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The Research on Radio Resource Management Technology in Broadband OFDMA System

Author: ZhangZuoFeng
Tutor: WuWeiLing
School: Beijing University of Posts and Telecommunications
Course: Signal and Information Processing
Keywords: B3G/4G OFDMA Uplink scheduling mechanism Radio Resource Management Packet Scheduling Cellular Network with Relay Station Channel Allocation Power Allocation
CLC: TN915.07
Type: PhD thesis
Year: 2007
Downloads: 912
Quote: 10
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Abstract


With rapid development of mobile communication and internet network, the requirement of broadband wireless access is increasing to meet the dramatically growing demands for wireless multimedia services. The next-generation mobile communication systems (B3G/4G) provide high data-rate, support more subscribers and guarantee quality-of-service (QoS). So advanced technologies will be applied in the B3G/4G system to provide higher frequency efficiency within limited wireless bandwidth, among which orthogonal frequency division multiple access (OFDMA) system is promising technology.In OFDMA cellular system, uplink allocation is performed efficiently by base station (BS) mainly depending on the traffic information reported from UE. In order to support multimedia services, the OFDMA system provides some scheduling services, each with an associated service class according to their QoS requirements and realizes uplink bandwidth dynamic allocation. In the dissertation, how to support VoIP service is investigated in three uplink scheduling service mechanisms that are designed to support real-time service flow. Considering voice ON-OFF state characteristic of VoIP service, a new ErtPS uplink scheduling service mechanism for VoIP is proposed which utilizes user grouping and multi-polling scheme based on OFF state probability distribution. Via analysis of theory, on condition of VoIP real time delay guarantee, the proposed mechanism reduces uplink resource requirement efficiently when VoIP service is during OFF state. So it could support more VoIP users compared with three conventional uplink scheduling service mechanisms in OFDMA system.Subsequently, the dissertation focuses on adaptive wireless resource allocation algorithms for OFDMA system which exploit the independent subchannel fading of different users and acquire multiuser diversity gain. Considering QoS requirement besides wireless channel fading for real-time service, the resource allocation problem with QoS constrained is investigated. Two reduced-complexity scheduling algorithms are introduced to implement fast multiuser packet scheduling in OFDMA system. The two algorithms execute the fixed power allocation equally with adaptive modulation on all subchannels and apply Max-Max method and subchannel utilization factor among users on subchannel allocation policy. The results indicate that the two algorithms can improve subchannel transmission efficiency with guaranteed delay QoS requirement and maximize throughput in adaptive OFDMA system. Besides, the fairness of packet scheduling algorithm is evaluated in OFDMA system.The next-generation communication network could not only provide more system capacity but also guarantee the almost-ubiquitous provision of very high data rate coverage. Towards this end, in addition to advanced transmission techniques, some major modifications in the wireless network architecture itself are sought. An architecture, which is based on introducing relaying technologies into the cellular infrastructure, seems an attractive and competitive network for future mobile communication by alleviating some of the shortcomings of today’s cellular concept and with lower cost of running a communication network. So the research on subchannel assignment and power allocation is conducted for OFDMA cellular communication system with relay station(RS).In the cellular mobile communication system with two-hop fixed relay stations, an additional channel is needed by a relay station to forward the data. To make full of limited wireless resource, the channel assignment policy among cells is researched. And a relay fixed channel assignment policy is proposed for cellular network with RS on the condition of frequency reuse factor being equal to one, which based on the deployment of the relay stations and the partition of OFDMA time-frequency frame. Considering time-variety and non-uniform traffic distribution, a flexible hybrid channel assignment policy is further presented which maximizes the minimum co-channel interference among adjacent cells and is more adaptive to different traffic distribution. So the relay channel assignment policy could reduce co-channel system interference and improve system performance.Data may be forwarded by relay stations in multihop cellular network. The system power consumption may be minimized by adjusting the transmit power of each hop adaptively. The optimal power allocation problem is formulated with the end-to-end effective links throughput constraint. A power allocation scheme over source-relay-destination links is investigated which is based on dependent multihop wireless link fading, then a new adaptive allocation scheme joint power and time-slot is proposed and the optimal time-slot and power allocation is derived.Results show that the proposed joint power allocation strategy has superior performance in view of power consumption on the condition of the same system throughput guarantee.

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