Abstract
We propose a simpler and faster Gold codes generator, which can be efficiently initialized to any desired code, with a minimum delay. Its principle consists of generating only one sequence (code number 1) from which we can produce all the other different signal codes. This is realized by simply shifting this sequence by different delays that are judiciously determined by using the bicorrelation function characteristics. This is in contrast to the classical Linear Feedback Shift Register (LFSR) based Gold codes generator that requires, in addition to the shift process, a significant number of logic XOR gates and a phase selector to change the code. The presence of all these logic XOR gates in classical LFSR based Gold codes generator provokes the consumption of an additional time in the generation and acquisition processes. In addition to its simplicity and its rapidity, the proposed architecture, due to the total absence of XOR gates, has fewer resources than the conventional Gold generator and can thus be produced at lower cost. The Digital Signal Processing (DSP) implementations have shown that the proposed architecture presents a solution for acquiring Global Positioning System (GPS) satellites signals optimally and in a parallel way.
Highlights
The spreading codes are the most important elements of the Direct Sequence Code Division Multiple Access (DS-CDMA) communications [1]
An efficient method for generating and acquiring C/AGPS signals based on bicorrelation function principle is proposed in this paper
This method takes advantage of the relationships between the different Coarse Acquisition (C/A)-Gold codes that are derived from the slices of the bicorrelation function
Summary
The spreading codes are the most important elements of the Direct Sequence Code Division Multiple Access (DS-CDMA) communications [1]. GPS system uses Gold codes that are generated by two LFSRs expressed each as coefficients of a polynomial. In cold-start case, no information is available to help acquiring signals and determining the satellites in view; the acquisition times may take several minutes. Reacquisition start is the process when satellites signals have just been lost and are acquired again; the receiver has good knowledge of time and Doppler shift [32]. The acquisition of a specific satellite from the total constellation involves performing the correlation between the code corresponding to this satellite and its replica that is locally generated. An increasing number of visible satellites increase the requirements of the hardware components and circuitry, which is a limitation of classical LFSR based Gold codes generator
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