Frequency Hopping Synchronization Signals in Unlicensed Spectrum
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Solution Overview
Problem
Wireless communication systems face inefficiencies in identifying synchronization signals in unlicensed radio frequency spectrum due to limitations on transmitter usage, particularly when performing listen-before-talk (LBT) routines, which can hinder efficient network operation and UE acquisition.
Innovation Solution
The implementation of frequency hopping techniques for transmitting synchronization signals across multiple hopping frequencies in unlicensed radio frequency spectrum, allowing base stations to identify and transmit synchronization signals without performing a listen-before-talk routine, enabling more reliable identification by user equipment (UE).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen-before-talk (LBT) routines are performed before transmitting synchronization signals in unlicensed spectrum, then channel access compliance is improved, but transmission efficiency and UE acquisition speed deteriorate due to additional time and complexity
Solution Approach 1:
The patent extracts the LBT procedure from the synchronization signal transmission path, allowing synchronization signals to be transmitted without performing LBT. This separation enables compliance with LBT requirements for data transmissions while eliminating LBT delays for critical synchronization and broadcasting signals, thereby improving transmission efficiency without compromising channel access compliance for regular data traffic.
Solution Approach 2:
The patent establishes predetermined rules and configurations for synchronization signal transmission in unlicensed spectrum, including predefined time windows, frequency selections, and hopping patterns. These preliminary actions allow base stations to transmit synchronization signals immediately without performing LBT, as the transmission parameters are pre-approved by regulatory frameworks and standard specifications.
2Reliability
If synchronization signals are transmitted using frequency hopping across multiple hopping frequencies, then reliability of UE identification is improved through diversity, but device complexity increases due to hopping pattern management
Solution Approach 1:
The patent segments the synchronization signal transmission across multiple frequency hops, dividing the transmission into discrete frequency segments. Each hop transmits a portion of the synchronization signal or reference signals, and the UE combines information from multiple hops to achieve reliable identification. This segmentation provides frequency diversity, improving reliability while the segmented structure simplifies the hopping pattern management compared to continuous frequency switching.
Solution Approach 2:
The patent implements periodic frequency hopping patterns where synchronization signals are transmitted at regular intervals across predetermined frequency sequences. The periodic nature of the hopping pattern allows UEs to predict and efficiently monitor the hopping sequence, reducing the complexity of tracking and managing frequency changes while maintaining reliable signal acquisition through repeated periodic transmissions.
3Speed
If synchronization signals are transmitted without LBT in unlicensed spectrum, then transmission speed is improved, but interference with other users of the spectrum increases
Solution Approach 1:
The patent implements dynamic frequency hopping for synchronization signal transmission, where the base station switches between multiple frequency channels according to a predetermined hopping pattern. This dynamic approach allows the system to quickly access the spectrum for synchronization transmissions without LBT while mitigating interference by distributing transmissions across multiple frequencies. If interference is detected on one frequency, the hopping pattern naturally transitions to other frequencies, reducing harmful effects on other spectrum users.
Data Source
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AI summary
Described techniques provide for transmission of synchronization signals using frequency hopping across a number of hopping frequencies in unlicensed or shared radio frequency spectrum. A base station may identify a set of hop frequencies for transmitting synchronization signals, and transmit synchronization signals using a hopping pattern over the hop frequencies. A user equipment (UE) seeking to identify the base station may monitor one or more of the hop frequencies to identify one or more synchronization signals on the hop frequency. A system timing may be identified in some cases, and one or more base station IDs may be identified. In some cases, a hop frequency may be monitored for a duration that may span the transmission of two or more synchronization signals of a particular base station, based on a periodicity of synchronization signal transmissions on each hop frequency.