Opportunistic spectrum sensing optimization for a communication system

• US 8,155,033 B2
• Filed: 11/28/2007
• Issued: 04/10/2012
• Est. Priority Date: 11/28/2007
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola Solutions, Inc.
• Inventors: Chaudhri, Apoorv, Rao, Yadunandana N.
• Primary Examiner(s): Pham, Chi H
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US11/946,306
• Publication Number:
  US 20090135744A1
• Time in Patent Office: 1,595 Days
• Field of Search: None
• US Class Current: 370/278
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks

Abstract

A combination of subscriber clustering and link interleaving provides a cognitive radio system (CR) 100 with opportunities to sense an incumbent system'"'"'s spectrum on secondary basis. The CR system (100) uses clustering to identify out-of-band channels. The CR system (100) uses link interleaving during a second mode of operation to sense and detect any incumbent (120) on in-band channels. A list of out-band channels are sensed by clusters (0, 1, 2, 3) sequentially to generate a ranked list of potential channels for future use by the CR system. These out-of-band channels can be used opportunistically in case of in-band incumbent detection.

Claims

1. A secondary communication system seeking to share spectrum with a primary communication system, the secondary communication system comprising:

a plurality of subscriber units; and

a base station communicating with the plurality of subscriber units using first and second operating modes, the second operating mode being used in conjunction with link interleaving to generate in-band sensing opportunities for the plurality of subscribers, wherein the base station groups the plurality of subscribers into a plurality of clusters, the plurality of clusters being sequentially notified of out-of-band sensing opportunities and to perform out-of-band spectrum sensing of the primary communication system'"'"'s channels, and the plurality of clusters send sensed channel data back to the base station, and the base station performs channel ranking based on the sensed channel data.

2. The secondary system of claim 1, wherein the in-band sensing opportunities occur on at least one of an uplink channel or a downlink channel.

3. The secondary system of claim 2, wherein the in-band sensing comprises downlink in-band sensing on the downlink channel or uplink in-band sensing on the uplink channel during the second operating mode.

4. The secondary system of claim 1, wherein the link interleaving comprises at least one of a downlink being interleaved on an uplink channel or an uplink being interleaved on a downlink channel during the second operating mode.

5. The secondary system of claim 1, wherein the base station transmits a notification during the first operating mode to notify the plurality of subscribers to begin in-band sensing.

6. The secondary system of claim 5, wherein the notification identifies the sensing opportunity as occurring on an uplink channel or a downlink channel, a list of in-band channels to be sensed, a starting time for the interleaving, a duration time for the in-band sensing interleaving, and a map designating start and duration time of uplink and downlink in the secondary mode.

7. A secondary communication system seeking to share spectrum with a primary communication system, the secondary communication system comprising:

a plurality of subscriber units; and

a base station communicating with the plurality of subscriber units using first and second operating modes, the second operating mode being used in conjunction with link interleaving to generate in-band sensing opportunities for the plurality of subscribers, the first mode of operation being a Frequency Domain Duplexing (FDD) mode and the second mode of operation being a Time Domain Duplexing (TDD) mode.

8. The secondary system of claim 7, wherein the base station groups the plurality of subscribers into a plurality of clusters, the plurality of clusters being sequentially notified of out-of-band sensing opportunities and to perform out-of-band spectrum sensing of the primary communication system'"'"'s channels.

9. The secondary system of claim 8, wherein the plurality of clusters send sensed channel data back to the base station.

10. The secondary system of claim 9, wherein the base station performs channel ranking based on the sensed channel data.

11. A secondary communication system seeking to share spectrum with a primary communication system, the secondary communication system comprising:

a plurality of subscriber units; and

a base station communicating with the plurality of subscriber units using first and second operating modes, the second operating mode being used in conjunction with link interleaving to generate in-band sensing opportunities for the plurality of subscribers, wherein the base station groups the plurality of subscribers into a plurality of clusters, the plurality of clusters being sequentially notified of out-of-band sensing opportunities and to perform out-of-band spectrum sensing of the primary communication system'"'"'s channels, wherein the clusters are sequentially notified of out-of-band sensing opportunities based on at least one of a current frame number or a beacon number.

12. A secondary communication system seeking to share spectrum with a primary communication system, the secondary communication system comprising:

a plurality of subscriber units; and

a base station communicating with the plurality of subscriber units using first and second operating modes, the second operating mode being used in conjunction with link interleaving to generate in-band sensing opportunities for the plurality of subscribers, wherein the base station groups the plurality of subscribers into a plurality of clusters, the plurality of clusters being sequentially notified of out-of-band sensing opportunities and to perform out-of-band spectrum sensing of the primary communication system'"'"'s channels, wherein the base station notifies the plurality of clusters to switch from the first operating mode to the second operating mode when all of the out-of-band spectrum have been sensed by a predetermined number of clusters, and wherein the plurality of subscribers perform in-band sensing using link interleaving during the second operating mode.

13. A method of a secondary communication system to share spectrum with a primary communication system, the method comprising the steps of:

at the secondary system;

registering subscriber units with a base station;

clustering the subscriber units based on address assignment at the time of registration;

sensing for out-of-band channels within the primary system'"'"'s spectrum while operating in frequency domain duplex (FDD) mode;

generating a ranked list of potential channels based on the sensed out-of-band channels;

notifying the subscriber units to start in-band sensing in response to all the out-of-band channels being sensed by a predetermined number of clusters;

interleaving uplink in-band sensing on a downlink channel using TDD mode;

reverting back to FDD mode when a predetermined uplink in-band sensing time has expired;

interleaving downlink in-band sensing on an uplink in-band channel using TDD mode; and

reverting back to FDD mode when a predetermined downlink in-band sensing time has expired.

14. The method of claim 13, wherein the step of sensing for out-of-band channels comprises the step of sequentially sensing for out-of-band channels within the primary system'"'"'s spectrum while operating in frequency domain duplex (FDD) mode.

15. A cognitive radio (CR) communication system for sharing spectrum with an incumbent communication system, the CR system comprising:

a plurality of subscriber units grouped into a plurality of clusters;

a base station communicating with the plurality of subscribers via frequency division duplexing (FDD) using an uplink frequency and a downlink frequency;

the plurality of clusters performing out-of-band spectrum sensing to detect primary incumbent channels and transmit sensed channel data from the detected incumbent channels back to the base station via the uplink frequency until a predetermined number of channels have been sensed by a predetermined number of the plurality of clusters; and

the base station ranking all the out-of-band spectrum for use in case of in-band incumbent detection on an in-band channel and the base station scheduling all of the plurality of subscribers to change to TDD operation and utilize link interleaving for in-band sensing during a predetermined time interval.

16. The CR system of claim 15, further comprising a controller within the base station and wherein the scheduling of the in-band sensing time interval is determined by the controller.

17. The CR system of claim 15, wherein the scheduling of the in-band sensing is based on at least one of:

the number of in-band channels, type of in-band signals, integration time and subscriber location.

18. A cognitive radio (CR) communication system for sharing spectrum with an incumbent communication system, the CR system comprising:

a plurality of subscribers grouped into a plurality of clusters;

a base station communicating with the plurality of clusters via a frequency domain duplexing (FDD) mode, the base station providing a sequential sensing opportunity to each cluster for out-of-band sensing over a predetermined out-of-band sensing time interval; and

wherein upon a determination that all out-of-band channels are sensed by a predetermined number of clusters, the base station ranks the out-of-band channels;

the plurality of subscribers changing to time domain duplexing (TDD) operation utilizing link interleaving for in-band sensing during a predetermined in-band sensing time interval.

19. The CR system of claim 18, wherein the base station and the plurality of subscribers return to the FDD mode upon the expiration of the predetermined in-band sensing time interval.

20. The CR system of claim 18, wherein the base station sends an in-band sensing opportunity notification to the plurality of subscribers which includes whether the in-band sensing is to be performed on an uplink or downlink frequency, an in-band channel list, sensing duration and link map.

21. The CR system of claim 19, wherein the in-band sensing notification occurs in a downlink channel.

22. The CR system of claim 20, wherein the base station includes a controller providing an in-band sensing scheduler and an out-of-band sensing scheduler for controlling in-band and out-of-band sensing while maintaining uplink and downlink synchronization.

23. The CR system of claim 21, wherein both the base station and plurality of subscribers identify out-of band sensing opportunities for a given cluster (N) of the plurality of clusters.

24. The CR system of claim 22, wherein out-of-band sensing opportunity scheduling is accomplished by the base station broadcasting an out-of-band sensing scheduling data comprising a secondary channel list and out-of-band sensing parameters.

25. The CR system of claim 23, wherein the out-of-band sensing parameters include an out-of-band sensing duration time and an out-of-band channel list to be sensed along with a sensing opportunity divisor (X).

26. The CR system of claim 24, wherein the following equation is used to determine when an out-of-band sensing opportunity for a given cluster (N) of the plurality of clusters arrives:

|FC−

SC|% (4/X)=Y

where;

FC=current beacon or frame number

SC=sensing cluster (0 . . . N)

X=sensing opportunity divisor; and

Y=0-sensing opportunity.