An Adaptive Power Saving Strategy Based on Traffic Load in the IEEE 802.16e Networks

[[abstract]]在傳統IEEE 802.16網路中，由Base Station (BS)與Subscriber Station(SS)來架構大範圍及高頻寬的都會型網路(MAN)，但其中SS卻無行動能力，因而可能無法滿足市場對無線寬頻存取服務更廣闊的需求，因此研究學者特別在新版的IEEE 802.16e的網路環境裡增加了SS的行動能力亦即為Mobile Subscriber Station(MSS)，希望能提供一個高速資料傳輸及支援高速移動的的無線寬頻環境。不過也因為MSS具備了移動能力，所以能源節省的策略也成為一個不可或缺的需求。 在IEEE 802.16e標準中的現有的標準能源節省機制，並無考慮網路流量負載，因此在不同網路流量負載下將會造成能源效能下降的缺點。例如：MSS使用IEEE 802.16e標準中的power saving Type1，在light load 時，buffer可能累積些許資料時MSS就要必須執行清除之動作，這樣會大大降低power efficiency ;而若使用 power saving Type 2，則將會因資料來的間隔常常無法大於idle time，所以將沒辦法進入sleeping mode。所以我們的論文中提出一種根據網路流量負載情形的能源節省機制，此種機制是在BS的暫存區定一個門檻值，讓資料累積到門檻值才讓MSS開始接收資料，並且試著透過掌握traffic pattern的流量來使MSS有較佳的power efficiency。而實驗結果也顯示我們所提出的機制能有顯著地提昇MSS的能源效率，並且面對資料流有延遲限制時，延遲時間依然能夠還在我們的控制範圍內。[[abstract]]In the traditional IEEE 802.16 networks, the wide range of MAN (Metropolitan Area Network) is composed of BSs (Base Station) and SSs (Subscriber Station). However, SSs have no mobility in the high speed transmission of IEEE 802.16 networks .To provide a solution, a new standard was proposed to increase the mobility of SSs in the IEEE 802.16e networks, called SS Mobile Subscriber Station(MSS).Nevertheless, due to the mobility of MSS, power saving becomes a necessary requirement. The classical power saving mechanism of IEEE 802.16e may cause some drawbacks about power efficiency in the different traffic. For example, under the power saving Type1 of IEEE 802.16e standard, MSS should wake up to receive the packets while the buffer accumulates a little packets. In this situation, it will decrease the power efficiency. The other case, under the power saving Type2, MSS might have a few chances not go to sleeping mode to save energy .Because the inter-arrival time is always smaller than the idle time. Due to the above situations, we propose a power saving scheme base on traffic load. The scheme is design a period time according to buffer reaching threshold for MSS in sleeping mode. The simulation result shows that the power efficiency in our power saving scheme is obviously superior than the classical power saving mechanism of IEEE 802.16e. Moreover, even if the traffic has delay bound, the delay time of traffic could be also controlled.[[note]]碩