適用於IEEE 802.16j多重躍進中繼網路之流量感知路由演算法

Abstract

為了提升整體傳輸效能與擴展基地台原有的涵蓋範圍，IEEE 802.16中繼任務小組以既有的IEEE 802.16e為基礎來制定符合需求的IEEE 802.16j標準。此多重躍進中繼技術於網路環境內建置許多低成本的中繼台，以輔助基地台服務位於通訊死角或者原涵蓋範圍之外的使用者。然而使用此技術必須解決許多棘手的問題，其中之一便是基地台如何為使用者選擇適當的傳輸路徑。只依據訊號對干擾/雜訊比或是可支配的頻寬來做路徑選擇，中繼台容易產生附載不平衡的情形。附載不平衡造成無線資源使用效率低落，進而限制整體系統容量。因此，本篇論文提出一有效運用無線資源同時維持負載平衡的流量感知路由演算法。當基地台得知某中繼台負載過重，而鄰近中繼台擁有多餘的頻寬可以滿足使用者的連線需求，流量感知路由演算法避開較高負載以及經由較多中繼站的路徑來傳輸資料。模擬結果顯示在多重躍進中繼網路之中，使用此路由演算法允許使用者在相同時間內傳輸更多資料。將延遲時間維持在合理範圍的同時，在提升封包成功投遞率與系統整體傳輸率方面也有出色的表現。

The amendment of 802.16e has been released lately by IEEE 802.16 Relay Task Group j. For the sake of improving throughput and extension of cell coverage, relay stations (RSs) are deployed in the network. Intuitively, the base station (BS) selects a path for a target subscriber station (SS) according to Signal to Interference plus Noise Ratio (SINR) or the available bandwidth. However, it will lead to inefficient resource utilization and low system capacity since some RSs may have high traffic load whereas others may have redundant bandwidth. To tackle this problem, we propose a traffic-aware routing algorithm. By taking into account both resource utilization and load balance, our proposed scheme ensures that paths with heavy traffic load and long hop distance will not be selected while establishing the route. Simulations results demonstrate that, with the proposed traffic-aware routing algorithm, users are able to transmit more packets over the same period. Not only is the latency maintained in a reasonable range but also the throughput as well as packet delivery ratio are enhanced.