Real-time DSP and FPGA Implementation of Wiener LMS Based Multipath Channel Estimation in 3G CDMA Systems

Abstract

This paper investigates real-time DSP and FPGA implementations of a low complexity technique for asynchronous multiuser delay acquisition and time varying channel tracking for multipath channels in WCDMA and cdma2000 systems. A multiuser-LMS-like structure along with smoothing/prediction filters to improve tracking quality is reviewed. We investigate an efficient implementation based on FFT/IFFT technique, under fixed-point data representation and computation constraint. The measured BER reveals that fixed-point implementation is feasible at possibly no performance degradation. Based on real time execution made on a fixed-point high performance DSP, the maximum number of users is 15 and 17 for the proposed method and correlator, respectively. Due to the inherent parallelism and regular data flow FPGA implementation is suggested wherein a maximum number of users more than 80 can be afforded in Xilinx Virtexi II Pro device.

Adaptive Duplicated Filters and Interference Canceller for DS-CDMA Systems

“…Unlike in (5), k ,ĥ k;p n ½ and the delays b t k;p , for k=1,2,...,K and p=1,...,P k , are provided by a channel estimator, possibly a Correlator [27] or more performed method [26]. Accordingly, the total contribution from all the K users is given by the summation of all the users' contributions, such that:…”

“…The channel estimation is not the object of this paper; a Correlator can be used instead but other methods can be used to boost the MUD performance (e.g. [26]); & During ADIC's adaptation phase, (13)- (18) , N s being the last stage.…”

“…This approach consists of creating synthesized training signals based on the known channel parameters given in turn by the channel estimator (e.g. Correlator [26,27]). These synthesized training signals can be generated at the receiver to adapt the filter coefficients following indirect adaptation method.…”

On MSE Exit Chart Analysis and Real Time DSP Implementation for Iterative (Turbo) Detection

“…ð ÞI 2N Â2N Þ, and A, an 2N × 3K matrix, combines the spreading codes and the multipath channel [10]. Without loss of generalities, the signal model assumes that a user signal at the receiver undergoes a multipath fading channel wherein the maximum multipath delay (for all users as well) is less than the symbol rate [10] and [7].…”

VLSI Implementation of an Adaptive Multiuser Detector for Multirate WCDMA Systems

“…Nevertheless, the channel parameters can be estimated by a channel estimation technique, e.g. a Correlator [7] or a better channel estimation method [25]. The received baseband signalr and the internal baseband signal r train are common for all users.…”