基植於IEEE 802.16m正交分頻多工多重存取系統下, 一個具子通道感知的變動長度下行頻寬配置機制

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Title:	基植於IEEE 802.16m正交分頻多工多重存取系統下, 一個具子通道感知的變動長度下行頻寬配置機制
Other Titles:	A subchannel-aware variable-length burst scheduling algorithm for downlink traffic in IEEE 802.16m ofdma systems
Authors:	江致平;Chiang, Chih-Ping
Contributors:	淡江大學資訊工程學系資訊網路與通訊碩士班石貴平
Keywords:	排程;資源配置;正交分頻多工多重存取;IEEE 802.16m;scheduling;resource allocation;OFDMA
Date:	2011
Issue Date:	2011-12-28 18:57:38 (UTC+8)
Abstract:	本論文考量在IEEE 802.16m OFDMA Frame架構下，提出一個Downlink頻寬管理機制來分配與規劃Downlink AAI Subframe中Burst的Subchannel 與OFDMA Symbol Time，此機制之基本概念在於針對不同使用者，配置可支援較高傳送速率的Subchannel藉以提升網路的整體傳輸效能。由於不當地分配Subchannel與OFDMA Symbol Time會造成Downlink無線資源利用率下降與Downlink AAI Subframe嚴重外部碎裂與內部碎裂，進而降低網路整體執行效能。為了解決上述之問題，本論文針對Downlink頻寬之分配與排程，提出一Subchannel-Aware Variable-Length Burst Scheduling (VLBS) Algorithm調整與分配每個排程的Burst之Subchannel位置與大小，透過適當的Subchannel配置與安排，能夠提升網路整體執行效能與增加Subchannel利用率，並能夠讓Downlink AAI Subframe中的可用資源大幅度增加。由實驗結果發現，ABS經由演算法可以有效地降低內部碎裂及外部碎裂之問題發生，提昇Downlink AAI Subframe的利用率。進而增加Downlink Subframe的產能，而且也真的提高了網路傳輸的效能。 Burst is an atomic bandwidth allocation unit in IEEE 802.16m OFDMA system. Each burst is composed of subchannels and OFDMA symbol time. This paper investigates the downlink burst allocation problem (BAP) in IEEE 802.16 OFDMA systems. In order to solve this problem, this paper proposes a subchannel-aware Variable-Length Burst Scheduling (VLBS) algorithm for throughput gains and control overhead alleviations, to schedule the position of each burst based on the rectangular mapping constraint. VLBS contains two vital schemes, including the burst allocation scheme and the burst compression scheme. The burst allocation scheme is used to schedule the position of each burst and to adjust the shape of each burst in the downlink AAI subframe. Through the burst allocation scheme, the wasted LRU caused by the external fragmentation problem (EFP) can be alleviated in an efficient manner. In the meanwhile, the utilization of downlink bandwidth can be improved. In order to achieve the rectangular mapping, the OFDMA slots will be wasted due to the internal fragmentation problem (IFP). With the increasing number of bursts. Therefore, the wasted OFDMA slots caused by IFP can be released for other bursts by burst fragmentation and the A-MAP control overhead also be reduced through burst packing. Since the A-MAP message is transmitted with the most robust burst profile, the bursts are transmitted in order of decreasing robustness. This paper is the first one to consider this transmission characteristic in the OFDMA system. The simulation results highlight that VLBS outperforms other related approaches in the throughput, the satisfaction ratio, and the downlink utilization ratio.
Appears in Collections:	[Graduate Institute & Department of Computer Science and Information Engineering] Thesis

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