三种多址蜂窝系统的容量及性能分析

从理论上推导了 FDMA、TDMA、CDMA制式的容量表达式 ,计算了 3种典型系统 AMPS、GSM和 Q- CDMA的容量关系 ,分析比较不同系统的通信性能 ,指出了移动通信系统的发展趋势     

Optimal channel assignment strategies for forced channel hopping in CDPD systems

To provide an acceptable call blocking probability in circuit-switched cellular networks, such as the Advanced Mobile Phone System (AMPS) networks, a significant fraction of the channel capacity in each cell is normally unused. This “free” capacity can be effectively used for packet data transmissions that yield to voice traffic when necessary. Cellular Digital Packet Data (CDPD) is a packet-switched data service which may share radio channels with the AMPS service on a secondary basis to tap this “free” capacity. The length of time that a CDPD stream can occupy a channel is greatly influenced by the channel assignment strategies of both the AMPS and the CDPD systems. This paper investigates these channel assignment strategies and their effects on the CDPD channel holding times, in comparison with the optimal channel assignment strategy that interrupts the CDPD service only when a new AMPS call finds no other idle channels in the cell site. One such optimal strategy is the cooperative strategy in which the CDPD and AMPS networks actively communicate with each other. It is shown that other optimal strategies exist without the need of communications between the two systems. The effects of AMPS traffic levels, number of channels, and number of CDPD streams at the cell site on the CDPD channel holding time and channel utilization are also considered. This revised version was published online in June 2006 with corrections to the Cover Date.     

Frequency overlay of GSM and cellular B-CDMA

The maximum capacity gain of a cellular broad-band direct-sequence code-division multiple-access (DS-CDMA) overlay on top of a cellular global system for mobile communications (GSM) system is estimated. Using geometrical arguments and a standard propagation model, all relevant contributions to the carrier-to-interference ratios (CIRs) of the GSM and CDMA systems are numerically evaluated. It is assumed that the base stations (BSs) of both systems are unilocated and that the power control in both systems is perfect. Furthermore, in the CDMA transmitters and receivers, ideal notch filtering is assumed around the occupied GSM frequencies of the same cell. Adapting standard limits for the CIRs of 5-7 dB for CDMA and 9-12 dB for GSM, the total system capacity can be increased considerably over the GSM-only case: the capacity is increased by a factor of 1.8-2.9 if no macrodiversity is employed and by a factor of 1.9-3.3 if macrodiversity in the CDMA downlink is applied     

Optimal channel assignment strategies for forced channel hopping in CDPD systems

To provide an acceptable call blocking probability in circuit-switched cellular networks, such as the Advanced Mobile Phone System (AMPS) networks, a significant fraction of the channel capacity in each cell is normally unused. This “free” capacity can be effectively used for packet data transmissions that yield to voice traffic when necessary. Cellular Digital Packet Data (CDPD) is a packet-switched data service which may share radio channels with the AMPS service on a secondary basis to tap this “free” capacity. The length of time that a CDPD stream can occupy a channel is greatly influenced by the channel assignment strategies of both the AMPS and the CDPD systems. This paper investigates these channel assignment strategies and their effects on the CDPD channel holding times, in comparison with the optimal channel assignment strategy that interrupts the CDPD service only when a new AMPS call finds no other idle channels in the cell site. One such optimal strategy is the cooperative strategy in which the CDPD and AMPS networks actively communicate with each other. It is shown that other optimal strategies exist without the need of communications between the two systems. The effects of AMPS traffic levels, number of channels, and number of CDPD streams at the cell site on the CDPD channel holding time and channel utilization are also considered. This revised version was published online in June 2006 with corrections to the Cover Date.     

浅谈无线接入技术

无线接入技术可分为模拟无一接入技术和数字无线接入技术,数字无线接入系统又有多种解决方案,包括数字直接扩频技术、ＧＳＭ、ＣＤＭＡ、ＤＥＣＴ、ＰＨＳ和ＳＣＤＭＡ等。     

Three-dimensional cellular systems for air/ground personal communication

A new three-dimensional (3-D) cellular system is proposed for air/ground (A/G) personal communications. The proposed system extends the Global System for Mobile Communication (GSM) to enable its subscribers to send and receive calls while traveling in the air using the same subscriber identity module (SIM)-the same mobile number-that is used for the ground network. Modifications to the GSM system architecture to develop the A/G system architecture are outlined. A multilayer service volume is proposed in which the coverage volume is divided into three coaxial cylindrical layers (cells) with each layer serving a limited part of the airspace. Capacity of the new proposed system based on the standard GSM concept is analyzed and compared to other alternative systems: Code Division Multiple Access (CDMA) and Frequency Division Multiple Access (FDMA).     

Using RF filtering to reduce competitor-induced interference

This paper examines the success of RF filtering on mitigating interference that occurs between two wireless multiple-access systems operating within the same geographic area. Such interference is referred to as "competitor-induced interference" and can significantly degrade system capacity and performance. Three dual-system scenarios are considered: a dual code-division multiple-access (CDMA) (IS-95) system, a CDMA mobile in an FM (AMPS) cell, and an FM mobile in a CDMA cell     

码分多址系统的抗干扰分析

对于800MHz频段码分多址(CDMA)系统基站和直放站的杂散辐射对全球移动通信系统(GSM)900的干扰限制,信产部无(2002)65号文已作了明确规定。至于GSM900对CDMA的干扰,以及GSM1800和个人接入系统(PAS)等时分多址系统对第三代移动通信系统中宽带码分多址(WCDMA)系统的干扰影响有多大,文中以CDMA系统的抗干扰机理为基础,分析多系统共(站)址时这些干扰对CDMA系统容量的影响。工程实践中,通常采用滤波器来减少干扰对系统容量的影响,文中推导的公式可用来计算滤波器的衰减指标。     

Known and novel diversity approaches as a powerful means to enhancethe performance of cellular mobile radio systems

The main requirements to be met by third generation mobile radio systems are high cellular spectrum efficiency and high flexibility. The authors focus on high cellular spectrum efficiency, which is difficult to achieve due to the time variance and frequency selectivity of the mobile radio channel and due to interference. It is known that the degrading effects of these adverse characteristics of the mobile radio channel and of interference can be mitigated by diversity. The way how diversity influences cellular spectrum efficiency is derived in general. As a reference point, the types of diversity used in GSM are analyzed. In GSM, the potential for diversity enhancement inherent in code-division multiple-access (CDMA) is not exploited. A joint detection code-division multiple-access (JD-CDMA) system concept aimed at third generation mobile radio systems has been proposed which introduces a CDMA feature into systems based on time-division multiple-access (TDMA) and frequency-division multiple-access (FDMA) like GSM and also advanced TDMA (ATDMA). The gains achievable by different types of diversity in GSM as well as in the JD-CDMA system concept are investigated. It is shown that considerable gains can be achieved by different types of antenna diversity and by exploiting the additional diversity potential of CDMA. Therefore, third generation standards should be flexible in order to allow the use of as many types of diversity as possible to enhance the cellular spectrum efficiency     

CDMA与GSM基站共址杂散干扰仿真与分析

随着无线通信技术和服务要求的飞速发展，出现了第二代和第三代系统，以及同一代移动通信系统内不同通信标准共存的情况。中国联通的CDMA系统和GSM系统就是一个最具代表性的例子。不同系统营运于同一个电磁环境下，势必会带来系统之间电磁兼容的问题。对电磁兼容中的共址干扰问题中的杂散干扰做了较深入地探讨。     

A 3-V monolithic SiGe HBT power amplifier for dual-mode (CDMA/AMPS)cellular handset applications

A dual-mode (CDMA/AMPS) power amplifier has been successfully implemented by using a monolithic SiGe/Si heterojunction bipolar transistor (HBT) foundry process for cellular handset (824-849 MHz) applications. The designed two-stage power amplifier satisfies both CDMA and AMPS requirements in output power, linearity, and efficiency. At V _cc=3 V,the power amplifier shows an excellent linearity (first ACPR<-44.1 dBc and second ACPR<-57.1 dBc) up to 28 dBm of output power for CDMA applications. Under the same bias condition, the power amplifier also meets AMPS handset requirements in output power (up to 31 dBm) and linearity (with second and third harmonic to fundamental ratios lower than -37 dBc and -55 dBc, respectively). At the maximum output power level, the worst power-added efficiencies (PAEs) are measured to be 36% for CDMA and 49% for AMPS operations. The power amplifier also tolerates severe output mismatch (VSWR>12:1) up to V _cc=4 V, with spurs measured to be <-22 dBc in CDMA outputs at two specific tuning angles, but with no spur in AMPS outputs at any tuning angle     

Where there's a WILL [wireless in the local loop]

Linking telephone subscribers into the network via wireless in the local loop (WILL) promises to boost telephone usage and enhance the effectiveness of telecommunications liberalisation. There is a wide choice of wireless technology potentially suitable for deployment in WILL applications. Candidates include the various analogue cellular technologies, digital cellular including GSM, and cordless systems including CT2 and DECT. The author discusses the FDMA/TDMA based fixed radio access system of Ionica, and the CDMA based system of Liberty. Both are in competition with BT. The choice of radio technology is discussed as are the problems caused by telecommunications liberalisation     

Who will get China's 3G dowry?

The situation in China mainly boils down to a contest between two versions of code division multiple access (CDMA). One is Europe's wideband CDMA (WCDMA), which was designed to be as compatible as possible with Europe's hugely successful second-generation Global System for Mobile Communication (GSM). The other, CDMA2000, is preferred by US manufacturers like Motorola Inc. and Lucent Technologies, as well as Qualcomm. The picture has been complicated, however, by China's development of an indigenous alternative, combining elements of other standards. China's Ministry of Information Industry has been working with Siemens to develop a system it calls TD-SCDMA, for time-division synchronous code-division multiple access.     

Rayleigh fading channels in mobile digital communication systems.II. Mitigation

For pt. I see ibid., vol. 35, no. 7, p. 90, 1997. In Part I of this tutorial, the major elements that contribute to fading and their effects in a communication channel were characterized. In Part II, these phenomena are briefly summarized, and emphasis is then placed on methods to cope with these degradation effects. Two particular mitigation techniques are examined: the Viterbi equalizer implemented in the Global System for Mobile Communication (GSM), and the RAKE receiver used in CDMA systems built to meet Interim Standard 95 (IS-95)     

一种基于CDMA/TDMA混合多址的GSM与CDMA扩容方法

提出了一种基于CDMA/TDMA混合多址的GSM与CDMA扩容方法。在发送端,通过扩频码对GSM信号进行直接序列扩频,使其多址方式由TDMA变换为CDMA/TDMA,然后与CDMA信号在空间同频传输,这样就可以解决两个系统在Um接口的兼容问题;在接收端,使用相同的扩频码对CDMA/TDMA信号进行解扩,使其多址方式由CDMA/TDMA还原为TDMA,由此可以将GSM与CDMA两种信号进行分离。文章提出了用互补码集作为多址接入码,并给出了一个时隙内GSM用户被扩频调制的具体过程。理论分析和仿真结果表明,该方法可使系统总容量扩大2倍。     

RADIO AND NETWORK COMPARISONS FOR MSBN AND GSM SYSTEMS IN A GEOSTATIONARY SATELLITE ENVIRONMENT

One of the most frequently debated issues in satellite communications concerns the comparison between time division multiple access (TDMA) and code division multiple access (CDMA) systems. Although, in our view, a general answer to this problem cannot be found, this paper presents comparisons of two systems utilizing the above-mentioned access techniques, both from a radio and a network point of view. In particular, the mobile satellite business network (MSBN), (a CDMA system currently being developed by the European Space Agency (ESA) for general satellite applications) and the full integrated extension to satellite systems of the global system for mobile communication (GSM) (the well-known frequency division multiplex (FDM)/TDMA pan-European mobile cellular system) are compared by taking, as the reference payload, the L-band land mobile (LLM) satellite (a spot-beam geostationary satellite whose launch should take place at the end of 1997). Reasonable assumptions take into account the fact that, on one hand, the MSBN system is not completely defined and, on the other, the GSM is applied in a context different from the one specified by the European Telecommunication Standard Institute (ETSI). Performance comparisons are carried out in terms of flexibility and number of available channels for the same quality requirements, emitted power levels, propagation environment and interference levels coming from adjacent satellites. It is concluded that MSBN is more flexible than GSM and that, as regards capacity, an advantage of GSM over MSBN is present in the transportable mobile case, whereas, in the vehicular mobile case, MSBN shows an advantage over GSM. © 1996 by John Wiley & Sons, Ltd.     

Cell phones answer Internet's call

Cellular service providers, handset manufacturers, and system integrators are captivated by the promise of the wireless Internet using third generation cellular telephony. The leading contender to be the global standard for third-generation cellular telephony is the Universal Mobile Telecommunication System (UMTS). This is a wideband CDMA system designed to be smoothly backward-compatible with GSM, and also the leading member of the IMT-2000 family of third-generation systems sponsored by the International Telecommunication Union (ITU). The developments of this technology and its impact on the telecommunications industry worldwide are discussed     

Digital wireless local loop system

The digital access technologies for the wireless local loop (WLL) or fixed wireless system are discussed. WLL is an important means of providing telephone services more cheaply and quickly in the developing countries than through a wireline system. Capacities of a WLL system based on the IS-54 (now IS-136) TDMA, IS-95A CDMA, and ETSI GSM technologies are developed and compared     

AD8348正交IQ解调器及其应用

IQ解调是数字调制系统中一种重要的解调方法,AD8348是Analog Devices公司推出的一种IQ正交解调器,广泛应用于QAM/QPSK解调器及各种通信系统中,如W-CDMA/CDMA/GSM等。介绍了AD8348的性能特点、内部结构、具体应用设计,并给出了典型应用电路及结果。     

CDMA Mobile System Overview: Introduction,Background, and System Concepts

The CDMA Mobile System (CMS) has been developed by Electronics and Telecommunications Research Institute (ETRI) and fieldtested for commercial ser- vice deployment in Korea. The project was started in 1989 and completed in 1995 with the CMS commercial test. During the course of development, there had been active technical cooperation with Qualcomm, Inc. and Korean manufacturers. The CMS adopted the basic CDMA concepts conforming to Korean CDMA system which was derived from IS-95. The CMS functions are allocated to subsystems by considering efficiency and expandability. The CMS consists of mobile stations and the infrastructure which is composed of base stations, mobile exchanges and home location register/authentication center. The commercial field tests performed both in Taejon and Seoul have indicated that the CMS capacity is 10 to 15 times larger than that of AMPS. This paper overviews the development history, system characteristics, architecture and test results.