METHOD AND APPARATUS FOR OPTIMIZING SPECTRUM UTILIZATION BY A COGNITIVE RADIO NETWORK

• US 20100081449A1
• Filed: 09/30/2008
• Published: 04/01/2010
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Simms, Matthew E., Rao, Yadunandana N., Chaudhri, Apoorv, Gurney, David P., Kuffner, Stephen L.
• Granted Patent: US 8,140,085 B2
• Time in Patent Office: Days
• US Class Current: 455/452.200
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 8/205 Transfer to or from user equipment or user record carrier

Abstract

A technique for a secondary communication system to utilize spectrum designated to another (or primary) communication system is provided. By ranking a plurality of secondary base stations based on base station transmit power, calculated required transmit power and path loss, a set of criteria is developed for selecting a highest ranked secondary base station for operation within a primary'"'"'s spectrum. The ranking may be adapted based on mobility of the secondary'"'"'s subscriber; and as such the secondary system communicates within the primary'"'"'s spectrum using the adaptively ranked base stations. Channel selection may also be ranked. The technique and apparatus allows a cognitive radio (CR) network to operate within an incumbent network'"'"'s spectrum.

Claims

1. A method for selecting a communications channel in a CR system, comprising the steps of:

determining a maximum allowed transmit power level on each of a plurality of candidate channels;

measuring a power level on each of the plurality of candidate channels;

computing an estimated link budget for each candidate channel, wherein the estimated link budget comprises a difference between the maximum allowed transmit power level and the corresponding measured power level for the candidate channel; and

selecting the channel that has the highest estimated link budget for communications.

2. The method of claim 1, wherein the step of determining a maximum allowed transmit power level is determined using geo-location information.

3. The method of claim 1, wherein the step of determining a maximum allowed transmit power level is determined using sensing information.

4. A method for selecting a cognitive radio (CR) channel, comprising the steps at a CR mobile subscriber:

scanning frequency bands to determine the availability of one or more CR base stations at the location of the CR mobile subscriber;

determining a transmit power level for each available CR base station;

measuring a received power level for each available CR base station;

computing an estimated link budget for each candidate channel, wherein the estimated link budget comprises a difference between the transmit power level of the CR base station and the corresponding measured received power level for the CR base station;

calculating required transmit power by the CR mobile subscriber to reach each CR base station and avoid interference to identified incumbents;

ranking the CR base stations based on the estimated link budget, required transmit power and maximum allowed transmit power level of the CR mobile subscriber; and

selecting and utilizing a highest ranked CR base station and channel for transmission from the CR mobile subscriber.

5. The method of claim 4, wherein the step of calculating required transmit power by the CR mobile subscriber comprises determining the transmit power level required to achieve a target received signal strength indicator (RSSI) level at the CR base station.

6. The method of claim 4, wherein the step of calculating required transmit power by the CR mobile subscriber further comprises adjusting transmit power levels in proportion to local CR base site noise floor levels per channel.

7. The method of claim 4, wherein the step of determining the CR base stations transmit power level is based on a geo-location of each available base station.

8. The method of claim 4, wherein the maximum allowed CR mobile subscriber transmit power level is determined via geo-location of the CR mobile subscriber.

9. The method of claim 4, wherein the maximum allowed CR mobile subscriber transmit power level is determined via spectral sensing.

10. The method of claim 4, wherein base site noise floor levels are broadcast to the CR mobile subscriber and taken into account during the step of ranking along with the local noise level measured at the mobile.

11. A communication system, comprising:

a primary system operating under regulated spectrum;

a database containing regulation and geo-location information pertaining to the primary system;

a secondary system having a secondary subscriber and a plurality of secondary base stations, the secondary system seeking to utilize the regulated spectrum; and

the secondary subscriber selecting one of the plurality of secondary base station channels for operation within the primary system'"'"'s spectrum based on secondary base station rankings, the secondary base station rankings being based on a maximum allowed transmit power level in conjunction with active or passive channel measurements of the secondary system.

12. The communication system of claim 11, wherein the maximum allowed transmit power level is determined based on the geo-location information.

13. The communication system of claim 11, wherein the secondary system comprises a public safety network seeking to utilize TV white space spectrum.

14. The communication system of claim 11, wherein the secondary base station rankings are periodically updated in response to mobility of the secondary subscriber.

15. The communication system of claim 14, wherein the database containing regulation and geo-location information pertaining to the primary system further includes location information pertaining to the mobility of the secondary subscriber capable of providing updated regulatory and spectrum information based on change in location of the secondary subscriber.

16. A method for optimizing spectrum sharing amongst cognitive radio systems and incumbent systems, comprising:

scanning the spectrum for CR base stations by a CR subscriber;

detecting the presence of a plurality of CR base stations;

ranking the plurality of CR base stations by the CR subscriber based on CR base station transmit power, required transmit power of the CR subscriber to reach each CR base station and estimated link budgets, wherein estimated link budgets are based on path loss between the CR subscriber and each CR base station of the plurality of base stations and local noise levels;

selecting a CR base station from the ranked CR base station

detecting mobility of the CR subscriber and re-ranking the plurality of CR base stations based on the mobility of the CR subscriber; and

maintaining CR subscriber communication within the incumbent spectrum by switching base stations when the detected mobility meets predefined criteria.

17. The method of claim 16, wherein the step of detecting mobility of the CR mobile subscriber is based on at least one of:

power of the CR subscriber dropping below that needed to reach the CR base station, a drop in signal quality on the current operating channel, and receiving a change in location information from a geo-location database.

18. The method of claim 16, wherein the CR base station transmit power is stored in a database.

19. A method for optimizing spectrum sharing amongst cognitive radio (CR) systems and incumbent systems, comprising:

ranking a plurality of CR base stations based on base station transmit power, calculated required CR transmit power;

selecting a highest ranked CR base station for operation within the incumbent'"'"'s spectrum;

adapting the ranking based on mobility of the CR subscriber; and

the CR system communicating within the incumbent'"'"'s spectrum using the adaptively ranked CR base station.

20. The method of claim 19, wherein the ranking is further based on signal to interference plus noise ratios (SINR) and local noise levels at the CR base station and at the CR subscriber.