Decision directed channel tracking for MIMO-constant envelope modulation

The authors have proposed Multi-Input Multi-Output (MIMO)-Constant Envelope Modulation, MIMO-CEM, as power and complexity efficient alternative to MIMO-OFDM, suitable for wireless backhaul networks. Because MIMO-CEM receiver employs 1-bit ADC, MIMO-CEM channel estimation is one of the major challenges toward its real application. The authors have proposed adaptive channel estimator in static and quasi-static channel conditions. Although wireless backhaul channel conditions are theoretically considered as static and quasi-static, it suffers from some channel fluctuations in real applications. Hence, the objective of this paper is to present a decision directed channel estimation (DDCE) to track channel fluctuation in high Doppler frequency condition, and clarify the effectiveness of our method under dynamic channel. For the purpose of comparison, the performance of DDCE is compared with that of a pilot assisted linear interpolation channel tracking for MIMO-CEM. Different Doppler frequencies are assumed to prove the effectiveness of the scheme even in high channel variations.