Process of switching to a server of cells sent by a module linked to a local access network for mobile (stations), as well as such a network for implementation of said process

• US 6,243,363 B1
• Filed: 10/08/1997
• Issued: 06/05/2001
• Est. Priority Date: 10/25/1996
• Status: Expired due to Fees

• Current Assignee: France Telecom SA (Orange S.A.)
• Original Assignee: France Telecom SA (Orange S.A.)
• Inventors: Roussel, Olivier, Quinquis, Jean-Paul
• Primary Examiner(s): Martin-Wallace, Valencia
• Assistant Examiner(s): Nguyen, Kim T.
• Application Number:
  US08/947,278
• Time in Patent Office: 1,336 Days
• Field of Search: 370/331, 370/332, 370/328, 370/329, 370/338, 370/355, 370/349, 370/389, 370/395, 370/399, 370/397, 370/277
• US Class Current: 370/277
• CPC Class Codes: H04L 2012/5607 Radio
• CPC Class Codes: H04L 2012/561 Star, e.g. cross-connect, concentrator, subscriber group equipment, remote electronics
• CPC Class Codes: H04L 2012/5642 Multicast/broadcast/point-multipoint, e.g. VOD
• CPC Class Codes: H04L 2012/5643 Concast/multipoint-to-point
• CPC Class Codes: H04L 49/3081 ATM peripheral units, e.g. policing, insertion or extraction
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections
• CPC Class Codes: H04W 36/12 Reselecting a serving backbone network switching or routing node
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

The invention concerns a directional method for a server for cells transmitted by a module attached to a local mobile area network as well as a network of this type for implementing said method.

The directional method applies to a network which is comprised of a plurality of concentration stages and terminals linked to the low-level concentration stages, said network comprising servers respectively linked to concentration stages.

This method is characterized therein that it consists of initially establishing permanent virtual channels in direction of the servers and, when a mobile is connected to two terminals of said network, said two terminals ascertain the closest common server and modify the header of the user cells transmitted by said mobile in such a way that they carry the identifier VPI/VCI of the channel established for said server so as to enable it to be processed there.

The present invention also concerns a network provided for implementing said method.

Claims

1. A method for transmitting user'"'"'s cells from terminals to a switch stage of a local access network during a handover phase while a mobile unit is simultaneously in an area under coverage of two terminals,

said network comprising terminals, concentration stages and a switch stage arranged in levels of hierarchy, means for linking said terminals to inputs of the concentration stages at a low hierarchical level and for linking outputs of the concentration stages at a high hierarchical level to said switch stage,

means for identifying a VPI/VCI for each communication that is allocated to a mobile user'"'"'s cells during a call phase,

said method including the steps of:

providing said network with servers associated with some of said concentration stages and said switch stage, said servers processing the flow of cells respectively emitted simultaneously by two terminals serving a coverage area in which a mobile unit is then located and for outputting one processed flow of cells,

establishing a permanent virtual channel with a particular VPI identifier for each of said servers, and

a plurality of steps carried out when a mobile unit already in communication moves into an area simultaneously served by two terminals of said network, as follows;

determining the common server closest to said terminals,

modifying the identifier VPI/VCI of the user'"'"'s cells in the flows of cells emitted by said terminals, said modified identifier being the identifier of the permanent virtual channel of said determined common server so that cells emitted by both terminals can be processed in said server,

and re-allocating the initial user'"'"'s cells identifier VPI/VCI of the cells of the server output flow so that processed cells can be directed to said switch stage.

2. A method according to claim 1 further comprising the step of initially establishing permanent virtual channels to the servers associated with concentration stages to which said servers are linked.

3. A method according to claim 1 wherein said servers are respectively linked by multiplex connections leaving the concentration stages, and further steps wherein in each of said servers initially establish a permanent virtual channel extending to a functional unit of said server, and determining the closest common server when said mobile unit is connected to two terminals, and modifying the header of the cells in such a way that they carry the VPI/VCI identifier of the established channel to a function unit of said server.

4. A method according to claim 1 further comprising the step of establishing a virtual channel to each of a plurality of said hierarchy levels of said concentration stages to which said servers are linked.

5. A method according to claim 4 further comprising the step of connecting said mobile unit to exchange dialogue information with the terminals, said information relating to the relative localization of said two terminals in said local network.

6. A method according to claim 5 further comprising the step wherein each of said two terminals transmits information to the other terminal on a permanent signal channel which is specific to it, said other terminal ascertaining the localization of said transmitting terminal responsive to the identifier of said channel carried by the cells transmitted by said terminal.

7. A method according to claim 6 wherein the permanent signal channel connected to each terminal for a transmission of said information carries an identifier consisting of a code having N−

1 words, N being the number of hierarchy levels of said concentration stages of the network, and a Jrd word differentiating each concentration stage of the Jrd level linked to a same concentration stage of level J+1.

8. A method according to claim 7 further comprising the step of ascertaining the closest server, each terminal comparing the identifier of the signal channel which is assigned to it and the identifier of the signal channel on which it received said information from the other terminal, determining the word which differentiates channels and, if it is the nth word, ascertaining the closest server as being the one which is linked to the concentration stage of level N+1.

9. A method according to claim 5 further comprising the step wherein each terminal to which said mobile unit is connected uses a look up table to ascertain the closest server in response to the information relating to the location of said two terminals.

10. A method according to claim 1 further comprising the step of starting from the moment when the mobile unit is connected to said two terminals and continuing up to the moment when the mobile unit is again connected to a single terminal, and the further step comprises inserting an indicator into a header of the user cells that is transmitting and said terminals to which said mobile user is connected modifying the header of said cells only while said cells carry said inserted indicator.

11. A method according to claim 10 further comprising a step wherein an original terminal modifies the header of said cells only when it has received the message concerning said information from the new terminal.

12. A method according to claim 11 further comprising a step wherein the new terminal modifies the header of said cells only when a connection based on it has been made.

13. A method according to claim 1 wherein said servers are macrodiversity servers.

14. A local access network for mobile telephones, said network comprising terminals, concentration stages and a switch stage arranged in successive levels of hierarchy, said terminals being linked to the inputs of the concentration stages in a low level hierarchy and the outputs of concentration stages in a high level hierarchy being linked to said switch stage, a VPI/VCI identifier means for each communication then allocated to a mobile user'"'"'s cells during a call phase, said network comprising server means associated with at least some of said concentration stages and said switch stage, said server means processing a flow of cells respectively emitted simultaneously by two terminals serving an area under a coverage in which a mobile unit is then located and for outputting one processed flow of cells, means comprising a permanent virtual channel with a particular VPI identifier being provided by said server, said network comprising means for determining which common server is closest to said terminals when a mobile unit already in communication is simultaneously connected to two terminals of said network, means for modifying the VPI/VCI identifier of the user'"'"'s cells in the flow of the cells emitted by said terminals, the modified identifier becoming the identifier of the permanent virtual channel of said determined common server, whereby cells emitted by both terminals are in said determined common server, and means for thereafter reallocating the initial VPI/VCI identifier of the user'"'"'s cells in the server output flow of cells so that processed cells can be directed to said switch stage.

15. A network according to claim 14 wherein said servers are respectively linked to the concentration stages and means for initially establishing said permanent virtual channels to the servers in the concentration stages to which the servers are linked.

16. A network according to claim 14 wherein said servers are respectively linked by a multiplex connection when leaving the concentration stages;

and said multiplex connection comprises means in each of said servers for initially establishing a permanent virtual channel extending to a functional unit of said server, means responsive to said mobile unit being connected simultaneously to two terminals of said network for ascertaining the closest common server and for modifying the header of the cells to carry the identifier VPI/VCI of the established channel to said functional unit of said closest server.

17. A network according to claim 14 wherein each terminal includes dialogue information for exchanging with any other terminal of said network, the dialogue information relating to the relative localization of said two terminals in said local network.

18. A network according to claim 14 wherein each terminal has a look up table for making it possible to ascertain the closest server in response to said information received from another terminal.

19. A network according to claim 14 wherein said servers are macrodiversity servers.