On Hybrid Pilot for Channel Estimation in Massive MIMO Uplink

TL;DR

This paper proposes a hybrid pilot scheme combining time-multiplexed and time-superimposed pilots to improve channel estimation in massive MIMO uplink, reducing pilot contamination and enhancing achievable rates.

Contribution

It introduces a novel hybrid pilot design that leverages the advantages of TM and TS pilots, with a closed-form rate approximation and asymptotic optimality analysis.

Findings

Hybrid pilot outperforms individual TM or TS pilots in simulations.

Asymptotic analysis shows optimal hybrid pilot design in large-antenna regimes.

Numerical results confirm the effectiveness of the proposed scheme.

Abstract

This paper introduces a hybrid pilot-aided channel estimation technique for mitigating the effect of pilot contamination for the uplink of multi-cell multiuser massive MIMO systems. The proposed hybrid pilot is designed such that it enjoys the complementary advantages between time-multiplexed (TM) pilot and time-superimposed (TS) pilot, and thereby, allows superior solution to the conventional pilot schemes. We mathematically characterize the impact of hybrid pilot on the massive MIMO uplink by deriving a closed-form approximation for the uplink achievable rate. In large-number-of-antennas regime, we obtain the asymptotically optimal solution for hybrid pilot by jointly designing the TM pilot and the TS pilot. It is shown that either TM pilot or TS pilot has the advantages for large frame-size and limited frame-size transmission, respectively, while the hybrid pilot scheme can offer a superior performance to that employing either TM pilot or TS pilot. Numerical results demonstrate the effectiveness of the proposed design.