摘要:

AbstractNetwork services with deterministic guarantees are based on a worst—case description of user—generated traffic. When designing a policing and scheduling algorithm for guaranteed services on the Internet, accuracy of description of the traffic profile has to be traded with simplicity of implementation. The result of this trade off is often expressed as the number of token buckets required by the service along with the choice of their parameters. The GS type of service proposed by the IETF uses two token buckets both for characterizing the traffic and for policing it. The choice of using only two token buckets is primarily driven by policing costs. In this paper we propose a method that allows the number of token buckets used for characterizing the traffic to be greater than what is actually needed to police it. This means we can obtain an accurate profile of the traffic while keeping policing simple. The method consists of computing a profile of the traffic which involves a number of token buckets of the order of ten, and then doing the policing using only the first token bucket, plus another one which is chosen depending on the delay requirements of the receivers. This paper shows that with this simple enhancement we obtain a guaranteed service whose performance closely approaches the theoretical limits of services with deterministic guarant

ISSN:1124-318X    

DOI:10.1002/ett.4460120102

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

年代:2001

数据来源: WILEY

摘要:

AbstractMany papers have considered the problem of how to calculate theprobability of outagedue to cochannel interference in cellular radio systems. A general approach based on the characteristic function method has been recently presented in [1,2] and in [3]in the cases of Nakagami fading and Rice fading, respectively. However, closed—form results are available only in a few cases, while numerical integration and/or evaluation of special functions is the solution for other cases. In this paper we follow a similar approach as in the above works, but we evaluate integrals by using thesaddle point approximationmethod which has proven itself to be fast and accurate. Some comparisons between our results and the results published in the above references are reporte

ISSN:1124-318X    

DOI:10.1002/ett.4460120103

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

年代:2001

数据来源: WILEY

摘要:

AbstractCombined error correction and detection techniques, or hybrid automatic—repeat—request (ARQ) schemes with negative acknowledgment are considered for highly reliable reverse link data transmission in direct sequence code division multiple access (DS—CDMA) personal communication systems. The proposed selective repeat hybrid ARQ scheme employs an inner convolutional code for error correction and an outer shortened BCH code for error detection. Each negative acknowledgment message contains all packet sequence numbers that have been detected in error, and it is both error—correction and error—detection encoded. Accepted packet error rate and throughput are derived as a function of the error correction encoded frame error rate. An optimum signal—to—interference ratio (SIR) assignment maximizing the system's capacity is also found. A comprehensive simulation is conducted to evaluate performance of the data transmission system. Analysis and simulations show that by applying the proposed type I hybrid ARQ scheme with properly selected system parameters, virtually error free and highly efficient data transmission in CDMA personal communication system

ISSN:1124-318X    

DOI:10.1002/ett.4460120104

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

年代:2001

数据来源: WILEY

摘要:

AbstractIn this paper, the performance of trellis coded M—PSK systems is investigated operating over Rician fading channels with phase jitter. Thus the results reflect not only the degradation due to the effect of fading on the amplitude of the received signal, but also the impairment caused by the noisy carrier reference, which is usually neglected by the assumption of perfect phase tracking at the receiver. Analytical upper bounds on pairwise error probability for Rician fading with phase jitter are derived using Chernoff bounding technique in both cases where channel state information is available or not. The bit error probability performances are evaluated based on the modified transfer function approach. The numerical examples clearly demonstra'e the error performance degradation due to both amplitude fading and phase noise proces

ISSN:1124-318X    

DOI:10.1002/ett.4460120105

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

年代:2001

数据来源: WILEY

摘要:

AbstractSynchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) cross connect switching structures may be made non—blocking by providing sufficient hardware resources. For example, in a three—stage Clos switching structure this is accomplished by providing a sufficient number of middle stage switches to allow connections to be made without blocking. Nonblocking SONET/SDH cross—connects are more expensive than architectures which reduce the hardware complexity in their implementations at the expense of increased blocking probability. Under certain circumstances, initially unsuccessful new connections may still be connected if rearrangement of existing connections is possible. Factors which make rearranging connections difficult in a SONET/SDH signal environment is the multirate and multicast nature of the traffic, the requirement that any rearrangements must not interrupt existing sessions, and subnetwork connection protection. Cross—connects with this subnetwork connection protection capability must provide hardware and software functionality that selects between two independent copies of a signal and passes the error—free copy through the matrix. We explain how subnetwork protection introduces a requirement for intact switching of SONET/SDH signals. We also present a comparison of intact and fractional SONET/SDH connection and rearrangement algorithms in the context of subnetwork connection protection requirements. We demonstrate the blocking probability impact of introducing subnetwork protection connections into cross

ISSN:1124-318X    

DOI:10.1002/ett.4460120106

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

年代:2001

数据来源: WILEY

摘要:

AbstractAn analysis is presented for the evaluation of the probability of error achieved by single/multiple site diversity systems taking into account rain attenuation. A systematic method is proposed relating rain attenuation statistics to BER performance masks recommended by ITU for satellite links. The efficiency of site diversity as a countermeasure against severe rain attenuation is investigated for various frequency bands and climatic regions. Single site systems are compared to double and triple site diversity systems.

ISSN:1124-318X    

DOI:10.1002/ett.4460120107

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

年代:2001

数据来源: WILEY

摘要:

AbstractIn this paper new techniques able to solve the problem of frequency assignment in satellite communications are proposed. Their performance is evaluated in a non—linear environment that models the satellite channel behaviour. The stochastic approach consists in the exploration and validation of new load configurations for the downlink channel. Since the carriers have different powers, the complexity of the problem is high. An analytical approach is used for calculating the number and the power of 3rd order inter—modulation products, which may also be used for higher order contributions. After this, comparisons between classic and stochastic techniques, in terms of computational time and allocation quality, are sh

ISSN:1124-318X    

DOI:10.1002/ett.4460120108

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

年代:2001

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460120101

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

年代:2001

数据来源: WILEY