Channel access methods and apparatus in low-power wireless communication systems

• US 7,231,221 B2
• Filed: 08/26/2004
• Issued: 06/12/2007
• Est. Priority Date: 09/12/2003
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Aberg, Jan, Haartsen, Jacobus, Assarsson, Mikael
• Primary Examiner(s): LE, DANH C
• Application Number:
  US10/926,854
• Publication Number:
  US 20050064818A1
• Time in Patent Office: 1,020 Days
• Field of Search: 455/458, 455/502, 455/69, 455/550, 455/550.1, 370/509, 370/447, 370/336, 370/390, 370/350, 375/139
• US Class Current: 455/458
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An access scheme in a communication system can deal with a mix of devices having different power constraints and different latency requirements and allow highly asymmetric latency behavior. Such a communication system may include a central control station that broadcasts beacon messages on a communication channel, such as a radio channel, and at least one remote terminal that accesses a communication channel based on the beacon messages. The beacon messages are configured such that individual access to the communication channel by each terminal is controlled according to a grouping of the terminals into respective beacon groups. Each beacon group may have a corresponding beacon message, and beacon messages corresponding to different beacon groups may be broadcast at staggered time intervals.

Claims

1. A communication system, comprising:

a central control station that broadcasts beacon messages on a communication channel; and

at least one remote terminal that accesses a communication channel based on the beacon messages;

wherein the beacon messages provide timing references for the at least one remote terminal, signal a remote terminal that data is waiting in the control station, enable a remote terminal to request access to the communication channel, and are configured such that access to the communication channel by a terminal is controlled according to a grouping of the terminal into a respective beacon group;

remote terminals of a beacon group are permitted to send channel access request messages during an access window following a beacon message corresponding to the beacon group;

the access window includes a plurality of consecutive time slots, and remote terminals are allocated to respective time slots and send channel access request messages during their allocated time slots; and

an allocated time slot, a remote terminal, and a data-pending indication in a beacon message correspond to one another.

2. The system of claim 1, wherein each beacon group has a corresponding beacon message, and beacon messages corresponding to different beacon groups are broadcast at staggered time intervals.

3. The system of claim 2, wherein time intervals between beacon messages corresponding to different beacon groups are different.

4. The system of claim 2, wherein the central control station replaces at least one beacon message corresponding to a first beacon group with at least one beacon message corresponding to a second beacon group.

5. The system of claim 1, wherein time intervals between beacon messages corresponding to a beacon group are selected according to latency requirements for communication from remote terminals in the group to the central control station.

6. The system of claim 5, wherein remote terminals having the same latency requirements are grouped in the same beacon group.

7. The system of claim 6, wherein a remote terminal in a beacon group listens to selected ones of beacon messages corresponding to the beacon group, and the beacon messages are selected according to on the latency requirements for communication from the central control station to the remote terminal.

8. The system of claim 5, wherein a remote terminal in a beacon group listens to at least one beacon message corresponding to another beacon group.

9. The system of claim 1, wherein beacon messages corresponding to a beacon group indicate data is pending transmission for respective remote terminals in the beacon group.

10. The system of claim 9, wherein beacon messages corresponding to a beacon group include bitmaps that indicate data is pending transmission for respective remote terminals in the beacon group.

11. The system of claim 10, wherein a bitmap has a length that depends on a number of remote terminals for which data is pending transmission and a data-pending indication in a beacon message correspond to one another.

12. The system of claim 1, wherein the central control station is a telephone and the remote terminal is a headset.

13. The system of claim 1, wherein the remote terminals include a light switch and a light bulb.

14. The system of claim 1, wherein the remote terminals include a plurality of sensors for measuring at least one of temperature, humidity, and pressure.

15. The system of claim 1, wherein the system is a BLUETOOTH®

system.

16. A terminal for a communication system, comprising:

a transmitter that sends messages through a communication channel;

a receiver that receives messages from the communication channel; and

a controller that operates the transmitter and receiver in response to beacon messages on the communication channel;

wherein the terminal uses beacon messages as a timing reference, as signals that messages are waiting to be received, and to enable the terminal to request access to the communication channel, and the terminal accesses the communication channel according to a grouping of the terminal into a respective beacon group;

the controller operates the transmitter to send a channel access request message during an access window following a beacon message corresponding to the beacon group;

the access window includes a plurality of consecutive time slots;

the terminal is allocated to a respective time slot and sends its channel access request message during its allocated time slot; and

an allocated time slot, the terminal and a data-pending indication in a beacon message correspond to one another.

17. The terminal of claim 16, wherein the beacon group has a corresponding beacon message, and beacon messages corresponding to the beacon group are broadcast at staggered time intervals.

18. The terminal of claim 17, wherein time intervals between beacon messages corresponding to the beacon group are based on latency requirements of the terminal.

19. The terminal of claim 18, wherein the terminal listens to selected ones of beacon messages corresponding to the beacon group, and the beacon messages are selected according to the latency requirements for communication to the terminal.

20. The terminal of claim 16, wherein the terminal listens to at least one beacon message that does not correspond to the beacon group.

21. The terminal of claim 16, wherein the terminal is a headset.

22. The terminal of claim 16, wherein the terminal is one of a light switch and a light bulb.

23. The terminal of claim 16, wherein the terminal is a sensor for measuring one of temperature, humidity, and pressure.

24. The terminal of claim 16, wherein the terminal is one of a keyboard, a mouse, and a game controller.

25. The terminal of claim 16, wherein the terminal is included in a BLUETOOTH®

system.

26. A central control station for a communication system, comprising:

a transmitter configured to send messages through a communication channel;

a receiver configured to receive messages from the communication channel; and

a controller configured to cause the transmitter to broadcast beacon messages on the communication channel;

wherein the beacon messages provide a timing reference, signal that data is waiting in the control station, enable requests for access to the communication channel, and are configured such that access to the communication channel is controlled according to beacon groups, requests for access corresponding to a beacon group are enabled during an access window following a beacon message corresponding to the beacon group;

the access window includes a plurality of consecutive time slots;

requests for access corresponding to the beacon group are allocated to respective time slots; and

a data-waiting indication in a beacon message, an allocated time slot, and an intended recipient of the data correspond to one another.

27. The station of claim 26, wherein each beacon group has a corresponding beacon message, and beacon messages corresponding to different beacon groups are broadcast at staggered time intervals.

28. The station of claim 27, wherein time intervals between beacon messages corresponding to different beacon groups are different.

29. The station of claim 27, wherein at least one beacon message corresponding to a first beacon group is replaced with at least one beacon message corresponding to a second beacon group.

30. The station of claim 26, wherein time intervals between beacon messages corresponding to a beacon group are selected according to latency requirements for communication to the station.

31. The station of claim 26, wherein beacon messages corresponding to a beacon group include bitmaps that selectively indicate data is pending transmission.

32. The station of claim 26, wherein the station is a telephone.

33. The station of claim 26, wherein the station is a terminal in a BLUETOOTH®

system.