Pilot-Assisted Short-Packet Transmission over Multiantenna Fading Channels: A 5G Case Study

TL;DR

This paper analyzes short-packet transmission over multiantenna fading channels in 5G, proposing bounds and optimal pilot strategies to meet strict latency and reliability requirements.

Contribution

It introduces an achievability bound for short-packet 5G control channels using pilot-assisted MIMO transmission, optimizing pilot overhead for reliability.

Findings

Multiple antennas enhance reliability in short-packet 5G transmissions.

Optimal pilot symbols balance channel estimation accuracy and rate loss.

Spatial diversity is crucial for meeting stringent reliability constraints.

Abstract

Leveraging recent results in finite-blocklength information theory, we investigate the problem of designing a control channel in a 5G system. The setup involves the transmission, under stringent latency and reliability constraints, of a short data packet containing a small information payload, over a propagation channel that offers limited frequency diversity and no time diversity. We present an achievability bound, built upon the random-coding union bound with parameter $s$ (Martinez & Guill\'en i F\`abregas, 2011), which relies on quadrature phase-shift keying modulation, pilot-assisted transmission to estimate the fading channel, and scaled nearest-neighbor decoding at the receiver. Using our achievability bound, we determine how many pilot symbols should be transmitted to optimally trade between channel-estimation errors and rate loss due to pilot overhead. Our analysis also reveals the importance of using multiple antennas at the transmitter and/or the receiver to provide the spatial diversity needed to meet the stringent reliability constraint.