Tradeoff between Diversity and Multiplexing Gains in Block Fading Optical Wireless Channels

TL;DR

This paper analyzes the fundamental tradeoff between diversity and multiplexing in block fading optical wireless channels, considering power constraints and different fading conditions, revealing significant differences from RF channel results.

Contribution

It characterizes the DMT in optical wireless channels under power constraints and various fading distributions, providing bounds and optimal tradeoffs for different block lengths.

Findings

Optimal DMT derived for large block lengths

Bounds of DMT curve established for small block lengths

Significant differences from RF channel DMT results

Abstract

The diversity-multiplexing tradeoff (DMT) provides a fundamental performance metric for different multiple-input multiple-output (MIMO) schemes in wireless communications. In this paper, we explore the block fading optical wireless communication (OWC) channels and characterize the DMT in the presence of both optical peak- and average-power constraints. Three different fading distributions are considered, which reflect different channel conditions. In each channel condition, we obtain the optimal DMT when the block length is sufficiently large, and we also derive the lower and upper bounds of the DMT curve when the block length is small. These results are dramatically different from the existing DMT results in radio-frequency (RF) channels. These differences may be due to the fact that the optical input signal is real and bounded, while its RF counterpart is usually complex and unbounded.