101 research outputs found

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

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    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

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    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

    New contention resolution schemes for WiMAX

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    Abstract—The use of Broadband Wireless Access (BWA) technology is increasing due to the use of Internet and multimedia applications with strict requirements of end–to–end delay and jitter, through wireless devices. The IEEE 802.16 standard, which defines the physical (PHY) and the medium access control (MAC) layers, is one of the BWA standards. Its MAC layer is centralized basis, where the Base Station (BS) is responsible for assigning the needed bandwidth for each Subscriber Station (SS), which requests bandwidth competing between all of them. The standard defines a contention resolution process to resolve the potential occurrence of collisions during the requesting process. In this paper, we propose to modify the contention resolution process to improve the network performance, including end–to–end delay and throughput

    Performance Study of Bandwidth Request Mechanisms in IEEE 802.16e Networks

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    WiMAX (Worldwide Interoperability for Microwave Access) is the IEEE 802.16 standards-based wireless technology that provides fixed and mobile Internet access for Metropolitan Area Networks (MAN). The IEEE 802.16 std. includes medium access control (MAC) and physical (PHY) layer pecifications and is consider to be a promising technology. Bandwidth reservation is employed to provide quality of service (QoS) to guarantee different services specified in the standard. A bandwidth request/grant scheme is defined in the IEEE 802.16 standard. There are two types of bandwidth request (BR) mechanisms, i.e., polling and contention resolution, which are defined in the standard. As specified, connections belonging to scheduling classes of extended real-time polling service, non-real-time polling service, and best effort have options to make BRs via both mechanisms, depending on the scheduling decision made by the base station (BS). This paper attempts the comparative study of BR mechanisms for different service classes defined in the standard

    Performance Analysis for Bandwidth Allocation in IEEE 802.16 Broadband Wireless Networks using BMAP Queueing

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    This paper presents a performance analysis for the bandwidth allocation in IEEE 802.16 broadband wireless access (BWA) networks considering the packet-level quality-of-service (QoS) constraints. Adaptive Modulation and Coding (AMC) rate based on IEEE 802.16 standard is used to adjust the transmission rate adaptively in each frame time according to channel quality in order to obtain multiuser diversity gain. To model the arrival process and the traffic source we use the Batch Markov Arrival Process (BMAP), which enables more realistic and more accurate traffic modelling. We determine analytically different performance parameters, such as average queue length, packet dropping probability, queue throughput and average packet delay. Finally, the analytical results are validated numerically.Comment: 16 page

    Performance analysis of contention based bandwidth request mechanisms in WiMAX networks

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    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

    Reverse Direction Transmission in Wireless Networks: Review

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    Reverse direction mechanism is a promising significant development that may lead to promoting the accuracy of TXOP. The transfer, in conventional TXOP operation, is one way direction out of the station which holds the TXOP and which is not applied to some network services using two lane traffic namely VoIP and on-line gaming. Therefore, the conventional TXOP operation enhances only the forward direction transfer, but not the reverse direction transfer. Moreover, reverse direction mechanism makes it possible for the holder of TXOP to reserve unused TXOP time for its receivers which may improve the channel utilization as well as the performance of reverse direction traffic flows. It is well-known that the reverse direction transfer scheme aims mainly to improve the effectiveness and that plays a key role in reducing the overhead and increasing the system throughput. Thus, this paper provides an overview of a research progress in reverse direction transmission scheme over high speed wireless LANs. Moreover, it addresses the reverse direction mechanism that has been proposed for the next generation wireless networks and the ones adopted by IEEE 802.11n standard. Furthermore, it stresses the reverse issues that require to be dealt with in order to bring further progress to the reverse direction transmission

    ADAPTIVE CHANNEL SPLIT RATIO IN TDD BASED WI-MAX NETWORK FOR LINK IMPROVEMENT ANALYSIS

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    The last mile access for residential user are asymmetric. As a result an equal split between the uplink and downlink channel cause inefficient bandwidth utilization. Improper allocation will severely affect the traffic. In this work the main focus is TCP performance during improper bandwidth allocation. The TDD framing in Wi-max is adaptive in the order to make the downlink to uplink bandwidth ratio vary with time. Adaptive channel split ratio, adjust the bandwidth ratio with the help of present traffic profile, transport layer parameters and wireless interference. This scheme will provide higher throughput. The performance of the proposed scheme is validated via ns-2 simulation
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