Abstract
Prior to hardware implementation, simulation is an important step in the study of systems such as Direct Sequence Code Division Multiple Access (DS-CDMA). A useful technique is presented, allowing to model and simulate Linear Feedback Shift Register (LFSR) for CDMA. It uses the Scilab package and its modeling tool for dynamical systems Xcos. PN-Generators are designed for the quadrature-phase modulation and the Gold Code Generator for Global Positioning System (GPS). This study gives a great flexibility in the conception of LFSR and the analysis of Maximum Length Sequences (MLS) used by spread spectrum systems. Interesting results have been obtained, which allow the verification of generated sequences and their exploitation by signal processing tools.
Highlights
Compared to conventional access methods, Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA), the Code Division Multiple Access (CDMA) has three mainly advantages: it is a multiplexing scheme based on pseudo-random codes, a spread spectrum system with a wide frequency band, and it occurs security of the air interface
In this work we present firstly the polynomials that are used for the CDMA and their corresponding Maximum Length Sequences (MLS)
CDMA uses another register i.e. the “Long Code Generator”, it is a Linear Feedback Shift Register (LFSR) modelled by a polynomial of degree 42, it intervenes in the allocation of user codes (Multiple Access) [2] [3]
Summary
Compared to conventional access methods, Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA), the CDMA has three mainly advantages: it is a multiplexing scheme based on pseudo-random codes, a spread spectrum system with a wide frequency band, and it occurs security of the air interface. The DSSS method is the technique that is adopted by CDMA mobile networks. In this work we present firstly the polynomials that are used for the CDMA and their corresponding Maximum Length Sequences (MLS). We give their block diagrams and implement them in Scialab/Xcos. The Q-Channel is designed and we give a simulation and analysis of direct sequence spreading in Xcos using this channel. To show the wide range of possibility given by our simulation method, we model another kind of. (2015) Modeling and Simulation of CDMA Codes in Scilab. Sequence Generator, the Gold Code used for GPS, and make detail analysis of generated sequences
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