83 research outputs found
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
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Investigation of efficient resource allocation schemes for WiMAX networks
This thesis was submitted for the degree of Master of Philosophy and was awarded by Brunel University on 9 July 2008.WiMax (Worldwide Interoperability for Microwave Access) is a promising wireless technology with the aim of providing the last mile wireless broadband access designed for both fixed and mobile consumers as an alternative solution to the wired DSL and cable access schemes. The purpose of this research project is to investigate efficient resource allocation algorithms for WiMax. To achieve this goal, we investigate efficient PHY layer Partial Usage of SubCarriers (PUSC) allocation as well as MAC layer piggyback bandwidth request mechanisms. At the PHY layer we proposed improvements on the Uplink and Downlink PUSC subcarrier allocation scheme. For the Uplink PUSC we suggested a method by allocating different frequencies to neighbouring cells in combination with the Integer Frequency Reuse (IFR) and Fractional Frequency Reuse (FFR) in order to reduce interferences and collisions. The simulation results exhibit that collision rates can be reduced to zero for both IFR and FFR patterns with the proposed improvement by assuming that perfect power control is used in the system. In addition, there is no collision at cell edges. The results also show that FFR patterns achieve lower inter-cell interference and higher capacities as compared to the IFR patterns. For the Downlink PUSC we introduced an offset scheme with the purpose of increasing the number of users in the system. At the MAC layer we propose an improvement on the piggyback bandwidth request mechanism by increasing the size of the piggyback bandwidth request in order to reduce the number of bandwidth requests and hence improve the resource utilisation. The simulation results demonstrate that our improved scheme achieves higher throughput, less delay and packet loss rates as compared to the standardised piggyback bandwidth 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, WiMAXâbased 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
AbstractâThe use of Broadband Wireless Access (BWA) technology is increasing due to the use of Internet and multimedia applications with strict requirements of endâtoâend 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 endâtoâend delay and throughput
Performance Study of Bandwidth Request Mechanisms in IEEE 802.16e Networks
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
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
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 Universityâs BRIEF Award
Reverse Direction Transmission in Wireless Networks: Review
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
A Novel Approach for Implementing Worldwide Interoperability for Microwave Access for Video Surveillance
Video surveillance applications have experienced an increase in demand over the last decade. Surveillance
systems can easily be found in places such as commercial offices, banks and traffic intersections, parks and
recreational areas. Surveillance applications have the potential to be implemented on a WiMAX (Worldwide
Interoperability for Microwave Access) network. Moreover, WiMAX devices have been used widely in the
market and WiMAX-based video surveillance products have also been available. As a radio technology,
WiMAX is a wireless broadband system that offers greater capacity than WiFi networks and wider coverage
than cellular networks.
The acceptance of WiMAX in the market, the availability of WiMAX products and its technology excellence,
contribute to the possibility of implementing it for surveillance application. However, since WiMAX is designed
to accommodate various applications with different quality of service (QoS) requirements, dedicated surveillance
network implementation of WiMAX may not achieve optimum performance, as all Subscriber Stations (SSs)
generate the same QoS requirements.
In the medium access (MAC) layer, this thesis proposes a bandwidth allocation scheme that considers the QoS
uniformity of the traffic sources. The proposed bandwidth allocation scheme comprises a simplified bandwidth
allocation architecture, a packet-aware bandwidth request mechanism and packet-aware scheduling algorithms.
The simplified architecture maximizes resources in the Base Station (BS), deactivates unnecessary services and
minimizes the processing delay. The proposed bandwidth request mechanism reduces bandwidth grant and
transmission delays. The proposed scheduling algorithms prioritize bandwidth granting access to a request that
contains important packet(s). The proposed methods in the MAC layer are designed to be applied to existing
devices in the market, without the necessity to change hardware.
The transport protocol should be able to deliver video with sufficient quality while maintaining low delay
connectivity. The proposed transport layer protocol is therefore designed to improve the existing user datagram
protocol (UDP) performance by retransmitting packet loss selectively to increase the received video quality, and
utilizing MAC support to achieve low delay connectivity.
In order to overcome the limitations of the lower layers, this thesis employs a rateless code instead of transport
layer redundancy in the application layer. Moreover, this thesis proposes post-decoding error concealment
techniques as the last means to overcome packet loss.
To evaluate the performances of the proposed methods, simulations are carried out using NS-2 simulator on
Linux platform. The proposed methods are compared to existing works to measure their effectiveness. To
facilitate the implementation of the transport layer protocols in practical scenarios, UDP packet modification is
applied for each transport layer protocol.Indonesian Directorate General of Higher Education (DGHE/DIKTI
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