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1. WO2007099031 - PROCÉDÉ ET SYSTÈME DE TRANSFERT SANS COUPURE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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CLAIMS

1. A communication system (200) for performing the seamless handover of a mobile station

(210) between at least a first wireless access point (206) and a second wireless access point (208) within wireless LAN, wherein, the mobile station

(210) is in coverage area of at least the first wireless access point (206) for receiving and/or sending the data from and/or to the first wireless access point (206) , the communication system (200) comprises :

a first server (202) for storing data from a data source;

a switch (204) for exchanging data between the first server (202) and the first and second wireless access points (206, 208) ; and

a second server (212) , coupled with the switch (204), for receiving the data from the first server (202) via the switch (204) when the mobile station (210) roams from the first access point (206) to the second access point (208) , and transferring the stored data to the mobile station (210) through the switch (204) after the roaming.

2. The communication system (200) according to claim 1, wherein the first server (202) is a streaming server for storing streaming media data for the mobile station (210) .

3. The communication system (200) according to any one of claims 1 and 2, wherein the second server (212) is a cache server for caching the data from the first server (202) when the mobile station (210) roams from the first access point (206) to the second access point (208) , and transferring the cached data to the mobile station (210) through the switch (204) .

4. The communication system (200) according to any one of claims 1 to 3, wherein the communication system (200) is a WLAN video stream broadcasting system, and the switch (204) is an Ethernet switch.

5. The communication system (200) according to any one of claims 1 to 4, wherein

the mobile station (210) includes a data caching start request message to be sent to the second server (212) during the roaming;

the second server (212) includes an acknowledgement message to be sent to the mobile station (210) in response to the data cache start request message, so as to start to receive and cache the data for the mobile station (210) from the first server (202) ;

the mobile station (210) includes a data cache stop request message to be sent to the second server (212) after the handover or scan process is over, so as to stop caching the data for the mobile station (210) , and transfer the cached data to the mobile station (210) .

6. The communication system (200) according to claim 5, further comprising a multicast group joined with the second server (212) to get multicast data from the first server (202) .

7. The communication system (200) according to claim 5, wherein the second server (212) includes a fake Ethernet frame for an unicast data, which is assembled with the MAC address of the mobile station (210) to send the assembled frame to the switch once or several times, so as to deceive the switch (204) , make the switch (204) change the MAC-port map entry of the mobile station (210) , and then receive the data that otherwise be directed to the mobile station (210) from the first server (202) .

8. The communication system (200) according to anyone of Claims 1 to 7, wherein the data source is a live video source (214) for sending stream video data to the first server.

9. The communication system (200) according to anyone of Claims 1 to 8, wherein the second server (212) can work in peer-to-peer mode, and the second sever (212) can be integrated with the mobile station (210) .

10. A communication method for performing the seamless handover of a mobile station between at least a first wireless access point and a second wireless access point within wireless LAN, which comprises following steps:
storing data from a data source by a first server;

exchanging data between the first server and the first and second wireless access points via a switch;
receiving and/or sending the data from and/or to the first wireless access point by the mobile station while it is in coverage area of at least the first wireless access point; and
receiving data from the first server via the switch by a second server when the mobile station roams from the first access point to the second access point, and transferring the stored data to the mobile station through the switch after the roaming .

11. The communication method according to claim 10, wherein the first server is a streaming server for storing streaming media data for the mobile station.

12. The communication method according to any one of claims 10 and 11, wherein the second server is a cache server for caching the data from the first server when the mobile station roams from the first access point to the second access point, and transferring the cached data to the mobile station through the switch.

13. The communication method according to any one of claims 10 to 12, wherein the communication system is a WLAN video streaming communication system, and the switch is an Ethernet switch.

14. The communication method according to any one of claims 10 to 13, wherein during roaming from the first access point to the second access point and performing channel scanning to find available wireless access points:

the mobile station sends a data caching start request message to the second server;

the second server sends an acknowledgement message to the mobile station in response to the data cache start request, and starts to receive and cache the data for the mobile station from the first server;

after the handover or scan process is over, the mobile station sends data cache stop request message to the second server; and

the second server stops caching the data for the mobile station in response to the data cache stop request, and transfers the data to the mobile station .

15. The communication method according to claim 16, wherein upon receipt of a multicast data, the second server joins this multicast group to get the multicast data from the first server.

16. The communication method according to claim 15, wherein upon receipt of an unicast data, the second server produces a fake Ethernet frame and assembles the fake Ethernet frame with the MAC address of the mobile station to send the assembled frame to the switch once or several times, so as to deceive the switch, make the switch change the MAC- port map entry of the mobile station, and then receive the data that otherwise be directed to the mobile station from the first server.

17. The communication method according to anyone of claims 10 to 16, wherein the data source is a live video source for sending stream video data to the first server.

18. The communication method according to anyone of claims 10 to 17, wherein the second server can work in peer-to-peer mode, the second sever can be integrated with the mobile station.

19. The seamless handover method according to claim 14, wherein the data cache start request message comprises:

a control message flag field indicating to the second server and the mobile station whether the received UDP packet is a caching control message;

a message type field having a first value, indicating the message is a data cache start request;

a sequence number of request, which is a unique sequence number which in the mobile station for the message;

a stream destination address, which is the IP address of the stream to be cached;

a stream destination port, which is the UDP port of the stream to be cached; and

a padding field, which is used to make the message word-aligned.

20. The seamless handover method according to claim 19, wherein the data cache stop request message comprises:

a control message flag field indicating to the second server and the mobile station whether the received UDP packet is a caching control message;

a message type filed having a second value other than the first value, indicating the message is a data cache stop request;

a sequence number of request, which is a unique sequence number in the mobile station for the message;

a stream destination address, which is the IP address of the stream to be cached;

a stream destination port, which is the UDP port of the stream to be cached; and

a padding field, which is used to make the message word-aligned.

21. The seamless handover method according to anyone of claims 19 to 20, wherein the acknowledgement message comprises:

a control message flag field indicating to the second server and the mobile station whether the received UDP packet is a caching control message;

a message type field having a third value other than the first value and the second value, indicating the message is a data cache start request;

a sequence number of request, which is a unique sequence number in the mobile station for the message;

a requester's address, which is the IP address of the mobile station which startups caching request;

a requester's port, which is the UDP port of the mobile station which startups caching request; and

a padding field, which is used to make the message word-aligned.