Spread-spectrum technology is widely used in communication system particularly in Global Navigation Satellite System (GNSS) to achieve a better ranging accuracy. This makes spreading code (also known as ranging code) ...
详细信息
ISBN:
(纸本)9791188428021
Spread-spectrum technology is widely used in communication system particularly in Global Navigation Satellite System (GNSS) to achieve a better ranging accuracy. This makes spreading code (also known as ranging code) so important that any change of it would directly influence positioning accuracy, compatibility, anti-interference, security, and receiver performance. Therefore, research on ranging code could provide theoretical support for the improvement of the performance of ranging codes and extension of their design methods to future satellite navigation signal structures. Chaotic sequence is not predictable and non-periodic so that has great auto-correlation and cross-correlation characteristic. However, the code balance of chaotic sequence is barely satisfactory, in this paper, a novel ranging code is proposed and we will give the details of the ranging code design process based on improved Logistic-map chaotic sequences and m code. Then the code select criteria based on even/odd correlation functions and welch bound have been set up to compare different code sets which include the proposed code, common GPS code, common Beidou code, and Random code. Theoretical analysis and simulation results show that the proposed ranging code cannot only maintain excellent performance in the acquisition, tracking, and anti-interference performance as the GPS L5I code but also significantly improve balance performance to strong balance constraints and improve code length flexibility.
m code signal by the BOC modulation will be the military signal in the plan of GPS modernization. In the paper, m codemilitary signal strategy is analyzed, the modulation principal, the auto-correlation function of t...
详细信息
m code signal by the BOC modulation will be the military signal in the plan of GPS modernization. In the paper, m codemilitary signal strategy is analyzed, the modulation principal, the auto-correlation function of the signal are analyzed and simulated. The specialty of the spectrum-apart, the increased signal power level and the structure of navigation message indicate the improvement of anti-jamming performance for m code as compare with P/Y code signal, the simulation result of code tracking loops accuracy testify the higher measurement precision of m code compare with P/Y code signal.
The source coding problem is considered where the only information known about the source is the number of symbols n and the order of the symbol probabilities. In this case, the code which achieves the minimum average...
详细信息
The source coding problem is considered where the only information known about the source is the number of symbols n and the order of the symbol probabilities. In this case, the code which achieves the minimum average redundancy is known as the m code. It is the Huffman code for the average distribution of monotone sources, and thus is a fixed code which does not depend on the symbol probabilities. The m code is a near-optimal code not only in the sense of average redundancy, but also in terms of the redundancy for almost all monotone sources. No simple expression is known for the codeword lengths of the m code for a given alphabet size. In this letter, the structure of this code is investigated, and an estimate is given for the number of codewords of a given length. In particular, the number of codewords of length j + 1 for encoding 2n symbols is shown to be almost twice the number of codewords of length j for encoding n symbols.
暂无评论