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We analyze the performance of a cooperative multi-hop network with an incremental hop selection (IHS) scheme. Generally, multiple-relay networks based on half-duplex-mode relays undergo spectral efficiency loss due to the use of multiple time phases. The IHS scheme can prevent this problem because it increases the number of hops only when the currently selected path cannot support the target performance. Moreover, we apply an adaptive modulation technique to the IHS scheme to determine the additional spectral efficiency gain while maintaining the target performance. We evaluate the average spectral efficiency and the outage probability performances over the Nakagami- $m$ fading channel. Also, the diversity and coding gains are derived through the asymptotic outage probability in the high transmit SNR region. [ABSTRACT FROM PUBLISHER]

This paper presents an analysis of magnetic resonance coupling effects that can be considered for realizing a wireless power transfer (WPT) system. In this study, numerical analysis is applied to investigate the power transfer characteristics affected by coil inductance and placement. The simulations and experiments, using various coils and positions, are conducted to find the optimum power transfer condition. The experiment shows that the frequency bandwidth of the wireless power transfer at the optimum coupling condition is enlarged to 0.73 MHz and the transfer efficiency is maintained at over 80%. [ABSTRACT FROM PUBLISHER]

This letter proposes an incremental hop selection (IHS) scheme which improves network coverage while preventing spectral efficiency loss in half-duplex amplify-and-forward (HD-AF) protocol based multi-hop networks (MHNs). In contrast to the fixed N-hop networks, the proposed IHS scheme increases the number of hops only when the current selected path cannot support a performance threshold. Since the proposed scheme uses minimal time phases to satisfy the constraint, the spectral efficiency can be improved. Furthermore, we evaluate the outage probability and average spectral efficiency performance over Nakagami-m fading channel. The simulation results show that the proposed scheme outperforms the existing multiple relay schemes and the derived evaluations are valid. [ABSTRACT FROM PUBLISHER]

\boldmath This paper analyzes the performance of an amplify-and-forward (AF) protocol based cooperative multi-hop relay networks (CMHNs), where signals from the multi-hop relay network (MHN) and the direct path are considered in the detection, over the flat Nakagami-m fading channels. The analysis is accomplished by using the Beaulieu series that obtains a cumulative distributed function (CDF) through a characteristic function (CHF). Since the received SNR of MHN is mainly affected by the weakest channel in the network, we propose a hop selection scheme that prevents the performance degradation of the MHNs. We expand the CDF analysis to the networks employing proposed scheme by a tight bound of the received SNR. Also, in order to evaluate the diversity and coding gains of the proposed hop selection scheme, an asymptotic outage probability at high SNR region is derived. We show that the simulation results are closely matched to the analyzed results. [ABSTRACT FROM PUBLISHER]

This paper deals with the power allocation problem in a wireless relay network employing differential modulation technique and Alamouti distributed space-time code, where signals from both the direct and relay paths are taken into account in the detection process. We propose a sub-optimal power allocation scheme based on the maximization of an approximate receive covariance expression. The proposed scheme jointly allocates the transmit power of both the source and relay nodes under a total transmit power and per-node transmit power constraints. We can increase the effectiveness of the proposed power allocation algorithm by grouping the relays with respect to their individual covariances. Numerical experiments show that the proposed covariance maximization algorithm combined with the relay grouping algorithm offers a respectable BER performance improvement, compared to the conventional schemes. Finally, we demonstrate that the proposed scheme requires only a small number of iterations to achieve convergence, making it attractive to practical systems. [ABSTRACT FROM PUBLISHER]