All PSoC Application Notes

AN2373: Ranking Original Pseudo-Noise Ranking Original Pseudo-Noise Codes in a DSSS System

If a WirelessUSB or any direct-sequence spread spectrum (DSSS) system is to be used with unique pseudo-noise (PN) codes, an assessment should be done of the code’s auto-correlation properties. Being able to assess the quality of a given PN code relative to another is important in choosing a code appropriate for an application. An algorithm was developed to rank PN codes by assigning a score based on the length of the groups of overlapping sections of the code. The algorithm is too inefficient to use to find the optimal PN codes. However, optimal PN codes are not necessary, but good PN codes are. Range testing results prove the ranked PN codes out performed each other by the average number of retries needed for successful communication. Therefore, the ranking of the codes should suffice in order to determine that any PN codes chosen are acceptable for use. The codes provided by Cypress were determined not to be the optimal found by the algorithm. This is because the criteria that the algorithm assesses do not include cross correlation properties. This rationale postulates that the list provided by Cypress is a good starting point to generate original PN codes, if needed.