RTS Frame Channel Reservation for URLLC in Unlicensed Spectrum
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Solution Overview
Problem
In scenarios where licensed and unlicensed radio technologies coexist in the same frequency band, unlicensed technologies often fail to meet the Quality of Service (QoS) demands for Ultra-Reliable Low Latency Communication (URLLC) applications due to interference and power limitations, particularly in unlicensed frequency bands.
Innovation Solution
The method involves a radio access node transmitting a Request to Send (RTS) frame within a Time Division Duplexing (TDD) radio frame in an unlicensed frequency band, allowing for protected downlink or uplink transmissions by prioritizing data based on the duration indicated in the RTS frame, especially for URLLC services, and utilizing mechanisms like RTS/CTS to manage interference from unlicensed devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If unlicensed radio technology is used in the same frequency band as licensed radio technology, then spectrum utilization is improved, but transmission reliability deteriorates due to interference from unlicensed devices
Solution Approach 1:
The licensed radio access node transmits an RTS frame before the actual data transmission to reserve the channel in advance. This preliminary action prevents unlicensed devices from accessing the channel during the upcoming transmission period, ensuring reliable communication for URLLC services while allowing spectrum sharing with unlicensed technologies.
2Reliability
If higher output power is used for licensed radio technology, then transmission reliability is improved, but interference to unlicensed devices increases
Solution Approach 1:
The patent applies different transmission characteristics to different time periods: during the RTS/CTS protected period, high power transmission is used for reliable URLLC communication; outside this period, normal power levels are maintained to minimize interference to unlicensed devices. This local differentiation in transmission quality resolves the contradiction between reliability and interference.
3Reliability
If RTS/CTS mechanism is implemented for protection, then transmission protection is improved, but device complexity increases
Solution Approach 1:
The RTS/CTS mechanism, originally designed for Wi-Fi channel access, is adapted for dual use: it serves both as a channel reservation protocol for unlicensed spectrum sharing and as a protection mechanism for licensed URLLC transmissions. This multi-functionality provides transmission protection without requiring entirely new protocols, thus limiting the increase in device complexity.
Data Source
AI summary
Systems and methods are disclosed herein that enable protecting a higher priority radio technology (e.g., 3GPP New Radio (NR) or NR in Unlicensed spectrum (NR-U)) when co-existing with an unlicensed radio technology (e.g., the Wi-Fi wireless network technology) operating in the same frequency band. In one embodiment, a method of operation of a radio access node of radio access network of a cellular communications system comprises transmitting a Request to Send (RTS) frame within a Time Division Duplexing (TDD) radio frame on a cell served by the radio access node in an unlicensed frequency band. The method further comprises transmitting a downlink transmission to a wireless communication device or receiving an uplink transmission from the wireless communication device, on the cell served by the radio access node in the unlicensed spectrum during a period of time that corresponds to a duration of time indicated in the RTS frame.