行動寬頻網路之省電與資源管理

Abstract

近年來，無線寬頻存取越來越受歡迎，在所有的無線數據存取技術裡，IEEE 802.11無線區域網路提供一個簡單而且省錢的方式讓使用者可以自己建立他們的區域網路，而IEEE 802.16e無線都會網路則提供一個無線存取方案來替代目前以有線電纜作為最後一哩存取網際網路的方式。對於行動無線用戶而言，高速寬頻、服務品質保證、連續而無縫的網路存取、與無線終端設備的續航力一直都是在無線網路上的重要議題，本篇論文專注於行動寬頻網路之省電與資源管理，主要包括三項議題：第一項議題中，我們提出一個行動寬頻網路的架構，這個架構上的行動閘道器可以同時備配多個無線介面同時連上網際網路，藉著這樣的設計，可以提供一群行動用戶無線寬頻的存取服務；第二項議題中，我們討論在行動寬頻網路上的資源管理議題，思考如何分配無線資源以及如何管理使用者的移動使得正在進行中的資料流可以獲得品質服務保證並且連線不會中斷；最後，在第三項議題中，我們討論行動寬頻網路上省電管理的問題，針對行動閘道器和行動用戶裝備IEEE 802.16e無線介面的情況下，我們研究其省電類別管理問題。 在第一項議題中，我們發展了一個行動寬頻網路的架構以提供一群在行動網路中的行動用戶寬頻的無線存取以及網路的行動管理，這個行動寬頻網路的網路行動管理是藉由SIP (session initiation protocol)來達成的，而行動網路內的使用者則以行動隨意網路的方式在內部組成一個連結的網路，這個行動隨意網路透過一個網路內的行動閘道器存取網際網路，而行動閘道器上對內裝備了數個IEEE 802.11介面來與內部網路連結，對外則同時裝備了多個無線介面來存取網際網路，這些對外介面可以是IEEE 802.11、WiMAX、PHS、或者三代或三•五代的無線介面，藉著同時整合多種不同的無線介面來連結外部網路，內部行動用戶得以享有寬頻無線存取的服務。 在第二項議題中，我們首先利用SIP信令所夾帶的通話描述資訊設計通話允許控制以及資源管理機制，接著，考慮因為移動和無線頻道的多變性所產生的換手以及無線網路的多重速率調變，我們進一步對資源管理機制提出改善，觀察到現在的無線媒體控制層均支援服務品質機制和通話允許控制，對我們而言，整合應用層的服務品質資訊和媒體控制層的服務品質機制來設計一個跨層的資源管理機制是十分有吸引力的，所以我們設計了一考量換手和多重速率調變的跨層資源管理機制，在此機制中，當無線資源很擁擠的時候，我們可以藉由改變已存在的通話的編解碼和訊框速率動態的調整它們的資源的分配，這麼一來，不只是遭遇無線頻道品質劣化的通話其通話品質得以舒解，網路也可以接受更多的連線，除此之外，為了確保行動用戶的服務連續性，我們並且提出一個適用於包含認證加密機制的無線網路的無縫式換手機制。 在第三項議題中，我們針對的是IEEE 802.16e無線介面的省電類別管理問題，這個問題當行動用戶裝備的是IEEE 802.16e無線介面而且透過作為中繼傳播的行動閘道器連到網際網路時會發生，針對IEEE 802.16e，我們設計了四個省電類別管理演算法，四個演算法中，三個針對單一行動裝置的省電類別管理機制，一個則針對同時多個行動裝置的省電類別管理機制；對於單一行動裝置，IEEE 802.16e定義省電類別來管理它的睡眠，但是標準並沒有描述如何為資料流定義和管理省電類別，而現存的研究僅考慮所有的資料流中最小的延遲限制來規劃單一或多個行動裝置的睡眠。針對單一行動裝置，我們提出同時使用多個省電類別來規劃行動裝置的睡眠，每一個省電類別均考慮到資料流的特性，這麼一來，我們可以為行動裝置預備更準確的資源減少浪費並且使得行動裝置可以睡得更多；同樣的動機，對於多個行動裝置的情況，我們亦設計針對每個行動裝置的服務品質特性來安排他們的睡眠，如此一來可以節省更多的能源以及更有效率的運用頻寬。

In the recent years, wireless broadband access is gaining more popularity. Among all wireless data access technologies, the IEEE 802.11 WLANs (wireless local area networks) provide an easy and low cost solution for users to build their own local area networks while the IEEE 802.16 WMANs (wireless metropolitan area networks) provide a wireless solution to substitute the wire line last-mile Internet access. For mobile wireless users, high data rate, QoS (quality of service) guaranteed and continuous access, and long device operation time are always important issues for wireless networks. In this dissertation, we study the power and resource management in mobile broadband networks, which is composed of three major works. In the ‾rst work, we propose a mobile broadband network architecture which provides a group of mobile users broadband wireless access by attaching multiple wireless interfaces on the mobile gateway. In the second work, we discuss the resource management issue over the mobile broadband networks which considers how to manage wireless resource distribution and user mobility such that an on-going call can have guaranteed QoS and continuous connectivity. Finally, in the third work, we discuss the power management issue over the mobile broadband networks which studies the power saving class (PSC) management problem for the mobile gateway and mobile users which are equipped with IEEE 802.16e interfaces. In the first work, we develop a mobile broadband network architecture to provide broadband wireless access and support network mobility for a group of mobile users inside the network, where the mobility management is maintained by SIP (session initiation protocol). We propose to form a mobile ad hoc network (MANET) by a group of mobile stations (MSs). The MANET is connected to the outside world via a mobile gateway, which connects to the intra MANET by some IEEE 802.11 interfaces and attaches to the Internet through more external wireless interfaces (such as IEEE 802.11, WiMAX, PHS, and 3/3.5G interfaces). By aggregating multiple external interfaces of different wireless technologies in the gateway, mobile users are allowed to have a broadband wireless access. In the second work, we propose to design resource management mechanism by exploiting the session information carried by the SIP messages. Then, considering handoff and physical rate adaptation issues caused by mobility and wireless channel variation, we further enhance the resource management mechanism. Observing that current wireless MAC protocols all support QoS and CAC (call admission control), it is attractive to us to design a cross-layer resource management mechanism by integrating the QoS information from the application layer and the QoS mechanisms supported by the MAC layer. The proposed cross-layer scheme takes handoff and multi-rate environment into consideration. When wireless resource is stringent, we can dynamically adjust the resource distribution among existing calls by controlling their supporting codecs and frame rates. This not only takes care of calls in bad channel conditions, but also can accept more calls. In addition, to maintain continuous network continuity during handoff, we also develop a seamless post-handoff mechanism for secured wireless networks. In the last work, we focus on the PSC management problem for IEEE 802.16e interfaces. This issue happens to the mobile broadband networks when the mobile gateway acts as an IEEE 802.16 relay and the mobile users are equipped with IEEE 802.16e interfaces to access the Internet via the gateway. In this part, we propose four PSC management algorithms for IEEE 802.16e wireless networks. In the four schemes, three consider a base station (BS)-MS pair, one refers to multiple MSs under a BS. For each individual MS, IEEE 802.16e defines PSCs to manage its sleep. However, the standard does not describe how to define and manage PSCs for flows. Existing works all consider only the strictest delay bound among flows to control the sleep of single or multiple MSs. Therefore, for single MS, we propose to use multiple PSCs to schedule the sleep of the MS such that the sleep schedule can more accurately capture the QoS of flows and make the MS sleep more. Based on the same motivation, for multiple MSs, we also propose to schedule each MS's sleep according to each of their QoS characteristics. These lead to less energy consumption, more efficient use of bandwidth, and more compact listening windows.