PN code-aided ranging for optical satellite communication systems

A model for the pseudonoise (PN) code-aided estimation of the transmission path delay and ranging for direct-detection on-off-keying (OOK) optical intersatellite channels is suggested in which the intensity of the optical field is modulated by a PN code and random binary data symbols. A closed-loop code-tracking loop model, motivated by the maximum-likelihood (ML) estimation of the phase difference between the received PN code and a locally generated one, is obtained. The maximum-likelihood model is approximated and, consequently, receiver models for the high and low signal-to-noise ratio (SNR) are suggested. The resulting code tracking loop S-curves of the receivers are that of the S-curves of a noncoherent delay-locked loop (NCDLL). The performance of the two receivers under the influence of background noise, signal count and PN code length is obtained