IEEE802.16j中具干擾感知之訊框排程的研究

Abstract

IEEE 802.16標準中，有所謂Multi-hop Relay (MR)的概念，其中存在很多問題需要解決，所以在IEEE 802.16j標準中提出中繼傳輸站(Relay Station，RS)來延伸原來的涵蓋範圍及解決遮蔽效應造成訊號衰弱的問題。但在MR中由於多了中繼傳輸站來傳遞資料，網路拓樸變得相對複雜，資料從發送端到接收端的路徑變長了，在資料大量傳輸的狀況下，會因干擾及壅塞的問題變得嚴重而導致整個網路效能低落。本研究提出一套具干擾感知的排程方法，可有效提升網路效能。本方法分為三個部分，首先在允入控制階段盡可能選取高調變的連線，其次利用空間距離的分群概念提出TZG (Time Zone Grouping)方法，以逆時針的方式區分不同RS傳輸的時區，最後以調整分區內non-real time服務的頻寬需求，減少RS在access zone頻寬的浪費。我們利用NS2進行模擬實驗分析，驗證所提出的方法在利用分區傳送避免碰撞下，UGS的delay time相較於未分群的方法可有效改善約33%，ertPS可改善約29%，rtPS可改善約20%，而系統throughout相較於其他僅選擇最大access link的頻寬需求作為access zone大小的方法最多可提升約15.5%的效能。

As we know, there is Multi-hop Relay concept in standard of IEEE 802.16. But there are still many problems unsolved in WiMAX, so IEEE 802.16j propose a new station type, relay station, to extend signal coverage and improve the signal intensity which affected by shadow fading. Since there are many relay stations in the coverage of base station, data transmission and path routing become more complexity. At the same time, the transmissions become close, more interference and network congestion will decrease the efficiency of data transmission in the network.\nThis research proposes a frame scheduling with interference aware, which consist of three parts. First, we make the better modulation of links get higher priority; Second, we use concept of distance to proposed Time Zone grouping (TZG), which set RS into different group in counterclockwise way to reduce interference; Third, adjusting bandwidth allocation in access zone to decrease bandwidth waste in access zone. We implement our algorithm in NS2 simulator, the result shows that our method can improve delay of UGS about 33%, ertPS about 20%, rtPS about 20% than RTDS(Real time Distributed Scheduling ), and the system throughput can grow about 15.5% than the mechanism that just choose maximum requirement in access link of all BS/RS as access zone.