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Survey of network coding-aware routing protocols in wireless networks
Abstract
In recent times, there have been many advances in the field of information theory and wireless ad hoc network technologies. Regarding information theory progression and its connection with wireless ad hoc networks, this study presents fundamental concepts related to the application of the state-of-the-art Network Coding (NC) within wireless ad hoc networks in the context of routing. To begin with, this paper briefly describes opportunistic routing and identifies differentiation between NC-aware and NC-based routing mechanisms in wireless ad hoc networks. However, our main focus is to provide a survey of available NC-aware routing protocols that make forwarding decisions based on the information of available coding opportunities across several routes within wireless ad hoc networks. The taxonomy and characteristics of various representative NC-aware routing protocols will also be discussed. In summary, we provide a comparison of available NC-aware routing schemes and conclude that NC-aware routing techniques have several advantages over traditional routing in terms of high throughput, high reliability, and lower delay in a wireless scenario. To the best of our knowledge, this work is the first that provides comprehensive discussion about NC-aware routing protocols.
... Due to the potentials of network coding in improving the performance of wireless multihop network, some network coding-based routings [13][14][15] have been proposed. The network coding applied in routings is network layer network coding, instead of physical layer network coding. ...
... The classic network coding routings put emphasis on the increasing of coding opportunities through improving the network coding conditions. [13][14][15] However, existing network coding conditions are only valid under certain conditions and may lead to failure decoding problem in certain scenarios. On the other hand, network coding opportunity at one node only means that network coding potentially take place at the node, but existing coding aware routings exploit opportunistic network coding scheduling (ONCS) for packets transmission scheduling, which cannot guarantee the occurrence of network coding. ...
... Perform XOR operation on the left and right sides of the equations (12) and (13), then there is ...
Network coding–based routing has been widely considered as a promising technology to improve the network throughput of wireless multihop network. However, existing network coding aware routings have the problem of failure decoding and usually neglect the transmission scheduling, which degrades the gain of network coding. In this article, a common network coding condition and traffic matching supported network coding aware routing is proposed for wireless multihop network. In this, common network coding condition is proposed to avoid the problem of failed decoding. In addition, traffic matching mechanism is presented to promote the occurrence of network coding. Besides, a coding and load aware routing metric, which jointly considers the network coding opportunity and node load, is designed to evaluate the discovered paths. Extensive simulations on NS2 demonstrate that CTNR increases the number of coding opportunities and network coding occurrence, and improves network throughput.
... In this paper, we are concerned with the inter-session NC implemented between the medium access control (MAC) and network layers of the protocol stack, focusing on potential benefits provided by its tight collaboration with routing procedure. If the latter aims to discover coding opportunities in the network and take them into account during route selection, we refer to it as NC-aware routing [5]. By creating additional coding opportunities, NC-aware routing further increases network throughput compared to NC-unaware routing. ...
... Therefore, the traffic intensity on those paths should also be considered to avoid network congestion. In wireless networks, high traffic does not only result in traffic congestion but also in the increased interference among the nodes located within each other's coverage area [5]. ...
... Subsequently, only the encoded packet is forwarded, as shown in Fig. 1(b), therefore, only three transmissions are used to deliver the packets. Several on-demand coding-aware routing procedures have been designed and presented in the literature in order to improve the NC benefits and further increase network throughput [5], considering various effects and limitations in wireless networks. For example, in [9] and [10], different metrics are proposed to balance between interference degradation and coding gain performance, i.e., to achieve a trade-off between routing multiple flows "close to each other" for more coding opportunities and routing multiple flows "away from each other" to reduce the interference. ...
Network Coding (NC) is an approach recently investigated for increasing the network throughput and thus enhancing the performance of wireless mesh networks. The benefits of NC can further be improved when routing decisions are made with the awareness of coding capabilities and opportunities. Typically, the goal of such routing is to find and exploit routes with new coding opportunities and thus further increase the network throughput. As shown in this paper, in case of proactive routing the coding awareness along with the information of the measured traffic coding success can also be efficiently used to support the congestion avoidance and enable more encoded packets, thus indirectly further increasing the network throughput. To this end, a new proactive routing procedure called Congestion-Avoidance Network Coding-Aware Routing (CANCAR) is proposed. It detects the currently most highly-loaded node and prevents it from saturation by diverting some of the least coded traffic flows to alternative routes, thus achieving even higher coding gain by the remaining well-coded traffic flows on the node. The simulation results confirm that the proposed proactive routing procedure combined with the well-known COPE NC avoids network congestion and provides higher coding gains, thus achieving significantly higher throughput and enabling higher traffic loads both in a representative regular network topology as well as in two synthetically generated random network topologies.
... In opportunistic routing, multiple neighbors can overhear a transmitting node and upon receiving a data packet, selected set of a sender's neighbor can continue the packet forwarding towards the destination while meeting the certain conditions [12] [13]. The contemporary opportunistic routing schemes can be categorized in various ways in terms of forwarder set selection and prioritization metric [14]. Regarding prioritization metric, Network Coding Based (NC-Based also known as Intra-flow) and Network Coding-Aware (NC-Aware also known as Inter-flow) approaches make forwarding decisions based on the available coding opportunities across several directions towards the destination node(s) within ad hoc networks [15]. ...
... In [14], the authors have recommended the taxonomy of NC-Aware routing approaches for ad hoc networks as shown in Fig. 4 Fig. 4. Taxonomy of NC-Aware routing protocols for ad hoc networks [14] Merits and demerits of the existing NC-Aware routing techniques with reference to their implications in VANETs are discussed below: ...
... In [14], the authors have recommended the taxonomy of NC-Aware routing approaches for ad hoc networks as shown in Fig. 4 Fig. 4. Taxonomy of NC-Aware routing protocols for ad hoc networks [14] Merits and demerits of the existing NC-Aware routing techniques with reference to their implications in VANETs are discussed below: ...
Information theory progression along with the advancements being made in the field of Vehicular Ad hoc NETworks (VANETs) supports the use of coding-aware opportunistic routing for efficient data forwarding. In this work, we propose and investigate an adaptive coding-aware routing scheme in a specific VANET scenario known as a vehicular platoon. Availability of coding opportunities may vary with time and therefore, the accurate identification of available coding opportunities at a specific time is a quite challenging task in the highly dynamic scenario of VANETs. In the proposed approach, while estimating the topology of the network at any time instance, a forwarding vehicle contemplates the composition of multiple unicast data flows to encode the correct data packets that can be decoded successfully at destinations. The results obtained by using OMNeT++ simulator reveal that higher throughput can be achieved with minimum possible packet transmissions through the proposed adaptive coding-aware routing approach. In addition, the proposed adaptive scheme outperforms static transmissions of the encoded packets in terms of coding gain, transmission percentage, and encoded packet transmission. To the best of our knowledge, the use of coding-aware opportunistic routing has not been exploited extensively in available literature with reference to its implications in VANETs.
... reduction in transmission delay, reduction in power consumption, and an increase in network robustness [3][4][5]. In general, network coding presents a better routing solution for any network that supports internode processing. ...
... In general, network coding presents a better routing solution for any network that supports internode processing. Due to the above reasons, applications for network coding have been found in areas of P2P communication [4,6,7], data gathering in sensor networks [7], and wireless networks [8][9][10][11][12][13]. ...
One of the major security threats that plague network coding are pollution attacks. Therefore, the ability to authenticate the contents of received packets is a vital requirement of all network coding authentication schemes. One of the most famous cryptographic approaches used to mitigate data and tag pollution in network coding are homomorphic message authentication codes (HMACS). In this approach, authentication is achieved by appending one or more HMAC tag vectors and in some cases a homomorphic cryptographic signature to the packet payload. Two major concerns arise when designing authentication schemes for network coding. These are the costs associated with the communication and computational overheads. These two factors determine the efficiency and practicality of the scheme. Unfortunately, in most cases, lowering one of the costs results in an increase in the other. In this paper we propose an efficient data and tag pollution immune authentication scheme based on HMACs and a homomorphic cryptographic signature. In our evaluation of the performance of the proposed scheme we compared it with three other similar state of the art schemes. The result of our evaluation showed that the proposed scheme incurs a computational overhead that is up to 64–97% lower at the source and non-source nodes. The proposed scheme also fairs well with respect to communication overhead where it is only outperformed by one of the three schemes. This difference however is minute (one symbol) and is greatly outweighed by the proposed schemes lower computational overhead.
... The Network Coding (NC) provides diversity by transmitting carefully designed mathematical combinations of multiple original packets instead. The mathematical combination can be implemented at the packet level [23] [24], and the symbol level [25]. Finally, the OR [26] takes advantage of the broadcasting nature of the wireless medium and makes all the overhearing nodes incrementally contribute to the forwarding process (node diversity). ...
... B loc (i) is not required in the definition of B opp (i) since we have considered its effect in eq. (24). Finally, the BCR metric is defined as the ratio of ETC to EAB. • Correlation-aware EAX (cEAX): Link correlation is caused by (i) cross-network interference under a shared medium and (ii) correlated fading introduced by highly dynamic environments. ...
High-speed, low latency, and heterogeneity features of 5G, as the common denominator of many emerging and classic wireless applications, have put wireless technology back in the spotlight. Continuous connectivity requirement in low-power and wide-reach networks underlines the need for more efficient routing over scarce wireless resources, in multi-hp scenarios. In this regard, Opportunistic Routing (OR), which utilizes the broadcast nature of wireless media to provide transmission cooperation amongst a selected number of overhearing nodes, has become more promising than ever. Crucial to the overall network performance, which nodes to participate and where they stand on the transmission-priority hierarchy, are decided by user-defined OR metrics embedded in OR protocols. Therefore, the task of choosing or designing an appropriate OR metric is a critical one. The numerousness, proprietary notations, and the objective variousness of OR metrics can cause the interested researcher to lose insight and become overwhelmed, making the metric selection or design effort-intensive. While there are not any comprehensive OR metrics surveys in the literature, those who partially address the subject are non-exhaustive and lacking in detail. Furthermore, they offer limited insight regarding related taxonomy and future research recommendations. In this paper, starting with a custom tutorial with a new look to OR and OR metrics, we devise a new framework for OR metric design. Introducing a new taxonomy enables us to take a structured, investigative, and comparative approach to OR metrics, supported by extensive simulations. Exhaustive coverage of OR metrics, formulated in a unified notation, is presented with sufficient details. Self-explanatory, easy-to-grasp, and visual-friendly quick references are provided, which can be used independently from the rest of the paper.
... In particular, we were focusing on potential benefits provided by its tight collaboration with the routing procedure, by finding a path where more coding opportunities exist, based on the information of existing traffic and network topology. We refer to it as NC-aware routing, as it aims to discover coding opportunities in the network and take them into account during route selection [6]. Such NC-aware routing further increases network throughput compared to NC-unaware routing by creating additional coding opportunities. ...
... Thus, the reduction of network load which is due to NC, enabled (in this case) by network-coding-aware routing, is 25% (i.e. 3 transmissions instead of 4). In order to improve the network coding benefits and further increase the network throughput, several on-demand coding-aware routing procedures have been designed and presented in the literature [6]. Different coding-aware routing approaches were designed and various effects and limitations in wireless networks have been considered. ...
Approaches for increasing the network throughput and thus enhancing the performance of wireless mesh networks are one of the key challenges. Network Coding (NC) offers a way to improve on the network performance, by sharing network resources. With the additional approaches, where routing decisions are made with the awareness of coding capabilities and opportunities, the performance of NC can be further improved. As shown in this paper, in the case of proposed proactive routing procedure CANCAR (Congestion-Avoidance Network Coding-Aware Routing), which takes into account the coding awareness along with the information of the measured traffic coding success, it can be efficiently used to support the congestion avoidance and enable more encoded packets, thus indirectly increasing the network throughput. Comprehensive evaluation of CANCAR in realistic simulation environments confirms that the performance in terms of network goodput is notably improved in comparison to COPE. In addition, we showed that the accurate use of measured coding success information for congestion-avoidance routing improves the network performance and has the potential to increase the number of encoded packets. Furthermore, the CANCAR also enables the fairer share of system resources according to the Jain’s fairness index.
... Tais protocolos também exigem que os quadros xor sejam decodificados na camada de enlace. Isso subotimiza o possível uso de técnicas de roteamento ciente de codificação (CAR -Coding-Aware Routing) [8]. Outra desvantagem do protocolo em [7]é que o esquema PNCé realizado dentro de uma só sessão, o que também prejudica o CAR pois com issó e inibido a possibilidade do pacote xor ser recodificado. ...
... Tais tarefas podem ser feitas mais facilmente pela camada de rede. Com isso, a principal desvantagem dessa abordagemé que técnicas de CAR [8], presentes na camada de rede, terão acesso apenas ao tipo de entrega convencional. Ao contrário, no esquema proposto no presente artigo tais técnicas terão flexibilidade e poderão optar também pelos tipos de entrega PNC e MC. ...
... Energy consumed in transmission mode P Transmission = Current required to transmit signals * Voltage*Time (1) Energy consumed in receiving mode P perceiving = Current required to receive signals * Voltage *Time (2) Energy consumed in idle mode P idle = Current required in Idle mode * Voltage * Time (3) Energy consumed in Sleep mode P sleep = Current required in Sleep mode *Voltage * Time (4) The units of power are mW, voltage is volts, time, current, battery life is mAh, and the charge is mA's.The total energy utilized is equal to the aggregation of energies in all modes. ...
... f) NC-mindful directing: The nodes are known as coding points that consider the NC-mindful convention in the system, that guide in choosing a way for forwarding the packets in the network [1] ...
A Node in MANETs bond with neighboring nodes that are existent inside the transmission range and contact them by means of wireless medium. Distinctive sorts of modes are Transmit, Receive, Idle and Sleep. Keeping up dynamic topology and states lead to outcomes, for example, utilization of more battery power, in this manner decreases the system lifetime. Accordingly, it is fundamental to advance power utilization for enhancing the continuance of the system. Many conventions have been proposed for effective routing of the data packets. Distinctive conventions can be teamed up with various energy models, for example, GENERIC, MICAZ, MICA-MOTES, and USER-DEFINED provided by QualNet, that also investigates the power utilization. These conventions are assessed to foregather the most dependable and productive convention. Examinations are finished with the fundamental emphasis to accomplish energy proficiency. Execution assessment is done dependent on measurements, such as, energy utilization, network lifetime, time to live, the measure of current used, cost of the battery, and so forth
... Since network coding can reduce transmission number and improve network throughput, some network coding based routings have been proposed [14][15][16]. According to the packets participating in coding from one flow or multiple flows, the network coding applied in routings can be divided into intra-flow network coding and inter-flow network coding [14]. ...
... Since network coding can reduce transmission number and improve network throughput, some network coding based routings have been proposed [14][15][16]. According to the packets participating in coding from one flow or multiple flows, the network coding applied in routings can be divided into intra-flow network coding and inter-flow network coding [14]. The aim of intra-flow network coding based routings are generally to improve the reliability of transmission by using random linear network coding. ...
Energy efficiency is a critical problem for wireless sensor networks. In past decades, network coding has been proved as a promising technology to reduce the number of transmissions, save energy and improve network throughput, especially suitable for the wireless network, which motivates the emergence of network coding aware routings. However, existing network coding aware routings have the failure decoding problem because of defective network coding conditions. On the other hand, existing network coding aware routings usually consider the ideal traffic scheduling and neglect nodes’ energy and load which are important to wireless sensor networks. Therefore, it is not appropriate to directly apply existing network coding aware routings in wireless sensor networks. Regarding the problems above, this paper proposes the traffic shaped network coding aware routing (TSCAR) for wireless sensor networks. In TSCAR, a universal network coding condition is presented to solve the false decoding problem. And traffic shaping mechanism is proposed to shape the traffic of different flows to create more coding actions when coding opportunities exist. In addition, network calculus is used to analyze the delay of TSCAR. Besides, a coding, load, and energy aware routing metric (CLERM) is proposed to evaluate the discovered paths. Extensive simulation results demonstrate that TSCAR increases the number of coding opportunities and the proportion of coded packets, improves network throughput, and extends the network lifetime of wireless sensor networks.
... In farmland, time-varying channels, unstable link conditions, and stringent energy constraint pose a challenge for efficient and stable data aggregation in WSN. However, researchers have proposed opportunistic routing (OR) to improve the transmission reliability and end to end throughput of WSN by using the inherent advantages of wireless channel broadcast [2] . This paper proposes an improved energy aware opportunistic routing of farmland WSN. ...
... Opportunistic routing (OR) was first proposed by Biswas of Massachusetts Institute of Technology (MIT) in 2004 [2] . OR algorithm improves the network throughput and reliability through multiple potential relay nodes competing and autonomous intelligent judgment, performs the next hop node selection, and takes full advantage of channel broadcast characteristic. ...
... Network coding (NC) is an emerging communication paradigm that has the potential to provide significant benefits to networks in terms of bandwidth, robustness to packet losses, delay and energy consumption [1][2][3]. The main idea of network coding (NC) was introduced for the first time by Ahlswede et al. in [4]. ...
... In terms of exponentiations, we have considered that each exponentiation is equivalent to 3 2 | p| multiplications as it is shown in [16]. Figure 5 represents the number of multiplications which are required for verification of a packet at each non-source node for three different numbers of compromised nodes (i.e., c = 1, 2 and 3). ...
Recent research efforts have shown that wireless networks can benefit from network coding (NC) technology in terms of bandwidth, robustness to packet losses, delay and energy consumption. However, NC-enabled wireless networks are susceptible to a severe security threat, known as data pollution attack, where a malicious node injects into the network polluted packets that prevent the destination nodes from decoding correctly. Due to recoding, occurred at the intermediate nodes, according to the core principle of NC, the polluted packets propagate quickly into other packets and corrupt bunches of legitimate packets leading to network resource waste. Hence, a lot of research effort has been devoted to schemes against data pollution attacks. Homomorphic MAC-based schemes are a promising solution against data pollution attacks. However, most of them are susceptible to a new type of pollution attack, called tag pollution attack, where an adversary node randomly modifies tags appended to the end of the transmitted packets. Therefore, in this paper, we propose an efficient homomorphic message authentication code-based scheme, called HMAC, providing resistance against data pollution attacks and tag pollution attacks in NC-enabled wireless networks. Our proposed scheme makes use of three types of homomorphic tags (i.e., MACs, D-MACs and one signature) which are appended to the end of the coded packet. Our results show that the proposed HMAC scheme is more efficient compared to other competitive tag pollution immune schemes in terms of complexity, communication overhead and key storage overhead.
... Currently, there are some works on surveying network coding [10][11][12][13], but none of them is specifically on XNC for unicast traffic in WMNs. Thus, due to the usefulness of XNC in WMNs and those identified design factors, we are motivated to give a survey on this topic in this paper. ...
... This rate region problem can be formulated as a simple linear program [51], of which the details are omitted here. Fig. 15(b) and (c) show the regions of (R 0 , R 2 ) under the two schemes when C 12 = C 10 . From the figures, we can find that when C 12 > C 10 , it is not possible for XNC to support a (R 0 , R 2 ) tuple with R 0 > 1/(1/C 01 + 1/C 21 ), and that when C 12 < C 10 , it is not possible for XNC to support a (R 0 , R 2 ) tuple with R 2 > 1/(1/C 12 + 1/C 21 ). ...
... However, as part of the routing metric to find the next-hop, it takes into account the number of available coding opportunities at each node. Details on NC-aware routing protocols can be found in [21]. ...
Network coding and opportunistic routing are two recognized innovative ideas to improve the performance of wireless networks by utilizing the broadcast nature of the wireless medium. In the last decade, there has been considerable research on how to synergize inter-flow network coding and opportunistic routing in a single joint protocol outperforming each in any scenario. This paper explains the motivation behind the integration of these two techniques, and highlights certain scenarios in which the joint approach may even degrade the performance, emphasizing the fact that their synergistic effect cannot be accomplished with a naive and perfunctory combination. This survey paper also provides a comprehensive taxonomy of the joint protocols in terms of their fundamental components and associated challenges, and compares existing joint protocols. We also present concluding remarks along with an outline of future research directions.
... A variety of improvements over COPE have been put forward, especially by adding opportunistic forwarding [9]. In CORMEN [10], as a network coding scheme enhanced with opportunistic routing, the nodes in the forwarder set are neighbors of the nodes in the shortest path to avoid diverging the path and unnecessary duplicate packets. ...
In recent years, network coding has emerged as an innovative method that helps a wireless network approach its maximum capacity, by combining multiple unicasts in one broadcast. However, the majority of research conducted in this area is yet to fully utilize the broadcasting nature of wireless networks, and still assumes fixed route between the source and destination that every packet should travel through. This assumption not only limits coding opportunities, but can also cause buffer overflow in some specific intermediate nodes. Although some studies considered scattering of the flows dynamically in the network, they still face some limitations. This paper explains pros and cons of some prominent research in network coding and proposes a Flexible and Opportunistic Network Coding scheme (FlexONC) as a solution to such issues. Furthermore, this research discovers that the conditions used in previous studies to combine packets of different flows are overly optimistic and would affect the network performance adversarially. Therefore, we provide a more accurate set of rules for packet encoding. The experimental results show that FlexONC outperforms previous methods especially in networks with high bit error rate, by better utilizing redundant packets spread in the network.
... NC is foreseen as a promising solution for the wireless network of MSCs to increase its throughput and improve its performance. In fact, NC is an emerging communication paradigm that has the potential to provide significant benefits to networks in terms of bandwidth, energy consumption, delay and robustness to packet losses [19][20][21]. The main idea of NC was introduced for the first time by Ahlswede et al. [22]. ...
This thesis investigates decentralized key management and presents two novel decentralized key management schemes that are capable of providing secure communication in ad hoc-type networks and are agnostic to the network coding technology. The main research contributions of this thesis are summarized as follows:
We investigate the inherent security and privacy challenges of the scenario architecture and identify the necessity for a decentralized key management solution. We examine nine legacy decentralized key management solutions and evaluate their suitability based on their abilities to satisfy seven proposed requirements. Our evaluation identifies that the fully distributed TTP (FD-TTP)-based key management solution has the greatest potential. This solution takes advantage of secret sharing techniques to establish a distributed TTP such that a threshold number of network users can collaboratively provide key management services. An appropriate adversarial model is defined to evaluate the security level of FD-TTP-based key management schemes.
We present the design of our novel decentralized key management scheme, entitled DISTANT. This decentralized key management scheme follows the conventional structure of FD-TTP-based key management schemes and aims to improve the level of security compared to previously proposed FD-TTP-based key management schemes. Our scheme utilizes the self-generated certificates paradigm for its abilities to (i) guarantee network subscribers with end-to-end security and (ii) limit communication overheads due to non-interactive certificate updating and a redundant certificate revocation procedure. In comparison to closely related schemes, DISTANT reaches the highest level of security while remaining competitive in terms of communication overhead.
We also present the design of our novel decentralized key management scheme, entitled DECENT. This decentralized key management scheme deviates from the conventional structure of FD-TTP-based key management schemes through the utilization of threshold-tolerant identity-based public key cryptography where secret shares are directly used as private keys. This equivalence between shares and keys allows the key management design to benefit from (i) the self-healing property (i.e., the network can independently recover from compromise), and (ii) the merger of share- and key-related protocols which provide significant reductions in terms of communication overhead. In comparison to closely related schemes, DECENT has the lowest communication overhead requirement while remaining competitive in terms of security.
... Network coding enables the router to broadcast a mixture of information packets. Due to its potential to provide energyefficient and high throughput performance, network coding has found a wider acceptance in the academia and industry (Fragouli et al., 2006;Iqbal et al., 2011;Magli et al., 2013). For a HD hexagonal wireless backhaul network where the MBS transmits a linear combination of the messages to a set of SBSs, the per user degrees of freedom was shown to be approaching 1/2 in (Bande and Veeravalli, 2020). ...
Benefiting from the usage of the high-frequency band, utilizing part of the large available bandwidth for wireless backhauling is feasible without considerable performance sacrifice. In this context, integrated access and backhaul (IAB) has been proposed by the Third Generation Partnership Project (3GPP) to reduce the expenses related to the deployment of fiber optics for 5G and beyond networks. In this paper, first, a brief introduction of IAB based on the 3GPP release is presented. Then, the existing research on IAB networks based on 3GPP specifications and possible non-3GPP research extensions are surveyed. The research on non-3GPP extensions includes the integration of IAB networks with other advanced techniques beyond the currently defined protocol stacks, such as the integration of IAB to cache-enabled, optical communication transport, and non-terrestrial networks. Finally, the challenges and opportunities related to the development and commercialization of the IAB networks are discussed.
... It allows that flows are encoded into an encoded flow in their intersecting node as long as their destination nodes can retrieve them from the encoded flow separately. To take the advantages of network coding, network coding-aware routing has been proposed in wireless networks [4]. XOR coding is one of the simplest but effective interflow network coding schemes and thus widely used in the existing network coding-aware routing methods [5][6][7]. ...
Network coding-aware routing has become an effective paradigm to improve network throughput and relieve network congestion. However, to detect coding opportunities and make routing decision for a data flow, most existing XOR coding-aware routing methods need to consume much overhead to collect overhearing information on its possible routing paths. In view of this, we propose low-overhead and dynamic Coding-Aware Routing via Tree-based Address (CARTA) for wireless sensor networks (WSNs). In CARTA, a Multi-Root Multi-Tree Topology (MRMTT) with a tree-based address allocation mechanism is firstly constructed to provide transmission paths for data flows. Then, a low-overhead coding condition judgment method is provided to detect real-time coding opportunities via tree address calculation in the MRMTT. Further, CARTA defines routing address adjustments caused by encoding and decoding to ensure the flows’ routing paths can be adjusted flexibly according to their real-time coding opportunities. It also makes additional constraints on congestion and hop count in the coding condition judgment to relieve network congestion and control the hop counts of routing paths. The simulation results verify that CARTA can utilize more coding opportunities with less overhead on coding, and this is ultimately beneficial for promoting network throughout and balancing energy consumption in WSNs.
... The concept of network coding was first introduced in [11]. It is an emerging communication paradigm that has the potential to provide significant benefits to networks in terms of bandwidth, energy consumption, delay and robustness to packet losses [12,13,14]. ...
The continuous growth in wireless devices connected to the Internet and the increasing demand for higher data rates put ever increasing pressure on the 4G cellular network. The EU funded H2020-MSCA project “SECRET” investigates a scenario architecture to cover the urban landscape for the upcoming 5G cellular network. The studied scenario architecture combines multi-hop device-to-device (D2D) communication with network coding-enabled mobile small cells. In this scenario architecture, mobile nodes benefit from high transmission speeds, low latency and increased energy efficiency, while the cellular network benefits from a reduced workload of its base stations. However, this scenario architecture faces various security and privacy challenges. These challenges can be addressed using cryptographic techniques and protocols, assuming that a key management scheme is able to provide mobile nodes with secret keys in a secure manner. Unfortunately, existing key management schemes are unable to cover all security and privacy challenges of the studied scenario architecture. Certificateless key management schemes seem promising, although many proposed schemes of this category of key management schemes require a secure channel or lack key update and key revocation procedures. We therefore suggest further research in key management schemes which include secret key sharing among mobile nodes, key revocation, key update and mobile node authentication to fit with our scenario architecture.
Keywords5GSecurityPrivacyKey managementMobile small cellsNetwork codingD2D communications
... Due to the advantages of network coding in reducing data transmission and improving throughput, some network coding-based routings for wireless multi-hop network have emerged [13][14][15]. The network coding exploited in wireless multi-hop network routing can be divided into two categories: inter-flow network coding and intra-flow network coding according to the packets participating in network coding belongs to single flow or multiple flow [9]. ...
Wireless sensor nodes in wireless sensor networks are generally battery powered and it is usually hard to change their batteries. Therefore, energy saving has always been the basic critical problem of wireless sensor networks. In recent years, network coding has become a promising technology to improve network throughput, reduce transmission number, and save energy, which has great potential to solve the energy efficiency problem of wireless sensor networks. In addition, some network coding aware routings have been proposed. However, the network coding condition of existing network coding aware routings may experience the problem of false-coding effect in some scenarios, and usually neglect node energy, which greatly influences the energy efficiency performance. Therefore, existing network coding aware routings are not suitable for wireless sensor networks. This paper proposes network coding aware energy efficient routing (NAER) for wireless sensor networks. In NAER, universal network coding condition is presented and proved to avoid false-coding problem. Besides, combined with the coverage control and topology control mechanism at lower layer, cross layer coding opportunity discover mechanism is presented to increase coding opportunities. In addition, a network coding aware energy efficient routing metric (NERM) is presented, which takes coding opportunity, node energy, and link quality into account jointly. Simulation results demonstrate that NAER improves the accuracy of coding discovery mechanism, increases the number of coding opportunities, saves node’s energy consumption, and prolongs network lifetime.
... However, as part of the routing metric to find the next-hop, it takes into account the number of available coding opportunities at each node. Details on NCaware routing protocols can be found in [21]. ...
Network coding and opportunistic routing are two recognized innovative ideas to improve the performance of wireless networks by utilizing the broadcast nature of the wireless medium. In the last decade, there has been considerable research on how to synergize inter-flow network coding and opportunistic routing in a single joint protocol outperforming each in any scenario. This paper explains the motivation behind the integration of these two techniques, and highlights certain scenarios in which the joint approach may even degrade the performance, emphasizing the fact that their synergistic effect cannot be accomplished with a naive and perfunctory combination. This survey paper also provides a comprehensive taxonomy of the joint protocols in terms of their fundamental components and associated challenges, and compares existing joint protocols. We also present concluding remarks along with an outline of future research directions.
... A variety of improvements over COPE have been put forward [11]. BEND, as an advancement of COPE, introduces another type of gain, referred to as the diffusion gain, which is the benefit of being able to scatter flows through multiple forwarders dynamically. ...
In recent years, network coding has emerged as an innovative method that helps wireless network approaches its maximum capacity, by combining multiple unicasts in one broadcast. However, the majority of research conducted in this area is yet to fully utilize the broadcasting nature of wireless networks, and still assumes fixed route between the source and destination that every packet should travel through. This assumption not only limits coding opportunities, but can also cause buffer overflow in some specific intermediate nodes. Although some studies considered scattering of the flows dynamically in the network, they still face some limitations. This paper explains pros and cons of some prominent research in network coding and proposes FlexONC (Flexible and Opportunistic Network Coding) as a solution to such issues. The performance results show that FlexONC outperforms previous methods especially in worse quality networks, by better utilizing redundant packets spread in the network.
... The various network coding schemes are discussed in [18,19]. Muhammad Azhar Iqbal et al. [20] compared different routing protocols and how it differed from routing schemes based on network cod-ing. Network coding occurs at the intermediate node for both unicast and multicast networks [21]. ...
The broadband wireless network provides an efficient solution for both data reliability and network congestion to meet the demand of the increasing number of mobile users. However, due to dense deployment of nodes, interference and data dissemination problems occur which result in unreliable packet delivery during data transmission in smart cities. All this creates problem in efficient data transmission. In order to solve this problem, in this work, we propose a novel Code-Encoding and Decoding (C-ED) mechanism for IEEE 802.16 networks that helps to mitigate the problem of data dissemination by using minimal number of channels. The proposed C-ED mechanism provides a reliable packet delivery during multicast transmission. As the smart cities are connected with complex networks, our scheme utilizes the existing channel assignment strategies to assign a minimal number of channels to the network and transmit the data using the proposed C-ED mechanism. To illustrate the effectiveness of the proposed C-ED mechanism, it is evaluated by combining it with the existing channel assignment strategies i.e., clique partitioning and random. The simulation results show that the C-ED mechanism with clique partitioning provides improved quality of service than random channel assignment. The C-ED mechanism is compared with Luby Transform (LT) codes which result in reduced transmission delay and improved throughput for a complex network.
... There are several survey papers which exclusively discuss network coding. Network coding-aware routing protocols for wireless ad-hoc networks are discussed in [48], while a survey on network coding-based wireless relay networks is presented in [49]. Bassoli et al. [50] presented a survey of all known fields of network coding. ...
Network Coding (NC) is a technique used for effective and secure communication by improving the network capacity, throughput, efficiency, and robustness. In network coding, data packets are encoded by intermediate nodes and are then decoded at the destination nodes. Network coding has been successfully applied in a variety of networks including relay networks, peer-to-peer networks, wireless networks, cognitive radio networks, and wireless sensor networks. Cognitive radio network (CRN) is an emerging field which exploits the utilization of unused spectrum or white spaces, effectively and efficiently. In CRNs, network coding schemes are also applied to maximize the spectrum utilization, as well as to maintain the effective and secure transmission of data packets over the network. In this paper, we provide a comprehensive survey of network coding schemes in cognitive radio networks, highlighting the motivations for and the applications of network coding in CRNs. We provide typical case studies of network coding schemes in CRNs, as well as the taxonomy of network coding schemes in CRNs. Finally, we present open issues, challenges, and future research directions related with network coding in cognitive radio networks.
... A variety of improvements over COPE have been put forward, especially by adding opportunistic forwarding [9]. In CORMEN [10], as a network coding scheme enhanced with opportunistic routing, the nodes in the forwarder set are neighbors of the nodes in the shortest path to avoid diverging the path and unnecessary duplicate packets. ...
... Routing-path selection, traffic-load balancing, and network coding decisions are the three main issues tackled in the development of opportunistic network coding schemes [3]. Traffic flows need to be routed through the network in order to provide as many coding possibilities as possible [21][22][23][24][25][26]. Coding opportunities are more likely to appear on fully loaded nodes. ...
This paper proposes a Bearing Opportunistic Network (BON) coding procedure that operates in wireless multihop networks over multiple unicast sessions and it introduces very low overhead to the network. The BON coding is used to increase network performance in terms of a higher throughput and a lower delay. It can be seen as an independent layer in the communication stack, relying solely on information that is on the node itself. The proposed coding procedure is easy to implement and deploy. The performance evaluation of the BON coding procedure was performed in a dedicated simulation model. The comparison was made to the well-known network coding procedure COPE and the case where network coding is not used at all. Results show that BON coding increases the network goodput and decreases the delay in comparison to COPE and case where network coding is not used.
... A variety of improvements over COPE have been put forward [11]. BEND, as an advancement of COPE, introduces another type of gain, referred to as the diffusion gain, which is the benefit of being able to scatter flows through multiple forwarders dynamically. ...
... Therefore we present a general structure to draw insight into all possible attacks that may be launched at different phases of NC based routing. Based on how packets are selected for coding, existing NC based wireless routings can be classified into intra-flow and inter-flow NC based routings [9]. For intra-flow NC based routing, intermediate nodes only mix packets with the same source and destination. ...
... Therefore we present a general structure to draw insight into all possible attacks that may be launched at different phases of NC based routing. Based on how packets are selected for coding, existing NC based wireless routings can be classified into intra-flow and inter-flow NC based routings [9]. For intra-flow NC based routing, intermediate nodes only mix packets with the same source and destination. ...
... Being aware of Applicable NC scenarios and opportunistic coding among different flows at certain amount of time provides the opportunity to improve the throughput of networks. Thus in order to Improve performance of existing protocols it is important to improve a NC-Aware routing to support active XOR coding between various data flows [3]. ...
... Network coding can be classified into two categories: intra-flow network coding and inter-flow network coding [9]. The former encodes the packets belonging to the same flow, such as Random Linear Network Coding (RLNC); and the latter mixes packets from different flows, such as opportunistic network coding (ONC) [4]. ...
In opportunistic networks (OppNets), instead of assuming a complete path, messages are exchanged opportunistically when two nodes encounter. To support efficient and reliable end-to-end messaging in OppNets, a number of routing protocols based on network coding have been proposed. However, few efforts in the studies focus on opportunistic network coding (ONC). It is because the coding opportunities do not probably exist in OppNets due to nodal mobility, low density, lossy link, etc. In this paper, an ONC routing model for OppNets based on a new hybrid communication scheme was proposed. The communication scheme combines contact-based communication mode used by most routing protocols in OppNets and contact duration-based communication mode employed by few routing protocols in OppNets. We also designed an ONC routing protocol based on the ONC routing model in OppNets. Simulated results show that compared with Epidemic routing, the ONC routing can achieve higher delivery ratio and lower delay but consume fewer network cost.
... Network coding technique was originally proposed by Ahlswede et al. [10], as a paradigm whereby the contents of the outgoing packets are arbitrary casual functions of the contents of the received packets. Since its introduction, several papers have built upon their work [11], [12]. But, these papers have based their analysis on computational methods. ...
This paper considers an existing computational method for minimum energy multicast in ad hoc wireless networks and proposes an empirical model that is based on Data Envelopment Analysis (DEA) methodology. The new model using input orientation with constant returns to scale (CRS) assumption is derived based on Economics concept of production function. The new approach provides alternative means of evaluating system performance with multiple inputs and outputs. This type of evaluation using empirical DEA method to study a program provides adequate technical efficiency measurement compared to the effectiveness performance measurement using a computational method. It is found that the proposed model is able to further minimize the transmission energy by the ad hoc wireless networks without altered the output.
... Network coding, first presented in Ref. [3], could reduce the number of transmissions, improve network throughput significantly, and save bandwidth consumption [4,5] . The excellent quality of network coding motivates the advances of network coding based routing for WMNs [6] . ...
The growth of network coding opportunities is considered the unique optimization goal by most current network coding based routing algorithms for wireless mesh networks. This usually results in flows aggregation problem in areas with coding opportunities, and degrades the network performance. This paper proposes a Load balanced coding aware multipath routing (LCMR) for wireless mesh networks. To facilitate the evaluation of discovered multiple paths and the tradeoffs between coding opportunity and load balancing, a novel routing metric, Load balanced coding aware routing metric (LCRM) is presented, which considers the load degree of nodes when detects coding opportunities. LCMR could spread traffic over multipath to further balance load. Simulation results demonstrate that LCMR could evenly spread the traffic over the network with increasing network throughput in a heavy load at the expense of some coding opportunities.
Network coding (NC) authentication schemes based on homomorphic message authentication codes (HMACs) are usually preferred due to the low computational complexity associated with their implementation. A basic requirement of these schemes is that they should be able to resist both message and tag pollution attacks. A common approach adopted in the design of these schemes uses key vectors to generate tags that are then used to detect these attacks. Conventionally, the only constraint placed on existing key selection models is that key elements must be chosen from a predefined finite cyclic field. In this work we prove that this condition alone is not sufficient to ensure total resistance to pollution attacks. We also provide a detailed description of this security loophole as well as a proposition that defines what a scheme needs in order to achieve total resistance to pollution attacks. Based on our findings we propose a modified authentication scheme for NC that is not exposed to the security loophole and therefore provides complete resistance to pollution attacks. Our evaluation of the proposed scheme against similar state of the art schemes shows that it achieves this at no extra overhead. As a matter of fact, the proposed scheme incurs a slightly lower computational overhead at non-source nodes coupled with a slightly lower key storage overhead.KeywordsNetwork codingComplete resistance to pollution attacksKey selection modelHMAC-based authentication
With wireless communication, resource efficiency is an important issue. Routing protocols has considered to be a successful technology in recent years, reducing transmission numbers, saving energy and improving network efficiency, especially appropriate for Wireless Networks that drive network coding expertise. However, current network coding knowing routing issues with failed network coding due to faulty conditions. Established network coding, on the other hand, typically takes into account the ideal traffic planning schedule and overlooked resource and load checkpoints that are critical for wireless communication. Therefore, current network coding in the information of routings on wireless sensor networks cannot be implemented explicitly. With regard to the problems mentioned above, this paper proposes the TSCAR for wireless sensor systems for routing in the context of a traffic system. A standard network coding criterion is set out in TSCAR to overcome the fake sequencing problem. In order to produce further coding behaviour as coding openings occur, a method for influencing the transport of various flows is also suggested. Furthermore, the TSCAR delay is analysed by the network calculus. In order to quantify the tracks found, a codification, load, also energy-aware metrics are also planned. Extensive simulation findings show that the TSCAR improves the amount of coding possibilities in addition the percentage of coded packages, boosts system efficiency, then extends wireless network sensor network life.
Authentication schemes based on homomorphic message authentication codes (HMACs) with or without a homomorphic cryptographic signature (HCS) have always played a vital role in network coding (NC). A newly developing trend with respect to research in this area takes authentication in NC-compatible networks beyond error detection. Current HMAC-based authentication schemes for networks that support NC not only detect and drop corrupted packets but also identify the rogue nodes that begun the attack. However, in order to completely optimize the performance of an NC-enabled network, nodes that identify corrupted packets should also be able to correct the errors. Doing this eliminates the communication cost associated with the need for re-transmission and improves throughput. In this paper we propose what to the best of our knowledge is the first of such HMAC-based authentication schemes. Like all current state of the art HMAC-based authentication schemes, the proposed scheme is able to identify pollution attacks and the nodes that launched them. Furthermore, the proposed scheme is also able to correct the corruption. This according to our evaluation improves the throughput of the network when compared to other similar state of the art schemes that do not possess this feature.
Benefiting from the usage of the high-frequency band, utilizing part of the large available bandwidth for wireless backhauling is feasible without considerable performance sacrifice. In this context, integrated access and backhaul (IAB) was proposed by 3GPP to reduce the fiber optics deployment cost of 5G and beyond networks. In this paper, we first give a brief introduction of IAB based on the 3GPP release. After that, we survey existing research on IAB networks, the integrations of IAB to cache-enabled network, optical communication transport network, and the non-terrestrial network. Finally, we discuss the challenges and opportunities that might arise while developing and commercializing IAB networks.
Pollution attacks in network coding result in the waste of bandwidth and computational resources. Several homomorphic message authentication code (HMAC) and signature-based schemes have been proposed to mitigate such attacks. In these schemes, authentication is achieved by appending several HMAC tags with or without a signature to the packet payload. This approach negatively affects the throughput as well as the communication overhead incurred by such schemes. A phenomenon determined by a property we dubbed as the admissible payload rate (APR). In this paper we propose an HMAC and signature-based authentication scheme that addresses the afore mentioned problems. It achieves this by reducing the number of symbols needed to represent a packet. We evaluated the performance of our scheme and compared our findings to the performance of similar, state of the art authentication schemes. Our comparisons revealed that the proposed scheme incurred a negligible percentage gain in computational complexity. However, with no extra key storage overhead, and without sacrificing security, our scheme achieved a significant percentage reduction in communication overhead. The above mentioned favorable characteristics make our scheme an ideal and practical authentication solution for networks where bandwidth is a constraint or an optimal throughput is a requirement.
For a future scenario where everything is connected, cognitive technology can be used for spectrum sensing and access, and emerging coding technologies can be used to address the erasure of packets caused by dynamic spectrum access and realize cognitive spectrum collaboration among users in mass connection scenarios. Machine learning technologies are being increasingly used in the implementation of smart networks. In this paper, after an overview of several key technologies in the cognitive spectrum collaboration, a joint optimization algorithm of dynamic spectrum access and coding is proposed and implemented using reinforcement learning, and the effectiveness of the algorithm is verified by simulations, thus providing a feasible research direction for the realization of cognitive spectrum collaboration.
High-speed, low latency, and heterogeneity features of 5G, as the common denominator of many emerging and classic wireless applications, have put wireless technology back in the spotlight. Continuous connectivity requirement in low-power and wide-reach networks underlines the need for more efficient routing over scarce wireless resources, in multi-hp scenarios. In this regard, Opportunistic Routing (OR), which utilizes the broadcast nature of wireless media to provide transmission cooperation amongst a selected number of overhearing nodes, has become more promising than ever. Crucial to the overall network performance, which nodes to participate and where they stand on the transmission-priority hierarchy, are decided by user-defined OR metrics embedded in OR protocols. Therefore, the task of choosing or designing an appropriate OR metric is a critical one. The numerousness, proprietary notations, and the objective variousness of OR metrics can cause the interested researcher to lose insight and become overwhelmed, making the metric selection or design effort-intensive. While there are not any comprehensive OR metrics surveys in the literature, those who partially address the subject are non-exhaustive and lacking in detail. Furthermore, they offer limited insight regarding related taxonomy and future research recommendations. In this paper, starting with a custom tutorial with a new look to OR and OR metrics, we devise a new framework for OR metric design. Introducing a new taxonomy enables us to take a structured, investigative, and comparative approach to OR metrics, supported by extensive simulations. Exhaustive coverage of OR metrics, formulated in a unified notation, is presented with sufficient details. Self-explanatory, easy-to-grasp, and visual-friendly quick references are provided, which can be used independently from the rest of the paper. Finally, a new insightful framework for future research directions is developed. This tutorial-survey has been organized to benefit both generalists and OR specialists equally, and to be used not only in its entirety but selectively as well.
In recent years, device-to-device (D2D) communication has attained significant attention in the research community. The advantages of D2D communication can be fully realized in multi-hop communication scenario. The integration of cellular and multi-hop networks not only provides guaranteed Quality of Service (QoS) and reliability as a traditional cellular network, but also has the flexibility and adaptability as a multi-hop network. Routing in such multi-hop cellular D2D networks is a critical issue, since the multi-hop network can perform worse than a traditional cellular network if wrong routing decisions are made. This is because routing in these multi-hop networks needs to take care of the node mobility, dynamic network topology, and network fragmentation, which did not exist in traditional cellular networking. This paper provides a comprehensive survey of routing in multi-hop D2D networks. Some future research directions for the routing in D2D networks are also discussed at the end of this paper.
LTE-Advanced heterogeneous networks enable a uniform broadband experience to users flexibly anywhere in the network by using a mix of large and small cells — i.e., macro, pico, femto and relay stations. In this paper, we propose a novel network coding-based for mobile content uploading, where multiple user equipments upload their own content toward the eNodeB in LTE-Advanced relay networks. Network coding has been considered as a promising solution in next generation networks because of the significant improvement in the transmission rate and reliability. The network coding enables an intermediate node having the capability of encoding incoming packets rather than simply forwarding. However, the advantages come at the cost of high computational, storage costs and coding vector overhead. The two former drawbacks can be solved easily by the fast development of current smart users and relay with high capability on computation and storage. The last issue of coding vector overhead still remains as many packets are encoded together using a linear combination since each packet needs to carry a large size of the header to store the information of the coding vector. We propose random overlapped chunked code for enhancing the transmission rate and reliability under the constraint of coding vector overhead. Furthermore, the encoding and decoding processes can be operated with low complexity. The complete transmission consists of two phases: users upload the content to the relay; the relay performs the proposed random overlapped chunked code of different coming streams from users and forwards the network-coded packets to the eNodeB. For performance evaluation, we run various simulations along with analysis to show that our proposal outperforms current schemes in terms of decoding probability.
This paper considers an existing computational method for minimum energy multicast in ad hoc wireless networks and proposes an empirical model that is based on Data Envelopment Analysis (DEA) methodology. The new model using input orientation with constant returns to scale (CRS) assumption is derived based on Economics concept of production function. The new approach provides alternative means of evaluating system performance with multiple inputs and outputs. This type of evaluation using empirical DEA method to study a program provides adequate technical efficiency measurement compared to the effectiveness performance measurement using a computational method. It is found that the proposed model is able to further minimize the transmission energy by the ad hoc wireless networks without altered the output.
Physical Layer Network coding (PLNC) can significantly improve network performance, but some security issues arise due to the limited information available to the forwarders. This paper analyses authentication in networks with PLNC and show theoretical and practical security limits. In particular, we obtain a lower bound for the probability of an attacker being able to insert a false message such that the message is believed to come from a legitimate source. We prove that an information-theoretic bound similar to the one for point-to-point communication systems can be achieved in networks employing PLNC. Necessary and sufficient conditions to achieve the bound are identified. Finally, a simple but important modification of a previous scheme is proposed to achieve the obtained bound.
This paper presents an Mobile Agent based Coding Aware Routing (MA-CAMR) for wireless sensor network, which exploits mobile agent to discovery the routing and coding opportunities, reducing complexity of node design. Besides, the general network coding condition of two cross flows is proposed for coding opportunity discovery. In addition, a novel routing metric, Coding and Energy Aware Routing Metric (CEARM) is proposed, which considers the coding gain, the load and energy of node. MA-CAMR exploits multipath routing and CEARM to balance the network load and energy consumption. Simulation results demonstrate that MA-CAMR could balance network load and energy consumption, reduce energy consumption, and prolong network lifetime.
In this paper, we address the issue of maximizing the lifetime of a static wireless ad-hoc network wherein the nodes are battery powered and have limited energy. In such scenarios, routing the traffic along shortest paths will lead to over-use of some nodes leading to premature network partition and an eventual end of communication. Network Coding is a promising technique that has been used, of late, by researchers for throughput improvement. We propose an algorithm that exploits network coding to route a set of unicast traffic demands, the objective being network lifetime maximization. The routing algorithm uses a link metric that takes care of the communication power consumption, the residual energy at the nodes and also the potential coding opportunities available at the node. Simulation results show that this algorithm enhances the network lifetime compared to the existing algorithms that do not employ network coding.
This paper proposes a network coding aware QoS (quality of service) routing (NCQR) for wireless sensor network, which exploits network coding technology to improve the QoS routing of wireless sensor network. Network coding condition with QoS constraint is proposed, which provides proof for coding opportunity detection. To facilitate the evaluation of discovered routes, a novel routing metric, called CQRM (coding aware QoS routing metric), is presented, which jointly considers link quality, node congestion and coding opportunity. Simulation results demonstrate that NCQR decreases the blocking ratio of QoS requests significantly and prolongs network lifetime.
Wireless ad hoc networks usually have lower network throughput than wireless infrastructure networks due to the inherent nature of multi-hop communication on a shared channel in wireless ad hoc networks. Network coding is a method that can improve the network throughput by reducing the amount of workload in the network while still ensuring that all user data is transferred. With network coding, a node can improve its transmission efficiency by combining (encoding) several packets together and sending only the resultant encoded packet if the coding conditions are satisfied. In this paper, we propose the Network Coding Routing (NCRT) protocol which consists of a new set of coding conditions, and a new routing metric that takes into consideration both coding opportunities and network workload. Comprehensive simulation studies showed that NCRT gives promising performance.
Network coding is a novel technique introduced to improve the throughput of the network. It is used in many areas such as internet, file download, wireless mesh networks, sensor networks. The main benefits of network coding are increasing the throughput reducing the delay, enhance robustness and adaptability. In this paper we discuss the concept of network coding, how it does, its areas of use and benefits. We also evaluate the gain obtained in different topologies using network coding, with different offered loads.
Network coding promises to significantly impact the way communications networks are designed, operated, and understood. The first book to present a unified and intuitive overview of the theory, applications, challenges, and future directions of this emerging field, this is a must-have resource for those working in wireline or wireless networking. *Uses an engineering approach – explains the ideas and practical techniques *Covers mathematical underpinnings, practical algorithms, code selection, security, and network management *Discusses key topics of inter-session (non-multicast) network coding, lossy networks, lossless networks, and subgraph-selection algorithms Starting with basic concepts, models, and theory, then covering a core subset of results with full proofs, Ho and Lun provide an authoritative introduction to network coding that supplies both the background to support research and the practical considerations for designing coded networks. This is an essential resource for graduate students and researchers in electronic and computer engineering and for practitioners in the communications industry.
The Quantize and Forward cooperative communication protocol improves the reliability of data transmission by allowing a relay to forward to the destination a quantized version of the signal received from the source. In prior studies of the Quantize and Forward protocol, all channel parameters are assumed to be perfectly known at the destination, while in reality these need to be estimated. This paper proposes a novel Quantize and Forward protocol in which the relay compensates for the rotation on the source-relay channel using a crude channel estimate, before quantizing the phase of the received M-PSK data symbols. Therefore, as far as the source-relay channel is concerned, only an SNR estimate is needed at the destination. Further, the destination applies the EM algorithm to improve the estimates of the source-destination and relay-destination channels. The resulting performance is shown to be close to that of a system with known channel parameters.
In this paper, we propose network coding, as an efficient and low cost option for the implementation of block-Markov coding for cooperative communications. Cooperative communications is a strategy where users, besides transmitting their own encoded information, also relay re-encoded versions of other users' information to a common destination. Our work is motivated by the recent information-theoretic results on user cooperation. These results show that cooperating users in a multiple access channel can improve on the classical multiple access channel capacity region under the same average trans-mit power constraint. Additionally, cooperation provides diver-sity gain. The proposed implementation of the above informa-tion theoretic coding with network coding is very simple and cost effective.
We show that mutual exchange of independent information between two nodes in a wireless network can be effi-ciently performed by exploiting network coding and the physical-layer broadcast property offered by the wireless medium. The proposed approach improves upon conventional solutions that separate the processing of the two unicast sessions, corresponding to information transfer along one direction and the opposite direction. We propose a distributed scheme that obviates the need for synchronization and is robust to random packet loss and delay, and so on. The scheme is simple and incurs minor overhead.
We compare multicast network coding and routing
for a time-varying wireless network model with interference-
determined link capacities. We use dynamic back pressure
algorithms that are optimal for intra-session network coding
and routing respectively. Our results suggest that under such conditions, the gap in multicast capacity between network coding and routing can decrease relative to a collision-based wireless model with fixed link capacities.
The marriage of network coding and wireless packet networks is a natural and attractive one. So, despite network coding being a still nascent field, a considerable body of work on this subject already exists. In this paper, we give a brief overview of this work and hope, thereby, to provide the reader with a firm theoretical basis from which practical implementations and theoretical extensions can be developed.
Network coding, where relay nodes combine the information received from multiple links rather than simply replicating and forwarding the received packets, has shown the promise of significantly improving system performance. In very recent works, multiple researchers have presented methods for increasing system throughput by employing network coding inspired methods to mix packets at the physical layer: physical-layer network coding (PNC). A common example used to validate much of this work is that of two sources exchanging information through a single intervening relay -a situation that we denote the "exchange channel". In this paper, achievable rates of various schemes on the exchange channel are considered. Achievable rates for traditional multi-hop routing approaches, network cod-ing approaches, and various PNC approaches are considered. A new method of PNC inspired by Tomlinson-Harashima precoding (THP), where a modulo operation is used to control the power at the relay, is introduced.
Scalable and reliable routing is a critical issue in sensor network deployment. A number of approaches have been proposed for sensor network routing, but sensor field implementation tends to be lacking in the literature. In our study, the problems of scalability and reliability in sensor network routing are addressed through a simple but powerful scheme implemented on Mica2 motes running TinyOS along with other, more widely-used routing protocols. Motes are tested in an outdoor sensor field, and detailed experiments are carried out for performance analysis. This paper presents the implementation details and the results obtained from head-to-head comparison of routing protocols. The proposed protocol delivers 93% of packets injected at a rate of one packet per second in networks with end to end hop distances of over 10 hops-a result which significantly improves upon results from the standard TinyOS routing implementation of MINTRoute. The promising results can be explained by the key protocol properties of reliability (via multi-path redundancy), scalability (with efficiently contained flooding), and flexibility (source-tunable per-packet priority) which are achieved without adding protocol complexity or resource consumption. These strengths enable the protocol to outperform even sophisticated link estimation based protocols especially in adverse outdoor sensor field environments.
This paper considers relaying techniques that increase the achievable throughput in multi-hop wireless networks by taking advantage of the bi-directional traffic flow. Such a relaying technique is termed relaying with Bi-directional Amplification of Throughput (BAT-relaying). The BAT-relaying is utilizing the concept of anti-packets, defined for bi-directional traffic flows. The relay node combines the anti-packets that are destined for different nodes and broadcasts the combined packet. Two BAT-relaying techniques have been proposed previously, Decode-and-Forward (DF) BAT-relaying and Amplify-and-Forward (AF) BAT-relaying. While in DF the relay node combines the packets by an XOR operation, AF BAT-relaying utilizes the inherent packet combining provided by the multiple access channel. In an errorless channel, AF has always higher achievable throughput than DF, but in noisy channels the noise amplification can severely degrade the performance of AF. In this paper we introduce a new scheme for BAT-relaying, termed Denoise-And-Forward (DNF) BAT-Relaying. The DNF BAT-relaying also makes use of the combining provided by the multiple access channel, but it removes the noise from the combined anti-packets before broadcasting to the destinations. While in the noiseless channel DNF and AF offer the same throughput performance which is superior to DF BAT-relaying, in large regions of the lower SNR values DNF BAT-relaying has the best throughput performance of all three schemes. Due to the unconventional nature of the BAT-relaying schemes, there are many open issues for further investigation. The design of a practical DNF scheme concerns several protocol layers, including modulation and coding.
In studying the performance of coded communications over memoryless channels (with or without fading), the results are given as upper bounds on the average bit error probability (BEP). In principle, there are three different approaches to arriving at these bounds, all of which employ obtaining the so-called pairwise error probability, or the probability of choosing one symbol sequence over another for a given pair of possible transmitted symbol sequences, followed by a weighted summation over all pairwise events. In this chapter, we will focus on the results obtained from the third approach since these provide the tightest upper bounds on the true performance. The first emphasis will be placed on evaluating the pairwise error probability with and without CSI, following which we shall discuss how the results of these evaluations can be used via the transfer bound approach to evaluate average BEP of coded modulation transmitted over the fading channel.
Network coding has been a prominent approach to a series of problems that used to be considered intractable with traditional transmission paradigms. Recent work on network coding includes a substantial number of optimization based protocols, but mostly for wireline multicast networks. In this paper, we consider maximizing the benefits of network coding for unicast sessions in lossy wireless environments. We propose Optimized Multipath Network Coding (OMNC), a rate control protocol that dramatically improves the throughput of lossy wireless networks. OMNC employs multiple paths to push coded packets to the destination, and uses the broadcast MAC to deliver packets between neighboring nodes. The coding and broadcast rate is allocated to transmitters by a distributed optimization algorithm that maximizes the advantage of network coding while avoiding congestion. With extensive experiments on an emulation testbed, we find that OMNC achieves more than two-fold throughput increase on average compared to traditional best path routing, and significant improvement over existing multipath routing protocols with network coding. The performance improvement is notable not only for one unicast session, but also when multiple concurrent unicast sessions coexist in the network. © 2009, by The Institute of Electrical Electrical and Electronics Engineers, Inc. All rights reserved.
A new wireless routing protocol called OCR was presented, enhancing throughput of unicast traffic in wireless mesh networks (WMN). In the routing discovery, OCR could actively detect the possible coding opportunities and make a tradeoff among these factors: utilizing the coding opportunities, finding the shortest path and neatly avoiding the congestion. The simulation results show that the network throughput can be greatly improved by OCR, compared to the traditional routing protocol, when using COPE.
Goldsmith and Varaiya derived the capacity of a single-user flat-fading channel with channel measurement information at the transmitter and receiver for various adaptive transmission policies. In this chapter, we first apply the general theory that they developed and present closed-form expressions for the capacity of Rayleigh fading channels under different adaptive transmission schemes with and without diversity combining. In particular, we consider three adaptation policies: optimum simultaneous power and rate adaptation, constant power with optimum rate adaptation, and channel inversion with fixed rate. We then investigate the impact of maximal-ratio diversity (MRC) on the Shannon capacity in conjunction with each of these adaptive transmission schemes.
This paper describes ExOR,an integrated routing and MAC protocol that increases the throughput of large unicast transfers in multi-hop wireless networks. ExOR chooses each hop of a packet's route after the transmission for that hop, so that the choice can reflect which intermediate nodes actually received the transmission. This deferred choice gives each transmission multiple opportunities to make progress. As a result ExOR can use long radio links with high loss rates, which would be avoided by traditional routing. ExOR increases a connection's throughput while using no more network capacity than traditional routine.ExOR's design faces the following challenges. The nodes that receive each packet must agree on their identities and choose one forwarder.The agreement protocol must have low overhead, but must also be robust enough that it rarely forwards a packet zero times or more than once. Finally, ExOR must choose the forwarder with the lowest remaining cost to the ultimate destination.Measurements of an implementation on a 38-node 802.11b test-bed show that ExOR increases throughput for most node pairs when compared with traditional routing. For pairs between which traditional routing uses one or two hops, ExOR's robust acknowledgments prevent unnecessary retransmissions,increasing throughput by nearly 35%. For more distant pairs, ExOR takes advantage of the choice of forwarders to provide throughput gains of a factor of two to four.
Traditionally, interference is considered harmful. Wireless networks strive to avoid scheduling multiple transmissions at the same time in order to prevent interference. This paper adopts the opposite approach; it encourages strategically picked senders to interfere. Instead of forwarding packets, routers forward the interfering signals. The destination leverages network-level information to cancel the interference and recover the signal destined to it. The result is analog network coding because it mixes signals not bits.
So, what if wireless routers forward signals instead of packets? Theoretically, such an approach doubles the capacity of the canonical 2-way relay network. Surprisingly, it is also practical. We implement our design using software radios and show that it achieves significantly higher throughput than both traditional wireless routing and prior work on wireless network coding.
In this paper, we study the outage probability performance of a very well-known bidirectional protocol based on decode-and-forward relaying: physical-layer network coding (PNC). We first derive an exact closed-form outage probability expression for the PNC protocol. To provide more insight, we also derive asymptotic outage probability expression. Finally, the validity of the derived expressions is confirmed by numerical results.
This paper proposes a network coding-aware multi-path routing (CAMP) protocol, which forwards packets over multiple paths dynamically based on path reliability and coding opportunity. CAMP employs a route discovery mechanism which returns to the source multiple paths along with ETX (expected transmission count) of all links on each path. With its unique forwarding mechanism, CAMP splits the traffic among multiple paths and actively creates, while not merely waiting for, the coding opportunity by switching its path to maximize the switching gain and thus improves the network throughput. The experimental results demonstrate that CAMP can achieve much higher throughput than peer schemes for delivering packets in wireless networks. © by Institute of Software, the Chinese Academy of Sciences. All rights reserved.
Network coding considers as a major ability to achieve higher throughput. Toward that goal, this article investigates and analyzes soft decision scheme of network coding (SDS-NC) at relay node to exchange encoding BPSK packets between two nodes with help of the relay over an additive white Gaussian noise (AWGN) channel by considering the maximum-likelihood (ML) detection metric at the relay. We also consider the Soft Bit Forward (SBF) in order to a sure that the soft schemes perform well. The objective of soft scheme is to achieve better normalized throughput with reliability of information transmission and to solve the complexity. The numerical results of a Soft scheme show that the results obtained are reasonable.
Recently, network coding considers as a major ability to achieve effectiveness and Reliability for wireless networks. This article examine the channel capacity and Bit Error Rate (BER) of Network Coding and channel coding for different channel models using convolutional encoding with Viterbi decoding algorithm. We identify the results of a bit stream transmitted through different channel models such as Binary Symmetric Channel (BSC), Additive White Gaussian Noise (AWGN) and Slow Rayleigh Fading Channel (SRFC). It shown that, all channel models achieve the same capacity in higher signal to noise ratio (SNR). Furthermore, the BER performance has shown that the propose scheme outperform conventional scheme. We have done our simulation using Matlab to show the performance evaluation of both schemes for different scenario. mobile communication. We analyze the channel capacity and BER performance of both schemes with different channel models. It demonstrated that, the proposal scheme achieves the same channel capacity in high SNR. In this paper, we describe the system model and the algorithm description of the General network scheme. In this regards, we proposed a new scheme to improve the performance of model. We then describe the Analysis of the capacity in the three channel models. Results show that the performance of propose scheme outperform the conventional scheme.
In identical Nakagami-m fading channels, the outage probability performance of network coding for multicast relay system is analyzed. The amplify-and-forward network coding (AFNC) transmission strategy is applied in the system. By using the outage event definition in multiuser communication system and the mutual information expressions of multiple access channels, the approximate expression of outage probability is derived at high SNR and the conclusion that the system diversity gain of AFNC is 2m is also obtained, which is verified by numerical simulations. Simulation results also show that, AFNC can outperform direct transmission without relay in the performances of system outage probability and symbol error ratio.
A new image relevance feedback mechanism based on selective neural network ensemble is proposed in this paper. At the beginning, positive and negative examples are marked by users, and several classifiers are trained using improved Bagging algorithm. Afterward a novel simple cluster method (AM) based on accessibility matrix is proposed to cluster individual networks. This new method can obtain the number of clusters automatically. Then, the most superior network in each class is chosen to form the ensemble. Finally, the similar images are located in the related class. The application in the COREL image database demonstrates that the algorithm obtains higher recall and precision ratio over other methods (e.g., neural network ensembles based on tradition K-means cluster and min-max distance (MM) cluster) and achieves low time complexity.
Using the intrinsic broadcast property of the wireless medium, network coding has become an important technology in the area of wireless networks. Network coding needs multiple flows to gather together which will contribute to interference between these flows and decrease the transmission utilization. In this paper, we investigate the relation between coding and interference in multi-hop wireless networks and illustrate tradeoff between performance degradation of interference and performance gain of coding. We first summarize the coding technology and propose a coding rule. Then, we combine the interference cost and coding gain to form the interference-avoid and coding-aware metric (ICM). Finally, we conclude that network performance including network throughput and end-to-end delay can be greatly improved by using ICM.
The energy industry technology innovation (EITI) was defined and classified into several types on the base of energy technology history and its characteristics. Then, according to the energy industry features in China and current international circumstances, the six factors which affected the energy industry in China to do technology innovation were got and their characteristics were that both per-capita resources was less and its proportion of high quality was low, the energy efficiency is urgent to improve, environment issues caused by energy was urgent to be improved, fluctuations in prices caused the renewable energy technology feasible, industrial interactive growing, and tiny history events.
Cooperation among network users provides trans- mit diversity in cases where wireless transmitters, due to size and power limitation, cannot support multiple antennas. We consider cooperation between M users, where each user achieves space-time diversity by using other users' antennas as relays. Cooperation among users has been shown to achieve impressive gains as compared to a non-cooperative system while maintaining the same information rate, transmit power, and bandwidth (1), (2), (3), (4). This paper formulates an optimum power allocation scheme appropriate for a cooperative network using transparent relaying. It will be shown that the proposed allocation scheme significantly outperforms the equal power allocation scheme, e.g., by up to 7 dB at a bit error rate of 10 ¡3 . The results presented here may serve as bounds for the performance assessment of sub-optimal (but practical) algorithms. I. I NTRODUCTION
This study addresses some of the inhibiting aspects of the hydrodesulfurization (HDS) of 4,6-diethyldibenzothiophene on a sulfided CoMo/Al2O3–SiO2 catalyst at relatively low hydrogen pressures. It is shown that thermodynamic equilibrium does not play a significant role in inhibiting sulfur removal at 2.17 MPa hydrogen pressure at least up to 370°C. Both 3-ethylcarbazole and naphthalene inhibit the HDS rate, with the former being far more potent. Other electron-rich or electron-deficient substituted carbazoles are also strong inhibitors, suggesting that the substituent-induced electronic effect is not a factor governing the poisoning potency of the carbazole family. Operating at high temperatures is more effective in mitigating the inhibiting effect than operating at high hydrogen pressures. A strong inhibiting effect can lead to falsification of the overall HDS kinetics.
Osseointegration is critical for implant fixation, and mechanical stimuli play a role in this process. Our long term goal is to investigate the relationship between local mechanical environment and osseointegration. In this paper, as a first step in the study, we constructed an approximate D model of the in-vivo test and focused on calculating the strain fields around the implant. We first demonstrated that 3D finite element models gave significant differences compared with 2D models. The D model was then used to study strain distributions as gap tissue properties were varied over an experimentally estimated range in the first 7 days post implant. Results for strain concentration in gap tissue around the circumferential ridges and bottom of the implant agreed, on average, with previous 2D studies. Variations of the strain field around the implant were consistent with bone healing and remodeling trends around the implant between post-surgical days 1 and 5, and 6 and 7.
We study a new class of multiuser source coding problems inspired by network communications. We propose the use of coding in networks for the purpose of multicasting. This concept may have significant impact on future design of switching systems
Presenting the fundamentals of cooperative communications and networking, this book treats the concepts of space, time, frequency diversity and MIMO, with a holistic approach to principal topics where significant improvements can be obtained. Beginning with background and MIMO systems, Part I includes a review of basic principles of wireless communications and space-time diversity and coding. Part II then presents topics on physical layer cooperative communications such as relay channels and protocols, performance bounds, multi-node cooperation, and energy efficiency. Finally, Part III focuses on cooperative networking including cooperative and content-aware multiple access, distributed routing, source-channel coding, and cooperative OFDM. Including end-of-chapter review questions, this text will appeal to graduate students of electrical engineering and is an ideal textbook for advanced courses on wireless communications. It will also be of great interest to practitioners in the wireless communications industry. Presentation slides for each chapter and instructor-only solutions are available at www.cambridge.org/9780521895132.
A Mobile Ad hoc NETwork (MANET) is consisting of a collection of wireless mobile nodes, which form a temporary network without relying on any existing infrastructure or centralized administration. Since the bandwidth of MANETs is limited and shared between the participating nodes in the network, it is important to efficiently utilize the network bandwidth. Multicasting can minimize the link bandwidth consumption and reduce the communication cost by sending the same data to multiple participants. Multicast service is critical for applications that need collaboration of team of users. Multicasting in MANETs becomes a hot research area due to the increasing popularity of group communication applications such as video conferencing and interactive television. Recently, multimedia and group-oriented computing gains more popularity for users of ad hoc networks. So, effective Quality of Service (QoS) multicasting protocol plays significant role in MANETs. In this paper, we are presenting an overview of set of the most recent QoS multicast routing protocols that have been proposed in order to provide the researchers with a clear view of what has been done in this field.
In cooperative transmission users are allowed to share antennas to transmit their messages to a common des-tination. Users employ either amplify-and-forward or decode-and-forward strategies to forward each others' messages. In network-coding-based cooperative transmission schemes, users are allowed to combine their own and their partner's message by a network-coding operation. This work analysis the outage probability of a network-coding-based decode-and-forward cooperative transmission scheme, when non-ideal inter-user channels exist. A modulo-2 summation is used to implement the network coding, and transmissions are done us-ing time division duplex channels. At the destination, identical messages are combined using either Selection combining or Maximum-Ratio combining. The numerical results show that a diversity order in the range of two can be obtained using this scheme, taking point-to-point transmission as a baseline. The work is extended to goodput analysis, based on feedback from the destination.
Wireless mesh networks hold promises to provide robust and high-throughput data delivery to wireless users. In a mesh network, high-speed Access Points (HAPs), equipped with advanced antennas, communicate with each other over wireless channels and form an indoor/outdoor broadband backhaul. This backbone efficiently forwards user traffic to a few gateway APs (GAPs), which additionally have high-speed connections to the wired Internet. In this paper, we describe ROMER, a resilient and opportunistic routing solution for mesh networks. ROMER balances between long-term route stability and short-term opportunistic performance. It builds a runtime, forwarding mesh on a per-packet basis that offers a set of candidate routes. The actual forwarding path by each packet opportunistically adapts to the dynamic channel condition and exploits the highest-rate wireless channels at the time. To improve resilience against lossy links, HAP failures or HAPs under DoS attacks, ROMER delivers redundant data copies in a controlled and randomized manner over the candidate forwarding mesh. We evaluate the effectiveness of ROMER through both simulations and analysis.
We propose to use joint network-channel coding based on turbo codes for the multiple-access relay channel. Such a system can be used for the cooperative uplink for two mobile stations to a base station with the help of a relay. We compare the proposed system with a distributed turbo code for the relay channel and with a system which uses separate network-channel coding for the multiple-access relay channel. Simulation results confirm that the systems with network coding for the multiple-access relay channel gain cooperative diversity compared to the system with the distributed turbo code for the relay channel. Moreover, the results show that joint network-channel coding outperforms separate network-channel coding. The reason for this is that the redundancy which is contained in the transmission of the relay can be exploited more efficiently with joint network-channel coding
Network coding is known to improve network throughput by mixing information from different flows and conveying more information in each transmission. Recently there have been some proposals for applying network coding to wireless mesh networks leveraging the broadcast nature of wireless transmissions. These approaches exploit coding opportunities passively while forwarding packets but they do not proactively change routing of flows to create more coding opportunities. In this paper, we attempt to investigate the extent of performance gain possible when routing decisions are made with the awareness of coding. We first define the expected number of coded transmissions for a successful exchange of packets between two nodes through an intermediate node. We then formulate optimal routing with coding, given the topology and traffic, as a linear programming problem. We conduct a preliminary evaluation of coding-aware routing and show that it offers significant gain particularly when there are many long distance flows.
Multihop wireless mesh networks are becoming a new attractive communication paradigm. Many cities and public places have deployed or are planning to deploy mesh networks to provide Internet access to residents and local businesses. Routing protocol design is critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along pre-determined paths and have been shown ineffective in coping with unreliable and unpredictable wireless medium. In this paper, we develop a simple opportunistic adaptive routing protocol (SOAR) for wireless mesh networks. SOAR maximizes the progress each packet makes by using priority-based timers to ensure that the most preferred node forwards the packet with little coordination overhead. Moreover, SOAR minimizes resource consumption and duplicate transmissions by judiciously selecting forwarding nodes to prevent routes from diverging. To further protect against packet losses, SOAR uses local recovery to retransmit a packet when an ACK is not received within a specified time. SOAR uses a combination of selective ACKs, piggyback ACKs, and ACK compression to protect against ACK loss while minimizing ACK overhead. We evaluate SOAR using NS-2 simulations. Our preliminary results show that SOAR is promising to achieve high efficiency and effectively support multiple simultaneous flows.
Routing protocols have traditionally been based on finding shortest paths under certain cost metrics. A conventional routing metric models the cost of a path as the sum of the costs on the constituting links. This paper introduces the concept of a Markovian metric, which models the cost of a path as the cost of the first hop plus the cost of the second hop conditioned on the first hop, and so on. The notion of the Markovian metric is fairly general. It is potentially applicable to scenarios where the cost of sending a packet (or a stream of packets) over a link may depend on the previous hop of the packet (or the stream). Such scenario arises, for instance, in a wireless mesh network equipped with local mixing, a recent link layer advance. This scenario is examined as a case study for the Markovian metric. The local mixing engine sits between the routing and MAC layers. It maintains information about the packets each neighbor has, and identifies opportunities to mix the outgoing packets via network coding to reduce the transmissions in the air. We use a Markovian metric to model the reduction of channel resource consumption due to local mixing. This leads to routing decisions that can better take advantage of local mixing. We have implemented a system that incorporates local mixing and source routing using a Markovian metric in Qualnet. The experimental results demonstrate significant throughput gain and resource saving.
A recent approach, COPE, for improving the throughput of unicast traffic in wireless multi-hop networks exploits the broadcast nature of the wireless medium through opportunistic network coding. In this paper, we analyze throughput improvements obtained by COPE-type network coding in wireless networks from a theoretical perspective. We make two key contributions. First, we obtain a theoretical formulation for computing the throughput of network coding on any wireless network topology and any pattern of concurrent unicast traffic sessions. Second, we advocate that routing be made aware of network coding opportunities rather than, as in COPE, being oblivious to it. More importantly, our work studies the tradeoff between routing flows "close to each other" for utilizing coding opportunities and "away from each other" for avoiding wireless interference. Our theoretical formulation provides a method for computing source-destination routes and utilizing the best coding opportunities from available ones so as to maximize the throughput. We handle scheduling of broadcast transmissions subject to wireless transmit/receive diversity and link interference in our optimization framework. Using our formulations, we compare the performance of traditional unicast routing and network coding with coding-oblivious and coding-aware routing on a variety of mesh network topologies, including some derived from contemporary mesh network testbeds. Our evaluations show that a route selection strategy that is aware of network coding opportunities leads to higher end-to-end throughput when compared to coding-oblivious routing strategies.
We introduce an extension of the relay channel that we call two-way relay channel. The two-way relay channel consists of two users which want to communicate to each other with the help of one relay. We consider the time-division two-way relay channel without power control, where the broadcast channels are orthogonalized in time and where the two users and the relay use the same transmission power. We describe a joint network-channel coding method for this channel model, where channel codes are used at both users and a network code is used at the relay. The channel code of one user and the network code form a distributed turbo code which we call turbo network code and which can be iteratively decoded at the other user. Moreover, we conjecture closed expressions for lower bounds for the channel capacities of the time-division relay and two-way relay channel without power control and deliver simulation results of the proposed turbo network code.
This paper investigates the diversity gain offered by implementing network coding (R. Ahlswede et al., 2000) over wireless communication links. The network coding algorithm is applied to both a wireless network containing a distributed antenna system (DAS) as well as one that supports user cooperation between users. The results show that network-coded DAS leads to better diversity performance as compared to conventional DAS, at a lower hardware cost and higher spectral efficiency. In the case of user cooperation, network coding yields additional diversity, especially when there are multiple users