Research On Sequence Mapping Algorithm With Error Correction Ability For PCSS System

Parallel Combinatory Spread Spectrum (PCSS) System is an improved method of spread spectrum communication, and proposed on the basis of soft spread spectrum. This system not only inherited the advantages from traditional spread spectrum, such as good concealment, low probability of intercept, but also has a highly band utilization and communication efficiency. So it has a broad application prospect and is suitable for the burst spread spectrum communication, high information rate spread spectrum communication, etc.PC/SS communication system, takes a combination of r PN sequences out of M PN sequences through mapping algorithm, and then transmission. At the receiving end, due to the effects of interference and noise, the selected maximal r PN sequences are not always the transmitted r PN sequences, there may be one or more sequences are received in error, thus a number of data errors will be received. But all existing mapping algorithms are designed to just complete the data-sequence mapping, and without the ability of error detection and correction. To solve this problem and improve anti- interference performance of the system,the data-sequence mapping algorithm with error correction ability was studied, and the main research content includes the following several aspects:(1) The error case of received sequences was analyzed, and its statistical law has been obtained, then combining with the characteristic of PC/SS system itself, cyclic mapping algorithm was proposed. The proposed algorithm can effectively reduce the error probability,through adding strong cyclic constraint relation in transmisted r sequences. Theoretical analysis and simulation results show that the error rate performance of cyclic mapping algorithm 2 orders of magnitude lower than conventional mapping algorithm under the same conditions, the reliability of PC/SS system is improved dramatically.(2) The relationship between the information transmitting ability and the minimum hamming distance of the select control vectors was analyzed. For the proplem that cyclic mapping algorithm is insufficient in information transmission capacity, the big hamming distance with enlarge detection scope algorithm was proposed. The proposed algorithm can effectively reduce the error probability in the case of producing less redundant information.Theoretical analysis and simulation results show that the error rate performance of cyclic mapping algorithm 1 orders of magnitude lower than conventional mapping algorithm under the same conditions, the reliability of PC/SS system is improved dramatically, and the information transmission ability is improved compared with cyclic mapping algorithm.(3) The potential error detection performance of enlarge detection scope algorithm was discovered, through analyzing its information redundancy. For the proplem that enlarge detection scope algorithm is limited in error correction ability, combining with the error detection performance,the improved enlarge detection scope algorithm and retransmission enlarge detection scope algorithm were proposed. They can improve the reliability of system even more than enlarge detection scope algorithm. Theoretical analysis and simulation results show that these two kinds of improved algorithm can effectively reduce the BER of PC/SS communication, and both have some practical value.