3 research outputs found
Selection Combiner in Time-Varying Amplify Forward Cooperative Communication
This research presents the diversity combining schemes for Multiple Symbol Double Differential Sphere Detection (MSDDSD) in a time-varying amplify-and-forward wireless cooperative communication network. Four diversity combiners, including direct combiner, Maximal Ratio Combiner (MRC), semi MRC and Selection Combiner (SC) are demonstrated and explained in details. A comprehensive error probability and outage probability performance analysis are carried through the flat fading Rayleigh environment for semi MRC and SC. Specifically, error performance analysis is obtained using the PDF for SC detectors. Finally, power allocation expression based on error performance minimization approach is presented for the proposed SC performance optimization. It is observed that the performance analysis matches well with the simulation results. Furthermore, the proposed SC scheme offers better performance among the conventional MRC and direct combiner schemes in the presence of frequency offsets
Differential Modulation and Non-Coherent Detection in Wireless Relay Networks
The technique of cooperative communications is finding its way in the next
generations of many wireless communication applications. Due to the distributed
nature of cooperative networks, acquiring fading channels information for
coherent detection is more challenging than in the traditional point-to-point
communications. To bypass the requirement of channel information, differential
modulation together with non-coherent detection can be deployed. This thesis is
concerned with various issues related to differential modulation and
non-coherent detection in cooperative networks. Specifically, the thesis
examines the behaviour and robustness of non-coherent detection in mobile
environments (i.e., time-varying channels). The amount of channel variation is
related to the normalized Doppler shift which is a function of user's mobility.
The Doppler shift is used to distinguish between slow time-varying
(slow-fading) and rapid time-varying (fast-fading) channels. The performance of
several important relay topologies, including single-branch and multi-branch
dual-hop relaying with/without a direct link that employ amplify-and-forward
relaying and two-symbol non-coherent detection, is analyzed. For this purpose,
a time-series model is developed for characterizing the time-varying nature of
the cascaded channel encountered in amplify-and-forward relaying.Comment: PhD Dissertatio