Loading...

Harnessing Interference in Cooperative Communication Networks

Hejazi, Mohsen | 2016

1064 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49554 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Nasiri-Kenari, Masoumeh
  7. Abstract:
  8. The compute-and-forward (CMF) method has shown a great promise as an innovative approach to exploit interference towards achieving higher network throughput. Here, instead of recovering single messages, the relays attempt to reliably decode (compute) and pass an integer linear combination of the transmitted messages, referred to as an equation, to the destination. By receiving sufficient equations,the destination can solve the linear equation system to recover the desired messages.Two main challenges of the CMF methods are the computational complexity and the rank failure problem at the destination. In this thesis, to decrease the implementation as well as the computational complexity of the CMF method, we propose the simplified CMF (SCMF) method that limits the search set of the CMF optimization problem to be selected from a predetermined small-size set. Through analytical and simulation evaluations, we show that the SCMF presents nearly the same performance as the original CMF in low SNR regimes (where the SNR is below a certain threshold), and is more robust against channel estimation error (CEE) than the original CMF.Moreover, to solve the rank failure problem in CMF setups and to achieve full diversity of the network, we introduce two novel CMF methods, namely, extended CMF and successive CMF. The former, having low complexity, is based on recovering multiple equations at relays. The latter utilizes successive interference cancellation (SIC) to enhance the system performance compared to the stateof-the-art schemes. Both methods can be utilized in a network with different number of users, relays, and relay antennas, with negligible feedback channels or signaling overhead. We derive new concise formulations and explicit framework for the successive CMF method as well as an approach to reduce its computational complexity. Our theoretical analysis and computer simulations demonstrate the superior performance of the both proposed CMF methods over the conventional schemes. Furthermore,based on our simulation results, the successive CMF method yields additional signal-to-noise ratio gains and shows considerable robustness against channel estimation error, compared to the extended CMF method.Finally, considering the Gaussian multiple access channel (MAC), the computation of a fixed desired equation at the relay is analyzed. Based on the CMF methods, we propose two novel computation algorithms, namely, the optimum multi-stage with no equations feedback (MS-NF) and the optimum multi-stage with equations feedback (MS-EF). We show that the number of required lattice decoding stages in each algorithm is at most the number of the MAC users. Furthermore, we prove that the optimum MS-EF algorithm is optimum among all Gaussian MAC computation algorithms in terms of the computation rate of the desired equation at the relay
  9. Keywords:
  10. Compute and Forward ; Cooperative Network ; Outage Probability ; Gaussian Multiple-Access Channel ; Relay Network ; Multiuser Network ; Relaying Strategies ; Diversity Order ; Exploiting Interference

 Digital Object List

 Bookmark

...see more