Adaptive Cross-Layer Strategies for Fourth Generation Wireless Communications

Copyright © 2010 Mohammad Shikh-Bahaei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Ubiquitous support of heterogeneous services with prescribed QoS requirements is an ever-increasing demand in the fourth generation of wireless communication systems. Unpredictable and variable nature of environment and scarcity of resources necessitate exploiting efficient adaptive resource allocation strategies in operating the emerging networks. Recent growth in popularity of high-data rate-applications and the need for larger bandwidths for transmission of multimedia content have also made the ideas of " resource sharing " and " cognitive radio " very attractive. Again sharing or allocation of resources should be dynamic and adapted to the network condition. On the other hand, for attaining the optimal perceived quality, QoS requirements and the respective resource allocation techniques for the new wireless applications should be considered across the open system interconnection (OSI) layers. For example, quality of video streaming application is best measured at higher layers, while this quality is affected by resource allocation within lower layers. This special issue aims to shed light on the above concepts from a number of perspectives. The first paper " Particle swarm optimization (PSO) for adaptive resource allocation in communication networks " focuses on adaptive centralized and distributed resource allocation strategies in communication networks. For a low-complexity design, a generalized model of particle swarm optimization (PSO) technique is used. By deploying the concept of PSO for subcarrier allocation, the required computational complexity and traffic overheads are significantly lowered. The next three papers study adaptive cross-layer schemes in cognitive radio (CR) systems. The paper " A cross-layer approach in sensing and resource allocation for multimedia transmission over cognitive UWB networks " studies medium access control (MAC) centric cross-layer approach to address the problem of multime-dia transmission over cognitive ultra wideband (C-UWB) networks. This paper proposes a cross-layer design while considering UWB wireless channel conditions, time slot allocations at the MAC layer, and MPEG-4 video at the APP layer. Then, the performance of the proposed approach is investigated. The paper " Cross-layer design in dynamic spectrum sharing systems " in this special issue proposes to employ a cross-layer design policy that incorporates adaptive power and coded discrete M-QAM modulation scheme into the physical layer with a truncated automatic repeat request (ARQ) protocol at the data …