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Energy and spectrum efficiency in wireless cooperative networks

Qing Chen, University of Nebraska - Lincoln


To effectively combat the channel fading and increase the reliability of wireless networks, this thesis first studies the cross-layer design on the energy efficiency and the end-to-end throughput by incorporating modulation optimization, cooperative transmission and bi-direction communication strategies. Initially, we investigate the modulation optimization and the optimal routing in a multi-hop linear network under certain quality of service (QoS) constraints. Subsequently, we propose a 3-node cooperative network that operates in either Amplify-and-Forward (AF) or Decode-and-Forward (DF) mode, in which the cooperative transmission mechanism as well as the system performance is thoroughly analyzed with or without the presence of maximum ratio combining (MRC). Moreover, we study the trade-off between the physical-layer reliability and the successful throughput by performing a cross-layer optimization to maximize the system goodput of the cooperative networks that employ the Automatic Repeat reQust (ARQ) technique. In the second part of this thesis, we propose the two-way relay networks in Rayleigh fading channels and model the network state transition by Markov chain in both AF and DF modes. The goodput and average bit energy consumption (BEC) are optimized with respect to the fixed transmission rate. In a multi-relay scenario, the opportunistic relaying under the distributed selection algorithm is adopted and significant improvement is shown on the spectrum and energy efficiency. We further consider a multi-relay DF two-way network with a priori unknown Rayleigh fading channels. Minimum mean square error (MMSE) estimation via pilot symbol training is employed to estimate the channel fading coefficients. The worst-case average achievable rate regions are investigated under different power and resource allocation strategies in both multi-access channel (MAC) and broadcast channel (BC). Later, we outline a BC-channel architecture of adaptive modulation with partial XOR coding and selective ARQ in two-way relay networks. Upon satisfying a given packet loss constraint, the modulation and demodulation modes are determined by a two-dimensional SNR region partition and a significant spectrum efficiency gain can be achieved in this setting.

Subject Area

Electrical engineering

Recommended Citation

Chen, Qing, "Energy and spectrum efficiency in wireless cooperative networks" (2012). ETD collection for University of Nebraska - Lincoln. AAI3546596.