Bandwidth-guaranteed multicast in multi-channel multi-interface wireless mesh networks

Proceedings of the IEEE International Conference on Communications, 2009, p. 1-5We consider multi-channel multi-interface wireless mesh networks with a schedule-based MAC protocol, where conflict-free transmission is ensured by requiring links assigned with the same channel and within the mutual interference range of each other to be active at different time slots. When a (point-to-multipoint) multicast call arrives, the call is accepted if a multicast distribution tree can be established for connecting the source node with all the receiving nodes, and with sufficient bandwidth reserved on each link. Otherwise, the call is rejected. To maximize the call acceptance rate, the multicast tree must be constructed judiciously upon each call arrival. Aiming at minimizing the carried load on the most-heavily loaded channel, and maximizing the residual capacity of the most heavily loaded node, an integer linear program (ILP) is formulated for multicast tree construction. Since solving ILP can be time-consuming, an efficient heuristic algorithm is then proposed. We compare the two tree construction algorithms by simulations. We found that both algorithms give comparable call acceptance rate, but the heuristic algorithm requires much shorter running time. ©2009 IEEE.published_or_final_versio

Maximizing multicast call acceptance rate in multi-channel multi-interface wireless mesh networks

In this paper, we consider the problem of constructing bandwidth-guaranteed multicast tree in multi-channel multi-interface wireless mesh networks. We focus on the scenario of dynamic multicast call arrival, where each call has a specific bandwidth requirement. A call is accepted if a multicast tree with sufficient bandwidth on each link can be constructed. Intuitively, if the carried load on both the most-heavily loaded channel and the most-heavily loaded node is minimized, the traffic load in the network will be balanced. If the network load is balanced, more room will be available for accommodating future calls. This would maximize the call acceptance rate in the network. With the above notion of load balancing in mind, an Integer Linear Programming (ILP) formulation is formulated for constructing bandwidth-guaranteed tree. We show that the above problem is NP-hard, and an efficient heuristic algorithm called Largest Coverage Shortest-Path First (LC-SPF) is devised. Simulation results show that LC-SPF yields comparable call acceptance rate as the ILP formulation, but with much shorter running time. © 2010 IEEE.published_or_final_versio

Efficient wireless multimedia multicast in multi-rate multi-channel mesh networks.

Devices in wireless mesh networks can operate on multiple channels (MC) and automatically adjust their transmission rates for the occupied channels. This paper shows how to improve performance-guaranteed multicasting transmission coverage for wireless multihop mesh networks by exploring the transmission opportunity offered by multiple rates (MR) and MC. Based on the characteristics of transmissions with different rates, we propose and analyze parallel low-rate transmissions and alternative rate transmissions (ART) to explore the advantages of MRMC in improving the performance and coverage tradeoff under the constraint of limited channel resources. We then apply these new transmission schemes to improve the WMN multicast experience. Combined with the strategy of reliable interference-controlled connections, a novel MRMC multicast algorithm (LC-MRMC) is designed to make efficient use of channel and rate resources to greatly extend wireless multicast coverage with high throughput and short delay performance. Our NS2 simulation results prove that ART and LC-MRMC achieve improved wireless transmission quality across much larger areas as compared to other related studies

Performance evaluation of WLAN for mutual interaction between unicast and multicast communication sessions

In this Thesis, performance evaluation of wireless local area networks (WLANs) is conducted to understand the effects of mutual interaction between real-time unicast and multicast communication sessions. The analysis extends the performance evaluation of WLAN from the isolated study of unicast or multicast sessions to their mutual interaction. The nature of multicast session is VoIP, whereas the unicast sessions are VoIP and a single video flow. The performance of unicast and multicast sessions is investigated by simulations for experienced quality of service. The reliability concerns of simulator performance are addressed by verifying the simulator against an experimental setup. It takes into account the Medium Access Control (MAC) and Physical (PHY) layer parameters and the probability of collision for increasing number of sessions. The analysis environment is a single WLAN cell where the sessions are mobile. The mobility of the sessions is mapped with a proposed group mobility model whose statistical properties are studied via simulations. The performance results obtained with the sessions' mobility are compared with those of static sessions and sessions moving according to the Random Waypoint (RWP) mobility model

Improving the Performance of Wireless LANs

This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids

Transmission rate sampling and selection for reliable wireless multicast

The multicast communication concept offers a scalable and efficient method for many classes of applications; however, its potential remains largely unexploited when it comes to link-layer multicasting in wireless local area networks. The fundamental lacking feature for this is a transmission rate control mechanism that offers higher transmission performance and lower channel utilization, while ensuring the reliability of wireless multicast transmissions. This is much harder to achieve in a scalable manner for multicast when compared with unicast transmissions, which employs explicit acknowledgment mechanisms for rate control. This article introduces EWRiM, a reliable multicast transmission rate control protocol for IEEE 802.11 networks. It adapts the transmission rate sampling concept to multicast through an aggregated receiver feedback scheme and combines it with a sliding window forward error correction (FEC) mechanism for ensuring reliability at the link layer. An inherent novelty of EWRiM is the close interaction of its FEC and transmission rate selection components to address the performance-reliability tradeoff in multicast communications. The performance of EWRiM was tested in three scenarios with intrinsically different traffic patterns; namely, music streaming scenario, large data frame delivery scenario, and an IoT scenario with frequent distribution of small data packets. Evaluation results demonstrate that the proposed approach adapts well to all of these realistic multicast traffic scenarios and provides significant improvements over the legacy multicast- and unicast-based transmissions.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

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

Design and Analysis of Medium Access Control Protocols for Broadband Wireless Networks

The next-generation wireless networks are expected to integrate diverse network architectures and various wireless access technologies to provide a robust solution for ubiquitous broadband wireless access, such as wireless local area networks (WLANs), Ultra-Wideband (UWB), and millimeter-wave (mmWave) based wireless personal area networks (WPANs), etc. To enhance the spectral efficiency and link reliability, smart antenna systems have been proposed as a promising candidate for future broadband access networks. To effectively exploit the increased capabilities of the emerging wireless networks, the different network characteristics and the underlying physical layer features need to be considered in the medium access control (MAC) design, which plays a critical role in providing efficient and fair resource sharing among multiple users. In this thesis, we comprehensively investigate the MAC design in both single- and multi-hop broadband wireless networks, with and without infrastructure support. We first develop mathematical models to identify the performance bottlenecks and constraints in the design and operation of existing MAC. We then use a cross-layer approach to mitigate the identified bottleneck problems. Finally, by evaluating the performance of the proposed protocols with analytical models and extensive simulations, we determine the optimal protocol parameters to maximize the network performance. In specific, a generic analytical framework is developed for capacity study of an IEEE 802.11 WLAN in support of non-persistent asymmetric traffic flows. The analysis can be applied for effective admission control to guarantee the quality of service (QoS) performance of multimedia applications. As the access point (AP) becomes the bottleneck in an infrastructure based WLAN, we explore the multiple-input multiple-output (MIMO) capability in the future IEEE 802.11n WLANs and propose a MIMO-aware multi-user (MU) MAC. By exploiting the multi-user degree of freedom in a MIMO system to allow the AP to communicate with multiple users in the downlink simultaneously, the proposed MU MAC can minimize the AP-bottleneck effect and significantly improve the network capacity. Other enhanced MAC mechanisms, e.g., frame aggregation and bidirectional transmissions, are also studied. Furthermore, different from a narrowband system where simultaneous transmissions by nearby neighbors collide with each other, wideband system can support multiple concurrent transmissions if the multi-user interference can be properly managed. Taking advantage of the salient features of UWB and mmWave communications, we propose an exclusive region (ER) based MAC protocol to exploit the spatial multiplexing gain of centralized UWB and mmWave based wireless networks. Moreover, instead of studying the asymptotic capacity bounds of arbitrary networks which may be too loose to be useful in realistic networks, we derive the expected capacity or transport capacity of UWB and mmWave based networks with random topology. The analysis reveals the main factors affecting the network (transport) capacity, and how to determine the best protocol parameters to maximize the network capacity. In addition, due to limited transmission range, multi-hop relay is necessary to extend the communication coverage of UWB networks. A simple, scalable, and distributed UWB MAC protocol is crucial for efficiently utilizing the large bandwidth of UWB channels and enabling numerous new applications cost-effectively. To address this issue, we further design a distributed asynchronous ER based MAC for multi-hop UWB networks and derive the optimal ER size towards the maximum network throughput. The proposed MAC can significantly improve both network throughput and fairness performance, while the throughput and fairness are usually treated as a tradeoff in other MAC protocols