Approaching Capacity Without Pilots via Nonlinear Processing at the Edge

TL;DR

This paper introduces a maximum likelihood-based nonlinear detector for uplink wireless channels that operates without prior channel state information, eliminating the need for pilot signals and enabling efficient user data retrieval in high SNR conditions.

Contribution

It proposes a novel nonlinear detection method derived from information theory that works without pilot-assisted channel estimation in multi-user wireless systems.

Findings

Effective in retrieving channel coefficients and data without prior CSI.

Operates under high SNR and large coherence block assumptions.

No coordination needed with unintended users.

Abstract

A nonlinear detector derived within a maximum likelihood estimation framework is shown to be effective in retrieving the channel coefficients and data of users on the uplink channel of a noncooperative wireless system without the access point having any prior channel state information (no CSI or noncoherent setup). Rather than relying on pilot-assisted transmissions, it is shown that a maximum likelihood-based detector emerges naturally from an information-theoretic argument. The assumptions under which the detector is designed are as follows: 1) the uplink data from different users are independent and non-Gaussian; 2) the coherence block of the channel is much larger than the number of users (in practice, the square of the number of users); 3) the number of antennas at the access point or base station is equal to the number of users; 4) users continuously transmit within the coherence block; and 5) the transmission occurs at high signal-to-noise ratio. No coordination between the access point and unintended users (interference) is needed. Some coordination with intended users is needed. Finally, the system is assumed to be symbol-synchronous.