Guard Band Insertion for CBRS Adjacent Channel Interference

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Solution Overview

Problem

In Citizens Broadband Radio Service (CBRS) systems, TDD unsynchronized CBSDs can cause interference due to asynchronous transmission and reception, leading to desensitization of receivers, especially when operating on adjacent frequency spectrums without sufficient guard bands.

Innovation Solution

A program product is provided that determines pairs of adjacent frequency spectrums and inserts a guard band between them to prevent interference, ensuring that one end of one frequency spectrum is no longer within a predefined threshold frequency of another, thereby reducing desensitization and maintaining acceptable interference levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If TDD unsynchronized CBSDs operate on adjacent frequency spectrums without guard bands, then spectrum utilization efficiency is improved, but receiver desensitization and interference increase

Engineering Contradiction:

Improvespectrum utilization efficiencyVSAvoidreceiver desensitization

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a guard band as an intermediary frequency spectrum between adjacent frequency spectrums used by TDD unsynchronized CBSDs. This guard band acts as a buffer that absorbs and isolates interference, preventing receiver desensitization while allowing efficient spectrum utilization. The guard band is inserted between frequency spectrums where CBSDs are not synchronized, creating a protective barrier without significantly reducing overall spectrum usage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If guard bands are inserted between adjacent frequency spectrums, then interference between TDD unsynchronized CBSDs is reduced, but spectrum bandwidth is consumed

Engineering Contradiction:

Improveinterference reductionVSAvoidspectrum bandwidth

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies guard bands selectively and locally rather than universally. Specifically, guard bands are inserted only between adjacent frequency spectrums where TDD unsynchronized CBSDs operate, and only when interference thresholds would be exceeded. This localized approach ensures interference reduction is applied precisely where needed, minimizing the total spectrum bandwidth consumed by guard bands while maintaining reliable operation.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If TDD synchronization is enforced across all CBSDs, then adjacent channel interference is eliminated, but system flexibility and adaptability are reduced

Engineering Contradiction:

Improveadjacent channel interferenceVSAvoidsystem flexibility

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent segments the CBSD population based on TDD synchronization status. Instead of requiring all CBSDs to be synchronized, the system identifies and separately manages TDD synchronized and TDD unsynchronized CBSDs. Guard bands are inserted specifically for adjacent frequency spectrum pairs involving TDD unsynchronized CBSDs, allowing the system to maintain flexibility and support diverse deployment scenarios while still protecting against interference where it occurs.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12074687B2Systems and methods for diminishing adjacent channel interference between radios using shared frequency spectrum

Publication Date: 2024.08.27 OUTDOOR WIRELESS NETWORKS LLC

AI summary

Techniques are provided for diminishing adjacent channel interference between radios using shared frequency spectrum. A guard band may be inserted between a pair of adjacent frequency spectrums so that they are no longer adjacent.