Block Equalization and Generalized MLSE Arbitration for the HSPA WCDMA Uplink

High speed packet access (HSPA), the latest evolution of the wideband code division multiple access (WCDMA) standard, provides higher uplink data rates using higher-order modulation (16-QAM) and multicode transmission. Equalization is needed when the channel is dispersive. Despite gains from linear equalization, there is room for further improvement. In this paper, we consider two enhancements: block equalization with joint detection and a generalization of arbitration. Block equalization with joint detection, originally developed for non-spread systems, involves jointly detecting symbols from multiple symbol periods and using a feedback filter to remove interference from past symbol periods. Here we extend this idea to parallel symbol streams, add feedforward filtering, and introduce the notion of block linear equalization. Arbitration, also originally developed for nonspread systems, involves bidirectional decision feedback equalization and selection. Here we generalize the arbitration concept to other forms of equalization and improve the selection process using constrained maximum-likelihood sequence estimation (MLSE). These enhancements are then evaluated via simulation for the HSPA uplink, demonstrating their efficacy.