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Analyses for diversity and adaptive ...

Lehigh University.

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Analyses for diversity and adaptive transmission techniques in wireless systems.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Analyses for diversity and adaptive transmission techniques in wireless systems./
作者:	Li, Yan.
面頁冊數:	96 p.
附註:	Adviser: Shalinee Kishore.
Contained By:	Dissertation Abstracts International69-06B.
標題:	Engineering, Electronics and Electrical. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3316889
ISBN:	9780549654711

Analyses for diversity and adaptive transmission techniques in wireless systems.
Li, Yan.

Analyses for diversity and adaptive transmission techniques in wireless systems. - 96 p.

Adviser: Shalinee Kishore.

Thesis (Ph.D.)--Lehigh University, 2008.

Emerging wireless systems require reliable and spectrally efficient transmissions to provide high data rate services. The key challenge to wireless communications is multipath fading which causes fluctuations in the received signal power. Diversity techniques attempt to counter this disparity; in particular, they focus on reducing the fluctuations of received signal power to overcome the unreliability caused by bad channel conditions. However, a system designed for the worst-case channel conditions may often results in inefficient utilization of the radio resources. By adapting to the time variations of the channel and taking advantage of favorable channel conditions, adaptive transmission techniques enable spectrally efficient communications over wireless channels.

ISBN: 9780549654711Subjects--Topical Terms:

626636
Engineering, Electronics and Electrical.

Analyses for diversity and adaptive transmission techniques in wireless systems.
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245 1 0 $a Analyses for diversity and adaptive transmission techniques in wireless systems.
300 $a 96 p.
500 $a Adviser: Shalinee Kishore.
500 $a Source: Dissertation Abstracts International, Volume: 69-06, Section: B, page: 3752.
502 $a Thesis (Ph.D.)--Lehigh University, 2008.
520 $a Emerging wireless systems require reliable and spectrally efficient transmissions to provide high data rate services. The key challenge to wireless communications is multipath fading which causes fluctuations in the received signal power. Diversity techniques attempt to counter this disparity; in particular, they focus on reducing the fluctuations of received signal power to overcome the unreliability caused by bad channel conditions. However, a system designed for the worst-case channel conditions may often results in inefficient utilization of the radio resources. By adapting to the time variations of the channel and taking advantage of favorable channel conditions, adaptive transmission techniques enable spectrally efficient communications over wireless channels.
520 $a The first contribution of this dissertation involves the diversity factor (DF), a simple and easily evaluated metric for assessing link diversity. We show that the DF, which depends only on the first two moments of the SNR, effectively captures the asymptotic capacity improvement offered by optimal diversity reception for various Rayleigh-fading scenarios. The relationships between DF and other performance quantities, such as average symbol error probability and outage probability, are also discussed. These studies imply that diversity systems with the same DF have roughly same performance and that the DF may be useful in determining the performance of non-i.i.d. fading diversity paths using analytical methods developed for i.i.d. fading, where the DF is exactly equal to the number of diversity paths. To illustrate the broad applications of the DF, we validate this approximation approach in calculating the orthogonality factor in WCDMA downlinks.
520 $a The second contribution focuses on an asymptotic analysis of amplify-and-forward (AF) based cooperative diversity system in Nakagami-fading environments. Specifically, the asymptotic outage probabilities of CSI-assisted and semi-blind AF relaying, in terms of both diversity and coding gains, are derived for various channel profiles. The importance of our work is at least twofold: First, the Nakagami channel can be used to model a wide range of fading conditions and simple results like coding and diversity gains we present here, may be more useful than more complicated exact expressions. Second, under the same average power constraint, our results provide cooperative system designers with performance comparisons between two important AF relaying strategies, each with different implementation complexities, CSI requirements and short-term power constraints.
520 $a The third contribution of this thesis is motivated by recent interest in dynamic spectrum sharing between primary and secondary spectrum users. We investigate slow adaptive quadrature amplitude modulation (QAM) under third-party received power constraints. The optimal rate and power adaptation schemes are derived to maximize the average spectral efficiency (SE) for the secondary users. Additionally, closed-form expressions of the achievable SE are presented for correlated log-normal shadow fading environments. Our analytical and numerical results underscore the importance of exploiting shadowing correlation in the proposed adaptive schemes.
590 $a School code: 0105.
650 4 $a Engineering, Electronics and Electrical. $3 626636
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710 2 $a Lehigh University. $3 515436
773 0 $t Dissertation Abstracts International $g 69-06B.
790 $a 0105
790 1 0 $a Kishore, Shalinee, $e advisor
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3316889