Frame synchronizers, suitable for use with continuous phase modulation (CPM) in the presence of phase and frequency offsets, are derived for periodically inserted preamble bits in continuous-mode transmission. The resulting frame synchronizers involve single or double correlations of the received samples with a local copy of the CPM samples corresponding to the preamble bits. Of particular interest in aeronautical telemetry is shaped offset QPSK, telemetry group version (SOQPSK-TG), with the preamble defined in the integrated network enhanced telemetry (iNET) standard. Two low-complexity versions that leverage the special properties of the iNET preamble and SOQPSK-TG operating at 2 samples/bit are developed. Simulation results show that most frame synchronizers are capable of achieving acceptable performance for Eb/N0 ≥ 0 dB and the maximum frequency offset that can be tolerated increases with Eb/N0 to about 3%of the bit rate.
['Michael Rice', 'Andrew McMurdie']
On frame synchronization in aeronautical telemetry