A New Class of TAST Codes With A Simplified Tree Structure

TL;DR

This paper introduces a novel class of TAST space-time codes with a simplified tree structure, achieved through a new SISO encoder design that results in an upper triangular code matrix, facilitating easier decoding.

Contribution

It presents a new construction method for TAST codes that simplifies the decoding process by producing an upper triangular code matrix, applicable to arbitrary antennas and input alphabets.

Findings

Simplified QR-decomposition due to upper triangular code matrix

Enhanced decoding efficiency with tree search algorithms

Applicable to various antenna configurations and input alphabets

Abstract

We consider in this paper the design of full diversity and high rate space-time codes with moderate decoding complexity for arbitrary number of transmit and receive antennas and arbitrary input alphabets. We focus our attention to codes from the threaded algebraic space-time (TAST) framework since the latter includes most known full diversity space-time codes. We propose a new construction of the component single-input single-output (SISO) encoders such that the equivalent code matrix has an upper triangular form. We accomplish this task by designing each SISO encoder to create an ISI-channel in each thread. This, in turn, greatly simplifies the QR-decomposition of the composite channel and code matrix, which is essential for optimal or near-optimal tree search algorithms, such as the sequential decoder.