System and method for low overhead multiplexing of real-time and non-real-time data

Abstract

A system and method for low latency multiplexing of real-time and regular data in the same data frame. Real-time data capable of being delivered at regular intervals (such as digitized voice) is multiplexed with regular (non-real-time data) across a communications link (such as a modem connection). The link's existing packet protocol (such as V.42/HDLC) may be extended to provide low latency for the real-time data, with minimal impact on existing data-transfer efficiency. Before each data frame is transmitted, the transmitter determines the time before the next real-time data will become available for transmission. If the real-time data will become available before the data frame will have been completely transmitted, the real-time data may be embedded within the frame as follows. Bit values within the header of the data frame may be used to indicate the offset within the frame of the start of the real-time data. Regular data may be transmitted until this offset is reached, at which point a “capsule” of real-time data may be inserted into the data stream. The receiver may use the bit values to determine where to start interpreting the data stream as a capsule. After inserting the capsule, the transmitter may resume transmitting the regular data. Both transmitter and receiver determine when the next real-time data is expected by adding a predetermined amount to the offset of the previous capsule. When this offset is reached another capsule is transferred. This continues until the end of the frame is reached.