Abstract
The synchronization and/or time acquisition problem in the presence of interferences has been strongly studied these last two decades, mainly to mitigate the multiple access interferences from other users in DS/CDMA systems. Among the available receivers, only some scarce receivers may also be used in other contexts such as F/TDMA systems. However, these receivers assume implicitly or explicitly circular (or proper) interferences and become suboptimal for noncircular (or improper) interferences. Such interferences are characteristic in particular of radio communication networks using either rectilinear (or monodimensional) modulations such as BPSK modulation or modulation becoming quasirectilinear after a preprocessing such as MSK, GMSK, or OQAM modulations. For this reason, the purpose of this paper is to introduce and to analyze the performance of second-optimal array receivers for synchronization and/or time acquisition of BPSK, MSK, and GMSK signals corrupted by noncircular interferences. For given performances and in the presence of rectilinear signal and interferences, the proposed receiver allows a reduction of the number of sensors by a factor at least equal to two.
Highlights
The synchronization and/or time acquisition problem in the presence of interferences has been strongly studied these last two decades, mainly to mitigate the multiple access interferences (MAI) from other users in DS/CDMA systems
Receivers presented in [8, 10] become sub-optimal for SO noncircular interferences. This property is characteristic of radio communication networks using either rectilinear modulations, such as amplitude modulation (AM), amplitude phase shift keying (ASK), binary phase shift keying (BPSK) modulations, or modulations becoming quasirectilinear after a preprocessing such as Minimum Shift Keying (MSK), Gaussian MSK (GMSK), or offset quadrature amplitude modulations (OQAM) [16]
This receiver, patented recently [20], implements an optimal, in an least square (LS) sense, widely linear (WL) [21] spatial filtering of the data followed by a correlation operation with a training sequence
Summary
The synchronization and/or time acquisition problem in the presence of interferences has been strongly studied these last two decades, mainly to mitigate the multiple access interferences (MAI) from other users in DS/CDMA systems. The BPSK modulation is still of interest for various current wireless systems [15], whereas MSK and GMSK modulations may be interpreted as a BPSK modulation after a simple algebraic operation of derotation on the baseband signal [17,18,19] For these reasons, the first purpose of this paper is to introduce and to EURASIP Journal on Advances in Signal Processing analyze the performance of the SO optimal array receiver for synchronization and/or time acquisition of BPSK signals corrupted by noncircular, and more precisely by rectilinear interferences.
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