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.     

Analysis of Radio Paging Errors in Multitransmitter Mobile Systems

Many mobile telephone and personal paging systems require signaling simultaneously from multiple transmitters. This paper analyzes the factors that cause paging errors due to interference when the signaling format consists of audio tones sent simultaneously from two FM transmitters. The factors considered are: drift in carrier and modulation frequencies, and misequalization of land-line amplitude and audio delay. The following results are shown: 1) the interference errors are eliminated if the land lines are amplitude and phase equalized, 2)if the lines are not equalized but the modulation frequencies are equal, then the interference errors can be decreased by an order of magnitude if the transmitters are mistuned such that their difference carrier frequency is just greater than the modulation tone filter bandwidth in the receiver, and 3) if the modulation frequencies are slightly different, then the interference errors can be decreased somewhat by misequalizing the modulation indicies. It is then concluded that if the land lines are not equalized and the signaling tones are not exactly equal, the interference errors cannot be eliminated, but can be decreased by properly aligning the system.     

Fading Channel Prediction for Mobile Radio Adaptive Transmission Systems

Adaptive transmission methods can potentially aid the achievement of high data rates required for mobile radio multimedia services. To realize this potential, the transmitter needs accurate channel state information (CSI) for the upcoming transmission frame. In most mobile radio systems, the CSI is estimated at the receiver and fed back to the transmitter. However, unless the mobile speed is very low, the estimated CSI cannot be used directly to select the parameters of adaptive transmission systems, since it quickly becomes outdated due to the rapid channel variation caused by multipath fading. To enable adaptive transmission for mobile radio systems, prediction of future fading channel samples is required. Several fundamental issues arise in the design and testing of fading prediction algorithms for adaptive transmission systems. These include complexity, robustness, choice of an appropriate channel model for algorithm validation, channel estimation and noise reduction required for reliable prediction, and design and analysis of adaptive transmission methods aided by fading prediction algorithms. We use these criteria in the review of recent advances in the area of fading channel prediction. We also demonstrate that reliable fading prediction makes adaptive transmission feasible in diverse wireless communication systems.     

ARQ Schemes for Data Transmission in Mobile Radio Systems

An important problem in land mobile radio communications is how to provide reliable data communications to the largest number of users. To explore this problem, several existing ARQ protocols are examined which have application to the land mobile radio channel, as well as some new protocol combinations. All protocols are analyzed for several key system performance measures which are verified by experimental means for static as well as fading channels. Finally, a conclusion is reached regarding a new Protocol combination which is found to offer significant advantages over all other protocols explored.     

Cochannel Interference in High-Capacity Mobile Radio Systems

The probability of cochannel interference is evaluated for a mobile radio system operating in Rayleigh fading and log-normal shadowing environment. All cochannel cells surrounding the base station are taken into consideration in this evaluation. The results obtained are used to calculate the reuse distance and the cluster size (number of cells in a group). The blocking probability, the number of channels in each cell, the protection ratio, and the standard deviation are taken as parameters in this evaluation. The results show that shadowing has a severe effect on the interference level and on the channel reuse distance ratio.     

Traffic Engineering of Combined Mobile Telephone and Dispatch Systems

If a server group carrying short-holding-time queued traffic at high blocking probability is combined with another server group carrying normal blocked-calls-cleared traffic at low blocking probability, the resulting mixed group will in many cases operate at an intermediate blocking probability. Thus the mixed group provides better service to the queued traffic, while degrading the service of the cleared traffic. If the random arrival characteristics of the short-holding-time traffic are suitably modified by delaying calls an appropriate time before service, then the grades of service for both types of traffic may be engineered independently. An example of a possible use of this technique of induced delay, the combining of dispatch and mobile-telephone traffic on the same set of radio channels in the High-Capacity Mobile Telecommunications System, is discussed.     

Efficient Spectrum Utilization for Mobile Radio Systems Using Space Diversity

Space diversity combining is a well-known method of smoothing amplitude fluctuations of the received signal in Rayleigh fading environments, such as mobile radio. Perhaps less well known is that space diversity combining can also be an excellent method of combating cochannel interference. In this paper, it is shown that high spectrum efficiencies in mobile radio systems can be achieved with a modest number of space diversity branches. With a large number of diversity branches it is shown that frequency reuse is possible resulting in spectrum efficiencies, as defined herein, greater than 100 percent.     

基于移动网络的无线信号分布特性检验方法

介绍了移动网络的无线信号实时监控系统.在该系统长期的监测数据基础上,对移动网络的无线信号分布特性进行了统计分析.描述了Q-Q(Quantile-Quantile)图和P-P(Probabilty-Probabilty)图的理论基础,并采用该方法对监测数据进行了处理,验证了移动网络的信号变化服从正态分布.     

C 900--An Advanced Mobile Radio Telephone System with Optimum Frequency Utilization

The paper presents a survey of a new approach to advanced system solutions for mobile radio telephone systems. It is shown that, by the combination of both radio techniques and microprocessor data capabilities, improved means are available for controlling the specific multiple propagation and interference influences within the mobile radio environment. The aim of the system structure is to achieve the best possible frequency channel utilization, system availability, and cost benefits for deployment and users if traffic demand grows. The paper shows the different types of switching functions in public land mobile networks. Problems, as caused purely by radio conditions, are controlled within a defined radio exchange function, allowing the optimization of individual cell parameters. It is shown that distance measurement is the most reliable means of detecting cell boundaries. New approaches for system control channels lead to synchronous operation of base stations. The system operates with off-air call setup and queueing to improve channel utilization. Full national and international roaming capabilities are provided. During all calls, continuous digital link control is maintained to allow the radio exchange function in call condition. This new approach leads to different types of handoff to suit specific situations. Speech scrambling provides subscriber privacy.     

第三代移动通信系统中的软件无线电

阐述了软件无线电的发展动态、基本结构,分析了其关键技术,并对第三代移动通信系统中软件无线电技术的应用和发展作了初步的探讨。     

A Comparison of Digital Speech Coding Methods for Mobile Radio Systems

Subjective quality measurements on three digital speech coders, simulated with mobile radio channel transmission, were performed using the "mean opinion score (MOS)" method. The three speech coding methods tested were: continuously variable slope deltamodulation (CVSD) coding, adaptive predictive coding (APC), and residually excited linear predictive (RELP) coding. Several versions of each coder, with transmission rates in the range of 7.3 to 16.1 kbits/s, were simulated. Five different channel conditions, including three derived from land mobile radio field experiments, were applied to the speech coders' encoded output to study the effects. The results show that of the three coders, the CVSD coder is the most robust to channel errors, but produces reconstructed output speech of unacceptable quality. The 14.4 kbit/s RELP coder produces relatively good Output speech quality, exhibits a mild degree of robustness to mobile radio channel errors, and is slightly less complex than the APC coder. Of the three digital speech coders tested, the RELP coder appears the most suitable for use with land mobile radio. However none of the three coders was able to produce speech of telephone toll quality in a mobile radio environment.     

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。     

Spectral and Economic Efficiencies of Land Mobile Radio Systems

A variety of land mobile radio systems are compared by their spectral and economic efficiencies in providing various user services, system types covered are private one-channel, shared repeater one channel, controlled-access one-channel, trunked multichannel, and cellular. Spectral efficiency is defined to be the number of mobile users that can be served per MHz of spectrum in a core urban area, while economic efficiency is the average system cost per mobile. Both efficiencies vary with the type of usage, hence they are calculated for three major usages-mobile telephone service, dispatch service emergency, and dispatch service nonemergency. Services are described via seven "service parameters," namely call holding time (average), tolerable average wait for channel access, peak busy hour utilization per mobile, audio quality (S/N), noise levels tolerable, and service range. Sensitivity of the basic results to variations in the service parameters are also computed and discussed.     

IP电话与移动IP技术综述

简要介绍了IP电话的工作原理与技术方法 ,同时对支持主机和网络移动性的IP协议RFC2 0 0 2作了比较明确的阐述 ,以及该领域的现状与有关问题。     

IP电话与移动IP技术综述

简要介绍了IP电话的工作原理与技术方法,同时对支持主机和网络移动性的IP协议RFC2002作了比较明确的阐述,以及该领域的现状与有关问题。     

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.     

An Improved Stop-and-Wait ARQ Logic for Data Transmission in Mobile Radio Systems

An efficient Automatic-Repeat-Request (ARQ) logic, for use in systems with high error rate two-frequeney-simplex data channels, is proposed. The throughput efficiency provided by this logic is compared with that of conventional "stop-and-wait" ARQ, and a significant improvement is shown to be available. Particular emphasis is placed on the use of this logic for data transmission to mobile land vehicles.     

Joint Detection and Diversity Techniques in CDMA Mobile Radio Systems

CDMA mobile radio systems suffer from intersymbol interference (ISI) and multiple access interference (MAI) which can be combated by using joint detection (JD) techniques. Furthermore, the time variation of the radio channels leads to degradations of the receiver performance due to fading. These degradations can be reduced by applying diversity techniques. Three suboptimum detection techniques based on matched filters (MF), zero forcing (ZF) and minimum mean square-error (MMSE) equalization are considered. For further improvements, switched and equal gain diversity techniques are employed to combat fading. The performance is depicted in terms of the average bit error probability versus the average SNR per bit in a single cell environment showing an appreciable improvement over the non diversity situation. Theoretical results for the SNR at the front end of the receiver and the BER for ideal channel are obtained and compared with the simulation results.