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Ultra-wideband (UWB) communication systems are usually implemented by baseband spreading schemes relying either on time hopping (TH) or direct sequence (DS) codes. However these schemes are not suitable to cancel narrow band interference (NBI). Other approaches rely on digital single carrier spreading (SC) or multi-carrier (MC) spreading codes, offering flexibility in NBI cancellation.
In this work, we propose a novel combined set-membership (SM) reduced-rank interference suppression scheme and consider its application to spread-spectrum multiuser direct sequence ultra-wideband (DS-UWB) systems. In the proposed scheme, the theory of set-membership filtering is applied to the training-based powers of R (PoR) multi-stage Wiener filter (MSWF) reduced-rank process and the reduced-rank...
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...
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,...
In this paper, interference mitigation through downlink power control is considered for macrocell Femtocell overlay. Specifically, the strong interference in the downlink from the home base station to a nearby macrocell user should be properly controlled such that the quality-of-service of both the macrocell user and the Femtocell users can be guaranteed. In this work, the fundamental capacity limitation...
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...
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