Robust Frame Synchronization for Noisy PCM Systems

Serial digital transmission requires reliable frame synchronization at the receiver in order to demultiplex and recover the transmitted signals. This paper proposes a faster and more robust method of detecting frame synchronization. A large serial memory is used to store sufficient received history to include all bits of the synchronizing codeword. Equations have been developed which predict the search and "in frame" performance. These equations have been verified with laboratory models. Using, for example, the well-known D3 PCM system, the reframe time is improved from 48 to 3 ms. With an error rate of 1 percent, the predicted "in frame" time is improved from 1.9 s to several centuries! Techniques for hardware implementation are suggested and application to the extended framing format is discussed.