(19)
(11)EP 2 979 478 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
03.06.2020 Bulletin 2020/23

(21)Application number: 14715383.7

(22)Date of filing:  27.03.2014
(51)Int. Cl.: 
H04W 48/16  (2009.01)
H04W 76/10  (2018.01)
(86)International application number:
PCT/GB2014/000122
(87)International publication number:
WO 2014/155044 (02.10.2014 Gazette  2014/40)

(54)

ACCESS POINT SELECTION IN A WIRELESS NETWORK

ZUGRIFFSPUNKTAUSWAHL IN EINEM DRAHTLOSEN NETZWERK

SÉLECTION DE POINT D'ACCÈS DANS UN RÉSEAU SANS FIL


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 28.03.2013 EP 13250043

(43)Date of publication of application:
03.02.2016 Bulletin 2016/05

(73)Proprietor: British Telecommunications public limited company
London EC1A 7AJ (GB)

(72)Inventor:
  • TOWNEND, David, Paul
    London EC1A 7AJ (GB)

(74)Representative: British Telecommunications public limited company Intellectual Property Department 
Ground Floor, Faraday Building 1 Knightrider Street
London EC4V 5BT
London EC4V 5BT (GB)


(56)References cited: : 
EP-A1- 2 424 281
US-A1- 2008 080 388
US-A1- 2008 080 387
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Field of the Invention



    [0001] The present invention relates to wireless network access and in particular to a method of controlling access to a wireless network by controlling the esponses of access points to the presence of client devices.

    Background of the Invention



    [0002] In contrast to traditional wired networks in which computing devices are physically linked via copper or optical cables, wireless networks rely on radio frequency waves transmitted across an air medium.

    [0003] Standards for controlling the behaviour of such example wireless networks include the "Wi-Fi" family of standards currently defined in IEEE 8C2.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n and IEEE 802.11ac protocol.

    [0004] In Wi-Fi networks, the network is created using a device known as an access point (AP). The access point transmits and receives radio frequency signals in specific frequency ranges called channels within the 2.4GHz and 5GHz spectrum or any other supported radio bands. For example, in 802.11g and 2.4GHz 802.11n there are thirteen 20MHz channels with a 5MHz separation, with channel 1 centred at 2412MHz and channel 13 centred at 2472MHz. Devices such as smartphones, personal computers and tablet device which are compatible with the protocol used by the access point can join the network via an authentication and association process.

    [0005] The access point is often paired to a router or modem hardware which is linked to a wide area network such as the Internet. It therefore functions as a bridge between the created wireless network and a wired network such as the Internet or a corporate network.

    [0006] The benefit of a wireless network is that client devices do not have to be attached to the access point by a wire to gain connectivity to a wider area network, furthermore the devices can move while still maintaining connectivity. Due to the nature of the radio frequency signals and antenna properties, the wireless network created by an access point extends into the surrounding area, typically between 50m indoors and 100m outdoors under ideal conditions. Although the signal strength deteriorates as the distance from the access point increases and/or as the number of obstructions increases, so as to reduce these ranges in most cases, this degree of mobility provides flexibility to the client devices.

    [0007] Due to the limited range of each access point and the availability of multiple frequency channels, it is common for many wireless networks to be present in any given area. By selecting different channels, the interference can be minimised. In some cases, each network is a private network and therefore each one will be secured with a pre-shared key security protocol such as Wi-Fi Protected Access version 2 (WPA2). It is also known to create hotspot networks such as the BT Wi-Fi network in which many access points are located across a large area and configured to appear as a single large area wireless network. In this case the access points within the hotspot network do not use any low level authentication since authorisation onto the network is handled in the higher network layers using a protocol such as IEEE 802.1x or a web portal login.

    [0008] Given that a wireless client device will often be within the connectivity range of multiple wireless networks, in order to determine which wireless networks are available, in accordance with the IEEE 802.11 family standards, a wireless device can perform a discovery process by sending a probe request frame on each available channel and wait for responses from any surrounding access points. This is shown in Figure 1. Conventionally and as shown in Figure 2, the access points are configured to respond to any probe messages with capability information and supported data rates. The client device will then process any received responses and present the list of networks to a user for manual selection. Once a network has been selected, then the standard authentication and association procedures are carried out until connectivity to the access point is established.

    [0009] Furthermore the client device may remember access points it has previously connected to and when a known or "preferred" network is detected, it will automatically initiate the authentication and associated process without any action by the user.

    [0010] Where there is a large number of access points, the number of probe request frames and probe responses can be very large. This reduces the bandwidth available for actual data traffic since only one device can be transmitting on a given channel at one time in accordance with the collision avoidance defined in Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA) protocols. This is especially true in densely populated areas, or at large events such as sporting events.

    [0011] EP2424281 describes a wireless communications apparatus which includes a receiving unit configured to receive a response request signal, a transmitting unit configured to transmit a response signal in response to the response request signal, a measuring unit configured to continuously measure received power of the response request signal received by the receiving unit, and a communication control unit configured to cause the transmitting unit to transmit the response signal to a wireless communication apparatus that has transmitted the response request signal if the received power of the response request signal is higher than a threshold value.

    [0012] US20080080388 describes an apparatus and method of an access point supressing probe responses. The method includes the access point receiving a probe request from a client device. The access point determines a quality of a link between the access point and the client device based on the probe request, and the access point communicates to other access points, a client identifier and the quality of the link between the access point and the client device.

    [0013] US20080080387 describes an apparatus and method of an access point determining whether to transmit a response to a client device probe request. The method includes the access point receiving a probe request from a client device. The access point determines a quality of a link between the access point and the client device based on the probe request. The access point sets a delay time for transmitting a probe response to the probe request depending upon the quality of the link.

    Summary of the Invention



    [0014] In one aspect an embodiment provides a method of performing device handover in a wireless access network as set out in claim 1.

    [0015] In one aspect an embodiment provides a method of operating a management device in a network as set out in claim 4.

    [0016] In another aspect, an embodiment provides a wireless access network as set out in claim 7.

    [0017] In a further aspect, an embodiment provides a management server in a wireless access network as set out in claim 10.

    [0018] In a yet further aspect an embodiment provides a computer program comprising instructions that when executed by a management server in a network, control it to perform the method of any of claims 4 to 6.

    Brief Description of the Drawings



    [0019] The invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

    Figure 1 is a schematic diagram of a prior art wireless network system in which a client device sends a probe message to a number of access points in the form of a broadcast message;

    Figure 2 is a schematic diagram of the wireless network system illustrated in Figure 1 in which the access points respond to the probe request frame;

    Figure 3 is a schematic diagram of a wireless network system in accordance with a first embodiment of the present invention in which a client device broadcasts a probe request frame and a number of access points are within range to hear the broadcast, each of which are connected to a management server;

    Figure 4 is a schematic diagram of the wireless network system illustrated in Figure 3 in which only one of the access points responds to the client device's probe request frame;

    Figure 5 is a schematic diagram of the main physical components of an access point illustrated in Figure 3;

    Figure 6 is a schematic diagram of the functional components of the access point illustrated in Figure 5;

    Figure 7 is a schematic diagram of the physical components of the management server illustrated in Figure 3;

    Figure 8 is a schematic diagram of the functional components of the management server illustrated in Figure 7;

    Figure 9 is a flowchart showing the processing of the client device when connecting to an access point in accordance with the first embodiment;

    Figure 10 is a flow chart showing the processing of an access point when a probe response message is received in accordance with the first embodiment;

    Figure 11 is a flowchart showing the processing of the management server when an access point reports a new client device wishing to connect to a network in accordance with the first embodiment;

    Figure 12 is a schematic diagram of example contents of the client database in the management server in accordance with the first embodiment;

    Figure 13 is a schematic diagram of a wireless network system in accordance with a second embodiment of the present invention in which a client device is connected to a wireless access point;

    Figure 14 is a schematic diagram showing the network illustrated in Figure 13 in which the connected client device has changed location and broadcasts a probe request frame when the signal strength to the connected access point becomes too low;

    Figure 15 is a schematic diagram showing the network illustrated in Figure 14 where a single access point responds to the client device's probe request frame;

    Figure 16 is a schematic diagram showing the network illustrated in Figure 15 where the client device has completed a handover process and connected to the responding access point;

    Figure 17 is a schematic diagram showing the functional components of an access point illustrated in Figures 13 to 16;

    Figure 18 is a schematic diagram showing the functional components of a management server illustrated in Figures 13 to 16

    Figure 19 is a flowchart showing the processing of the access point that a client device is connected to before handover in accordance with the second embodiment;

    Figure 20 is a flowchart showing the processing of the management server in the second embodiment;

    Figure 21 is a schematic diagram showing example contents of the client database in the second embodiment;

    Figure 22 is a flowchart showing the processing of other access points in the network which hear the client device's handover probe request frame in the second embodiment;

    Figure 23 is a schematic diagram of a wireless network system in accordance with a third embodiment of the present invention in which a client device is connected to a wireless access point;

    Figure 24 is a schematic diagram showing the functional components of an access point illustrated in Figures 23;

    Figure 25 is a schematic diagram showing the functional components of a management server illustrated in Figures 23;

    Figure 26 is a flowchart showing the processing of the access point currently connected to the client device before handover in the third embodiment;

    Figure 27 is a flowchart showing the processing of the management server upon receipt of a threshold signal from an access point in the third embodiment;

    Figure 28 is a flow chart showing the processing of an access point when a probe response message is received in the third embodiment; and

    Figure 29 is a flowchart showing the processirg of the management server when an access point reports a client device probe request frame in the third embodiment.


    Detailed Description of Preferred Embodiments



    [0020] Figure 3 shows a network system in accordance with an implementation example useful for understanding the invention, The network 1 includes a number of wireless client devices 3 in the vicinity of a number of wireless access points 5 forming part of a hotspot network 7. Laptop 3a, smartphone 3b and tablet computer 3c are connected to some of the access points 5 while smartphone 9 is not yet connected. As is conventional, when a wireless client device 9 is not associated with a particular access point 5, it sends a probe message on the different wireless frequency channels and waits for at least one response. The surrounding wireless access points 5 hear the probe message. However, in this example, instead of immediately responding, they each forward the probe message and signal strength metrics to a network management server 11 via a wired connections.

    [0021] In this example, the access points 5 are linked and form part of the hotspot network 7 which handles user management and authentication, device behaviours and access to a wide area network such as the Internet 13.

    [0022] The management server 11 processes the forwarded probe requests in order to rank the access points and determine the best access point 5 that the client device 9 should connect to. It then selects the highest ranking access point 5 as the most suitable access point 5 for providing the client device 9 with connectivity and instructs only that access point to respond to the client device's 9 probe request. Figure 4 shows a single access point 5 responding to the client device's probe request.

    [0023] In this way, the volume of management data being transmitted in the wireless network is reduced, thereby providing more bandwidth for actual wireless data traffic.

    [0024] The processing of the management server 11 to determine the best access point for connectivity corresponds to the processing that the wireless client device 9 would perform in a conventional system. However by performing the selection at an earlier stage, the bandwidth usage is reduced without any modifications to the wireless client device behaviour. It simply functions as though only a single wireless access point 5 is present in the vicinity.

    Hardware



    [0025] Figure 5 shows the physical components of a wireless access point 5. The wireless access point 5 is responsible for providing a wireless local area network and routing any data traffic between the WLAN and a wired network such a corporate LAN, an Ethernet network or a wide area network such as the Internet 13.

    [0026] The wireless access point 5 therefore contains a wireless network adaptor 21, a wired network adaptor 23, a processor 25 and memory 27.

    [0027] When software instructions stored in the memory 27 are executed on the processor 25, the wireless access point 5 can be regarded as a number of functional units. Figure 6 shows the main functional units of the wireless access point in accordance with the first embodiment.

    [0028] The wireless access point includes a wireless network interface 31, a wired network interface 33 and standard access point functions 35 such as routing. Furthermore the access point 5 contains a modified probe request receiver and responder 37 and network manager interface 39. The operation of these further functions allows for a reduction in the volume of control data transmitted across the wireless network interface and will be explained in more detail later.

    [0029] Figure 7 shows the physical components of the management server 11. The management server 11 contains a wired network adaptor 41, a processor 43, a memory 45 and a data store 47.

    [0030] When data instructions stored in the memory 45 are executed on the processor 43 the management server functionality can be regarded as having a number of functional units. Figure 8 shows the functional units of the management server 11 in accordance with the first embodiment.

    [0031] The functional units of the management server 11 include an access point interface 51, an access point update receiver 53, a response processor 55, a client device database57 and an access point responder 59.

    Processes



    [0032] The processing of the client devices, access points and the network management server will now be described with reference to Figures 9, 10 and 11.

    [0033] Figure 9 is a flowchart showing the operation of the unconnected client device 9. When a client device 9 wishes to connect to a wireless access point 5, in this embodiment it functions in a standard manner. In step s1 a probe request is broadcast via a wireless adaptor. Depending on the capabilities of the wireless adaptor, the probe message is transmitted on both the 2.4GHz and 5GHz frequency channels.

    [0034] After the probe message has been sent, in step s3 the client device waits until a response is received from an access point. Of course in the case there are no access points nearby the process will time out.

    [0035] Once a response is received, in step s5 the standard association and authentication routines take place and in step s7 the device is connected to a wireless device.

    [0036] The operation of the access points will now be described with reference to Figure 10. In step s11 the access point 5 receives a probe request. Instead of immediately responding to the probe message, in step s13 the access point 5 forwards the probe request and an indication of the signal strength between the client device 9 and the access point 5 to the network management server 11.

    [0037] In step s15 a response is received from the management server. In step s17 the access point 5 processes the response. If the response instructs the access point 5 to respond to the probe message then in step s19 the access point 5 responds to the client device 9 in the conventional manner, however, if the instruction is to ignore the probe message, then processing ends without responding to the probe message.

    [0038] The processing of the management server 11 will now be explained with reference to Figure 11. In step s21 a first message from an access point 5 is received and in response to this event, an entry is created in the database for the new client device 9 noting the client's identity, the identity of the access point and a detected signal strength between the client device and access point. In step s23 further access point messages are received, as the messages relate to the same client device, the access point identity and signal strength are added to the client device's entry in the database 57. After a predetermined amount of time has elapsed, in step s25 the management server ranks the access points in accordance with their signal strength. In step s27, the highest ranking access point is instructed to respond to the client device's probe message and the client table is update to reflect this instruction. In step s29, the other access points are instructed to not respond to the probe request since they will not be chosen by the client device.

    [0039] Figure 12 shows a client entry in the database 57. For a given client device 9, the entry stores a number of access point identities, the signal strength and the identity of the selected access point 5. In this way, only the access point which would have been chosen by the client device 9 responds to the probe request. This processing by the access point and management server reduces the traffic requirements on the wireless network space which is typically of lower capacity than the wired network space.

    First embodiment



    [0040] The first example discusses a method of minimising management traffic for dealing with unconnected clients, in particular that caused by responding to probe requests. The second embodiment describes the behaviour of the access points and the management server when dealing with connected client behaviour.

    [0041] Typically, when a client device is in a connected (or associated) state with a particular access point, there is little management traffic generated that is not directly related to user data transfers. Figure 13 shows a client device 109 connected to an access point 105. However, when a connected client device 109 is a mobile device such as a smartphone or tablet computer, if the device moves, the signal strength to the connected access point will change. As shown in Figure 14, if the client device 109 moves away from the access point 105, then the signal strength will decrease and in order to maintain connectivity to the network 107, the client device 109 may need to find a new access point to perform a handover by broadcasting a probe request.

    [0042] Different devices generally have different threshold signal strengths for initiating a handover. This may be due to hardware capabilities of the adaptor card or aerial of the client device, a minimum bandwidth or data rate required or a manufacturer defined setting for "roaming aggressiveness".

    [0043] In the first embodiment, the access points regularly log the signal strength of their connected client devices to determine when a device first sends probe requests as this signal strength is the threshold value for that device. Rather than attempting to send this threshold value to all neighbouring access points, this signal strength data is sent to the management server 111 which acts as a central database for the other access points to consult before responding to the client device's probe request. This processing reduces the amount of management traffic which improves the bandwidth available for data transfers.

    [0044] Having retrieved the threshold value, each access point can determine whether the signal strength is above the threshold and hence decide whether or not to respond to the probe request.

    [0045] As shown in Figure 15, although there are three other access points 105 able to hear the client device's probe request, after the processing of the access point according to the second embodiment, only one access point 105 having a greater signal strength than the determined threshold replies to the client device's probe request.

    [0046] The client device 109 processes any probe responses in a conventional manner in order to select a new access point to maintain connectivity. Figure 16 shows the client device 109 connected to a new access point 105.

    [0047] Figure 17 is a schematic diagram showing the functional components of an access point 105 in the first embodiment.

    [0048] The wireless access point 105 includes a wireless network interface 131, a wired network interface 133 and standard access point functions 135 such as routing. Furthermore the access point 105 contains a signal strength monitor 137 and network manager interface 139.

    [0049] Figure 18 is a schematic diagram showing the functional components of a management server 111 in a first embodiment.

    [0050] The functional units of the management server 111 include an access point interface 151, an access point update receiver 153, a client device database 155 and an interface for other network management functions 157.

    [0051] Figure 19 shows the processing of the access point 105 which has a connected client device 109 in the first embodiment.

    [0052] In step s101 the access point 105 is connected to a client device and measures the signal strength between itself and the client device. At step s103 a test is performed to see if the connected client device 109 has started sending probe requests, if it has not, then processing returns to step s101 so that the access point can continue to monitor the signal strength. The determination of the signal strength of the client is based on received packets. Each packet has a received signal strength at which it was measured. The measurement is an average of packet signal strength over a time frame. In this embodiment the time frame is 100ms which is the same default interval at which regular AP management traffic is sent.

    [0053] If the access point finds that the connected client device 109 has started sending probe requests because the signal strength is deteriorating, then in step s105 the access point 105 logs the measured signal strength as the threshold signal strength for the connected client 109.

    [0054] Finally the threshold value is sent as a message to the management server 111 in step s107 and processing ends.

    [0055] Figure 20 shows the processing performed by the management server 111.

    [0056] In step s111 a threshold message is received from an access point 105 and in step s113 the management server 111 updates the client database 155 with this new value and makes it available to other access points 105 in the network 107.

    [0057] Figure 21 shows example contents of the client database 155 in the second embodiment. As can be seen, each of the four connected devices has a different threshold signal strength due to variations in the performance and capabilities of the wireless adaptors.

    [0058] Figure 22 shows the processing performed by other access points 105 which are candidates for client device 109 handover.

    [0059] In step s121 the access point receives a probe request from a client device. In response the access point determines the signal strength to the client device in step s123 and then in step s125 consults the management server for the threshold level for the client device.

    [0060] The retrieved threshold value is then compared to the determined signal strength in step s127 and if the signal strength is higher than the threshold then in step s129 the access point responds to the client device's probe request so that it can be considered for the handover. However, if signal strength is lower than the threshold, then in step s131 the access point ignores the probe request since it will not be considered for the handover - the client device would not consider handing over to a lower signal strength access point.

    [0061] In the first embodiment the amount of management traffic transmitted over a wireless network for a handover routine when a client device is reduced because the access points can choose to ignore client device probe requests.

    Second embodiment



    [0062] In the first embodiment, the access points selectively respond to probe requests by comparing the measured signal strength for a handover client device against a threshold. This reduces the management traffic thereby allowing more data traffic bandwidth for connected clients.

    [0063] In a further improvement, the functionality of the management server in the first example is applied to the first embodiment to handle client device handover. The connected access point monitors the signal strength to determine a threshold for that particular device and forwards it to the management server.

    [0064] The operation of other access points and the management server differs from the second embodiment in that the management server is also responsible for selecting the next access point for the client device. The access points which receive the probe request forward them to the management server instead of retrieving the threshold value. The management server then compares each access point's signal strength against the threshold, to filter out unsuitable candidates for handover. Then it ranks the candidate access points and notifies the top ranking access point to reply to the probe request while instructing the other access points to ignore the probe request.

    [0065] With this operation, the management server can ensure that only access points with higher signal strengths than the threshold to the client are considered as a possible handover candidates. Then the management server reduces the management traffic sent over the wireless networks by deciding which access point handles the handover procedure and sending all signalling over the wired network. The wired network traffic is also reduced due to a decrease in message flows.

    [0066] Figure 23 is a schematic diagram of a wireless network system in accordance with a second embodiment of the present invention in which client devices 203 can connect wireless access points 205 within a hotspot network 207 to provide connection to a wide area network such as the Internet 213. Whilst the overall impression is the same as in the first embodiment, the processing of the wireless access points 205 and the interaction with a management server 211 is different. An exemplary client device 209 is shown in a state where it has broadcast for access points 205 and a single access point 205 has replied.

    [0067] Unlike in the first embodiment, the access points 203 and 209 do not determine for themselves whether access points 205 are suitable. In the third embodiment this functionality is provided by the management server 211.

    [0068] Compared with the first embodiment, the access points 205 are simpler and the management server 211 is more complex.

    [0069] Figure 24 is a schematic diagram showing the functional components of an access point 205 illustrated in Figures 23.

    [0070] The wireless access point 205 includes a wireless network interface 221, a wired network interface 223 and standard access point functions 225 such as routing. Furthermore the access point 5 contains a modified probe request receiver and responder 227 and network manager interface 229 as per the first embodiment and a signal strength monitor 231 as in the second embodiment. The operation of these further functions allows for a reduction in the volume of control data transmitted across the wireless network interface and will be explained in more detail later.

    [0071] Figure 25 is a schematic diagram showing the functional components of a management server 211 illustrated in Figures 23;

    [0072] The functional units of the management server 7 include an access point interface 251, an access point update receiver 253, a response processor 255, a client device database2 57 and an access point responder 259.

    [0073] Figure 26 is a flowchart showing the processing of the access point currently connected to the client device before handover.

    [0074] In step s201 the access point is connected to a client device and measures the signal strength between itself and the client device. At step s203 a test is performed to see if the connected client device has started sending probe requests, if it has not, then processing returns to step s201 so that the access point can continue to monitor the signal strength. The determination of the signal strength of the client is based on received packets. Each packet has a received signal strength at which it was measured. The measurement is an average of packet signal strength over a time frame. In this embodiment the time frame is 100ms which is the same default interval at which regular AP management traffic is sent.

    [0075] If the access point finds that the connected client device has started sending probe requests because the signal strength is deteriorating, then in step s205 the access point logs the measured signal strength as the threshold signal strength for the connected client.

    [0076] Finally the threshold value is sent as a message to the management server 211 in step s207 and processing ends.

    [0077] Figure 27 is a flowchart showing the processing of the management server upon receipt of a threshold signal from an access point;

    [0078] In step s211 a threshold message is received from an access point and in step s213 the management server updates the client database with this new value and makes it available to other access points in the network.

    [0079] Figure 28 is a flow chart showing the processing of an access point when a probe response message is received.

    [0080] In step s221 the access point receives a probe request and instead of immediately responding to the probe message, in step s223 the access point forwards the probe request and an indication of the signal strength between the client device and the access point to the network management server 211.

    [0081] In step s225 a response is received from the management server 211. In step s227 the access point 205 processes the response. If the response instructs the access point 205 to respond to the probe message then in step s229 the access point responds to the client device in the conventional manner, however, if the instruction is to ignore the probe message, then processing ends without responding to the probe message.

    [0082] Figure 29 is a flowchart showing the processing of the management server 211 when an access point 205 reports a client device probe request frame.

    [0083] In step s231 a first message from an access point is received and in response to this event, an entry is created in the database for the new client device noting the client's identity, the identity of the access point and a detected signal strength between the client device and access point. In step s233 further access point messages are received, as the messages relate to the same client device, the access point identity and signal strength are added to the client device's entry in the database. After a predetermined amount of time has elapsed, in step s235 the management server 211 retrieves the threshold signal for the client device 209. It then compares each received access point message against the threshold and in step s237 removes any signals which are below the threshold for the device since the client device will not connect to any devices with a lower strength. After this initial cull, in step s239 the management server ranks the access points in accordance with their signal strength. In step s241, the highest ranking access point is instructed to respond to the client device's probe message and the client table is updated to reflect this instruction. In step s243, the other access points are instructed to not respond to the probe request since they will not be chosen by the client device.

    [0084] In the second embodiment, the amount of wireless management data during handover can be reduced because the management server 211 first filters out weak signals and then finds the strongest access point for a client device. Most of the communications are over conventional fixed line networks so this removes a source of interference and traffic from the wireless network.

    Alternatives and Modifications



    [0085] In the first example, unconnected client devices can join a wireless network after the processing of the access points and management server selects the most suitable access point. If the unconnected client device has been previously connected to the network then it will have an entry in the management server and in particular it may have a threshold value. Therefore in an alternative, the management server includes an addition step of comparing each received message from the access points against the threshold to pre-filter and reduce the list of access points that need to be ranked.

    [0086] In the above embodiments, the example systems assume that the client device can connect to any of the available access points and therefore the access point simply connects to the strongest signal access point at any given moment in time. Such a scenario is common in hotspot networks in which the access point low level security is often disabled since the security aspects of the network are addressed at a much higher network level.

    [0087] However it is more common that the access points are secured access points requiring authentication using a protocol such as Wi-Fi Protected Access version 2 (WPA2) and therefore if the wireless client does not have the authentication key, then even if the access point provides the strongest signal strength the client will not be able to connect.

    [0088] In a modification to the above embodiments, the management server maintains a list of each client's preferred networks and ensures that the preferred networks are instructed to respond in preference to other stronger but protected networks which the client device will not be able to connect to.

    [0089] In some of the embodiments the management server is arranged to select the access point having the strongest signal strength, whilst other access points are instructed to ignore the probe request. This behaviour minimises the amount of management traffic on the network.

    [0090] In an alternative to the behaviour of the management server in the first and third embodiments, the management server is configured to instruct more than one of the top ranking access points, e.g the top two access points to respond to the probe request. The client then makes the final decision regarding which access point it connects to based on local criteria. This is especially important for mobile client devices which will be moving and therefore the signal strengths may have changed from the sending of the requests to the actual association. In any case, weak signals which the client would never connect to are filtered out. E.g. all those with a signal strength below -70dBm. The threshold value could be obtained from the connected client behaviour when it starts to hunt for a new AP.

    [0091] In the embodiments, the access points send their measured signal strength to the management server which then ranks the access points. However, other criteria in addition to the signal strength may be utilised. In an alternative, the access points send other metrics in addition to signal strength so the management server can use different selection criteria to determine "best" access point. E.g. present load so closest AP might not be the best one. Such metrics such as network load, interference etc., can be obtained from the ratified IEEE 802.11k standard.

    [0092] In the embodiments, the access points forward probe requests, however, it will be appreciated by those skilled in the art that only the information and parameters are important. Therefore the access points could also send probe request summary messages in an alternative.

    [0093] In a further modification, the management server can be used for access control by preventing specific sets of access points or even all access points from responding to the probe requests issuing from a particular set of client devices.

    Additional Implementation Details



    [0094] The systems and methods of the above embodiments may be implemented in a computer system (in particular in computer hardware or in computer software or a combination of both) in addition or as an alternative to the structural components and user interactions described. The term "computer system" includes the hardware, software and data storage devices for embodying a system or carrying out a method according to the above described embodiments. For example, a computer system may comprise a central processing unit (CPU), input means, output means and data storage. Alternatively, a microprocessor, plural microprocessors, microcontroller, plural microcontrollers, ASIC and/or FPGA may be employed. The computer system may have a monitor to provide a visual output display. The data storage may comprise RAM, hard disk drive (HDD) or other computer readable media, including portable media and optical media. The computer system may include a plurality of computing devices connected by a network and able to communicate with each other over that network.

    [0095] The methods of the above embodiments may be provided as computer programs or as computer program products or computer-readable media carrying a computer program which is arranged, when run/executed on a computer, to perform the method(s) described above.

    [0096] The term "computer readable media" includes, without limitation, any medium or media which can be read and accessed directly by a computer or computer system. The media can include, but are not limited to, magnetic storage media such as floppy discs, hard disc storage media and magnetic tape; optical storage media such as optical discs or CD-ROMs; electrical storage media such as memory, including RAM, ROM and flash memory; and hybrids and combinations of the above such as magnetic/optical storage media.

    [0097] It will be appreciated that the above described embodiments are purely illustrative and are not limiting on the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art upon reading the present application.


    Claims

    1. A method of performing device handover in a wireless access network having a plurality of wireless access points (205) for providing connectivity to a plurality of mobile devices (209) wherein each mobile device (209) is operable to connect to different ones of the wireless access points (205) in dependence on their location within the wireless access network, the wireless access points (205) being connected to a management server (211) for exchange of control data between sets of wireless access points (205) in relation to the mobile devices (209), the method comprising:

    a first wireless access point (205) having a connected mobile device (209):

    monitoring (s203) for probe requests issued by the connected mobile device, indicative that the mobile device is seeking to handover to another of the plurality of wireless access points;

    determining (s205) the signal strength of a wireless link between said first wireless access point and the mobile device;

    sending (s207) a message to said management server (211), the message containing the determined signal strength and an identifier for the connected mobile device (209),

    the management server (211):

    receiving (s211) the message from the first wireless access point;

    storing (s213) the identifier for the mobile device and the determined signal strength in a data store, wherein the determined signal strength is stored as a threshold signal strength for handover for that mobile device,

    at least one second wireless access point (205):

    receiving (s221) a probe request from said mobile device;

    sending (s223) a second message to the management server, including details of the probe request, an identifier for the mobile device and an observed signal strength,

    wherein the management server (211) further performs the steps of:

    receiving (s231) the second message from the at least one second wireless access point;

    retrieving (s235) the threshold signal strength associated with the mobile device from the data store;

    determining (s237) whether the observed signal strength between the at least one second wireless access point and the mobile device is above the stored threshold signal strength associated with said mobile device;

    if the observed signal strength is above the threshold signal strength, then instructing (s241) the second wireless access point to respond to the probe request,

    if the observed signal strength is below the threshold signal strength, then instructing (s243) the second wireless access point to ignore the probe request.


     
    2. A method according to claim 1, further comprising the management server:

    receiving (s233) messages from a plurality of second access points in the network;

    comparing (s237) each of the second access points against the stored threshold signal strength associated with the mobile device; and

    instructing (s241) a subset from the plurality of second wireless access points to respond to the mobile device's probe request.


     
    3. A method according to claim 1 or claim 2, further comprising determining access permissions and network load of the at least one second wireless access point.
     
    4. A method of operating a management device (211) in a network having a plurality of wireless access points (205) and a plurality of mobile devices (209) in device handover, comprising:

    receiving from a first wireless access point (205) connected to a mobile device (209), a message containing a signal strength value of a wireless link between said first wireless access point (205) and the mobile device (209) when the mobile device (209) issued connection requests for handover and an identifier for the connected mobile device (209);

    storing the identifier for the mobile device (209) and the signal strength in a data store (257), wherein the signal strength is stored as a threshold signal strength for handover associated with that mobile device (209),

    receiving from at least one second wireless access point (205) that has received a probe request from said mobile device (209), a second message, including details of the probe request, an identifier for the mobile device (209) and an observed signal strength,

    retrieving the threshold signal strength associated with the mobile device (209) from the data store (257);

    determining whether the observed signal strength between the second wireless access point (205) and the mobile device (209) is above the threshold signal strength for said mobile device (209);

    if the observed signal strength is above the threshold signal strength, then instructing the second wireless access point (205) to respond to the probe request,

    if the observed signal strength is below the threshold signal strength, then instructing the second wireless access point (205) to ignore the probe request.


     
    5. A method according to claim 4, further comprising:

    receiving messages from a plurality of second access points (205) in the network;

    comparing each of the second access points (205) against the threshold signal strength associated with the mobile device; and

    instructing a subset from the plurality of second wireless access points (205) to respond to the probe request.


     
    6. A method according to claim 4 or claim 5, further comprising determining access permissions and network load of the at least one second wireless access point (205).
     
    7. A wireless access network having a plurality of wireless access points (205) for providing connectivity to a plurality of mobile devices (209) wherein each mobile device (209) is operable to connect to different ones of the wireless access points (205) in dependence on their location within the wireless access network, the wireless access points (205) being connected to a management server (211) for exchange of control data between sets of wireless access points (205) in relation to the mobile devices (209), comprising:

    a first wireless access point (205) having a connected mobile device (209), comprising:

    means (227) for monitoring for probe requests issued by the connected mobile device (209), indicative that the mobile device (209) is seeking to handover to another of the plurality of wireless access points (205);

    means (231) for determining the signal strength of a wireless link between said first wireless access point (205) and the mobile device (209);

    means (229) for sending a message to said management server (211), the message containing the determined signal strength and an identifier for the connected mobile device (209),

    the management server (211) comprising:

    means (251) for receiving the message from the first wireless access point;

    a data store (257) for storing an identifier for the mobile device and a determined signal strength in a data store;

    means (253) for storing the identifier for the mobile device (209) and the determined signal strength in the data store (257), wherein the determined signal strength is stored as a threshold signal strength for handover for that mobile device (209),

    at least one second wireless access point (205) comprising:

    means (227) for receiving a probe request from said mobile device (209);

    means (229) for sending a second message to the management server (211), including details of the probe request, an identifier for the mobile device (209) and an observed signal strength,

    wherein the management server (211) further comprises:

    means (251) for receiving the second message from the at least one second wireless access point;

    means (255) for retrieving the threshold signal strength associated with the mobile device (209) from the data store (257);

    means (255) for determining whether the observed signal strength between the at least one second wireless access point (205) and the mobile device (209) is above the stored threshold signal strength associated with said mobile device (209); and

    control means (255, 259)operable to:

    instruct the second wireless access point (209) to respond to the probe request if the observed signal strength is above the threshold signal strength, and

    instruct the second wireless access point (209) to ignore the probe request if the observed signal strength is below the threshold signal strength.


     
    8. A method according to claim 7, wherein the management server (211) is further operable to:

    receive messages from a plurality of second access points (205) in the network;

    compare each of the second access points (205) against the stored threshold signal strength associated with the mobile device (209); and

    instruct a subset from the plurality of second wireless access points (205) to respond to the mobile device's probe request.


     
    9. A method according to claim 7 or claim 8, further comprising means for determining access permissions and network load of the at least one second wireless access point (205).
     
    10. A management server (211) for managing device handover in a network having a plurality of wireless access points (205) and a plurality of mobile devices (209) comprising:

    means (251) for receiving from a first wireless access point connected to a mobile device, a message containing a signal strength value of a wireless link between said first wireless access point and the mobile device when the mobile device issued connection requests for handover and an identifier for the connected mobile device;

    a data store (257);

    means (253) for storing the identifier for the mobile device and the signal strength in a data store, wherein the signal strength is stored as a threshold signal strength for handover associated with that mobile device;

    means (251) for receiving from at least one second wireless access point that has received a probe request from said mobile wireless communication device, a second message, including details of the probe request, an identifier for the mobile device and an observed signal strength,

    means (255) for retrieving the threshold signal strength associated with the mobile device from the data store (257);

    means (255) for determining whether the observed signal strength between the second wireless access point and the mobile device is above the threshold signal strength for said mobile device;

    control (255, 259) means operable to:

    instruct the second wireless access point to respond to the probe request if the observed signal strength is above the threshold signal strength, and

    instruct the second wireless access point to ignore the probe request if the observed signal strength is below the threshold signal strength.


     
    11. A management server (211) according to claim 10, further operable to:

    receive messages from a plurality of second access points in the network;

    compare each of the second access points against the stored threshold signal strength associated with the mobile device; and

    instruct a subset from the plurality of second wireless access points to respond to the mobile device's probe request.


     
    12. A management server (211) according to claim 10 or claim 11, further comprising means for determining access permissions and network load of the at least one second wireless access point.
     
    13. A computer program comprising instructions that when executed by a management device in a network, control it to perform the method of any of claims 4 to 6.
     


    Ansprüche

    1. Verfahren zum Durchführen von Einrichtungsübergabe in einem Funkzugangsnetz mit einer Vielzahl von Funkzugangspunkten (205) zum Bereitstellen von Konnektivität an eine Vielzahl von Mobileinrichtungen (209), wobei jede Mobileinrichtung (209) betriebsfähig ist, sich abhängig von ihrem Standort innerhalb des Funkzugangsnetzes mit verschiedenen der Funkzugangspunkte (205) zu verbinden, wobei die Funkzugangspunkte (205) zum Austausch von Steuerdaten zwischen Gruppen von Funkzugangspunkten (205) in Bezug auf die Mobileinrichtungen (209) mit einem Verwaltungsserver (211) verbunden sind, wobei das Verfahren Folgendes umfasst:
    durch einen ersten Funkzugangspunkt (205) mit einer verbundenen Mobileinrichtung (209):

    Überwachen (s203) auf von der verbundenen Mobileinrichtung ausgegebene Sondierungsanfragen, die anzeigen, dass die Mobileinrichtung eine Übergabe an einen anderen der Vielzahl von Funkzugangspunkten anstrebt,

    Bestimmen (s205) der Signalstärke einer Funkverbindung zwischen dem ersten Funkzugangspunkt und der Mobileinrichtung,

    Senden (s207) einer Nachricht an den Verwaltungsserver (211), wobei die Nachricht die bestimmte Signalstärke und eine Kennung für die verbundene Mobileinrichtung (209) enthält,

    durch den Verwaltungsserver (211):

    Empfangen (s211) der Nachricht vom ersten Funkzugangspunkt,

    Speichern (s213) der Kennung für die Mobileinrichtung und der bestimmten Signalstärke in einem Datenspeicher, wobei die bestimmte Signalstärke als Grenzsignalstärke für Übergabe für diese Mobileinrichtung gespeichert wird,

    durch mindestens einen zweiten Funkzugangspunkt (205):

    Empfangen (s221) einer Sondierungsanfrage von der Mobileinrichtung,

    Senden (s223) einer zweiten Nachricht an den Verwaltungsserver, die Einzelheiten der Sondierungsanfrage, eine Kennung für die Mobileinrichtung und eine beobachtete Signalstärke beinhaltet,

    wobei der Verwaltungsserver (211) ferner folgende Schritte durchführt:

    Empfangen (s231) der zweiten Nachricht vom mindestens einen zweiten Funkzugangspunkt,

    Abrufen (s235) der der Mobileinrichtung zugehörigen Grenzsignalstärke aus dem Datenspeicher,

    Bestimmen (s237), ob die beobachtete Signalstärke zwischen dem mindestens einen zweiten Funkzugangspunkt und der Mobileinrichtung oberhalb der der Mobileinrichtung zugehörigen Grenzsignalstärke liegt,

    falls die beobachtete Signalstärke oberhalb der Grenzsignalstärke liegt, Anweisen (s241) des zweiten Funkzugangspunkts, auf die Sondierungsanfrage zu antworten,

    falls die beobachtete Signalstärke unterhalb der Grenzsignalstärke liegt, Anweisen (s243) des zweiten Funkzugangspunkts, die Sondierungsanfrage zu ignorieren.


     
    2. Verfahren nach Anspruch 1, ferner umfassend durch den Verwaltungsserver:

    Empfangen (s233) von Nachrichten von einer Vielzahl zweiter Zugangspunkte im Netzwerk,

    Vergleichen (s237) jedes der zweiten Zugangspunkte mit der der Mobileinrichtung zugehörigen gespeicherten Grenzsignalstärke und

    Anweisen (s241) einer Teilgruppe aus der Vielzahl zweiter Funkzugangspunkte, auf die Sondierungsanfrage der Mobileinrichtung zu antworten.


     
    3. Verfahren nach Anspruch 1 oder Anspruch 2, ferner umfassend Bestimmen von Zugriffsberechtigungen und Netzwerklast des mindestens einen zweiten Funkzugangspunkts.
     
    4. Verfahren zum Betreiben einer Verwaltungseinrichtung (211) in einem Netzwerk mit einer Vielzahl von Funkzugangspunkten (205) und einer Vielzahl von Mobileinrichtungen (209) in Einrichtungsübergabe, umfassend:

    Empfangen, von einem mit einer Mobileinrichtung (209) verbundenen ersten Funkzugangspunkt (205), einer Nachricht, die einen Signalstärkewert einer Funkverbindung zwischen dem ersten Funkzugangspunkt (205) und der Mobileinrichtung (209), als die Mobileinrichtung (209) Verbindungsanfragen für eine Übergabe ausgegeben hat, und eine Kennung für die verbundene Mobileinrichtung (209) enthält,

    Speichern der Kennung für die Mobileinrichtung (209) und der Signalstärke in einem Datenspeicher (257), wobei die Signalstärke als eine dieser Mobileinrichtung (209) zugehörige Grenzsignalstärke für Übergabe gespeichert wird,

    Empfangen, von mindestens einem zweiten Funkzugangspunkt (205), der eine Sondierungsanfrage von der Mobileinrichtung (209) empfangen hat, einer zweiten Nachricht, die Einzelheiten der Sondierungsanfrage, eine Kennung für die Mobileinrichtung (209) und eine beobachtete Signalstärke beinhaltet,

    Abrufen der der Mobileinrichtung (209) zugehörigen Grenzsignalstärke aus dem Datenspeicher (257), Bestimmen, ob die beobachtete Signalstärke zwischen dem zweiten Funkzugangspunkt (205) und der Mobileinrichtung (209) oberhalb der der Mobileinrichtung (209) zugehörigen Grenzsignalstärke liegt,

    falls die beobachtete Signalstärke oberhalb der Grenzsignalstärke liegt, Anweisen des zweiten Funkzugangspunkts (205), auf die Sondierungsanfrage zu antworten,

    falls die beobachtete Signalstärke unterhalb der Grenzsignalstärke liegt, Anweisen des zweiten Funkzugangspunkts (205), die Sondierungsanfrage zu ignorieren.


     
    5. Verfahren nach Anspruch 4, ferner umfassend:

    Empfangen von Nachrichten von einer Vielzahl zweiter Funkzugangspunkte (205) im Netzwerk,

    Vergleichen jedes der zweiten Zugangspunkte (205) mit der der Mobileinrichtung zugehörigen Grenzsignalstärke und Anweisen einer Teilgruppe aus der Vielzahl zweiter Funkzugangspunkte (205), auf die Sondierungsanfrage zu antworten.


     
    6. Verfahren nach Anspruch 4 oder Anspruch 5, ferner umfassend Bestimmen von Zugriffsberechtigungen und Netzwerklast des mindestens einen zweiten Funkzugangspunkts (205).
     
    7. Funkzugangsnetz mit einer Vielzahl von Funkzugangspunkten (205) zum Bereitstellen von Konnektivität an eine Vielzahl von Mobileinrichtungen (209), wobei jede Mobileinrichtung (209) betriebsfähig ist, sich abhängig von ihrem Standort innerhalb des Funkzugangsnetzes mit verschiedenen der Funkzugangspunkte (205) zu verbinden, wobei die Funkzugangspunkte (205) zum Austausch von Steuerdaten zwischen Gruppen von Funkzugangspunkten (205) in Bezug auf die Mobileinrichtungen (209) mit einem Verwaltungsserver (211) verbunden sind, umfassend:
    einen ersten Funkzugangspunkt (205) mit einer verbundenen Mobileinrichtung (209), umfassend:

    Mittel (227) zum Überwachen auf von der verbundenen Mobileinrichtung (209) ausgegebene Sondierungsanfragen, die anzeigen, dass die Mobileinrichtung (209) eine Übergabe an einen anderen der Vielzahl von Funkzugangspunkten (205) anstrebt,

    Mittel (231) zum Bestimmen der Signalstärke einer Funkverbindung zwischen dem ersten Funkzugangspunkt (205) und der Mobileinrichtung (209),

    Mittel (229) zum Senden einer Nachricht an den Verwaltungsserver (211), wobei die Nachricht die bestimmte Signalstärke und eine Kennung für die verbundene Mobileinrichtung (209) enthält,

    wobei der Verwaltungsserver (211) Folgendes umfasst:

    Mittel (251) zum Empfangen der Nachricht vom ersten Funkzugangspunkt,

    einen Datenspeicher (257) zum Speichern einer Kennung für die Mobileinrichtung und einer bestimmten Signalstärke in einem Datenspeicher,

    Mittel (253) zum Speichern der Kennung für die Mobileinrichtung (209) und der bestimmten Signalstärke im Datenspeicher (257), wobei die bestimmte Signalstärke als Grenzsignalstärke für Übergabe für diese Mobileinrichtung (209) gespeichert wird,

    mindestens einen zweiten Funkzugangspunkt (205), der Folgendes umfasst:

    Mittel (227) zum Empfangen einer Sondierungsanfrage von der Mobileinrichtung (209),

    Mittel (229) zum Senden einer zweiten Nachricht an den Verwaltungsserver (211), die Einzelheiten der Sondierungsanfrage, eine Kennung für die Mobileinrichtung (209) und eine beobachtete Signalstärke beinhaltet,

    wobei der Verwaltungsserver (211) ferner Folgendes umfasst:

    Mittel (251) zum Empfangen der zweiten Nachricht vom mindestens einen zweiten Funkzugangspunkt,

    Mittel (255) zum Abrufen der der Mobileinrichtung (209) zugehörigen Grenzsignalstärke aus dem Datenspeicher (257),

    Mittel (255) zum Bestimmen, ob die beobachtete Signalstärke zwischen dem mindestens einen zweiten Funkzugangspunkt (205) und der Mobileinrichtung (209) oberhalb der der Mobileinrichtung (209) zugehörigen Grenzsignalstärke liegt, und

    Steuermittel (255, 259), die betriebsfähig sind, um:

    den zweiten Funkzugangspunkt (209) anzuweisen, auf die Sondierungsanfrage zu antworten, falls die beobachtete Signalstärke oberhalb der Grenzsignalstärke liegt, und

    den zweiten Funkzugangspunkt (209) anzuweisen, die Sondierungsanfrage zu ignorieren, falls die beobachtete Signalstärke unterhalb der Grenzsignalstärke liegt.


     
    8. Verfahren nach Anspruch 7, wobei der Verwaltungsserver (211) ferner betriebsfähig ist, um:

    Nachrichten von einer Vielzahl zweiter Funkzugangspunkte (205) im Netzwerk zu empfangen,

    jeden der zweiten Zugangspunkte (205) mit der der Mobileinrichtung (209) zugehörigen gespeicherten Grenzsignalstärke zu vergleichen und

    eine Teilgruppe aus der Vielzahl zweiter Funkzugangspunkte (205) anzuweisen, auf die Sondierungsfrage der Mobileinrichtung zu antworten.


     
    9. Verfahren nach Anspruch 7 oder Anspruch 8, ferner umfassend Mittel zum Bestimmen von Zugriffsberechtigungen und Netzwerklast des mindestens einen zweiten Funkzugangspunkts (205).
     
    10. Verwaltungsserver (211) zum Verwalten von Einrichtungsübergabe in einem Netzwerk mit einer Vielzahl von Funkzugangspunkten (205) und einer Vielzahl von Mobileinrichtungen (209), umfassend:

    Mittel (251) zum Empfangen, von einem mit einer Mobileinrichtung verbundenen ersten Funkzugangspunkt, einer Nachricht, die einen Signalstärkewert einer Funkverbindung zwischen dem ersten Funkzugangspunkt und der Mobileinrichtung, als die Mobileinrichtung Verbindungsanfragen für eine Übergabe ausgegeben hat, und eine Kennung für die verbundene Mobileinrichtung enthält, einen Datenspeicher (257),

    Mittel (253) zum Speichern der Kennung für die Mobileinrichtung und der Signalstärke in einem Datenspeicher, wobei die Signalstärke als eine dieser Mobileinrichtung zugehörige Grenzsignalstärke für Übergabe gespeichert wird,

    Mittel (251) zum Empfangen, von mindestens einem zweiten Funkzugangspunkt, der eine Sondierungsanfrage von der mobilen Funkkommunikationseinrichtung empfangen hat, einer zweiten Nachricht, die Einzelheiten der Sondierungsanfrage, eine Kennung für die Mobileinrichtung und eine beobachtete Signalstärke beinhaltet,

    Mittel (255) zum Abrufen der der Mobileinrichtung zugehörigen Grenzsignalstärke aus dem Datenspeicher (257),

    Mittel (255) zum Bestimmen, ob die beobachtete Signalstärke zwischen dem zweiten Funkzugangspunkt und der Mobileinrichtung oberhalb der Grenzsignalstärke für die Mobileinrichtung liegt,

    Steuer- (255, 259) Mittel, die betriebsfähig sind, um:

    den zweiten Funkzugangspunkt anzuweisen, auf die Sondierungsanfrage zu antworten, falls die beobachtete Signalstärke oberhalb der Grenzsignalstärke liegt, und

    den zweiten Funkzugangspunkt anzuweisen, die Sondierungsanfrage zu ignorieren, falls die beobachtete Signalstärke unterhalb der Grenzsignalstärke liegt.


     
    11. Verwaltungsserver (211) nach Anspruch 10, ferner betriebsfähig, um:

    Nachrichten von einer Vielzahl zweiter Zugangspunkte im Netzwerk zu empfangen,

    jeden der zweiten Zugangspunkte mit der der Mobileinrichtung zugehörigen Grenzsignalstärke zu vergleichen und

    eine Teilgruppe aus der Vielzahl zweiter Funkzugangspunkte anzuweisen, auf die Sondierungsanfrage der Mobileinrichtung zu antworten.


     
    12. Verwaltungsserver (211) nach Anspruch 10 oder Anspruch 11, ferner umfassend Mittel zum Bestimmen von Zugriffsberechtigungen und Netzwerklast des mindestens einen zweiten Funkzugangspunkts.
     
    13. Computerprogramm, das Anweisungen umfasst, die bei Ausführung durch eine Verwaltungseinrichtung in einem Netzwerk diese steuern, um das Verfahren nach einem der Ansprüche 4 bis 6 durchzuführen.
     


    Revendications

    1. Procédé de réalisation d'un transfert de dispositif dans un réseau d'accès sans fil doté d'une pluralité de points (205) d'accès sans fil servant à assurer une connectivité à une pluralité de dispositifs mobiles (209), chaque dispositif mobile (209) étant exploitable pour se connecter à différents points parmi les points (205) d'accès sans fil en fonction de leur emplacement au sein du réseau d'accès sans fil, les points (205) d'accès sans fil étant connectés à un serveur (211) de gestion pour un échange de données de commande entre des ensembles de points (205) d'accès sans fil par rapport aux dispositifs mobiles (209), le procédé comportant les étapes lors desquelles :

    un premier point (205) d'accès sans fil doté d'un dispositif mobile (209) connecté :

    surveille (s203) l'apparition de demandes de sonde émises par le dispositif mobile connecté, indiquant que le dispositif mobile recherche un transfert vers un autre point de la pluralité de points d'accès sans fil ;

    détermine (s205) l'intensité de signal d'une liaison sans fil entre ledit premier point d'accès sans fil et le dispositif mobile ;

    envoie (s207) un message audit serveur (211) de gestion, le message contenant l'intensité de signal déterminée et un identifiant relatif au dispositif mobile (209) connecté,

    le serveur (211) de gestion :

    reçoit (s211) le message en provenance du premier point d'accès sans fil ;

    stocke (s213) l'identifiant relatif au dispositif mobile et l'intensité de signal déterminée dans une mémoire de données, l'intensité de signal déterminée étant stockée en tant qu'intensité seuil de signal en vue d'un transfert pour le dispositif mobile considéré, au moins un second point (205) d'accès sans fil :

    reçoit (s221) une demande de sonde en provenance dudit dispositif mobile ;

    envoie (s223) un second message au serveur de gestion, comprenant des détails de la demande de sonde, un identifiant relatif au dispositif mobile et une intensité de signal observée,

    le serveur (211) de gestion effectuant en outre les étapes consistant à :

    recevoir (s231) le second message en provenance du ou des seconds points d'accès sans fil ;

    extraire (s235) l'intensité seuil de signal associée au dispositif mobile de la mémoire de données ;

    déterminer (s237) si l'intensité de signal observée entre le ou les seconds points d'accès sans fil et le dispositif mobile est supérieure à l'intensité seuil de signal stockée associée audit dispositif mobile ;

    si l'intensité de signal observée est supérieure à l'intensité seuil de signal, donner (s241) comme instruction au second point d'accès sans fil de réagir à la demande de sonde,

    si l'intensité de signal observée est inférieure à l'intensité seuil de signal, donner (s243) comme instruction au second point d'accès sans fil d'ignorer la demande de sonde.


     
    2. Procédé selon la revendication 1, comportant en outre les étapes lors desquelles le serveur de gestion :

    reçoit (s233) des messages en provenance d'une pluralité de seconds points d'accès dans le réseau ;

    compare (s237) chacun des seconds points d'accès vis-à-vis de l'intensité seuil de signal stockée associée au dispositif mobile ; et

    donne (s241) comme instruction à un sous-ensemble de la pluralité de seconds points d'accès sans fil de réagir à la demande de sonde du dispositif mobile.


     
    3. Procédé selon la revendication 1 ou la revendication 2, comportant en outre la détermination de permissions d'accès et d'une charge de réseau du ou des seconds points d'accès sans fil.
     
    4. Procédé d'exploitation d'un dispositif (211) de gestion dans un réseau doté d'une pluralité de points (205) d'accès sans fil et d'une pluralité de dispositifs mobiles (209) lors d'un transfert de dispositif, comportant les étapes consistant à :

    recevoir en provenance d'un premier point (205) d'accès sans fil connecté à un dispositif mobile (209), un message contenant une valeur d'intensité de signal d'une liaison sans fil entre ledit premier point (205) d'accès sans fil et le dispositif mobile (209) lorsque le dispositif mobile (209) a émis des demandes de connexion en vue d'un transfert et un identifiant relatif au dispositif mobile (209) connecté ;

    stocker l'identifiant relatif au dispositif mobile (209) et l'intensité de signal dans une mémoire (257) de données, l'intensité de signal étant stockée en tant qu'intensité seuil de signal pour transfert associée au dispositif mobile (209) considéré,

    recevoir en provenance d'au moins un second point (205) d'accès sans fil ayant reçu une demande de sonde en provenance dudit dispositif mobile (209), un second message, comprenant des détails de la demande de sonde, un identifiant relatif au dispositif mobile (209) et une intensité de signal observée,

    extraire l'intensité seuil de signal associée au dispositif mobile (209) de la mémoire (257) de données ;

    déterminer si l'intensité de signal observée entre le second point (205) d'accès sans fil et le dispositif mobile (209) est supérieure à l'intensité seuil de signal pour ledit dispositif mobile (209) ;

    si l'intensité de signal observée est supérieure à l'intensité seuil de signal, donner comme instruction au second point (205) d'accès sans fil de réagir à la demande de sonde,

    si l'intensité de signal observée est inférieure à l'intensité seuil de signal, donner comme instruction au second point (205) d'accès sans fil d'ignorer la demande de sonde.


     
    5. Procédé selon la revendication 4, comportant en outre les étapes consistant à :

    recevoir des messages en provenance d'une pluralité de seconds points (205) d'accès dans le réseau ;

    comparer chacun des seconds points (205) d'accès vis-à-vis de l'intensité seuil de signal associée au dispositif mobile ; et

    donner comme instruction à un sous-ensemble de la pluralité de seconds points (205) d'accès sans fil de réagir à la demande de sonde.


     
    6. Procédé selon la revendication 4 ou la revendication 5, comportant en outre la détermination de permissions d'accès et d'une charge de réseau du ou des seconds points (205) d'accès sans fil.
     
    7. Réseau d'accès sans fil doté d'une pluralité de points (205) d'accès sans fil servant à assurer une connectivité à une pluralité de dispositifs mobiles (209), chaque dispositif mobile (209) étant exploitable pour se connecter à différents points parmi les points (205) d'accès sans fil en fonction de leur emplacement au sein du réseau d'accès sans fil, les points (205) d'accès sans fil étant connectés à un serveur (211) de gestion pour un échange de données de commande entre des ensembles de points (205) d'accès sans fil par rapport aux dispositifs mobiles (209), comportant :

    un premier point (205) d'accès sans fil doté d'un dispositif mobile (209) connecté, comportant :

    un moyen (227) servant à surveiller l'apparition de demandes de sonde émises par le dispositif mobile (209) connecté, indiquant que le dispositif mobile (209) recherche un transfert vers un autre point de la pluralité de points (205) d'accès sans fil ;

    un moyen (231) servant à déterminer l'intensité de signal d'une liaison sans fil entre ledit premier point (205) d'accès sans fil et le dispositif mobile (209) ;

    un moyen (229) servant à envoyer un message audit serveur (211) de gestion, le message contenant l'intensité de signal déterminée et un identifiant relatif au dispositif mobile (209) connecté,

    le serveur (211) de gestion comportant :

    un moyen (251) servant à recevoir le message en provenance du premier point d'accès sans fil ;

    une mémoire (257) de données servant à stocker un identifiant relatif au dispositif mobile et une intensité de signal déterminée dans une mémoire de données ;

    un moyen (253) servant à stocker l'identifiant relatif au dispositif mobile (209) et l'intensité de signal déterminée dans la mémoire (257) de données, l'intensité de signal déterminée étant stockée en tant qu'intensité seuil de signal en vue d'un transfert pour le dispositif mobile (209) considéré,

    au moins un second point (205) d'accès sans fil comportant :

    un moyen (227) servant à recevoir une demande de sonde en provenance dudit dispositif mobile (209) ;

    un moyen (229) servant à envoyer un second message au serveur (211) de gestion, comprenant des détails de la demande de sonde, un identifiant relatif au dispositif mobile (209) et une intensité de signal observée,

    le serveur (211) de gestion comportant en outre :

    un moyen (251) servant à recevoir le second message en provenance du ou des seconds points d'accès sans fil ;

    un moyen (255) servant à extraire l'intensité seuil de signal associée au dispositif mobile (209) de la mémoire (257) de données ;

    un moyen (255) servant à déterminer si l'intensité de signal observée entre le ou les seconds points (205) d'accès sans fil et le dispositif mobile (209) est supérieure à l'intensité seuil de signal stockée associée audit dispositif mobile (209) ; et

    des moyens (255, 259) de commande exploitables pour :

    donner comme instruction au second point (209) d'accès sans fil de réagir à la demande de sonde si l'intensité de signal observée est supérieure à l'intensité seuil de signal, et

    donner comme instruction au second point (209) d'accès sans fil d'ignorer la demande de sonde si l'intensité de signal observée est inférieure à l'intensité seuil de signal.


     
    8. Procédé selon la revendication 7, le serveur (211) de gestion étant en outre exploitable pour :

    recevoir des messages en provenance d'une pluralité de seconds points (205) d'accès dans le réseau ;

    comparer chacun des seconds points (205) d'accès vis-à-vis de l'intensité seuil de signal stockée associée au dispositif mobile (209) ; et

    donner comme instruction à un sous-ensemble de la pluralité de seconds points (205) d'accès sans fil de réagir à la demande de sonde du dispositif mobile.


     
    9. Procédé selon la revendication 7 ou la revendication 8, comportant en outre un moyen servant à déterminer des permissions d'accès et une charge de réseau du ou des seconds points (205) d'accès sans fil.
     
    10. Serveur (211) de gestion destiné à gérer un transfert de dispositif dans un réseau doté d'une pluralité de points (205) d'accès sans fil et d'une pluralité de dispositifs mobiles (209), comportant :

    un moyen (251) servant à recevoir, en provenance d'un premier point d'accès sans fil connecté à un dispositif mobile, un message contenant une valeur d'intensité de signal d'une liaison sans fil entre ledit premier point d'accès sans fil et le dispositif mobile lorsque le dispositif mobile a émis des demandes de connexion en vue d'un transfert et un identifiant relatif au dispositif mobile connecté ;

    une mémoire (257) de données ;

    un moyen (253) servant à stocker l'identifiant relatif au dispositif mobile et l'intensité de signal dans une mémoire de données, l'intensité de signal étant stockée en tant qu'intensité seuil de signal pour transfert associée au dispositif mobile considéré ;

    un moyen (251) servant à recevoir, en provenance d'au moins un second point d'accès sans fil ayant reçu une demande de sonde en provenance dudit dispositif mobile de communication sans fil, un second message, comprenant des détails de la demande de sonde, un identifiant relatif au dispositif mobile et une intensité de signal observée,

    un moyen (255) servant à extraire l'intensité seuil de signal associée au dispositif mobile de la mémoire (257) de données ;

    un moyen (255) servant à déterminer si l'intensité de signal observée entre le second point d'accès sans fil et le dispositif mobile est supérieure à l'intensité seuil de signal pour ledit dispositif mobile ;

    des moyens (255, 259) de commande exploitables pour :

    donner comme instruction au second point d'accès sans fil de réagir à la demande de sonde si l'intensité de signal observée est supérieure à l'intensité seuil de signal, et

    donner comme instruction au second point d'accès sans fil d'ignorer la demande de sonde si l'intensité de signal observée est inférieure à l'intensité seuil de signal.


     
    11. Serveur (211) de gestion selon la revendication 10, exploitable en outre pour :

    recevoir des messages en provenance d'une pluralité de seconds points d'accès dans le réseau ;

    comparer chacun des seconds points d'accès vis-à-vis de l'intensité seuil de signal stockée associée au dispositif mobile ; et

    donner comme instruction à un sous-ensemble de la pluralité de seconds points d'accès sans fil de réagir à la demande de sonde du dispositif mobile.


     
    12. Serveur (211) de gestion selon la revendication 10 ou la revendication 11, comportant en outre un moyen servant à déterminer des permissions d'accès et une charge de réseau du ou des seconds points d'accès sans fil.
     
    13. Programme informatique comportant des instructions qui, lorsqu'elles sont exécutées par un dispositif de gestion dans un réseau, le commandent de façon à réaliser le procédé selon l'une quelconque des revendications 4 à 6.
     




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    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description