Showing papers by "Mohammad Shikh-Bahaei published in 2014"

Packet error rate-based adaptive rate optimisation with selective-repeat automatic repeat request for convolutionally-coded M-ary quadrature amplitude modulation systems

Abstract: Link adaptation using adaptive modulation and coding (AMC) is a popular physical layer technique for efficient use of time-varying fading channels. Using a cross-layer approach, AMC and truncated automatic repeat request scheme at data link layer are jointly considered. For a convolutionally-coded M-ary quadrature amplitude modulation system under block fading channel condition, a variable rate transmission scheme that uses imperfect channel state information is derived. First, a closed-form expression for approximating packet error rate (PER) is found as a function of coded information rate. It is then shown that by solving an optimisation problem using this expression, optimum transmission rate can be determined in a way that maximises the spectral efficiency while satisfying an average PER constraint. Hence, the parameters in physical and medium access control layers are incorporated in the analysis.

Cross-layer resource allocation for video streaming over OFDMA cognitive radio networks with imperfect cross-link CSI

Abstract: In this paper, novel cross-layer radio resource allocation (RRA) algorithm is proposed in the context of Orthogonal frequency division multiple access (OFDMA)-based cognitive radio (CR) video application systems. User video quality and channel awareness are incorporated in the design, to exploit joint optimization of rate and power for secondary receivers (SRs), subject to minimum SR video quality and primary receiver (PR) interference threshold constraints. Firstly, the relationship between PR interference margin and power limits at the secondary transmitter (ST) is analytically derived. Then, to provide PRs with satisfactory quality of service (QoS), we propose a new probabilistic approach to mitigate the total imposed interference of the ST on PRs, considering imperfect ST to PR channel state information (CSI). The effect of PR interference limit violation probability, interference threshold, and error variance of imperfect CSI are evaluated using computer simulations. Results indicate that significant improvement in SR total video quality is achieved through our proposed algorithm over other state-of-the-art Non-Quality-Aware (NQA) designs in the literature. The enhanced performance was obtained whilst guaranteeing SR minimum quality and PR prescribed QoS constraints.

Resource Allocation and Interference Management for Adaptive Modulation and Coding-Based OFDMA Cognitive Radio Networks

Abstract: Radio resource allocation (RRA) algorithms are developed to enhance the spectral efficiency of downlink adaptive modulation and coding (AMC)-based orthogonal frequency-division multiple access (OFDMA) cognitive radios (CRs) under average transmit and peak interference power constraints. We consider the practical case of noisy channel-state-information (CSI) between cognitive transmitter (CTx) and primary receiver (PRx), and design novel interference management techniques to model and control the CR-inflicted interference on licensed spectrum. An expression for the cumulative density function (cdf) of the CRs' received signal-to-interference-plus-noise ratio (SINR) is developed to evaluate the resultant average spectral efficiency. Simulation results reveal that by adopting the joint resource allocation and interference management framework a considerable performance gain in the AMC-based OFDMA CR network is achieved over the conventional optimization methods.

Cross-layer radio resource allocation for multi-service networks of heterogeneous traffic

Abstract: A cross-layer design framework, in the sense of maximizing sum-throughput, is proposed for a multi-service network of heterogeneous traffic. Considering different prescribed target packet loss rates and maximum automatic repeat request (ARQ) delays for the services in the data link control (DLC)-layer, we derive the respective optimum signal-to-interference-plus-noise ratio (SINR)-targets and variable spreading factor (VSF)s of the services in the physical (PHY)-layer, analytically as functions of the multi-user interference (MUI) and fading fluctuations. A multi-dimensional Markov chain is employed to model the packet traffic characteristics in the network. Performance of the proposed optimized cross-layer system is demonstrated and compared to state-of-the-art universal mobile telecommunication system (UMTS) standard, with conventional power, rate, and error control, for various practical system settings using theoretical and simulation results. Considerable improvement in sum-throughput performance of the multi-service mobile communication network is achieved through joint optimization of PHY-layer and DLC-layer parameters, whilst satisfying unique quality of service (QoS) constraints of different traffic types.