IEEE 802.16相關標準已經發展出像是已經成熟的802.16d、支援移動性的802.16e還有支援Multihop Relay (MR)的802.16j。802.16j的特點就是多了可以轉傳資料的Relay Station (RS)，藉由RS可以擴大網路覆蓋範圍(coverage extension)並提升系統傳輸效能(throughput enhancement)，不過也因此使得802.16j的topology不同於以往，變成類似Tree的架構，傳輸路徑也不再是單純的single hop，有可能變成two hop甚至multihop的方式，也因此產生了新的多重路徑(multipath)問題：BS和MS中間的路徑不再唯一，因此路徑也需適時的配合改變，否則可能會嚴重的影響效能。 本文以連線的QoS（Quality of Service）要求為標準，依照系統中delay需求順序建立連線BS與RS間的連線，最後建構出系統的tree topology並依此進行傳送。目的在讓高QoS連線與BS間的Hop數降低，達到降低delay並穩定jitter的目標，並提供congestion control。最後利用NS-2網路模擬器對不同的網路環境進行模擬，測試所產生的效能並進行評估，以驗證此方法的實際可行性。

<p>In the past 10 years, the bandwidths and processing capabilities of the networks have increased dramatically. The number of real-time applications using these networks has also increased. The large number of real-time packets might, in a switched multi-hop network, lead to unpredictable traffic patterns. This is not a problem when the traffic intensity is low, but if the same network is used by a large number of users simultaneously, the overall performance of the network degrades. In fact, unpredictable delays in the delivery of the message can adversely affect the execution of the tasks dependent on these messages, even if we take into account the soft real-time performance.</p><p>In this paper, we investigate the effect of traffic shapers on soft real-time performance. We will consider a switched multi-hop network with FCFS queues. We will implement two versions of the network simulator. One version will be without traffic shaper and the other version will use a traffic shaper. By comparing the results (for average delay, deadline miss ratio etc.) from both the versions, we will try to conclude if it is really beneficial to use traffic shapers for soft real-time performance. Leaky bucket and token bucket algorithms are the most popular ones for traffic shaper implementation. We will consider leaky bucket algorithm for our analysis. We analyse different versions of the leaky bucket and present the trade-off’s involved.</p>

In the past 10 years, the bandwidths and processing capabilities of the networks have increased dramatically. The number of real-time applications using these networks has also increased. The large number of real-time packets might, in a switched multi-hop network, lead to unpredictable traffic patterns. This is not a problem when the traffic intensity is low, but if the same network is used by a large number of users simultaneously, the overall performance of the network degrades. In fact, unpredictable delays in the delivery of the message can adversely affect the execution of the tasks dependent on these messages, even if we take into account the soft real-time performance. In this paper, we investigate the effect of traffic shapers on soft real-time performance. We will consider a switched multi-hop network with FCFS queues. We will implement two versions of the network simulator. One version will be without traffic shaper and the other version will use a traffic shaper. By comparing the results (for average delay, deadline miss ratio etc.) from both the versions, we will try to conclude if it is really beneficial to use traffic shapers for soft real-time performance. Leaky bucket and token bucket algorithms are the most popular ones for traffic shaper implementation. We will consider leaky bucket algorithm for our analysis. We analyse different versions of the leaky bucket and present the trade-off’s involved.