A Comparison of Digital Transmission Techniques for Standard FM Mobile Radio Sets

Digital transmission for existing standard FM mobile radio sets is discussed. The transmission properties of such standard sets are presented. Various data pre-encoding techniques and the corresponding decoders are considered and their performances compared, The comparison includes consideration of the radiated FM spectra, the measured bit error rate curves, and the necessary complexity.     

数字专用无线通信系统的新进展

围绕ETSI近几年提出的数字无线电标准TS 102 361(Digital Mobile Radio),TS 102 490和TS 102 658(Digital Private Mobile Radio),阐述了数字专用无线通信系统的近期进展。主要分析了DMR标准和dPMR标准的起源、技术特点、应用情况和发展趋势;将这两种标准与我国现存的其他数字无线电标准进行了比较;在此基础上,结合我国专用无线通信系统现状,分析了两种标准在我国的应用前景。     

线性预测语音数字的编码技术

以一个双声道声码为例，说明一性预测编码技术在处理语音信号中的应用，一个２４００ｂｉｔ／ｓ双声道线性预测编码的声码器使用高速、可编程序的片型微处理机、字长可扩充。并使用２Ｋ的ＲＡＭ和１Ｋ的ＲＯＭ的数存储器。该系统设计成物理 ２０８毫微秒的双一结构。该声码器能同时处理两个声道，用微处理线性预测编码技术开发出该系统，并叙述使用该技术设计怕码器的要邻。     

Comparison of High-Level Modulation Schemes for High-Capacity Digital Radio Systems

This paper presents a comparative study of four 2ⁿ-state quadrature amplitude modulation techniques, namely, 16, 32, 64, and 128 QAM, in a digital radio system environment. The effects of filtering, interference, amplifier nonlinearities, and selective fading are investigated using computational and simulation methods. Increase of the carrier-to-noise ratio (CNR) at a fixed symbol error probability(10^{-3}) is taken as a robustness criterion.     

Pilot-Symbol-Aided 16PSK and 16QAM for Digital Land Mobile Radio Systems

The paper proposes a novel pilot-symbol-aided (PSA) technique for fading compensation of digital signals in the mobile environments. In a PSA system, the data sequence at the transmitter is divided into frames of data. A pilot symbol from a known pseudoradom-symbol sequence is inserted periodically into a frame of data symbol for transmission. In a conventional PSA-receiver, these pilot symbols are extracted from the received signal and used to estimate the effects of signal distortion introduced in the fading channel. The resultant estimates are then used to correct the distortion effects in the received data frames. In the paper, a novel estimation technique that uses the data symbols as well as the pilot symbols is proposed. The technique has the major advantages of simple implementation and short storage-delay time. Results are presented in a series of computer-simulation tests. These assess the effectiveness of the estimation technique on the BER performances of a 16-ary phase-shift keyed (16PSK) and a 16-ary quadrature-amplitude modulated (16QAM) signals in the frequency-selective and frequency-nonselective Rayleigh fading channels. The channels are corrupted by co-channel interference or additive white Gaussian noise. Results of differential-detected 16PSK and star-16QAM signals are also presented for comparison. It has been shown that, the use of PSA technique can significantly improve the bit-error-rate performances of the systems, relative to those using differential detection.     

The Effect of Channel Coding on the Efficiency of Cellular Mobile Radio Systems

Error correcting codes have two opposite effects on the efficiency of cellular mobile-radio systems. Although they increase the bandwidth per channel, the codes also make signals more robust and thereby reduce the required distance between users of the same frequency band. This paper reports a mathematical study of the interactions of these two effects in determining the efficiencies of a large number of sourcecode and channel-code combinations. Within a statistical performance objective (basebandSNR geq 11dB for 90 percent of the users), the most efficient scheme in this study has an embedded differential pulse code modulation (DPCM) source code and a rate 1/2 channel code that protects 2 bits of each 4 bit DPCM code word. Based on a conservative model of cellular transmission, we estimate that the bandwidth efficiency is 3 users/cell/MHz of system bandwidth. By contrast, there are only 1.2 users/cell/MHz with uncoded transmission and 4.5 users/cell/MHz with a rather complicated variable-rate scheme. We also observe that the embedded source code, originally devised for variable-rate operation, has a higher baseband SNR than conventional DPCM in certain fixed-rate environments.     

三种数字集群系统的话音编码技术分析比较

在众多数字集群系统标准中 ,Motorola公司研制的综合调度增强型网络iDEN、泛欧数字集群无线系统TETRA和以色列的数字集群系统FHMA属姣姣者。在优选适合我国国情的数字集群系统标准的最后阶段 ,就是从这三种系统标准中优选一种。本文主要介绍这三种系统的话音编码技术 ,并对它们进行分析比较。     

GMSK Modulation for Digital Mobile Radio Telephony

This paper is concerned with digital modulation for future mobile radio telephone services. First, the specific requirements on the digital modulation for mobile radio use are described. Then, premodulation Gaussian filtered minimum shift keying (GMSK) with coherent detection is proposed as an effective digital modulation for the present purpose, and its fundamental properties are clarified with the aid of machine computation. The constitution of modulator and demodulator is then discussed from the viewpoints of mobile radio applications. The superiority of this modulation is supported by some experimental test results.     

用于移动宽带基础设施的新一代无线电数字前端解决方案

网络运营商在通过使用新型空中接口、更高带宽和更多蜂窝基站努力扩大网络容量的同时,要求显著地降低设备成本。为提供能够满足所有这些需求的设备,无线基础设施设备的制造商正在寻求具有更高集成度、更低功耗和成本但灵活性更高的解决方案。本文将分析赛灵思提供的新型器件Zynq TM可扩展处理平台（EPP）将如何帮助设备制造商解决这些问题。     

Features and Performance of 12PM3 Modulation Methods for Digital Land Mobile Radio

A number of continuous-phase modulation methods suitable for digital and mobile radio applications has been grouped in a common class, which has been named 12PM3 (12-state, phase modulation with correlation over three consecutive bits). This paper introduces the definition of this class of modulation schemes, and presents some of its features. With reference to the scheme that gives the best spectral compactness, some effects of typical implementation imperfections of the modulation circuits are discussed. The performance of some 12PM3 modulators associated with a frequency discrimination receiver is then computed with reference to both AWGN (additive white Gaussian noise) channels and the typical propagation conditions envisaged for SCPC/FDMA digital land mobile radio systems in urban environment. The adopted pre and postdiscrimination filters of the receiver are optimized for the best performance. Different decision techniques are considered, namely 2-TH (2-threshold), 4-TH, mixed 2-TH/4-TH and MLSE (maximum-likelihood sequence estimation) techniques.     

基于软件无线电的数字语音岩层通信机

本文论述了一种基于软件无线电的甚低频低码率语音数字岩层通信机 ,它采用了QPSK调制和 FEC信道编码技术。计算机仿真和 DSP编程结果表明 ,与同一硬件平台上实现的数字化单边带岩层通信机相比 ,在带宽相近的条件下 ,语音数字岩层通信机的功放效率高、语音音质好、传输距离远     

Spread-Spectrum Mobile Radio with Variable-Bit-Rate Speech Transmission

We describe a digital mobile radio system in which users experiencing poor transmission reduce the number of bits per second used for speech coding from 32000 to 28000. They do so in a manner that greatly reduces the binary error rate. The reduced error rate more than compensates for increased quantization noise. We predict two statistics of user satisfaction in a mobile radio service area: POW, the percentage of users experiencing poor or worse transmission, and GOB, the percentage good or better. In a typical environment the maximum number of users that can operate within a 20 MHz band with POW ≤ 5 percent is 137, compared to 91 users when everyone transmits 32 kbits/s. The modulation technique is FH-FSK (frequency hopped, frequency shift keying) and the digital code is embedded ADPCM (adaptive differential pulse code modulation), in the mobile radio service area, signal strength depends on distance from mobile unit to a central base station. There is slow (shadow) fading due to terrain and building variations and rapid (Rayleigh) fading due to multipath propagation. To predict user satisfaction we have combined three different analyses: 1) a theory of FH-FSK, 2) a theory of the signal-to-noise ratio statistics in mobile radio service areas, and 3) a model, based on computer simulations and subjective testing data, of the dependence of subjective speech quality on ADPCM transmission rate and binary error rate.     

Teletraffic Analysis for Multicell Mobile Radio Telephone Systems

New teletraffic formulas are derived for the congestion in multicell mobile radio telephone systems. Fixed, dynamic, and hybrid channel asignment are considered and "tromboning," where mobileto-mobile calls go via a base station, is taken into account. The formulas agree with previously published sumulation results.     

Teletraffic Analysis for Single-Cell Mobile Radio Telephone Systems

Formulas are derived for the congestion in single-cell mobile radio systems in which there are both land-to-mobile and mobile-to-mobile calls and in which mobile-to-mobile calls go via the base station. Two approaches are used. The first yields modified forms of the familiar Erlang and Engset formulas. The second gives more complicated but more accurate formulas. The results of computer simulations to establish the accuracy of the formulas are described.     

A Multipath Fading Channel Model for Terrestrial Digital Radio Systems

The frequency transfer function of a multipath fading channel is examined in terms of its effects on digital radio signals. The transfer function is expanded into a power series about the channel center frequency and the coefficients are related to the multipath structure. It is then shown that, in the channelized common carrier bands below 15 GHz, the first two (complex) terms of the power series are usually sufficient for characterizing multipath effects. This demonstration is based on a mean-square error-of-fit measure which is applied to the multipath fading response and evaluated under some worst-case assumptions.     

Use of Four-Level Phase Modulation for Digital Mobile Radio

The paper explains the advantages of and compares various forms of four-level phase modulation from the point of view of performance, implementation, and spectrum usage. The results are applicable to digital mobile radio systems employing a large number of transmissions in which cochannel and adjacent channel interference are experienced. Of particular interest is the extent to which the theoretical spectra may be realized with practical transmitters. Differences between theoretical spectra and those measured from practical power amplifiers are identified. A method of simulating the effects of power amplifier nonlinearities is described and results are presented which agree closely with measurements made on an actual power amplifier.     

Advances in Digital Radio Systems

This paper examines the analog methods presently used in carrying digital signal via the terrestrial microwave radio relay systems. It then summarized the state of the art of two proposed digital radio systems, operating above and below 10 GHz. It also highlights some of the problem areas yet to be solved, with particular emphasis on these design problems associated with the high-capacity system. An extensive bibliography is given for easy reference.     

公众数字对讲机欧美市场准入介绍

数字对讲机对模拟对讲机的替代正在加速进行,该文针对数字对讲机产品出口面临的欧美市场准入问题,对涉及的标准,合格评定要求进行介绍.