Showing papers by "Mazen O. Hasna published in 2003"

End-to-end performance of transmission systems with relays over Rayleigh-fading channels

Abstract: End-to-end performance of two-hop wireless communication systems with nonregenerative relays over flat Rayleigh-fading channels is presented. This is accomplished by deriving and applying some new closed-form expressions for the statistics of the harmonic mean of two independent exponential variates. It is shown that the presented results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, average bit-error rate expressions for binary differential phase-shift keying, as well as outage probability formulas for noise limited systems are derived. Finally, comparisons between regenerative and nonregenerative systems are presented. Numerical results show that the former systems clearly outperform the latter ones for low average signal-to-noise-ratio (SNR). They also show that the two systems have similar performance at high average SNR.

A performance study of dual-hop transmissions with fixed gain relays

Abstract: The paper presents a study on the end-to-end performance of dual-hop wireless communication systems equipped with non-regenerative fixed gain relays and operating over flat Rayleigh fading channels. More specifically, it first derives generic closed-form expressions for the outage probability and the average probability of error when the relays have arbitrary fixed gains. It then proposes a specific fixed gain relay that benefits from the knowledge of the first hop's average fading power and compares its performance with previously proposed relay gains that, in contrast, require knowledge of the instantaneous channel state information of the first hop. Finally, the paper investigates the effect of the relay saturation on the performance of the systems under consideration. Numerical results show that non-regenerative systems with fixed gain relays have a comparable performance to non-regenerative systems with variable gain relays. These results also show that relay saturation of these systems results in a minimal loss in performance.

Outage probability of multihop transmission over Nakagami fading channels

Abstract: We present a general analytical framework for the evaluation of the end-to-end outage probability of multihop wireless communication systems with nonregenerative relays over Nakagami fading channels. It is shown that the presented results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, we obtain a closed-form expression for the moment generating function of the reciprocal of the end-to-end signal-to-noise ratio (SNR) and we then use this expression to calculate the outage probability via numerical inversion of the Laplace transform. Numerical examples show that regeneration is more crucial at low average SNR and for multihop systems with a large number of hops.

Performance analysis of cellular mobile systems with successive co-channel interference cancellation

Abstract: This paper presents an analytical framework for the performance evaluation of cellular mobile radio systems equipped with smart antenna systems. In particular, the paper focuses on low-complexity systems which are able to successively suppress the strongest active interferers. The desired user fading statistics is assumed to be flat Rayleigh, Rician, or Nakagami, whereas the interfering signals are assumed to be independent and subject to slow flat Rayleigh fading. The paper starts by presenting generic closed-form expressions for the the carrier-to-interference ratio probability density function after interference cancellation. Based on that, exact closed-form expressions for the outage probability and average error rate formulas are derived. Finally, a comparison with a practical cancellation scheme and the impact of some practical considerations on the performance of successive interference cancellation are investigated. More specifically, the effect of traffic loading, the overall spectral efficiency gain, and the impact of time delay are studied.

Optimal power allocation for relayed transmissions over Rayleigh fading channels

Abstract: Relayed transmission is a way to attain broader coverage by splitting the communication link from the source to the destination into several links/hops. One of the main advantages of this communication technique is that it distributes the use of power throughout the hops which means longer battery lives and lower interference introduced to the rest of the network. In this context, this paper investigates the optimal allocation of power over these links/hops for a given power budget. All hops are assumed to be subject to independent Rayleigh fading. The optimization criterion used is outage probability which is the probability that the link quality from source to destination falls below a certain threshold. Numerical results show that optimizing the allocation of power enhances the system performance, specially if the links are highly unbalanced in terms of their average fading power. They also show that non-regenerative systems with optimum power allocation can outperform regenerative systems with no power optimization.

Average BER of multihop communication systems over fading channels

Abstract: Multihop transmission is a way to attain broader coverage by splitting the communication link from the source to the destination into several, possibly shorter links/hops This paper presents an expression for the moment generating function (MGF) of the end-to-end signal-to-noise ratio of multihop non-regenerative systems, which makes it possible to use the MGF-based approach for calculating the average BER of several modulation schemes Due to the complexity of the expression introduced, the paper presents also a lower bound on the average bit error rate performance of the systems under study Numerical results show that relaying enhances the system performance compared with equivalent direct transmission They also show that increasing the number of hops has a diminishing effect on the degradation of the performance of multihop systems

Average outage duration of multihop communication systems with regenerative relays

Abstract: Closed-form expressions for the average outage duration of multihop regenerative communication systems over generalized fading channels are presented. These results are general and account for the noise-limited and interference-limited systems. To show the usefulness of the presented expressions, some specific fading scenarios are considered. Finally, some numerical examples of interest comparing direct and relayed transmission, and studying the effect of increasing the number of hops and/or co-channel interferences are plotted and discussed.

End-to-end outage probability of multihop transmission over lognormal shadowed channels

Abstract: يقدم هذا البحث دراسة لاحتمالية الانقطاع الكلي لأنظمة الاتصالات اللاسلكية متعددة القفزات العاملة في قنوات الحجب ذات الطابع اللوغارثمي الطبيعي ‏كما يقدم البحث معادلة محكمة لنسبة الإشارة إلى الضوضاء في الأنظمة المزودة ‏بمرحلات غير مجددة، و يبين أن تركيب المعادلة الثي ثم استنتاجها تجعل من الممكن تقريبها باستخدام متغير لوغارثمي طبيعي. وبناء على ذلك يستنتج البحث معادلات محكمة لاحتمالية الانقطاع في الأنظمة المزودة بمرحلات غير مجددة، ومن ثم يتم مقارنتها بتلك الخاصة بالأنظمة ذات المرحلات المجددة . ‏وتوضح الأمثلة العددية في البحث أن استخدام مرحلات مجددة أمر ضروري عندما تكون نسبة الإشارة إلى الضوضاء متدنية، أو عندما يكون عدد القفزات في النظام كبيرا .

Outage Probability of Multihop Transmission Over

Abstract: We present a general analytical framework for the evaluation of the end-to-end outage probability of multihop wireless communication systems with nonregenerative relays over Nakagami fading channels. It is shown that the presented results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, we obtain a closed-form expression for the moment generating function of the reciprocal of the end-to-end signal-to-noise ratio (SNR) and we then use this expression to calculate the outage probability via numerical inversion of the Laplace transform. Numerical examples show that regeneration is more crucial at low average SNR and for multihop systems with a large number of hops.