Synchronization of pulse code modulation telemetry

Pulse Code Modulation (PCM) is one of the most widely utilized radio telemetry techniques for the recovery of test data from aerospace vehicles. Synchronization of the receiver with the transmitted data is perhaps the prime requisite of a PCM telemetry system. In this paper the frame synchronization process is analyzed by developing equations which define the three modes of synchronizer operation (SEARCH, VERIFY, and LOCK) in terms of the relative probabilities of operation. The criteria employed to optimize the synchronization process are the mean time to acquire true synchronization, the probability of true synchronization after verification of the synchronization decision, and the percentage of data last due to synchronization dropout (the dropout resulting from noise in the received signal). The results of this analysis are used to derive optimum synchronization system parameter settings for a hypothetical telemetry system. The problem of deriving an optimum PCM synchronization code is also presented. It is based on the criteria of minimum probability of false occurrence of the pattern in the received signal. Prior to discussing the frame synchronization problem, a general description of a typical airborne PCM telemetry system is made. Also, a brief description of bit synchronization and data regeneration techniques and their affect on the frame sync problem is included --Abstract, page ii