Bandwidth allocation method and apparatus
A satellite communications system provides a communications service to a mobile terminal on which different communications applications may be run. Calls are set up between any of the applications via a satellite to a network management centre which provides different service adaptors which adapt the calls to different types of service provided over terrestrial networks, such as telephony, facsimile, internet or ATM services. The bandwidth allocated to each call over the satellite link may be varied during the call according to demand either from the relevant application or from the network management centre. Multiple calls may be connected concurrently to or from different applications running on the mobile terminal. A maximum bandwidth is allocated to each call. Efficient use is thereby made of the limited bandwidth available over the satellite, according to the instantaneous bandwidth requirements of different applications. For real-time calls requiring multiple slots per frame in a TDMA channel, the slots are mutually spaced apart to reduce delay.
1. A method of handling a call to or from a mobile terminal over a wireless link to a base station connected to a communications network, comprising:
when setting up the call, determining a maximum bandwidth allocation for the call; and
during the call, varying the current bandwidth allocation for the call over the wireless link in accordance with a variable bandwidth demand relating to the call without exceeding said maximum bandwidth allocation,
wherein the current bandwidth allocation includes a forward bandwidth allocation, the forward bandwidth allocation being varied during the call in accordance with a forward channel demand relating to the call, the method further comprising transmitting from the base station to the mobile terminal using the forward bandwidth allocation; and
wherein the forward channel demand is derived from the quantity of buffered data received from the network for transmission to the mobile terminal.
2. A method as claimed in claim 1 , wherein the current bandwidth allocation includes a return bandwidth allocation, further comprising receiving a demand signal at the base station from the mobile terminal, the return bandwidth allocation being varied in accordance with said demand signal, the method further comprising transmitting from the base station to the mobile terminal allocation data indicating the return bandwidth allocation, such that the mobile terminal uses the return bandwidth allocation for transmission to the base station.
3. A method as claimed in claim 2 , wherein said minimum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
4. A method as claimed in claim 3 , wherein said call set-up fails if said requested minimum bit rate is not available.
5. A method as claimed in claim 2 , wherein said maximum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
6. A method as claimed in claim 2 , wherein the forward bandwidth allocation is determined independently of the return bandwidth allocation.
7. A method as claimed in claimed 6 , wherein said minimum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
8. A method as claimed in claim 6 , wherein said maximum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
9. A method as claimed in claim 7 , wherein said call set-up fails if said requested minimum bit rate is not available.
10. A method as claimed in claim 2 , wherein the step of setting up said call includes determining a minimum bandwidth allocation for the call, and the current bandwidth allocation is varied without falling below said minimum bandwidth allocation.
11. A method as claimed in claim 10 , wherein said minimum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
12. A method as claimed in claim 11 , wherein said call set-up fails if said requested minimum bit rate is not available.
13. A method as claimed in claim 10 , wherein said maximum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
14. A method as claimed in claim 1 , wherein the step of setting up said call includes determining a minimum bandwidth allocation for the call, and the current bandwidth allocation is varied without falling below said minimum bandwidth allocation.
15. A method as claimed in claim 14 , wherein said minimum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
16. A method as claimed in claim 15 , wherein said call set-up fails if said requested minimum bit rate is not available.
17. A method as claimed in claim 14 , wherein said maximum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
18. A method as claimed in claim 1 , wherein said maximum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
19. A method as claimed in claim 18 , wherein the step of setting up said call includes determining a minimum bandwidth allocation for the call, and the current bandwidth allocation is varied without falling below said minimum bandwidth allocation.
20. A method as claimed in claim 18 , wherein the step of setting up said call includes determining a minimum bandwidth allocation for the call, and the current bandwidth allocation is varied without falling below said minimum bandwidth allocation.
21. A method as claimed in claim 19 , wherein said minimum bandwidth allocation is determined according to a request by the mobile terminal during call set-up.
22. A method as claimed in claim 21 , wherein said call set-up fails if said requested minimum bit rate is not available.
23. Apparatus for handling a call to or from a mobile terminal over a wireless link to a base station connected to a communication network, comprising:
call set-up means operable to set up the call and to determine a maximum bandwidth allocation for that call;
means operable to vary the current bandwidth allocation for the call over a wireless link in accordance with a variable bandwidth demand relating to the call, without exceeding said maximum bandwidth allocation,
wherein the current bandwidth allocation includes a forward bandwidth allocation, the forward bandwidth allocation being varied during the call in accordance with a forward channel demand relating to the call, such that the base station transmits to the mobile terminal using the forward bandwidth allocation; the apparatus further comprising
means for deriving the forward channel demand from the quantity of buffered data received from the network for transmission to the mobile terminal.