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We consider here the problem of multi-user detection for randomly spread direct-sequence (DS) coded-division multiple access (CDMA) over flat fading channels. The analysis is focused on the case of many users, and large spreading sequences such that their ratio, which is the system load, is kept fixed. Spectral efficiency of practical linear detectors such as match-filter and decorrelator employing...
The author presents new analytical approach of the bit error rate (BER) performance for multicode code division multiple access (CDMA) systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. Numerical results obtained from the proposed analytical approach indicate that the performance mismatch between the previous analysis and simulations is generated by the...
In addition to some design flexibilities, the low interference property of code division multiple access (CDMA) makes multi-carrier direct sequence CDMA (MC-DS-CDMA) suitable for possible unlicensed transmissions in the licensed bands. Introducing the concept of time division multiple access (TDMA) into MC- DS-CDMA may further create a new dimension dealing with the interference problem. In this paper,...
This paper proposes RADICAL independent component analysis (ICA) algorithm for detection of DS-CDMA signals and also effect of fading on ICA based detection of DS-CDMA has been studied. ICA based technique is based on independence of source signals and these conditions are satisfied in multi-user CDMA environment. Combining an ICA element to conventional signal detection reduces multiple access interference...
In the multicarrier code division multiple access (MC-CDMA) uplink, the base station receiver has the knowledge of the spreading sequences of all the users within the cell, but not that of the users from other cells. In this paper, we present a novel semi-blind adaptive MMSE multi-user detector based on subspace tracking for MC-CDMA systems in such scenarios. We develop an modified MMSE detector which...
In this paper, a lead compensator is proposed for compensating round-trip delay of direct-sequence code-division multiple-access (DS-CDMA) cellular mobile radio systems. Furthermore, in addition to the delay compensation, a disturbance rejection filter is designed to minimize the effect of uncertain noise and interference to track a desired signal to interference and noise ratio (SINR). The two-step...
Motivated by the recent development on iterate-averaging (IA) for accelerating convergence rates of stochastic approximation algorithms, and widely linear (WL) processing for improving performance of the linear minimum mean-squared error (MMSE) multiuser receivers, in this paper, a widely linear IA affine LMS algorithm (WL IA-ALMS) for adjustment of the WL MMSE filter for multiple access interference...
Cell overloading is a bandwidth efficient scheme to increase the number of users in a fixed bandwidth for mobile applications. One of the efficient schemes to overload a CDMA system is to use two sets of orthogonal signal waveforms (O/O) [2]. An iterative soft decision interference cancellation receiver (SDIC) scheme is used to cancel interference between the two sets of users. In this paper, the...
While two-dimensional (2-D) orthogonal variable spreading factor (OVSF) codes were proposed for multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) systems in order to eliminate multiple-access interference, the number of orthogonal sequences (or code cardinality) was restricted by the number of carrier frequencies. Non-orthogonal 2-D frequency-time-spreading (FTS) codes were then...
The AC coupling circuit is widely used in direct-conversion receivers to suppress the in-band DC offset and 1/f noise. This paper analyzes the requirements of the AC coupling circuit in a TD-SCDMA mobile phone operating in an environment with strong out-of-band interference. In this paper, a passive first-order high-pass filter is assumed to act as the AC coupling circuit. The recommended cutoff frequency...
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