【正文】 量升高，那數(shù)據(jù)包延遲個數(shù)就會下降，反之一樣。本文首先介紹了隨機(jī)多址接入?yún)f(xié)議的研究背景及主要成果，從常用的網(wǎng)絡(luò)參考模型入手，對目前廣泛研究的純ALOHA 協(xié)議、時隙ALOHA 協(xié)議、非持續(xù)性CSMA 協(xié)議進(jìn)行了詳細(xì)闡述，具體分析了這三種協(xié)議的基本原理、系統(tǒng)吞吐量、平均傳輸時延等性能指標(biāo)，然后基于Matlab 平臺進(jìn)行建模仿真，對所得數(shù)據(jù)進(jìn)行了分析，進(jìn)而比較得出不同類型的多址系統(tǒng)的優(yōu)缺點(diǎn)，為提高協(xié)議性能提供了參考。隨著音頻、視頻等多媒體業(yè)務(wù)的普及，以及工業(yè)應(yīng)用方面等的特殊要求，使得傳統(tǒng)的ALOHA 和CSMA 協(xié)議逐漸顯得有些捉襟見肘，尤其是在無線局域網(wǎng)方面的CSMA/CA 系統(tǒng)，目前人們對無線網(wǎng)絡(luò)的呼聲也越來越高，當(dāng)然對網(wǎng)絡(luò)質(zhì)量的要求也是越來越苛刻。吳老師嚴(yán)謹(jǐn)?shù)闹螌W(xué)態(tài)度、淵博的學(xué)識、刻苦專研的科研精神和兢兢業(yè)業(yè)的工作態(tài)度都給我留下了深刻的印象，將對我以后的學(xué)習(xí)和工作產(chǎn)生深遠(yuǎn)的影響。感謝物理與電信工程學(xué)院及里通信學(xué)院的老師們的指導(dǎo)和幫助！最后，感謝我的父母和家人，他們殷切的期望是我不斷進(jìn)取的動力，他們在各方面都給予了我最無私的幫助和支持，同時，也感謝所有關(guān)心和幫助過我的同學(xué)和朋友們！參考文獻(xiàn)[1] of Metropolitan Area .[2]徐洋,:合肥出版社,.[3]范謙, .[4]:電子工業(yè)出版社,.[5]王申濤,楊浩,.[6]:人民郵電出版社,.[7]佘明輝,.[8] .[9] CSMA ,.[10] :重慶大學(xué)碩士學(xué)位論文,.附錄A：RESEARCH OF CELLULAR WIRELESS COMMUNATION SYSTEMAbstract Cellular munication systems allow a large number of mobile users to seamlessly and simultaneously municate to wireless modems at fixed base stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to bandsmen, or to a waveband microwave link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public Switched Telephone Network (PSTN). Similarly, munications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or spatial division multiple access (SDMA).1 IntroductionA wide variety of wireless munication systems have been developed to provide access to the munications infrastructure for mobile or fixed users in a myriad of operating environments. Most of today’s wireless systems are based on the cellular radio concept. Cellular munication systems allow a large number of mobile users to seamlessly and simultaneously municate to wireless modems at fixed base stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to bandsmen, or to a waveband microwave link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public Switched Telephone Network (PSTN). Similarly, munications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or spatial division multiple access (SDMA) .Wireless munication links experience hostile physical channel characteristics, such as timevarying multiparty and shadowing due to large objects in the propagation path. In addition, the performance of wireless cellular systems tends to be limited by interference from other users, and for that reason, it is important to have accurate techniques for modeling interference. These plex channel conditions are difficult to describe with a simple analytic model, although several models do provide analytic tractability with reasonable agreement to measured channel data . However, even when the channel is modeled in an analytically elegant manner, in the vast majority of situations it is still difficult or impossible to construct analytic solutions for link performance when error control coding, equalization, diversity, and network models are factored into the link model. Simulation approaches, therefore, are usually required when analyzing the performance of cellular munication links.Like wireless links, the system performance of a cellular radio system is most effectively modeled using simulation, due to the difficulty in modeling a large number of random events over time and space. These random events, such as the location of users, the number of simultaneous users in the system, the propagation conditions, interference and power level settings of each user, and the traffic demands of each user,bine together to impact the overall performance seen by a typical user in the cellular system. The aforementioned variables are just a small sampling of the many key physical mechanisms that dictate the instantaneous performance of a particular user at any time within the system. The term cellular radio system,therefore, refers to the entire population of mobile users and base stations throughout the geographic service area, as opposed to a single link that connects a single mobile user to a single base station. To design for a particular systemlevel performance, such as the likelihood of a particular user having acceptable service throughout the system, it is necessary to consider the plexity of multiple users that are simultaneously using the system throughout the coverage area. Thus, simulation is needed to consider the muftiuser effects upon any of the individual links between the mobile and the base station.The link performance is a smallscale phenomenon, which deals with the instantaneous changes in the channel over a small local area, or small time duration, over which the average received power is assumed constant . Such assumptions are sensible in the design of error control codes, equalizers, and other ponents that serve to mitigate the transient effects created by the channel. However, in order to determine the overall system performance of a large number of users spread over a wide geographic area, it is necessary to incorporate largescale effects such as the statistical behavior of interference and signal levels experienced by individual users over large distances, while ignoring the transient channel characteristics. One may think of linklevel simulation as being a vernier adjustment on the performance of a munication system, and the systemlevel simulation as being a coarse, yet important, approximation of the overall level of quality that any user could expect at any time.Cellular systems achieve