Radio communication arrangements

• US 20030003912A1
• Filed: 04/30/2002
• Published: 01/02/2003
• Est. Priority Date: 05/01/2001
• Status: Active Grant

• Current Assignee: Uniloc 2017 LLC (FIG LLC (d/b/a Fortress Investment Group LLC))
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Gallo, Francesco, Melpignano, Diego
• Granted Patent: US 7,193,991 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/0064 of control information between different access points
• CPC Class Codes: H04W 36/08 Reselecting an access point
• 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 said shared resource network, the arrangement including:

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

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

Claims

1. A method of performing a handoff of a currently wireless connected slave unit (MT) from a first master unit (AP₁) of a shared resource network to a further master unit (AP₂) of said shared resource network, the method including:

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

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

2. A method according to claim 1, including determining in which of said master units (AP_2-4) to activate said paging procedure on the basis of their proximity to said first master unit (AP₁), preferably activating said paging procedure only in further master units (AP_2,3) neighboring said first master unit (AP₁).

3. A method according to claim 1 or claim 2, including said first master unit (AP₁) supplying to the or each further master unit (AP_2,3) during a said handoff paging information relating to said slave unit (MT), which information assists the or each neighboring master unit (AP_2,3) in paging said slave unit and includes for example an address (MAC) of said slave unit.

4. A method according to any preceding claim, including using said network topology information to select neighboring master units (AP_1-4) for the exchange of clock offset information, preferably deriving said clock offset or offsets by exchanging time-stamped information (T1-T4) between master units (AP_1-4).

5. A method according to any preceding claim, including exchanging messages between said master units (AP_1-4) through a shared resource network connecting them and preferably including passing in said messages said network topology information.

6. A method according to any preceding claim, including determining said network topology information substantially upon initialization of said shared resource network or after initialization so as for example to determine which of the neighboring access points (AP_1-4) should be contacted to exchange clock offset information in order to take account of clock drifts which occur during network operation.

7. A method according to any preceding claim, including determining said network topology by exporting the value of a master unit native clock (CLKN_1-6) to a master unit host (H), for example by means of a vendor specific Host Controller Interface (HCI) command or by periodically sending at least one said master unit (AP_1-4) into an inquiry mode in which it communicates with other master units (AP_1-4) and uses their responses to update its estimate of their respective clock offsets (CLKE_1-4).

8. A method according to any preceding claim, including said slave unit (MT) triggering a handoff procedure by sending a handoff request to its currently connected master unit (AP₁) and preferably substantially immediately entering into a continuous page scan, said currently connected master unit (AP₁) preferably forwarding said handoff request to one or more substantially neighboring said master units (AP_2,3) and preferably including a network address (MAC) of said slave unit (MT).

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 (AP₁) to connection with said slave unit MT 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 (AP₂), the original connection preferably being broken on the expiration of a preset timeout or on receipt of an acknowledgment message received from said next master unit (AP₂) whereby, if an attempted handoff does not succeed, it is still be possible for the slave unit to return to its original connection (#1).

10. A method according to any preceding claim, including, on receipt of a message indicative of connection (#2) of said slave unit (MT) to a next said master unit (AP₂), canceling an attempt by a further said master unit (AP₃) at paging or connecting with said slave unit.

11. A method according to any preceding claim, including operating said master units (AP_1-4) in such a manner that there is substantially no overlap in coverage area between any further master units (AP_2,3) neighboring said currently connected master unit (AP₁), whereby said slave unit (MT) receives identity packets from preferably only its closest further master unit (AP₂).

12. A method according to any preceding claim, including using said network topology information to configure one or more of a group of master units (AP_1-4) with information about which of said master units (AP_1-4) are neighbors and what are their network addresses (MAC), preferably holding said network topology information in the form of a matrix indicating which said master units (AP_1-6) are neighbors, which others are in at least part of the coverage of said network, and preferably storing a said matrix locally to one or more of said master units.

13. A method according to any preceding claim, including gathering said network topology information in an automatic manner, for example by using a mobile probe (MT) adapted to probe said master units (AP_1-6) by activating an inquiry procedure in different positions (A-D) within the coverage of said shared resource network and preferably also adapted to make a record of the response or responses from said master units (AP_1-6) to said inquiries.

15. A method according to any one of claims 1 to 13 or an arrangement according to claim 14, wherein said slave and master units comprise a mobile terminal (MT) and access points (AP_1-4) respectively of said shared resource network, which network comprises for example a Bluetooth local area network (BT LAN).

16. A communications unit (MT) for use as a slave unit in a method or arrangement of any one of the preceding claims, said unit being adapted to send a handoff request to a master unit (AP_1-4) and to advertise its page scan time window in said handoff request, said unit preferably being adapted to enter into a substantially continuous page scan state during said advertised page scan time window and preferably also being adapted to select from a plurality of paging master units (AP_1-4) a particular said master unit (AP₂) for connection therewith.

17. A communications unit (AP₂) for use as a master unit in a method or arrangement according to any one of claims 1 to 15, wherein said master unit (AP₂) is adapted to page a slave unit (MT) during a handoff procedure, said master unit preferably being adapted to hold information about the topology of a shared resource network of which in use it forms a part, for example which master units (AP_1,3,4) are neighbors and what are their addresses (MAC).

18. A communications unit (AP₂) according to claim 17, adapted to accept handoff requests from slave units (MT) or from said shared resource network, preferably also adapted to acknowledge said handoff requests and to forward a received said handoff request to at least one neighboring master unit (AP_2,3) via a shared resource network, said unit preferably being further adapted to schedule paging processes used to attempt connection with a plurality of slave units (MT).

19. A communications unit (AP₁) according to claim 18, wherein, if a number of said handoff requests made from a plurality of slave units (MT) 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 (AP_2-4) acting as master units and, if said communications unit (AP₁) receives from a slave unit (MT) a handoff request which involves a master unit (AP₂) which is congested, said slave unit is informed that it must wait for said handoff, by staying for example in a continuous page scan for an extended period.

20. A communications unit (AP₃) according to any one of claims 17 to 19, wherein said communications unit is adapted to stop paging a particular said slave unit (MT) on or after a message is received indicative of a successful connection between a further communications unit acting as a master unit (AP₂) and said slave unit, said further communications unit (AP₂) preferably being adapted to send an acknowledgment message to at least one master unit (AP_1,3,4) indicative of successful paging of, and preferably also of a successful connection to, a slave unit (MT).

14. A radio communications arrangement for performing a handoff of a currently wireless connected slave unit (MT) from a first master unit (AP₁) of a shared resource network to a further master unit (AP₂) 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 a said handoff a paging procedure in one or more further master units (AP_2-4) based on said topology, in which paging procedure one or more said further master units page said slave unit.