Resource Allocation and Design of Variable Length Per-Tone Equalizers in MIMO-OFDM Systems

For mitigating inter-symbol interference (ISI) and inter-carrier interference (ICI) caused by insufficient cyclic prefix (CP), per-tone equalizer (PTEQ) outperforms traditional time domain equalizer (TEQ) since each tone is equalized independently. However, PTEQ with equal number of taps (equal length) for all the tones can not achieve the optimal performance because channel conditions of different tones between different transmit and receive antennas are not the same. Variable-length PTEQ can make full use of each tap, however it is difficult to design for MIMO-OFDM because its design needs exhaustive search and results in extremely high complexity. In this paper, a novel algorithm of designing variable-length PTEQ is proposed. The design is realized in two steps--tap number allocation and tap coefficient calculation, so that the complexity is low. The tap number allocation and the optimal coefficient calculation are based on channel conditions, so that better system performance can be achieved than using equal-length PTEQ. Simulation is carried out and main parameters are investigated.