Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e. policies) potentially provide significant performance gains for various systems. In this paper we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by the means of dynamic resource allocation. Two specific areas are treated separately: Models and dynamic approaches for single transmitter/receiver pairs-i.e. a point-to-point communication scenario-as well as models and approaches for point-to-multi-point communication scenarios-such as the down-link of a wireless cell. This paper provides the basic knowledge in order to investigate future OFDM cross-layer-optimization issues.
Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMAILTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally distributes power and resource blocks among the users of the network. It is shown that large differences exist between the performance of different mask types and the optimal case in both, the overall cell throughput, as well as the cell-edge user performance.
Abstract-one of the major challenges in designing cellular Cognitive Radio (CR) networks is the avoidance of Secondary User (SU) interference to so called Primary Users (PUs) operating in the licensed bands. Usually, SU operation has to be interrupted periodically in order to detect PU activity and avoid the respective frequencies. Recently, Dynamic Frequency Hopping (DFH) mechanisms have been suggested to enable reliable PU detection and continuous SU operation at the same time. Applying DFH in a multi-cell environment adds the challenge of mitigating Co-Channel Interference (CCI). In this paper, we introduce a new DFH approach for cellular CR networks to allow reliable PU detection and continuous SU operation while avoiding CCI: Double Hopping (DH). We present a distributed frequency assignment heuristic for DH and compare it to the optimal assignment. We show that the performance of the suboptimal distributed assignment is only slightly worse than the optimal performance, and, thus, outperforms existing distributed approaches by far.
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