Methods and apparatus for locating a mobile device in a sleep mode
Apparatus and methods are provided for locating a mobile device in a sleep mode. A method comprises transmitting a beacon signal configured to initiate transmission of a response signal from a mobile device in a sleep mode. The mobile device is associated with a first wireless access device on a first communication channel. The method further comprises receiving the response signal from the mobile device on the first communication channel and determining the physical location of the mobile device based on the response signal.
1. A method for locating a mobile device in an IEEE 802.11 wireless local area network (WLAN), the mobile device being initially in a sleep mode, the mobile device being associated with a first WLAN access device on a first WLAN channel, the method comprising:
configuring at least one other WLAN access device operable on other respective WLAN channels for receiving data on the first WLAN channel by having the at least one other WLAN access device send a Clear To Send message to mobile devices being served by that at least one other WLAN access device on the other respective WLAN channels and switching the at least one other WLAN access device to operate on the first WLAN channel;
waking the mobile device from the sleep mode by transmitting a beacon that falsely indicates that there is pending data for the mobile device, wherein the mobile device transmits a beacon response frame on the first WLAN channel in response to waking;
receiving the beacon response frame by the first and at least one other WLAN access devices; and
determining a location of the mobile device based on at least one respective characteristic for the beacon response frame received at the first and at least one other WLAN access devices,
wherein falsely indicating pending data comprises transmitting a beacon frame from the first wireless access device, the beacon frame including a traffic information map, wherein the traffic information map associated with the mobile device is configured to falsely notify the mobile device of data awaiting delivery to the mobile device.
2. The method of claim 1 , further comprising an initial step of identifying a particular mobile device to be located to a WLAN switch, whereupon the WLAN switch will determine the first WLAN access device and first WLAN channel associated with that mobile device.
3. The method of claim 1 , further comprising returning the mobile device to the sleep mode after the mobile device transmits the frame.
4. The method of claim 1 , wherein the at least one other WLAN access device is an access device neighboring the first WLAN access device unless the at least one WLAN access device is supporting a type of communication that should not be interrupted.
5. The method of claim 1 , wherein the at least one respective characteristic is an identifier of the mobile device and at least one of a respective signal strength of the received frame at each access device and a respective time of arrival of the received frame at each access device.
6. A wireless switch for an IEEE 802.11 wireless local area network (WLAN) having a plurality of wireless access devices, wherein a mobile device is associated with a first WLAN access device of the plurality of wireless access devices on a first WLAN channel, the wireless switch comprising:
a communication module, the communication module being configured to communicate with the plurality of wireless access devices;
a database, the database being configured to maintain physical location information for each wireless access device of the plurality of wireless access devices; and
a processor coupled to the communication module and the database, wherein the processor is configured to:
configure at least one other WLAN access device other than the first WLAN access device operable on other respective WLAN channels other than the first WLAN channel for receiving data on the first WLAN channel by having the at least one other WLAN access device send a Clear To Send message to mobile devices being served by that at least one other WLAN access device on the other respective WLAN channels and switching the at least one other WLAN access device to operate on the first WLAN channel;
wake the mobile device from the sleep mode by initiating the transmission of a beacon that falsely indicates that there is pending data for the mobile device, wherein the mobile device transmits a beacon response frame on the first WLAN channel in response to waking to be received by the first and at least one other WLAN access devices; and
determine a physical location of the mobile device based at least in part on a physical location of the first wireless access device, a physical location of the second wireless access device, and at least one respective characteristic for the beacon response frame received at the first and at least one other WLAN access devices,
wherein falsely indicating pending data comprises transmitting a beacon frame from the first wireless access device, the beacon frame including a traffic information map, wherein the traffic information map associated with the mobile device is configured to falsely notify the mobile device of data awaiting delivery to the mobile device.