In cooperative relaying, intermediate stations are required to enhance the end-to-end transmission performance. The performance of the cooperative relaying scheme has been investigated theoretically and via computer s...
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In cooperative relaying, intermediate stations are required to enhance the end-to-end transmission performance. The performance of the cooperative relaying scheme has been investigated theoretically and via computer simulations. However, cooperative relaying using transmit diversity techniques in actual environments has not been investigated thus far. This paper presents an experimental system for distributed cooperative relaying using space-time block code and evaluations of its transmission performances in real propagation channels. To this end, four wireless stations-specifically, one source, two relays, and one destination-were developed using analog transceivers and field-programmable gate arrays for real-time digital signal processing. Sample timing and frequency synchronizations among the four wireless stations were established by using the received signals as a reference. The end-to-end error performance of distributed cooperative relaying was compared to those of noncooperative relaying schemes, and the performances of three relaying schemes were evaluated quasisimultaneously in terms of their cumulative distribution functions of the bit-error ratios (BERs). The experimental results indicated that the BER performance of the two-hop distributed cooperative relaying scheme was substantially superior to those of noncooperative two-hop relaying schemes, including a route diversity scheme.
We consider efficient communications over the multiple-input multiple-output (MIMO) multiway distributed relay channel (MDRC) with full data exchange, where each user, equipped with multiple antennas and broadcasts me...
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We consider efficient communications over the multiple-input multiple-output (MIMO) multiway distributed relay channel (MDRC) with full data exchange, where each user, equipped with multiple antennas and broadcasts messages to all the other users via the help of a number of distributive relays. We propose a physical-layer network coding (PNC)-based scheme involving linear precoding for channel alignment, nested lattice coding for PNC, and lattice-based precoding for interference mitigation. Unlike most existing approaches characterizing the degrees of freedom of MIMO multiway relay channels, we focus on analyzing the rate gap of the proposed scheme towards the fundamental channel capacity. In this regard, we establish a sufficient condition on the system configuration for that distributive relaying achieves the same sum rate as cooperative relaying does in the high SNR regime. We further show that the proposed scheme achieves the asymptotic sum capacity of the MIMO MDRC within a constant gap in the high SNR regime. Numerical results demonstrate that the proposed scheme considerably outperforms the existing schemes including decode-and-forward and amplify-and-forward.
We consider efficient communications over the multiple-input multiple-output (MIMO) multiway distributed relay channel (MDRC) with full data exchange, where each user, equipped with multiple antennas, broadcasts its m...
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ISBN:
(纸本)9781509059355
We consider efficient communications over the multiple-input multiple-output (MIMO) multiway distributed relay channel (MDRC) with full data exchange, where each user, equipped with multiple antennas, broadcasts its message to all the other users via the help of a number of distributive relays. We propose a physical-layer network coding (PNC) based scheme involving linear precoding for channel alignment, nested lattice coding for PNC, and lattice-based precoding for interference mitigation. We show that distributed relaying achieves the same sum-rate as cooperative relaying in the high SNR regime in most scenarios, which implies that the proposed scheme with distributed relays is more suitable for practical systems than the schemes with cooperative relays.
Due to signal fading and user mobility in wireless networks, quality-of-service provisioning for wireless services has become more challenging. As a promising technique, cooperative communications make use of the broa...
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Due to signal fading and user mobility in wireless networks, quality-of-service provisioning for wireless services has become more challenging. As a promising technique, cooperative communications make use of the broadcasting nature of the wireless medium to facilitate data transmission and, thereby, reduce energy consumption. However, in many studies on wireless cooperative diversity, it is often assumed that the number of relays or the relay distribution intensity is known a priori. In this paper, we relax this assumption and propose an algorithm to estimate the relay intensity for a backoff-based cooperative scheme, where the relays are distributed as a homogeneous Poisson point process. It is proved that the algorithm can converge to an optimal solution with the minimum estimation error. Based on the estimated relay intensity, we further investigate a distributed energy saving strategy, which selectively turns off some relays to reduce energy consumption while maintaining the required transmission success probability. The performance of the proposed cooperative scheme is analytically evaluated with respect to the collision probability. The numerical and simulation results demonstrate the high accuracy and efficiency of the intensity estimation algorithm and validate the theoretical analysis. Moreover, the proposed cooperative scheme exhibits significant energy savings and satisfactory transmission performance, which offers a good match to accommodate green communications in wireless networks.
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