無線中繼式接取網路的規畫與品質最佳化之研究

Network planning and performance optimization for wireless relay networks

盧曉珍(Hsiao-Chen Lu)

指導教授 ： 廖婉君

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.02881

摘要

利用中繼台來支援多段式傳輸將是未來4G通訊系統的主要趨勢之一。一般認為,將中繼台整合至無線接取網路的架構中可帶來增加網路覆蓋度與增進網路吞吐量的好處,但這也衍生了技術上的新挑戰。如何讓中繼台在無線接取網路的架構下順利運作,並且發揮最大的效益,將是網路規畫者的一大課題。
本論文主要探討的是,整合中繼台到無線接取網路過程中會遇到的數個關鍵問題。對行動網路業者而言,首要解決的問題是如何佈建網路。我們分析了不同種類的中繼台與基地台,其佈設的位置、數量對效能的影響,並且考慮了二種不同的網路佈建狀況下,分別該如何決定設置何種基台,以及基台的位置,使在有限的預算下佈設的網路容量能最大化。
然而,獨立運作的中繼台,對網路效能的提升相當有限。為克服此問題,我們提出中繼台合作傳輸的概念,並分析此做法對中繼台的覆蓋度及吞吐量的增益。透過數學模型分析,我們提出一套既可決定中繼台的合作傳輸方式,亦可決定使用者的資源分配的方法,可以最大化網路容量且兼顧使用者的公平性。同時,我們也探討中繼台的佈放方式對其合作傳輸效率的影響。
最後,我們探討在利用網路編碼支援多重播送的狀況下,如何選擇適當的中繼台與適當的傳輸速率進行傳輸。我們提出一套可以精確描述傳輸過程中網路狀態的數學模型,並透過此模型設計了可找到最佳傳輸方式的動態規畫演算法、以及另外二種低複雜度的次佳演算法。
綜觀以上問題,皆是在佈建次世代4G通訊系統時會遇到的核心問題。我們相信本論文中的問題分析,以及所提出的解決方法與實驗結果的觀察,將是4G系統佈建規畫時不可或缺的指引。

關鍵字

無線中繼式網路 ； 網路規畫 ； 最佳化

並列摘要

Integrating relay stations (RSs) into the architecture of centralized wireless access networks to support multi-hop relaying has become a major trend for 4G wireless communication systems. Though commonly believed that RSs can effectively extend the coverage and enhance throughput of a network, integrating RSs into the system can bring as many challenges as benefits. Much more sophisticated network planning is required to make full use of RS’s functionality and to optimize the performance of a relay-assisted wireless access network.
In this dissertation, we study several critical issues for wireless relay networks. The first is the network deployment problem. We analyze the impacts of deployment locations on system performances for different types of network nodes. Considering different deployment scenarios and user distributions, we propose deployment strategies determining which types of stations should be deployed and their deployed locations, under a budget constraint. Due to the capacity limitation at each relay station, simply having each relay station independently relay traffics for their serving base station can only achieve limited performance gain, which motivates us to propose the concept of relay station cooperation. The second problem we studied is therefore how to coordinate relay stations to cooperatively serve the downstream users such that system capacity can be maximized without sacrificing fairness. Through analyzing the impacts of relay cooperation on its coverage and downstream rate, we have mathematically formulated this problem, and propose joint relay cooperation and resource assignment solution. The effect of relay station placement on the performance of relay station cooperation is also studied. The last problem tackled is how to select data forwarding strategies for relay stations when network coding is enabled for multi-cast data repair. We propose a Markov decision process to characterize the data forwarding process, by which a delay-optimal dynamic programming algorithm as well as two light-weight on-line heuristics are derived. To summarize, several critical issues induced when integrating relays into a wireless access network are studied in this dissertation. We believe that our analysis and observations are indispensible for the planning and performance optimization of next generation wireless relay network.
Integrating relay stations (RSs) into the architecture of centralized wireless access networks to support multi-hop relaying has become a major trend for 4G wireless communication systems. Though commonly believed that RSs can effectively extend the coverage and enhance throughput of a network, integrating RSs into the system can bring as many challenges as benefits. Much more sophisticated network planning is required to make full use of RS’s functionality and to optimize the performance of a relay-assisted wireless access network.
In this dissertation, we study several critical issues for wireless relay networks. The first is the network deployment problem. We analyze the impacts of deployment locations on system performances for different types of network nodes. Considering different deployment scenarios and user distributions, we propose deployment strategies determining which types of stations should be deployed and their deployed locations, under a budget constraint. Due to the capacity limitation at each relay station, simply having each relay station independently relay traffics for their serving base station can only achieve limited performance gain, which motivates us to propose the concept of relay station cooperation. The second problem we studied is therefore how to coordinate relay stations to cooperatively serve the downstream users such that system capacity can be maximized without sacrificing fairness. Through analyzing the impacts of relay cooperation on its coverage and downstream rate, we have mathematically formulated this problem, and propose joint relay cooperation and resource assignment solution. The effect of relay station placement on the performance of relay station cooperation is also studied. The last problem tackled is how to select data forwarding strategies for relay stations when network coding is enabled for multi-cast data repair. We propose a Markov decision process to characterize the data forwarding process, by which a delay-optimal dynamic programming algorithm as well as two light-weight on-line heuristics are derived. To summarize, several critical issues induced when integrating relays into a wireless access network are studied in this dissertation. We believe that our analysis and observations are indispensible for the planning and performance optimization of next generation wireless relay network.

並列關鍵字

wireless relay networks ； network planning ； optimization

參考文獻

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