Chip-Level Channel Equalization in WCDMA Downlink

Abstract

The most important third generation (3G) cellular communications standard is based on wideband CDMA (WCDMA). Receivers based on TDMA style channel equalization at the chip level have been proposed for a WCDMA downlink employing long spreading sequences to ensure adequate performance even with a high number of active users. These receivers equalize the channel prior to despreading, thus restoring the orthogonality of users and resulting in multiple-access interference (MAI) suppression. In this paper, an overview of chip-level channel equalizers is delivered with special attention to adaptation methods suitable for the WCDMA downlink. Numerical examples on the equalizers′ performance are given in Rayleigh fading frequency-selective channels

Throughput Analysis of DS-CDMA Wireless Packet Access using Frequency-Domain Equalization and Random TPC

“…If the IPI is partially suppressed by an interference canceller [4] or an equalizer [5], the throughput increases. We have shown that a combined use of IPI canceller and random TPC provides a significant improvement in the throughput of DS-CDMA slotted ALOHA [6]. Recently, frequency-domain equalization (FDE) [7], [8] has been attracting much attention to improve the single-carrier transmission performance in a frequencyselective channel.…”

Hermitian optimization and scalable VLSI architecture for circulant approximated MIMO equalizer in CDMA downlink

“…We also only need to compute d21 and d22 to get the G elements. The redundant computations in {tmp 4 , tmp 8 …”

“…With a very short spreading gain, the conventional Rake receiver could not provide acceptable performance. Linear-MinimumMean-Square-Error (LMMSE) chip equalizer is promising to restore the orthogonality of the spreading code, so as to suppress both the ISI and MAI [4]. However, it requires to inverse a large correlation matrix with O((N F )…”

Efficient MIMO equalization for downlink multi-code CDMA: complexity optimization and comparative study

“…With a very short spreading gain, the conventional Rake receiver could not provide acceptable performance. The LMMSE (LinearMinimum-Mean-Square-Error)-based chip equalizer is promising to restore the orthogonality of the spreading code, so as to suppress both the ISI and MAI [5].…”

“…The fact that the receiver must be embedded into a portable device makes the design of low complexity mobile receivers very critical for widespread commercial deployment of low cost products. To avoid the Direct-Matrix-Inverse (DMI), adaptive stochastic gradient algorithms such as LMS could be applied [5]. However, they suffer from stability problems because the convergence depends on the choice of good step size.…”