Real-time algorithms and architectures for multiuser channel estimation and detection in wireless base-station receivers

Abstract

Abstract-This paper presents algorithms and architecture designs that can meet real-time requirements of multiuser channel estimation and detection in future code-division multiple-access-based wireless base-station receivers. Sophisticated algorithms proposed to implement multiuser channel estimation and detection make their real-time implementation difficult on current digital signal processor-based receivers. A maximum-likelihood based multiuser channel estimation scheme requiring matrix inversions is redesigned from an implementation perspective for a reduced complexity, iterative scheme with a simple fixed-point very large scale integration (VLSI) architecture. A reduced-complexity, bit-streaming multiuser detection algorithm that avoids the need for multishot detection is also developed for a simple, pipelined VLSI architecture. Thus, we develop real-time solutions for multiuser channel estimation and detection for third-generation wireless systems by: 1) designing the algorithms from a fixed-point implementation perspective, without significant loss in error rate performance; 2) task partitioning; and 3) designing bit-streaming fixed-point VLSI architectures that explore pipelining, parallelism, and bit-level computations to achieve real-time with minimum area overhead.

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“…For AWGN, the ML approach of our scheme and the MMSE approach of RLS lead to the same solution and hence, have similar BER performance [16]. However, our scheme is more suited towards a real-time implementation than RLS.…”

“…The comparisons of our scheme with recursive least squares (RLS) has been shown in [16]. For AWGN, the ML approach of our scheme and the MMSE approach of RLS lead to the same solution and hence, have similar BER performance [16].…”

“…Floating point detection was used to ensure that the loss in performance was due to the effects of channel estimation alone. The effects of fixed-point detection is studied in [16].…”

Adaptive Duplicated Filters and Interference Canceller for DS-CDMA Systems

“…Unfortunately, this optimal MUD is prohibitively complex for real-time implementation; its complexity increases exponentially with the number of users. Therefore, over the last two decades, research in this area has focused on several uplink sub-optimal MUD solutions [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] whose design objective is to reach a good tradeoff between performance and complexity: (1) to combat MAI and ISI in order to reliably detect information data of possibly a larger number of active users; while (2) maintaining a complexity permitting a real-time implementation for this maximum number of users. This implementation complexity issue explains the reason why the Rake receiver is still present in 3G base stations [4].…”

“…Indeed, even though many sub-optimal MUD methods have been proposed, most of these techniques show high computational complexity and can not be feasible in real-time on commercial baseband processors used in the BS. Nevertheless, some work has been conducted regarding real-time implementation aspect of MUDs [16,24].…”