Journal ArticleDOI
The impact of timing errors on the performance of linear DS-CDMA receivers
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TLDR
An asynchronous direct-sequence code-division multiple-access (DS-CDMA) communication system operating over an additive white Gaussian noise (AWGN) channel is considered and the performance degradation errors impose on linear detectors, especially the decorrelating detector is the topic of this paper.Abstract:
In this paper, an asynchronous direct-sequence code-division multiple-access (DS-CDMA) communication system operating over an additive white Gaussian noise (AWGN) channel is considered. In many applications, the near-far problem can be the limiting factor for the capacity of a DS-CDMA system. Several near-far resistant receivers have, therefore, been proposed (e.g., the decorrelating receiver). These receivers assume perfect knowledge of the propagation delay from all users to the receiver. In practice, the delays are estimated and therefore subject to errors. The performance degradation these errors impose on linear detectors, especially the decorrelating detector, is the topic of this paper.read more
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Journal ArticleDOI
Soft handoffs in CDMA mobile systems
D. Wong,Teng Joon Lim +1 more
TL;DR: The benefits and disadvantages of using soft handoff over hard handoff are discussed, with the two most well-known benefits are fade margin improvement and higher uplink capacity, while disadvantages include increased downlink interference and more complex implementation.
Journal ArticleDOI
Code-spread CDMA using maximum free distance low-rate convolutional codes
TL;DR: The performance of these codes for spectrum spreading in a CDMA system is evaluated and shown to outperform that of orthogonal and super-orthogonal codes as well as conventionally coded and spread systems.
Journal ArticleDOI
A simulation comparison of multiuser receivers for cellular CDMA
TL;DR: A comparison of five of the most discussed receiver structures: the decorrelator, the minimum mean square error (MMSE) receiver, the multistage parallel interference cancellation receivers, the successive interference cancellation receiver, and the decor Relating decision feedback receiver.
Book
IEEE transactions on acoustics, speech, and signal processing
TL;DR: A low-cost recognition system for isolated words and small vocabulary (typically 15 words) is described, with possibility of integration in a stand-alone small-size CMOS chip, very-low-power consumption, and automatic adaptation to the speaker without any tedious training mode.
Multiuser demodulation for DS-CDMA systems in fading channels
TL;DR: It is shown that the FIR detectors can be made near-far resistant under a given ratio between maximum and minimum received power of users by selecting an appropriate memory-length, and the iterative detectors are also shown to be applicable for parallel implementation.
References
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Digital communications
TL;DR: This month's guest columnist, Steve Bible, N7HPR, is completing a master’s degree in computer science at the Naval Postgraduate School in Monterey, California, and his research area closely follows his interest in amateur radio.
Journal ArticleDOI
MUSIC, maximum likelihood, and Cramer-Rao bound
Petre Stoica,Nehorai Arye +1 more
TL;DR: The Cramer-Rao bound (CRB) for the estimation problems is derived, and some useful properties of the CRB covariance matrix are established.
Journal ArticleDOI
Crosscorrelation properties of pseudorandom and related sequences
TL;DR: This paper presents a survey of recent results and provides several new results on the periodic and aperiodic crosscorrelation functions for pairs of m-sequences and for Pair of related (but not maximal-length) binary shift register sequences.
Journal ArticleDOI
Multistage detection in asynchronous code-division multiple-access communications
TL;DR: A multiuser detection strategy for coherent demodulation in an asynchronous code-division multiple-access system is proposed and analyzed, showing that the two-stage receiver is particularly well suited for near-far situations, approaching performance of single-user communications as the interfering signals become stronger.
Journal Article
Near-far resistance of multiuser detectors in asynchronous channels
R. Lupas,Sergio Verdu +1 more
TL;DR: In this paper, the authors consider an asynchronous code-division multiple access (CDMA) environment where the receiver has knowledge of the signature waveforms of all the users and compare detectors by their worst case bit error rate in a low background noise near-far environment.