於IEEE 802.16e行動網路使用賽局理論提出基於使用率之換手連線演算法

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2011

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IEEE 802.16e為可實現的4G通訊協定,當中之重要應用如:WiMAX(Worldwide Interoperability for Microwave Access) 全球互通微波存取,根據IMT-A所規劃,未來4G通訊達成的網路功能需包含:高速上/下傳、更好的頻寬使用率、更佳的封包傳輸能力於行動通訊,WiMAX無線技術由於可提供以上要求,而被視為4G通訊協定的主要競爭者其一。IEEE 802.16e標準所制定的技術規格,針對即時與非即時通訊提供不同傳輸參數,進一步實現封包傳輸的QoS(Quality of Service),提高頻寬使用率與使用者的滿意度。IEEE 802.16e的MAC層(Medium Access Control),基地台(Base Station)可判斷連線對應的訊務流類別,同時運行系統的允入控制(Connection Admission Control),允入機制可估計系統整體容量,並且給予允入之連線適如其分的服務品質。對於不同類型的訊務流(service flow), 802.16e採取多樣的方式實現,除了區分傳輸的優先順序(High- and Low-Priority) 如:保證式(UGS : Unsolicited Granted Service)與盡力式 (BE ; Best Effort)服務,另有較為複雜的輪詢服務(PS ; Polling Service) 。輪詢概念介於固定分級與隨機傳輸,可依訊務流所搭配之服務再分為:延展式即時輪詢(ertPS ; Extended Real-Time Polling Service)、即時輪詢(rtPS ; Real-Time Polling Service)、非即時輪詢(nrtPS ; Non Real-Time Polling Service)三種。此外,IEEE 802.16家族協定以開放式架構呈現資源分配議題,ISPs(Internet Service Providers)業者可依標準協定自行設計、增加部分系統內容,改善資源使用效率,以滿足其屬用戶。如今,多數研究皆著眼有限的頻寬分配於即時與非即時串流,用戶區分則取自新進與現存用戶之討論,缺乏對換手連線用戶頻寬請求之單一論述。現有作法於換手連線,採取預留的方式,於總體頻寬中分割一部分,做為服務換手連線之用。此方式的優點為簡單、易實現,但缺點則為彈性不足,無法應付使用者不同需求的比例,如:定點連線遠用戶遠少於換手連線用戶,則固有做法會嚴重影響頻寬使用效率,反之若換手連線用戶數量微乎其微,被預留下的頻寬形同浪費,傷害系統整體的效率。本研究提出「換手與新進用戶置於同一水平探討」的概念,嘗試找出適合換手連線用戶的使用率方程(Utility Function)與新進用戶比較,最後引用賽局理論的納許議價均衡解(Nash Bargaining Solution)為演算法核心,設計新概念的智慧型頻寬分配機制。
The IEEE 802.16e a.k.a. mobile WiMAX (Worldwide Interoperability for Microwave Access) network has been implemented as one of the options for 4th generation mobile communication system. According to the criteria of IMT-A, the 4G communication in the future must achieve: high-speed uplink / downlink transmission, better bandwidth utilization, better transmission capacity, and higher mobility. The mobile WiMAX network technology can provide above requirements, thus it comes to be a major competitor in the 4G network technology standard. Follow the technique specification of the IEEE 802.16e, real and non-real time traffics are classified by different transmission parameter to enhance the resource efficiency and satisfaction of clients. To implement QoS (Quality of Service) in the packet switch transmission, the MAC layer of IEEE 802.16e could distinguish the type of service flow and operate the CAC (connection admission control) in the base station (BS), which could be used to estimate the capacity of the whole system. By the way, the BS would apply an accurate QoS for admitted connections. The IEEE 802.16e-based network system has adopted various ways to execute the demands of different service flow. It is provided with a traditional high- and low-priority methods: unsolicited granted service (UGS) and BE (Best Effort). Beside that there are more complex methods such as polling services: ertPS (Extended Real-Time Polling Service), rtPS (Real-Time Polling Service), nrtPS (Non Real-Time Polling Service) for diversity. In these days, the studies on the collation of service are between new incoming and existing users, but lack for the description of handoff users. The current method applied bandwidth reservation for handoff connection in the radio coverage. The advantages of this way are simple and practical. On the other hand, this is an inflexible method for dynamic network scenario. The total efficiency of the system maybe over or under estimated, no matter which condition happened it would harm the performance of the whole network. In this research, we analyzed the associations among handoff, real and non-real time connections. After that we derived some integrated variables from bandwidth requests for diverse handoff connections. Besides that we proposed a QoS-aware utility function for handoff users. A QoS-aware utility function can help the handoff user to indicate its requirements accurately. At last, we build up a new algorithm for resource allocation by the Nash bargaining solution (NBS). The proposed algorithm estimates the load of the system by the minimum utility rather than the minimum bandwidth. The simulation results show that the algorithm could fully use the system by pulling up the system capacity.

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IEEE 802.16e, WiMAX, 服務品質, 連線允入控制, 動態頻寬分配, 賽局理論, IEEE 802.16e, WiMAX, quality of service, connection admission control, dynamic bandwidth allocation, game theory

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