Optimum Equivalent Loading in Multi-Dimensional Transmission

Abstract

Loading methods for wireline and wireless transmission systems are explained and reviewed to allow examination of fundamental equivalences between approaches to optimum transmission with linear cross-dimensional interference. Shannon’s famous water-filling method is then re-interpreted by examining the difference between mutual information and the constellation size used on each tone. Results reinforce that highest performance in all methods retains use of Shannon’s water-filling. However, results also find that a constant-size constellation on all energized water-filling dimensions, when used with a good code and an appropriate joint maximum-likelihood decoder, is sufficient to approximate this highest performance. This means that tone-dependent constellation variation is not necessary, which increases receiver complexity but reduces the need for channel-state feedback. This then leads to some adaptive MCS (modulation and coding scheme) equivalent loading methods that can be applied generally to wireline and wireless transmission.

Keywords

• Adaptive modulation
• coded modulation
• discrete multitone (DMT)
• modulation and coding scheme (MCS)
• orthogonal frequency-division multiplexing (OFDM)