25,259 research outputs found
A Cross-Layer Design Based on Geographic Information for Cooperative Wireless Networks
Most of geographic routing approaches in wireless ad hoc and sensor networks
do not take into consideration the medium access control (MAC) and physical
layers when designing a routing protocol. In this paper, we focus on a
cross-layer framework design that exploits the synergies between network, MAC,
and physical layers. In the proposed CoopGeo, we use a beaconless forwarding
scheme where the next hop is selected through a contention process based on the
geographic position of nodes. We optimize this Network-MAC layer interaction
using a cooperative relaying technique with a relay selection scheme also based
on geographic information in order to improve the system performance in terms
of reliability.Comment: in 2010 IEEE 71st Vehicular Technology Conference, 201
Performance Evaluation of a Helper Initiated Distributed Cooperative Medium Access Control Protocol for Wireless Networks
Cross layer cooperative protocol which exploits the benefits of physical layer cooperative communication, is one of the widely recognized MAC layer protocol design strategies for future wireless networks. This paper presents performance analysis of a cooperative mac and these performance parameters are compared those of the legacy IEEE 802.11 DCF MAC. Appropriate relay station selection is the main hurdle in designing efficient cooperative MAC protocol for wireless networks. This cooperative mac demonstrated that intermediate relay nodes themselves can initiate cooperation for relaying data frame to the receiver on behalf of the sender. This procedure makes the selection process of a “helper node” more distributed in nature as well as it contributes to increase throughput of a wireless network by reducing the overheads that are usually incurred in the helper selection process. It has been shown by thorough analytical analysis that the proposed cooperative MAC protocol offers higher throughput and lower frame transmission delay in both ideal and error prone wireless environment. These performance metrics are also evaluated while the wireless nodes are mobile as well
Performance Evaluation of a Helper Initiated Distributed Cooperative Medium Access Control Protocol for Wireless Networks
Cross layer cooperative protocol which exploits the benefits of physical layer cooperative communication, is one of the widely recognized MAC layer protocol design strategies for future wireless networks. This paper presents performance analysis of a cooperative mac and these performance parameters are compared those of the legacy IEEE 802.11 DCF MAC. Appropriate relay station selection is the main hurdle in designing efficient cooperative MAC protocol for wireless networks. This cooperative mac demonstrated that intermediate relay nodes themselves can initiate cooperation for relaying data frame to the receiver on behalf of the sender. This procedure makes the selection process of a “helper node” more distributed in nature as well as it contributes to increase throughput of a wireless network by reducing the overheads that are usually incurred in the helper selection process. It has been shown by thorough analytical analysis that the proposed cooperative MAC protocol offers higher throughput and lower frame transmission delay in both ideal and error prone wireless environment. These performance metrics are also evaluated while the wireless nodes are mobile as well
Cooperative Medium Access Mechanisms and Service-oriented Routing in Multi-hop Wireless Networks
Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 2011Multi-hop wireless networks have been regarded as a promising path towards future
wireless communication landscape. In the past decade, most related work has been
performed in the context of mobile ad hoc networks. In very recent years, however,
much effort has been shifted to more static networks such as wireless mesh networks
and wireless sensor networks. While significant progress has been achieved through
these years, both theoretically and experimentally, challenges still exist in various
aspects of these networks. For instance, how to use multi-hop networks as a means
for providing broadband Internet services with reliability and balanced load remains
as a challenging task. As the number of end-users is increasing rapidly and more
and more users are enjoying multimedia services, how to provide Quality of Service
(QoS) with user satisfaction in such networks remains also as a hot topic.
Meanwhile, another direction which has recently attracted lots of efforts in the
international research community is the introduction of cooperative communications.
Cooperative communications based on relaying nodes are capable of improving
network performance in terms of increased spectral and power efficiency, extended
network coverage, balanced QoS, infrastructure-less deployment, etc. Cooperation
may happen at different communication layers, at the physical layer where
the received signal is retransmitted and at the MAC and routing layers where a
packet is forwarded to the next hop in a coordinated manner towards the destination,
respectively. However, without joint consideration and design of physical
layer, MAC layer and network layer, the benefit of cooperative communication cannot
be exploited to the maximum extent. In addition, how to extend one-hop cooperative
communication into multi-hop wireless network scenarios remains as an
almost un-chartered research frontier.
In this dissertation, we enhance the state of the art technologies in the field of
multi-hop wireless networks from a layered perspective. While efficient scheduling
mechanisms are proposed at the MAC layer, elaborate routing protocols are devised
at the network layer. More specifically, by taking into account of cross layer design
we cope with network congestion problems in wireless mesh networks mainly at the
network layer. In order to further improve the performance of cooperative wireless
networks, we propose a contention-based cooperative MAC protocol in the presence
of multiple relay nodes. Since a large majority of existing cooperative MAC
protocols are designed based on widely-used IEEE 802.11 MAC protocol which
exhibits inherent design constraint when applied in multi-hop wireless networks, it
is imperative to develop a novel cooperative MAC protocol which is appropriate
for multi-hop network scenarios. Next, we propose a TDMA-based MAC protocol supporting cooperative communications in static multi-hop wireless networks. Furthermore,
a cooperative lifetime maximization MAC protocol is proposed to cope
with the energy hole problem in wireless sensor networks
Medium Access Control and Network Coding for Wireless Information Flows
This dissertation addresses the intertwined problems of medium access control (MAC) and network coding in ad hoc wireless networks. The emerging wireless network applications introduce new challenges that go beyond the classical understanding of wireline networks based on layered architecture and cooperation. Wireless networks involve strong interactions between MAC and network layers that need to be jointly specified in a cross-layer design framework with cooperative and non-cooperative users.
For multi-hop wireless networks, we first rediscover the value of scheduled access at MAC layer through a detailed foray into the questions of throughput and energy consumption. We propose a distributed time-division mechanism to activate dynamic transmitter-receiver assignments and eliminate interference at non-intended receivers for throughput and energy-efficient resource allocation based on stable operation with arbitrary single-receiver MAC protocols.
In addition to full cooperation, we consider competitive operation of selfish users with individual performance objectives of throughput, energy and delay. We follow a game-theoretic approach to evaluate the non-cooperative equilibrium strategies at MAC layer and discuss the coupling with physical layer through power and rate control. As a cross-layer extension to multi-hop operation, we analyze the non-cooperative operation of joint MAC and routing, and introduce cooperation stimulation mechanisms for packet forwarding. We also study the impact of malicious transmitters through a game formulation of denial of service attacks in random access and power-controlled MAC.
As a new networking paradigm, network coding extends routing by allowing intermediate transmitters to code over the received packets. We introduce the adaptation of network coding to wireless environment in conjunction with MAC. We address new research problems that arise when network coding is cast in a cross-layer optimization framework with stable operation. We specify the maximum throughput and stability regions, and show the necessity of joint design of MAC and network coding for throughput and energy-efficient operation of cooperative or competitive users. Finally, we discuss the benefits of network coding for throughput stability in single-hop multicast communication over erasure channels. Deterministic and random coding schemes are introduced to optimize the stable throughput properties. The results extend our understanding of fundamental communication limits and trade-offs in wireless networks
Cooperative Communications inWireless Local Area Networks: MAC Protocol Design and Multi-layer Solutions
This dissertation addresses cooperative communications and proposes multi-layer solu-
tions for wireless local area networks, focusing on cooperative MAC design. The coop-
erative MAC design starts from CSMA/CA based wireless networks. Three key issues
of cooperation from the MAC layer are dealt with: i.e., when to cooperate (opportunistic
cooperation), whom to cooperate with (relay selection), and how to protect cooperative
transmissions (message procedure design). In addition, a cooperative MAC protocol that
addresses these three issues is proposed. The relay selection scheme is further optimized
in a clustered network to solve the problem of high collision probability in a dense
network. The performance of the proposed schemes is evaluated in terms of through-
put, packet delivery rate and energy efficiency. Furthermore, the proposed protocol is
verified through formal model checking using SPIN. Moreover, a cooperative code allo-
cation scheme is proposed targeting at a clustered network where multiple relay nodes
can transmit simultaneously. The cooperative communication design is then extended to
the routing layer through cross layer routing metrics. Another part of the work aims at
enabling concurrent transmissions using cooperative carrier sensing to improve the per-
formance in a WLAN network with multiple access points sharing the same channel
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Cross-layer design for OFDMA wireless networks with finite queue length based on game theory
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.In next generation wireless networks such as 4G- LTE and WiMax, the demand for high data rates, the scarcity of wireless resources and the time varying channel conditions has led to the adoption of more sophisticated and robust techniques in PHY such as orthogonal frequency division multiplexing (OFDM) and the corresponding access technique known as orthogonal frequency division multiplexing access (OFDMA). Cross-layer schedulers have been developed in order to describe the procedure of resource allocation in OFDMA wireless networks. The resource allocation in OFDMA wireless networks has received great attention in research, by proposing many different ways for frequency diversity exploitation and system’s optimization. Many cross-layer proposals for dynamic resource allocation have been investigated in literature approaching the optimization problem from different viewpoints i.e. maximizing total data rate, minimizing total transmit power, satisfying minimum users’ requirements or providing fairness amongst users. The design of a cross-layer scheduler for OFDMA wireless networks is the topic of this research. The scheduler utilizes game theory in order to make decisions for subcarrier and power allocation to the users with the main concern being to maintain fairness as well as to maximize overall system’s performance. A very well known theorem in cooperative game theory, the Nash Bargaining Solution (NBS), is employed and solved in a close form way, resulting in a Pareto optimal solution. Two different cases are proposed. The first one is the symmetric NBS (S-NBS) where all users have the same weight and therefore all users have the same opportunity for resources and the second one, is the asymmetric NBS (A-NBS), where users have different weights, hence different priorities where the scheduler favours users with higher priorities at expense of lower priority users. As MAC layer is vital for cross-layer, the scheduler is combined with a queuing model based on Markov chain in order to describe more realistically the incoming procedure from the higher layers
Efficient Power Allocation Schemes for Hybrid Decode-Amplify-Forward Relay Based Wireless Cooperative Network
Cooperative communication in various wireless domains, such as cellular networks, sensor networks and wireless ad hoc networks, has gained significant interest recently. In cooperative network, relays between the source and the destination, form a virtual MIMO that creates spatial diversity at the destination, which overcomes the fading effect of wireless channels. Such relay assisted schemes have potential to increase the channel capacity and network coverage. Most current research on cooperative communication are focused broadly on efficient protocol design and analysis, resource allocation, relay selection and cross layer optimization. The first part of this research aims at introducing hybrid decode-amplify-forward (HDAF) relaying in a distributed Alamouti coded cooperative network. Performance of such adaptive relaying scheme in terms of symbol error rate (SER), outage probability and average channel capacity is derived theoretically and verified through simulation based study. This work is further extended to a generalized multi HDAF relaying cooperative frame work. Various efficient power allocation schemes such as maximized channel capacity based, minimized SER based and total power minimization based are proposed and their superiority in performance over the existing equal power allocation scheme is demonstrated in the simulation results. Due to the broadcast nature of wireless transmission, information privacy in wireless networks becomes a critical issue. In the context of physical layer security, the role of multi HDAF relaying based cooperative model with control jamming and multiple eavesdroppers is explored in the second part of the research. Performance evaluation parameters such as secrecy rate, secrecy outage and intercept probability are derived theoretically. Further the importance of the proposed power allocation schemes in enhancing the secrecy performance of the network in the presence of multiple eavesdroppers is studied in detail through simulation based study and analysis. For all the proposed power allocation schemes in this research, the optimization problems are defined under total power constraint and are solved using Lagrange multiplier method and also evolutionary algorithms such as Differential evolution and Invasive Weed Optimization are employed. Monte Carlo simulation based study is adopted throughout the research. It is concluded that HDAF relaying based wireless cooperative network with optimal power allocation schemes offers improved and reliable performance compared to conventional amplify forward and decode forward relaying schemes. Above research contributions will be applicable for future generation wireless cooperative networks
Cross-Layer design and analysis of cooperative wireless networks relying on efficient coding techniques
2011/2012This thesis work aims at analysing the performance of efficient cooperative techniques and of smart antenna aided solutions in the context of wireless networks. Particularly, original contributions include a performance analysis of distributed coding techniques for the physical layer of communication systems, the design of practical efficient coding schemes that approach the analytic limiting bound, the cross-layer design of cooperative medium access control systems that incorporate and benefit from advanced physical layer techniques, the study of the performance of such solutions under realistic network assumptions, and, finally the design of access protocols where nodes are equipped with smart antenna systems.XXV Ciclo198
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