Apparatus and Method for Controlling Channel Switching in Wireless Networks

• US 20090067354A1
• Filed: 12/19/2006
• Published: 03/12/2009
• Est. Priority Date: 01/11/2006
• Status: Active Grant

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Gao, Wen, Liu, Hang
• Granted Patent: US 8,588,115 B2
• Time in Patent Office: Days
• US Class Current: 370/310
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

The invention provides apparatus methods for avoiding channel collisions in Wireless Regional Area Networks (WRAN), A medium access controller (MAC) for switching a base station (BS) of a WRAN from a first channel to a second channel at a time t is provided. The MAC includes a switch time delay circuit for delaying said switching with respect to time t by a random delay time.

Claims

1. A channel switch delay circuit for use in a node of a wireless communication network comprising a medium access controller (MAC) coupled to a transceiver to switch said transceiver from a first channel to a second channel at a time t, said circuit comprising:

a processor coupled to said medium access controller (MAC) to receive an indication of said switch;

a random delay time circuit coupled to said processor to provide a random delay time (t_rwait) in response to receiving said indication;

said processor delaying said switch of said transceiver with respect to said time t by said random delay time (t_rwait).

2. The channel switch delay circuit of claim 1 wherein said transceiver comprises a base station (BS) of a wireless regional area network (WRAN) and said medium access controller (MAC) cooperates with a cognitive radio (CR) to sense occupancy of said first channel, said processor coupled to said MAC and to said transceiver to switch said transceiver in response to sensed occupancy of said first channel at a time delayed from said time t by said random delay time (t_wait).

3. The circuit of claim 1 wherein said random delay time circuit includes a random number generator coupled to said processor to generate a random number in response to a signal received from said processor, said processor providing said signal to said random number generator in response to said indication of said switch.

6. The controller of claim 1 including at least one counter coupled to said processor, said counter defining a time window for said random delay time, said time window comprising at least one of a maximum wait time (t_max) and a minimum wait time (t_min), said processor configured to randomly select a wait time from times within said time window.

10. The controller of claim 1 including at least one counter defining a time window, said time window comprising at least one of a maximum wait time (t_max) and a minimum wait time (t_min), said processor configured to randomly select a wait time from times within said time window.

11. The controller of claim 1 wherein said base station further includes a channel occupancy sensor coupled to said processor, said processor configured to select a second channel from a candidate channel list if said channel occupancy sensor indicates occupancy of said first channel before expiration of said random wait timer.

4. A medium access controller for switching a BS of a wireless regional area network from a first channel to a second channel at a time t, said controller including a switch time delay circuit for delaying said switching with respect to time t by a random delay time.

5. The medium access controller of claim 4 wherein said base station includes a channel occupancy sensor coupled to said medium access controller to provide an indication of occupancy of said first channel, said medium access controller coupled to said switch time delay circuit for initiating said switching in response to said indication by a randomly generated switch time.

7. A method for controlling channel switching in a BS of a wireless regional area network comprising the steps of:

establishing a communication link between said base station and at least one CPE comprising a first air channel;

deciding to switch said communication link from said first air channel to a second air channel;

generating a random number in response to said deciding step;

generating a time t for switching to said second channel based on said random number;

announcing said time t to said at least one CPE;

switching said base station from said first channel to said second channel at said time t, wherein a step of sensing said second channel for occupancy is carried out after said deciding step and before said switching step.

8. A method for controlling channel switching of a transceiver comprising the steps of:

deciding to switch said transceiver from a first channel to a second channel;

switching to said second channel after a random time delay.

9. The method for controlling channel switching of claim 8 further comprising steps of:

generating a random number after carrying out said deciding step;

determining said random time delay based on said random number.

12. A medium access controller (MAC) for use in frequency hopping (FH) wireless regional area network (WRAN) said MAC comprising:

a processor configured to select a next hop channel for a wireless regional area network (WRAN) system;

a random delay time generator coupled to said processor to generate a random delay time in response to selection of said next hop channel by said processor;

said wireless regional area network (WRAN) hopping to said next hop channel after expiration of said random delay time.

13. The controller according to claim 12 wherein said WRAN further includes a spectrum sensor coupled to said processor to sense said next hop channel for occupancy status after said random time delay expires and to provide an indication of said occupancy status to said processor;

said transmitter responsive to said indication of said occupancy status to switch to said next hop channel if said indication of said occupancy status indicates said next hop channel is unoccupied;

said transmitter responsive to said indication to select a different next hop channel if said occupancy status indicates said next hop channel is occupied.

14. A node of a wireless network including a radio frequency transmitter operable to transmit radio signals on at least one channel selectable from a plurality of channels of a wireless transmission medium, the node comprising;

a receiver operable to receive a channel switch command at an input;

a random number generator coupled to said input and providing a random number in response to receiving said channel switch command;

a processor coupled to said random number generator to receive said random number and to provide a channel switch time based upon said random number;

said transmitter configured to transmit a radio signal comprising said channel switch time to at least one other node of said wireless network.

15. The radio frequency transmitter of claim 14 wherein said transmitter further comprises a memory storing at least a candidate channel list and wherein said processor is configured to receive a candidate channel from said list and to provide a candidate channel to said transmitter, said radio signal further comprising said candidate channel.

16. The radio frequency transmitter of claim 15 wherein said memory is coupled to said receiver.

17. A radio frequency receiver comprising:

a radio frequency front end tunable to receive radio signals comprising a channel switch command including a random switch time signal on a channel of a transmission medium;

a channel switching processor coupled to said radio frequency front end to receive said channel switch command including said random switch time signal and to tune said radio frequency front end at a time determined by said channel switch time signal.

18. A radio frequency transceiver comprising:

a radio frequency front end operable to transmit and receive radio signals on a channel of a transmission medium;

a random number generator;

a channel switch processor including an input for receiving a channel switch command, said channel switch processor coupled to said random number generator to receive a random number and configured to provide a randomly generated switch time signal based upon said random number in response to said channel switch command;

said radio frequency front end configured to transmit a radio signal comprising said randomly generated switch time signal.

19. The transceiver of claim 18 wherein said radio frequency front end includes tuning circuits coupled to said channel switch processor, said processor further configured to change said same channel in accordance with said random time switch signal.

20. A wireless network comprising:

at least a first and second wireless transceivers comprising respective radio frequency front ends operable to transmit and receive radio signals on a same channel of a wireless transmission medium;

said first wireless transceiver comprising;

a random number generator;

a channel switch processor including an input for receiving a channel switch command, said channel switch processor coupled to said random number generator to receive a random number and configured to provide a randomly generated switch time for said same channel based upon said random number in response to said channel switch command;

said radio frequency front end configured to transmit a radio signal comprising said randomly generated switch time signal.

21. The method of claim 20 further comprising a step of selecting a channel comprising said second channel.

22. The method of claim 21 wherein said step of selecting a channel includes a step of sensing at least a portion of an RF spectrum for channel occupancy.

23. The method of claim 21 wherein the step of selecting a channel includes steps of:

storing a list of candidate channels in a memory;

selecting a second channel from said stored list of candidate channels.

24. The method of claim 21 wherein the step of storing a list of candidate channels in a memory includes steps of:

receiving at least one channel broadcast schedule from at least one source of channel broadcast schedules;

compiling said list of candidate channels based at least in part on said at least one received channel broadcast schedule;

storing said compiled list of candidate channels in said memory.

25. The method of claim 23 wherein the step of storing a list of candidate channels in a memory includes steps of:

receiving channel information from at least one user node of said network;

compiling said list of candidate channels based at least in part on said received channel information;

storing said compiled list of candidate channels in said memory.