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With the rapid development of multimedia services, wireless communication engineers may face a major challenge to meet the demand of higher data-rate communication over error-prone mobile radio channels. As a promising solution, the concept of cooperative communication, where a so-called relay node is formed to assist the direct link, has recently been applied to alleviate the severe pathloss and shadowing effects in wireless systems. In addition, without spending extra spectrum and power resources, multiple-input multiple-output (MIMO) antenna systems have been shown to provide an immense improvement in system performance compared to its single-antenna counterpart. As such, cooperative MIMO communication is essential for wireless and mobile networks because of its remarkable increase in spectral efficiency and reliability. Although the utilization of cooperative communication in MIMO systems has gained great attention in the literature, most of the research works have assumed perfect conditions. Inspired by the aforementioned discussion, this thesis takes a step further to investigate the performance of cooperative communications with practical constraints. The thesis provides a general framework for performance analysis of cooperative communications subject to several practical constraints such as antenna correlation, rank-deficiency of the channel matrix, co-channel interference, and interference-limited constraint of cognitive radio networks based on an underlay spectrum-sharing approach. The thesis is divided into six parts. The first part investigates the performance of orthogonal space-time block codes (OSTBCs) over MIMO relay networks in Nakagami-m fading channels under the antenna correlation effect. The second part extends the full-rank MIMO channel to the case of the MIMO channel matrix being of rank-deficiency. Several important findings on the impact of the single-keyhole effect (SKE) and double-keyhole effect (DKE) are observed for two types of amplifying mechanism at the relay, namely, linear and squaring approaches. An important observation corroborated by our studies is that for offering a tradeoff between performance and complexity, we should use the linear approach for SKE and the squaring approach for DKE. The third part generalizes the keyhole effect to multi-keyhole channels. The exact and asymptotic expressions for symbol error probability (SEP) are derived for some specific cases such as multi-keyhole MIMO/multiple-input single-output (MISO) channel. The fourth part proposes a distributed Alamouti space-time code for two-way fixed gain amplify-and-forward (AF) relaying. In particular, closed-form expressions for approximated ergodic sum-rate and exact pairwise error probability (PWEP) are derived for Nakagami-m fading channels. To reveal further insights into array and diversity gains, an asymptotic PWEP is also obtained. The fifth part analyzes the outage performance of a two-way fixed gain AF relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Finally, the sixth part investigates the impact of interference power constraint on the performance of cognitive relay networks based on the spectrum-sharing approach.

With the incitation to reduce power consumption and the aggressive reuse of spectral resources, there is an inevitable trend towards the deployment of small-cell networks by decomposing a traditional single-tier network into a multi-tier network with very high throughput per network area. However, this cell size reduction increases the complexity of network operation and the severity of cross-tier interference. In this paper, we consider a downlink two-tier network comprising of a multiple-antenna macrocell base station and a single femtocell access point, each serving multiples users with a single antenna. In this scenario, we treat the following beamforming optimization problems: i) Total transmit power minimization problem; ii) mean-square error balancing problem; and iii) interference power minimization problem. In the presence of perfect channel state information (CSI), we formulate the optimization algorithms in a centralized manner and determine the optimal beamformers using standard convex optimization techniques. In addition, we propose semi-decentralized algorithms to overcome the drawback of centralized design by introducing the signal-to- leakage plus noise ratio criteria. Taking into account imperfect CSI for both centralized and semi-decentralized approaches, we also propose robust algorithms tailored by the worst-case design to mitigate the effect of channel uncertainty. Finally, numerical results are presented to validate our proposed algorithms.

Wireless sensor networks (WSNs) have introduced a new paradigm of communication between devices, which are applied to different scenarios. These applications demand three important performance parameters: the end-to-end reliability, the end-to-end delay and the overall energy consumption. Due to the fundamentality of reliability in many applications, we consider it in this thesis as a hard constraint, and the other two performance criteria, i. E. , energy and delay are exploited as a couple of competing criteria. Meanwhile, since unreliability is an inherent property of wireless channels, unreliable links are efficiently exploited to improve the energy-delay performance. We propose a metric for energy efficiency: mean energy distance ratio per bit and a metric for mean delay: mean delay distance, which are combine with the unreliable link model. Using these two metrics and a realistic unreliable link model, the lower bounds and the Pareto front of energy-delay trade-off are derived for three kinds of communication schemes: traditional multi-hop communications, opportunistic communications and cooperative MIMO (CMIMO) communications in three different channels: Additive White Gaussian Noise (AWGN) channel, Rayleigh block fading channel and Rayleigh flat fading channel. The close-form expression of these low bounds are obtained and verified by the simulations in 2-dimension Poisson networks. Furthermore, these results are applied to optimise the parameters of a network including physical and protocol layers. Finally, the lower bounds of the above three communication schemes are compared in different channels respectively. The results show that in order to achieve better energy-delay performance, the corresponding communication scheme should be adopted for different channels: traditional multi-hop communications for AWGN channel, opportunistic communications for Rayleigh block fading channel and CMIMO for Rayleigh flat fading channel

Wireless communication systems always demand higher data rates and better quality of service (QoS). Transmission reliability in a wireless channel with high path loss, time-varying multipath fading and power and bandwidth limitations, is a testing issue. Multiple-input multiple-output (MIMO) systems can reduce the effect of these channel interferences and achieve reliable signal transmission at high data rate. Space-time block code (STBC) is a coding scheme for the use of multiple transmits antennas providing a simple transmit diversity scheme. In certain MIMO fading environments, the offered channel capacity can be very low, where despite rich local scattering and uncorrelated transmit and receive signals, the system has a single degree of freedom. This effect has been termed as keyhole or pinhole effect. This contribution analyzes the average symbol error rate (SER) performance of MIMO systems employing orthogonal STBC with M-PSK constellations over fading channels in the presence of the keyhole. The Nakagami-m distribution has been considered for MIMO channel modeling. We derive the probability density function (PDF) of instantaneous signal-to-noise ratio (SNR) and an integral equation to calculate the average SER after space-time block decoding in such channels. Numerical results show that the keyhole significantly degrades the SER performance of the STBC in MIMO channels. The performance of such channels is a function of fading figure, m and diversity.

We study the performance of space-time block coding in terms of different transmission matrices over Nakagami-m fading channels in multiple-input multiple-output (MIMO) environments. A closed-form expression for the exact symbol error rate (SER) of orthogonal space-time block coding (OSTBC) over independent identically distributed Nakagami-m fading channels can be derived by means of the equivalent single-input single-output (SISO) model. The exact SERs of OSTBC with M-PSK and M-QAM modulations are expressed in terms of the moment generating function (MGF) of instantaneous SNR as well as the higher transcendental functions. In this paper, we provide performance evaluation results of several codes of OSTBC with the closed-form expressions; also, Monte Carlo simulation results are given, which demonstrate the accuracy of closed-form solutions. In addition, some new observations on the performance results of different code matrices are made.

We provide a closed form upper bound formulation for the average pairwise-error probability (PEP) of selective decode and forward (SDF) cooperation protocol for a keyhole (pinhole) channel condition. We have employed orthogonal space-time block-code scheme (OSTBC) in conjunction with multi-antenna (MIMO) technology. We have used moment generating function (MGF) based approach for deriving the upper bound of PEP. PEP expression provides information regarding the performance of the wireless system with respect to the channel conditions. We have included simulation results which confirm the analytical results of our proposed upper bound. Simulation results show that due to keyhole effect performance of wireless system degrades.

We propose a novel adaptive transmission scheme for space-time coded multiple-input multiple-output beamforming systems with imperfect channel state information at the transmitter, of which the signal constellation, total transmit power (temporal power), and power allocation among eigen-beams (spatial power) are jointly adapted to maximize the average spectral efficiency, subject to a target bit-error-rate and an average power constraint. The power allocation over the spatial and temporal domains makes the traditional approach of partitioning the received signal-to-noise ratio (SNR) inapplicable to the above design problem. By introducing a new variable, called as effective signal-to-noise-to-modulation ratio (ESNMR), we derive a rate-selection policy by partitioning the range of the ESNMR with an optimal set of thresholds. A closed-form temporal power control policy and a simple spatial power allocation algorithm are also obtained. Numerical results demonstrate that the new adaptive transmission scheme yields a significant performance gain over existing adaptation systems.

We present novel exact expressions and accurate closed-form approximations for the level crossing rate (LCR) and the average fade duration (AFD) of the double Nakagami-m random process. These results are used to study the second order statistics of multiple input multiple output (MIMO) keyhole fading channels with space-time block coding. Numerical and computer simulation examples validate the accuracy of the presented mathematical analysis and show the tightness of the proposed approximations.

We present closed-form bounds for the performance of multihop transmissions with non-regenerative relays over Nakagami-m fading channels. The end-to-end signal-to-noise ratio (SNR) is formulated and upper bounded by using the inequality between harmonic and geometric mean of positive random variables (RVs). Novel closed-form expressions are derived for the moment generating function, the probability density function, and the cumulative distribution function of the product of arbitrary powers of statistically independent Gamma RVs in terms of the Meijer's G-function. Using these theoretical results, closed-form lower bounds are obtained for the outage and average bit error probability of phase or frequency modulated signallings, while simple asymptotic expressions are also given for the bounds at high SNRs. Numerical results are compared to computer simulations, to show the tightness of the proposed bounds.

We present a symbol-by-symbol channel estimation receiver for an orthogonal space-time block coded system, and derive its analytical performance on a slow, nonselective, Rayleigh fading channel. Exact, closed-form expressions for its bit error probability (BEP) performance for M-ary phase shift-keying modulations are obtained, which enable us to theoretically predict the actual performance achievable under practical conditions with channel estimation error. Our BEP expressions show explicitly the dependence of BEP on the mean square error of the channel estimates, which in turn depend on the channel fading model and the channel estimator used. Tight upper bounds are presented that show more clearly the dependence of the BEP on various system parameters. Simulation results using various fading models are obtained to demonstrate the validity of the analysis.

We investigate the problem associated with the statistics of the product of two squared Shadowed Rician (SR) random variables (RVs). Both SR RVs are independent and nonidentically distributed. The distribution of the product of two squared SR RVs is very important from the satellite communication perspective. We derive approximate expressions of the probability density function (p.d.f.), the moment generating function (m.g.f.), and the cumulative distribution function (c.d.f.) in terms of Meijer-G functions. Furthermore, exact closed-form expressions for higher order moments, channel quality estimation index, and amount of fading are derived. The outage probability is also discussed by utilizing the expression of the c.d.f. An approximate closed-form expression of channel capacity is also derived with the help of the p.d.f. expression. Furthermore, the performance of satellite communication system is discussed in terms of the approximate symbol error rate by using the derived results. Specifically, the derived expression of the p.d.f. is used to develop an approximate closed-form expression of the m.g.f. for an amplify-and-forward-based satellite communication system.

We investigate the pairwise error probability (PEP) bounds for space-time trellis codes (STTC) in Nakagami-m fading channels with the arbitrary fading severity parameter, m. We derive an analytical expression for PEP upper bound in the case of two transmit antennas in terms of the higher transcendental functions, such as the Appell hypergeometric function or the Lauricella function, over uncorrelated and correlated Nakagami-m fading channels. Furthermore, we show that the probability bound for the general multiple transmit antenna scenario can also be expressed as an integral involving nested summations.

We investigate the joint relay and antenna selection performance in a multiple input multiple output (MIMO) Vehicle-to-Vehicle (V2V) communication system employing physical layer network coding (PLNC) with amplify-and-forward (AF) scheme at the relay antenna. Analytic results are derived under the cascaded Nakagami-m fading channel model assumption, which covers cascaded Rayleigh and conventional cellular channel models as well. We evaluate the performance of the system in terms of joint outage probability of sources and derive closed-form expressions for lower and upper bounds while an exact expression is found as a single integral form. Besides, the asymptotic diversity order is analyzed and quantified as a function of number of relays and antennas installed on the source and relay vehicles, and channel parameters. Finally, we verify the analytic derivations by computer simulations. Our results show that the outage probability performance decreases with the increasing cascading degrees of the channels but joint relay and antenna selection enhances the performance of the system superbly with the increasing number of relays and antennas. Also it is shown throughout all the simulation results, the lower bound for the joint outage probability seems to consistently be well tight for large SNR. Therefore it can be used for practical design of inter-vehicular communication systems which contain multiple relays and antennas.

We investigate physical layer security (PLY) of space–time-block-coded (STBC)–multi-input–multi-output (MIMO) wiretap channel in the presence of imperfect channel state information (ICSI) over Rician fading channel. Secrecy for data transmission to legitimate user in the presence of eavesdropper is metered in terms of average secrecy capacity (ASC), probability of non-zero secrecy rate (PNZSR) and secrecy outage probability (SOP). We derive the closed form expression for security parameter by using the probability distribution function and cumulative distribution function of output signal to noise ratio (SNR). Simulation results are presented to validate our analytical results and demonstrate the impact of ICSI on the secrecy performance of STBC–MIMO system.

We derive the exact maximal-ratio combining (MRC) performance of dual-hop cooperative diversity systems with L-antenna destination reception in Nakagami-m fading channels, where a single-antenna relay operates in semi-blind (fixed-gain) amplify-and-forward (AF) mode. We also show that if m₀, m₁, and m₂ are the respective Nakagami parameters for the source-to-destination, source-to-relay, and relay-to-destination links, the semi-blind AF cooperation with MRC achieves the diversity order of m₀L + min {m₁, m₂L}.

We derive the exact maximal-ratio combining (MRC) performance of dual-hop cooperative diversity systems with L-antenna destination reception in Nakagami-m fading channels, where a single-antenna relay operates in fixed-gain (semi-blind) amplify-and-forward (AF) mode. We also show that if m₀, m₁, and m₂ are the respective Nakagami parameters for the source-to-destination, source-to-relay, and relay-to-destination links, the fixed-gain AF cooperation with MRC achieves the diversity order of m₀L + min {m₁, m₂L}.

We derive novel exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the product and ratio of products of an arbitrary number of independent non-identically distributed (i.n.i.d) extended generalized-$$\mathcal {K}$$K (EGK) variates. The expressions are given in terms of the Meijer’s G-function and can be computed easily using commonly available mathematical software tools. They also subsume those for arbitrary combinations of other well-known variates and can be directly utilized in performance evaluation of wireless communication systems under different scenarios. We present various analytical results that are verified via Monte-Carlo simulations for both the PDF and CDF as well as their application in multiple practical scenarios.

We deal with the analytical performance study of orthogonal space-time block codes (OSTBC) applied to multiple-input multiple-output (MIMO) systems experiencing non-frequency selective fast fading and shadowing. We address the problem of finding a tractable closed-form expression for the symbol error outage (SEO) over Rice fading channels in shadowing environments. In order to obtain the SEO, a symbol error probability (SEP) inversion w.r.t. the average signal to noise ratio (ASNR) is needed since no invertible SEP approximations are available in literature. We propose an accurate approximation for the SEP in Rice fading channels. This new approximation is proved to be invertible w.r.t. the ASNR and this expression thus facilitates the derivation of a tight approximation of the SEO in lognormal shadowing environments.

We consider the two-way relaying of orthogonal space time block codes (OSTBCs) with imperfect channel information. We derive a maximum likelihood (ML) decoder of OSTBC, by assuming perfect channel knowledge at both user nodes. The decoding of OSTBC data at a user terminal is performed by replacing the exact channel state information (CSI) by the estimated CSI, in the ML metric. An approximate closed-form expression for the moment generating function (m.g.f.) of the received signal-to-noise ratio at a user is derived. By using the m.g.f. expression, the analytical average error performance of the scheme is obtained for M-ary phase shift keying constellation. The diversity order of the considered scheme is analytically calculated, for certain system configurations. It is deduced by the simulations and analysis that the channel estimation does not affect the diversity order of the two-way amplify-and-forward multiple-input multiple-output relay system.