Full-rate integer space-time block codes for 2×2 MIMO channels

We propose two types of full-rate integer STBCs (ICs) for 2 × 2 Multiple-Input Multiple-Output (MIMO) fading channels. A unique property of ICs is the presence of integer coefficients in the code structure, which enables reduced numbers of processor bits for the encoder. Due to the presence of integer coefficients ICs can be encoded with as low as 3, 5, and 7 bits for 4, 16, and 64-QAM constellations, respectively. We show that ICs are fast Maximum Likelihood (ML) decodable with the worst-case complexity of O(2M^2.5) for square M-QAM constellation. We also show that ICs have low Peak-Average-Power-Ratio (PAPR) values. Through computer simulations, we show that ICs outperform the finite-precision versions of the Golden code and the Silver code. Importantly, one of the proposed types of ICs are within a constant gap of 2 dB from the infinite-precision versions of the Golden code and the Silver code for 4, 16, and 64-QAM constellations, at moderate to high SNR values.