Broadcast rate control allocation (BRCA) for congestion avoidance in satellite ATM networks
AssigneeEMS Technologies Canada, Ltd.
InventorsAugustin Iuoras, Peter Takats, Rocco Di Girolamo, Eko A. Wibowo
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Abstract
A congestion avoidance scheme for ABR services in an ATM satellite system is described. The scheme relies on the broadcast nature of a satellite system to control the rates at which user terminals can send their requests for capacity. The scheme is integrated with the uplink scheduler mechanisms and therefore it is capable of achieving high bandwidth efficiency. It also achieves fairness in satellite resource utilization, while guaranteeing low cell loss ratio with rather modest buffer size.
Claims22
In a satellite communication system carrying data traffic between a communication satellite and more than one user terminals, a method for congestion avoidance utilizing successive averaging intervals of fixed time duration in order to allocate bandwidth among the terminals sharing either an uplink channel, a downlink channel or both, each having a fair rate and loading conditions, the method comprising the steps of:
- measuring for each averaging interval, the arrival rates for ABR traffic and higher priority traffic, requests for capacity for ABR traffic and a number of active ABR sources;
- computing, at the end of each averaging interval, the fair rate and the loading conditions in each uplink and downlink channel, a rate adaptation for each uplink-downlink channel couple;
- the rate adaptation being one of a rate increase, a rate decrease or no rate change;
- broadcasting at each averaging interval, the congestion control messages to each of the more than one terminals, the congestion control messages comprising the fair rate and the rate adaptation for each uplink-downlink channel couple;
- computing within each of the more than one user terminals, in each averaging interval, an allowable cell rate at which a terminal can make requests for bandwidth.
In a satellite communication system supporting ABR services with a given cell loss tolerance, a method for managing queue size in the output ports of an on-board switch, the method comprising the steps of:
- providing a maximum queuing delay for ABR traffic;
- adapting an available capacity for the ABR traffic on downlink channels, by setting aside capacity for queue draining;
- computing a queue draining capacity by using a negative exponential function;
- providing an upper limit for the maximum draining capacity;
- attempting to always maintain the queuing delay below the provided upper limit.
Dependencies are inferred from the claim text.