【正文】 間產(chǎn)生同頻干擾，這 是影響蜂窩系統(tǒng)容量和性能的主要制約因素之一。本章我們將討論在同頻干擾情況下，包括一個典型系統(tǒng)中的天線和傳播的影響。從基站到移動臺這個發(fā)送方向使用的射頻信道稱為前向信道，而從移動臺到基站這個發(fā)送方向使用的信道稱為反向信道。把服務區(qū)內(nèi)可用的無線頻譜都分配給每一個簇，使同一個簇內(nèi)的小區(qū)不共用相同的信道。例如，如果一個移動臺同時接收來自本地小區(qū)基站的信號和鄰近層的同頻小區(qū)基站產(chǎn)生的信號，就會產(chǎn)生同頻干擾。如前所述，在我們感興趣的那個特定小區(qū)周圍，同頻小區(qū)組成一個個的層。但是第一層的同頻小區(qū)對總的干擾時從所有層的全部同頻小區(qū)發(fā)送出的同頻干擾信號的總和。例如，在不增加分配給系統(tǒng)的無線頻譜帶寬的前提下，得到高容量（大量的用戶）的一種措施是，通過減小蜂窩系統(tǒng)簇的大小 N，來縮短信道復用距離。 同頻干擾的影響可以用通信鏈路的信干比（ SIR）來估計，這里信干比定義為有用信號的功率 S與總干擾信號的功率 I之比。要注意鏈路中斷概率和系統(tǒng)中斷概率之間的區(qū)別，前者是根據(jù)可接受的聲音性能所需的特定誤比特率（ BER）或者Eb/N0閾值，確定是否為中斷，而后者考慮的是一個典型用戶可接受的移動性能所需的 SIR閾值。本章我們給出了蜂窩通信系統(tǒng)的簡單仿真示例，著重考慮通信系統(tǒng)的一些系統(tǒng)方面的問題，包括多用戶性能、話務量工程和信道復用。這樣，無論何時何地你都將能夠通過無線網(wǎng)絡獲得大量的媒體信息和娛樂。我們唯一確信的是 2020 年多媒體移動通信將沖擊日本市場，而且歐洲SIR(x)pSIR(x)p和北美也將很快發(fā) 展多媒體通信市場。 IP 的自然無連接性可以大大提高存取速率 : 文件下載只需要很短的時間，而且只需輕輕一點就能和網(wǎng)絡連接上。 3G服務將為我們管理個人信息提供幫助，簡單的任務例如在食品雜貨店，如何合理的利用時間來提高我們的服務就是非常生動的應用。 在休閑度假中，你倒了一個新城市。商人是關(guān)注電視節(jié)目實際間最長的人，因此，他們?yōu)槭謾C的設計者描述了一個很大的商機。到一個服務車站 , 你使用你的 3G 裝置和你的同事舉行電話會議，與此同時，你能看到全部草稿的發(fā)表而且在線上做出相應的變化。綜合在一起，這些為先進的移動英特網(wǎng)服務奠定了基礎，包括個性化的入口，你的手機將會自動接收最新的電視信息，提供高品質(zhì)的聲音和圖像。 這一段提出了一些主要的技術(shù)和發(fā)展的簡短觀點。當 電子數(shù)據(jù)采集設備備集成到 GPRS中，這些數(shù)據(jù)的傳輸率將會達到 384 kbit/s 。 WCDMA 寬帶碼分多址接入技術(shù) (WCDMA) 提供的數(shù)據(jù)傳送速率遠遠大于現(xiàn)在我們采用的通信方式，提供高達 2Mbit/s的傳輸速率，大大提高了光纖對語音信號的傳輸率。 愛立信在 WCDMA的研發(fā)方面走在了前列。 全球革命性的提高傳輸速率將是原來的 GSM和 TSMA運營商利用現(xiàn)有的設備提供 3G服務。 cdma2020提供的帶寬向我們展示了 3G的潛能。 愛立信是 cdma2020研發(fā)的先行者，它制定了對無線通信和網(wǎng)絡中樞進行改革的新標準，同時也提出了對 IP 和多媒體網(wǎng)絡進行改革的意見。存儲在智能數(shù)字助理上的日程表可以在個人計算機中藍牙能夠達到范圍里面自動更新。愛立信已經(jīng)研制出了藍牙裝置，包括 T36藍牙手機和藍牙掌上設備。s core characteristic is the wide band addressing turns on nongap roaming between the rigid work and numerous different munications system39。s 3G handset, during has had two mobile munication technology transformation, transits from 1G AMPS to 2G GSM, from GSM to IMT2020 (. 3G technology). 1 The mobile munication technology to have the following several aspect important technologies: 1) Wideband modulation and multiple access technique The wireless high speed data transmission cannot only depend on the frequency spectrum constantly the expansion, should be higher than the present number magnitude at least in the frequency spectrum efficiency, may use three technologies in the physical level, namely OFDM, UWB and free time modulation code. OFDM with other encoding method39。s Rake receive and the track technology, the OFDMA technology which declines from the time domain and the frequency range resistance time and the frequency selectivity, the link autoadapted technology, the union coding technique. 2) Frequency spectrum use factor lift technique The fundamental research pointed out: In the independent Rayleigh scattering channel, the data rate and the antenna several tenth linear relationships, the capacity may reach Shannon 90%. Is launching and the receiving end may obtain the capacity and the frequency spectrum efficiency gain by the multiantenna development channel space. The MIMO technology mainly includes the spatial multiplying and the space diversity technology, concurrent or the salvo same information enhances the transmission reliability on the independent channel. Receives and dispatches the bilateral space diversity is the highcapacity wireless munication system uses one of technical. Bell Lab free time39。s foundation, has had the land honeyb mobile munication, the satellite munication as well as the wireless Inter munication, these mailing address caused the correspondence appearance to have the huge change, used the digital technique the modern wireless munication already to permeate the national economy each domain and people39。 The three, software39。 The six, puters have developed from central processing to the distributional server and intellectualized processing。 2) Networking wide band。 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. Simulatio