IEEE 802.16e行動WiMAX網路之省電類別管理

Abstract

IEEE 802.16e標準被制訂用來提供都會網路中的行動寬頻無線網路存取，行動性意謂了電源管理在行動用戶端 (Mobile Subscriber Station, MSS)的重要性。IEEE 802.16e中定義了三種省電類別 (power saving class, PSC)，一個資料流 (traffic flow) 可以和一個省電類別作關聯。然而，從行動用戶端的角度來看，標準並未定義當有多個資料流時，哪些要被放在同一個省電類別中，以及在一個行動用戶端中，多個省電類別要如何相互配合運作，來達到更好的能源效率 (energy efficiency)。同時，也要解決如何決定省電類別的參數，像是起始訊框 (start frame)、聆聽視窗 (listening window) 大小、睡眠視窗 (sleep window) 大小，以及如何保證當多個省電類別存在時，服務品質 (Quality of Service, QoS) 能夠被維持。在本篇文章裡，我們提出了一個新穎的 “交疊及解多工” 方式，利用了type I和type II兩種省電類別，為IEEE 802.16e的網路提出了上述問題的解決方法。給定一組同一行動用戶端中的資料流，我們的方法首先試著為每個資料流制定出一個省電類別，以滿足各自的服務品質需求，然後我們會將它們交疊在一個很長的序列中，以計算總頻寬需求 (bandwidth requirement)。最後，我們會將這個序列解多工 (demultiplexing) 成多個省電類別，每一個用來支援一或多個資料流。此方法最後可達到高能源效率且能滿足每個資料流的服務品質需求。

The IEEE 802.16e standard has been defined to provide mobile broadband wireless access in metropolitan areas. Mobility implies the importance of power management at the Mobile Subscriber Station (MSS) side. In IEEE 802.16e, three types of power saving classes (PSCs) are defined. A traffic flow can be bound to a PSC. However, from an MSS's point of view, it does not define how multiple flows should be put into one PSC and how multiple PSCs of an MSS should cooperate with each other for better energy efficiency. At the same time, it needs to answer how to determine the parameters of each PSC, such as start frame, listening window size, and sleep window size, and how to guarantee QoS of traffic flows when multiple PSCs coexist. In this paper, we propose a novel ``fold-and-demultiplex'' method for an IEEE 802.16e network with PSCs of type I and type II. Given a set of traffic flows in an MSS, our method first tries to give each one a PSC satisfying its QoS requirement. Then we fold them together into one long series so as to calculate the total bandwidth requirement. Finally, we demultiplex the series into multiple PSCs, each supporting one or multiple flows. This ends up with high energy efficiency for MSSs while meeting flows' QoS requirements.