Terminal address assignment in a broadcast transmission system

A method of assigning addresses to a plurality of terminals in a broadcast transmission system in which in normal operation messages and said addresses are transmitted between a master station and said terminals, the method comprising the steps of:

• (a) reducing to low level the strength of the signal transmitted by the master station, whereby each terminal is subjected to a high bit error rate;
• (b) transmitting from the master station a general polling message to which any terminal may respond;
• (c) transmitting a response from each terminal which receives the general polling message with a tolerable bit error rate and which has not yet been assigned an address;
• (d) detecting in the master station whether there is no response, a single response, or multiple responses to the general polling message and in dependence upon such detection proceeding with step (e), (g), or (f) respectively;
• (e) increasing by an amount D the strength of the signal transmitted by the master station and returning to step (b);
• (f) decreasing the magnitude of the amount D, reducing by the new amount D the strength of the signal transmitted by the master station, and returning to step (b);
• (g) transmitting an assigned address from the master station;
• (h) transmitting from each terminal which receives an assigned address an acknowledgement of the assignment;
• (i) detecting in the master station each acknowledgement of the assigned address, and in the absence of such detection returning to step (f);
• and
• (j) increasing the magnitude of the amount D and returning to step (e) until a normal operating strength of the signal transmitted by the master station is reached.

A master station for use in a broadcast transmission system in which in normal operation messages and terminal addresses are transmitted between the master station and a plurality of terminals each with an assigned address, the master station including means for assigning said addresses to said terminals, said means comprising:

• means for transmitting a general polling message to which any terminal may respond;
• means for detecting whether no response, a single response, or multiple responses are received from the terminals in response to the general polling message, and for varying in dependence upon such detection at least one parameter which affects the bit error rate of the terminals, whereby in response to a general polling message a single response from one terminal is received;
• means for transmitting an assigned address to said one terminal;
• and
• means for repeating the general polling message until each of the terminals has been assigned an address.

A terminal for use in a broadcast transmission system in which in normal operation messages and terminal addresses are transmitted between a master station and a plurality of such terminals each with an assigned address, the terminal comprising:

• means responsive to a high bit error rate of its received signal for assuming a first state in which the terminal does not transmit;
• means responsive to a reduced bit error rate of its received signal for assuming a second state in which the terminal transmits a response to a general polling message from the master station;
• and
• means responsive to an address received from the master station while in the second state for adopting said address as its assigned address and assuming a third, normal operating state in which the terminal does not respond to said general polling message.