In this paper, we consider the wideband spectrum sensing in which primary users use OFDM modulation. Pulse shape of each subchannel is non-ideal which results in the leakage of power among adjacent subchannels. This phenomenon makes the received energy of each subchanne More
In this paper, we consider the wideband spectrum sensing in which primary users use OFDM modulation. Pulse shape of each subchannel is non-ideal which results in the leakage of power among adjacent subchannels. This phenomenon makes the received energy of each subchannel (test statistic of energy detector) correlated with those of other subchannels. Therefore, in order to jointly detect the state of primary network subchannels, we propose a simple iterative method and we observe its performance improvements in comparison to the disjointed method (in which the detection of each subchannel state is independent of the detection of other s
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Spatial diversity is one of the most effective techniques to combat fading in wireless channels that can be implemented through antenna arrays. In this paper the hybrid decode-amplify-forward protocol with best relay selection (HDAF-S)in a cooperative system with multip More
Spatial diversity is one of the most effective techniques to combat fading in wireless channels that can be implemented through antenna arrays. In this paper the hybrid decode-amplify-forward protocol with best relay selection (HDAF-S)in a cooperative system with multiple parallel relays with independent non-identically channels is considered and tight upper and lower bounds on bit error rate (BER) of this protocol is derived. It is shown that the BER of this protocol outperforms the BER of amplify and forward (AF) protocol but cannot exceeds the performance of decode and forward (DF) protocol. Then through asymptotic analysis for high SNR regime, it is shown that the HDAF-S protocol achieves full diversity order. Then the BER performance of HDAF protocol with n-th best relay selection (HDAF-nS) in independent and identically distributed channels is analyzed and tight upper and lower bounds on the BER are derived. Asymptotic analysis shows that this protocol cannot achieve full diversity order and it is shown that the diversity order decreases as n increases. The analytical results are validated through simulations.
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In this paper, a cooperative network consisting of one source, one relay, and one destination is considered. The source and the destination are both single-antenna systems, while the relay is equipped with N antennas and operates in decode-and-forward (DF) mode. We assu More
In this paper, a cooperative network consisting of one source, one relay, and one destination is considered. The source and the destination are both single-antenna systems, while the relay is equipped with N antennas and operates in decode-and-forward (DF) mode. We assume that there is no direct link between the source and the destination. We propose two beamforming methods at the relay to transmit the data to the destination. Beamforming is performed at the relay by the assumption of having two bit quantized information about the phase of all links between the relay and the destination. We derive an upper bound on bit error probability of the system and show that the proposed scheme achieves full diversity order. Simulation results illustrate that performance of the system in terms of bit error probability is better than some well-known scenarios and is close to some scenarios with ideal assumptions.
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