摘要:

AbstractThe performance of an asynchronous multi‐cell Direct‐Sequence Spread Spectrum Multiple‐Access (DS/SSMA) system is evaluated in lineal microcells with flat Rician fading and shadowing. Both the Bit Error Rate(BER)of the uplink (i.e., the user to the base station) and the downlink (i.e., the base station to the user) are evaluated. We develop a new analytical model to evaluate the uplink performance which accounts for the user's spatial distribution, the chip waveform, the power control, and macro‐selection diversity. On the downlink, since no power control is used, the desired signal follows a composite log‐normal noncentral chi‐square distribution. We propose an approximation method to reduce the computational complexity while still providing satisfactory precision. The analysis results show that the macro‐selection diversity can reduce the other‐cell interference effectively even for a channel with heavy shadowing. The Rician factor, the standard deviation of the shadowing, and the chip waveform have significant influence on

ISSN:1124-318X    

DOI:10.1002/ett.4460060112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the context of deriving schemes for efficient use of the spectrum by multi‐media users in direct‐sequence code‐division multiple‐access (DS/CDMA) networks we describe in this paper an optimal policy for CDMA code allocation to voice and multi‐priority data traffic We consider CDMA networks with voice traffic and two types of data traffic: high priority data traffic with the same priority as voice traffic that requires real‐time delivery and lower priority data traffic that can tolerate delay and thus can be queued. A movable boundary policy in the CDMA code domain is used for the voice and high priority data, whereas a small number of CDMA codes are reserved for the lower priority data which also utilizes any CDMA codes left unused by the other two traffic types. The optimal policy is obtained by minimizing a cost function consisting of the weighted sum of the rejection rates of voice and high priority data traffic subject to performance requirements (bit error rates orBER)on all traffic types. The queueing delay of the lower priority data traffic is also evaluated. A semi‐Markov decision process (SMDP) with guaranteedBERsfor voice and data traffic is used for formulating the dynamic code assignment problem. A value‐iteration algorithm is applied to this SMDP to derive the

ISSN:1124-318X    

DOI:10.1002/ett.4460060113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFour contributors to Synchronous Digital Hierarchy (SDH) network desynchronizer buffer fill variations are the justification bits in the VC‐12 payload, the irregular spacing of the data in the VC‐12 payload, the irregular spacing of the data in the SDH frame, and the pointer activity which contains byte activity as opposed to the bit activity in the VC‐12 itself. These phenomena result in a variation of the rate at which bits arrive at a desynchronizer in a SDH network. Modeling and understanding of these processes is required in order to be able to propose advanced pointer processor algorithms as well as advanced jitter reduction techniques in SDH de‐synchronizers. This paper examines the relative effects of bit justifications in VC‐12 payloads in conjunction with the corresponding byte justifications in SDH networks in order to determine the dynamics of SDH network plesiochronous desynchronize

ISSN:1124-318X    

DOI:10.1002/ett.4460060114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this paper a new approximate method for the computation of outage probabilities in a mobile radio environment is proposed. It allows one to evaluate the performance of a mobile radio system in the presence of fading, in a very fast and accurate way, while maintaining a very good flexibility as to the application to different network environments. Coding is also considered as a possible choice, in order to increase the spectral efficiency of the system, which represents a major concern for the designers of cellular networks.

ISSN:1124-318X    

DOI:10.1002/ett.4460060115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe performance of a communication system that operates over a binary‐input, output‐symmetric memoryless channel and employs a convolutional error correcting code is usually evaluated by applying the union bound to the node error and the bit error probabilities. These bounds depend on the probability that an incorrect path on the code trellis accumulates a larger metric than the correct path. The paper presents an easy method to compute this pairwise error probability that is applicable to the significant case of a Viterbi decoder that uses a finite set of integer branch metr

ISSN:1124-318X    

DOI:10.1002/ett.4460060116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460060117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460060101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY