A Robust Timing and Phase Offset Estimation Technique for CPM-DSSS-Based Secured Communication Link

Abstract

Continuous Phase Modulation–Direct Sequence Spread Spectrum (CPM-DSSS) is a promising scheme for a secured Point-to-Point (P2P) communication system having Anti-Jamming (AJ) capabilities. However, like other communication systems, synchronization of CPM-DSSS based systems is required for reliable detection of data. This paper presents a novel algorithm for estimating the timing and phase offset for binary full-response CPM-DSSS based systems. A burst mode transmission is considered here, and within each burst, a training sequence is embedded along with data. Firstly, the entire burst is spread using DSSS and then modulated with CPM, which is later upconverted and passed on to the channel. After down-conversion at the receiver, the proposed algorithm estimates timing and phase offset from the received spread training sequence. Then estimation accuracy of the proposed algorithm is compared with the state-of-the-art. The results indicate that the proposed joint estimator is superior by 9 dB and 10 dB for the estimation of timing and phase offset, respectively, as compared to the existing algorithm. Furthermore, the estimator’s variance for three different frequency pulses is compared with Modified Cramer-Rao Bound (MCRB). The results suggest that the phase offset estimator’s variance approaches MCRB for all Signal-to-Noise Ratios (SNRs). The effectiveness of the proposed algorithm in the multipath fading channel is also demonstrated.

Keywords

• Timing offset
• carrier phase offset (CPO)
• continuous phase modulation-direct sequence spread spectrum (CPM-DSSS) scheme
• point-to-point (P2P) communication