Performance of LTE linear MIMO detectors: Achievable data rates and complexity

In this study we analyze performance of linear single user multiple-input multiple-output (SU-MIMO) detector applied in 3GPP LTE wireless systems. We consider minimum mean square error (MMSE) linear detectors based on (i) explicit matrix inversion, and (ii) adaptive gradient algorithm. We present the average achievable data rates as a function of different mobile terminal speeds, using the Jakes model, with symbol-by-symbol temporal variations. Mean and cell-edge rates are determined using two-dimensional multi-cell model. The LTE-specific reference signal (i.e., pilot) arrangements are considered. In addition, the implementation complexity is analyzed. At the expense of higher implementation complexity, for higher mobile terminal speeds and signal-to-interference-and-noise ratio (SLNR) the detector based on explicit matrix inversion outperforms the one based on the adaptive gradient algorithm. Furthermore, we show that a corresponding single-input multiple-output (SIMO) solution outperforms MIMO for moderate and high mobile terminal speeds. In addition, complexity-wise the SIMO transmission is shown to be more efficient. The results indicate that the MIMO transmission with linear detection should be applied only in a very limited number of channel conditions: (i) high SINR, and (ii) low mobility. This study may be used as a basis for establishing a trade-off between the data rates, complexity and multiple antenna arrangements.