Performance analysis of contention based bandwidth request mechanisms in WiMAX networks

This article is posted here with the permission of IEEE. The official version can be obtained from the DOI below - Copyright @ 2010 IEEEWiMAX networks have received wide attention as they support high data rate access and amazing ubiquitous connectivity with great quality-of-service (QoS) capabilities. In order to support QoS, bandwidth request (BW-REQ) mechanisms are suggested in the WiMAX standard for resource reservation, in which subscriber stations send BW-REQs to a base station which can grant or reject the requests according to the available radio resources. In this paper we propose a new analytical model for the performance analysis of various contention based bandwidth request mechanisms, including grouping and no-grouping schemes, as suggested in the WiMAX standard. Our analytical model covers both unsaturated and saturated traffic load conditions in both error-free and error-prone wireless channels. The accuracy of this model is verified by various simulation results. Our results show that the grouping mechanism outperforms the no-grouping mechanism when the system load is high, but it is not preferable when the system load is light. The channel noise degrades the performance of both throughput and delay.This work was supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/G070350/1 and by the Brunel University’s BRIEF Award

Wireless broadband access: WiMAX and beyond - Investigation of bandwidth request mechanisms under point-to-multipoint mode of WiMAX networks

The WiMAX standard specifies a metropolitan area broadband wireless access air interface. In order to support QoS for multimedia applications, various bandwidth request and scheduling mechanisms are suggested in WiMAX, in which a subscriber station can send request messages to a base station, and the base station can grant or reject the request according to the available radio resources. This article first compares two fundamental bandwidth request mechanisms specified in the standard, random access vs. polling under the point-to-multipoint mode, a mandatory transmission mode. Our results demonstrate that random access outperforms polling when the request rate is low. However, its performance degrades significantly when the channel is congested. Adaptive switching between random access and polling according to load can improve system performance. We also investigate the impact of channel noise on the random access request mechanism

Adjusting WiMAX for a Dedicated Surveillance Network

WiMAX (Worldwide Interoperability for Microwave Access) devices have been used widely in the market. WiMAX-based video surveillance products have also been available. The acceptance of WiMAX in the market, as well as the availability of WiMAX products, contributes to the possibility of implementing it for dedicated video surveillance application. However, since WiMAX is designed to accommodate various applications with different quality of service (QoS) requirements, WiMAX–based dedicated surveillance network may not achieve optimum performance, as all SSs generate the same QoS requirements. The scheduler cannot implement traffic type priority; therefore, service classification does not work as expected. This paper proposes WiMAX adjustment to transform a multi-purpose WiMAX network into a network dedicated to video surveillance. NS-2 simulations show that the proposed adjustment is able to deliver low delay and high quality video surveillance.DOI:http://dx.doi.org/10.11591/ijece.v3i4.318

Bandwidth and Power Management in Broadband Wireless Networks

Bandwidth and power are considered as two important resources in wireless networks. Therefore, how to management these resources becomes a critical issue. In this thesis, we investigate this issue majorally in IEEE 802.16 networks. We first perform performance analysis on two bandwidth request mechanisms defined in IEEE 802.16 networks. We also propose two practical performance objectives. Based on the analysis, we design two scheduling algorithm to achieve the objectives. Due to the characteristics of popular variable bit rate (VBR) traffic, it is very difficult for subscriber stations (SSs) to make appropriate bandwidth reservation. Therefore, the bandwidth may not be utilized all the time. We propose a new protocol, named bandwidth recycling, to utilized unused bandwidth. Our simulation shows that the proposed scheme can improve system utilization averagely by 40\%. We also propose a more aggressive solution to reduce the gap between bandwidth reservation and real usage. We first design a centralized approach by linear programming to obtain the optimal solution. Further, we design a fully distributed scheme based on game theory, named bandwidth reservation (BR) game. Due to different quality of service (QoS) requirements, we customize the utility function for each scheduling class. Our numerical and simulation show that the gap between BR game and optimal solution is limited. Due to the advantage of dynamical fractional frequency reuse (DFFR), the base station (BS) can dynamically adjust transmission power on each frequency partition. We emphasis on power allocation issue in DFFR to achieve most ecomicical data transmission. We first formulate the problem by integer linear programming (ILP). Due to high computation complexity, we further design a greedy algorithm. Our simulation shows that the results of the greedy algorithm is very close to the ILP results

Design and analysis of MAC protocols for wireless networks

During the last few years, wireless networking has attracted much of the research and industry interest. In addition, almost all current wireless devices are based on the IEEE 802.11 and IEEE 802.16 standards for the local and metropolitan area networks (LAN/MAN) respectively. Both of these standards define the medium access control layer (MAC) and physical layer (PHY) parts of a wireless user. In a wireless network, the MAC protocol plays a significant role in determining the performance of the whole network and individual users. Accordingly, many challenges are addressed by research to improve the performance of MAC operations in IEEE 802.11 and IEEE 802.16 standards. Such performance is measured using different metrics like the throughput, fairness, delay, utilization, and drop rate. We propose new protocols and solutions to enhance the performance of an IEEE 802.11 WLAN (wireless LAN) network, and to enhance the utilization of an IEEE 802.16e WMAN (wireless MAN). First, we propose a new protocol called HDCF (High-performance Distributed Coordination Function), to address the problem of wasted time, or idle slots and collided frames, in contention resolution of the IEEE 802.11 DCF. Second, we propose a simple protocol that enhances the performance of DCF in the existence of the hidden terminal problem. Opposite to other approaches, the proposed protocol attempts to benefit from the hidden terminal problem. Third, we propose two variants of a simple though effective distributed scheme, called NZ-ACK (Non Zero-Acknowledgement), to address the effects of coexisting IEEE 802.11e EDCA and IEEE 802.11 DCF devices. Finally, we investigate encouraging ertPS (enhanced real time Polling Service) connections, in an IEEE 802.16e, network to benefit from contention, and we aim at improving the network performance without violating any delay requirements of voice applications

A Unified Performance Model for Best-Effort Services in WiMAX Networks

Based on the work from the IEEE Working Group 802.16 and ETSI HiperMAN Working Group, the WiMAX (Worldwide Interoperability for Microwave Access) technology is defined by the WiMAX Forum to support fixed and mobile broadband wireless access. In the standard (IEEE 802.16 standard, 2009), it defines several air interface variants, including WirelessMAN-SC, WirelessMAN-OFDM, WirelessMAN-OFDMA and WirelessMAN-HUMAN. WiMAX networks can be operated in two different modes: point to multi-point (PMP) mode and mesh mode. Under the PMP mode, all traffics from subscriber stations (SSs) are controlled by the base station. Mesh mode is a distributed architecture where traffics are allowed to route not only between SSs and the base station but also between SSs. In this chapter, we focus on the WirelessMAN-SC air interface operating in the PMP mode. In WiMAX networks, quality of service (QoS) is provided through five different services classes in the MAC layer (Andrews et al., 2007): 1. Unsolicited grant service (UGS) is designed for real-time applications with constant data rate. These applications always have stringent delay requirement, such as T1/E1. 2. Real-time polling service (rtPS) is designed for real-time applications with variable data rate. These applications have less stringent delay requirement, such as MPEG and VoIP without silence suppression. 3. Extended real-time polling service (ertPS) builds on the efficiency of both UGS and rtPS. It is designed for the applications with variable data rate such as VoIP with silence suppression. 4. Non-real-time polling service (nrtPS) is designed to support variable bit rate non-real-time applications with certain bandwidth guarantee, such as high bandwidth FTP. 5. Best effort service (BE) is designed for best effort applications such as HTTP. To meet the requirements of different service classes, several bandwidth request mechanisms have been defined, namely, unsolicited granting, unicast polling, broadcast polling and piggybacking. In this chapter, we present a performance model for services, such as BE service, based on the broadcast polling mechanism which is contention based and requires he SSs to use the truncated binary exponential backoff (TBEB) algorithm (Kwak et al., 2005) to resolve contention

A Survey on Scheduling in IEEE 802.16 Mesh Mode

Cataloged from PDF version of article.IEEE 802.16 standard (also known as WiMAX) defines the wireless broadband network technology which aims to solve the so called last mile problem via providing high bandwidth Internet even to the rural areas for which the cable deployment is very costly. The standard mainly focuses on the MAC and PHY layer issues, supporting two transmission modes: PMP (Point-to-Multipoint) and mesh modes. Mesh mode is an optional mode developed as an extension to PMP mode and it has the advantage of having an improving performance as more subscribers are added to the system using multi-hop routes. In 802.16 MAC protocol, mesh mode slot allocation and reservation mechanisms are left open which makes this topic a hot research area. Hence, the focus of this survey will mostly be on the mesh mode, and the proposed scheduling algorithms and performance evaluation methods