Ergodic UL/DL capacity analysis of co-located and distributed antenna configuration for high speed train with massive MIMO system

This paper analyse the performance and design of high speed Train (HST) communications that use massive multiple-input multiple-output (MIMO) system. The users travelling in the train communicate with the Base Station by using antennas mounted on top of the train as gateways. Two antenna configuration are considered, one is co-located antennas (CA) at the center of the train, and the other is distributed antennas (DA) uniformly placed along the train. In the CA layout, the average ergodic uplink capacity is concave in the number of Tx antennas on the train, and the optimum antennas on the train is found by increasing the average uplink capacity. In the DA layout, the average ergodic capacity is bounded concave function, which are then used to find optimum value of the number of Tx antennas on the train. Both analytical and simulation results demonstrate that the CA layout has a higher average cell capacity while the DA layout has comparatively low capacity. In this paper downlink maximum achievable rate or capacity is also simulated and analysed with respect to number of base station antenna which shows that as we increase number of base station antenna, achievable rate from base station to user terminal is also increased.