MIMO exploitation of 3D multipath statistics in a heterogenous LTE-advanced network

• Main Author: Mansor, Zuhanis
• Published: University of Bristol 2013
• Subjects: 621.382
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616887

The ever increasing demand for wireless mobile communication has led the Third Generation Partnership Project (3GPP) Long Term Evolution Advanced (LTE-Advanced) standard to exploit the latest advances in physical layer technologies; including Single Carrier- Frequency Division Multiple Access (SC-FDMA), Orthogonal Frequency Multiple Access (OFDMA) and Multiple-Input Multiple-Output (MIMO). This research is focused on the need to radically enhance the capacity and spectral efficiency of cellular networks via a combination of heterogeneous networks (HetNets) and MIMO antenna array optimisation. The peak-to-average-power ratio (PAPR) of SC-FDMA with time-domain pulse shaping and frequency-domain spectral shaping is investigated. This PAPR reduction can be used to enhance the power efficiency of the handset, or alternatively to improve the uplink throughput and/or operating range. Results have shown that a PAPR reduction of 1.5 dB can be achieved compared to the unfiltered version via Frequency Domain Spectral Shaping (FDSS). The impact of 3D multi path in an LTE-Advanced HetNet is further explored as the current 3GPPIITU channel model assumes 2D multipath statistics. Spatial and temporal multipath statistics are generated for example macro- and pico-cellular base stations and these are combined with appropriately oriented complex polarmetric antenna patterns. The resulting wideband channels are then passed to an LTE-Advanced physical layer (PHY) simulator. A powerful MATLAB simulator has been developed to mathematically model the LTE-Advanced uplink (UL) and downlink (DL) performance. The simulator is able to predict the received power, data throughput, bit error rate and packet error rate for each user in the network. The optimal spatial multiplexing mode is determined by computing the throughput for all modulation and coding schemes. This is achieved by calculating the received bit mutual information rate given knowledge of the radio channel. The fastest link speed for each user is identified with a packet error rate threshold of 10% or better. The handset is also rotated in the azimuth and elevation planes to evaluate performance sensitivity. The impact of base station array orientation is considered in both the azimuth and elevation planes. Results show that antenna orientation at the base station strongly influences user performance in an LTE-Advanced network. The deployment of macro-cellular vertical arrays is shown to significantly degrade network performance. In contrast, the elevation angle spread is found to be far greater, in pico-cells and this allows vertical arrays to be applied to produce compact high performance pico base stations. Results show that the pico-cells offer significantly higher data rates compared to the macro-cells. The results also show that for higher order modulation, macro-cells offer the lowest usage percentage (43%) compared to pico-cells (53-56%).