Επίδοση μεθόδων επικοινωνίας με πολλαπλούς αναμεταδότες σε γενικευμένους διαύλους ασύρματων επικοινωνιών
Μπίσιας, Νικόλαος Σ.
SubjectWireless communication systems ; Radio relay systems ; Digital communications -- Reliability -- Mathematics ; Error-correcting codes (Information theory) ; Stochastic analysis
This dissertation investigates the performances of multihop relaying systems in composite fading environments. A review of small and large-scale fading for the wireless channel is given in Chapter 1, where the statistical characterization of various channel models is presented. This work considers the generalized-X fading channel, which is a composite fading model that considers the effects of both small- and large-scale fading on the received signal. Then, in Chapter 2 it reviews various relay systems that have been proposed for wireless communications according to the relay gain employed and the selection of the relays utilized. In Chapter 3, it presents novel and easy-to-evaluate expressions for the error rate performance of cooperative dual-hop relaying with maximal ratio combining operating over independent generalized-X fading channels. In Chapter 4, it presents novel and easy-to-evaluate expressions for the performance of dual-hop relaying with best relay selection operating over generalized-X fading channels. In Chapter 5, it evaluates performance measures of multihop relaying systems operating in a composite fading environment modeled by the generalized-X distribution. By approximating the end-to-end signal-to-noise ratio of the multihop relay system by the minimum SNR of all the links, it provides easy to compute analytical expressions for the outage probability and the average bit and symbol error rates for a variety of digital modulation schemes. The derived expressions are validated by computer simulation and provide tight lower bounds to the exact performance of multihop relaying transmissions in a generalized fading environment. In Chapter 6 it derives closed-form lower bounds on the performance of multihop communication systems with non-regenerative relays operating in a Nakagami-m fading channel. The relay gains are assumed to be chosen to maximize the end-to-end SNR, which is bounded by the geometric mean of the positive random variables. Closed-form expressions are then derived for the statistics of the geometric mean of the optimum end-to-end SNR. These, in turn, are used to derive tight bounds for the outage as well as average error performances of the system. An upper bound is also derived for the mean ergodic capacity of the end-to-end SNR. Finally, in Chapter 7 it studies the effect of co-channel interference on the outage probability of dual-hop wireless communication systems with amplify-and-forward relaying operating in a Rayleigh fading channel.