A novel equivalent definition of modified Bessel functions for performance analysis of multi-hop wireless communication systems

A statistical model is derived for the equivalent signal-to-noise ratio of the Source-to-Relay-to-Destination (S-R-D) link for Amplify-and-Forward (AF) relaying systems that are subject to block Rayleigh-fading. The probability density function and the cumulated density function of the S-R-D link SNR involve modified Bessel functions of the second kind. Using fractional-calculus mathematics, a novel approach is introduced to rewrite those Bessel functions (and the statistical model of the S-R-D link SNR) in series form using simple elementary functions. Moreover, a statistical characterization of the total receive-SNR at the destination, corresponding to the S-R-D and the S-D link SNR, is provided for a more general relaying scenario in which the destination receives signals from both the relay and the source and processes them using maximum ratio combining (MRC). Using the novel statistical model for the total receive SNR at the destination, accurate and simple analytical expressions for the outage probability, the bit error probability, and the ergodic capacity are obtained. The analytical results presented in this paper provide a theoretical framework to analyze the performance of the AF cooperative systems with an MRC receiver

Performance analysis of relay-aided wireless communication systems

Relay-aided networks have been proved to be cost-efficient solutions for wireless communications in respect of high data rates, enhanced spectrum efficiency and improved signal coverage. In the past decade, relaying techniques have been written into standards of modern wireless communications and significantly improve the quality of service (QoS) in wireless communications. In order to satisfy exponentially increased demands for data rates and wireless connectivities, various novel techniques for wireless communications have been proposed in recent years, which have brought significant challenges for the performance analysis of relaying networks. For the purpose of more practical investigations into relaying systems, researchers should not only analyse the relays employing novel techniques but also attach more importance to complex environments of wireless communications. With these objectives in mind, in this thesis, in-depth investigations into system performance for relay-assisted wireless communications are detailed. Firstly, the theoretic reliability of dual-hop amplify-and-forward (AF) systems over generalised η-μ and κ-μ fading channels are investigated using Gallager’s error exponents. These two versatile channel models can encompass a number of popular fading channels such as Rayleigh, Rician, Nakagami-m, Hoyt and one-sided Gaussian fading channels. We derive new analytical expressions for the probability distribution function (pdf) of the end-to-end signal-to-noise-ratio (SNR) of the system. These analytical expressions are then applied to analyse the system performance through the study of Gallager’s exponents, which are classical tight bounds of error exponents and present the trade-off between the practical information rate and the reliability of communication. Two types of Gallager’s exponents, namely the random coding error exponent (RCEE) and the expurgated error exponent, are studied. Based on the newly derived analytical expressions, we provide an efficient method to compute the required codeword length to achieve a predefined upper bound of error probability. In addition, the analytical expressions are derived for the cut-off rate and ergodic capacity of the system. Moreover, simplified expressions are presented at the high SNR regime. Secondly, the performance of a dual-hop amplify-and-forward (AF) multi-antenna relaying system over complex Gaussian channels is investigated. Three classical receiving strategies, i.e. the maximal-ratio combining (MRC), zero-forcing (ZF) and minimum mean square error (MMSE) are employed in the relay to mitigate the impact of co-channel interference (CCI), which follows the Poisson point process (PPP). We derive the exact analytical expressions of the capacities for this system in the infinite-area interference environment and the asymptotic analytical expressions for the lower bounds of capacities in the limited-area interference scenario. By computing the numerical results and the Monte Carlo simulation, we can observe the effect of relay processing schemes under different interference regimes. In the end, the non-orthogonal multiple access (NOMA) technique is introduced to relaying systems, which exploits multiplexing in the power domain. Order statistics are applied in this part to analyse the performances of ordered users. The randomness of both channel fading and path loss are taken into consideration. In addition to the exact analytical expressions, asymptotic expressions at high-SNR regimes are provided, which clearly show the effects of NOMA techniques using at relaying systems

Cognitive Multihop Wireless Sensor Networks over Nakagami-m Fading Channels

This work is supported by the National Science Foundation of China (NSFC) under Grant 61372114, by the National 973 Program of China under Grant 2012CB316005, by the Joint Funds of NSFC-Guangdong under Grant U1035001, and by Beijing Higher Education Young Elite Teacher Project (no. YETP0434)

Error exponent of amplify and forward relay networks in presence of I.I.D. interferers

© 2014 IEEE. In this paper, we derive the random coding error exponent of amplify-and-forward (AF) relay networks in presence of arbitrary number of independent and identically distributed (i.i.d.) interferers both at the relay and the destination. Multiuser networks are common examples of interference limited networks. We derive the ergodic capacity of the network and present simulation results on the performance of the network where we compare the capacity and error exponent performance of interference limited networks with noise limited networks. Numerical results show that noise limited networks outperform interference limited networks even when only a very few interferers exist in the network

Performance Analysis of Optimal Single Stream Beamforming in MIMO Dual-Hop AF Systems

This paper investigates the performance of optimal single stream beamforming schemes in multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) systems. Assuming channel state information is not available at the source and relay, the optimal transmit and receive beamforming vectors are computed at the destination, and the transmit beamforming vector is sent to the transmitter via a dedicated feedback link. Then, a set of new closed-form expressions for the statistical properties of the maximum eigenvalue of the resultant channel is derived, i.e., the cumulative density function (cdf), probability density function (pdf) and general moments, as well as the first order asymptotic expansion and asymptotic large dimension approximations. These analytical expressions are then applied to study three important performance metrics of the system, i.e., outage probability, average symbol error rate and ergodic capacity. In addition, more detailed treatments are provided for some important special cases, e.g., when the number of antennas at one of the nodes is one or large, simple and insightful expressions for the key parameters such as diversity order and array gain of the system are derived. With the analytical results, the joint impact of source, relay and destination antenna numbers on the system performance is addressed, and the performance of optimal beamforming schemes and orthogonal space-time block-coding (OSTBC) schemes are compared. Results reveal that the number of antennas at the relay has a great impact on how the numbers of antennas at the source and destination contribute to the system performance, and optimal beamforming not only achieves the same maximum diversity order as OSTBC, but also provides significant power gains over OSTBC.Comment: to appear in IEEE Journal on Selected Areas in Communications special issue on Theories and Methods for Advanced Wireless Relay