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An OFDM based cognitive radio (CR) network is considered in this paper. The goal is to maximize the total sum rate of the CR system while ensuring that no excessive interference is induced to the primary system. The optimal scheme adopts the dual decomposition technique and in order to reduce the computational complexity of the optimal scheme, a greedy suboptimal algorithm is proposed. Selected numerical...
A novel intra-cell frequency planning scheme based on interference coordination is exploited for cellular Orthogonal Frequency Division Multiplexing (OFDM)-Relay systems. In this strategy, a factor RI is introduced to model the interference in the 2nd slot. According to RI and the signal-to-interference-plus-noise ratio, the scheduler groups all the users into three sets. Furthermore, the total spectrum...
We maximize the minimum rate among sources in a multi-source, multi-relay, single destination cooperative network. The relays use the decode-and-forward protocol while all transmissions use orthogonal frequency division multiplexing. The key to our approach is fractional cooperation: there may be fewer relays than sources and not all source subcarriers are relayed. Optimal matching of the sources...
This paper aims to improve capacity in multi-hop OFDM system with non-regenerative relaying based on power allocation. The capacity model is presented, power allocation is analyzed based on the subsignal tuned to subcarrier of OFDM. Power allocation is decomposed to two subproblems. The first subproblem is the optimal power allocation to every hop of subsignal, when the power of each subsignal is...
In this paper, we propose a robust STBC transmission scheme to combat the timing synchronization errors over frequency-selective multiple-access channels. First, the equivalent channel model in the presence of timing synchronization errors is derived and we find that the synchronization errors result in an equivalent channel model with larger number of correlated channel taps. Based on this correlated...
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