METHOD AND DEVICE FOR DATA TRANSMISSION

摘要

In order to measure the rate at which a terminal (2) can receive data from a source (5, 6, 7) the source temporarily increases it transmitting rate. The time taken to receive these higher-rate transmissions is measured at the terminal (or acknowledged by the terminal and measured at the transmitter) a nd the rate calculated. Inter alia, these measurements can be used for control of layered coding where apparatus for transmitting signals to video or other terminals (2) has coding means (5) for receiving the signals to generate a base signal stream (B) which is a coarse representation of the signal to be transmitted and at least one higher order stream (E1, E2) containing finer detail of the signal not present in any lower order stream. These streams ar e sent by transmitting means (6) to the terminals, but at least some of the terminals do not receive all of the higher order streams.