Method and apparatus for adjusting service rate to adapt to channel conditions
An approach is disclosed for a satellite terminal to utilize a lower transmit rate when transmission conditions do not permit the terminal to successfully transmit at a higher, preferred service rate. The terminal monitors retransmissions to determine whether transmission is possible at the higher rate. As an initial measure, the terminal first tries another inroute (or inroute group) at the preferred service rate before any attempt to switch to a lower service rate. If this other inroute group still poses a problem for successful transmission, the terminal switches to a lower service rate. The terminal remains at the lower service rate for a predetermined, configurable amount of time. This arrangement has particular applicability to a satellite network that provides data communication services.
1 . A method for adapting to transmission conditions in a radio communication system, the method comprising:
tracking the number of retransmissions over a first inroute of the radio communication system, the first inroute supporting a first rate;
determining whether the number of retransmissions exceeds a predetermined threshold; and
switching to a second inroute of the radio communication system if the number of retransmissions exceeds the predetermined threshold, the second inroute supporting a second rate, wherein the second rate is lower than the first rate.
2 . A method according to claim 1 , wherein the first inroute is part of an inroute group that includes a plurality of inroutes supporting the first rate, the method further comprising:
selecting, from the inroute group, an inroute that is different from the first inroute before switching to the second inroute.
3 . A method according to claim 2 , wherein the selected inroute is based on an accumulated metric value.
4 . A method according to claim 1 , wherein each of the rates is specified by a data rate and a coding scheme.
5 . A method according to claim 1 , further comprising:
transmitting data over the second inroute for a predeterminded duration; and
after the predetermined duration, switching to an inroute of the first rate.
6 . A method according to claim 1 , wherein the radio communication system is a satellite communication system, and the inroutes are contention channels.
7 . A method according to claim 1 , wherein the contention channels support an ALOHA-based communication protocol.
8 . A computer-readable medium bearing instructions for adapting to transmission conditions in a radio communication system, said instruction, being arranged, upon execution, to cause one or more processors to perform the method of claim 1 .
9 . An apparatus for adapting to transmission conditions in a radio communication system, the apparatus comprising:
means for tracking the number of retransmissions over a first inroute of the radio communication system, the first inroute supporting a first rate;
means for determining whether the number of retransmissions exceeds a predetermined threshold; and
means for switching to a second inroute of the radio communication system if the number of retransmissions exceeds the predetermined threshold, the second inroute supporting a second rate, wherein the second rate is lower than the first rate.
10 . An apparatus according to claim 9 , wherein the first inroute is part of an inroute group that includes a plurality of inroutes supporting the first rate, the apparatus further comprising:
means for selecting, from the inroute group, an inroute that is different from the first inroute before switching to the second inroute.
11 . An apparatus according to claim 10 , wherein the selected inroute is based on an accumulated metric value.
12 . An apparatus according to claim 9 , wherein each of the rates is specified by a data rate and a coding scheme.
13 . An apparatus according to claim 9 , further comprising:
means for transmitting data over the second inroute for a predeterminded duration; and
after the predetermined duration, means for switching to an inroute of the first rate.
14 . An apparatus according to claim 9 , wherein the radio communication system is a satellite communication system, and the inroutes are contention channels.
15 . An apparatus according to claim 9 , wherein the contention channels support an ALOHA-based communication protocol.
16 . A method for adapting to transmission conditions in a radio communication system, the method comprising:
determining that a return channel, associated with a first data rate and a first coding scheme, is not available based upon the number of retransmissions over the return channel; and
switching to another return channel, associated with a second data rate and a second coding scheme, wherein at least the first data rate or the first coding scheme is different from the second data rate or the second coding scheme.
17 . A method according to claim 16 , further comprising:
switching back to the return channel after a predeterminded duration.
18 . A method according to claim 16 , wherein the radio communication system is a satellite communication system, and the return channels are contention channels.
19 . A method according to claim 16 , wherein the contention channels support an ALOHA-based communication protocol.
20 . A computer-readable medium bearing instructions for adapting to transmission conditions in a radio communication system, said instruction, being arranged, upon execution, to cause one or more processors to perform the method of claim 16.