Cognitive Radio Interference Alignment for Spectrum Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional cognitive networks typically avoid interference and do not efficiently utilize shared radio frequency bands, leading to limitations in throughput and spectrum utilization, especially in crowded wireless communication environments.
Innovation Solution
The development of a cognitive coexistence radio system that intentionally creates interference in an intelligent manner by using advanced processing and sensing technologies to adapt transmit-power, carrier-frequency, and modulation strategy in real-time, allowing multiple wireless networks to coexist in the same frequency band without pre-specified coordination protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cognitive networks avoid interference through pre-arranged frequency assignment and coordination protocols, then interference between networks is reduced, but spectrum utilization efficiency and throughput are limited
Solution Approach 1:
The patent applies interference alignment to convert harmful interference into beneficial structured interference. By designing transmit signals such that interference aligns in specific subspaces at unintended receivers, the system transforms random harmful interference into structured interference that can be easily nulled by zero-forcing receivers, thereby enabling high-rate communication without traditional coordination protocols
Solution Approach 2:
The system changes the parameters of transmitted signals (precoding matrices, power allocation) to align interference in specific directions. By dynamically adjusting these parameters based on channel state information, the system achieves interference management without requiring frequency coordination or time slot allocation between different networks
2Reliability
If radios actively sense the spectrum and coordinate to choose unused bands for transmission, then interference is avoided, but system complexity and coordination overhead increase
Solution Approach 1:
The interference alignment system is self-configuring and does not require external coordination. Each transmitter independently computes precoding matrices based on local channel state information, and each receiver independently nulls interference using zero-forcing. This eliminates the need for spectrum sensing coordination and centralized control, reducing system complexity while maintaining interference avoidance
Solution Approach 2:
Instead of avoiding interference by selecting unused frequency bands (traditional cognitive radio approach), the system inverts the approach by deliberately allowing interference in the same band but structuring it through precoding so that it can be easily removed at the receiver. This inversion eliminates the need for frequency coordination protocols
3Productivity
If multiple wireless networks share the same frequency band without coordination, then spectrum utilization improves, but interference increases and reliable communication becomes difficult
Solution Approach 1:
The system segments the signal space into different subspaces using precoding. By dividing the available degrees of freedom into signal subspaces and interference subspaces, the system allows multiple networks to share the same frequency band while maintaining reliable communication through orthogonal signal design and zero-forcing reception
Data Source
AI summary
In a radio network having a plurality of first users on channel (FUOCs) and one or more second users on channel (SUOCs), a method and apparatus for a SUOC to select a channel to co-occupy based upon a “selfish” goal of achieving a desired SUOC rate and an “altruistic” goal of causing low-impact on the FUOC. A SUOC collects signal parameters for a plurality of FUOCs, orders the FUOCs based upon different criteria, and attempts to co-exist with FUOCs until a suitable FUOC channel is found.