Performance of LTE in Rural Areas - Benefits of Opportunistic Multi-User MIMO

This paper focuses on the performance of LTE in rural areas which is based on a channel measurement campaign conducted with the Eurecom OpenAirInterface LTE testbed at 800MHz. This testbed is based on LTE release 8 PHY layer and implements transmission modes 1 (single antenna - SISO), 2 (transmit diversity), and 6 (single-user MIMO - closed loop rank-1 precoding) in real time. In addition to the throughput recorded from the real modem, the raw channel estimates were stored and used for extrapolating the performance to transmission mode 5 (multi-user MIMO). This extrapolation is done by means of a mutual-information based link-quality model that abstracts the performance of multi-user (MU) MIMO for an interference aware receiver proposed by Ghaffar et al and then the results are compared with the performance of abstraction to transmission mode 2 and 6. The superior performance of MU MIMO mode (with interference aware receiver) over other transmission modes is illustrated and it is shown that if the channel admits then MU MIMO is the preferred option.