Mobile Intelligent Roaming Using Multi-Modal Access Point Devices

• US 20100118830A1
• Filed: 12/19/2008
• Published: 05/13/2010
• Est. Priority Date: 11/10/2008
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Nayak, Seema, Kumar, Rajneesh, Stephenson, David Sheldon, Ghosal, Sudip
• Granted Patent: US 8,204,029 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04L 63/10 for controlling access to devices or network resources
• CPC Class Codes: H04W 36/0088 Scheduling hand-off measurements
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/1446 wherein at least one of the networks is unlicensed
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A system and method are provided in which access point (AP) devices in a wireless local area network (WLAN) are typed or configured into one of three measurement and reporting roles: Monitor-Mode AP (MMAP), Portal AP (PAP), a Border AP (BAP) or an Interior AP (IAP). APs are assigned specific link measurement requirements according to their assigned type or role. In general, MMAPs and PAPs have the greatest measurement and reporting responsibilities, BAPs have less measurement and reporting responsibilities than PAPs and IAPs have the least measurement and reporting responsibilities. The APs generate measurements that are supplied to appropriate equipment to facilitate handover decisions with respect to a dual-mode wireless client device that roams between the WLAN and another network or vice versa. As a result, link measurements are only performed by APs in locations where such measurements are necessary for handover service, thus reducing the overall processing load on the WLAN infrastructure.

Claims

1. A system comprising:

a plurality of wireless local area network access points configured to provide wireless communication in a first wireless network with wireless client devices including dual-mode wireless client devices that are configured to communicate with the first wireless local area network and with at least one other network; and

a central controller configured to communicate with the access points, wherein the central controller is configured to receive information defining a coverage domain that is associated with the plurality of access points, information related to locations of at least one handover point where a dual-mode wireless client device may roam between the first wireless local area network and the other network during a communication session, and information about locations of the plurality of access points, wherein the central controller is configured to assign measurement and reporting roles to each of the plurality of access points based on their radio frequency locations with respect to the handover points.

2. The system of claim 1, wherein the central controller is configured to assign a first measurement and reporting role to those access point devices that are closest in radio frequency location to a handover point, and wherein the central controller is configured to assign a second measurement and reporting role to those access points that are proximate borders of the coverage area.

3. The system of claim 2, wherein access point devices assigned to the first measurement and reporting role are configured to make receive signal strength measurements of signals received from the dual-mode wireless client devices during the communication session and to make packet loss and packet latency measurements associated with packets transmitted between the dual-mode wireless client device and the first wireless local area network during the communication session.

4. The system of claim 3, and wherein access point devices assigned to the first and second measurement and reporting roles are further configured to make receive signal strength measurements on request messages transmitted by the dual-mode wireless client device when it attempts to associate with a different access point.

5. The system of claim 1, wherein one or more of the plurality of access point devices that have a radio frequency location near a handover point are configured to operate in a monitoring mode and to scan a plurality of radio frequency channels in order to measure receive signal strength of signals, including signals transmitted by the dual-mode wireless client device, on each of the radio frequency channels for a period of time.

6. The system of claim 1, wherein the central controller is configured to register existence of a dual-mode wireless client device which may require handover to the other network, and to send messages to the wireless controllers as to an identity of the dual-mode wireless client device.

7. The system of claim 6, wherein the central controller configures the access points to make measurements and reports only for a dual-mode wireless client device that has registered with the central controller for handover to the other network.

8. The system of claim 1, wherein the central controller is configured to analyze data contained in reports received from the plurality of access points in order to determine when to generate a handover trigger for the communication session of the dual-mode wireless client device.

9. The system of claim 1, wherein the central controller is configured to track a state of a dual-mode wireless client device based on data that indicates whether the dual-mode wireless client device is transmitting voice call signals and the receive signal strength at access points that receive the voice call signals, and wherein the central controller is configured to assign one of a plurality of states to the dual-mode wireless client device depending on the presence of the voice call signals and the receive signal strength of the voice call signals.

10. The system of claim 9, wherein the central controller is further configured to determine when the receive signal strength of the voice call signals is less than a threshold to send a message to the dual-mode wireless client device requesting it to transmit a signal on at least one different RF channel than that in use for the voice call to allow one or more access point devices to make measurements of the signal on the different RF channel.

11. The system of claim 1, wherein the central controller is further configured to determine when one or more of the plurality of access points becomes inoperable in order re-compute a location of a handover point and/or make changes to the measurement and reporting roles of one or more other access points.

12. The system of claim 1, wherein the central controller is further configured to determine when measurement reports from multiple access points are not reaching the central controller in order to determine whether to discontinue handover service with respect to the dual-mode wireless client device.

13. The system of claim 1, wherein the central controller is further configured to generate a message that is sent to the dual-mode wireless client device via an access point that is in communication with the dual-mode wireless client device to cause the dual-mode wireless client device to transmit a first message on each of different radio frequency channels which upon reception cause access points that are operating on those different radio frequency channels to respond with second messages, and wherein access point devices that receive first messages are configured to measure the receive signal strength thereof and to send measurement reports to the central controller.

14. The system of claim 13, wherein one or more access points are configured to receive from the dual-mode wireless client device a report that contains receive signal strength measurements made by the dual-mode wireless client device on the second messages received by the dual-mode wireless client device on each of the different radio frequency channels, and to forward the report to the central controller.

15. The system of claim 1, wherein the other network is a second wireless local area network.

16. The system of claim 1, wherein the other network is a cellular network.

17. The system of claim 1, wherein three or more of the plurality of access point devices that have a radio frequency location near a handover point are configured to operate on the same radio frequency channel and in a mode that allows reception and processing of received signals without lower media access control filtering in order to measure receive signal strength of signals received on the same radio frequency channel, including signals transmitted by the dual-mode wireless client device.

18. A method comprising:

at a plurality of wireless local area network access points that are part of a first wireless local area network;

receiving signals from dual-mode wireless client devices that are configured to communicate with the first wireless local area network and at least one other network; and

measuring characteristics of signals received from dual-mode wireless client devices according to measurement and reporting roles assigned based on access point location relative to at least one handover point in a coverage area of the first wireless local area network where dual-mode wireless client devices may roam to the other network;

at a controller;

receiving measurement reports from the plurality of access points; and

analyzing data in the measurement reports to determine whether to generate a handover trigger to enable a dual-mode wireless client device to roam between the first wireless local area network and the other network.

19. The method of claim 18, wherein measuring comprises first measuring characteristics of signals received at one or more first access points that are located relatively close to the at least one handover point, and second measuring characteristics of signals received at one or more second access points that are located near borders of the coverage area.

20. The method of claim 19, wherein first measuring comprises measuring receive signal strength of signals received from a dual-mode wireless client device and measuring packet loss and latency associated with a communication session ongoing between the dual-mode wireless client device and the first wireless local area network.

21. The method of claim 20, wherein first and second measuring comprise measuring receive signal strength measurements on request messages sent by a dual-mode wireless client device when the dual-mode wireless client devices attempts to associate with a different access point.

22. The method of claim 18, and further comprising, at one or more access point that are located near the at least one handover point, scanning each of a plurality of radio frequency channels and measuring receive signal strength of signals, including signals transmitted by a dual-mode wireless client device, on each of the plurality of radio frequency channels for a period of time.

23. The method of claim 18, and further comprising transmitting a message to a dual-mode wireless client device via an access point that is in communication with the dual-mode wireless client device to cause the dual-mode wireless client device to transmit a first message on each of different radio frequency channels, receiving second messages at one or more of the plurality of access points on the different radio frequency channels that are transmitted by access points that receive the first message, and measuring receive signal strength of the second messages at one or more of the plurality of access points and sending measurement reports associated with the first messages to the controller.

24. The system of claim 23, and further comprising receiving at one or more of the plurality of access points from the dual-mode wireless client device a report that contains receive signal strength measurements made by the dual-mode wireless client device of second messages received on each of the different radio frequency channels, and forwarding the report to the controller.

25. A system comprising:

a plurality of wireless local area network access points configured to provide wireless communication in a first wireless network with wireless client devices including dual-mode wireless client devices that are configured to communicate with the first wireless local area network and with at least one other network, wherein each of the plurality of access points is configured according to one of several measurement and reporting roles to make measurements of signals associated with dual-mode wireless client devices based on RF locations of each access point with respect to at least one handover point where a dual-mode wireless client device may roam between the first wireless local network and the other network; and

a controller configured to communicate with the access points, wherein the controller is configured to receive and analyze data received from the plurality of access points in order to determine when to generate a handover trigger for the communication session of the dual-mode wireless client device.

26. The system of claim 25, wherein one or more access points that are closest in radio frequency location to a handover point are configured in accordance with a first measurement and reporting role to make measurements of received signals associated with a dual-mode wireless client device and report measurements to the controller, and one or more access points that are proximate borders of the coverage area are configured in accordance with a second measurement and reporting role to make measurements of received signals associated with the dual-mode wireless client device and report measurements to the controller.

27. The system of claim 26, wherein one or more access points that are configured according to the first measurement and reporting role are configured to make receive signal strength measurements of signals received from the dual-mode wireless client device during the communication session and to make packet loss and packet latency measurements associated with the communication session.

28. The system of claim 27, wherein one or more access points that are configured according to the first and second measurement and reporting roles are configured to make receive signal strength measurements on probe request messages transmitted by the dual-mode wireless client device when it attempts to associate with a different access point.

29. The system of claim 25, wherein one or more of the plurality of access points that have a radio frequency location near a handover point are configured to operate in a monitoring mode and to scan a plurality of radio frequency channels in order to measure strength of signals including signals transmitted by the dual-mode wireless client device on each of the radio frequency channels for a period of time.

30. The system of claim 25, wherein the controller is further configured to generate a message that it sends to the dual-mode wireless client device via an access point that is in communication with the dual-mode wireless client device to cause the dual-mode wireless client device to transmit a first message on each of different radio frequency channels which upon reception cause access points that are operating on those different radio frequency channels to respond with second messages, and wherein access point devices that receive the first message are configured to measure the receive signal strength of the second message and to send measurement reports to the controller.

31. The system of claim 30, wherein one or more access points are configured to receive from the dual-mode wireless client device a report that contains receive signal strength measurements made by the dual-mode wireless client device on the second messages received by the dual-mode wireless client device on each of the different radio frequency channels, and to forward the report to the controller.

32. The system of claim 25, wherein the other network is a second wireless local area network.

33. The system of claim 25, wherein the other network is a cellular network.