In this study, the authors propose a new method that eliminates ambiguity in global navigation satellite system (GNSS) code acquisition and tracking significantly. It is based on the use of a specified locally generated (SLG) pseudo-random noise code that can be correlated with any received binary offset carrier sine- or cosine-modulated signal. As a result, the correlation function (CF) together with its discriminator function (DF) at the delay locked loop (DLL) output, determined within a tracking region of (−1, 1) chips, are unambiguous and narrow, providing thus better positioning accuracy. On the other hand, the SLG-based methods CF and DF are such as those of high-resolution correlator and Strobe correlator, initially proposed for multipath mitigation in classical binary phase shift keying-modulated code. In addition, their proposed SLG-based scheme is valid for any value of the early–late chip spacing in the DLL-DF. The computer simulation results show that the proposed scheme is unambiguous for DLL code-tracking operation and has superior performance in the estimation of the delay of line of sight signal in GNSS applications.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-spr.2018.5379

Efficient technique for DLL S -curve side zero-crossings cancellation in global positioning system/Galileo receiver

Finding sets of binary sequences with low auto- and cross-correlation properties is a hard combinatorial optimization problem with numerous applications, including multiple-input-multiple-output (MIMO) radar and global navigation satellite systems (GNSS). The sum of squared correlations, sometimes referred to as the integrated sidelobe level (ISL), is a quartic function in the variables and is a commonly-used metric of sequence set quality. In this paper, we show that the ISL minimization problem may be formulated as a mixed-integer quadratic program (MIQP). We then present a block coordinate descent (BCD) algorithm that iteratively optimizes over subsets of variables. The subset optimization subproblems are also MIQPs which may be handled more efficiently using specialized solvers than using exhaustive search; this allows us to perform BCD over larger variable subsets than previously possible. Our approach was used to find sets of four binary sequences of lengths up to 1023 with better ISL performance than Gold codes and sequence sets found using existing BCD methods.

pdf/binary-sequence-set-optimization-for-cdma-applications-via-aooh8dkh.pdf

Binary Sequence Set Optimization for CDMA Applications via Mixed-Integer Quadratic Programming

Efficient method for constructing optimized long binary spreading sequences

Abstract Optimizing the correlation properties of spreading codes is critical for minimizing inter-channel interference in satellite navigation systems. By improving the codes’ correlation sidelobes, we can enhance navigation performance while minimizing the required spreading code lengths. In the case of low-earth orbit (LEO) satellite navigation, shorter code lengths (on the order of a hundred) are preferred due to their ability to achieve fast signal acquisition. Additionally, the relatively high signal-to-noise ratio in LEO systems reduces the need for longer spreading codes to mitigate inter-channel interference. In this work, we propose a two-stage block coordinate descent (BCD) method which optimizes the codes’ correlation properties while enforcing the autocorrelation sidelobe zero property. In each iteration of the BCD method, we solve a mixed-integer convex program over a block of 25 binary variables. Our method is applicable to spreading code families of arbitrary sizes and lengths, and we demonstrate its effectiveness for a problem with 66 length-127 codes and a problem with 130 length-257 codes. 

pdf/spreading-code-optimization-for-low-earth-orbit-satellites-2wcdx0fp6h.pdf

Spreading code optimization for low-earth orbit satellites via mixed-integer convex programming

Binary spreading codes with good auto- and cross-correlation properties are critical for satellite navigation to ensuring precise synchronization and tracking with minimal inter-system interference. In this paper, we demonstrate that multiple instances of the spreading code design problem found in the literature may be cast as binary-constrained convex optimization problems. This approach enables new optimization methods that can exploit the convex structure of the problem. We demonstrate the approach using a block coordinate descent (BCD) method, which uses a convexity-exploiting branch-and-bound method to perform the block updates. With minimal tuning, the BCD method was able to identify GPS codes with better performance compared to the Gold codes and codes derived from a recently introduced natural evolution strategy. 

Spreading Code Sequence Design via Mixed-Integer Convex Optimization

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.

/pdf/optimized-method-for-generating-and-acquiring-gps-gold-codes-1u1swl6shn.pdf

Optimized Method for Generating and Acquiring GPS Gold Codes

/pdf/corrigendum-to-optimized-method-for-generating-and-acquiring-1wmua45wqp.pdf

Corrigendum to “Optimized Method for Generating and Acquiring GPS Gold Codes”

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Optimized Method for Generating and Acquiring GPS Gold Codes

Efficient method for constructing optimized long binary spreading sequences

Corrigendum to “Optimized Method for Generating and Acquiring GPS Gold Codes”