On The Efficiency of Widely Linear Precoding and Symbol Extension in Cellular Uplink

TL;DR

This paper explores the use of improper Gaussian signaling with symbol extension in cellular uplink to improve data rates and power efficiency, especially under strong interference, compared to traditional proper Gaussian signaling.

Contribution

It demonstrates the benefits of widely linear precoding and symbol extension in reducing power consumption and increasing rates in interference-limited cellular uplink scenarios.

Findings

Improper Gaussian signaling outperforms proper signaling at low rate demands under strong interference.

Symbol extension combined with improper signaling significantly reduces power consumption.

The proposed scheme achieves higher information rates with manageable complexity.

Abstract

We investigate Gaussian widely linear precoding known as improper Gaussian signaling for the cellular uplink with inter-cell interference, known as interference multiple access channel (IMAC). This transmission scheme provides extra degrees of freedom by treating the real and imaginary components of the complex Gaussian signal differently. Since current standards mainly utilize linear beamforming for waveform generation, we highlight the benefits of widely linear beamforming over multiple temporal dimensions (symbol extension in time) in the IMAC. This scheme achieves significantly higher information rates compared to conventional proper Gaussian signaling at the expense of extra complexity at the transmission phase. We study the sum-power minimization problem under rate constraints. This problem is a difference of concave functions (DC) program, hence, a non-convex problem. By numerical simulations, we observe the benefits of improper Gaussian signaling alongside symbol extension in power consumption for both single-antenna and multi-antenna base stations. Interestingly, we observe that at strong interference scenarios, the efficiency of improper Gaussian signaling outperforms conventional proper Gaussian signaling at low rate demands. Moreover, in such scenarios the sum-power required for achieving particular rate demands is significantly reduced.