Call admission control for Wi-Fi
View Patent ↗Call admission control within a wireless network is implemented using a service controller that manages a set of access points. The call admission control (CAC) function for a given access point determines whether the access point has sufficient unused bandwidth to handle an additional call. The service controller makes this determination by monitoring the access points and evaluating certain probability functions and load conditions. In one embodiment, a determination of whether the access point has sufficient unused bandwidth to handle an additional call is a function of two (2) independent probabilities: (i) a probability of an active session moving to the access point from one or more neighbor access points, and (ii) a probability of an idle mobile device already associated with the access point entering into a new active session by initiating an inbound or outbound call. According to another aspect, the service controller issues and manages “call admission credits” among the set of access points, where a call admission credit value indicates a number of calls that idle mobile devices associated with the access point may initiate from the AP. The call admission credits value is a function of a determined load on the AP, and a mobility probability, which is a probability of an active call moving to the access point from one or more neighbor access points. The call admission credit value for the access point is adjusted as a function of a change of the load or in the mobility probability.
1. A method of call admission control operative within a wireless network having a set of access points, comprising:
in response to a call admission control request received at an access point from a mobile device, determining whether the access point has sufficient unused bandwidth to handle an additional call; and
if the access point has sufficient unused bandwidth to handle the additional call, accepting the CAC request;
wherein the determination of whether the access point has sufficient unused bandwidth is a function of (i) a probability of an active session moving to the access point from one or more neighbor access points, and (ii) a probability of an idle mobile device associated with the access point entering into a new active session.
2. The method as described in claim 1 wherein the probability of an active session moving to the access point from a given neighbor access point of the one or more neighbor access points is a function of a number of active sessions for the given neighbor access point for a given admission class.
3. The method as described in claim 2 wherein the probability of an active session moving to the access point also is a function of a value that represents a historic or defined ratio of a number of current mobile devices for the given neighbor access point and the admission class over a given time period in a day.
4. The method as described in claim 3 wherein the probability of an active session moving to the access point is represented by the following:
Pmob[AP][Ac]=T _Active_Calls [AP][Ac]X Mover_Ratio [AP][AC] [Curr_Period]
where:
Pmob: represent the probability a user device currently associated to the neighbor access point will handover to the access point;
T_Active_Calls: represents the number of active sessions for the access point and a specific admission class on the access point;
Mover_Ratio: represents a historical or defined ratio of current user devices for the access point and admission class at a specific period of the day;
Curr_Period: represents a current period of time; and
Mover_Ratio [AP][Ac] [Period]= T _Active_Calls 13 that_moved [AP][AC][ Period]/ T _Active_Calls_Period [AP][Ac][Period]
where:
Mover_Ratio: represents the historical or defined ratio of current user devices for the access point and the admission class at the specific period of the day;
T_Active_Calls_that_moved: represents the number of active sessions for the access point and the admission class on that access point that moved to another access point in the neighborhood of the access point; and
T_Active_Calls_Period: represents the number of active sessions for the access point and the admission class on that access point for the specific period of the day.
5. The method as described in claim 1 wherein the determination also is based on a load at the access point.
6. The method as described in claim 1 wherein the determination is made at a location other than at the access point that receives the call admission control request.
7. The method as described in claim 6 wherein the determination is made at a controller to which the access points are associated.
8. The method as described in claim 7 further including having the controller determine a potential load on the access point that is a function of an Erlang value, the Erlang value representing a maximum number of simultaneous active sessions per admission class across the set of access points.
9. The method as described in claim 1 wherein the access point is compliant with IEEE 802.11e.
10. The method as described in claim 1 wherein a neighbor access point is a given access point that is sufficiently close to the access point such that a mobile device is movable from the given access point to the access point without losing connectivity.
11. A controller for use in a wireless network, the network having a set of access points each having a predetermined service area, wherein mobile devices receive a communication service by associating with access points in the set, comprising:
a processor;
program code, executable by the processor, to implement a call admission control operation at an access point within the set of access points as a function of one or more of: (i) a probability of an active call moving to the access point from a neighbor access point, and (ii) a probability of an idle mobile device associated with the access point initiating a new call.
12. The controller as described in claim 11 wherein the new call is an inbound call or an outbound call.
13. The controller as described in claim 11 wherein the call admission control function is also based on a load at the access point.
14. The controller as described in claim 13 wherein the load at the access point is determined as a function of one or more admission classes.
15. The controller as described in claim 14 wherein the load is a function of an Erlang value.
16. The controller as described in claim 15 wherein the Erlang value is a maximum number of simultaneous calls expected per admission class across the set of access points.
17. The controller as described in claim 11 further including program code executable by the processor to establish and maintain a secure communication link to each of the access points in the set.
18. The controller as described in claim 11 further including program code executable by the processor to collect data from the access points, wherein the data is used to calculate the probabilities.
19. A system, comprising, in combination:
a set of access points each having a predetermined service area, wherein mobile devices receive a communication service by associating with access points in the set; and
a controller, comprising:
a processor;
program code, executable by the processor, to implement a call admission control operation at an access point as a function of one or more of: (i) a probability of an active call moving to the access point from a neighbor access point, and (ii) a probability of an idle mobile device associated with the access point initiating a new call.
20. The system as described in claim 19 wherein a given access point in the set of access points is compliant with IEEE 802.11 e.
21. The system as described in claim 19 wherein the controller further includes program code executable by the processor to establish and maintain a secure communication link to each of the access points in the set.
22. The system as described in claim 19 wherein the controller further includes program code executable by the processor to collect data from the access points, wherein the data is used to calculate the probabilities.
23. A method for issuing and managing call admission credits among a set of access points, comprising:
determining a load on an access point; and
issuing a call admission credit value to the access point as a function of the determined load and a mobility probability, wherein the call admission credit value indicates a probability of a number of calls that idle mobile devices associated with the access point may initiate and that can be accepted by the access point.
24. The method as described in claim 23 further including, at a later time, adjusting the call admission credit value as a function of a change in the mobility probability or the load on one of: the access point and the set of access points.
25. The method as described in claim 23 wherein the mobility probability is a probability of an active call moving to the access point from one or more neighbor access points.