Orthogonal Frequency Code Assignment for Licensed-Unlicensed Spectrum Sharing
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Solution Overview
Problem
Licensed and unlicensed communications devices struggle to coexist in the same spectrum without interfering with each other, particularly in underutilized licensed spectrum like the television broadcast band, where licensed devices must not be disrupted while unlicensed devices seek to utilize unused bandwidth for high-speed broadband access.
Innovation Solution
A method and system that utilize orthogonal sequences for spreading and despreading data, allowing licensed and unlicensed devices to share the same frequency band by selecting appropriate orthogonal sequences for transmission, with primary and secondary protecting devices managing communications to prevent interference and enable efficient use of bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If licensed devices use licensed spectrum exclusively to avoid interference, then communication reliability is improved, but spectral efficiency deteriorates due to underutilization of available bandwidth
Solution Approach 1:
The licensed spectrum is segmented into multiple orthogonal frequency codes (OFCs) that can be independently assigned to different devices. This segmentation allows multiple licensed devices to share the same frequency band simultaneously without interfering with each other, thereby improving spectral efficiency while maintaining communication reliability through orthogonal separation
Solution Approach 2:
The patent introduces a new dimension of orthogonal frequency coding in the frequency domain, transforming the traditional single-frequency licensed communication into multi-frequency code-based communication. This dimensional expansion enables multiple devices to coexist in the same licensed band by assigning them different orthogonal frequency codes, thus resolving the contradiction between reliability and spectral efficiency
2Productivity
If unlicensed devices operate in unused licensed spectrum to improve broadband access, then productivity is improved, but interference to licensed devices occurs
Solution Approach 1:
The patent introduces an intermediary mechanism of orthogonal frequency code assignment and protection devices that mediate between unlicensed broadband access devices and licensed devices. The protection devices monitor the spectrum and coordinate orthogonal code usage, allowing unlicensed devices to access unused licensed bandwidth while preventing interference to licensed communications through coordinated resource allocation
Solution Approach 2:
The patent changes the operational parameters of licensed spectrum by introducing orthogonal frequency codes as an additional modulation dimension. This parameter change allows unlicensed devices to operate in the same spectrum by using different orthogonal code combinations, transforming the harmful interference scenario into a coordinated multi-access system that improves broadband access without disrupting licensed services
3Productivity
If multiple wireless networks operate in the same region to utilize underused spectrum, then spectral efficiency is improved, but system complexity increases due to interference management
Solution Approach 1:
The patent creates a universal orthogonal frequency code framework that can be applied across multiple wireless networks operating in the same region. This universal coding scheme provides a standardized method for frequency allocation and interference avoidance that can be implemented by different networks, enabling them to coexist efficiently without requiring complex proprietary interference management systems, thus improving spectral efficiency while controlling system complexity
4Productivity
If licensed spectrum is fully utilized to improve broadband availability, then productivity is improved, but interference to existing licensed communications occurs
Solution Approach 1:
The patent implements preliminary action by pre-assigning orthogonal frequency codes to licensed devices before unlicensed devices access the spectrum. This preliminary code allocation establishes a protected framework that guides subsequent unlicensed device access, ensuring that new broadband devices can utilize the spectrum fully while automatically avoiding interference through pre-coordinated orthogonal code assignment
Data Source
AI summary
System and method for enabling the cohabitation of licensed and unlicensed communications devices. A method comprises at a receiver, receiving transmitted data, demodulating the transmitted data to produce spread symbols, despreading the spread symbols to produce received data, wherein the despreading comprises using an orthogonal sequence selected from a list of orthogonal sequences for use by all transmissions in the wireless network, and processing the received data.