Algorithm and FPGA implementation of interpolation-based soft output mmse mimo detector for 3GPP LTE

The number of orthogonal frequency division multiplexing (OFDM) sub-carriers in modern wireless communication systems such as Third Generation Partnership Project (3GPP) long term evolution (LTE) can be as high as 2048. Channel matrix of data sub-carriers in conventional multiple-input-multiple-output (MIMO) receivers is derived by interpolating channel matrix of pilot sub-carriers and MIMO detection is performed on each interpolated channel matrix. Symbol detection on sub-carrier by sub-carrier basis demands a very high computational power. This study presents the first very-large scale integration implementation of a novel 4 × 4 interpolation-based soft output minimum-mean-squared error (MMSE) MIMO detector which combines channel estimation and MIMO detection. The detector computes MMSE matrix on pilot sub-carriers using proposed division-free matrix inversion algorithm and obtains MMSE matrix of data sub-carriers by interpolation, reducing computational complexity by more than 66%. The throughput of the implemented detector on Virtex-7 field programmable gate array (FPGA) exceeds 1 Gbps with 2.1 μs latency.