PERFORMANCE EVALUATION OF LTE DOWNLINK WITH MIMO TECHNIQUES

Abstract: Long Term Evolution (LTE) of the Universal Mobile Telecommunication System (UMTS) also known as the Evolved Packet System (EPS) is a transilient move in the field of mobile communications. Such a revolution is necessitated by the unceasing increase in demand for high speed connections on networks, low latency and delay, low error rates and resilience because modern users and network applications have become increasingly dependent on these requirements for efficient functionality and performance. Third Generation Partnership Project Long Term Evolution (3GPP LTE) promises high peak data rates for both uplink and downlink transmission, spectral efficiency, low delay and latency, low bit error rates, to mention but a few. These functional and performance targets of 3GPP LTE are laudable and can be met with a great measure of certainty, but then a vital question emerges: What are the prime drivers or enablers for these technology standard requirements to be met? LTE leverages on a number of technologies namely Multi Input Multiple Output (MIMO) antennas, Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Frequency Division Multiplexing Access (OFDMA) at the downlink, Single Carrier Frequency Division Multiple Access (SCFDMA) at the uplink, support for Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), and 64QAM. This thesis work evaluates the performance of LTE downlink with MIMO techniques. MIMO technology involves the use of multiple antennas at the transmitter, receiver or both. There are different combinations of array configuration and polarization, transmission and detection schemes that can be implemented to achieve different purposes in functional and performance terms. In terms of array configuration and polarization, there exists single polarized array and cross polarized array (which could be compact or detached); transmission schemes include diversity schemes particularly transmit diversity and spatial multiplexing; detection schemes such as Zero Forcing (ZF) and Soft Sphere Decoding (SSD). The performance metrics considered are throughput and BER and these are used to evaluate the performance of LTE in flat-fading and International Telecommunications Union B (ITU-B) Pedestrian channel with zero forcing and soft sphere decoding for Single Input Single Output (SISO), transmit diversity and spatial multiplexing. The granular analysis and evaluation of the performance 3GPP LTE is imperative and this thesis implements this on the downlink side. A thorough analysis and performance evaluation of the LTE downlink with MIMO antennas is thus the focal point and the results demonstrate that the design goals and requirements of 3GPP LTE can be met with a great deal of reliability and certainty. The simulations show that the performance of MIMO is better than SISO in both channel models particularly when SSD is employed. When high order modulation is utilized, performance in the flat-fading channel model is better than ITU pedestrian B channel at low SNR regions. Spatial multiplexing is ideal for achieving very high peak rates, while transmit diversity is a valuable scheme to minimize the rate of bit error occurrence thereby improving signal quality.