Simulation, Analysis, and Optimization of spatial multiplexing in WLAN Massive MIMO systems

Massive MIMO is a new technology that has the potential to improve wireless communication performance, in particular spectral efficiency, by spatially multiplexing different user equipments (UEs) using many antennas at the access point (AP). In this thesis we provide an in-depth study of a Massive MIMO implementation with wireless local area network (WLAN). We analyze and optimize signal processing and channel estimation techniques to reduce complexity and enable efficient Massive MIMO operation. A Massive MIMO system supported by the current WLAN specification (IEEE 802.11ax) is designed and simulated. It accounts for the main sources of overhead for both uplink (UL) and downlink (DL) (with transmit beamforming (TxBF)) transmissions. We investigate how the overhead affects spatial multiplexing gain in a single cell WLAN Massive MIMO network as the number of antennas at the AP and UEs increases. We first develop two overhead models, the UL and DL overhead efficiency factor, that provide accurate results to examine overhead impact in different configurations without the requirement for simulations. Then, we identify the main issues and propose solutions that reduce its impact on the performances. We determine ideal pairs of AP antennas and spatially multiplexed UEs that maximize SE in UL and DL. Finally we demonstrate that Massive MIMO is worthwhile for UL transmissions, while the benchmark (OFDMA) solution with TxBF remains preferable for DL transmissions.