| 摘要 |
In a network for communicating data over a wireless channel (e.g. using infra-red radiation), a transmitting station is arranged to pause regularly during data transmission and monitor the communications channel for a confirmation signal from the receiving station that no interference has occurred. If no confirmation is received the transmitting station discontinues that transmission. The network uses a data code having a respective code symbol for each data value to be communicated, and in which superpositions of any two or more data symbols (e.g. because of interference between two transmitting stations) form symbols which are different from any valid data symbol. Thus interference generates invalid symbols which are directly detectable as such. Any other station which has received any data symbol or confirmation signal waits thereafter for a period at least equal to the interval between confirmation signals before attempting transmission itself. The network effectively regulates access to a shared communication channel, and in particular resolves the problem of 'hidden' stations which cannot directly receive signals from some other stations in the network but which can transmit to stations which do receive those signals, and can thus interfere with their reception of those signals. In this way the network can reduce waste of power and effective decrease in channel bandwidth which would otherwise occur. <IMAGE> |
