【正文】 6) Each kind of work tends the fusion. The understanding, grasps these tendencies has the vital practical significance to the mobile munication operator and the equipment manufacturer. 3 Research of cellular wireless mination system summarize A 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 baseband, or to a wideband 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 multipath 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 analytical model, although several models do provide analytical 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 analytical solutions for link performance when error control coding, equalization, diversity, and work 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 multiuser 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 high capacity (., serve a large number of users) by allowing the mobile stations to share, or reuse a munication channel in different regions of the geographic service area. Channel reuse leads to cochannel interference among users sharing the same channel, which is recognized as one of the major limiting factors of performance and capacity of a cellular system. An appropriate understanding of the effects of cochannel interference on the capacity and performance is therefore required when deploying cellular systems, or when analyzing and designing system methodologies that mitigate the undesired effects of cochannel interference. These effects are strongly dependent on system aspects of the munication system, such as the number of users sharing the channel and their locations. Other aspects, more related to the propagation channel, such as path loss, shadow fading (or shadowing), and antenna radiation patterns are also important in the context of system performance, since these effects also vary with the locations of particular users. In this chapter, we will discuss the application of systemlevel simulation in the analysis of the performance of a cellular munication system under t