Abstract:
A wireless area network terminal receives an unsolicited broadcast from a network to all wireless area network terminals in a predetermined category. The unsolicited broadcast includes an indicator that an emergency alert is waiting. The indicator triggers a request to be sent from the terminal to the network to allow the alert to be downloaded to the terminal.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. national stage of International Application No. PCT/GB2007/050683, filed Nov. 12, 2007 and claims the benefit thereof. The International Application claims the benefits of United Kingdom Application No. 0622454.7 filed on Nov. 13, 2006 and United Kingdom Application No. 0706120.3 filed on Mar. 29, 2007, all three applications are incorporated by reference herein in their entirety. 
       BACKGROUND 
       [0002]    Described below is a method of providing an emergency alert to a wireless local area network terminal, in particular for the IEEE  802  family of wireless communications systems. 
         [0003]    In the event of an emergency situation arising, various regional entities wish to notify users using any available communications systems at their disposal. It is likely that legislation will mandate this requirement for any wireless communication system, regardless of the application used, such as voice over internet protocol (VoIP), Text, Video, FAX, Email and Instant Messenger (IM). The wireless technology underpinning the communications media is not of concern to the entities mentioned above. 
         [0004]    The IEEE 802 family of wireless communications systems, typically characterized by IEEE 802.11, are architecturally based on short range wireless communications and include, in order of increasing radio range coverage, IEEE 802.15 (Personal Area Networks), IEEE 802.11 (Local Area Networks), IEEE 802.16 (Wireless Metropolitan Area Networks, also referred to as WiMAX) and IEEE 802.22 (Wireless Regional Area Networks). Furthermore, there are other non-802 type networks to which the method applies, such as high performance radio wireless local area network (HIPERLAN) or high performance metropolitan area network (HIPERMAN) and reference to a wireless area network includes any of these. 
       SUMMARY 
       [0005]    In accordance with a first aspect, a method of providing an emergency alert to a wireless area network terminal includes sending an unsolicited broadcast from a network to all wireless area network terminals in a predetermined category; wherein the unsolicited broadcast includes an indicator that an emergency alert is waiting; and wherein the indicator triggers a request to be sent from the terminal to the network to allow the alert to be downloaded to the terminal. 
         [0006]    In wireless area networks of any of the types or categories mentioned above, the passive network edge elements have to signal to a user in a potentially unsolicited manner, whereas in a cellular system an allocated user channel would just be interrupted by an emergency alert message. According to the method, the wireless terminal can transmit a separate request back to the network in a two stage handshake process, allowing the alert to be transmitted. 
         [0007]    The trigger may be an alert to the user, requesting that they initiate a connection to the network. 
         [0008]    The request is then sent to the network on the connection that has been initiated. 
         [0009]    Alternatively, the trigger initiates a connection to the network from the terminal automatically, in response to receipt of the unsolicited broadcast containing the indicator. 
         [0010]    The indicator may be transmitted from a network with which the terminal is operating, but alternatively, the indicator is transmitted from a neighboring network within radio range of the terminal. 
         [0011]    The predetermined category may be one of terminal type, or geographical range, or membership of a closed user group. 
         [0012]    The indicator may be an additional field in a broadcast, multicast, or unicast transmission. 
         [0013]    Alternatively, the indicator is an additional field in a paging message. 
         [0014]    Typically, the wireless local area network is an IEEE 802 type network, although the method is equally applicable to other types of wireless local area network, such as high performance radio wireless local area network (HIPERLAN) or high performance metropolitan area network (HIPERMAN). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other aspects and advantages a method of providing an emergency alert to a wireless local area network terminal will become more apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
           [0016]      FIG. 1  is an iconic drawing of a typical deployment scenario in which the method may be applied; 
           [0017]      FIG. 2  is a message flow sequence diagram illustrating an example of the method applied in the scenario of  FIG. 1 , for certain wireless user devices; 
           [0018]      FIG. 3  is an example of an emergency alert message frame sent by the network in the method; 
           [0019]      FIG. 4  is an example of a request message sent by a user device in the method; 
           [0020]      FIG. 5  is an example of a response message sent by a user device in the method, in reply to the message of  FIG. 2 ; 
           [0021]      FIG. 6  is an example of an emergency alert message frame, for a closed user group; 
           [0022]      FIG. 7  is an example of a message flow sequence in the scenario of  FIG. 1 , for a wireless device, which is aware of the emergency alert; 
           [0023]      FIG. 8  is a paging emergency alert message frame. 
           [0024]      FIG. 9  is an alternative scenario to that shown in  FIG. 1 ; and, 
           [0025]      FIG. 10  is an implementation specific example of an emergency alert message frame for IEEE 802.11. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
         [0027]    A problem for wireless area network communication systems wishing to provide an emergency alert is that passive network edge elements, such as an IEEE 802.11 access point, have to signal to the user in a potentially unsolicited manner, which goes against the normal mode of operation in these types of systems. If a user has established a data session, then the network can interrupt this session, but if a user does not have a data session in operation, the network edge element (e.g. an IEEE 802.11 access point) may not have any knowledge of the user&#39;s existence within a hotspot. 
         [0028]    Even with an established data session, the alert may be of a different form (e.g. text message), to that of the current user session (e.g. a VoIP call). Since the IEEE 802 family of systems use packet based connections, the emergency alert message is able to share any currently allocated radio resources. In other words a dedicated channel for emergency alert transmission is not required. A further feature is to allow simultaneous transmission of the alert within the current user session (e.g. the aforementioned VoIP call) with another form of transmission (e.g. text message or ringing alert). 
         [0029]    Where there is no established data session, the network needs to prompt the user to request receipt of the emergency alert. A prompting mechanism is suggested as this saves valuable radio resource, as it is expected that a cascade of messages will shortly follow, requesting more information. If the emergency alert were to be broadcast in an unsolicited manner, this may consume all available radio resources within that area. Upon reception of a centralized emergency alert notification (e.g. from a network entity), the network edge element (e.g. IEEE 802.11 access point) then broadcasts a signalling frame (e.g. an IEEE 802.11 beacon) with a special flag set to indicate that an emergency alert is ready to be delivered. This message typically uses a broadcast type address, but a multicast, or unicast message could be used instead. 
         [0030]    The user device then initiates an algorithm to enable reception of this alert. The reception of the alert within the user device may trigger a prompt to the user, which can be of any type, such as a ring tone, video display wakeup, or vibration etc., to notify the user to react. Alternatively, the flag may cause the user device to set up a connection automatically. 
         [0031]      FIG. 1  illustrates a typical deployment scenario for implementation of this method. The examples are described with respect to IEEE 802 type networks, but are equally applicable to other wireless personal, local, metropolitan, or regional area networks and references to wireless local area network (WLAN) in this description encompasses all such wireless area networks. A network  1  sends an emergency alert  2  to a network edge device  3 , which relays this as an initial hotspot alert message  4 . This alert is received at a number of wireless devices in the vicinity, including non-IEEE 802 wireless devices within radio reception range. 
         [0032]    In the example of  FIG. 1  the emergency alert message  2 , relayed as a hotspot alert message  4 , sent from the network  1  via the edge device  3 , is broadcast to all devices  5 ,  6 ,  7 ,  8  within radio reception range. Of the devices within range, three are wireless enabled devices  5 ,  6 ,  7  and one is a cellular device  8 . As the edge device  3  is sending communication for a specific type of wireless system, the cellular only device  8  does not respond to the broadcast. The wireless enabled device  7  is a multimode device including a cellular receiver, together with an IEEE  802  wireless receiver, so the device can receive the IEEE 802 wireless emergency alerts and be prompted to respond. The wireless device  5  has not been in recent communication with network edge device  3 , so that it is not registered with this edge device; and the wireless device  6  is already connected to the network edge device  3  and is currently communicating with some other traffic, so that the device is currently registered with the network edge device. On receipt of the hotspot alert message frame with an emergency alert flag  12 , the user device  6  connects to receive the alert  13  without requesting any further information from the network  1 . 
         [0033]    The alert can be set to prompt a response from all devices within radio reception range that are the correct type of WLAN devices, or else user specific criteria are applied, as described below. Furthermore, in some circumstances an initial alert triggers the user device into requesting more information, either manually, or autonomously. The message flow sequence is as shown in  FIG. 2 . The network  1  sends the emergency alert  2  to the network edge device  3 . The network edge device  3  sends a hotspot alert message  4  to all devices within radio range. Wireless devices  5 ,  6  may choose to send back a request message  9  to the network edge device  3  for further information and they receive a response  10 , which is broadcast to all devices  5 ,  6 ,  7 ,  8  within radio range. 
         [0034]    The emergency alert message  2  may be a single field  12  within the hotspot alert message  4  as shown in  FIG. 3 , to indicate that an alert is present within the network. The hotspot alert message  4  is typically made up of several fields and includes a header  11 , the alert field  12 , and the remainder of the bits in the message  4  are a reserved field  15 . In  FIG. 4 , an example of a request frame message  9  transmitted to the network is shown. The request  9  includes a header  11 , query identifier  16 , request for alert information  17  and a reserved field  18 . The request, once received by the network edge device, then enables the user device to be provided with more information, if available, through a response  10  to the network edge device. An example of a response message  10  is shown in  FIG. 5 , in which a header  11 , broadcast flag, or query identifier  19  and alert information  20  are provided. The network edge device returns the further information, if any is available, in the response. The response from the network edge device  3 , is transmitted in a broadcast fashion, so that any other terminals  6 ,  7 ,  8  in radio range can receive the same information. Alternatively, multicast, or unicast transmission can be used to limit the number of user devices which are allowed to receive the transmission. 
         [0035]    As a minimum, receipt of the emergency alert field prompts the receiving device to connect to receive the emergency alert information content, either through user action, or an automated sequence. However, in order to adapt the broadcast to a specific user group, some of the reserved field can be allocated as identifiers for the user group (as shown in  FIG. 6 , where a user group identifier  21  is provided and the remaining bits are a reserved field  22 ), rather than simply relying on all users within radio reception range responding. An indication of the emergency alert is transmitted in this way, to save radio resource bandwidth. In the scenario of  FIG. 1 , the user device  7  is already connected and working, so on receipt of the broadcast hotspot alert message frame  4  with the emergency alert flag  12 , the user device  7  determines from the user group identifier field  21  that the user device is not within the specified user group and continues its normal working. If the device did fall within the required user group, the device could simply divert resources to request receipt of the alert. 
         [0036]      FIG. 7  illustrates a typical message exchange with user device  7  in the scenario of  FIG. 1 . Initially the network  1  issues an emergency alert message  2 , which is then relayed in a hotspot alert  4  from the network edge device  3 . In this scenario, the indication may be ignored  14  by the multi-mode device  7  on the basis that a similar alert has already been received on the cellular receiver within the multi-mode device, from a suitable cellular transmitter. If an indication has not been received on the cellular receiver, then the multi-mode device  7  can process the alert  2  in a similar manner to wireless devices  5 ,  6 , as described with respect to  FIG. 2 , depending on whether, or not the multi-mode device  7  is transmitting data over the IEEE 802 wireless interface at the time. 
         [0037]    A further option is to allow simultaneous transmission of the alert on the current user session, rather than requiring an interruption. The user may then perceive the alert as a pop up window in a current media session, or alternatively a text message, email or ringing alert 
         [0038]    The Query ID field  16 ,  19  in the request and response messages  9 ,  10  is a token generated by the wireless device  5 , which allows the network edge device  3  to respond to this device directly, if there is a requirement to do so. The response message  10  may be sent in a unicast mode to the specific device  5  which requested the alert information using the Query ID value, or the response may be transmitted in a broadcast mode to all IEEE 802 wireless devices  5 ,  6 ,  7  or in a multicast mode, to a specific subset of IEEE 802 wireless devices,  5 ,  6  defined by the Query ID value. 
         [0039]    Within an IEEE 802 system which uses paging to awaken an idle wireless device, operation is very similar to the above method, with the distinction that the alert notification of  FIG. 3  is appended to a paging update, so that when the wireless device awakens for the paging update, it then can respond to the alert notification. It is known to have paging updates extend the IEEE 802.11 beacon with a paging group indicator field. User devices which wish to enter an idle mode, add themselves to the current paging group in operation within the local hotspot. The user device then powers down its IEEE 802.11 radio receiver, which has been synchronized previously with the paging beacons from the IEEE 802.11 access point. This then means that the user device only has to awaken for each paging beacon to remain in contact with the network. This paging group indicator field may be further extended as shown in  FIG. 8  to include the network emergency alert field. The paging update  23  includes an element identifier  24 , a length field  25 , a paging group identifier  26 , a paging interval field  27 , digital pulse interval modulation (DPIM) count field  28  and network emergency alert  29 . The advantage of this mechanism is that IEEE 802.11 devices in idle mode, would wake upon reception of this modified paging message and then proceed to request the emergency alert information as described above. 
         [0040]    As mentioned above, a further extension to the method is that under certain circumstances, the emergency alert system is restricted to a closed user group. This may occur, for example, when wishing to restrict an emergency alert to a limited geographical area, e.g. in the event of a chemical spillage; or when wishing to restrict the emergency alert to specific user types, such as police or army, for security reasons (e.g. to avoid civilian panic). This restriction is applied as shown in  FIG. 6 , where the header  11  and alert field  12  are augmented by the user group identifier  21  and the remaining fields  22  are reserved. The initial hotspot alert message  4 , as shown in  FIG. 3 , is modified by the addition of the user group identifier  21 . Although the network edge device  3  transmits this message as an emergency alert, only IEEE 802 wireless devices recognizing the user group identifier will respond to the message. Security of these messages is achieved through known methods such as Diffie-Hellman key exchange; use of well known session keys; or through the use of certificates within the user group devices. 
         [0041]    In a further example, as shown in  FIG. 9 , the IEEE 802 wireless device  5  issues the request  9  for more information to the initial hotspot transmitter  3 , but there is nothing to stop another network edge device  30  from transmitting the response  10 . This may be a useful feature, if the device  5  is in motion, particularly within a moving vehicle where emergency alerts may be highly desirable. Network signalling  31  takes place between the two network edge devices  3 ,  30  which relays the query ID  16  and request for alert information  17  from device  5 , in a similar format to that of the request  9 . 
         [0042]      FIG. 10  illustrates a specific implementation for IEEE 802.11. Within an IEEE 802.11 system (Wireless Local Area Network), one example of the implementation details of the hotspot alert is as follows. Bit  0  (B 0 ) provides a quality of service (QoS) map, bit  1  (B 1 ) is for an expected bandwidth request, bit  2  (B 2 ) is reserved for emergency service only, bit  3  (B 3 ) of the interworking capabilities field is used for the network emergency alert notification (the interworking capabilities field is typically transmitted within an IEEE 802.11 beacon frame), and bits  4  to  15  (B 4  to B 15 ) are reserved. Upon receipt of this alert, an IEEE 802.11 terminal can then issue a probe request message conforming to the format as shown above in  FIG. 4  for further information. 
         [0043]    The system also includes permanent or removable storage, such as magnetic and optical discs, RAM, ROM, etc. on which the process and data structures of the present invention can be stored and distributed. The processes can also be distributed via, for example, downloading over a network such as the Internet. The system can output the results to a display device, printer, readily accessible memory or another computer on a network. 
         [0044]    A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).