Circular Buffer HARQ for Polar Code Rate Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless communication technologies, such as those used in 5G networks, face challenges in achieving optimal throughput and error rate management for ultra-reliable low-latency communications, particularly in meeting stringent block error rate requirements and latency constraints.
Innovation Solution
A circular buffer-based hybrid automatic retransmission request (HARQ) scheme is employed using polar codes, where a target coding rate and buffer size are determined to generate redundancy versions, with increased transmission resources and lower code rates allocated for the last transmission to minimize error rates and meet latency requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional HARQ schemes are used for polar codes, then implementation simplicity is maintained, but throughput efficiency and error rate performance are insufficient to meet 5G URLLC requirements
Solution Approach 1:
The patent implements dynamic code rate adaptation where the code rate is adjusted based on channel conditions and transmission history. The system dynamically selects redundancy versions and adjusts coding rates to optimize both reliability and throughput performance for polar codes in 5G URLLC scenarios
Solution Approach 2:
The patent changes key parameters including code rate, redundancy version, and circular buffer size based on channel quality indicators and transmission requirements. These parameter adjustments enable the system to achieve optimal error rate performance while maintaining high throughput efficiency
2Reliability
If more redundancy versions are transmitted to reduce error rate, then block error rate improves, but transmission time and latency increase
Solution Approach 1:
The patent prepares multiple redundancy versions in advance using a circular buffer, allowing the system to quickly select and transmit the most appropriate version without delay. This preliminary preparation enables rapid response to channel conditions while maintaining low latency
Solution Approach 2:
The system uses channel quality feedback and transmission history to intelligently select which redundancy versions to transmit. This feedback mechanism ensures that only necessary retransmissions are performed, optimizing the balance between error rate reduction and latency maintenance
3Reliability
If fixed code rate is used for all transmissions, then system complexity is reduced, but adaptive error rate optimization is lost
Solution Approach 1:
The system automatically adjusts code rates and selects redundancy versions based on channel conditions without requiring complex external control. The circular buffer mechanism enables self-managed adaptation where the system serves itself by intelligently selecting transmission parameters based on real-time conditions
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to methods and apparatus for rate-matching a stream of bits encoded using polar codes. An exemplary method generally includes determining a target coding rate, R T, for transmitting a group of K information bits, based on a first coding rate, R 1, corresponding to a first target block error rate (BLER) for a first transmission of a first redundancy version (RV) of the packet and a second coding rate, R 2, corresponding to a second target BLER for a last transmission of a last RV of the packet; determining a circular buffer size, N, of a circular buffer for use in transmitting the first RV and the last RV of the packet; generating encoded information bits from the K information bits using a polar code having a mother code size of N; writing the encoded information bits to the circular buffer; determining a maximum number of retransmissions, based on a latency requirement for the packet; generating different RVs from the encoded information bits in the circular buffer, each RV based on a corresponding target BLER; and transmitting the first RV via a wireless medium.