Outage-Efficient Downlink Transmission Without Transmit Channel State Information

TL;DR

This paper explores outage-efficient downlink transmission strategies for fading Gaussian broadcast channels without transmit channel state information, proposing two coding schemes that outperform traditional methods.

Contribution

It introduces two novel coding schemes, B-DPC and S-SC, designed for scenarios where only fading distribution knowledge is available at the transmitter, improving outage achievable rates.

Findings

Both schemes outperform time-sharing in achievable rates.

S-SC can be extended to multiple transmit antennas.

Proposed schemes are robust to fading distribution variations.

Abstract

This paper investigates downlink transmission over a quasi-static fading Gaussian broadcast channel (BC), to model delay-sensitive applications over slowly time-varying fading channels. System performance is characterized by outage achievable rate regions. In contrast to most previous work, here the problem is studied under the key assumption that the transmitter only knows the probability distributions of the fading coefficients, but not their realizations. For scalar-input channels, two coding schemes are proposed. The first scheme is called blind dirty paper coding (B-DPC), which utilizes a robustness property of dirty paper coding to perform precoding at the transmitter. The second scheme is called statistical superposition coding (S-SC), in which each receiver adaptively performs successive decoding with the process statistically governed by the realized fading. Both B-DPC and S-SC schemes lead to the same outage achievable rate region, which always dominates that of time-sharing, irrespective of the particular fading distributions. The S-SC scheme can be extended to BCs with multiple transmit antennas.