Method of, and signalling system for, transferring data

摘要

A method of transferring data signals between a primary station ( 10 ) and secondary stations (SL 1 to SL 5 ) of a master/slave radio network, comprises the primary station assigning the secondary stations to a plurality of categories (Z 1 , Z 2 ). The primary station transmits beacon signals containing indications of those categories of the plurality for which it has data to be transferred. A secondary station operating in accordance with a wakeup sequence receives the beacon signals and determines if there is an indication of its category in a received beacon signal. If so, it transmits a request including an indication of its identity. The primary station checks to see if it has a data packet for the identified secondary station and, if it has, it transmits the data packet and, if not, it transmits a negative acknowledgement. Those secondary stations not participating in the exchange of messages can revert to a sleep mode thereby saving power.