System for dynamically changing the length of transmit and receive

Abstract

An apparatus for and method of implementing a novel buffer based fall duplex communication system is disclosed. The disclosed invention is particularly useful in native signal processing systems wherein heavy contention of processor resources typically exist, such as in systems running multi-tasking operating systems. The communication system of the present invention includes a receiver, transmitter, CODEC and telephone hybrid. The major components of the system operate on a buffer of input samples consisting of a set of input bits. The communication system operates to generate a buffer of output samples consisting of a set of output bits. The invention utilizes a novel dynamic buffer size mechanism to optimize the tradeoff between buffer delay and processing time period, on one hand, and robustness to interrupt latency and processor availability on the other hand. Small buffers provide the communication system with short, accurate response times in addition to short processing times. Using a large buffer of spare or dummy samples to be transmitted while the CPU is unavailable reduces the probability of a buffer underrun, thus giving the operating system greater leeway in deciding the exact time the signal processing functions in the modem routine are run. In this manner latency time is held to a minimum and data is not lost or corrupted. The concept of using dummy bits or silence for the generation of spare samples enables the elimination of additional latency caused by the spare samples by overriding them if they are not transmitted. This is achieved without a loss of signal coherency.