| dc.description.abstract | 本論文主要在探討WiMAX的行動節點(Mobile Station, MS)在已經進入休眠模式(Sleep mode)的狀態下,處於休眠週期(sleep window)的期間,逐漸離開原本serving WiMAX基地台(Base Station, BS)的信號範圍,移動至另外一個BS的信號範圍,原本serving BS有資料要傳給MS,會因為只有原本serving BS本身知道有資料要傳給MS,在無法叫醒該MS的狀況,新的BS又不知道有資料要傳給MS,就會發生封包遺失(Packet loss).
所以本論文提出MS還在Sleep mode,整合空閒模式(Idle mode),我們建議當MS發現原本serving BS的信號已經逐漸微弱,且原本serving BS沒有資料要給該MS時,不直接進行換手(Handover),而改變為MS直接進入idle mode,其優點為可以省去handover的流程,且handover的進行必須回到正常運作的狀況,讓MS進入sleep mode可以省電的好處失去,且MS在idle mode下,因為傳呼群組(paging group)的範圍比BS的服務範圍要大上許多,便不會有MS換至另外一個BS所造成packet loss產生,但是因為Idle mode的傳呼無用期間(paging unavilable interval)比sleep window長很多,所以會造成封包有很長的延遲.
我們會針對本論文所提出的MS sleep mode整合idle mode的方式,與原本單純的sleep mode,模擬在不同的BS packet buffer、不同的流量packet發送情況下和MS的移動頻繁率,來觀察packet的loss rate與delay狀況,且進行分析與比較,整合idle mode比單純sleep mode在packet loss改善很多,不過也packet delay也增加很多.所以此方式很適合NRT、BE的應用,尤其是當MS移動率高的時,整合idle mode的packet loss 的改善更具效果.
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| dc.description.abstract | This paper discusses the phenomenon of Mobile Station(MS) in WiMAX network when it handovers during sleeping period , We suggested that when the serving BS signal is becoming weak gradually, the serving BS will inform the MS at its listening frame, to enter idle mode if BS does not have packet to transmit to this MS at that moment. The proposed approach simplifies the handover procedure of MS when it is in sleeping mode and can prevent MS losses connection when it moves out the original serving BS during sleeping period. Generally, in idle mode, the paging coverage is much wider than a single BS , and the paging interval could much longer than the sleeping interval.
Thus, the MS with non real time (NRT) or best effort services can save power when it enters idle mode. The data forwarding from the original serving BS to current BS is adopted when the MS wakes up to receive paging information and is informed for receiving data. However, additional delay is introduced during data forwarding. This research investigates the performance of packet loss, delay, and sleeping efficiency of the proposed scheme through exhaustive simulations. The simulation results show that the proposed integrated sleep/idle scheme achieves better performance than the traditional sleeping mode only scheme.
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