A new SISO algorithm with application to turbo equalization

TL;DR

This paper introduces a novel soft-input soft-output equalization algorithm that dynamically simplifies the trellis structure during processing, achieving a better performance/complexity balance for high-order modulation systems.

Contribution

It presents a new SISO equalization algorithm that merges states instead of deleting them, improving upon the reduced-state BCJR algorithm in performance and flexibility.

Findings

Outperforms the reduced-state BCJR algorithm in simulations.

Offers improved performance for systems with higher order modulations.

Provides a flexible approach balancing complexity and accuracy.

Abstract

In this paper we propose a new soft-input soft-output equalization algorithm, offering very good performance/complexity tradeoffs. It follows the structure of the BCJR algorithm, but dynamically constructs a simplified trellis during the forward recursion. In each trellis section, only the M states with the strongest forward metric are preserved, similar to the M-BCJR algorithm. Unlike the M-BCJR, however, the remaining states are not deleted, but rather merged into the surviving states. The new algorithm compares favorably with the reduced-state BCJR algorithm, offering better performance and more flexibility, particularly for systems with higher order modulations.