Low complexity linear MMSE detector with recursive update algorithm for iterative detection-decoding MIMO OFDM system

Iterative turbo processing between detection and decoding shows near-capacity performance on a multiple-antenna system. Combining iterative processing with optimum front-end detection is particularly challenging because the front-end maximum a posteriori (MAP) algorithm has a computational complexity that is exponential in the throughput. Sub-optimum detector such as the soft interference cancellation linear minimum mean square error (SIC-LMMSE) detector with near front-end MAP performance has been proposed. The asymptotic computational complexity of SIC-LMMSE remains O(nE2
_t
n
_r
+ n
_t
nE3
_r
+ n
_t
M
_c
2
^M

_c
) per detection-decoding cycle where n
_t
is number of transmit antenna, n
_r
is number of receive antenna, and mc is modulation size. A lower complexity detector is the hard interference cancellation LMMSE (HIC-LMMSE) detector. HIC-LMMSE has asymptotic complexity of O(nE2
_t
n
_r
+ n
_t
M
_c
2
^M

_c
) but suffers extra performance degradation. In this paper, we introduce a low complexity front-end detection algorithm that not only achieves asymptotic computational complexity of O(nE2
_t
n
_r
+ n
_t
nE3
_r
[Gamma (beta)] + n
_t
M
_c
2
^M

_c
) where [Gamma (beta) is a function with discrete output {-1,2,3, ...,n
_t
}. Simulation results demonstrate that the proposed low complexity detection algorithm offers exactly same performance as its full complexity counterpart in an iterative receiver while being computational more efficient