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Downlink Channel Decorrelation in CDMA Systems with Long Codes
- in Proc. IEEE Veh. Technol. Conf
, 1999
"... In this paper we develop linear detectors suitable for a Code Division Multiple Access (CDMA) mobile receiver using long codes. The special signal structure in the downlink transmission is exploited to obtain a simple detection rule. A least-squares (LS) detector, a best linear unbiased estimator (B ..."
Abstract
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Cited by 17 (3 self)
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In this paper we develop linear detectors suitable for a Code Division Multiple Access (CDMA) mobile receiver using long codes. The special signal structure in the downlink transmission is exploited to obtain a simple detection rule. A least-squares (LS) detector, a best linear unbiased estimator (BLUE) detector, and a linear minimum mean-square error (LMMSE) detector are derived. For the LMMSE detector we consider an adaptive implementation. The results show that improvement can be achieved using the proposed detectors compared with that of the conventional RAKE receiver. I. INTRODUCTION In CDMA reception at the mobile end there are several special requirements. The resources for processing are severely constrained by the physical size of the receiver and the strict limitations for power consumption. Furthermore, the other users' codes are not necessarily known at the mobile receiver and the estimation of other users' channel parameters especially may involve too complex processing ...
Constrained quasi-Newton algorithm for CDMA mobile communications
- International Telecommunications Symposium
, 1998
"... ..."
Comparison of Conventional and Adaptive Receiver Concepts for the UTRA Downlink
- in Proc. UMTS Workshop
, 1998
"... A new receiver concept with interference cancellation for the UTRA downlink is presented and compared in terms of the bit-error rate (BER) with single-antenna and multiple-antenna conventional receivers. Since the proposed scheme is equipped with the knowledge of the conventional receiver, i.e. the ..."
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Cited by 2 (1 self)
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A new receiver concept with interference cancellation for the UTRA downlink is presented and compared in terms of the bit-error rate (BER) with single-antenna and multiple-antenna conventional receivers. Since the proposed scheme is equipped with the knowledge of the conventional receiver, i.e. the code of the signal of interest and the number of relevant transmission paths arising from multipath propagation, it can be viewed as being adaptive to the multiple access interference in a blind fashion. Aperiodic scrambling sequences are readily taken into account since the scheme does not rely on the cyclostationarity of the interfering signals. Simulations reveal that the performance gain as compared to the single-antenna conventional receiver depends critically on the quality of the channel parameter estimates. Several other effects, like a small number of users or a high amount of intercell interference, reduce the gain. In view of the simulation results in different scenarios, the prop...
Pipelined Adaptive CDMA Mobile Receivers
, 1998
"... Adaptive multiple-antenna receivers can provide insensitivity to the interfering powers and room for more users or they require smaller number of antennas compared to the matched filter solution. In this paper, pipelined implementation of an adaptive DirectSequence Code Division Multiple Access rece ..."
Abstract
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Cited by 1 (1 self)
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Adaptive multiple-antenna receivers can provide insensitivity to the interfering powers and room for more users or they require smaller number of antennas compared to the matched filter solution. In this paper, pipelined implementation of an adaptive DirectSequence Code Division Multiple Access receiver is proposed when multiple antennas are utilized for mobile communications. A number of approximation techniques are utilized to pipeline the Recursive Least-Squares (RLS) algorithm used for the receiver. The resulting pipelined structure achieves a higher throughput or requires lower power as compared to the receiver using the conventional serial RLS algorithm. As a result of pipelining, the hardware overhead is only 2M extra latches. For different number of antennas and different levels of pipelining the signal-to-interference versus the relative interfering power are illustrated.
MULTIPLE-ANTENNA CDMA MOBILE RECEPTION USING CONSTRAINED NORMALIZED ADAPTIVE ALGORITHMS
"... Abstract- In this paper we analyze adaptive algorithms for a multiple-antenna Code Division Multiple Access (CDMA) mobile receiver. We study the constrained versions of the Binormalized Data-Reusing LMS (BNDR-LMS) and the Normalized LMS (NLMS). Their performance is compared with that of the classica ..."
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Abstract- In this paper we analyze adaptive algorithms for a multiple-antenna Code Division Multiple Access (CDMA) mobile receiver. We study the constrained versions of the Binormalized Data-Reusing LMS (BNDR-LMS) and the Normalized LMS (NLMS). Their performance is compared with that of the classical Frost algorithm. Time-varying stepsequences are used to further enhance the performance of the receiver. The results show that considerable improvement in the convergence speed can be achieved with the use of the normalized algorithms compared with the conventional Frost algorithm. Using an optimal step-sequence in the update provides a fast convergence and a nearoptimum steady-state performance. I.
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"... Adaptive multiple-antenna receivers can provide insensitivity to the interfering powers and room for more users or they require smaller number of antennas compared to the matched filter solution. In this paper, pipelined implementation of an adaptive Direct-Sequence Code Division Multiple Access rec ..."
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Adaptive multiple-antenna receivers can provide insensitivity to the interfering powers and room for more users or they require smaller number of antennas compared to the matched filter solution. In this paper, pipelined implementation of an adaptive Direct-Sequence Code Division Multiple Access receiver is proposed when multiple antennas are utilized for mobile communications. A number of approximation techniques are utilized to pipeline the Recursive Least-Squares (RLS) algorithm used for the receiver. The resulting pipelined structure achieves a higher throughput or requires lower power as compared to the receiver using the conventional serial RLS algorithm. As a result of pipelining, the hardware overhead is only 2M extra latches. For different number of antennas and different levels of pipelining the signal-to-interference versus the relative interfering power are illustrated. 1.
Relaxed Look-Ahead Technique For
- in Proc. IX European Signal Processing Conference, Island of Rhodes
, 1998
"... In this paper, Relaxed Look-Ahead technique for pipelined implementation of an adaptive Direct-Sequence Code Division Multiple Access receiver is proposed when multiple antennas are utilized for mobile communications. Adaptive multiple-antenna receivers can provide insensitivity to the interfering p ..."
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In this paper, Relaxed Look-Ahead technique for pipelined implementation of an adaptive Direct-Sequence Code Division Multiple Access receiver is proposed when multiple antennas are utilized for mobile communications. Adaptive multiple-antenna receivers can provide insensitivity to the interfering powers. They also provide room for more users or require smaller number of antennas than the matched filter solution. A number of approximation techniques are utilized to pipeline the adaptive algorithm used for the proposed multiple-antenna receiver. The resulting pipelined receiver achieves a higher throughput or requires lower power as compared to the receiver using the serial algorithm. With the aid of simulations, for different levels of pipelining and different number of antennas, the signal-tointerference ratio and the bit error rate versus the relative interfering power are illustrated.
Wideband CDMA By
, 2002
"... We consider a downlink DS-CDMA system in which multirate user signals are transmitted via synchronous orthogonal short codes overlaid with a common scram-bling sequence. The transmitted signal is subjected to significant time- and frequency-selective multipath fading, e.g., a channel with delay spre ..."
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We consider a downlink DS-CDMA system in which multirate user signals are transmitted via synchronous orthogonal short codes overlaid with a common scram-bling sequence. The transmitted signal is subjected to significant time- and frequency-selective multipath fading, e.g., a channel with delay spread potentially longer than the bit interval of high-rate users. In response to this scenario, a novel two-step receiver is proposed that com-bines chip-rate adaptive equalization with error filtering. In the first step, a code-multiplexed pilot is used to adapt the equalizer. Single-pole averaging of the chip-rate error signal used in adaptation reduces MAI and implies third-order LMS, which has advantages over standard LMS in tracking the time-varying channel. In the second step, decision-direction is used to improve the error signal, resulting in improved tracking performance. The performance of the adaptive receiver is studied through analysis and simulation. ii
