Abstract
因為頻寬是一非常有限的資源,所以頻譜效率對於設計蜂巢式行動通訊系統是極為重要的.因此,如何有效的應用有限的頻寬是一項非常具有挑戰性的工作.現今的蜂巢式行動通訊系統大多採取固定頻道分配技術.在本論文中,首先分析使用固定頻道分配技術的性能.對於已通話,如果他們需要換頻道時,我們設定系統優先處理這些需求.共有二種優先的方法.一是讓其排隊等待,另一是系統保留固定的頻道供其使用.結果顯示,如果有優先順序存在時,已進行的通話被強制中斷的機率將遠小於新使用者打不通的機率.眾所皆知,扇形化可減少同頻率基地臺干擾的數目.但如果分析系統的頻譜效應是根據對通話被強制中斷的機率和使用者打不通的機率來各定其最低下限時,若系統設計不良,我們發現扇形化系統的頻譜效率可能會比未扇形化系統的頻譜效率差.最後,系統使用最佳化動態頻道分配技術--最大化填色方法--的性能是經由計算機模擬產生.同樣的,若已通話有較高優先順序時,在大多數進入系統通話率相同的情況下,使用最大化填色方法的系統其已進行通話被強制中斷的機率和新使用者打不通的機率將遠低於其他使用固定頻道分配技術的系統.在本論文中,第一章為簡介.第二章將對已存在在文獻中討論使用固定頻道分配方法與動態頻道分配方法系統作個總灠.第三章分析使用固定頻道分配方法的性能.第四章將討論扇形化方法對頻譜效率的影響.第五章討論使用最佳化動態頻道分配方法系統性能.最後在第六章作個總結.Spectrum efficiency is of vital importance in designingcellular mobile communication systems since bandwidth is a verylimited resource. Hence how to effectively use the availablebandwidth is a challenging task. The method of fixed channelassignment (FCA) have been widely adopted in current mobilephone systems. In this thesis, performance analysis of cellularsystems employ- ing FCA is first studied. Two priority schemesfor handoff calls are considered: one is adding queue and theother is reserving a fixed number of channels. Results obtainedshow that if priori- ty schemes exist for handoff calls, theforced termination proba- bility will be much lower than he newcall blocking probability. Sectorization has been well-knownfor reducing the number of co- channel cells. Our analysis onspectrum efficiency based on diff- erent constraints on the newcalls blocking and forced terminati- on probability, show that,however, if not properly designed, the sectored system might beworse than the system without sectori- zation. Finally, theperformance of systems using the optimum DCA method, the``maximumm packing''(MP) strategy, is analyzed by computersimulation. Again higher priority for handoff calls isconsidered. Results obtained show that tthe new call blockingprobability and forced termination probability of systems usingthe MP strategy will be smaller than those of systems employingthe FCA method under most all of the interesting new callarrival rates.