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    题名: 無線通訊系統之移動與干擾分析
    其它题名: Analysis of mobility and interference in wireless communication system
    作者: 曾威傑;Tseng, Wei-chieh
    贡献者: 淡江大學電機工程學系碩士班
    李揚漢;Lee, Yang-han
    关键词: 換手;遲滯值;干擾;衰落;覆蓋率;Handover;Hysteresis;Interference;Fading;Overlapping
    日期: 2008
    上传时间: 2010-01-11 07:10:42 (UTC+8)
    摘要: 無線網路初期以固定式無線存取技術為主,隨著時代的進步,新規格不但支援可移動之通訊服務,更積極發展高速度下之行動通訊。然而行動台在移動時會受到基地台的干擾問題以及經由通道所接收到的各種衰落影響。除此之外,當行動台在系統中移動時,由於行動台與基地台距離發生變化,因此行動台所接收到的訊號會有所變動,當接收訊號越來越弱時,相對來說干擾也就越來越大。因此行動台想要維持好的服務品質就要使用換手技術,以確保資料能正常傳送,因此換手主要目的就是讓行動台不會因為移動而與基地台間之連線中斷。
    本篇論文的通道模型適用於發展高速無線通訊系統。在此模型中,行動台所接收到的訊號強度包含二種主要的通道模型,包括大範圍訊號衰減所產生的遮蔽衰落模型,和瑞雷衰落(Rayleigh fading)所產生的快速衰落模型,並且討論四種由基地台和行動台間所產生的干擾問題進行分析與討論。
    在換手的方式中,最主要的就是硬式換手與軟式換手二種方式。硬式換手藉由行動台與基地台間的訊號強弱來決策換手,並且使用遲滯值(Hysteresis)的方式來降低換手次數。在本篇論文中將討論行動台從時速六十公里上升至時速三百五十公里進行換手所發生的現象。藉由改變頻率重覆使用因子(reuse factor)、基地台間的覆蓋率(overlapping)和遲滯值的方式來降低換手次數並且提升系統效能。基於所設計的換手機制,我們藉由模擬許多的無線通道環境來描繪並發展出有效率的演算法。
    In the past the access of wireless network was mainly emphasized on the fixed mode transmission. As time goes by, new standards and their associated wireless communication networks have been designed and developed lately to support high mobility users. When a mobile moves around and through a series of base stations the user will receive signals not only from its serving and neighboring base stations but also from its surrounding radio environment so that the user’s received signal strength will encounter various kinds of fading and interference effects. Furthermore as the user moves its received signal strength from its serving base station may be degraded time to time and it needs to be handover to other base station to maintain its quality of communication and to avoid it from dropping of service.
    In this thesis a channel model that is suitable for use in the high mobility wireless communication system is developed. In this model the mobile received signal strength is formulated it consists of two parts one is the long range signal attenuation with the accumulation of lognormal scattering factor and the other part is the fast fading attenuation that is mainly contributed from the Rayleigh fading effect. Four kinds of interferences from its neighboring base stations are discussed and analyzed, their effect on the quality of service are reviewed.
    Hard and soft handoffs are considered in this thesis for mobile speed varying from low of 60 km/hr and up to 350 km/hr. The handoff phenomena and its effect on the system performance are widely discussed by varying the overlapping areas between base stations, the reuse factor, and the hysteresis value, i.e. the handoff threshold between the signal strengths of the serving and target base stations. Based on the handoff algorithm developed we have simulated many examples of the radio environments to depict the effectiveness of developed algorithm.
    显示于类别:[電機工程學系暨研究所] 學位論文

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