METHOD FOR OPTIMIZING SPATIAL DIVERSITY GAIN OF A SET OF NODES USED FOR COOPERATIVE SENSING

• US 20100329180A1
• Filed: 06/30/2009
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rao, Surhir, Rao, Yadunandana N., Chaudhri, Apoorv
• Granted Patent: US 8,160,004 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks

Abstract

A group of nodes used for sensing in a cooperative sensing communication system (100) are selected from nodes (104-112) associated with a base station (102) operating in secondary communication mode. The group has a spatial diversity gain, as determined by a cooperative sensing index (306) that initially meets a minimum threshold. To optimize the spatial diversity gain, nodes not in the initial set are individually added to the set (408), and the index is recomputed (608). The additional node having the highest effect on spatial diversity is added to the group (614). To maintain group size, each of the original nodes is individually removed from the group (706) and the index is recomputed (708) with each initial node removed to determine which of the initial nodes provided the smallest spatial gain contribution, and is removed from the group (714).

Claims

1. A method for optimizing spatial diversity of a set of nodes for cooperative spectrum sensing, comprising:

selecting an initial set of nodes from a plurality of nodes, the initial set of nodes selected substantially at random from the plurality of nodes;

obtaining sensing results from each node of the initial set of nodes, the sensing results produced by the nodes in response to performing a cooperative sensing regime;

determining an initial cooperative sensing index of the initial set of nodes based on the sensing results, the initial cooperative sensing index indicating a level of spatial diversity of the initial set of nodes, wherein the initial cooperative sensing index satisfies a minimum spatial diversity criteria;

selecting at least one additional node from a remaining set of nodes, the remaining set of nodes consisting of nodes in the plurality of nodes not in the initial set of nodes, wherein the at least one additional node is selected substantially at random from the remaining nodes; and

replacing at least one node in the initial set of nodes with the at least one additional node to produce an optimized set of nodes, the optimized set of nodes having an increased cooperative sensing index that is higher than the initial cooperative sensing index.

2. The method of claim 1, wherein the method is performed for at least a first radio frequency and a second radio frequency, and wherein the optimized set of nodes for the first radio frequency and the optimized set of nodes for the second radio frequency are determined independent of each other.

3. The method of claim 1, wherein selecting nodes of the initial set and the remaining set are performed by selecting node that are substantially fixed in location.

4. The method of claim 1, wherein selecting at least one additional node is performed by determining a cooperative sensing index of the initial set of nodes when sensing results of each one of the at least one additional nodes is included individually in the determination of the cooperative sensing index, and determining which additional node increases the cooperative sensing index most over the initial cooperative sensing index.

5. The method of claim 4, wherein replacing at least one node is performed by including the additional node which increased the cooperative sensing index most, and individually removing each node of the initial set of nodes and determining the cooperative sensing index with each node of the initial set of nodes removed individually, and determining which node of the initial set of nodes which, when removed, has a lowest effect on the cooperative sensing index.

6. The method of claim 1, wherein determining the initial and optimized cooperative sensing index are performed based on sensing results provided by each node of the initial set of nodes and the at least one additional node when they are sensing a common reference signal.

7. The method of claim 1, further comprising using the optimized set of nodes to sense secondary channel availability for a secondary communication operation.

8. A method for optimizing a sensing set of nodes for use in cooperative sensing secondary channel availability, comprising:

selecting an initial set of nodes from a plurality of nodes associated with a base station to form a sensing set of nodes, the initial set of nodes having a cooperative sensing index that at least meets a minimum cooperative sensing index criteria;

selecting an additional set of nodes, the additional set of nodes consisting of at least one node from the plurality of nodes not in the initial set of nodes;

determining a cooperative sensing index delta for each one of the additional nodes when each of the additional nodes is individually added to the sensing set of nodes and identifying a leader node among the additional nodes which yields a highest cooperative sensing index delta when added to the sensing set;

adding the leader node to the sensing set of nodes;

determining a cooperative sensing index delta for each node of the initial set of nodes when individually removed from the sensing set of nodes with the leader node added to the sensing set and identifying which node of the initial set of nodes yields a lowest cooperative sensing index delta when removed from the sensing set; and

removing the node of the initial set of nodes which yields the lowest cooperative sensing index delta from the sensing set;

wherein the cooperative sensing index is based on radio sensing results provided by each node of the sensing set, and wherein the sending results are obtained by each node in the sensing set by performing a sensing regime provided by the base station to each node in the sensing set.

9. The method of claim 8, further comprising iteratively repeating the method of claim 8 until the sensing set of nodes yields a desired cooperative sensing index, and wherein selecting the initial set comprises selecting the nodes of the sensing set produced by a most recent iteration of the method.

10. The method of claim 8, wherein the method is performed for at least a first radio frequency and a second radio frequency, and wherein the sensing set of nodes for the first radio frequency and the sensing set of nodes for the second radio frequency are determined independent of each other.

11. The method of claim 8, wherein the sensing regime comprises identification of a common reference signal to be sensed by each of the nodes.

12. The method of claim 8, wherein each of the sensing nodes are substantially fixed in location.

13. The method of claim 8, further comprising repeating the method of claim 8 upon occurrence of a predefined event.

14. The method of claim 13, wherein the predefined event is a passage of a preselected period of time.

15. The method of claim 8, wherein the initial set of nodes comprises two nodes, the method further comprises repeating selecting an additional set of nodes, determining a cooperative sensing index delta for each one of the additional nodes, and adding the leader node, increasing the number of nodes in the sensing set until a desired cooperative sensing index is reached.

16. A secondary communication system, comprising:

a plurality of nodes;

a base station configured to provide a radio interface to each of the plurality of nodes, and further configured to define a set of sensing nodes from the plurality of nodes by receiving sensing results of performing a sensing regime from an initial set of nodes having an initial cooperative sensing index, and replacing nodes in the initial set of nodes with other nodes from the plurality of nodes which increase the cooperative sensing index of the set over nodes of the initial set which are removed from the initial set to achieve a desired cooperative sensing index which is higher than the initial cooperative sensing index.

17. The secondary communication system of claim 16, wherein the base station defines different sets of nodes to be used at different frequencies for cooperative sensing at those different frequencies.

18. The secondary communication system of claim 16, wherein each of the nodes are substantially fixed in location.

19. The secondary communication system of claim 16, wherein the sensing regime comprises identification of a common reference signal to be sensed by each of the nodes.