Advanced MIMO Techniques for Long Term Evolution

Abstract

In modern wireless networks, the throughput achieved by the edge users is a key performance indicator of the network. Enhancing the edge user throughput can be achieved through mitigating intercell interference. Long term evolution (LTE) in- troduces a new technique for interference mitigation through coordination between BSs denoted as coordinated multipoint (CoMP) transmission reception systems. CoMP promises an enhanced edge user downlink throughput, especially in TDD systems. Radio frequency (RF) calibration is necessary for proper CoMP opera- tion. In this thesis, the RF calibration problem in CoMP systems is discussed and analyzed and new techniques are proposed. We study the performance of di erent CoMP schemes and di erent precoders under RF mismatch calibration errors. Numerical results are provided which show the best precoder and the best CoMP mode candidates given di erent SNR and calibration error levels. In addition, a new iterative MMSE-based calibration scheme is introduced and simulation results are provided showing superior performance compared to tra- ditional algorithms. Moreover, a new mobility-aware calibration point selection algorithm is proposed for di erent types of calibration in CoMP systems. Full xv xvi mathematical formulations for the optimization problems are provided. Finally, system simulation results are presented showing the performance of the proposed solutions compared to other algorithms in the literature. keywords: MIMO, RF calibration, LTE-A, cell edge user, CoMP, coordinated beamforming, joint transmission and MMSE.