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- Mahesh K. Varanasi, Clifford T. Mullis, Ateet Kapur
- IEEE Transactions on Information Theory
- 2006

This correspondence highlights the performance limitation of linear minimum mean-squared error (mmse) detection in underdetermined vector Gaussian channels (as in overloaded code-division multiple-access (CDMA) systems) where the number of symbols (users) exceeds the signal space dimension (spread factor). It is shown that for such a simple receiver it is… (More)

- Ateet Kapur, Mahesh K. Varanasi, Deepak Das
- IEEE Trans. Communications
- 2002

—Three noncoherent minimum mean-squared error (MMSE)-based multiuser receivers are proposed for multipulse modulation. These receivers have a common MMSE prefilter and are followed by one of three phase-independent decision rules. The simplest decision rule selects the maximum magnitude of the MMSE filter outputs, and the other two account for the… (More)

- Ateet Kapur, Mahesh K. Varanasi
- IEEE Transactions on Information Theory
- 2003

Multiuser detection for overloaded code-division multiple-access (CDMA) systems, in which the number of users is larger than the dimension of the signal space, is of particular interest when bandwidth is at a premium. In this paper, certain fundamental questions are answered regarding the asymptotic forms and performance of suboptimum multiuser detectors… (More)

- Martin Döttling, Angeliki Alexiou, +14 authors Ernesto Zimmermann
- 2005

This document contains a first assessment of spatial transmission schemes regarding performance and complexity. In order to assess advanced beamforming and MIMO technologies, mathematical models, as well as methodologies for simulation and assessment have been developed. Conceptual work and simulation campaigns have been conducted. A baseline WINNER… (More)

— Noncoherent minimum mean-squared error (MMSE)-based multiuser receivers are proposed for nonorthogonal multipulse modulation. The three proposed receivers have a common MMSE pre-filter and are followed by one of three distinct noncoherent decision rules. The simplest decision rule selects the maximum magnitude of the MMSE filter outputs and the other two… (More)

- Ateet Kapur, Mahesh K. Varanasi, Clifford T. Mullis
- IEEE Transactions on Information Theory
- 2005

This correspondence characterizes the performance limitation of the well-acclaimed generalized Welch-bound equality (WBE) signals under linear minimum mean-squared error (MMSE) detection. It is analytically proven, and experimentally verified, that when users in an overloaded but finite-size code-division multiple-access (CDMA) system are allocated such… (More)

— This paper addresses signal optimization for CDMA systems under linear minimum mean-squared error (MMSE) detection. In particular, generalized Welch-bound equality (WBE) signals, which have been found to be optimum for various measures/problems, are studied from a new perspective. Specifically, we consider the asymptotic effective energy (AEE) criterion… (More)

— The maximization through signal design of the symmetric capacity of CDMA systems with optimal and minimum mean-square error decision feedback (MMSE-DF) decoding is considered. In particular, lower bounds on maximum symmetric capacity (and the signal set that achieves them) are derived for the two decoders. A common sufficient condition is obtained for… (More)

- Ateet Kapur, Mahesh K. Varanasi
- ICC
- 2003

— The problem of signal design for bandwidth efficient multiple access is addressed under quality of service (QoS) constraints specified by (possibly different) BER. Indeed, BER more accurately measures the performance than the signal-to-interference ratio (SIR) for uncoded communication. Furthermore, we argue that the asymptotic effective energy (AEE)… (More)

— The problem of optimizing signals for the Gaussian multiple access channel under Quality of Service (QoS) constraint is addressed. In particular, the Band-width Efficient Multiple Access (BEMA) approach of [1] is considered, wherein signals are designed at the base station and fed back to, and for use by, uplink transmitters, in order to minimize strict… (More)