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It is well known that spectral lines of the Global Positioning System (GPS) coarse acquisition (C/A) codes increase the amount of code division multiple access (CDMA) noise generated, occasionally far exceeding what is typically expected, depending on the user-satellite geometry. This degrades the available effective carrier-to-noise density ratio (C/N0)effective to a GPS receiver to a greater degree...
Spread spectrum signals are now widely used for secure communications, as well as for multiple access interference (MAI). They have many interesting properties, including low probability of interception. Indeed, DS/SS transmitters use a periodical pseudo-random sequence to modulate the baseband signal before transmission. A receiver which does not know the sequence can not demodulate the signal. Blind...
Bit error rate performance analysis for communications systems with diversity and partial-band interference often yields complicated probability density functions (PDFs) for the decision statistics. The authors calculate these PDFs via a new technique by evaluating the inverse Laplace transform as an integral of a real integrand over a finite range.
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...
In this paper, we propose a cognitive radio-based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided...
Code synchronization is the most important matter of concern in all applications involving direct sequence spread spectrum system, such as CDMA. Conventional synchronization techniques are primarily based on the auto/cross correlation properties of the spreading codes. The objective of the present paper is to propose a new method for fast and reliable code synchronization based on the abilities of...
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