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ABSTRACT: Various algorithms have recently been proposed to enhance the Quality of Service (QoS) in Wireless Mesh Networks (WMNs). In this respect, we investigate joint Call Admission Control (CAC) and routing in order to provide quality of service (QoS) in wireless mesh networks. Joint association of each mesh client with a mesh access point and multi-hop backhaul routing to the Gateway, determine the availability of resources as to admit or reject a flow.We formulate a joint optimization problem, which maximizes the total revenue from all the carried connections in the network while taking into account the bandwidth constraints of access and backhaul links. In this regard, firstly we derive an optimal pricing policy that considers the complexity of the problem and the connection dropping probability. Then a CAC algorithm is presented using the pricing model. Due to its complexity, the proposed problem cannot be dealt with using the exact methods; therefore a sub-optimal solution is presented through incorporating the meta-heuristic search algorithm i.e batch based simulated annealing to the CAC algorithm.
Communications (ICC), 2011 IEEE International Conference on; 07/2011
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ABSTRACT: Abstract-In this paper, we propose a dynamic OFDMA based subcarrier/power allocation scheme, which aims to balance the aggregate rate and the achieved TCP throughput of competing TCP flows. The proposed allocation utilizes the theoretical TCP throughput which can be accomplished in the end-to-end path. In doing so, the TCP aware scheme attempts to minimize the gap between the allocated rate and the theoretical upper bound under the system constraints. Such a technique can be of significant importance since due to its popularity, TCP is commonly used for streaming video or other ultimedia applications. Numerical investigations reveal that the proposed approach, provides more balance towards the TCP throughput, and under some considerations significantly increase the fairness among competing TCP flows over end-to-end paths of different characteristics. In addition to that, it also manages to avoid starvation of TCP flows with poor channel conditions.
Communications (ICC), 2010 IEEE International Conference on; 06/2010
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ABSTRACT: This paper presents an evaluation of IP-based gateway discovery protocols for the interconnection of ad hoc networks to the Internet. There are three proposed internet discovery approaches: reactive, proactive and hybrid. This paper first compares these protocols performances with respect to different frequency of gateway advertisement considering random waypoint mobility model. The main contribution of this work is the study of the effect of applying realistic mobility models which has not been investigated so far in the related published work. Our results investigate the high impact of selected mobility models on the performance analysis of the discovery protocols.
Innovations in Information Technology, 2009. IIT '09. International Conference on; 01/2010
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ABSTRACT: In this paper, we propose a dynamic OFDMA based subcarrier/power allocation which aims to protect the newly established TCP connections. The proposed allocation utilizes an estimation of the current congestion window of TCP connections to allocate resources so that vulnerable flows with small congestion windows avoid entering packet recovery via retransmission time out. In addition, for the long-lived TCP flows, the theoretical TCP throughput which can be accomplished in their end-to-end path is used as their desired achievable data rate on wireless link. Such a technique can be of significant importance since due to its popularity, TCP is commonly used over the broadband wireless networks.
GLOBECOM Workshops, 2009 IEEE; 01/2010
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ABSTRACT: Various cross-layer optimizations have been recently proposed to improve the performance of TCP in wireless networks. In this paper, we propose a dynamic OFDMA based subcarrier/power allocation which aims to constrain the achievable rate on each flow proportionally to the TCP throughput of the corresponding flow. Numerical investigations reveal that the proposed approach significantly increases fairness among TCP flows operating over end-to-end paths of different characteristics.
Cross Layer Design, 2009. IWCLD '09. Second International Workshop on; 07/2009
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ABSTRACT: A significant body of recent research has analyzed the problematic behavior of TCP over wireless links, and a plethora of modifications to TCP have been proposed in order to increase its performance in such contexts. Two schools of thought have emerged: the first proposes changes to the end-to- end protocol, while the second explores the potential to enhance lower layers as a means to improve the end-to-end performance of TCP. This paper focuses on the latter, and in contrast to most research in this area, which thus-far has concentrated on a single TCP flavor, examines the case where different TCP flavors are competing over a wireless link. To this end, we present and assess a cross-layer solution that involves the adaptation of lower layer characteristics (i.e., the coding rate) based on the detected TCP flavor, in order to maximize the fairness among TCP flows. Through extensive numerical investigations, we show that the proposed scheme considerably improves the fairness over wireless links among different TCP flavors. Our approach also has a minimal effect on the aggregate throughput of the TCP flows, and in cases where the packet error rate is very low, has a small positive effect on throughput.
Global Telecommunications Conference, 2008. IEEE GLOBECOM 2008. IEEE; 01/2009
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ABSTRACT: A range of flavors of TCP are already in existence, and further flavors are being introduced in order to, for example, cope with the packet loss characteristics of wireless links. Moreover, the proliferation new wireless standards and the relative performance differences among them have been mushrooming in recent years. Given the increasingly heterogeneous nature of the Internet, mechanisms do not usually exist for a server to specifically select an appropriate TCP flavor for each individual download. In this paper, we therefore present and assess a cross-layer solution for a node (e.g. a base-station) to quickly adapt lower-layer characteristics (the coding rate and local ARQ retransmissions threshold) based on the detected TCP flavor, in order to optimize the end-to-end performance of the download for that utilized flavor. We demonstrate that the proposed scheme has considerable potential to improve the overall download throughput, while placing no burden on the server and requiring no changes to existing TCP implementations.
Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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ABSTRACT: In mobile communication environments, traditional routing protocols designed for static wireless sensor networks may fail to deliver data timely. The aim of this work is to identify improvements that can be obtained considering mobility and to recognize its research challenges. We briefly describe different levels of mobility in wireless sensor networks (WSNs) and highlight the efficiency of routing in the presence of the mobility.
Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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ABSTRACT: Mobility has introduced a new dimension to the wireless research areas such as IP mobility management protocols and wireless ad hoc networks. In this paper we take a closer look at the issues related to the mobility in wireless sensor networks (WSNs). The aim of this work is to identify improvements that can be obtained considering mobility, recognize its research challenges. We describe different levels of mobility in WSNs and highlight the effect of the mobility on the performance of WSN protocols.
Communications, 2008 24th Biennial Symposium on; 07/2008
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ABSTRACT: Aiming to generate ultra wideband (UWB) pulses based on wavelet packets, four different circuits are proposed. It has been shown that the wavelet packets are quasi-orthogonal and have almost identical time duration, and therefore appear to be valuable candidates for UWB pulse shape modulation systems. However, as with any technology, circuitry is an important challenge to solve before a theoretical application can live up to its full potential. The four proposed circuits are based on different interpretations of the equation defining the wavelet packets and their performance is investigated by computer simulation. The research also illustrates the characteristics and the consequent implementation advantages or issues afferent to each circuit.
IET Communications 06/2008; · 0.83 Impact Factor
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ABSTRACT: In unreliable communication environments, traditional routing protocols designed for static wireless sensor networks may fail to deliver data timely since link/node failures can be found out only after trying multiple transmissions. The main goal of the proposed protocol is to find more stable paths and to control the flooding overhead which will lead to higher level of scalability. This mechanism considers link stability for the route selection, which makes routing data more reliable and decreases the probability of retransmission, thus saves the energy and prolongs the lifetime of the whole network. In this work, we propose a cross-layer solution which utilises MAC layer information to improve routing mechanisms reliability and scalability in network layer.
Intelligent Sensors, Sensor Networks and Information, 2007. ISSNIP 2007. 3rd International Conference on; 01/2008
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ABSTRACT: The rise in the number of mobile wireless devices accessing IP based communication networks has fuelled the need for efficient mobility support for seamless communication. As a consequence a profusion of mobility protocols were proposed. The mobility agent based family of protocols have risen in popularity due to the simplicity in implementing them compared to per host based protocols. The mobility agents located within wireless access networks hide the movement of the mobile nodes by acting as an anchor point through which all the packets traverses to and from the mobile node. The presence of these mobility agents will result in bottlenecks of high congestion within the access network. This paper provides a formal definition to study this effect of mobility agents on wireless access networks. Using maximum concurrent flow problem we model the access network as a multicommodity flow problem and study the throughput of the network with and without the presence of the mobility agents. From the results it can be confidently concluded that by implementing local mobility solutions based on agents, the wireless access network capacity is reduced and the number and location of the agents within the access network have direct impact on the loss.
Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE; 12/2007
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ABSTRACT: The problem of multi-rate power-controlled collision-free scheduling in spatial time division multiple access (STDMA) wireless mesh networks is formulated as a mathematical program utilising cross layer information. As these mixed integer linear programs are intractable (NP-hard problems), optimal collision-free schedules can be found only for topologies consisting of a few nodes. To this end, approximation algorithms that are based on linear programming relaxation and randomised rounding are studied. The proposed framework, which aims to maximise the spatial timeslot reuse under predefined signal-to-interference noise ratio thresholds, is suitable for providing centralised scheduling in the mesh mode of the IEEE 802.16 standard. Performance aspects of the approximation algorithms under different scenarios are investigated.
IET Communications 11/2007; · 0.83 Impact Factor
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ABSTRACT: This paper focuses on the problem mobile terminals face when different protocols operate for providing the same service between visited access networks. Examples of such services are mobility management and QoS signaling. This plethora of protocols can restrict a mobile terminal from using the offered service since it might not be equipped with the appropriate software. This problem can be solved with the use of software reconfiguration. We present a framework for constructing mobile terminal architectures capable of dynamically reconfiguring between protocols that offer the same service. Then we employ the framework to construct two architectures; one capable of adapting to the offered mobility protocol and one capable of adapting to the offered QoS signaling protocol. Finally, we present an implementation of the emerged architectures and estimate through experiments their reconfiguration time.
Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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ABSTRACT: This paper proposes a positioning routing algorithm for UWB ad hoc networks. The algorithm is deployed in two main scenarios: Multi-Coordinate System (MCS) and Unique Coordinate System (UCS). A Packet Forwarding Zone (PFZ) is proposed to investigate the performance where a limited forwarding region is used. New ideas have been included in the routing algorithm, such as the use of the Davidon-Fletcher-Powell (DFP) algorithm to estimate the position of the locally available beacon nodes, and the Reference Group (RG) concept as formed by suitable nodes with the Reference Group Master (RGM) chosen as elected by the nodes in the RG. The RG group characteristics particularly apply in the UCS case. In addition, the performance of Direct Method (DM) and DFP position estimation algorithms are also analyzed.
Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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ABSTRACT: In this paper, the design issues of a coverage-based CRRM strategy are studied to support voice services in a heterogeneous UMTS/GSM environment which distribute the traffic load by controlling the effective UMTS coverage through a predefined pathloss threshold. Comparing with the conventional Load Balancing strategy, the proposed coverage-based CRRM gives a better performance in terms of voice capacity at the expense of extra inter-system handovers. The effects of compress mode operation and mobility on system performance and pathloss threshold selection are also studied in details to refine the CRRM.
Communications and Networking in China, 2007. CHINACOM '07. Second International Conference on; 09/2007
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ABSTRACT: Mobile ad hoc networks (MANETs) are unpredictable by nature. Providing any kind of reliability for quality of service (QoS) in such networks is challenging. Quantifying available resources accurately, avoiding interference with ongoing QoS traffic and adapting to QoS violations caused by nodes' mobility are the main concerns for the design of an efficient admission control protocol in MANETs. Adaptive admission control (AAC), a novel admission control protocol which uses robust and accurate resource estimation and prediction techniques for relevant admission decisions has been proposed. Furthermore, AAC uses statistical QoS provision to counteract the QoS threatening mobility. Through simulations, we show that our proposed scheme outperforms existing approaches in terms of correctness and overall performance.
IET Communications 09/2007; · 0.83 Impact Factor
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ABSTRACT: Industry reactions to major shifts such as mobile broadcast convergence are typically a mixture of opportunities and threats. Both the mobile and the broadcast industries acknowledge the role that convergence will play in their commercial futures, but both would prefer to achieve convergence "on their own patch." For this reason, the most appealing solution to fulfil the contrasting requirements from the different players is represented by interworking between these networks rather than integration. This approach avoids integration, thereby minimizing the changes required in each network and ensuring each network remains an autonomous, independently managed entity. The Internet protocol (IP) is chosen as the "glue" between these heterogeneous networks, providing the generic interworking platform. The main reason behind this choice is that IP was designed as an "interworking protocol" to connect multiple, physically-different networks in such a way as to remain independent of the underlying transport mechanisms used. This article concentrates on the confirm connectivity architecture definition of the interworking model between WLAN, 3G, and DVB. Broadcast networks are uni-directional in nature. When a user wants to receive a service over a broadcast network, there is no way to know whether the broadcast interface of the terminal is configured correctly. In this article we describe a method to automatically configure and test, without user intervention, that the DVB interface of the terminal can receive datagrams from the broadcast network. Furthermore, an optimization method to reduce the total number of confirm connectivity messages (CCMs) sent by the multimode terminals is introduced with simulation results to validate and prove its effectiveness
IEEE Network 04/2007; · 2.24 Impact Factor
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ABSTRACT: Media Independent Handover (MIH) is a technique proposed by the emerging IEEE 802.21 standard that provides solutions for seamless handover across heterogeneous networks. The IEEE standard provides link layer intelligence information to upper layer to optimize handover between networks of the same type as well as handover between different network types. Session Initiation Protocol (SIP) is becoming the leading protocol for multimedia call control in IP networks and is expected to be widely deployed in the near future. The existing SIP infrastructures and signalling could be optimized to provide a good solution for mobility support. In this paper we introduce the concept of MIH and propose a solution for vertical handover of a multimedia session based on SIP with the triggers being provided by MIH for efficient terminal mobility management in a SIP environment.
Vehicular Technology Conference, 2006. VTC-2006 Fall. 2006 IEEE 64th; 10/2006
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ABSTRACT: This paper presents the design and evaluation of a reconfigurable mobile terminal focusing on IP mobility protocols. The presented terminal architecture is capable of dynamically modifying its operation so as to employ the mobility services offered from the visited access networks. The fundamental concept in the architecture is that mobility protocols terminal operation can be modeled with a certain group of functional abstractions. As a consequence, only a few particular functional parts of the architecture need to be modified so as to implement a new mobility protocol. Evaluation results show that the terminal performance complies with the expected behavior and, further, that the reconfiguration process is accomplished within a few milliseconds.
Vehicular Technology Conference, 2006. VTC-2006 Fall. 2006 IEEE 64th; 10/2006
