Multi-hop relaying is an important concept in future generation wireless networks. It can address the inherent problems of limited capacity and coverage in cellular networks. However, most existing multi-hop relaying architectures waste energy. In this paper, our goal is to find a power-effective multihop relaying architecture, since the problem of coverage extension may occur in the given target service area where users' traffic density is relatively low or moderate, this paper introduces several popular topologies and the corresponding coverage extension methods for each case. Further, sets up the optimized mathematical model and obtain the simulation results which show that Type-D is the best topology which consumes less power than Type-A, Type-B and Type-C.
In this paper, we propose an adaptive multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system based on quasi-orthogonal space time/frequency block coding (QO-STBC/SFBC) with an improved angle feedback scheme. First we exploit the improved feedback scheme which can minimize the non-orthogonality of QO-STBC/SFBC by rotating constellation symbols. Then we investigate its quantification method and the related criterions. Furthermore, we apply the adaptive modulation technique to this scheme in frequency selective channel. Simulation results show that the proposed feedback scheme can provide higher signal-tonoise ratio (SNR) gains, and systems with such scheme can get significant improvement by applying adaptive modulation technique.
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