Voice Call Capacity Over Wireless Mesh Networks

The goal of this thesis is to understand the voice call carrying capacity of an IEEE 802.11b/e based ad hoc network. We begin with the modelling of conversational speech and define a six state semi-Markov voice model based on ITU-T P59 recommendation. We perform a theoretical analysis of the voice model and compare it with results obtained via simulations. Using a Java based IEEE 802.11 medium access layer simulator, we determine the upper-bound for the number of voice calls carried by an ad hoc network. We use a linear topology with the ideal carrier sensing range and evaluate the number of calls carried using packet loss and packet delay as metrics. We observe that, for one, two, three and four hop, 5.5 Mbps IEEE 802.11 wireless links have an upper-bound of eight, six, five, and three voice calls respectively. We then consider a carrier sensing range and a path loss model and compare them with the ideal case. We observe, after considering a carrier sensing range with path loss model, there is a reduction in the number of calls carried by the linear networks. One, two, three and four hop 5.5 Mbps IEEE 802.11 wireless links support eight, five, four, and two voice calls respectively, when a carrier sensing range and a path loss model is considered. We also find that by adopting packet dropping policies at the nodes, we improve the call carrying capacity and quality of service on the network. In our simulations of a two hop network in path loss conditions, we find that, by adopting a time delay based packet dropping policy at the nodes, the number of calls supported simultaneously increased from five to six. In a four hop linear network we find that by total packet loss is reduced by 20%, adopting a random packet dropping policy and by 50% adopting a time delay based packet dropping policy. Although there is no change in number of calls supported, load on the network is reduced

무선 랜 매체접근제어 (MAC) 효율화 기법

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2017. 2. 이광복.In this dissertation, we develop medium access control (MAC) efficiency improvement schemes for IEEE 802.11 wireless local area networks. In part I of this dissertation, we develop a contention window (CW) control scheme for practical IEEE 802.11 wireless local area networks (WLANs) that have node heterogeneity in terms of the traffic load, transmission rate, and packet size. We introduce activity probability, i.e., the probability that a node contends for medium access opportunities at a given time. We then newly develop a performance analysis model that enables analytic estimation on the contention status including the collision probability, collision time, back-off time, and throughput with comprehensive consideration of node heterogeneity. Based on the newly developed model, we derive the theoretically ideal contention status, and develop a CW control scheme that achieves the ideal contention status in an average sense. We perform extensive NS-3 simulations and real testbed experiments for evaluation of both the proposed performance analysis model and CW control scheme. The results show that the proposed model provides accurate prediction on the contention status, and the proposed CW control scheme achieves considerable throughput improvement compared to the existing schemes which do not comprehensively consider node heterogeneity. In part II of this dissertation, we propose a sounding control scheme for IEEE 802.11ac multi-user multiple-input multiple-output (MU-MIMO). The proposed scheme comprehensively considers the long-term characteristics of a network environment including the downlink traffic loads and channel coherence times of wireless links, and jointly determines the sounding node set and sounding interval to maximize the long-term expected MU-MIMO throughput gain in consideration of sounding overhead. To this end, we analytically formulate an MU-MIMO throughput gain maximization problem considering the network environment and sounding overhead. We conduct MIMO channel measurement in practical WLAN environments, and evaluate the performance of the proposed scheme by employing the real channel data traces. Simulation results verify that the proposed scheme adaptively determines the sounding node set and sounding interval according to the network environment, and outperforms the existing scheme which considers the channel coherence times only. In part III of this dissertation, we develop an adaptive group ID (GID) control scheme to mitigate idle power consumption at nodes in IEEE 802.11ac wireless local area networks (WLANs) supporting multi-user multiple input multiple output (MU-MIMO). We analytically derive the expected idle power consumption at nodes sharing common GIDs, revealing that it has relations with their downlink (DL) traffic loads. Based on the analysis, we formulate an idle power consumption minimization problem, and develop an efficient algorithm to reduce the computational complexity. Simulation results reveal that idle power consumption becomes extremely severe when an access point (AP) has a large number of associated nodes. The proposed scheme assigns GIDs in consideration of DL traffic loads, thus considerably mitigating idle power consumption compared to random GID overloading.1 Introduction 1 1.1 Activity Probability Based Performance Analysis and Contention Control for IEEE 802.11 WLANs 1 1.2 Sounding Node Set and Sounding Interval Determination for IEEE 802.11ac MU-MIMO 3 1.3 Adaptive Group ID Control for Idle Power Consumption Mitigation in IEEE 802.11ac WLANs 5 2 Activity Probability Based Performance Analysis and Contention Controlfor IEEE 802.11 WLANs 7 2.1 DCF and Contention Window control 7 2.2 Activity Probability-Based Performance Analysis Model 8 2.2.1 System Description 8 2.2.2 Activity Probability-Based Throughput Estimation 10 2.2.3 Determination of Activity Probabilities 14 2.2.4 Considering Aggregate MAC Protocol Data Unit (A-MPDU) 16 2.3 Contention Window Control 18 2.3.1 Genie-Aided Ideal Contention Window Control 18 2.3.2 Proposed Contention Window Control 22 2.4 Performance Evaluation 29 2.4.1 Evaluation of Proposed Performance Analysis Model 29 2.4.2 Evaluation of Proposed Contention Window Control 34 2.4.3 Testbed Experiments 43 3 Sounding Node Set and Sounding Interval Determination for IEEE 802.11ac MU-MIMO 48 3.1 MU-MIMO in IEEE 802.11ac 48 3.2 System Description 50 3.3 MIMO Channel Characteristics in real IEEE 802.11ac WLANs 51 3.4 Proposed Sounding Control 54 3.4.1 Derivation of TG (Ts) and TO (Ts) 55 3.4.2 Efficient Determination of Sounding Node Set and Sounding Interval 57 3.5 Performance Evaluation 59 4 Adaptive Group ID Control for Idle Power Consumption Mitigation in IEEE 802.11ac WLANs 65 4.1 Group ID and Power Saving Mechanism in IEEE 802.11ac MU-MIMO 65 4.2 Proposed GID Control 67 4.2.1 System Description 67 4.2.2 Definition of GID Overloading Node Set and Idle Power Consumption Minimization Problem 68 4.2.3 Efficient GID Overloading Algorithm 71 4.3 Performance Evaluation 75 5 Conclusion 80 Abstract (In Korean) 88Docto

Voice-over-IP (VoIP) over wireless local area networks (WLAN).

Wang Wei.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 80-83).Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Motivations and Contributions --- p.1Chapter 1.2 --- Organization of the Thesis --- p.4Chapter Chapter 2 --- Background --- p.6Chapter 2.1 --- IEEE 802.11 --- p.6Chapter 2.1.1 --- Distributed Coordination Function (DCF) / Point Coordination Function (PCF) --- p.7Chapter 2.1.2 --- Types of Networks --- p.8Chapter 2.1.3 --- The 802.11 MAC Sublayer Protocol --- p.9Chapter 2.1.4 --- Why CSMA/CA for Wireless LAN? --- p.11Chapter 2.2 --- Voice over IP (VoIP) --- p.13Chapter 2.2.1 --- Speech Codec --- p.13Chapter 2.2.2 --- The H.323 Standard --- p.13Chapter 2.3 --- Related Work --- p.15Chapter 2.3.1 --- Capacity limits of VoIP over WLAN --- p.16Chapter 2.3.2 --- Methods for increasing VoIP capacity over WLAN --- p.16Chapter 2.3.3 --- Interference between traffic of VoIP and other applications --- p.18Chapter Chapter 3 --- VoIP Multiplex-Multicast Scheme --- p.20Chapter 3.1 --- System Architecture --- p.20Chapter 3.2 --- Packet Multiplexing and Multicasting --- p.22Chapter 3.3 --- Header Compression --- p.24Chapter 3.4 --- Connection Establishment --- p.29Chapter Chapter 4 --- Capacity Analysis --- p.31Chapter 4.1 --- VoIP Capacity Analysis for 802. 11b --- p.31Chapter 4.1.1 --- Capacity of Ordinary VoIP over WLAN --- p.32Chapter 4.1.2 --- Capacity of Multiplex-Multicast Scheme over WLAN --- p.33Chapter 4.2 --- "VoIP Capacity Analysis for 802,11a and 802.11g" --- p.34Chapter 4.3 --- VoIP Capacity with VBR Sources --- p.38Chapter 4.4 --- Simulations --- p.38Chapter Chapter 5 --- Delay Performance --- p.41Chapter 5.1 --- Access Delay --- p.42Chapter 5.2 --- Extra Delay Incurred by the Multiplex-Multicast Scheme --- p.47Chapter Chapter 6 --- VoIP Co-existing with TCP Interference Traffic --- p.49Chapter 6.1 --- Ordinary VoIP co-existing with TCP over WLAN --- p.49Chapter 6.1.1 --- Problem Caused by TCP Interference --- p.49Chapter 6.1.2 --- Solutions --- p.52Chapter 6.2 --- M-M VoIP coexisting with TCP over WLAN --- p.53Chapter 6.3 --- 802.11e --- p.56Chapter 6.3.1 --- EDCA --- p.56Chapter 6.3.2 --- ACK Policies --- p.58Chapter 6.3.3 --- VoIP over EDCA --- p.58Chapter Chapter 7 --- Experimental Validation --- p.61Chapter 7.1 --- Transmission Errors --- p.61Chapter 7.2 --- Prototype Implementation --- p.62Chapter Chapter 8 --- VoIP over Ad Hoc Networks --- p.65Chapter 8.1 --- Mobile Ad Hoc Networks (MANET) and Wireless Distributed System (WDS) --- p.65Chapter 8.2 --- The M-M Scheme in WDS --- p.67Chapter 8.2.1 --- Modified System Architecture --- p.67Chapter 8.2.2 --- Delay Performance --- p.68Chapter 8.2.3 --- Analysis of M-M Scheme in WDS --- p.69Chapter 8.2.4 --- Capacity Improvement --- p.70Chapter 8.2.5 --- Delay Improvement --- p.71Chapter 8.2.6 --- Spectrum Reuse --- p.71Chapter Chapter 9 --- Conclusions --- p.76References --- p.8

Avaliação de desempenho de redes sem fio 802.11b

Orientadores: Nelson Luis Saldanha da Fonseca, Omar Carvalho BranquinhoDissertação (mestrado profissional) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: As redes locais sem fio (WLANs) têm crescido muito ultimamente com a popularidade do padrão 802.11. Diferentemente das redes cabeadas, as WLANs têm algumas características específicas da tecnologia sem fio e utilizam configurações de parâmetros que afetam o desempenho e a interoperabilidade. Este trabalho avalia as redes locais em fio 802.11b, com arquiteturas Fat e arquiteturas Thin. Apresentam-se resultados de medidas de desempenho, nos quais os Pontos de Acesso (APs) testados foram submetidos a tráfego UDP, tendo sido testado o tráfego no sentido AP para estação sem fio. Foram avaliadas situações de taxa máxima fornecida, comportamento com saturação de tráfego e comportamento com estação em condição desfavorável. Mostra-se a superioridade de desempenho na arquitetura Thin em relação às arquiteturas Fat. Justifica-se o desempenho considerando uma priorização de tráfego em função da relação sinal-ruídoAbstract: Wireless Local Area Networks (WLANs) have grown a lot with the popularity of the 802.11 standard. WLAN is different than network wired, it has some specific features from wireless technology and use parameters to configure that affect performance and interoperability. This assignrnent evaluate WLANs 802.11b, with Fat architectures and Thin architecture. It presents results of performance measures, tested Access Point (APs) were submitted to UDP traffic. The traffic flowed from AP to wireless station. The assignrnent evaluated situations to supplied maximum rate, behavior with traftic saturation and behavior with station in degraded rate. It show the good performance with Thin architecture regarding Fat architectures. It justify the performance result considering a traffic priorization for signal-noise ratioMestradoEngenharia de ComputaçãoMestre Profissional em Computaçã

Modelling and performance analysis of mobile ad hoc networks

PhD ThesisMobile Ad hoc Networks (MANETs) are becoming very attractive and useful in many kinds of communication and networking applications. This is due to their efficiency, relatively low cost, and flexibility provided by their dynamic infrastructure. Performance evaluation of mobile ad hoc networks is needed to compare various architectures of the network for their performance, study the effect of varying certain network parameters and study the interaction between various parameters that characterise the network. It can help in the design and implementation of MANETs. It is to be noted that most of the research that studies the performance of MANETs were evaluated using discrete event simulation (DES) utilising a broad band of network simulators. The principle drawback of DES models is the time and resources needed to run such models for large realistic systems, especially when results with a high accuracy are desired. In addition, studying typical problems such as the deadlock and concurrency in MANETs using DES is hard because network simulators implement the network at a low abstraction level and cannot support specifications at higher levels. Due to the advantage of quick construction and numerical analysis, analytical modelling techniques, such as stochastic Petri nets and process algebra, have been used for performance analysis of communication systems. In addition, analytical modelling is a less costly and more efficient method. It generally provides the best insight into the effects of various parameters and their interactions. Hence, analytical modelling is the method of choice for a fast and cost effective evaluation of mobile ad hoc networks. To the best of our knowledge, there is no analytical study that analyses the performance of multi-hop ad hoc networks, where mobile nodes move according to a random mobility model, in terms of the end-to-end delay and throughput. This work ii presents a novel analytical framework developed using stochastic reward nets and mathematical modelling techniques for modelling and analysis of multi-hop ad hoc networks, based on the IEEE 802.11 DCF MAC protocol, where mobile nodes move according to the random waypoint mobility model. The proposed framework is used to analysis the performance of multi-hop ad hoc networks as a function of network parameters such as the transmission range, carrier sensing range, interference range, number of nodes, network area size, packet size, and packet generation rate. The proposed framework is organized into several models to break up the complexity of modelling the complete network and make it easier to analyse each model as required. This is based on the idea of decomposition and fixed point iteration of stochastic reward nets. The proposed framework consists of a mathematical model and four stochastic reward nets models; the path analysis model, data link layer model, network layer model and transport layer model. These models are arranged in a way similar to the layers of the OSI protocol stack model. The mathematical model is used to compute the expected number of hops between any source-destination pair; and the average number of carrier sensing, hidden, and interfering nodes. The path analysis model analyses the dynamic of paths in the network due to the node mobility in terms of the path connection availability and rate of failure and repair. The data link layer model describes the behaviour of the IEEE 802.11 DCF MAC protocol. The actions in the network layer are modelled by the network layer model. The transport layer model represents the behaviour of the transport layer protocols. The proposed models are validated using extensive simulations

Cross layer optimization in 4G Wireless mesh networks

Wireless networks have been rapidly evolving over the past two decades. It is foreseen that Fourth generation (4G) wireless systems will involve the integration of wireless mesh networks and the 3G wireless systems such as WCDMA. Moreover their wireless mesh routers will provide service to wireless local networks (WLANs) and possibly incorporate MIMO system and smart admission control policies among others. This integration will not only help the service providers cost effectiveness and users connectivities but will also improve and guarantee the QoS criteria. On the other hand, cross layer design has emerged as a new and major thrust in improving the quality of service (QoS) of wireless networks. Cross layer design involves the interaction of various layers of the network hierarchy which could further improve the QoS of the 4G integrated networks. In this work we seek new techniques for improving the overall QoS of integrated 4G systems. Towards this objective we start with the local low tier WLAN access. We then investigate CDMA alternatives to the TDMA access for wireless mesh networks. Cross layer design in wireless mesh networks is then pursued. In the first phase of this thesis a new access mechanism for WLANs is developed, in which users use an optimum transmission probability obtained by estimating the number of stations from the traffic conditions in a sliding window fashion, thereby increasing the throughput compared to the standard DCF and RTS/CTS mechanism while maintaining the same fairness and the delay performance. In the second phase we introduce a code division multiple access/Time division duplex technique CDMA/TDD for wireless mesh networks, we outline the transmitter and receiver for the relay nodes and evaluate the efficiency, delay and delay jitter performances. This CDMA based technique is more amenable to integrating the two systems (Mesh networks and WCDMA or CDMA 2000 of3G). We compare these results with the TDMA operation and through analysis we prove that the CDMA system outperforms the TDMA counterparts. In the third phase we proceed to an instance of cross layer optimized networks, where we develop an overall optimization routine that finds simultaneously the best route and the best capacity allocation to various nodes. This optimization routine minimizes the average end to end packet delay over all calls subject to various contraints. In the process we use a new adaptive version of Spatial TDMA as a platform for comparison purposes of the MAC techniques involved in the cross layer design. In this phase we also combine CDMA/TDD and optimum routing for cross layer design in wireless mesh networks. We compare the results of the CDMA/TDD system with results obtained from the STDMA system. In our analysis we consider the parallel transmissions of mesh nodes in a mesh topology. These parallel transmissions will increase the capacity resulting in a higher throughput with a lower delay. This will allow the service providers to accommodate more users in their system which will obviously reduce the colt and the end users will enjoy a better service paying a lower amount