Research And Application On Added Correlation Property Of Combinatory Sequence In Parallel Combinatory Spread Spectrum System

As the inheritance of direct sequence spread spectrum(DSSS)system's strong anti-interfence,anti-noise and multiple access communication ability,parallel combinatory spread spectrum(PCSS)system is hopeful to be the efficient solution of spread specrum system.Combinatory sequence plays an important role in PCSS system.Conventional sequence correlation property analysis method which is not able to give the system solution sheme more greatly and accrutely is not suitable for PCSS system.Basing on the charateristic of combinatory sequence,added correlation property analysis which can measure the correlation property influence to system performance is used in combinatory sequence.To optimize the system perfomace,added correlation properties of different sequences can be used in different compositions of PCSS system.In order to improve the system performance,further reseach on added correlation property,soft decision of QPSK modulation,and capture algorithm of combinatory sequence are given above:(1)Added correlation property of combinatory sequenceAdded correlation property analysis method is used to study Gold sequence,composite sequence and Walsh sequence.The added correlation property of Gold sequence whose added correlation property at zero time delay remains good is discussed;meanwhile the muti-peak values of added correlation property at non-zero time delay is analyzedo.According to the muti-peak property of cross-correlation functions at non-zero time delay,a smaller superposition sequences cross-correlation peak characteristic value selection method among Gold sequences is proposed to decrease added correlation mutual interference in the asynchronous system.Added correlation property of compound sequences is discussed.As the large added correlation sidelobe property,m-W sequence is suitable for synchronous parallel combinatory spread spectrum system.The added correlation property of G-W sequence which is composed of Walsh sequence set is not so good at non-zero time delay,so this sequence is not suitable for asynchronous system,either.The added correlation property of G-W sequence which is composed of Gold sequence set is simlar to that of Gold sequence,so the characteristic peak optimization is implemented in G-W sequence in order to enlarge the sequence kinds in asynchronous system.Based on present Walsh function properties,same code combination columns theorem and partial orthogonal property have been derived in a complete Walsh function set.According to the property of same code combination columns provides therical basis for partial orthogonal property.The proof of new property not only enriches the added correlation property research of Walsh sequence,but also embodys inherent regularity of codes distribution and establishes theoretical basis of its application in PCSS system.(2)Soft decision algorithm of combinatory sequence QPSK modulationBasing on the orthogonal added correlation property of combinatory sequence and partial orthogonal property of Walsh sequence,two soft decision algorithms——weighting soft decision and peak removal soft decision which are suitable for short wave channel of QPSK modulation are given.Further more,currently existing constellation diagram algorithm,weighting soft decision algorithm and peak removal soft decision algorithm are compared and simulated in bit error probability and minimum euclidean distance aspect.(3)Capture algorithm of combinatory sequenceTo sovle the problem of high complexity hardware and large calculation which is brought by combinatory sequence capture,glide correlation capture algorithm which can realize the capture of combinatory sequence is given.The simulation results not only prove the feasibility of the glide correlation capture but also verify the effectiveness of characteristic peak selection.To avoid the large calculation of glide correlation capture algorithm,three FFT fast capture algorithms which are colum summation,the max of row and the max of colum are given by combining the added correlation property analysis of receiving correlation value matrix.Three FFT fast capture algorithms are compared and simulated,and glide correlation capture algorithm is compared with FFT fast capture algorithm in calculation and capture probability aspects.