Multi-Beam Transmission for URLLC Reliability
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Solution Overview
Problem
The 5G New Radio (NR) standard faces challenges in providing robust beam transmission on millimeter wave frequency bands (FR2) due to beam blocking, which affects reliability and introduces additional latency, making it difficult to meet high data rate and low latency requirements for ultra-reliable low latency communication (URLLC) services.
Innovation Solution
Configuring transmission beam parameters for configured grant (CG) or semi-persistent scheduling (SPS) transmissions, involving the use of transmission configuration indication (TCI) states, sounding resource signal (SRS) resource indicators, quasi-co-location (QCL) assumptions, precoders, and beam indices to enable multiple transmission beams within a transmission period, allowing for robust beam transmission by applying these parameters to transmission opportunities and repeating them as necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beam transmission is used on FR2 bands to achieve high data rate and low latency, then bandwidth and subcarrier spacing can be increased, but beam blocking occurs which reduces reliability and increases latency
Solution Approach 1:
The transmission beam is segmented into multiple candidate beams (first candidate beam, second candidate beam, etc.) that can be independently selected. Instead of relying on a single beam, the system divides the beam selection into multiple options, allowing switching when one beam is blocked, thereby maintaining reliability while using FR2 bands for high data rate transmission
Solution Approach 2:
The beam selection is made dynamic through monitoring mechanisms that continuously assess beam blockage conditions. The system dynamically switches between candidate beams based on real-time channel conditions, allowing the transmission to adapt to changing environments and maintain reliability despite the inherent vulnerability of FR2 beam transmission
2Reliability
If beam blocking recovery mechanisms are implemented to improve reliability, then additional latency is introduced which conflicts with URLLC requirements
Solution Approach 1:
Candidate beams are pre-configured and prepared in advance before transmission is needed. The system performs preliminary beam identification and configuration during setup, so that when transmission occurs, multiple ready-to-use beam options are already available, eliminating the need for time-consuming beam recovery procedures
Solution Approach 2:
The monitoring mechanism is designed to quickly detect beam blockage and rapidly switch to alternative candidate beams. By rushing through the beam selection and switching process using pre-configured options, the system minimizes the time penalty for reliability mechanisms, keeping latency within URLLC requirements
3Reliability
If multiple transmission beams are configured for CG or SPS transmissions, then robustness against beam blocking is improved, but system complexity increases
Solution Approach 1:
Multiple beam parameters (TCI states, SRS resource indicators, QCL assumptions, precoders, beam indices) are configured locally for specific transmission opportunities rather than globally for all transmissions. This allows robustness to be applied where needed (in FR2 URLLC scenarios) while keeping the system simple for other cases, reducing overall complexity while maintaining robustness when required
Data Source
AI summary
Aspects of the present application use diversity of more than one TCI state, QCL assumption, precoder and/or SRI on the network side to enable multiple transmission beams in a transmission period having multiple transmission opportunities to provide robust beam transmission from the network side. An example of transmission opportunities in a transmission period may be OFDM symbols in a slot. Aspects of the present application use diversity of more than one TCI state, QCL assumption, precoder and/or SRI at the UE to enable the UE to transmit multiple transmission beams in a configured transmission period having multiple transmission opportunities to provide robust transmission from the UEs. When using multiple transmission beams, in the event that data transmitted on one beam cannot be decoded (e.g. due to beam blockage, poor radio conditions, etc.), data transmitted on other beams can still be decoded successfully.