Burst Retransmission of PCM Telemetry Data

This paper discusses a technique for the real time retransmission of data from multiple asynchronous PCM telemetry links in a manner which will allow the times of individual samples to be accurately determined. The technique is called Periodic Burst and is characterized by the continuous tranmission of discrete blocks at rates which maintain the periodicity of parameters. A block is assembled from a single input link and will contain either a ??time of sync?? word or selected parameters. Blocks which contain parameters are assembled of samples which occur at a single rate during some prescribed time interval. The burst format is designed so that blocks from different links and at different rates are merged and burst transmitted at the rate at which these blocks were assembled. The sequence that a particular sample occurs relative to sync is known from the input links commutation format. If the commutation rate is also known or can be determined, the time of each sample can be established. The nominal commutation rate of a particular telemetry link will be known, but the actual commutation rate may differ by some tolerance, usually between 0.05% and 0.1%. To accurately determine sampling time, it is therefore necessary to determine the actual commutation rate. In the periodic burst technique, this is accomplished by assembling a ??time of sync?? block for each occurrence of sync and transmitting these blocks in the burst message.