Abstract: A method of communicating different size items of information between terminals via channels of a time-division-multiplexed parallel bus (1) operating with a predetermined frame period (F) divided into a predetermined number of time slots. Each terminal transmits the whole of each of first size items in a respective separate first time slot and transmits the whole of each of second size items larger than the first size items each in a respective group of consecutive second time slots (M, M+1) in each frame. Preferably, the first time slots (N) are uniformly spaced apart so as to occur at a frequency which is multiple of the frame frequency. Preferably, the second size items are transmitted in two or more groups (M, M+1) of consecutive second time slots within each frame, said two or more groups being uniformly spaced apart.

Abstract: A packet transmission system comprising a network of one or more nodes (1) each comprising a number of inputs connected via packet switching means to a number of outputs each of which has storage means (11) associated with it in which to store a queue of packets to be outputted; characterized in that each node (1) is provided with timer means (14) to measure the time each packet spends in a queue of said storage means (11); and stamping means (12) to add to a time stamp field (TS) of each packet before it is outputted from the node, the time the packet has spent in a queue as measured by the timer means (14).

Abstract: A packet transmission system in which variable delays are compensated for by packetizing an input signal so as to produce packets at a predetermined packet frequency (3), allocating a sequence number to each packet (6), transmitting these packets over a network to an endpoint (7), and forming the packets into an output signal at the endpoint by reference to their sequence number (12) and by delaying each as necessary (9, 10) so that they are all delayed by substantially the same predetermined delay time with reference to the packet frequency. Preferably, the delay in the transmission of each packet through the network is measured by comparison of the time of arrival of the packet at the endpoint relative to a timing signal (11) synchronized with or running plesiochronously with the predetermined packet frequency.

Abstract: An adaptive data compression system comprises an encoder 2 which responds to input characters by producing output codewords according to a stored encoding map or table of characters and codewords, and an adapter 4, 5 which adapts the encoding map or table in accordance with the input characters so as to increase the compression ratio between the input characters and output codewords. An optimizer 5 monitors the performance of the system and accordingly varies adaptation of the encoding map or table by the adapter 4 so as to optimize performance of the system. Performance of the system is preferably monitored in terms of the computational loading of the processor and the compression ratio it achieves. A decoder 7 subsequently decodes the codewords by reference to a corresponding decoding map or table which is adapted 9, 10 in accordance with the output data from the decoder and in accordance with variations in the adaptation process in the encoder.

Abstract: A system in which core information, for example in the form of a core block or blocks (C), is transmitted in a core packet (PC), and at least some enhancement information, for example, in the form of enhancement blocks (E), is transmitted in an enhancement packet (PE) which is separate from the core packet (PC) and is discardable to relieve congestion. Preferably, the core and enhancement packets have headers (H) which include a discard eligible marker (DE) to indicate whether or not the associated packet can be discarded. The enhancement blocks (E) may be distributed between the core packet and enhancement packet in accordance with congestion conditions, or the enhancement blocks may be incorporated only in the enhancement packet, and the actual number of enhancement blocks included are varied depending on congestion conditions.