URLLC HARQ Diversity for Sub-Millisecond Reliability
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving ultra-reliable low-latency communications (URLLC) due to stringent latency and reliability requirements, particularly in 5G New Radio (NR), where single transmissions often fail to meet the required Block Error Ratio (BLER) of 10^-5 or lower within a 0.5ms deadline, necessitating improved hybrid automatic repeat request (HARQ) operations.
Innovation Solution
Implementing enhanced HARQ operations with transmit diversity management and reference signal handling for URLLC services, including channel and interference diversity, through mechanisms such as carrier aggregation, different precoding cycling, and phase shifts across HARQ transmissions, to achieve uncorrelated decoding performance and meet BLER targets efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If single transmission is used to meet latency requirements, then latency is reduced, but reliability deteriorates (cannot achieve BLER of 10^-5 or lower)
Solution Approach 1:
The transmission process is segmented into multiple HARQ transmissions rather than using a single transmission. Each HARQ transmission carries the same transport block with different redundancy versions, allowing the system to divide the reliability requirement across multiple transmission attempts while maintaining low latency through efficient retransmission protocols
Solution Approach 2:
The system changes transmission parameters dynamically across HARQ transmissions, including modulation and coding scheme (MCS), redundancy version (RV), and resource allocation. These parameter variations enable the system to adapt to channel conditions and achieve the required BLER of 10^-5 while maintaining low latency through optimized retransmission strategies
2Reliability
If multiple HARQ transmissions are used to improve reliability, then reliability is improved (achieving BLER of 10^-9), but transmission complexity increases
Solution Approach 1:
The system employs periodic HARQ transmissions with structured timing patterns and predetermined redundancy versions. This periodic structure simplifies the management of multiple transmissions by establishing regular intervals and predictable patterns, reducing the operational complexity while maintaining high reliability through systematic retransmission sequences
Solution Approach 2:
The system uses redundant copies of the transport block across multiple HARQ transmissions with different redundancy versions. Instead of implementing complex error correction algorithms, the system creates multiple copies with varying error protection levels, allowing the receiver to combine these copies and achieve the required BLER of 10^-9 through simpler combining operations
3Reliability
If transmit diversity management is implemented across HARQ transmissions, then reliability is improved through uncorrelated decoding performance, but system complexity increases
Solution Approach 1:
The system dynamically adjusts precoding vectors and phase shifts across different HARQ transmissions to create transmit diversity. By varying these parameters dynamically rather than using fixed configurations, the system achieves uncorrelated decoding performance that improves reliability while managing complexity through adaptive rather than exhaustive approaches
Solution Approach 2:
The system introduces additional dimensions of diversity by varying precoding and phase shift parameters across HARQ transmissions. This creates diversity in the spatial and signal processing domains, allowing the receiver to exploit these additional dimensions for improved decoding performance and reliability without requiring complex multi-antenna configurations
Data Source
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AI summary
Techniques relating to improving ultra-reliable low-latency communications (URLLC) used in wireless communications are described. In an aspect, a method comprises receiving a first downlink transmission of a transport block (TB) from a first transmission point (TP), receiving a first repetition of the transport block (TB) from a second transmission point (TP) and performing quasi-co-location service based on the first transmission point (TP) and the second transmission point (TP). In another aspect, a method comprises mapping a first hybrid automatic repeat request (HARQ) transmission to a first set of sub-bands across a first component carrier (CC) and a second component carrier (CC), and a second HARQ transmission to a second set of sub-bands across the first component carrier (CC) and the second component carrier (CC), and performing the HARQ transmissions.