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Orthogonal frequency division multiplexing (OFDM) communication systems require accurate estimation of timing offset and channel impulse response in order to achieve desirable performance. In this paper, we consider the optimal placement of pilot symbols over the OFDM subcarriers in order to minimize a function of the Cramér-Rao bound on these parameters. Previous work has investigated this problem...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
Cyclic delay diversity (CDD) is a simple transmit diversity technique for coded OFDM systems with multiple transmit antennas. It is applicable to existed wireless communication systems since it does not need modifications of the standard OFDM receiver. However, CDD causes serious degradation in the performance of post-FFT estimation, i.e., integer frequency offset (IFO). This paper suggests pilot...
Three applications in wireless networks where model-free stochastic learning is applicable, are discussed. The learning based optimization problems are formulated and simulation results are presented. Some open issues are also discussed.
As Grid networks grows, the complexity of resource management in Grid networks dramatically increases. To manage the Grid resources efficiently, policy based resource management system is suitable. However, the policy which made at a moment could not be appropriate to other time because the condition of the grid resources with time space changes. Thus, in this paper, we propose asynchronous policy-based...
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