Performance Analyses of Frequency-hopped Spread-spectrum Multiple Access Systems in Fading Environments

Performance Analyses of Frequency-hopped Spread-spectrum Multiple Access Systems in Fading Environments
Author: Usa Svasti-Xuto
Publisher:
Total Pages:
Release: 1996
Genre:
ISBN:

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The focus of this dissertation is the performance analyses of two classes of frequency-hopped spread-spectrum multiple access (FH-SSMA) systems in various fading environments. The capacity of Viterbi's FH-SSMA system is evaluated under three types of fading, namely Rician, shadowed Rician, and Nakagami fading. The results of recent experiments have indicated that these fading phenomena occur in various environments where the FH-SSMA system may be implemented. In this dissertation, the deletion probability for each fading scenario is derived. Subsequently, the system capacity is analyzed in terms of maximum number of users versus average bit error rate. The effect of a change in the signal-to-noise ratio level on the system capacity is also demonstrated. For Rician fading, it is found that the capacity of the system with a Rician factor of 2 dBis reduced by 13 percent as compared to the capacity of the non-fading case. For shadowed Rician fading, three shadowing scenarios are considered: light, average, and heavy. It is shown that the light and the average shadowing scenarios provide only a slight decrease in the capacity, while the heavy shadowing scenario renders a capacity identical to that for the Rayleigh fading case. Finally, for Nakagami fading the capacity is found to decrease by 50 percent as the fading parameter is reduced to 0.5. The performance of a cellular frequency-hopped spread-spectrum multiple access system is studied under an indoor environment. It is demonstrated how the system capacity, given in terms of the number of users per cell, is affected by the number of cells in the system. Also, the influence of the delay spread, which is the result of multipath propagation, is investigated. The analysis focuses on a worst-case scenario where a user receives both the desired and interfering signals with equal power levels. This scenario applies to both the downlink and the uplink. It is shown that the system capacity is reduced drastically as the number of adjacent interfering cells increases from one to three. Previous work concerning the indoor multipath propagation assumed that the number of paths is fixed, the path delays are uniformly distributed, and the path gains are equal. In this dissertation, a more realistic channel model derived from actual impulse response measurements by Saleh and Valenzuela is employed. The model consists of clusters of rays with constant cluster and ray arrival rates and power-delay time constants. The system performance is shown to be affected strongly by the change in the power-delaytime constants, yet only slightly influenced by the variation in the arrival rates of the rays and clusters. In addition, the degradation in the system performance due to the delay spread becomes more severe as the transmission rate increases.

Frequency-Hopped Spread-Spectrum Systems Have a Larger Multiple-Access Capability: The Effect of Interfering Signals with Unequal Power Levels

Frequency-Hopped Spread-Spectrum Systems Have a Larger Multiple-Access Capability: The Effect of Interfering Signals with Unequal Power Levels
Author: Evaggelos Geraniotis
Publisher:
Total Pages: 48
Release: 1988
Genre:
ISBN:

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In this report we present a new method for the evaluation of the probability of error of uncoded frequency-hopped spread-spectrum multiple-access (FH/SSMA) communications. For systems with binary FSK modulation, the method provides an accurate approximation and a tight upper bound to the bit error probability; for systems with M -ary FSK modulation, it provides tight upper bounds to the symbol error probability. This method relies on the integration of the product of the characteristic function of the envelope of the branch of the BFSK demodulator, which carries the desired signal, and of the derivative of the characteristic function of the envelope of the other branch; it can achieve any desirable accuracy and the computational effort required for its evaluation grows linearly with the number of interfering users. In the M -ary case, tight upper bounds based on the union bound and the results of the binary case are derived. Keywords: Frequency hopping, Spread spectrum, Multiple access, and Error control coding. (RH).

Performance Analysis of Multi-Channel and Multi-Traffic on Wireless Communication Networks

Performance Analysis of Multi-Channel and Multi-Traffic on Wireless Communication Networks
Author: Wuyi Yue
Publisher: Springer Science & Business Media
Total Pages: 335
Release: 2007-05-08
Genre: Computers
ISBN: 0306473119

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With the rapidly increasing penetration of laptop computers and mobile phones, which are primarily used by mobile users to access Internet s- vices like e-mail and World Wide Web (WWW) access, support of Internet services in a mobile environment is an emerging requirement. Wireless n- works have been used for communication among fully distributed users in a multimedia environment that has the needs to provide real-time bursty traffic (such as voice or video) and data traffic with excellent reliability and service quality. To satisfy the huge wireless multimedia service demand and improve the system performance, efficient channel access methods and analytical methods must be provided. In this way very accurate models, that faithfully reproduce the stochastic behavior of multimedia wireless communication and computer networks, can be constructed. Most of these system models are discrete-time queueing systems. Queueing networks and Markov chains are commonly used for the p- formance and reliability evaluation of computer, communication, and m- ufacturing systems. Although there are quite a few books on the individual topics of queueing networks and Markov chains, we have found none that covers the topics of discrete-time and continuous-time multichannel mul- traffic queueing networks. On the other hand, the design and development of multichannel mul- hop network systems and interconnected network systems or integrated n- works of multimedia traffic require not only such average performance m- sures as the throughput or packet delay but also higher moments of traffic departures and transmission delay.

Multiple-Access Capability of Frequency-Hopped Spread-Spectrum Revisited: An Exact Analysis of the Effect of Unequal Power Levels

Multiple-Access Capability of Frequency-Hopped Spread-Spectrum Revisited: An Exact Analysis of the Effect of Unequal Power Levels
Author:
Publisher:
Total Pages: 49
Release: 1988
Genre:
ISBN:

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In this paper we present a new method for the evaluation of the probability of error of uncoded frequency-hopped spread-spectrum multiple-access (FH/SSMA) communications. For systems with binary FSK modulation the method provides an accurate approximation and a tight upper bound to the bit error probability; for systems with M-ary FSK modulation it provides tight upper bounds to the symbol error probability. This method relies on the integration of the product of the characteristic function of the envelope of the branch of the BFSK demodulator, which carries the desired signal, and of the derivative of the characteristic function of the envelope of the other branch; it can achieve any desirable accuracy and the computational effort required for its evaluation grows linearly with the number of interfering users. In the M-ary case tight upper bounds based on the union bound and the results of the binary case are derived.