False PN-code lock due to off-peaks of Gold sequence autocorrelation (satellite transponders)

Abstract

The author establishes that a false pseudo-noise (PN) code lock can happen with high probability for very strong signals if a Gold sequence is employed for the PN-spreading. The autocorrelation of a Gold sequence has off-peaks. The off-peaks may cause the final PN-code lock decision variable to exceed the preset threshold value when the received power is high, and yield false PN-code lock decisions. For example, the off-peaks can cause false PN-code lock when the received power exceeds -118 dBm and -103 dBm for 3 kb/s and 72 kb/s data rates, respectively. Thus, the received power should be below these numbers to avoid the false PN code lock. For a single-access system, it is recommended that the channel employ one of the two maximal-length sequences in a Gold sequence family and thus remove the off-peaks in a PN sequence autocorrelation.<>