Conference Paper

Performance study of ETX based wireless routing metrics

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Abstract

Being most popular and IETF standard metric, minimum hop count is appropriately used by ad hoc networks, as new paths must rapidly be found in the situations where quality paths could not be found in due time due to high node mobility. There always has been a tradeoff between throughput and energy consumption, but stationary topology of WMNs and high node density of WSN's benefit the algorithms to consider quality-aware routing to choose the best routes. In this paper, we analytically review ongoing research on wireless routing metrics which are based on ETX (expected transmission count) as it performs better than minimum hop count under link availability. Performances over ETX, target platforms and design requirements of these ETX based metrics are high-lighted. Consequences of the criteria being adopted (in addition to expected link layer transmissions & retransmissions) in the form of incremental: (1) performance overheads and computational complexity causing inefficient use of network resources and instability of the routing algorithm, (2) throughput gains achieved with better utilization of wireless medium resources have been elaborated.

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... Along with the existing implementation of three link metrics, ETX, Minimum Delay (MD), and Minimum Loss (ML), we implement inverse ETX; invETX with OLSR using NS-2. 34. The simulation results show that how the computational burden of a metric degrades the performance of the respective protocol and how a metric has to trade-off between different performance parameters. ...
... For delay sensitive applications, DYMO in reactive protocols and OLSR in proactive protocols are the plausible choices. During all this evaluation, we come to realize that the most important component of a routing protocol is routing link metric, so, in future we are interested to propose and implement a new ETX-based routing link metric with AODV and OLSR, as discussed in [34]. ...
... We use the implementation of ETX, Minimum Delay (MD) [76], and ML [77] with OLSR [78] in NS2-2. 34. Then we implement the fourth metric, invETX, as expressed by eq. ...
Article
This dissertation endeavors to contribute enhancements in goodputsof the IEEE 802.11-based Wireless Multi-hop Networks (WMhNs).By performing exhaustive simulations, for the deep analysis and detailed assessment of both reactive (AODV, DSR, DYMO) and proactive (DSDV, FSR, OLSR) protocols for varying mobilities, speeds, network loads and scalabilities, it is observed that a routing link metric is a significant component of a routing protocol. In addition to finding all available paths, the fastest end-to-end route is selected by a link metric for the routing protocol. This study aims the quality routing. In the class of quality link metrics, Expected Transmission Count (ETX) is extensively used. Thus, the most recently proposed ETX-based metrics have been analyzed. Though, newly developed metrics over perform ETX but still they can be improved. By profound analysis and particularized comparison of routing protocols depending upon their classes (reactive and proactive) and ETX-based metrics, we come to realize that users always demand proficient networks. In fact, WMhNs are facing several troubles which they expect to be resolved by the routing protocol operating them. Consequently, the protocol depends upon the link metric for providing quality paths. So, we identify and analyze the requirements to design a new routing link metric for WMhNs. Because, considering these requirements, when a link metric is proposed, then : firstly, both the design and implementation of the link metric with a routing protocol become easy. Secondly, the underlying network issues can easily be tackled. Thirdly, an appreciable performance of the network is guaranteed. Keeping in view the issues of WMhNs, increasing demands of users and capabilities of routing protocols, we propose and implement a new quality link metric, Interference and Bandwidth Adjusted ETX (IBETX). As, MAC layer affects the link performance and consequently the route quality, the metric therefore, tackles the issue by achieving twofold MAC-awareness. Firstly, interference is calculated using cross-layered approach by sending probes to MAC layer. Secondly, the nominal bit rate information is provided to all nodes in the same contention domain by considering the bandwidth sharing mechanism of 802.11. Like ETX, our metric also calculates link delivery ratios that directly affect throughput and selects those routes that bypass dense regions in the network. Simulation results by NS-2 show that IBETX gives 19% higher through put than ETX and 10% higher than Expected Throughput (ETP). Our metric also succeeds to reduce average end-to-end delay up to 16% less than Expected Link Performance (ELP) and 24% less than ETX
... The maximum reachability of a node belonging to Minimizing Longer path increases routing (1) By minimizing the number of transmi- Hop count [14] path length latency and reduces throughssions and (2) path selection with miniput of a path mum loss rates or higher probabilities of successful transmissions, etc. Balancing traffic Overloaded traffic causes drop Divert traffic from congested path or Transmission load rate due to congestion overloaded nodes to underloaded or reduction [15] idle ones Minimizing delay Delay results time-out buffer Delay can be reduced with selection ETX [15], [14], per of a path having minimum intraflow hop RTT, [11] per and interflow interferences along with hop PktPair [11] queuing delays and maximum link capacity ML [3] Maximizing networks capacity directly effects (1) Minimize interferences or retransmissions, MIC [14] aggregating throughput and (2) allow the multiple bandwidth rates to coexist in a network where a higher channel rate is used over each link Minimizing energy A path with an unreliable Reduction in retransmissions during MTPR [17], consumption link produces longer delay due routing to optimize communication delay MBCR [18] to higher retransmission rates and ultimately results in an increase in energy consumption Minimizing channel/ Data flow switching on different Interface assignment strategy keeps MIC [14], interface switching channels results in delay one interface fixed on a specific channel, WCETT [14] while other interfaces can be switched among the remaining channels; when necessary, Minimizing the Computational overhead consumes computations should be considered InvETX [1] computational memory, processing capability, that must not consume memory, processing overhead and battery power capability, and, most importantly, battery power Minimizing Intraflow and interflow interferences During path calculation, capture diversity MCR protocol interference result in bandwidth starvation of channel assignments and link capacity [14] and [14] Maximizing Instability in path weight results Load sensitivity or topology- Link affinity metric [19] route stability in drop rates dependent metrics solve instability issues with MCMR [20] Maximizing Faulty routes cause drop rates This problem can be solved through wireless ad hoc fault tolerance/ in high network flows providing redundant information of network [21] minimizing route alternative paths sensitivity Avoiding short-and Redundant links due to short- (1) Minimum TTL value that eliminates OLSR in long-lived and long-lived loops resulted in mini-loops [16]; (2) fresh sequence sparse WMNs [16] loops more path lengths and consequently number, etc. quently increased E2ED Considering E2ED in static networks cause A suitable trade-off helps to increase ML [3] performance drop rate efficiency trade-offs Also, the MPR(u) set of a node (u), a subset of H 1 (u), can be defined as follows: ...
... The maximum reachability of a node belonging to Minimizing Longer path increases routing (1) By minimizing the number of transmi- Hop count [14] path length latency and reduces throughssions and (2) path selection with miniput of a path mum loss rates or higher probabilities of successful transmissions, etc. Balancing traffic Overloaded traffic causes drop Divert traffic from congested path or Transmission load rate due to congestion overloaded nodes to underloaded or reduction [15] idle ones Minimizing delay Delay results time-out buffer Delay can be reduced with selection ETX [15], [14], per of a path having minimum intraflow hop RTT, [11] per and interflow interferences along with hop PktPair [11] queuing delays and maximum link capacity ML [3] Maximizing networks capacity directly effects (1) Minimize interferences or retransmissions, MIC [14] aggregating throughput and (2) allow the multiple bandwidth rates to coexist in a network where a higher channel rate is used over each link Minimizing energy A path with an unreliable Reduction in retransmissions during MTPR [17], consumption link produces longer delay due routing to optimize communication delay MBCR [18] to higher retransmission rates and ultimately results in an increase in energy consumption Minimizing channel/ Data flow switching on different Interface assignment strategy keeps MIC [14], interface switching channels results in delay one interface fixed on a specific channel, WCETT [14] while other interfaces can be switched among the remaining channels; when necessary, Minimizing the Computational overhead consumes computations should be considered InvETX [1] computational memory, processing capability, that must not consume memory, processing overhead and battery power capability, and, most importantly, battery power Minimizing Intraflow and interflow interferences During path calculation, capture diversity MCR protocol interference result in bandwidth starvation of channel assignments and link capacity [14] and [14] Maximizing Instability in path weight results Load sensitivity or topology- Link affinity metric [19] route stability in drop rates dependent metrics solve instability issues with MCMR [20] Maximizing Faulty routes cause drop rates This problem can be solved through wireless ad hoc fault tolerance/ in high network flows providing redundant information of network [21] minimizing route alternative paths sensitivity Avoiding short-and Redundant links due to short- (1) Minimum TTL value that eliminates OLSR in long-lived and long-lived loops resulted in mini-loops [16]; (2) fresh sequence sparse WMNs [16] loops more path lengths and consequently number, etc. quently increased E2ED Considering E2ED in static networks cause A suitable trade-off helps to increase ML [3] performance drop rate efficiency trade-offs Also, the MPR(u) set of a node (u), a subset of H 1 (u), can be defined as follows: ...
... The maximum reachability of a node belonging to Minimizing Longer path increases routing (1) By minimizing the number of transmi- Hop count [14] path length latency and reduces throughssions and (2) path selection with miniput of a path mum loss rates or higher probabilities of successful transmissions, etc. Balancing traffic Overloaded traffic causes drop Divert traffic from congested path or Transmission load rate due to congestion overloaded nodes to underloaded or reduction [15] idle ones Minimizing delay Delay results time-out buffer Delay can be reduced with selection ETX [15], [14], per of a path having minimum intraflow hop RTT, [11] per and interflow interferences along with hop PktPair [11] queuing delays and maximum link capacity ML [3] Maximizing networks capacity directly effects (1) Minimize interferences or retransmissions, MIC [14] aggregating throughput and (2) allow the multiple bandwidth rates to coexist in a network where a higher channel rate is used over each link Minimizing energy A path with an unreliable Reduction in retransmissions during MTPR [17], consumption link produces longer delay due routing to optimize communication delay MBCR [18] to higher retransmission rates and ultimately results in an increase in energy consumption Minimizing channel/ Data flow switching on different Interface assignment strategy keeps MIC [14], interface switching channels results in delay one interface fixed on a specific channel, WCETT [14] while other interfaces can be switched among the remaining channels; when necessary, Minimizing the Computational overhead consumes computations should be considered InvETX [1] computational memory, processing capability, that must not consume memory, processing overhead and battery power capability, and, most importantly, battery power Minimizing Intraflow and interflow interferences During path calculation, capture diversity MCR protocol interference result in bandwidth starvation of channel assignments and link capacity [14] and [14] Maximizing Instability in path weight results Load sensitivity or topology- Link affinity metric [19] route stability in drop rates dependent metrics solve instability issues with MCMR [20] Maximizing Faulty routes cause drop rates This problem can be solved through wireless ad hoc fault tolerance/ in high network flows providing redundant information of network [21] minimizing route alternative paths sensitivity Avoiding short-and Redundant links due to short- (1) Minimum TTL value that eliminates OLSR in long-lived and long-lived loops resulted in mini-loops [16]; (2) fresh sequence sparse WMNs [16] loops more path lengths and consequently number, etc. quently increased E2ED Considering E2ED in static networks cause A suitable trade-off helps to increase ML [3] performance drop rate efficiency trade-offs Also, the MPR(u) set of a node (u), a subset of H 1 (u), can be defined as follows: ...
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In this paper, we propose a new Quality Link Metric (QLM), “Inverse Expected Transmission Count (InvETX),” in Optimized Link State Routing (OLSR) protocol. Then, we compare performance of three existing QLMs which are based on loss probability measurements: Expected Transmission Count (ETX), Minimum Delay (MD), and Minimum Loss (ML) in Static Wireless Multihop Networks (SWMhNs). A novel contribution of this paper is enhancement in conventional OLSR to achieve high efficiency in terms of optimized routing load and routing latency. For this purpose, first we present a mathematical framework, and then to validate this frame work, we select three performance parameters to simulate default and enhanced versions of OLSR. The three chosen performance parameters are throughput, Normalized Routing Load, and End-to-End Delay. From the simulation results, we conclude that adjusting the frequencies of topological information exchange results in high efficiency.
... Along with the existing implementation of three link metrics, ETX, Minimum Delay (MD), and Minimum Loss (ML), we implement inverse ETX; invETX with OLSR using NS-2. 34. The simulation results show that how the computational burden of a metric degrades the performance of the respective protocol and how a metric has to trade-off between different performance parameters. ...
... We use the implementation of ETX, Minimum Delay (MD) [76], and ML [77] with OLSR [78] in NS2-2. 34. Then we implement the fourth metric, invETX, as expressed by eq. ...
... We implement and compare the performance of our proposed metric IBETX with ELP, ETX, and ETP in NS-2. 34. The window w used for link probe packets is chosen to be of size 10s and is named as τ t , as discussed in the last section. ...
... Our aim is to form a cluster of all the nodes that experience similar SINR, limited by a threshold. The concept of SINR in clustering of CR nodes are used in [18] (adopted from [19]). The authors have considered the impact of SINR imposed by collocated CR users on channel quality. ...
... Similarly, the signal power of neighbor SU k on the SU j is denoted by . Considering environmental noise as N, the signal to Noise Ratio (SNR) at SU node j for PU node i is computed as given below [19,25]. ...
... Equation (2) shows the impact of PU signals as well as neighbors CUs on a particular secondary user. considering interference into account, the ETT of a link l can be computed by calculating the expected number of transmissions ( ) required for successful delivery of the packet as stated in equation (3) as reported in [19]. ...
Article
A novel clustering approach for Cognitive Radio Ad Hoc Networks (CRAHNs) is proposed in this paper. The Signal to Interference and Noise Ratio (SINR) produced by Primary Users (PUs) on collocated Cognitive Users (CUs) along with Expected Transmission Time (ETT) among CUs is taken into account for cluster formation. The primary concern of the proposed work is to find a suitable method of cluster formation for efficient routing in CRAHN. The suggested algorithm is simulated in ns-3. Through the observed results, values of some base parameters for efficient clustering are established. Efficiency of the proposed approach is also compared with three existing cluster based protocols. Results reveal that the proposed algorithm performs better. One cluster maintenance algorithm is also proposed in the paper. Future scope of the work is outlined.
... Among them we find metrics indicating the distance from the destination measured in hops (hop count) or in distance units (measured on physical or virtual coordinates), the link reliability and packet loss due to congestion measured as the expected transmissions number (named usually ETX) until the packet is successfully received by the next hop node, the remaining energy of a node or of the nodes in a path. Different ways to quantify them exist (as discussed in[21]) with fifteen ways to quantify ETX proposed in[17]and a similar number reported in[7]for energy. Nevertheless, for a single network to satisfy diverse requirements, the design of proper composite metrics combining primary routing metrics in an additive (see e.g.[10]), lexicographic (see e.g.[14]) or more complicated (see e.g.[18]) manner has been pursued. ...
... Apart from ETX, an important number of metrics that capture link quality/reliability has been proposed as e.g. ETT[17]. Furthermore, significant research work (e.g.[32],[33]) has been devoted to the design of interference-aware routing metrics. ...
Article
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The use of Wireless Sensor Networks (WSN) in a wide variety of application domains has been intensively pursued lately while Future Internet designers consider WSN as a network architecture paradigm that provides abundant real-life real-time information which can be exploited to enhance the user experience. The wealth of applications running on WSNs imposes different Quality of Service requirements on the underlying network with respect to delay, reliability and loss. At the same time, WSNs present intricacies such as limited energy, node and network resources. To meet the application’s requirements while respecting the characteristics and limitations of the WSN, appropriate routing metrics have to be adopted by the routing protocol. These metrics can be primary (e.g. expected transmission count) to capture a specific effect (e.g. link reliability) and achieve a specific goal (e.g. low number of retransmissions to economize resources) or composite (e.g. combining latency with remaining energy) to satisfy different applications needs and WSNs requirements (e.g. low latency and energy consumption at the same time). In this paper, (a) we specify primary routing metrics and ways to combine them into composite routing metrics, (b) we prove (based on the routing algebra formalism) that these metrics can be utilized in such a way that the routing protocol converges to optimal paths in a loop-free manner and (c) we apply the proposed approach to the RPL protocol specified by the ROLL group of IETF for such low power and lossy link networks to quantify the achieved performance through extensive computer simulations.
... Moreover, it also considers the problem of locating BS outside the network. In[29]authors introduce adopted authentication approach for protecting our Ad-hoc wireless network by even-odd function. In this function, mobile node compute and generates random even or odd number during signaling process. ...
... We can also use sink mobility to improve the energy utilization efficiency as done in[30,37,38]. In future, we also aim to improve the network energy utilization in the light of wireless ad-hoc networks[29],[30],[33],[34],[35]and[36]. ...
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In this paper, we propose Regional Energy Efficient Cluster Heads based on Maximum Energy (REECH-ME) Routing Protocol for Wireless Sensor Networks (WSNs). The main purpose of this protocol is to improve the network lifetime and particularly the stability period of the network. In REECH-ME, the node with the maximum energy in a region becomes Cluster Head (CH) of that region for that particular round and the number of the cluster heads in each round remains the same. Our technique outperforms LEACH [1] which uses probabilistic approach for the selection of CHs. We also implement the Uniform Random Distribution Model to find the packet drop to make this protocol more practical. We also calculate the confidence interval of all our results which helps us to visualize the possible deviation of our graphs from the mean value.
... SINR computation: Let us assume that signal power of node PU i at node SU j is E Si(j) . Considering environmental noise as N, the signal to noise Ratio (SNR) at SU node j for PU node i is computed as given below [17]. ...
... It reasonably predicts the link quality and a lower ETT is a desirable criterion for better throughput. Without considering interference into account, the ETT can be computed by calculating the expected number of transmission (E TX(l) ) required for successful delivery of the packet as stated below [17]. ...
Article
A novel clustering approach for cognitive nodes in CRN based Ad Hoc Networks (CRAHNs) is proposed in this paper. The Signal to Interference plus Noise Ratio (SINR) produced by Primary Users (PUs) on collocated Cognitive Users (CUs) along with Expected Transmission Time (ETT) among CUs is taken into account in order to form the clusters. The operation of CUs, either during cluster formation or data transmission no way harms the ongoing transmission of PU. The main aim here is to find suitable method of cluster formation so that the findings of this work can be used for developing efficient cluster based routing protocol for CRAHN. A medium scale network with up to 200 CUs are taken for experiment and some reasonable values for influential parameters are presented here.
... There are two sorts of OFs by the IETF for RPL [10], OF0 and MRHOF. The OF0 uses hop count, whereas MRHOF uses ETX as a routing metric [13,14]. As per [15] the implementation of MRHOF is suitable for data transfer in the reliable network and OF0 implementation is suitable for fast formation network. ...
... Default routing metric used by RPL is ETX [13]. To calculate ETX, every node broadcasts an advertising message periodically. ...
Article
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The main objective of Internet of Things (IoT) is to connect almost all the devices anywhere and everywhere in the world. IoT network is heterogeneous in nature, hence routing the data packets in this network is a big challenge. Routing Protocol for Low Power Lossy Network (RPL), has been designed by Internet Engineering Task Force (IETF) for such type of network. The existing design of RPL Objective Function (OF) is insufficient to cover all the issues of IoT applications. In this paper, the proposed OFs designs using various routing metrics are used to enhance the performance of the IoT applications. The analysis for various scenarios for these designs shows that only traditional hop and Expected Transmission Count (ETX) routing parameters will not fit for the smart applications need. The routing metric selection according to the application requirement is the principal idea of the proposed design. Three metrics ETX, Content and Energy, single and combination with each other are used to enhance the design of objective function of RPL for IoT applications. The enhanced triggering technique is added in these designs for the improvement of RPL. This technique will eliminate the cumulative effect of the short-listen problem of default trickle timer. The result analysis done using Cooja simulator along with Contiki Operating System (OS) states that, all the designs are performing well in one or other manner than the traditional OF. Energy combined with Content (EC) and aggregation with Enhanced timer (EC_En_Timer) design gives better result for Packet Delivery Ratio (PDR) and Latency Delay (LD) as compared to default OF design. Residual Energy (RE) combined with ETX (EE) and conjunction with Enhanced timer (EE_En_Timer) design works well for energy consumption. Overhead is very less in RE and ETX design. Conversion time is reduced by almost 50% in an En_Timer design. Higher PDR and low delay values of EC and EC_En_Timer design encourages its use in health monitoring application where reliability is essential. Low energy consumption results of RE, EE and EE_En_Timer designs are comfortable for forest monitoring application, as energy is a crucial aspect. This comparative result outcome will help to fulfill the IoT application requirements.
... The routing metrics and protocols are attractive solutions to keep multimedia applications with acceptable quality level, while optimizing the usage of network resources [5]. In order to maintain a better level of quality, routing metrics have been proposed taking account characteristics of communication paths between end-points, such as number of hops, interference, jitter, and assign a cost to each of these links. ...
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In a near future, wireless mesh networks (WMNs) and multimedia content will be abundant technologies/applications in the Internet. Hence, in order to keep and attract new customers, as well as, reduce operational costs, the development of new quality level control schemes are needed and it is one of the key requirements for the success of next generation wireless multimedia systems. With this goal in mind, this paper presents a new routing metric with focused on estimation error on wireless links, named ETXMULT (Expected Transmission Count for Multimedia Content), to assure high-quality paths on multi-hop wireless networks for multimedia traffic. Simulations were carried out, by using Network Simulator 2 (NS-2), to demonstrate the behavior and benefits of the proposed metric with Optimized Link State Routing (OLSR) routing protocol. The results presented improvements in the distribution of multimedia content compared to the original Expected Transmission Count (ETX) metric, by analyzing well-know QoS and QoE metrics.
... All of these studies have confirmed the unpredictable behavior of radio communications and high fluctuations of data transmission quality over wireless links. According to these observations, link quality estimation is known as a fundamental building block of different network protocols in wireless sensor networks, and various link assessment techniques are designed to improve network performance [15,38]. Although there exist several research works which have introduced various neighbor discovery mechanisms and rich literature on the link quality estimation in wireless networks, still integration of initial neighbor discovery and link quality estimation has a lot of open research challenges [2]. ...
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Network connectivity and link quality information are the fundamental requirements of wireless sensor network protocols to perform their desired functionality. Most of the existing discovery protocols have only focused on the neighbor discovery problem, while a few number of them provide an integrated neighbor search and link estimation. As these protocols require a careful parameter adjustment before network deployment, they cannot provide scalable and accurate network initialization in large-scale dense wireless sensor networks with random topology. Furthermore, performance of these protocols has not entirely been evaluated yet. In this paper, we perform a comprehensive simulation study on the efficiency of employing adaptive protocols compared to the existing nonadaptive protocols for initializing sensor networks with random topology. In this regard, we propose adaptive network initialization protocols which integrate the initial neighbor discovery with link quality estimation process to initialize large-scale dense wireless sensor networks without requiring any parameter adjustment before network deployment. To the best of our knowledge, this work is the first attempt to provide a detailed simulation study on the performance of integrated neighbor discovery and link quality estimation protocols for initializing sensor networks. This study can help system designers to determine the most appropriate approach for different applications.
... Among them we find metrics indicating the distance from the destination measured in hops (hop count) or in physical distance units (measured on physical or virtual coordinates), the packet loss due to congestion or link failures measured as the number of expected transmissions until the packet is successfully transmitted (expected transmissions number -ETX), the remaining energy of a node or of the nodes in a path. Different ways to quantify them exists (as discussed in [10]) with fifteen ways to quantify ETX proposed in [6] and a similar number reported in [7] for energy. ...
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... Simulations show that FEEL protocol achieves longer stability period and throughput. In future, we intend to implement Expected Transmission Count (ETX) link metrics as discussed in [21,22]. [2] Jovanov,E.; ...
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... The ETX of a wireless link is the estimated average number of data and ACK frame transmissions required for the successful transmission of a packet [9]. As we know, the transfer of data can be in both directions. ...
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Sensor nodes are small, low-cost electronic devices that can self-organize into low-power networks and are susceptible to data packet loss, having computational and energy limitations. These devices expand the possibilities in many areas, like agriculture and urban spaces. In this work, we consider an IoT environment for monitoring a coffee plantation in precision agriculture. We investigate the energy consumption under low-power and lossy networks considering three different network topologies and an Internet Engineering Task Force (IETF) standardized Low-power and Lossy Network (LLN) routing protocol, the Routing Protocol for LLNs (RPL). For RPL, each secondary node selects a better parent according to some Objective Functions (OFs). We conducted simulations using Contiki Cooja 3.0, where we considered the Expected Transmission Count (ETX) and hop-count metric (HOP) metrics to evaluate energy consumption for three distinct topologies: tree, circular, and grid. The simulation results show that the circular topology had the best (lowest) energy consumption, being 15% better than the grid topology and 30% against the tree topology. The results help the need to improve the evolution of RPL metrics and motivate the network management of the topology.
... Expected Transmission Count (ETX) is adopted to estimate the frame error rate [13]. ETX metric periodically sends a message among the nodes and returns the message loss to the neighbors. ...
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Peer-to-peer based systems have been widely proposed to provide the Video-on-Demand (VoD) service on the Internet in recent years. With the development of mobile networks, we proposed a suitable VoD system for mobile networks, in which peers are classified into groups and the backbone networks are established so that peers in the same group can share and transmit the streaming videos through the backbone networks. Further, mobile nodes that are not located at the backbone networks can receive the streaming videos through the Wireless Mesh Networks (WMNs). Through our path selection mechanism, peers can route faster and the system will be load-balancing. By considering the influence of the locality to mobile nodes, we delimit the new range of WMNs. In addition, according to the Airtime metric proposed in IEEE 802.11s, the Airtime cost of every mesh loop is calculated and the optimal path thus can be figured out.
... For delay sensitive applications, DYMO in reactive protocols and OLSR in proactive protocols are the plausible choices. During all this evaluation, we come to realize that the most important component of a routing protocol is routing link metric, so, in future we are interested to propose and implement a new ETX-based routing link metric with AODV and OLSR, as discussed in [34]. ...
... The metric we use to select the channel is based on the expected transmission count metric (ETX) [7]. ETX is valuable in wireless environments as it incorporates the effects of lossy links, interference caused by PU activity, and interference among the successive links of a path [13] [8]. ETX optimizes for throughput as it minimizes the expected total number of packet transmissions required to successfully deliver a packet to the ultimate destination. ...
... The main purpose of data collection tree protocols is to enable all the nodes to find at least one path towards a single or multiple network data collection points for data transmission [73,74]. Different metrics (e.g., hopcount and link quality) can be used to construct a spanning tree that includes lowest cost paths [75][76][77][78]. Network nodes calculate the cost of data transmission over different paths towards the network data collection point according to the utilized cost function. ...
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The increasing growth of low-power wireless networks in real-world implementations has intensified the need to develop well-organized key network building blocks. Neighbor discovery, link quality measurement and data collection are among the fundamental building blocks of network initialization process. Over the past decade, network initialization has attracted significant attention from the research community of low-power wireless networks. Accordingly, the general concern of this paper is to survey neighbor discovery, link evaluation and collection tree construction protocols, as well as, research challenges in these research areas. Furthermore, we explore the impacts of these protocols on the functionality of different layers in the network protocol stack. In order to provide a clear view of the state-of-the-art neighbor discovery approaches, this paper also presents a classification of the existing neighbor discovery protocols. Finally, some of the important open issues in developing network initialization protocols are discussed to present new directions for further research.
... All of these studies have confirmed the unpredictable behavior of radio communications and high fluctuations of data transmission quality over wireless links. According to these observations, link quality estimation is known as a fundamental building block of different network protocols in wireless sensor networks, and various link assessment techniques are designed to improve network performance [15,38]. Although there exist several research works which have introduced various neighbor discovery mechanisms and rich literature on the link quality estimation in wireless networks, still integration of initial neighbor discovery and link quality estimation has a lot of open research challenges [2]. ...
... De Couto et al. [3] have designed ETX and observed the effect of this metric in DSDV (Destination-Sequenced Distance-Vector) and DSR (Dynamic Source Routing) and compared its performances with the "classical" hop count metric. Javaid et al. [4] studied ETX and some variant and observed that the most of metrics were designed for Wireless Mesh Networks (WMNs) and use some technics to improve performance such as the channel selection to have less interferences, etc. Liu et al. [5] suggests an improvement of ETX that make it more accurate by the use of a new formula to compute the delivery ratio determined by the ratio of received packets over packets sent during a temporal "sliding" window. This work suggests an interesting improvement about the accuracy of ETX but does not explore the reactivity for events detection (e.g. ...
Conference Paper
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The accuracy and the reactivity of link quality estimations are key concepts in Vehicular Ad-Hoc Network (VANET) applications, since routing metrics are used for routing decisions and neighbourhood information. The Expected Transmission Count(ETX) is the most salient metric used in wireless Ad-hoc and mesh networks that assesses the link quality. The provided estimation varies according to link changes like disruptions and bidirectional links becoming unidirectional. Such changes often occur in Vehicular Ad Hoc Network (VANET) and to be efficient, routing protocols have to face those events. Existing implementations lead to a limited accuracy and cannot be efficient in VANET environment. In this paper we present an algorithm that improves ETX and adapt it to VANET. This improved ETX metric, called F-ETX for Fast-ETX improves significantly ETX reactivity and makes it more accurate. Furthermore, internal computation information is suitable for link stability characterizing. This algorithm has been tested under realistic physical layers and mobility patterns to evaluate its reactivity, accuracy and stability .
... De Couto et al. proposed the ETX metric in [5] and implemented it in DSDV (Destination Sequenced Distance Vector) and DSR (Dynamic Source Routing) to compare its performances with the "classical" hop count metric. Javaid et al. [6] studied ETX and its variants. They observed that most of metrics were designed for Wireless Mesh Networks (WMNs) and use some techniques to improve performances (i.e. the channel selection to have less interferences). ...
... De Couto et al. proposed the ETX metric in [5] and implemented it in DSDV (Destination Sequenced Distance Vector) and DSR (Dynamic Source Routing) to compare its performances with the "classical" hop count metric. Javaid et al. [6] studied ETX and its variants. They observed that most of metrics were designed for Wireless Mesh Networks (WMNs) and use some techniques to improve performances (i.e. the channel selection to have less interferences). ...
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The accuracy and the reactivity of link quality estimators are key concepts in Mobile Ad hoc networks (MANETs) and especially in Vehicular Ad hoc Networks (VANETs), since routing process uses link quality related metrics based on neighbour information for making routing decisions. The Expected Transmission Count (ETX) is the most salient metric that assesses the link quality for wireless ad hoc and mesh networks. Its estimation varies according to the link changes like disruption and bidirectional to unidirectional switching. Such changes occur more often in highly mobile networks like VANETs. In order to be efficient routing protocols have to deal with these events. It has been observed that current implementation of ETX leads to a limited accuracy and cannot be efficient in VANETs. In this paper is presented an algorithm which makes the ETX metric more adapted for VANETs. Our contribution significantly improves the reactivity and the accuracy of the metric. In addition, our metric is not limited to the link quality estimation but also brings a link stability information. This results a new metric called Fast-ETX (F-ETX). This metric has been tested under realistic physical layer and mobility patterns to evaluate its reactivity, accuracy and stability properties.
... Application of routing link matrices on the proposed scheme can be useful in achieving efficient consumption of energy in the network. We aim to introduce multiple QoS parameters [32]. Mobility constraints also help to achieve better network lifetime similar to [33,34]. ...
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In this paper, a novel framework is presented through link and path duration for link availability of paths. Further, we evaluate and analyze our work by varying the number of nodes, pause time and speed in VANETs. We select three routing protocols namely Ad-hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR) and Fish-eye State Routing (FSR). Performance of these protocols is analyzed using Packet Delivery Ratio (PDR), Normalized Routing Overhead (NRO), End-to-End Delay (E2ED), Average Link Duration (ALD) and Average Path Duration (APD) against varying scalability, pause time and speed as performance metrices. We perform these simulations with NS-2 implementing Nakagami radio propagation model. The SUMO simulator is used to generate a random mobility pattern for VANETs. To find link duration and path duration we also use MATLAB. From the extensive simulations, we observe that AODV and DSR outperform better among all three routing protocols.
... Link quality measurements traditionally belong to MAC and PHY layers. Over the years there have been numerous attempts to establish a fast, reliable, and standardized mechanism for link quality assessment based on expected transmission count (ETX) [21,22] and low-level physical indicators like RSSI [23], LQI [24], and DSSS chip errors [25]. Ultimately, none of them became part of the previous IEEE 802. ...
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The Internet of Things (IoT) envisages expanding the current Internet with a huge number of intelligent communicating devices. Wireless sensor networks (WSNs) integrating IoT will rely on a set of the open standards striving to offer scalability and reliability in a variety of operating scenarios and conditions. Standardized protocols will tackle some of the major WSN challenges like energy efficiency, intrinsic impairments of low-power wireless medium, and self-organization. After more then a decade of tremendous standardization efforts, we can finally witness an integral IP-based WSN standardized protocol stack for IoT. Nevertheless, the current state of standards has redundancy issues and can benefit from further improvements. We would like to highlight some of the cross-layer aspects that need to be considered to bring further improvements to the standardized WSN protocol stack for the IoT.
... In the present work, we use Expected Transmission Count (ETX) as the routing metric as it allows for considering the effect of both path length and packet loss. Also it guarantees high throughput, minimum hops and optimizes spectrum usage [25][26][27]. EXT is a link metric which represents the number of transmissions a node has to make for a message to successfully reach its destination. ETX of a link can be computed based on the forward delivery ratio (df ) and reverse delivery ratio (dr) of a link as depicted in equation 1. ...
Conference Paper
The Low power and Lossy Networks (LLNs) form an important segment of the Internet of Things (IoT). IPv6 over Low power Personal Area Networks (6LoWPAN) enables connectivity of constrained non IP-enabled devices to the Internet. The routing protocol used in 6LoWPAN is IPv6 Routing Protocol over Low power and lossy networks (RPL). Though RPL meets all the routing requirements of LLNs, it is prone to several attacks. Among the several RPL attacks, misappropriation attacks are those which disrupt the legitimate path of traffic flow in the lossy network and causes convergence of a large section of traffic towards a particular malicious node. Also, misappropriation attacks can make the LLNs vulnerable to several other security attacks. Hence, it is important to timely detect misappropriation attacks. In this paper, we propose a mechanism to detect misappropriation attacks in IoT LLNs. Our approach makes use of Multilayer Perceptron (MLP) neural network to classifies the network data as normal or as under attack. Our proposed mechanism also identifies the nodes affected by the attack and identifies the attacker node.
... More complex software based link estimation algorithms will tackle the aforementioned issue by using historical and/or cross-layer information to make more intelligent decisions when selecting the best links. ETX[11]based algorithms estimate the number of expected transmissions needed to successfully send a packet to each destination by counting the number of attempts needed in previous transmissions. ETX based algorithms select the path with minimal ETX. ...
Conference Paper
Link estimators are extremely important in dynamic wireless sensor networks for obtaining a good network performance because they drive the decisions made by the routing protocol. Many estimators exist but the quality of their estimation depends on the scenario at hand. In this paper, the impact of the estimator on the network performance is investigated in different networking scenarios. Also the influence of the underlying MAC protocol was evaluated. The evaluation was performed both in simulation and on a real-life testbed. The results clearly show that there is no link estimator that is best in all scenario’s. Another major finding indicates that the results obtained in simulator differ heavily from the testbed results. This illustrates that research findings cannot be solely based on simulation results but also requires real-world experiments. The influence off the underlying MAC protocol is limited on the choice of estimator.
... This begins with the measurements of network and link using parameters such as actual delay and reception ratio. The classic network metric ETX (Expected Transmission Count) [24] calculates the expected number of data transmissions, including retransmissions. According to ETX, routing protocols meet the delivery rate through the retransmission approach. ...
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Abstract Cyber-physical systems (CPSs) connect physical equipment and the information system to realize real-time perception and intelligent control of the equipment. With the rapid development of wireless sensors, wireless sensor networks (WSNs) now play a major role in CPS and have become a focus of research. However, WSNs in CPS face great challenges in ensuring the high reliability and time critical performance of data transmission because of the characteristics of the complex structure and dynamic connectivity. In order to meet the performance requirement of CPS data transmission, a Reliability and Timeliness Guaranteed Opportunistic Routing (RTGOR) protocol is proposed that is based on opportunistic routing and combined with quantified transmission reliability and time guarantees. Our simulation results demonstrate that RTGOR performs better than the state-of-the-art protocol QMOR (QoS-assured Opportunistic Routing Mechanism), in terms of the packet delivery rate and end-to-end delay metrics.
... Future work focuses on estimating the delay, in propagating data from body sensors to the destination node in DARE protocol and also, to minimize link degradation issues in case of mobility in patient's body to enhance network lifetime. Authors in [36], work on routing metrics based on ETX (Expected Transmission Count) which, shows better performance than minimum hop count metric, under the availability of link. In view of this, the plan focus to work on routing link metrics as well. ...
... Therefore, some proposals [12,16,20] present methods that combine metric types to satisfy the needs of the applications. For example, the Hop Count (HC) [9,10] selects the route with the lowest number of hops, while the Expected Transmission Count (ETX) selects the route with the least number of expected transmissions [21][22][23]. ...
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This paper presents the adaptation of a specific metric for the RPL protocol in the objective function MRHOF. Among the functions standardized by IETF, we find OF0, which is based on the minimum hop count, as well as MRHOF, which is based on the Expected Transmission Count (ETX). However, when the network becomes denser or the number of nodes increases, both OF0 and MRHOF introduce long hops, which can generate a bottleneck that restricts the network. The adaptation is proposed to optimize both OFs through a new routing metric. To solve the above problem, the metrics of the minimum number of hops and the ETX are combined by designing a new routing metric called SIGMA-ETX, in which the best route is calculated using the standard deviation of ETX values between each node, as opposed to working with the ETX average along the route. This method ensures a better routing performance in dense sensor networks. The simulations are done through the Cooja simulator, based on the Contiki operating system. The simulations showed that the proposed optimization outperforms at a high margin in both OF0 and MRHOF, in terms of network latency, packet delivery ratio, lifetime, and power consumption.
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Because of its huge scale and restrictions on scope of communication, a Wireless Sensor Network (WSN) generally depends on multi-hop transmissions to transmit a data packet along a succession of storage nodes. It is of key significance to estimate the forwarding nature of multi-hop routes and such data might be used in developing dynamic and economical routing methodologies. Objective: To develop a scheme which eases the determination of Cluster Heads (CH) in a WSN, which inturn would enhances the quality of path management. Analysis: Existing measurements for the most part, concentrate on evaluating the connection link performance among the sensor nodes while ignoring the forwarding abilities inside them. Recent studies demonstrate that the nature of forwarding inside every wireless sensor node is equally essential component that adds to the path quality in data transmission. Methodology: We propose a methodology to reduce the overhead by developing an efficient scheme for selecting a Cluster Head (CH) in each cluster to represent all the other nodes in the cluster. This CH will be responsible for representing the entire Cluster viz., To determine the routing path ,To detect the malicious nodes (Attacker Node) in each cluster, etc., which eventually eases the task of determining the forwarding path, in other words, enhancing the forwarding path quality. Findings/Improvements: A stand-alone application had been developed for this proposed system in Eclispe IDE and the results we obtained has proved that the proposed methodology ,when applied can achieve the required forwarding path quality management in WSN by evaluating both the connection link performance and also the forwarding abilities inside a sensor node.
Presentation
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The list of literature sources presented here covers the following topics from the RPL Framework: 3.1. Performance Analysis and Evaluation (A & E), 3.2. Convergence A & E, 3.3. Objective Function Analysis, 3.4. Routing Metrics Analysis , 3.5. Mobility A & E, 3.6. Security A & E.
Chapter
Security in mobile wireless sensor networks is a big challenge because it adds more complexity to the network in addition to the problems of mobility and the limited sensor node resources. Even with authentication and encryption mechanisms, an attacker can compromise nodes and get all the keying materials. Therefore, an intrusion detection system is necessary to detect and defend against the insider attackers. Currently, there is no intrusion detection system applied to IPv6-based mobile wireless sensor networks. This paper is mainly interested in detecting the selective forwarding and clone attacks because they are considered among the most dangerous attackers. In this work, the authors design, implement, and evaluate a novel intrusion detection system for mobile wireless sensor networks based on IPv6 routing protocol for low power and lossy networks. The new intrusion detection system can be extended to other attacks such as wormhole and sybil attacks. The simulations results show that the detection probability is 100% for selective attackers under some cases.
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In this paper, we propose a new Quality Link Metric (QLM), ``Inverse Expected Transmission Count (InvETX)'' in Optimized Link State Routing (OLSR) protocol. Then we compare performance of three existing QLMs which are based on loss probability measurements; Expected Transmission Count (ETX), Minimum Delay (MD), Minimum Loss (ML) in Static Wireless Multi-hop Networks (SWMhNs). A novel contribution of this paper is enhancement in conventional OLSR to achieve high efficiency in terms of optimized routing load and routing latency. For this purpose, first we present a mathematical framework, and then to validate this frame work, we select three performance parameters to simulate default and enhanced versions of OLSR. Three chosen performance parameters are; throughput, Normalized Routing Load and End-to-End Delay. From simulation results, we conclude that adjusting the frequencies of topological information exchange results in high efficiency.
Conference Paper
In this paper, we propose a new approach for Quality-of-Service routing in wireless ad-hoc networks called r min -routing, with the provision of statistical minimum route reliability as main route selection criterion. Discovery of r min routes is based on a network model with statistical link reliabilities, which are combined into path reliabilities. To achieve specified minimum route reliabilities, we improve the reliability of individual links by well-directed retransmissions, to be applied during the operation of routes. To select among a set of candidate routes, we define and apply route quality criteria concerning network load. We have applied r min -routing in sample topologies, and compare it to other routing approaches.
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In this research we target the routing design in a directional hierarchical airborne network. Such a network has the following 2 main features: (1) Two-level architecture: The high level is a sparse wireless network with long-distance links and high-rate communications. It also has a commander node. The lower level is a high-density network with short-distance low-rate links. (2) Hybrid directional antennas: The network has mixed antennas (multi-/omni-directional antennas). We assume that the high-level nodes are equipped with more expensive, multi-directional (also called multi-beam) antennas, while low-level nodes have inexpensive omni-directional antennas. We propose to use bio-inspired algorithms, called MAN (Moth,Ant, Neuron), to achieve the two-level routing. Particularly we use male moth's light source pursuing pattern to handle the routing issue from any event node to the highly mobile sink among dense nodes, and use the ant's chemical trail maintenance principle to trace the trajectory of commander node in order to deliver low-level data to it with the minimized delay. In addition, inspired by human brain neuron grid architecture, we propose to construct a weighted fence routing topology among multi-beam high-level nodes in order to achieve a high-throughput routing.
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Critical monitoring applications can use wireless sensor networks to transport delay sensitive data. This data may demand bounded delays in order to be considered useful by the receiver. In these cases, an accurate and real-time estimation of the end-to-end delay could be used to anticipate the data usefulness prior to sending it. A novel real-time and end-to-end delay estimation mechanism is proposed in this paper, which considers processing times and two new RPL metrics. Results show that our proposal is more accurate than the ETT-based solution for delay estimation, and it does not significantly degrade the network performance.
Conference Paper
Machine to machine communication has gained increasing importance in the context of Internet of Things (IoT). The existing routing protocols for low-power, lossy networks (LLNs) mainly support multipoint to point or point to multipoint communications and have very limited support for point to point communication. The LOADng routing protocol is a source initiated reactive protocol with support for point to point communication. In this paper, a composite routing metric is proposed to improve the packet delivery ratio and the lifetime of a network using LOADng routing protocol. The results obtained through simulation show that using a composite metric can significantly improve the performance of LOADNg routing protocol for low-power, energy constrained networks with sparse traffic.
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Security in mobile wireless sensor networks is a big challenge because it adds more complexity to the network in addition to the problems of mobility and the limited sensor node resources. Even with authentication and encryption mechanisms, an attacker can compromise nodes and get all the keying materials. Therefore, an intrusion detection system is necessary to detect and defend against the insider attackers. Currently, there is no intrusion detection system applied to IPv6-based mobile wireless sensor networks. This paper is mainly interested in detecting the selective forwarding and clone attacks because they are considered among the most dangerous attackers. In this work, the authors design, implement, and evaluate a novel intrusion detection system for mobile wireless sensor networks based on IPv6 routing protocol for low power and lossy networks. The new intrusion detection system can be extended to other attacks such as wormhole and sybil attacks. The simulations results show that the detection probability is 100% for selective attackers under some cases.
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Recently, Flying Ad-hoc Sensor Networks (FASNETs), which are basically ad hoc networks between Unmanned Aerial Vehicles (UAVs), have been playing a great role in many sensing fields. To further improve the utilization of network resources, researchers offer the possibility of applying Software Defined Networking (SDN) technology to FASNETs, enabling various applications to be supported over the same platform. Since these concurrently executed applications might have diverse Quality of Service (QoS) requirements, it brings new challenges to network management and resource scheduling. In this paper, we propose a novel clustering FASNET architecture with SDN cluster controllers and also a collaborative controller, in order to realize hierarchical management and unified dispatch. Based on our designed architecture, we also propose a centralized traffic-differentiated routing (TDR) executed in each cluster, which aims to guarantee the specific QoS requirements of delay-sensitive and reliability-requisite services. Different weights are assigned to various flows according to their sensitivity to delay and also levels of importance. In particular, we introduce a transmission reliability prediction model to TDR, in which we consider both link availability and node's forwarding ability. Simulation results show our proposed TDR has good performances in terms of end-to-end delay, packet dropping ratio and network throughput.
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In the recent past, we witnessed to a dramatic growth of networks with a huge number of interconnected wireless nodes exchanging large amounts of information. This has brought to the need of ad-hoc, energy-aware protocols suitable for low-power and lossy networks. Among these, Routing Protocol for Low Power and Lossy Networks (RPL) is surely one of the most interesting ones. It chooses the optimal routes from a source to a destination node, based on specific metrics. In this work we present a RPL compliant composite metric that considers both reliability and energy. Its aim is twofold. First, it realizes energy consumption balancing, so that each node tends to consume the same amount of energy of all the others, thus prolonging the overall network lifetime. Second, it takes into account data reliability along the paths, expressed by the well known Expected Transmission Count (ETX). The effectiveness of the proposed metric is confirmed by some interesting simulation results, that strongly encourage a deeper investigation on this issue.
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The physical and logical representation of constrained embedded devices such as sensors and actuators plays a significant role in the Internet revolution to next era which is the Internet of Things (IoT). A Wireless Sensor Network (WSN) comprises of several tiny devices (called nodes) with restricted resources and has a capability of sensing and monitoring a certain environment to collect data and sending it to hop by hop to the root node (Sink) via a routing protocol. The routing strategy in WSNs that is called Low power and Lossy Networks (LLNs) determines the lifetime and quality of the network. The nodes in LLNs characteristics (such as low cost, limited storage, computation, and power) could bring an open challenge that is to find out an optimal routing protocol in wireless sensor networks. The IPv6 based RPL routing protocol for LLNs networks are developed based on a selected Objective Functions (OFs) and then different objective functions are used to evaluate the RPL performance to meet various predefined requirements of home-building automation, industrial control, and urban environment. Based on this, the authors attempt to introduce systematic perspectives in terms of RPL and the main metrics that are used in the LLNs. As a result, it is expected to illustrate the conceptual comparison among the metrics in OF's implementation in RPL. keywords: {Linear programming;Network topology;Routing;Routing protocols;Sensors;Topology;Wireless sensor networks;Internet of things;LLNs;Objective Functions;RPL;Routing metrics},
Conference Paper
High throughput and energy are two important constraints of the Wireless Sensor Networks (WSNs). In this paper, we present the Centrality-based Routing Aware for L2Ns (CRAL)1-Low Drop and Fast Delivery to mitigate these problems. The routing protocols are centrality-based and employ link quality estimators Expected Transmission Count (ETX) and Expected Transmission Time (ETT) to find best paths in wireless links. The suitable combinations of these techniques lead the algorithms to improve the literature results in delivery rate, energy consumption, and time to delivery data packets. CRAL does this by building routing trees with high throughput and maintains low energy consumption. The simulation results show that CRAL is more reliable, efficient in energy consumption, robust, and favoring data fusion than Centrality Tree (CT) and Shortest Paths Tree (SPT).
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With the success of wireless communications, it becomes possible to access the network anywhere at any time without the need for physically connect communicating devices in an infrastructure. The nodes (laptops, smartphones, etc.) can analyze different radio channels to be able to associate with an available wireless network (base station, access point, etc.). An undeniable advantage of wireless technologies is the ability to be mobile while staying connected. However, mobility is difficult to manage because it must be addressed at different layers to be transparent to users. In MANET (Mobile Ad hoc Network) routing protocols use metrics to select the best routes. The metric can reflect the quality of the wireless link and help manage mobility.But a significant delay between the estimate metrics and their inclusion in the routing process makes this approach ineffective.The work of this thesis are interested in proposing new methods for calculating routing metrics to manage the problem of mobility in ad hoc networks. The new metrics should reflect the quality of the link and be sensitive to the mobility simultaneously. We consider the classical metrics, particularly ETX (Expected Transmission Count) and ETT (Expected Transmission Time). We introduce new methods to predict the values of these metrics using prediction algorithms.We use a cross layer approach, which allows the joint use of information from layers 1, 2 and 3. The validation of new methods for calculating routing metrics requires evaluation through a real bench test. So we also implemented new routing metrics in a testbed to assess and compare their performance with classical metrics.
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Routing Protocol for Low-Power and Lossy Networks (RPL) is the Internet Engineering Task Force (IETF) standard for IPv6 routing in Low-power and Lossy Networks (LLNs). By using the Objective Function (OF) and a collection of routing metrics, it can build a Destination Oriented Directed Acyclic Graph (DODAG). There are two kinds of OFs specified by the IETF, Objective Function Zero (OF0) and Minimum Rank with Hysteresis Objective Function (MRHOF) respectively. The former is based on minimum hop count while the latter is based on Expected Transmission Count (ETX) and is more preferable. However, as the network size increases, both MRHOF and OF0 will introduce long single hop, which may become the routing bottleneck that restricts the entire network. In this paper, the problem is solved by optimizing the MRHOF with a new routing metric, the PER-HOP ETX. Instead of working with additive ETX metrics along a route, PER-HOP ETX distributes the ETX value to each node along the route. This method can achieve better routing performance in large-scale sensor network scenario. A detailed mathematical proof is given in the paper, and simulations were carried out based on the Contiki operating system. Experiments showed that PER-HOP ETX, the proposed optimization outperforms OF0 and ETX in terms of network latency, packet delivery ratio and energy consumption when the network scale becomes large.
Conference Paper
In this work, we propose a novel quality link metric; Bandwidth adjusted Inverse ETX (BIETX) for Static Wireless Multi-hop Networks (SWMhNs). The proposed metric considers two path selection parameters into account i.e., packet delivery ratio and link capacity. For computing packet delivery ratios in BIETX, the mechanism of Expected Transmission Count (ETX) is adopted. On the other hand, we take two methods of computing link capacity in BIETX. These methods are based upon the size of pair probes; equal size and different size. We also enhance Optimized Link State Routing (OLSR) protocol while using BIETX. A comparative analysis of proposed metric with equal size and different size pair probe; BIETX-1 and BIETX-2, with two existing quality metrics (ETX and Expected Transmission Time (ETT)) in SWMhNs is also a part of this work. From simulation results, we conclude that BIETX-2 outperforms rest of the metrics because of low routing load in ad-hoc probes, and low routing latencies due to enhancements of routing update frequencies and window size in OLSR.
Chapter
Wireless ad hoc networks are becoming increasingly relevant due to their suitability for Internet-of-Things (IoT) applications. These networks are comprised of devices that communicate directly with each other through the wireless medium. In applications deployed over a large area, each device is unable to directly contact all others, and thus they must cooperate to achieve multi-hop communication. The essential service for this is Routing, which is crucial for most applications and services in multi-hop ad hoc networks. Although many wireless routing protocols have been proposed, no single protocol is deemed the most suitable for all scenarios. Therefore, it is crucial to identify the key differences and similarities between protocols to better compare, combine, or dynamically elect which one to use in different settings and conditions. However, identifying such key similarities and distinctions is challenging due to highly heterogeneous specifications and assumptions. In this paper, we propose a conceptual framework for specifying routing protocols for wireless ad hoc networks, which abstracts their common elements and that can be parameterized to capture the behavior of particular instances of existing protocols. Furthermore, since many wireless ad hoc routing protocols lack systematic experimental evaluation on real networks, we leverage an implementation of our framework to conduct an experimental evaluation of several representative protocols using commodity devices.
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Designing routing metrics is critical for perfor-mance in wireless mesh networks. The unique characteristics of mesh networks, such as static nodes and the shared nature of the wireless medium, invalidate existing solutions from both wired and wireless networks and impose unique requirements on designing routing metrics for mesh networks. In this paper, we focus on identifying these requirements. We first analyze the possible types of routing protocols that can be used and show that proactive hop-by-hop routing protocols are the most appropriate for mesh networks. Then, we examine the requirements for designing routing metrics according to the characteristics of mesh networks and the type of routing protocols used. Finally, we study several existing routing metrics, including hop count, ETX, ETT, WCETT and MIC in terms of their ability to satisfy these requirements. Our simulation results of the performance of these metrics confirm our analysis of these metrics.
Conference Paper
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We address the problem of interference aware routing in multi-radio infrastructure mesh networks wherein each mesh node is equipped with multiple radio interfaces and a subset of nodes serve as Internet gateways. We present a new interference aware routing metric - iAWARE that aids in finding paths that are better in terms of reduced interflow and intra-flow interference. We incorporate this metric and new support for multi-radio networks in the well known AODV routing protocol to design an enhanced AODV-MR routing protocol. We study the performance of our new routing metric by implementing it in our wireless testbed consisting of 12 mesh nodes. We show that iAWARE tracks changes in interfering traffic far better than existing well known link metrics such as ETT and IRU. We also demonstrate that our AODV-MR protocol delivers increased throughput in single radio and two radio mesh networks compared to similar protocol with WCETT and MIC routing metrics. We also show that in the case of two radio mesh networks, our metric achieves good intra-path channel diversity.
Conference Paper
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We propose expected throughput, ETP, a new and improved routing metric for wireless mesh networks. In contrast to previously proposed routing metrics, ETP takes into account the bandwidth sharing mechanism of 802.11 DCF. In this mechanism, contending links with lower nominal bit rate degrade the throughput of faster links. It is evident that this MAC layer interaction impacts the link quality, and subsequently, the route quality. We develop an analytical model to capture the above interaction, and use it to define ETP. ETP is therefore expected to yield more accurate throughput estimations than existing routing metrics. Furthermore, ETP is suitable as a routing metric in multi-rate as well as multi-channel mesh networks
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Routing protocols for wireless ad hoc networks have traditionally focused on finding paths with minimum hop count. However, such paths can include slow or lossy links, leading to poor throughput. A routing algorithm can select better paths by explicitly taking the quality of the wireless links into account. In this paper, we conduct a detailed, empirical evaluation of the performance of three link-quality metrics---ETX, per-hop RTT, and per-hop packet pair---and compare them against minimum hop count. We study these metrics using a DSR-based routing protocol running in a wireless testbed. We find that the ETX metric has the best performance when all nodes are stationary. We also find that the per-hop RTT and per-hop packet-pair metrics perform poorly due to self-interference. Interestingly, the hop-count metric outperforms all of the link-quality metrics in a scenario where the sender is mobile.
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In this paper we propose the enhancement of rout- ing metrics through a more complete view of the physical channel. Using cross-layer optimizations, we develop the Distribution Based Expected Transmission Count (DBETX), which improves the performance of the network in the presence of varying channels. Through observations of the wireless link, the nodes are able to estimate how the wireless link behaves. The proposed metric exploits this estimation to increase routing efficiency. The proposed metric is shown to outperform the conventional ETX metric in the presence of fading. The improvement over ETX increases with the network density because connectivity increases and more routing options become available. Results show a reduction of up to 26% in the Average Number of Transmissions per link and an increase of up to 32% in the end-to-end route availability.
Conference Paper
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We present a new metric for routing in multi-radio, multi-hop wireless networks. We focus on wireless networks with stationary nodes, such as community wireless networks.The goal of the metric is to choose a high-throughput path between a source and a destination. Our metric assigns weights to individual links based on the Expected Transmission Time (ETT) of a packet over the link. The ETT is a function of the loss rate and the bandwidth of the link. The individual link weights are combined into a path metric called Weighted Cumulative ETT (WCETT) that explicitly accounts for the interference among links that use the same channel. The WCETT metric is incorporated into a routing protocol that we call Multi-Radio Link-Quality Source Routing.We studied the performance of our metric by implementing it in a wireless testbed consisting of 23 nodes, each equipped with two 802.11 wireless cards. We find that in a multi-radio environment, our metric significantly outperforms previously-proposed routing metrics by making judicious use of the second radio.
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WMNs are low-cost access networks built on cooperative routing over a backbone composed of stationary wireless routers. WMNs must deal with the highly unstable wireless medium. Therefore, the design of algorithms that consider link quality to choose the best routes are enabling routing metrics and protocols to evolve. In this work, we analyze the state of the art in WMN metrics and propose a taxonomy for WMN routing protocols. Performance measurements for a WMN, deployed using various routing metrics, are presented and corroborate our analysis.
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Load balancing is critical for improving performance in wireless mesh networks. The unique characteristics of mesh networks, such as static nodes and the shared nature of the wireless medium, invalidate existing solutions from both wired and wireless networks and introduce new challenges for providing load balancing. In this paper, we focus on addressing these challenges. We first formulate the objective of load balancing in mesh networks and provide a theoretical solution to optimally achieve this objective. Then, we investigate some existing practical approaches to load balancing in mesh networks and show that none of them sufficiently address these challenges and some may even cause non-optimal paths and forwarding loops. In response, we propose a new path weight function, called MIC, and a novel routing scheme, called LIBRA, to provide interference-aware and multi-channel/multi-radio aware load balancing for mesh networks, while still ensuring routing optimality and loop-freedom. We use extensive simulations to evaluate our scheme by comparing it with both the theoretical optimal solution and existing practical solutions. The results show close-to-optimum performance and indicate that LIBRA is a good candidate for load balancing and routing in wireless mesh networks.
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Wireless technologies, such as IEEE 802.11a, that are used in ad hoc networks provide for multiple non-overlapping channels. Most ad hoc network protocols that are currently available are designed to use a single channel. However, the available network capacity can be increased by using multiple channels. This paper presents new protocols specifically designed to exploit multiple channels. Our protocols simplify the use of multiple channels by using multiple interfaces, although the number of interfaces per host is typically smaller than the number of channels. We propose a link layer protocol to manage multiple channels, and it can be implemented over existing IEEE 802.11 hardware. We also propose a new routing metric for multi-channel multi-interface networks, and the metric is incorporated into an on-demand routing protocol that operates over the link layer protocol. Simulation results demonstrate the effectiveness of the proposed approach in significantly increasing network capacity, by utilizing all the available channels, even when the number of interfaces per host is smaller than the number of channels.
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This paper addresses a set of serious performance problems observed on the CityMesh 50-node 802.11b urban rooftop network that existing routing protocols do not consider. The original CityMesh routing protocol, based on DSR and ETX, delivered median TCP throughput of 20 kilobytes per sec-ond, despite the use of radios that could drive most individ-ual links at much higher rates. The key problems included varying link loss rates, transient bursts of losses on other-wise high-quality links, poor transmit bit-rate selection at the 802.11 level, failure to identify high throughput routes in the multiple bit-rate network, and interference between bulk data traffic and routing protocol updates. The paper describes SrcRR, a new routing protocol that includes solutions to these problems. SrcRR extends ETX by predicting the best 802.11 transmission bit-rate on each link. SrcRR monitors the loss rates of the links in each path it is using, as well as the loss rates of nearby alternate links, to ensure that it continues to use the best route. SrcRR switches to a new route only if the new route's metric is sig-nificantly better than that of the existing route. SrcRR per-forms more aggressive link-level retransmission than 802.11, and does not switch routes in response to modest numbers of lost packets. SrcRR uses its own transmit bit-rate selection algorithm based on medium-term loss rate measurements, replacing the algorithm built into the radio firmware. The paper presents an experimental evaluation of SrcRR on CityMesh. SrcRR improves the median bulk TCP through-put between pairs of nodes from 20 KB/s to 110 KB/s. SrcRR achieves these improvements primarily by reducing the loss rate visible to TCP, which avoids TCP timeouts and consequent idle time, and by improved choice of link transmission bit-rate.
Conference Paper
Routing metrics play a critical role in wireless mesh networks (WMNs). Several metrics have already been proposed but none of them can well meet the specific requirement brought by large-scale multi-radio mesh networks (LSMRMNs). In LSMRMNs, most of traffic has much longer paths than in small scale WMNs. The channel distribution on a long path thus has a significant impact on the route performance. In this paper, we identify such a challenge and study five existing routing metrics. Then we describe a novel interference-aware routing metric, named exclusive expected transmission time (EETT), proposed to select multi-channel routes with the least interference to maximize the end-to-end throughput. Both the theoretic analysis and simulation experiments demonstrate the vantages of EETT.
Conference Paper
We address the problem of energy-efficient reliable wireless communication in the presence of unreliable or lossy wireless link layers in multi-hop wireless networks. Prior work [1] has provided an optimal energy efficient solution to this problem for the case where link layers implement perfect reliability. However, a more common scenario --- a link layer that is not perfectly reliable, was left as an open problem. In this paper we first present two centralized algorithms, BAMER and GAMER, that optimally solve the minimum energy reliable communication problem in presence of unreliable links. Subsequently we present a distributed algorithm, DAMER, that approximates the performance of the centralized algorithm and leads to significant performance improvement over existing single-path or multi-path based techniques.
Conference Paper
This paper analyzes the causes of packet loss in a 38-node urban multi-hop 802.11b network. The patterns and causes of loss are important in the design of routing and error-correction protocols, as well as in network planning.The paper makes the following observations. The distribution of inter-node loss rates is relatively uniform over the whole range of loss rates; there is no clear threshold separating "in range" and "out of range." Most links have relatively stable loss rates from one second to the next, though a small minority have very bursty losses at that time scale. Signal-to-noise ratio and distance have little predictive value for loss rate. The large number of links with intermediate loss rates is probably due to multi-path fading rather than attenuation or interference.The phenomena discussed here are all well-known. The contributions of this paper are an understanding of their relative importance, of how they interact, and of the implications for MAC and routing protocol design.
Conference Paper
The geographic routing is an ideal approach to realize pointto-point routing in wireless sensor networks because packets can be delivered by only maintaining a small set of neighbors' physical positions. The geographic routing assumes that a packet can be moved closer to the destination in the network topology if it is moved geographically closer to the destination in the physical space. This assumption, however, only holds in an ideal model where uniformly distributed nodes communicate with neighbors through wireless channels with perfect reception. Because this model oversimplifies the spatial complexity of a wireless sensor network, the geographic routing may often lead a packet to the local minimum or low quality route. Unlike the geographic forwarding, the ETX-embedding proposed in this paper can accurately encode both a network's topological structure and channel quality to small size nodes' virtual coordinates, which makes it possible for greedy forwarding to guide a packet along an optimal routing path. Our performance evaluation based on both the MICA2 sensor platform and TOSSIM simulator shows that the greedy forwarding based on ETX-embedding outperforms previous geographic routing approaches.
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An ad hoc wireless network is an autonomous self- organizing system of mobile nodes connected by wireless links where nodes not in direct range communicate via intermediate nodes. Modern wireless devices, such as those that implement the 802.11b standard, utilize multiple transmission rates in order to accommodate a wide range of channel conditions. We provide a general theoretical model of the attainable throughput in multi- rate ad hoc wireless networks. This model is derived from a de- tailed analysis of the physical and medium access control layers.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004. Vita. Includes bibliographical references (leaves 111-118). This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. The expected transmission count (ETX) metric is a new route metric for finding high-throughput paths in multi-hop wireless networks. The ETX of a path is the expected total number of packet transmissions (including retransmissions) required to successfully deliver a packet along that path. For practical networks, paths with the minimum ETX have the highest throughput. The ETX metric incorporates the effects of link loss ratios, asymmetry in the loss ratios between the two directions of each link, and interference among the successive links of a path. Busy networks that use the ETX route metric will also maximize total network throughput. We describe the design and implementation of ETX as a metric for the DSDV and DSR routing protocols, as well as modifications to DSDV and DSR which make them work well with ETX. Measurements taken from a 29-node 802.11b test-bed show that using ETX improves performance significantly over the widely-used minimum hop-count metric. For long paths the throughput increase is often a factor of two or more, suggesting that ETX will become more useful as networks grow larger and paths become longer. We also present a simple model for predicting how packet delivery ratio varies with packet size, and detailed measurements which characterize the test-bed's distribution of link delivery ratios and route throughputs. by Douglas S.J. Couto. Ph.D.
Conference Paper
We present a new metric, Expected Data Rate (EDR), for accurately finding high-throughput paths in multi-hop ad hoc wireless networks. Our metric is based upon a new model for transmission interference which is a critical factor in determining path throughput. We construct a realistic and practical transmission interference model by (1) determining transmission contention degree of each link as a function of the wireless link loss, (2) quantifying the impact of the wireless link loss on medium access backoff, and (3) considering possible concurrent transmissions when two links do not interfere with each other. Our transmission interference model also takes the non-optimality of IEEE 802.11 medium access scheduling into account. Using extensive ns-2 simulations of IEEE 802.11 ad hoc networks, we find that EDR can accurately determine the achievable data rates of ad hoc paths, thereby significantly outperforming the other existing metrics.
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This paper considers the problem of selecting good paths in a wireless mesh network. It is well-known that picking the path with the smallest number of hops between two nodes often leads to poor performance, because such paths tend to use links that could have marginal quality. As a result, quality-aware routing metrics are desired for networks that are built solely from wireless radios. Previous work has developed metrics (such as ETX) that work well when wireless channel conditions are relatively static (DeCouto , 2003), but typical wireless channels experience variations at many time-scales. For example, channels may have low average packet loss ratios, but with high variability, implying that metrics that use the mean loss ratio will perform poorly. In this paper, we describe two new metrics, called modified expected number of transmissions (mETX) and effective number of transmissions (ENT) that work well under a wide variety of channel conditions. In addition to analyzing and evaluating the performance of these metrics, we provide a unified geometric interpretation for wireless quality-aware routing metrics. Empirical observations of a real-world wireless mesh network suggest that mETX and ENT could achieve a 50% reduction in the average packet loss rate compared with ETX