Radio communication arrangements

• US 7,193,991 B2
• Filed: 04/30/2002
• Issued: 03/20/2007
• Est. Priority Date: 05/01/2001
• Status: Expired due to Fees

• Current Assignee: Uniloc 2017 LLC (SoftBank Group Corp.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Gallo, Francesco, Melpignano, Diego
• Primary Examiner(s): Ferris, Derrick W.
• Application Number:
  US10/135,353
• Publication Number:
  US 20030003912A1
• Time in Patent Office: 1,785 Days
• Field of Search: 370/345, 370/338, 370/349, 370/352, 370/356, 370/254, 455/436, 455/41.2
• US Class Current: 370/352
• CPC Class Codes: H04W 36/0055 Transmission or use of information for re-establishing the radio link
• CPC Class Codes: H04W 84/20 Master-slave selection or change arrangements

Abstract

An arrangement is disclosed for performing a handoff of a slave unit (MT) from a currently wireless connected first master unit (AP₁) of a shared resource network to a further master unit (AP₂) of the shared resource network, the arrangement including:

a) holding in the first master unit information about the topology of the shared resource network; and

b) activating during a handoff a paging procedure in one or more further master units (AP_2-4) based on the topology, in the paging procedure the or each further master unit pages the slave unit.

Claims

1. A method of performing a handoff of a currently wireless connected slave unit from a first master unit of a shared resource network having a topology to a further master unit of said shared resource network, the method including:

a) holding in said first master unit information about the topology of said shared resource network;

b) activating during said handoff a paging procedure in one or more further master units based on said topology, in said paging procedure the or each further master unit pages said slave unit; and

c) holding said network topology information in the form of a matrix, said network topology information including which of said one or more further master units are neighbors of said first mater unit.

2. A method according to claim 1, including determining in which of said further master units to activate said paging procedure on the basis of their proximity to said first master unit, activating said paging procedure only in further master units neighboring said first master unit.

3. A method according to claim 1, including said first master unit supplying to the or each further master unit during a said handoff paging information relating to said slave unit, which information assists the or each neighboring master unit in paging said slave unit and said information includes an address of said slave unit.

4. A method according to claim 1, including using said network topology information to select neighboring master units for the exchange of clock offset information, and deriving said clock offset or offsets by exchanging time-stamped information between master units.

5. A method according to claim 1, including exchanging messages between said master units through a shared resource network connecting them, said messages including said network topology information.

6. A method according to claim 1, including determining said network topology information substantially upon initialization of said shared resource network or after initialization so as to determine which of the neighboring access points should the contacted to exchange clock offset information in order to take account of clock drifts which occur during network operation.

7. A method according to claim 1, including determining said network topology by exporting the value of a master unit native clock to a master unit host, by means of a vendor specific Host Controller Interface command or by periodically sending at least one said master unit into an inquiry mode in which it communicates with other master units and uses their responses to update its estimate of their respective clock offsets.

8. A method according to claim 1, including said slave unit triggering a handoff procedure by sending a handoff request to its currently connected master unit and entering into a continuous page scan, said currently connected master unit forwarding said handoff request to one or more substantially neighboring said master units and including a network address of said slave unit.

9. A method according to claim 8, including performing said handoff procedure as a hard hand-over in which resources allocated by said currently connected master unit to connection with said slave unit are not torn down or released until a connection is at least under establishment between said slave unit and a next or target master unit, the original connection being broken on the expiration of a preset timeout or on receipt of an acknowledgment message received from said next master unit, and if said handoff does not succeed, it is still possible for the slave unit to return to its original connection.

10. A method according to claim 1, including, on receipt of a message indicative of connection of said slave unit to a next said master unit, canceling an attempt by a further said master unit at paging or connecting with said slave unit.

11. A method according to claim 1, including operating said master units in such a manner that there is substantially no overlap in coverage area between any further master units neighboring said currently connected master unit, whereby said slave unit receives identity packets from only its closest further master unit.

12. A method according to claim 1, including using said network topology information to configure one or more of a group of master units with information about which of said master units are neighbors and what are their network addresses, holding said network topology information in said matrix indicating which said master units are neighbors, which others are in at least part of the coverage of said network, and storing a said matrix locally to one or more of said master units.

13. A method according to claim 1, including gathering said network topology information in an automatic manner, by using a mobile probe adapted to probe said master units by activating an inquiry procedure in different positions within the coverage of said shared resource network and further adapted to make a record of the response or responses from said master units to said inquiries.

14. A method according to claim 13, wherein said slave and master units comprise a mobile terminal and access points respectively of said shared resource network, and said shared resources network comprises a Bluetooth local area network.

15. A communications unit for use as a slave unit in the method of claim 1, said unit adapted;

to send a handoff request to a master unit,

to advertise its page scan time window in said handoff request,

to enter into a substantially continuous page scan state during said advertised page scan time window, and

to select from a plurality of paging master units a particular said master unit for connection therewith.

16. A communications unit for use as a master unit in a method according to claim 1, wherein said master unit is adapted to page a slave unit during a handoff procedure, and to hold information about the topology of a shared resource network of which in use it forms a part, said network topology information includes which master units are neighbors and what are their addresses.

17. A communications unit according to claim 16, adapted to accept handoff requests from slave units or from said shared resource network, and to acknowledge said handoff requests and to forward a received said handoff request to at least one neighboring master unit via a shared resource network, said unit further adapted to schedule paging processes used to attempt connection with a plurality of slave units.

18. A communications unit according to claim 17, wherein, if a number of said handoff requests made from a plurality of slave units to said communications unit for connection exceeds the available capacity of said communications unit to finalize paging procedures before expiry of any one or more page scan windows of the requesting slave units, a signal indicative of congestion is communicated to one or more further communications units acting as master units and, if said communications unit receives from a slave unit a handoff request which involves a master unit which is congested, said slave unit is informed that it must wait for said handoff, by staying in a continuous page scan for an extended period.

19. A communications unit according to claim 18, wherein said communications unit is adapted to stop paging a particular said slave unit on or after a message is received indicative of a successful connection between a further communications unit acting as a master unit and said slave unit, said further communications unit adapted to send an acknowledgment message to at least one master unit indicative of successful paging of, and successful connection to, a slave unit.

20. A radio communications arrangement adapted to perform a handoff of a currently wireless connected slave unit from a first master unit of a shared resource network having a topology to a further master unit of said shared resource network, said shared resource network being adapted to hold in said first master unit information about the topology of said network and further adapted to activate during said handoff a paging procedure in one or more further master units based on said topology, in said paging procedure one or more said further master units page said slave unit and holding said network topology information in the form of a matrix, said network topology information including which of said one or more further master units are neighbors of said first mater unit.

21. An arrangement according to claim 20, wherein said slave and master units comprise a mobile terminal and access points respectively of said shared resource network, and said shared resources network comprises a Bluetooth local area network.