Verification of pn synchronization in a direct-sequence spread-spectrum

Abstract

In a direct sequence spread spectrum digital communication receiver, a system and method for recovering and verifying the timing or phase of a pseudo-random noise (PN) sequence used for despreading received signals. In one embodiment, the method includes steps of: (a) determining an initial value of a received PN phase, (b) setting the receiver's PN phase equal to the initial value of the received PN phase, (c) a first testing to verify that the receiver identifies a SYNC field within a testing time of predetermined duration, (d) a second testing, to verify that temporarily shifting the receiver's PN phase results in a degraded correlation between the receiver's PN sequence and the received signal, and (e) repeating steps (a)-(d) if either of the testings indicate that the receiver's PN sequence is not correct. One embodiment of a system for recovering and verfying the PN timing includes an input for receiving a received spread-spectrum data stream, a maximal likelihood detection logic, a receiver PN clock, a despreading mixer that generates a narrowband signal from the spread-spectrum data stream, a first testing logic that generates a PASS output if it identifies a SYNC field in the narrowband signal during a testing period, and a second testing logic that temporarily shifts the receiver PN clock and generates a PASS output if the temporary shifting degrades the correlation between the receiver's PN sequence and the received signal.