Cooperative Spectrum Sensing Group Selection for Spatial Diversity

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Solution Overview

Problem

Cooperative spectrum sensing in cognitive radio networks becomes inefficient due to correlated fading or shadowing effects, leading to reduced interference protection for primary users.

Innovation Solution

A technique that selects a group of cooperating nodes to achieve spatial diversity gain without requiring location information, estimating a cooperative sensing metric, and validating it to ensure sufficient spatial diversity for primary user detection, allowing secondary users to communicate on unused channels without interfering with primary systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cooperative spectrum sensing is used to increase detection probability of primary users, then interference protection to primary users is improved, but network efficiency deteriorates when correlated fading or shadowing effects are present

Engineering Contradiction:

Improvedetection probability of primary usersVSAvoidnetwork efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the cooperative sensing network into multiple groups of secondary users, where each group independently performs spectrum sensing. This segmentation allows the system to maintain high detection probability by having multiple independent sensing units, while avoiding the inefficiency of correlated fading affecting the entire network simultaneously. Each group can make independent decisions about channel usage, improving overall network efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by having each group of secondary users perform spectrum sensing independently based on their local conditions. Each group evaluates the spectrum status locally without being influenced by correlated fading effects in other groups. This local independence ensures that detection reliability is maintained while network efficiency is improved through localized decision-making.

Inventive Principle:

Principle #3Local quality

2Reliability

If more cooperating nodes are used to improve detection reliability, then spatial diversity gain is improved, but device complexity increases

Engineering Contradiction:

Improvespatial diversity gainVSAvoidnumber of cooperating nodes

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies partial action by using a limited number of cooperating nodes per group rather than requiring all secondary users to participate. Each group is formed with a specific number of nodes that provides sufficient spatial diversity gain without excessive complexity. The system achieves reliable detection with a manageable number of cooperating nodes, balancing reliability and device complexity.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS8135424B2Method to improve diversity gain in a cooperative spectrum sensing network

Publication Date: 2012.03.13 MOTOROLA SOLUTIONS INC

AI summary

A cooperative sensing technique (300) operates by selecting a group of subscribers (302) from a secondary system, measuring a cooperative sensing metric (306) and then using the metric to identify an achievable spatial diversity gain for the group of selected subscribers (308). Once an achievable spatial diversity gain is determined for the group (308/412), it is compared to a required spatial diversity gain (310), and if the condition is met at (310), the validated group can begin spectrum sensing (314) to identify a vacant/suitable channel for operation. If the achievable spatial diversity gain is insufficient, then a new group of users is selected (312) within the secondary system and the process repeats itself.