Superimposed Signaling Inspired Channel Estimation in Full-Duplex Systems

TL;DR

This paper introduces a novel superimposed signaling-based channel estimation method for full-duplex systems, improving accuracy and robustness in residual self-interference cancellation through asymmetric shifted constellations and EM estimation.

Contribution

It proposes a new superimposed signaling technique with asymmetric shifted constellations and derives an EM estimator and MSE bounds for efficient channel estimation in full-duplex systems.

Findings

Outperforms data-aided methods in MSE and bit error rate.

Requires minimal additional energy for accurate estimation.

Robust against increasing self-interference power.

Abstract

Residual self-interference (SI) cancellation in the digital baseband is an important problem in full-duplex (FD) communication systems. In this paper, we propose a new technique for estimating the SI and communication channels in a FD communication system, which is inspired from superimposed signalling. In our proposed technique, we add a constant real number to each constellation point of a conventional modulation constellation to yield asymmetric shifted modulation constellations with respect to the origin. We show mathematically that such constellations can be used for bandwidth efficient channel estimation without ambiguity. We propose an expectation maximization (EM) estimator for use with the asymmetric shifted modulation constellations. We derive a closed-form lower bound for the mean square error (MSE) of the channel estimation error, which allows us to find the minimum shift energy needed for accurate channel estimation in a given FD communication system. The simulation results show that the proposed technique outperforms the data-aided channel estimation method, under the condition that the pilots use the same extra energy as the shift, both in terms of MSE of channel estimation error and bit error rate. The proposed technique is also robust to an increasing power of the SI signal.