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Performance Analysis and Power Optimization of Cooperative Networks with Channel Estimation Errors

Tabataba, Foroogh Sadat | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42760 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Pakravan, Mohammad Reza; Sadeghi, Parastoo
  7. Abstract:
  8. Cooperative communications have been introduced to combat degrading effects of fading in wireless networks and attracted much attention recently. This technique provides distributed spatial diversity that enables energy-efficient transmission of information from source nodes to destination nodes via intermediate relay nodes. Most existing protocols, detection techniques and optimization methods in cooperative networks assume that perfect channel state information is available. While in practical situations, the estimates of the channels may only be known and for acquiring such knowledge, a fraction of power and bandwidth have to be spent for channel estimation using pilot symbols. In this dissertation, we aim to study the performance of fundamental important structures of cooperative networks in presence of channel estimation errors and to optimize power allocation in these systems analytically without perfect channel state information. We consider two popular structures for one-way relaying named as dual-hop one-way relaying and one-way relaying with the direct link. We also investigate two important two-way structures called traditional routing and analog network coding. Channel estimation error makes the analysis complicated and we are looking for suitable simplifying approximations to find simple closed-form solutions. We derive outage probability and capacity upper or lower bounds in Rayleigh fading channels for one-way relaying and two-way relaying structures, respectively. Due to the impact of optimum power allocation on performance improvement and estimation error reduction, we analytically optimize the power of pilot and data symbols for each structure. We optimize the performance of each system subject to a given power constraint and derive closed-form solutions for power ratios. The proposed power allocation schemes do not depend on instantaneous channel information and can be used in practice. We also introduce outage-dependent power constraint applicable for incremental relaying schemes. This constraint is more efficient and effective in using the power budget of the system compared to traditional power constraint. We investigate the accuracy of the analysis and optimizations by Monte-Carlo simulations. It is shown that the provided simplifying approximations are reasonable and can be used in similar problems. Moreover, analytical results are matched to simulation results in many situation of interest. We also show that optimal power allocation can help alleviate the adverse affects of channel estimation errors and improves the performance towards ideal error-free situations.
  9. Keywords:
  10. Cooperative Network ; Channel Estimation ; Dropping Probability ; Optimal Power Allocation ; Capasity Bound

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