多層無線通訊網路上之資源管理策略; Strategies for Resources Management in Multi-tier Wireless Communication Networks

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/8419

Title:	多層無線通訊網路上之資源管理策略;Strategies for Resources Management in Multi-tier Wireless Communication Networks
Authors:	林國珍;Kuo-Jen Lin
Contributors:	資訊工程研究所
Keywords:	需求遺失機率;巨細胞;微細胞;重找路徑問題;尋徑;需求阻斷率;軟換手;預留連結;通道分享;資源管理;無線通訊網路;call blocking probability;microcell;soft handoff;macrocell;wireless communication networks;routing;resource management;channel-sharing;call loss probability;rerouting;connection reservation
Date:	2004-06-14
Issue Date:	2009-09-22 11:26:29 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	為了提供無線通訊激烈增加的需求，多層無線通訊網路之資源管理成為重要的研究課題。多層的無線通訊網路是由多個細胞(cell)及行動通訊者重疊涵蓋相同服務區域所組成。此種重疊的特性，可以讓通訊負載透過多層細胞通道的分享及行動通訊者的中繼協助來提昇系統的效能。在本篇論文中，我們提出兩種通道分享(channel-sharing)策略稱為垂直通道分享策略(vertical channel-sharing)及垂直水平通道分享策略(vertical-horizontal channel-sharing)來有效利用雙層細胞間可用的通道，透過分析及模擬結果顯示需求遺失機率(call loss probability)有了大幅的改善。這雙層細胞為涵蓋大範圍的巨細胞(macrocell)與涵蓋小範圍的微細胞(microcell)重疊涵蓋區域所組成。在連結導向服務的雙層無線網路中，資料傳輸需考慮到重找路徑問題(rerouting problem)。為了提供無間隙的換手(seamless handoff)和無延遲的傳輸，我們提出一種交叉型的雙層無線網路新架構。在這架構下，可以減少硬體佈線的成本。同時我們提出慵懶型預留(lazy reservation)及積極型預留(aggressive reservation)來減低預留連結(connection reservation)的佔用數。模擬結果顯示我們的方法減少了許多連結數及降低需求中斷機率。在WCDMA的系統中，軟換手(soft handoff)用於使用者處於細胞邊界時維持收訊品質的機制。一般的作法是使用MRC(maximal ratio combining)的方法將各個處於active set的細胞做組合，但是此方法相當耗用資源，於是有GSC(generalized selection combining)的方法出現，採用active set中最大的K個細胞做組合，但是收訊品質降低。在本篇論文中，我們提出ASC(adaptive selection combining)的方法同時考慮通道的使用及品質的維持，彈性交換使用MRC及GSC，調整細胞的組合,來達到高通道使用率極高品質的維持。模擬結果顯示，需求阻斷率(call blocking probability)比MRC高而品質比GSC高與MRC相當。最後我們寬頻尋徑(broadband routing)的方法運用於WCDMA網路及Ad Hoc網路的結合環境中，利用IEEE 802.11的較高頻寬做為中繼網路，讓較低訊號雜訊比的使用者可以藉由Ad Hoc網路並使用多個下傳路徑來改進傳輸速率，充分使用細胞內的資源，模擬結果顯示，所提的線條式路徑(linear-path routing) 、樹狀路徑(tree-based routing) 及區域廣播路徑(local-broadcast routing)均相當優於傳統下傳的結果。 To support the drastically increased demand for wireless communications, the resource management of multi-tier wireless communication networks becomes an important issue. A multi-tier wireless communication networks is characterized by multiple cells and some mobile hosts overlapping in the service area. This overlapping property provides an advantage that traffic loads can be shared by channels of multiple tiers or supports high data rates by forwarding data with mobile hosts to increase the performance of the system. In this dissertation, we propose several strategies in multi-tier wireless communication networks to increase resource utilization. Two channel-sharing strategies namely vertical channel-sharing and vertical-horizontal channel-sharing are proposed to better utilize channels for two-tier cellular networks. The call loss probability of new calls and call dropping probability of handoff calls are developed through analyses and simulations. The results justify the advantage of our strategies over existing strategies. The data transmission of connection-oriented services considers the rerouting problem in two-tier wireless networks for supporting seamless handoff and delay-sensitive transmission. We propose a new cell structure by interleaving the connections from mobile switching centers (MSCs) to microcells. This structure can effectively extend the physical area that can be covered by a MSC. Based on this structure, we show that connections can be reserved in a lazier manner. This lazy approach can reduce the number of times that a mobile subscriber switches between different MSCs due to mobility, and reduce the number of unnecessary connections reserved to support seamless handoff, and conserve network bandwidth for connection rerouting, at the cost of more vertical handoffs. In addition, such a cell structure can also reduce the hardware wiring cost. In WCDMA cellular networks, soft handover is supported at cell boundaries to maintain communication quality. The maximal ratio combining (MRC) and generalized selection combining (GSC) [1, 2] are two possible approaches. However, soft handover is resource-intensive. We propose an adaptive selection combining (ASC) scheme to manage the cell resources that can switch flexibly between MRC and GSC so as to take care of both channel loading and communication quality. The signal-to interference and noise ratio (SINR) is kept as high as that of MRC while the blocking probability can remain at about the same level as that of GSC. For supporting wireless broadband Internet services, an environment unified WCDMA cellular networks and ad-hoc networks is considered to enhance the broadband services and efficiently use the WCDMA resources. Three broadband routing protocols are proposed to increase the downlink transmission rates from WCDMA cellular networks and to decrease the route breakage probability. The contribution of broadband routing is twofold. First, such broadband routing service could be very attractive to highly mobile users. Second, we propose several promising multi-downlink routing protocols that are particularly suitable for WCDMA systems. Simulation results are presented to justify the effectiveness of the proposed routing protocols.
Appears in Collections:	[Graduate Institute of Computer Science and Information Engineering] Electronic Thesis & Dissertation

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