Analysis of multivariate generalized Gaussian fading distributions with applications to diversity receivers | |
| Author | Dharmawansa, Prathapasinghe |
| Call Number | AIT Diss. no.ICT-07-01 |
| Subject(s) | Radio transmitters and transmission--Fading Orthogonal frequency division multiplexing |
| Note | A dissertation submitted in patial fullfillment of the requirements for the degree of Doctor of Engineering in Information and Communications Technologies, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ICT-07-01 |
| Abstract | The Adversarial effects of fading can be mitigated by diversity techniques. However, the performance analysis of many diversity combining techniques with higher diversity order remains incomplete due to the unavailability of the multidimensional density functions of the correlated fading processes. The motives behind this research work are twofold; first, to derive the higher order densities for fading processes, and next, to analyze the performance of more general diversity receivers over generalized Gaussian fading channels. In relation to higher order densities, we derive new infinite series representations for trivariate and quadrivariate Nakaganli distributions, trivariate Rician distribution and trivariate non-central Chi-Squared distribution. With those derivations, we generalize most of the previous studies regarding the multivariate fading envelopes and unveil more scope in the wireless system analysis. An approach due to Miller is used in all of the multidimensional fading envelope analysis and we show that our formulas are the most optimum with his approach. Related joint statistics, namely cumulative distribution function and characteristic function, are also derived in the form of nested infinite series. In addition to multivariate envelopes we consider the density of sum of AI independent and identically distributed Nakagami random variables in view of deriving a more general expression. The resultant formula is in the form of nested infinite summations and not as elegant as the suns of two variables, which consists of the confluent hypergeometric function. Nevertheless, the convergence of infinite series are explicitly addressed in many scenarios discussed here. Even though the applications of multivariate densities are numerous in the context of wireless communications, we consider a few of them related to the diversity receivers over correlated fading environments. Performance degradation due to the fading correlation is observed clearly from our results. Furthermore, novel formulas for the distributions of envelope and phase of two correlated Gaussian variables are also derived. Subsequently those formulas are applied in analyzing the bit error rate (BER) performance of binary frequency shift keying (BFSK) systems with inphase-quadrature (I/Q) imbalance at the receiver. Orthogonal frequency division multiplexing (OFDM), which is well known for its low complexity equalization capability in frequency selective fading channels, is more sensitive to the frequency offset errors. However, no exact analysis has ever been performed on the performance of OFDM in the presence of frequency offset error. Hence, we derive exact BER/symbol error rate (SER) expressions for the impaired OFDM systems over additive white Gaussian noise (AWGN) and Rayleigh fading channels. The main drawback of our exact results is the exponential computational complexity associated with them which limits their practical applicability for systems with large number of OFDM carriers. Nonetheless, we show that relatively good accuracy can be retained even for a large number of carriers by truncating the number of ICI terms |
| Year | 2007 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertations ; no. ICT-07-01 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Information and Communication Technology (ICT) |
| Chairperson(s) | Rajatheva, R. M. A. P; |
| Examination Committee(s) | Ahmed, Kazi M.;Erke, Tapio J.;Iripathi, Nitin K. I;Adachi, Furniyuki,; |
| Scholarship Donor(s) | Government of Finland; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2007 |