Measurement-based admission control for wireless packet data services
A call admission control technique is described which is well-suited for wireless systems providing real-time services over a shared downlink. The call admission control technique considers both multiplexing and multi-user diversity gain. The technique accurately determines the multi-user diversity gain by measuring per-user resource allocation and advantageously maximizes user accommodations under quality-of-service (QoS) as well as location-dependent resource availability constraints. In a further aspect, the call admission control technique is combined with delay-based scheduling, which effectively balances between system efficiency (channel exploitation) and user expectation (e.g., QoS). A system embodying the described call admission control and scheduling techniques can advantageously deliver efficient real-time services and remain robust to different load scenarios that vary according to system dynamics and/or user mobility.
1. An admission control method comprising:
receiving a scheduling decision at a measurement based load estimator for a communications resource;
measuring an existing load of the communication resource based on the scheduling decision;
estimating an additional load of a new user;
combining the existing load measurement and the additional load estimate to determine a combined load;
comparing the combined load to a system capacity; and
admitting the new user if the combined load does not exceed the system capacity, the new user being admitted based on the following relationship:
∑
k
=
1
K
m
K
(
K
+
1
)
B
k
(
t
)
+
m
i
E
[
r
i
(
t
)
]
≤
1
,
where K is a number of admitted users k, m k is a profile rate of an admitted user k, m i is a profile rate of the new user, E[r i (t)] is an estimated channel rate of the new user at time t, and B k (t) is an average measure of a communication resource allocated to the admitted user k at time t.
2. The method of claim 1 , wherein the scheduling decision is substantially instantaneous.
3. The method of claim 1 , wherein measuring the existing load includes measuring a radio resource allocated in accordance with the scheduling decision.
4. The method of claim 1 , wherein the communications resource is a shared downlink radio channel.
5. The method of claim 1 , wherein:
B
k
(
t
+
1
)
=
(
1
-
1
t
l
)
B
k
(
t
)
+
1
t
l
r
k
(
t
)
I
k
(
t
)
,
where r k (t) is a channel rate of admitted user k at time t and I k (t) is the scheduling decision for the admitted user k at time t.
6. The method of claim 1 comprising rejecting the new user if the combined load exceeds the system capacity.
7. The method of claim 1 , wherein the method is carried out at a cellular base station.
8. The method of claim 1 , comprising generating the scheduling decision.
9. The method of claim 8 , wherein the scheduling decision is generated in accordance with a maximum cost deduction (MCD) algorithm.
10. The method of claim 9 , wherein the MCD algorithm is a real-time MCD algorithm with a delay-based weight function.
11. The method of claim 10 , wherein the delay-based weight function is a linear function.
12. The method of claim 10 , wherein the delay-based weight function is an exponential function.
13. The method of claim 9 , wherein the MCD algorithm is a non-real-time MCD algorithm with a rate-based weight function.
14. The method of claim 13 , wherein the rate-based weight function is a linear function.
15. The method of claim 8 , wherein the scheduling decision is generated at a cellular base station.
16. The method of claim 1 , wherein the method is carried out at a radio network controller.
17. The method of claim 16 , comprising generating the scheduling decision, wherein the scheduling decision is generated at a cellular base station.