On Analysis of Superimposed Pilot in Multi-User Massive MIMO with Massive Connectivity

TL;DR

This paper analyzes the superimposed pilot scheme in multi-user massive MIMO systems with massive connectivity, deriving scaling laws and optimal power allocation to improve performance over traditional methods.

Contribution

It provides a comprehensive analysis of superimposed pilots in massive MIMO, including explicit scaling laws and optimal power allocation strategies, which are novel contributions.

Findings

Superimposed pilot scheme outperforms traditional schemes in massive connectivity scenarios.

Derived explicit scaling law of mutual information lower bound with respect to user number.

Optimal power allocation between pilots and data enhances system performance.

Abstract

The simultaneous transmission of numerous users presents substantial challenges due to the inherent trade-off between channel estimation and information transmission in multi-user multiple-input multiple-output (MIMO) system. In this paper, we explore the use of the superimposed pilot (SP) scheme to tackle the large transmitting users, where the number of users may exceed the coherent time. SP scheme incorporates both transmitted data and noise in the channel estimation process, which is significant different from the counterpart of RP scheme. We provide an in-depth analysis of the interaction between interference caused by channel estimation errors and noise. We then derive the explicit expression for the scaling law of the mutual information lower bound (MILB) in relation to the number of users and the levels of transmitted power. Besides, the optimal power allocation between pilots and data transmission is also derived analytically. The analytical results demonstrate that the SP scheme significantly improves performance compared to traditional RP scheme in our consider case. Numerical results are also presented to validate our theoretical derivations.