Method, apparatus and computer program for self-adjusting spectrum sensing for cognitive radio

• US 20090252178A1
• Filed: 04/03/2008
• Published: 10/08/2009
• Est. Priority Date: 04/03/2008
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Huttunen, Anu Hannele, Junell, Jari, Pihlaja, Juha Hermanni
• Granted Patent: US 7,885,229 B2
• Time in Patent Office: Days
• US Class Current: 370/445
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

A cognitive radio determines a frequency channel of a spectrum, determines from a locally stored association of individual channels to either of at least two categories (e.g., in use and backup, other is a third category) a selected category for the determined frequency channel. From the selected category is determined a time at which to sense the determined frequency channel. The determined frequency channel is then sensed at the determined time and results of the sensing may be transmitted. Timers may be associated with each of the categories and adjusted based on density of cognitive nodes. A timer for the in use category is shortest, a timer for the other category is longest, and a timer for the backup category is between shortest and longest.

Claims

1. A method comprising:

determining a frequency channel of a spectrum;

determining, from a locally stored association of individual channels to one of at least two categories, a selected category for the determined frequency channel;

determining from the selected category a time at which to sense the determined frequency channel; and

sensing the determined frequency channel at the determined time

2. The method of claim 1, further comprising receiving information on which channels are in use and which channels are backup, and locally storing an association of the channels in use with one of the at least two categories and an association of the backup channels with another of the at least two categories and thereafter determining from the locally stored association whether the determined frequency channel is in use, backup, or other.

3. The method of claim 2, wherein the determined time is sooner for the case where the selected category is “

in use”

, and the determined time is later for the case where the selected category is “

backup”

, and the determined time is later than the “

backup”

category for the case where the selected category is “

other”

.

4. The method of claim 1, wherein determining from the selected category the time at which to sense the determined frequency channel comprises sensing at expiration of a timer associated with the selected category.

5. The method of claim 4, wherein for the case the selected category is “

in use”

the associated timer expires upon each sensing time instance, and for the case the selected category is “

backup”

the associated timer expires after a plurality of sensing time instances that equals the number of the individual channels.

6. The method of claim 1, further comprising:

transmitting the results of the sensing, wherein transmitting is at a first time for the case that the selected category is a first of the at least two categories and at a second time that is later than the first time for the case that the selected category is a second of the at least two categories.

7. The method of claim 6, wherein transmitting the results of the sensing comprises transmitting only those results of the sensing that exceed a censoring threshold.

8. The method of claim 1, further comprising determining a node density in a cognitive radio network,

and wherein the time at which to sense the determined frequency channel is determined from the selected category and from the determined node density.

9. The method of claim 8, wherein determining the node density comprises estimating the node density from how many spectrum sensing results are received from other nodes in the cognitive radio network.

10. The method of claim 9, wherein the node density is estimated for the selected category by averaging received spectrum sensing results for all channels of the selected category.

11. The method of claim 8, further comprising receiving power control information,

and wherein determining the node density comprises estimating the node density for a geographical area from the received power control information and from a hop count.

12. The method of claim 8, further comprising transmitting timer values for timers associated with each of the at least two categories and receiving timer values from other nodes for the other nodes'"'"' timers associated with each of the at least two categories,

and wherein determining the node density comprises estimating the node density from the received timer values.

13. An apparatus comprising a processor, a memory and a receiver that are configured to determine a frequency channel of a spectrum, to determine a selected category for the determined frequency channel from an association stored in the memory of individual channels to one of at least two categories, to determine from the selected category a time at which to sense the determined frequency channel, and to sense the determined frequency channel at the determined time.

14. The apparatus of claim 13, wherein the receiver is configured to receive information on which channels are in use and which channels are backup, and the memory is configured to store an association of the channels in use with one of the at least two categories and to store an association of the backup channels with another of the at least two categories, and the processor is configured to thereafter determine from the locally stored association whether the determined frequency channel is in use, backup, or other.

15. The apparatus of claim 14, wherein the determined time is sooner for the case where the selected category is “

in use”

, and the determined time is later for the case where the selected category is “

backup”

, and the determined time is later than the “

backup”

category for the case where the selected category is “

other”

.

16. The apparatus of claim 13, wherein the processor is configured to determine from the selected category the time at which the apparatus is to sense the determined frequency channel by sensing at an expiration of a timer that is associated with the selected category.

17. The apparatus of claim 16, wherein for the case that the selected category is “

in use”

the associated timer expires upon each sensing time instance, and for the case the selected category is “

backup”

the associated timer expires at after a plurality of the sensing time instances that equals the number of the individual channels.

18. The apparatus of claim 13 further comprising a transmitter, and wherein the apparatus is configured to transmit the results of the sensing at a first time for the case that the selected category is a first of the at least two categories and at a second time that is later than the first time for the case that the selected category is a second of the at least two categories.

19. The apparatus of claim 18, wherein the apparatus is configured to compare the results of the sensing to a censoring threshold and to transmit only those results of the sensing that exceed the censoring threshold

20. The apparatus of claim 13, further configured to determine a node density in a cognitive radio network,

and wherein the apparatus is configured to determine the time at which to sense the determined frequency channel from the selected category and from the determined node density.

21. The apparatus of claim 20, wherein the apparatus is configured to determine the node density by estimating the node density from how many spectrum sensing results the receiver receives from other nodes in the cognitive radio network.

22. The apparatus of claim 21, wherein the apparatus is configured to estimate the node density for the selected category by averaging received spectrum sensing results for all channels of the selected category.

23. The apparatus of claim 20, wherein the receiver is further configured to receive power control information,

and wherein the apparatus is configured to determine the node density by estimating the node density for a geographical area from the received power control information and from a determined hop count.

24. The apparatus of claim 20 further comprising a transmitter, wherein the transmitter is configured to transmit timer values for timers associated with each of the at least two categories and the receiver is configured to receive timer values from other nodes for the other nodes'"'"' timers associated with each of the at least two categories,

and wherein the apparatus is configured to determine the node density by estimating the node density from the received timer values.

25. A computer readable memory embodying a program of machine-readable instructions executable by a digital data processor to perform actions directed toward selecting a time at which to sense a channel of a spectrum, the actions comprising:

determining a frequency channel of a spectrum;

determining, from a locally stored association of individual channels to one of at least two categories, a selected category for the determined frequency channel;

determining from the selected category a time at which to sense the determined frequency channel; and

sensing the determined frequency channel at the determined time.

26. The computer readable memory of claim 25, wherein determining from the selected category the time at which to sense the determined frequency channel comprises sensing at expiration of a timer associated with the selected category.

27. An apparatus comprising processing means, storage means and receiving means, arranged for determining a frequency channel of a spectrum, for determining a selected category for the determined frequency channel from an association stored in the storage means of individual channels to one of at least two categories, for determining from the selected category a time at which to sense the determined frequency channel, and for sensing the determined frequency channel at the determined time

28. A method comprising:

determining a density of cognitive radio nodes operating in a cognitive radio network;

selecting at least one of a channel to sense and a time at which to sense a channel based at least in part on the determined node density; and

sensing a portion of a cognitive radio spectrum according to the selection.