Patent ID: 6061569
Filing Date: 2000-05-09
Classification: H04M,H04W

Abstract:
A telecommunications system comprising at least one primary radio station and a plurality of secondary radio stations, in which system a secondary radio station is matched to a primary radio station and a wireless communication between matched radio stations is done via a full duplex communication link, and the primary and the secondary stations are arranged for establishing the communication link to their respective opposite station while scanning for a free communication channel, whereby the stations have a transmitter and a receiver, characterised in that the station establishing the communication link is arranged for issuing an establishment request for establishing the communication link with the opposite station while applying a double checking protocol for checking whether both channels in the duplex communication link are free, which double checking protocol comprises the following steps:a) after having found a free channel, the establishing station switches on its transmitter and transmits at least one activation message to the opposite station,b) after having received and decoded an activation message, the opposite station switches on its transmitter on a free channel and checks for a first predetermined period of time whether the establishing station has switched off its transmitter within the first period on the channel on which its transmits the at least one activation message,c) the establishing station switches off its transmitter after having found a busy channel of the opposite station,d) if is ascertained that after the checking in b) the channel is free, the opposite station transmits at least one acknowledgement message on the channel it has selected after having received the activation message, ande) the establishing station switches on its transmitter on the channel it was transmitting the at least one activation message after having received and decoded the acknowledgement message.