EP2888905A2 - Procédé de commutation rapide, système de commutation rapide et client dans un système de communication sans fil - Google Patents

Procédé de commutation rapide, système de commutation rapide et client dans un système de communication sans fil

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Publication number
EP2888905A2
EP2888905A2 EP13756374.8A EP13756374A EP2888905A2 EP 2888905 A2 EP2888905 A2 EP 2888905A2 EP 13756374 A EP13756374 A EP 13756374A EP 2888905 A2 EP2888905 A2 EP 2888905A2
Authority
EP
European Patent Office
Prior art keywords
client
current
target
candidate aps
virtual
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP13756374.8A
Other languages
German (de)
English (en)
Inventor
Mattias Lampe
Ji Feng Tian
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Mobility GmbH
Original Assignee
Siemens AG
Siemens Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN201210305958.2A external-priority patent/CN103634860B/zh
Application filed by Siemens AG, Siemens Corp filed Critical Siemens AG
Publication of EP2888905A2 publication Critical patent/EP2888905A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00835—Determination of neighbour cell lists
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/0085—Hand-off measurements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/08—Reselecting an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Definitions

  • the present invention relates to the field of wireless communi - cations, and particularly, to a fast switching method, a fast switching system, a client and an access point (AP) in a wire- less communication system of a rail transit system.
  • Fig. 1 a plurality of access points (APs) are set on the road (for clarity, Fig. 1 shows only three APs : AP0, API and AP2) , with every two adjacent APs being separated by an interval of a specific distance to ensure that no coverage dead zone exists.
  • a client is located at the train side and can communicate with an AP which covers it. By means of the communication connection, a client on the train can communicate with a server on the road side through the access point, and the AP is referred to as the current AP of the client.
  • the client When the train moves, the client will depart from the coverage area of the current AP and interrupt the communication with the current AP, and at this moment, the client needs to switch to another AP (referred to as the target AP) in order to ensure normal communication. Therefore, the switching mechanism is critical to guarantee reliable and uninterrupted communication between the client and the AP.
  • a probe request to the target AP and the target AP returns a probe response to the client; and the client sends an association request to the target AP and the tar- get AP returns an association response to the client.
  • the client sends an authentication request to the target AP, and the target AP returns an authentication response to the client; and if the cli- ent passes the authentication, then the client establishes a communication connection with the target AP, and the target AP becomes the current AP of the client.
  • both the APs and the client are using directional antennas, the application of which is very common in the rail transit system.
  • the use of directional antennas usually causes the strength of the received signal to suddenly weaken when the client passes by the current AP.
  • the current AP of the client is API
  • the client when the client moves from right to left to point B, the strength of the signal emitted by API suddenly weakens.
  • the client must try to switch to another AP (i.e. the target AP; in Fig. 1, the target AP is AP2) in order to maintain communication with the server.
  • the time required for the client to switch from the current AP to the target AP is as short as possible.
  • the switching shown in Fig. 1 needs to spend a time of more than 100 ms ; that is to say, data transmission is interrupted in the time of 100 ms .
  • an interruption as long as 100 ms is unbearable whether it is passenger information or train control information. Therefore, a fast switching mechanism is required to reduce the switching time .
  • the process of a client switching from one AP to another AP can usually be divided into two stages: the switching-deciding stage and the connection-establishment stage.
  • the existing fast switching mechanisms are generally achieved by reducing the switching-deciding time or reducing the connection- establishment time.
  • a fast switching method in the prior art is as shown in Fig. 3, where API is the current AP of the client, and the client starts switching when the client moves to point A which is close to API.
  • API is the current AP of the client
  • the client starts switching when the client moves to point A which is close to API.
  • the strength of the signal of API received by the client remains strong and is greater than a switching threshold
  • the switching starts.
  • combining the method with the background scanning method in the prior art the client in the idle state continuously scans all the chan- nels to collect information about the candidate APs) can help reduce the switching-deciding time.
  • the client starts switching when the strength of the signal emitted by the current AP is still strong, more overlapping coverage areas are required between the current AP and the target AP, so to ensure that the switching point can correctly receive signals from the target AP, which will increase the number of APs. If the original distance between the APs remains, then the strength of the signal from the target AP may be relatively weak and this will seriously affect the switching process. In the worst case, a probe request, an association request and an authentication request transmitted by the client are all lost on the target AP side, and therefore multiple retransmissions are required, which will increase the connection-establishment time, thereby offsetting the advantages obtained by the switching-deciding stage. Moreo- ver, after the connection with the current AP is disconnected, this method cannot reduce the time of connection establishment with the target AP .
  • the authentication will take a lot of time. If an authentication server is used, the time spent will be more than 100 ms .
  • Another fast switching method in the prior art is the pre-authentication method: in the IEEE802.11x standard, the client can perform a pre-authentication operation with the au- thentication server before the switching starts, thereby reducing the connection-establishment time.
  • this pre- authentication method can only reduce the authentication operation time with the authentication server, but can neither reduce the time of other operations during connection establish- ment nor reduce the switching-deciding time.
  • the main object of the present invention is to provide a fast switching method, a fast switching system, a client and an AP in a wireless communication system, thereby effectively reducing the switching time of the client from the current AP to the target AP .
  • one embodiment of a fast switching method in a wireless communication system according to the present invention comprises: when a client decides to switch, said client establishes, via its current access point (AP) , virtual links with candidate
  • said virtual links including a communication link between said client and said current AP and communication links between said current AP and said candidate APs; said client sends, via said virtual links, a probe request to said candidate APs and receives probe responses of said candidate APs ; said client selects, according to the probe responses of said candidate APs, a target AP from said candidate APs; said client sends, via said virtual link, an association request to said target AP and receives an association response of said target AP; and when said client starts switching, said client terminates the communication with said current AP and switches to said target AP.
  • Another embodiment of a fast switching method in a wireless communication system comprises : when a client decides to switch, a current access point (AP) of said client is used to establish virtual links between said client and candidate APs, said virtual links including a communication link between said client and said current AP and communication links between said current AP and said candidate APs; said current AP receives a probe request sent, via said virtual links, by said client to said candidate APs and forwards the probe request to said candidate APs, and receives probe responses sent, via said virtual links, by said candidate APs to said client and forwards the probe responses to said client; said current AP receives an association request sent, via said virtual link, by said client to said target AP and forwards the association request to said target AP, and receives an association response sent, via said virtual link, by said target AP to said client and forwards the association response to said client ; and when said client starts switching, said current AP terminates the communication with said client.
  • a current access point (AP) of said client is
  • Yet another embodiment of a fast switching method in a wireless communication system comprises : when a client decides to switch, candidate access points (APs) establish, via a current AP of said client, virtual links with said client, said virtual links including communication links between said candidate APs and said current AP and a communication link between said current AP and said client; said candidate APs receive, via said virtual links, a probe re- quest of said client and send probe responses to said client; and said candidate APs receive, via said virtual links, an association request of said client and send association responses to said client.
  • candidate access points APs
  • One embodiment of a fast switching system in a wireless communication system comprises a client and a plurality of wireless access points (APs) , said client is used for establishing, via its current access point (AP) , virtual links with candidate APs when it decides to switch, said virtual links including a communication link between said client and said current AP and communication links between said current AP and said candidate APs; sending, via said virtual links, a probe request to said candidate APs and receiving probe responses of said candidate APs; selecting, ac- cording to the probe responses of said candidate APs, a target AP from said candidate APs; sending, via said virtual link, an association request to said target AP and receiving an association response of said target AP; and terminating the communica- tion with said current AP and switching to said target AP when switching is started; said current AP is used for establishing virtual links between said client and candidate APs when said client decides to switch; receiving a probe request sent, via said virtual links, by said client to
  • One embodiment of a fast switching client in a wireless communication system comprises: a first virtual link establishment module for establishing, via a current AP of said client, virtual links between said client and candidate APs when said client decides to switch, said virtual links including a communication link between said client and said current AP and communication links between said current AP and said candidate APs; a first probe module for sending, via said virtual links, a probe request to said candidate APs and receiving probe responses of said candidate APs; a selection module for selecting, according to the probe responses of said candidate APs, a target AP from said candidate APs; a first association module for sending, via said virtual link, an association request to said target AP and receiving an association response of said target AP; and a first switching module for terminating the communication with said current AP and switching to said target AP when said client starts switching.
  • an access point (AP) in a wireless communication system comprises: a second virtual link establishment module for establishing virtual links between a client and candidate APs when said cli- ent decides to switch, said virtual links including a communication link between said client and said AP and communication links between said AP and said candidate APs;
  • a second probe module for receiving a probe request sent, via said virtual links, by said client to said candidate APs and forwarding the probe request to said candidate APs, and receiving probe responses sent, via said virtual links, by said candidate APs to said client and forwarding the probe responses to said client;
  • a second association module for receiving an association request sent, via said virtual link, by said client to said target AP and forwarding the association request to said target AP, and receiving an association response sent, via said virtual link, by said target AP to said client and forwarding the association response to said client; and a second switching module for terminating the communication with said client when said client starts switching.
  • Another embodiment of the access point (AP) in a wireless communication system comprises: a third virtual link establishment module for establishing, via a current AP of a client, a virtual link between said AP and said client when said client decides to switch, said virtual link including a communication link between said AP and said current AP and a communication link between said current AP and said client; a third probe module for receiving, via said virtual link, a probe request of said client and sending a probe response to said client; and a third association module for receiving, via said virtual link, an association request of said client and sending an association response to said client.
  • Fig. 1 shows a schematic diagram of WLAN-based communication in a rail transit system in the prior art
  • Fig. 2 shows a schematic diagram of information interaction used for establishing a communication connection between a client and a candidate AP in the prior art
  • Fig. 3 shows a schematic diagram of a fast switching method in the prior art
  • Fig. 4 shows a flow chart of a fast switching method in a wireless communication system of an embodiment of the present invention
  • Fig. 5 shows a schematic diagram of a fast switching method in a wireless communication system of an embodiment of the present invention
  • Fig. 6 shows a flow chart of a fast switching method in a rail transit wireless communication system of an embodiment of the present invention
  • Fig. 7 shows a structural schematic diagram of a fast switching client in a wireless communication system of an embodiment of the present invention
  • Fig. 8 shows a structural schematic diagram of a current AP in a wireless communication system of an embodiment of the present invention.
  • Fig. 9 shows a structural schematic diagram of a candidate AP in a wireless communication system of an embodiment of the present invention.
  • the embodiments of the present invention propose a fast switching method in a wireless communication system as shown in Fig. 4, the method comprising the following steps: step 401, when a client decides to switch, the client establishes, via its current AP, virtual links with candidate APs, the virtual link including a communication link between the client and the current AP and communication links between the current AP and the candidate APs; step 402, the client sends, via the virtual links, a probe request to the candidate APs and receives probe responses of the candidate APs; step 403, the client selects, ac- cording to the probe responses of the candidate APs, a target AP from the candidate APs; step 404, the client sends, via the virtual link, an association request to the target AP and receives an association response of the target AP; and step 405, when the client starts switching, the client terminates the communication with the current AP and switches to the target AP.
  • said virtual link includes a wireless link be- tween the client and the current AP and wired links between the current AP and the candidate APs.
  • Fig. 5 shows a schematic diagram of a fast switching method in a wireless communication system of an embodiment of the present invention. As shown in Fig. 5, the current AP of the client is API, and the client de- cides to switch when moving to point A which is close to API, and at this moment pre- switching starts.
  • the pre- switching mentioned in the embodiments of the present invention refers to the preparations made before the client switches from the current AP to another AP (i.e. the target
  • the timing for deciding to switch can be determined using a variety of methods, one of which is to determine the timing of switching according to the strength of the signal emitted by the current AP (i.e. API) .
  • the client and the AP uses directional antennas in the rail transit system, in Fig. 5, when the client moves from right to left, the signal strength of API will first become increasingly strong, and when the cli- ent moves to point A, the signal strength reaches a threshold, and then the train will pass by API quickly, and when the train moves to point B where API resides, the signal strength will suddenly weaken. Therefore, in the embodiments of the present invention, when the client is informed that the signal strength of API exceeds a certain preset signal threshold which can be set in advance based on empirical values, the client starts to perform pre- switching . Another method is to determine the timing of switching according to the location of the client.
  • Step 601 when a client decides to switch, virtual links are established between the client and candidate APs, the virtual links including a wireless link between the client and the cur- rent AP and wired links between the current AP and the candidate APs.
  • the current AP is API
  • the client decides to switch when moving to a location (i.e. point A) close to API.
  • a variety of methods can be used to determine a candidate AP.
  • One of the relatively common methods is the following: all the APs store loca- tion information about their own and information about neighbor APs.
  • the client When deciding to switch, the client sends a pre- switching request to API; and after receiving the pre- switching request, API contains the information about the neighbor APs in a pre- switching response and sends same to the client, wherein the information about the neighbor APs contains the location information about the neighbor APs.
  • the client After receiving the information about the neighbor APs sent by API, according to the running direction of the train, the client selects as a candidate AP a neighbor AP with the same running direction as the train from the neighbor APs sent by API, wherein the candidate AP may be the next one or next two APs adjacent to API along the running direction of the train.
  • Another method to determine a candidate AP is the following: the client stores a list of APs which rec- ords the information about the APs in accordance with the sequence of how the APs are set on the road. Since the train route is fixed in the rail transit system, the client can determine which AP is to pass by next according to the list, that is, the client can determinate a candidate AP according to the current AP and the information about the APs recorded in the list.
  • Yet another method to determine a candidate AP is the following: information about all the APs set on the road are stored in a server, the client can then access the server via the current AP to obtain information about the neighbor APs of the current AP, and then according to the running direction of the train, the client selects as a candidate AP a neighbor AP with the same running direction as the train from the neighbor APs obtained. Additionally, the client can also use a method in the prior art to continuously scan, in the idle state, all the channels to collect information about the candidate AP . Of course, other methods can also be used to determine a candidate AP, on which the embodiments of the present invention do not impose restrictions.
  • a variety of methods can be used to establish a virtual link between the client and the candidate AP.
  • One method allows doing no more changes to the client, but the current AP modifies the MAC address filter thereof so as to be able to receive a message sent by the client to the candidate AP and forward the message to the candidate AP via its wired link with the candidate AP .
  • the current AP i.e. API
  • the current AP can add the MAC address of a candidate AP (e.g. AP2) in its MAC address filter, so that API can receive a message sent by the client to AP2 via a wireless link with API, and forward the message to AP2 via its Ethernet link with AP2.
  • Another method allows doing no more changes to the current AP, but the client sends, via its wireless link with the current AP, to the current AP the message which is sent to the candidate AP, and then the current AP forwards the message to the candidate AP via its wired link with the candidate AP; and con- versely, the candidate AP sends, via its wired link with the current AP, to the current AP the message which is sent to the client, and then the current AP forwards the message to the client via its wireless link with the client.
  • the client can use a distribution flag DS specified in the IEEE802.il standard in a message which is sent to the current AP to indicate to the current AP to forward a message the destination MAC address of which is the candidate AP, thus achieving the MAC layer communication with the candidate AP; and if the client and the candidate AP are in different subnets, the client can, in the message which is sent to the current AP, indicate to the current AP to forward, via an IP route, a message the destination IP address of which is the candidate AP, thus achieving the IP layer (layer 3) communication with the candi- date AP .
  • a distribution flag DS specified in the IEEE802.il standard in a message which is sent to the current AP to indicate to the current AP to forward a message the destination MAC address of which is the candidate AP, thus achieving the MAC layer communication with the candidate AP.
  • the current AP needs to re- encapsulate the message sent by the client to the candidate AP, but the client does not need to change the header of the message.
  • the client needs to encapsulate the message which is forwarded by the current AP and the destination address of which is the candidate AP, but the current AP does not need to re-encapsulate the message, just simply forward the message instead.
  • the embodiments of the pre- sent invention do not impose restrictions on the method for establishing a virtual link, and other methods that can be used should also be within the scope of protection of the present invention .
  • Step 602 the client sends a probe request to the candidate AP via the virtual link established between the client and the candidate AP.
  • the client sends a probe request to AP2 and AP3 over a channel where it currently resides, API changes the MAC address filter thereof to receive the probe request sent by the client to AP2 and AP3 , and then API re-encapsulates the received probe request and forwards same to AP2 and AP3 respectively via an Ethernet link.
  • the client can use a distributed flag to send to API, via a channel where it currently resides, a probe request that needs to be sent to AP2 and AP3 , and API will forward the probe request to AP2 and AP3 respectively via an Ethernet link.
  • the channel where the client currently resides refers to the chan- nel over which the client communicates with API, i.e. the channel of API .
  • Step 603 the candidate AP receives, via the virtual link, the probe request sent by the client and returns a probe response to the client.
  • AP2 and AP3 can transfer onto the channel indicated in the probe request to measure the strength of the received signal so as to generate a received signal strength indicator (RSSI) , and contain the RSSI value in the probe response and return same to the client via the established virtual link.
  • the channel indicated in the probe request is the channel where the client currently resides, i.e. the channel over which the client communicates with API. Since at this moment the client still maintains communication with API, AP2 and AP3 can continuously monitor the message sent by the client, thus quickly obtaining the RSSI value so as to facilitate the reduction of switching-decision time of the client.
  • the channel indicated in the probe request can also be the channel of AP2 or AP3 , or other channels that can be used in probe operations.
  • the client sends a probe message over the channels of AP2 and AP3 respectively, and AP2 and AP3 then, respectively, measure the strength of the received signal over their channels, generate the received signal strength indicator, and contain the RSSI value in the probe response and re- turn same to the client via the established virtual link.
  • AP2 and AP3 can also transfer onto the channel of API according to the channel information stored therein or obtained from a server, to measure the strength of the received signal, and contain the measured strength information about the received signal in the probe response. Since the channel of API is the channel where the client currently resides, AP2 and AP3 can continue monitoring the message sent by the client so as to quickly obtain the strength information about the received signal.
  • AP2 and AP3 can send, via a wired link with API, a probe response which contains the RSSI value to API, and after receiving the probe response from AP2 and AP3 , API forwards the re- ceived probe response to the client via a wireless link with the client.
  • Step 604 after receiving all the probe responses returned by the candidate AP, the client compares the RSSI values contained in the probe responses, and selects an AP with the maximum RSSI value as the target AP.
  • the client selects AP2 as the target AP .
  • Step 605 association and authentication are performed between the client and the target AP via the virtual link.
  • the client Before the client switches to the target AP, information interaction between the client and the target AP is performed via a virtual link.
  • the client selects AP2 as the target AP according to the RSSI value returned by the candidate AP, the client sends an association request to AP2 via a virtual link with AP2 and receives an association response returned by AP2 ; in addition, in the application scenario where the re- quirements regarding security are relatively high, the client sends an authentication request to AP2 via the virtual link and receives an authentication response returned by AP2.
  • the client can send to API, via its wireless link with API, an association request that needs to be sent to AP2 , and after receiving the association request, API forwards the association request to AP2 via its wired link with AP2 ; after receiving the association request, AP2 sends to API, via its wired link with API, an association response that needs to be sent to the client, and after receiving the association response, API forwards the association response to the client via its wireless link with the client.
  • the client can complete the authentication operation with AP2 by way of relaying API, which will not be described here.
  • the information interaction process between the client and target AP does not take up the switching time .
  • the association response returned by the target AP can also include channel information about the target AP .
  • Step 606 after receiving, via the virtual link, the authentication successful response returned by the target AP, the cli- ent can generate a virtual connection table for maintaining the switching information required for establishing a connection between the client and the target AP.
  • the switching information may comprise: the link status information (such as RSSI value) , the beacon interval information, and the MAC address, SSID and channel of the target AP, and other information .
  • Step 607 when the client starts switching, the client terminates the communication with the current AP and switches to the channel of the target AP, thus completing the switching to the target AP.
  • the client can update its system parameters according to the switching information maintained in the virtual connection table and send a switching complete signal to the target AP.
  • Step 608 after receiving the switching complete signal sent by the client, the target AP updates its system parameters and completes switching. After switching, the target AP becomes the current AP of the client.
  • the switching method proposed in the embodiments of the present invention has the following advantages:
  • a virtual link is established using a communication link between the client and the current AP and communication links between the current AP and the candidate APs .
  • the client can complete the information interaction with the target AP before switching to the target AP without interrupting the communication with the current AP, for example, the client obtains the RSSI values emitted by the candidate APs, selects the target AP and performs association and authentication with the target AP, and all the operations before switching can be completed at the pre- switching stage through the virtual link, whereas when the signal strength emitted by the current AP weakens and the real switching starts, the only thing the client needs to do is to update its system parameters based on the switching information maintained by itself. Therefore, the switching method can not only reduce the switching-deciding time, but also reduce the connection- establishment time, so that the time for the client to switch from one AP to another AP will be greatly reduced.
  • all the information interaction between the client and the candidate AP is conducted through the virtual link, which can guarantee the quality of communications between the client and the candidate APs, thus avoiding an increase in the number of APs.
  • the client since the client decides to switch before the signal strength of the current AP weakens, and at this moment, its communication with the current AP has not been interrupted, the quality of communication between the client and the current AP can be guaranteed.
  • the client can frequently transfer onto a channel where another AP resides and to send a message without interrupting the communication with the current AP, thereby simplifying the operation of the client.
  • the candidate AP can continuously monitor the message sent by the client, thus quickly obtaining the RSSI value so as to facilitate the reduction of the switching- deciding time of the client.
  • all the information used for switching can be interacted through the virtual link before the client switches to the target AP, and can be implemented by means of a distributed flag or an IP route under the IEEE802.il standard framework; therefore, no changes need to be made to the relevant part in the IEE802.11 standard, but simply modifying the software of the client and the AP instead.
  • the fast switching method proposed in the embodiments of the present invention is particularly suitable for the wireless communication scenario where at least one of the AP and the client is using directional antennas, such as a wireless commu- nication scenario in a rail transit system.
  • the switching method proposed in the embodiments of the present invention is also suitable for the wireless communication scenario where the AP and the client use omnidirec- tional antennas.
  • the method for the client to decide the switching timing can be slightly modified, for example, when the client is informed that the signal strength of the current AP is below a preset threshold, the client decides to switch.
  • Another embodiment of the present invention also proposes a fast switching method in a wireless communication system, the method comprising the steps of: when a client decides to switch, its current AP is used to establish virtual links between the client and candidate APs, the virtual links including a communication link between the client and the current AP and communication links between the current AP and the candidate APs; the current AP receives a probe request sent, via the virtual links, by the client to the candidate APs and forwards the probe request to the candidate APs, and receives probe responses sent, via the virtual links, by the candidate APs to the client and forwards the probe responses to the client; the current AP receives an association request sent, via the virtual link, by the client to a target AP and forwards the association request to the target AP, and receives an association response sent, via the virtual link, by the target AP to the client and forwards the association response to the client; and when the client starts switching, the current AP terminates the communication with the client.
  • the current AP when the abovementioned first method for establishing a virtual link is used, the current AP can estab- lish virtual links between the client and the candidate APs by modifying its MAC address filter.
  • the method may further comprise: the current AP receives an authentication request sent, via the virtual link, by the client to the target AP and forwards the authentication request to the target AP, and receives an authentication response sent, via the virtual link, by the target AP to the client and forwards the authentication response to the client.
  • Another embodiment of the present invention also proposes a fast switching method in a wireless communication system, the method comprising the steps of: when a client decides to switch, candidate access points (APs) establish, via a current AP of the client, virtual links with the client, the virtual links including communication links between the candidate APs and the current AP and a communication link between the current AP and the client; the candidate APs receive, via the virtual links, a probe request of the client and send probe responses to the client; and the candidate APs receive, via the virtual links, an association request of the client and send association responses to the client.
  • candidate access points APs
  • the probe request can contain information about a channel where the client currently resides. Then in this embodiment, the method further comprises: the candidate APs transfer onto the channel to measure the strength of a received signal, and contain the measured strength information about the received signal in the probe response.
  • the method may further com- prise: the candidate APs receive, via the virtual links, an authentication request of the client and send authentication responses to the client, to meet the high security requirements.
  • the embodiments of the present invention also propose a fast switching system in a wireless communication system, the system comprising a client and a plurality of APs.
  • the client is used for establishing, via its current AP, virtual links with candidate APs when it decides to switch, the virtual links including a communication link between the client and the current AP and communication links between the current AP and the candidate APs; sending a probe request, via the virtual links, to said candidate APs and receiving probe responses of said candidate APs; selecting, according to the probe responses of said candidate APs, a target AP from the candidate APs; sending an association request, via said virtual link, to said target AP and receiving an association response of said target AP; and terminating the communication with the current AP and switching to the target AP when switching is started;
  • the current AP is used for establishing virtual links between the client and the candidate APs when the client decides to switch; receiving a probe request sent, via the virtual link, by the client to the candidate APs and forwarding the probe request to the candidate APs, and receiving probe responses sent, via the virtual links, by the candidate APs to the client and forwarding the probe responses to the client
  • one embodiment of the present invention also proposes a structural schematic diagram of a fast switching client in a wireless communication system. As shown in Fig.
  • the client comprises: a first virtual link establishment module 701 for establishing, via a current AP of the client, virtual links between the client and candidate APs when the client decides to switch, the virtual links including a communication link between the client and the current AP and communication links between the current AP and the candidate APs; a first probe module 702 for sending a probe request, via said virtual link, to said candidate APs and receiving probe re- sponses of said candidate APs; a selection module 703 for selecting, according to the probe responses of the candidate APs, a target AP from the candidate APs;
  • a first association module 704 for sending an association request, via the virtual link, to said target AP and receiving an association response of said target AP; and a first switching module 705 for terminating the communication with the current AP and switching to the target AP when the client starts switching.
  • the first virtual link establishment module 701 can use an IP route to establish, via the current AP, virtual links with the candidate APs .
  • the probe request can contain information about a channel where the client currently resides; and the probe response can contain strength information about received signals measured by the candidate APs over the channel.
  • the client can further comprise a first authentication module for sending, via the virtual link, an authentication request to the target AP and receiving an authentication response of the target AP.
  • the association response can contain information about a channel of the target AP; and when the client starts switching, the first switching module 705 is used for switching to the channel of the target AP .
  • the client can further comprise: a switching deciding module for deciding to switch when the signal strength of the current AP received by the first probe module
  • one embodiment of the present invention also provides an AP in a wireless communication system.
  • the AP is a current AP of a client, and can comprise: a second virtual link establishment module 801 for establishing virtual links between the client and candidate APs when the client decides to switch, the virtual links including a communication link between the client and the AP and communication links between the AP and the candidate APs; a second probe module 802 for receiving a probe request sent, via the virtual links, by the client to the candidate APs and forwarding the probe request to the candidate APs, and receiving probe responses sent, via the virtual links, by the candi- date APs to the client and forwarding the probe responses to the client; a second association module 804 for receiving an association request sent, via the virtual link, by the client to the target AP and forwarding the association request to the target AP, and
  • the second virtual link establishment module 801 can be used for establishing virtual links between the client and the candidate APs by modifying a MAC address filter of the AP .
  • said AP can further comprise a second authentication module 806 for receiving an authentica- tion request sent, via the virtual link, by the client to the target AP and forwarding the authentication request to the target AP, and receiving an authentication response sent, via the virtual link, by the target AP to the client and forwarding the authentication response to the client.
  • a second authentication module 806 for receiving an authentica- tion request sent, via the virtual link, by the client to the target AP and forwarding the authentication request to the target AP, and receiving an authentication response sent, via the virtual link, by the target AP to the client and forwarding the authentication response to the client.
  • the AP is a candidate AP, and can comprise: a third virtual link establishment module 901 for establishing, via a current AP of a client, a virtual link with the client when the client decides to switch, the virtual link including a communication link between the AP and the current AP and a communication link between the current AP and the client; a third probe module 902 for receiving, via the virtual link, a probe request of the client and sending a probe response to the client; and a third association module 904 for receiving, via the virtual link, an association request of the client and sending an asso- ciation response to the client.
  • a third virtual link establishment module 901 for establishing, via a current AP of a client, a virtual link with the client when the client decides to switch, the virtual link including a communication link between the AP and the current AP and a communication link between the current AP and the client
  • a third probe module 902 for receiving, via the virtual link, a probe request of the client and sending a probe
  • the probe request can preferably contain information about a channel where the client currently resides; and the third probe module 902 is then used for measuring the strength of a received signal over the current channel of the client, and containing the measured strength information about the received signal in the probe response.
  • the candidate AP can further comprise a third authentication module 906 for receiving, via said virtual links, an authentication request of said client and sending an authentication response to said client.
  • client and AP which are provided in the embodiments of the present invention, please refer to the relevant description in the above- mentioned method embodiment, which will not be described here.
  • client and AP can also obtain the technical effects that can be obtained by the abovementioned fast switching method according to the embodiments of the present invention, which will not be described in detail here.
  • each of the abovementioned flow diagrams and structural schematic diagrams may be a physical structure or a logical structure, i.e., some modules may be implemented by one and the same phys- ical entity, or some modules may be implemented respectively by a plurality of physical entities, or may be implemented by certain components in a plurality of independent devices together.
  • the hardware unit may be im- plemented either mechanically or electrically.
  • a hardware unit may include a permanently dedicated circuit or logic (such as a dedicated processor, FPGA, or ASIC) to perform a corresponding operation.
  • the hardware unit may further include a programmable logic or circuit (such as a general pur- pose processor, or other programmable processors) that can perform a corresponding operation by way of temporary software settings.
  • a mechanical means, or a dedicated permanent circuit or a temporarily set circuit may be determined based on considerations of cost and time.
  • the present invention also provides a machine-readable medium which stores an instruction that enables a machine to execute the fast switching method according to the embodiments of the present invention.
  • a system or a device with a storage medium can be provided, on which storage medium there are stored software program codes for implementing the func- tions of any of the abovementioned embodiments, and a computer (or CPU or MPU) of the system or device is enabled to read and execute the program codes stored in the storage medium.
  • the functions of any of the abovementioned embod- iments can be implemented by the program codes per se read from the storage medium, therefore the program codes and the storage medium storing the program codes constitute a part of the present invention.
  • the embodiments of the storage medium for providing program codes include a floppy disk, a hard disk, a magnetic optical disk, an optical disk (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, and DVD+RW) , a magnetic tape, a non-volatility storage card, and a ROM.
  • the program codes can be downloaded from a server computer via a communication network.
  • the operating system running in the computer can be enabled to complete part of or all of the practical operations, not only can be by way of exe- cuting the program codes read out by the computer, but also can be by way of instructions based on the program codes, thereby realizing the function of any one of the above-mentioned embodiments .
  • writing the program codes read from the storage medium into the memory provided in the extension board inserted inside the computer or into the memory provided in the extension unit connected to the computer subsequently the instructions based on the program codes cause the CPU mounted on the extension board or the extension unit to execute part of or all of the practical operations, thereby realizing the function of any one of the abovementioned embodiments .

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Small-Scale Networks (AREA)

Abstract

La présente invention concerne un procédé de commutation rapide, un système de commutation rapide, un client et un point d'accès (AP) dans un système de communication sans fil. Selon ledit procédé : lorsqu'un client décide de commuter, il établit, par l'intermédiaire de son AP courant, des liens virtuels avec des AP candidats, lesquels liens virtuels comprennent un lien de communication entre le client et l'AP courant et des liens de communication entre l'AP courant et les AP candidats; le client envoie une requête de sondage aux AP candidats, par l'intermédiaire des liens virtuels, et reçoit des réponses de sondage des AP candidats; le client sélectionne, en fonction des réponses de sondage des AP candidats, un AP cible parmi les AP candidats; le client envoie, par l'intermédiaire du lien virtuel, une requête d'association à l'AP cible et reçoit une réponse d'association de l'AP cible; et lorsque le client débute la commutation, il met fin à la communication avec l'AP courant et commute sur l'AP cible. Ce procédé permet de réduire considérablement le temps de commutation.
EP13756374.8A 2012-08-24 2013-08-23 Procédé de commutation rapide, système de commutation rapide et client dans un système de communication sans fil Withdrawn EP2888905A2 (fr)

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CN201210305958.2A CN103634860B (zh) 2012-08-24 无线通信系统中的快速切换方法、系统和客户端
PCT/EP2013/067545 WO2014029870A2 (fr) 2012-08-24 2013-08-23 Procédé de commutation rapide, système de commutation rapide et client dans un système de communication sans fil

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KR102239729B1 (ko) 2014-04-07 2021-04-13 인터디지털 씨이 페이튼트 홀딩스 이동 통신 네트워크에서 핸드오버를 제어하는 방법과 이러한 방법을 구현하는 장치 및 시스템
US10448246B2 (en) 2014-04-29 2019-10-15 Hewlett Packard Enterprise Development Lp Network re-convergence point
EP3035741A1 (fr) * 2014-12-17 2016-06-22 Thomson Licensing Qualité utilisateur réseau local sans fil (WLAN) de contrôle d'expérience dans un environnement à plusieurs points d'accès
CN106385699B (zh) * 2016-08-31 2019-08-20 锐捷网络股份有限公司 一种无线分布式系统中选择根桥的方法、装置以及服务器
CN108235384B (zh) * 2016-12-12 2020-10-16 华为技术有限公司 一种无线网络切换方法和装置
JP7114223B2 (ja) * 2017-02-20 2022-08-08 株式会社東芝 機器制御システム、通信方法、無線端末及び制御装置
KR102580426B1 (ko) * 2017-08-25 2023-09-20 삼성메디슨 주식회사 초음파 진단 장치 및 그 동작 방법
CN109246784B (zh) * 2018-11-02 2021-03-26 新华三技术有限公司 一种漫游控制方法和装置
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CN111726842B (zh) * 2020-05-14 2023-03-03 深圳互由科技有限公司 漫游切换方法、电子设备及计算机可读存储介质
CN115396887B (zh) * 2022-07-22 2024-11-05 西安电子科技大学 一种高速移动终端快速安全切换认证方法、装置及系统
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