多重射頻多跳躍無線網狀網路下之空間再利用方法

Abstract

近來無線網狀網路已躍升為下一代無線網路的一項關鍵技術。無線網狀網路的空間再利用方法可允許多個傳輸通訊同時進行，因此可以大幅地增進整個網路的產量。然而無線網狀網路中的干擾問題是影響空間再利用的一個關鍵因素。在本篇論文中，我們提出了一個不需更改現有IEEE 802.11 MAC的程序機制 - RMP。RMP將無線網狀網路中的干擾問題列入考慮，並且利用事先指定好的傳輸方式來提高空間再利用。和現有的隨機存取方法不同的是，RMP使用了一個分散控制的存取方式來防止節點受到不必要的封包碰撞。RMP採用了可雙向傳輸的鏈狀拓撲，在此鏈狀拓撲中所有節點以等距離部署，使得各節點只能影響其前後兩個節點。模擬結果顯示就網路產量而言，RMP比Ripple [14] 高約30%，而比現有的IEEE 802.11 DCF高約200%。RMP不僅可達到比Ripple更高的產量，還可維持和Ripple一樣的傳輸延遲及傳輸品質。RMP對於CBR及FTP的流量皆可達到穩定的產量及較低的傳輸延遲時間。另外，RMP的設計簡單、部署容易，並且同時解決了在IEEE 802.11無線網路環境中無效率的backoff及碰撞問題。

Recently, wireless mesh networks (WMNs) have emerged as a key technology for next-generation wireless networking. Spatial reuse in a WMN can allow multiple communications to proceed simultaneously; thereby observably improve the overall network throughput. However, interferences between mesh nodes are a critical factor for maximizing the spatial reuse. In the thesis, we propose a novel scheduling mechanism without modifying the existing IEEE 802.11 MAC, called wireless Radio-Matching Protocol (RMP). It takes account of interferences in wireless environments to achieve maximum spatial reuse by using pre-specified radio transmissions. In contrast to existing random access approaches, RMP uses a decentralized controlled access approach to protect nodes from unintentional packet collisions. RMP adopts a chain topology of bidirectional transmissions, where nodes are equally spaced so that radios of non-neighboring nodes do not interference with each other. Simulation results indicate that the throughput of RMP is about 30% better than that of Ripple [14] and almost 200% better than that of the IEEE 802.11 DCF. Although RMP achieves higher throughput than Ripple, it still maintains the same delay time and transmission quality, as verified by our simulation results. RMP achieved a stable throughput and a low end-to-end transmission delay in both CBR and FTP traffic compared to the IEEE 802.11 DCF. In additions, RMP is simple, easy to implement, and it eliminates the back-off inefficiencies and the collision problem in IEEE 802.11 wireless environments.