Wireless base station to base station synchronization in a communication system, such as a system employing a short-range frequency hopping or time division duplex scheme

• US 7,151,757 B2
• Filed: 05/02/2002
• Issued: 12/19/2006
• Est. Priority Date: 05/02/2001
• Status: Active Grant

• Current Assignee: Aurix Pte., Ltd.
• Original Assignee: Strix Systems Incorporated (AHA Holdings Pvt Ltd.)
• Inventors: Stephens, Spencer, Kuiken, Matthew, Beasley, James, Mergenthal, Wade, Dombrowski, Dennis
• Primary Examiner(s): To, Doris H.
• Assistant Examiner(s): Nguyen, Phuongchau Ba
• Application Number:
  US10/139,130
• Publication Number:
  US 20020187749A1
• Time in Patent Office: 1,692 Days
• Field of Search: None
• US Class Current: 370/331
• CPC Class Codes: H04B 7/2662 Arrangements for Wireless System Synchronisation
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/50 Address allocation
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

In a network, a method is disclosed for wirelessly exchanging communications with at least one mobile unit. The network includes first and second base stations units coupled to the network, and may include a system controller. The method includes: receiving a communication signal from the second base station unit, wherein the first and second base station units are configured to employ a wireless communications protocol, and wherein the wireless communications protocol does not provide for handoff of communications links between base station units; at the first base station unit, determining if the second base station unit has been synchronized based on the communication signal; at the first base station unit, if the second base station unit is synchronized, then synchronizing an internal clock based on the synchronized second base station, wherein the synchronizing is performed without assistance from a system controller.

Claims

1. A system for wirelessly exchanging communications with at least one mobile unit, the system comprising:

more than two base station units coupled to a network;

wherein each base station unit is configured to communicate wirelessly with the mobile unit under a Bluetooth protocol wherein the Bluetooth protocol is a short-range, frequency hopping protocol for transmitting and receiving information during time division duplex pairs of transmit and receive slots, and wherein the pairs of transmit and receive slots repeat over a cycle of n pairs of slots;

wherein each base station unit is further configured to;

synchronize the transmit and receive slots with other base station units, wherein during synchronization, the base station unit;

(a) selects one transmit slot from the n pairs of slots,

(b) converts all transmit slots in the n pairs of slots, wherein n is a positive nonzero integer, except the one selected transmit slot, to receive slots to thereby receive synchronization information from the other base station units,

(c) locks the other base station units from transmitting on the one selected transmit slot,

(d) wirelessly transmits synchronization information during the one selected transmit slot, and

(e) reconvert to the pairs of transmit and receive slots after synchronization;

align the transmit and receive slots with respect to the other base station units based on the synchronization; and

hand-off communications with the mobile unit to one of the other base station units.

2. The system of claim 1 wherein n is 64, wherein each base station unit synchronizes about every 80 milliseconds, wherein each base station unit includes at least first and second base transceiver stations, wherein the first transceiver station has a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , while the second transceiver station has a second transmit and receive pattern of RTRTRT . . . ; and

wherein each base station unit includes;

upper and lower Bluetooth protocol stacks,

a radio environment management component to evaluate quality of links with mobile units and assist in handing off mobile units to a neighboring base station unit, wherein the radio environment management component is configured to operate above a Host Controller Interface (“

HCI”

) under the Bluetooth protocol,

a radio environment monitoring component, configured to operate below the HCI, for monitoring the links with mobile units, wherein the lower layers operate below the HCI; and

wherein the radio environment monitoring component and a baseband layer of the lower Bluetooth protocol stack is configured to, at least in part, convert all of the transmit slots in the n pairs of slots, except the one selected transmit slot, to receive slots.

3. The system of claim 1, further comprising a system controller, wherein each base station unit includes at least first and second base transceiver stations, wherein the first transceiver station has a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , while the second transceiver station has a second transmit and receive pattern of RTRTRT . . . ; and

wherein each base station unit or the system controller commands the first or second base transceiver to switch to the respective second or first pattern.

4. A system for wirelessly exchanging communications with at least one mobile unit, the system comprising:

a first base station unit coupled to a network;

a second base station unit coupled to the network, wherein the first and second base station units are configured to communicate wirelessly with the mobile unit under a short-range wireless protocol for transmitting and receiving information during time division duplex pairs of transmit and receive slots, wherein the pairs of transmit and receive slots repeat over a cycle of n pairs of slots, wherein n is a positive nonzero integer;

wherein the first and second base station units are further each configured for;

synchronizing the transmit and receive slots with respect to the first and second base station units; and

during synchronizing, transmitting synchronization information during one transmit slot of the n pairs of slots, and converting all other transmit slots in the n pairs of slots to receive slots to thereby receive synchronization information with respect to other base stations.

5. The system of claim 4 wherein the first and second base station units are further each configured for:

selecting one of the transmit slots of the n pairs of slots; and

notifying the other base stations that the one transmit slot has been selected.

6. The system of claim 4 wherein each base station unit includes at least first and second base transceiver stations, wherein the first transceiver station has a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , while the second transceiver station has a second transmit and receive pattern of RTRTRT . . . ; and

wherein each base station unit include;

upper and lower Bluetooth protocol stacks,

a radio environment management component to evaluate quality of links with mobile units and assist in handing off mobile units to a neighboring base station unit, wherein the radio environment management component is configured to operate above a Host Controller Interface (“

HCI”

) under the Bluetooth protocol,

a radio environment monitoring component, configured to operate below the HCI, for monitoring the links with mobile units, wherein the lower layers operate below the HCI; and

wherein the radio environment monitoring component and a baseband layer of the lower Bluetooth protocol stack is configured to, at least in part, convert all of the transmit slots in the n pairs of slots, except the one selected transmit slot, to receive slots.

7. The system of claim 4 wherein each base station unit includes at least first and second base transceiver stations, wherein the first transceiver station has a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , while the second transceiver station has a second transmit and receive pattern of RTRTRT . . . .

8. The system of claim 4 wherein each base station unit includes at least first and second base transceiver stations, and wherein each base station unit allocates to each of its transceiver stations either a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . or a second transmit and receive pattern of RTRTRT . . . , based on transmit and receive slot patterns of mobile units requesting to communicate with the base station unit.

9. The system of claim 4, further comprising a system controller, wherein each base station unit includes at least first and second base transceiver stations, wherein the first transceiver station has a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , while the second transceiver station has a second transmit and receive pattern of RTRTRT . . . ; and

wherein the system controller commands the first or second base transceiver to switch to the respective second or first pattern.

10. The system of claim 4 wherein each base station unit includes at least first and second base transceiver stations, and wherein each transceiver station employs an identical transmit (“

T”

) and receive (“

R”

) alternating slot pattern.

11. The system of claim 4 wherein each base station unit includes:

a lower Bluetooth protocol stack;

a radio environment monitoring component, configured to operate below the Host Controller Interface (“

HCI”

), for monitoring links with mobile units; and

wherein the radio environment monitoring component and a baseband layer of the lower Bluetooth protocol stack is configured to, at least in part, convert all of the transmit slots in the n pairs of slots, except the one selected transmit slot, to receive slots only during synchronization operations.

12. The system of claim 4 wherein the first and second base station units receive communication signals under a Bluetooth protocol from mobile units.

13. The system of claim 4 wherein the first and second base station units are stationary relative to a moving vehicle.

14. The system of claim 4 wherein the first and second base station units are stationary.

15. The system of claim 4 wherein the first and second base station units synchronize a clock of the first base station unit with a clock of the second base station unit.

16. The system of claim 4 wherein the first and second base station units are configured to synchronize the transmit and receive slots wirelessly between the first and second base station units.

17. The system of claim 4, further comprising a back-end wired networked coupled to the first and second base station units, and wherein the first and second base station units are configured to synchronize the transmit and receive slots between the first and second base station units through the back-end wired network.

18. A method for wirelessly exchanging communications with at least one mobile unit, the system comprising:

at a first base station unit coupled to a network, initiating synchronization;

at a second base station unit coupled to the network, receiving from the first base station unit a wireless signal under a wireless protocol for transmitting and receiving information during time division duplex pairs of transmit and receive slots, wherein the pairs of transmit and receive slots repeat over a cycle of n pairs of slots wherein n is a positive nonzero integer;

without involvement of a mobile unit, synchronizing the transmit and receive slots with respect to the first and second base station units; and

during synchronizing, transmitting synchronization information during one transmit slot of the n pairs of slots, and converting all other transmit slots in the n pairs of slots to receive slots to thereby receive synchronization information with respect to other base stations.

19. The method of claim 18, further comprising:

selecting one of the transmit slots of the n pairs of slots; and

notifying other base stations that the one transmit slot has been selected.

20. The method of claim 18 wherein each base station unit includes two or more, wherein the method further comprises automatically associating either a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , or a second transmit and receive pattern of RTRTRT . . . to each of the radios.

21. The method of claim 18 wherein the first and second base station units receive communication signals under a Bluetooth protocol from mobile units.

22. The method of claim 18 wherein the first and second base station units are stationary.

23. A computer-readable medium encoded with executable instructions whose instructions cause a short-range wireless communications switch to perform synchronization with a neighboring short-range wireless communications switch in a communications network, the method comprising:

converting all transmit slots in the n pairs of slots, wherein n is a positive nonzero integer, except the one selected transmit slot, to receive slots to thereby receive synchronization information from the other base station units;

wirelessly transmitting synchronization information during the one selected transmit slot; and

reconverting to the pairs of transmit and receive slots after synchronization.

24. The computer-readable medium of claim 23 wherein the computer-readable medium is a logical node in a computer network receiving the contents.

25. The computer-readable medium of claim 23 wherein the computer-readable medium is a computer-readable disk.

26. The computer-readable medium of claim 23 wherein the computer-readable medium is a data transmission medium transmitting a generated data signal containing the contents.

27. The computer-readable medium of claim 23 wherein the computer-readable medium is a memory of a computer system.

28. The computer-readable medium of claim 23, further comprising:

selecting one transmit slot from the n pairs of slots, and

locking the other base stations from transmitting on the one selected transmit slot.

29. In a picocellular communications network, wherein at least one mobile unit communicates with at least a portion of the network, an apparatus comprising:

a stationary wireless network access point coupled to the picocellular communications network, wherein the network access point includes;

a memory,

at least one radio, and

a processor,

wherein the network access point is configured for;

receiving from a neighboring network access point a wireless signal under a wireless protocol for transmitting and receiving information during time division duplex pairs of transmit and receive slots, wherein the pairs of transmit and receive slots repeat over a cycle of n pairs of slots, wherein n is a positive nonzero integer;

without involvement of a mobile unit, synchronizing the transmit and receive slots with respect to the first and second base station units; and

during synchronizing, transmitting synchronization information during one transmit slot of the n pairs of slots, and converting all other transmit slots in the n pairs of slots to receive slots to thereby receive synchronization information for other base stations.

30. The apparatus of claim 29, further comprising:

a system controller coupled to the network access point;

a gateway router coupled to the system controller and the network access point, wherein the network access point forms at least a part of a first subnet;

a backbone router coupled to the gateway router and to the neighboring network access point, wherein the neighboring network access point forms at least a part of a second subnet; and

a point of presence coupled to the backbone router, wherein the point of presence and the mobile unit form at least part of a mobile unit virtual subnet.

31. The apparatus of claim 29 wherein the protocol is a Bluetooth protocol.

32. The apparatus of claim 29 wherein a first radio has a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . , while a second radio has a second transmit and receive pattern of RTRTRT . . . .

33. The apparatus of claim 29 wherein the network access point is configured to allocate each of two or more radios either a first transmit (“

T”

) and receive (“

R”

) alternating slot pattern of TRTRTR . . . or a second transmit and receive pattern of RTRTRT . . . , based on transmit and receive slot patterns of mobile units requesting to communicate with the network access point.

34. The apparatus of claim 29 wherein each of two or more radios employs an identical transmit (“

T”

) and receive (“

R”

) alternating slot pattern.

35. The apparatus of claim 29 wherein the memory includes:

a lower Bluetooth protocol stack,

a radio environment monitoring component, configured to operate below a Host Controller Interface (“

HCI”

), for monitoring links with mobile units; and

wherein the radio environment monitoring component and a baseband layer of the lower Bluetooth protocol stack is configured to, at least in part, convert all of the transmit slots in the n pairs of slots, except the one selected transmit slot, to receive slots only during synchronization operations.