Adaptive multiuser MMSE down-link receiver techniques for UTRA TDD

First International Symposium on Control, Communications and Signal Processing, 2004.

2004

Self Cite

In this paper, we propose a blind multiuser detection scheme in a direct sequence CDMA downlink scenario by means of a chiplevel equaliser, which can be updated even if not all possible users are active, i.e. the system is partially loaded. The active synchronous users are separated by re-establishing orthogonality of their spreading sequences in a common chip-level equaliser. The adaptation algorithm is mainly based on a constant modulus (CM) criterion applied to the active users. The inactive codes in the system must be considered, for which we proposed and compare three different methods: (i) a mean square error criterion for absent users, and a CM approach with (ii) zero modulus or (iii) the transmission of arbitrary signals with small code amplitude. For all three cases, stochastic gradient descent algorithms are derived. The proposed algorithms are analysed and compared through various simulations, which demonstrate the algorithms' convergence and BER performance.

Section: Signal Modelmentioning

confidence: 99%

“…This permits to assemble stochastic gradient descent algorithms according to (6) for the various cost functions derived in Sec. 3.…”

Section: Stochastic Gradient Based Blind Adaptationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A blind synchronous multi-user DS-CDMA equaliser with partial loading

First International Symposium on Control, Communications and Signal Processing, 2004.

2004

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“…For the DS-CDMA downlink, the recovery of several synchronous users at the same time exploits more knowledge of the system. Non-blind multiuser schemes, such as the least mean square (LMS) algorithm, in turn are based either on the knowledge of a pilot [13,7] or training sequences [15]. Blind schemes have been derived using a constant modulus (CM) criterion [4,5], and the derived algorithms either neglect the dispersiveness of the channel [5] or spreading [4,2], whereby the later additionally require mutual decorrelation of the recovered user sequences.…”

Section: Introductionmentioning

confidence: 99%

A Pilot-Assisted Equalisation Scheme for the Umts-TDD Downlink With Partial Loading

2005 IEEE 61st Vehicular Technology Conference

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This version is available at https://strathprints.strath.ac.uk/38047/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. A PILOT-ASSISTED EQUALISATION SCHEME FOR THE UMTS-TDD DOWNLINK WITH PARTIAL LOADING Mahmoud Hadef and Stephan WeissSchool of Electronics & Computer Science University of Southampton, Southampton SO17 1BJ, UK {m.hadef,s.weiss}@ecs.soton.ac.uk Abstract. In this paper, we address a pilot-assisted channel equalisation strategy for the partially loaded downlink time-division duplex (TDD) component of the universal mobile telecommunication system (UMTS). The adaptation is performed by minimising a hybrid cost function based on the constant modulus (CM) criterion for all active users and a mean square error (MSE) criterion for both absent users and pilot signals. Computer simulations are used to assess the performance of the equalisation strategy under various partially loaded conditions.

Blind chip-rate equalisation for DS-CDMA downlink receiver

The Thrity-Seventh Asilomar Conference on Signals, Systems &Amp; Computers, 2003

Konrad

et al.

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A dispersive channel in the DS-CDMA downlink destroys the orthogonality of the synchronous users' spreading sequences. In this paper, we aim to re-establish this orthogonality blindly by means of a common chip-level equaliser. The adaptation algorithm is based on a constant modulus criterion forcing the various user symbols onto a constant modulus, for which a stochastic gradient descent algorithm is derived. This algorithm is structurally similar to a multiple error filtered-X LMS type approach, whereby the equaliser input CM update is replaced by a spreading code filtered version. Various simulations demonstrating the algorithm's convergence and noise performance are presented.