Indoor LOS MU-MIMO: efficient bandwidth usage of a geographical area
University of New Brunswick
Multiuser multi-input multi-output (MU-MIMO) systems are well known to provide performance improvements as compared with single-antenna systems. This thesis investigates the performance of a line-of-sight (LOS) MU-MIMO system present in an office environment. The main focus of this thesis is to demonstrate the effect of allocated user baseband bandwidth on the performance of a bandlimited MU-MIMO system. The condition number of a received channel matrix is used as a performance criterion for a MU-MIMO system. In addition, the effect of geographical dimensions of an office environment on the system's analog-to-digital converters (ADCs) dynamic-range requirements is investigated. The average MU-MIMO bandwidth requirements of an office environment are investigated. The relationship among the physical dimensions of an office environment, average MU-MIMO bandwidth and ADC's dynamic-range requirements is developed. The new term 90-50 MU-MIMO Bandwidth (90-50 MMB) is coined to indicate the MU-MIMO bandwidth of an office environment which results in the existence of an efficient MU-MIMO system over 90% of the portable user locations within an office environment with at least 50% usage of the dynamic range of the system's ADCs. The hypothesis is proposed to estimate the 90-50 MMB of an office environment based on the physical dimensions of an office environment. A 2 x 2 prototype MU-MIMO system was developed using Hittite HMC497LP4 radio frequency wideband modulators, Hittite HMC597LP4 wideband demodulators, monopole transmit and receive antennas, an Altera® Stratix® II field programmable gate array (FPGA) development board and the computer software. The indoor LOS measurements were carried out in 1.24 GHz to 1.30 GHz amateur radio frequency band. It is observed from the measurement results that an office environment with particular dimensions has an average user bandwidth and ADC dynamic range requirements which are required for satisfactory performance of system for the majority of the portable user locations. System performance along with bandwidth utilization and ADC dynamic range utilization is improved by allocating user baseband bandwidth and ADC dynamic range in accordance with the 90-50 MMB.