HARQ Early Termination for Wireless Retransmission Efficiency
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Solution Overview
Problem
In wireless communication systems, the conventional HARQ process is inefficient due to the need for multiple stop-and-wait processes, which can lead to increased transmit power requirements and interference, especially when retransmitting failed data blocks with the same transport block size, causing errors and system capacity issues.
Innovation Solution
Implementing early HARQ termination conditions, such as exceeding maximum transmit power or differing transport format combinations, to discard packets at the HARQ level and recover them via higher-layer processing, allowing for dynamic reconfiguration of retransmissions to avoid resource waste and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple stop-and-wait HARQ processes are used in parallel to improve system efficiency, then throughput is improved, but transmit power requirements increase and interference increases
Solution Approach 1:
The patent implements dynamic HARQ process selection where the system transitions from static multiple parallel stop-and-wait processes to a dynamic approach where a single HARQ process adapts its behavior based on channel conditions, power availability, and buffer status, thereby maintaining throughput while reducing power consumption
Solution Approach 2:
The system dynamically changes transmission parameters including transport block size, modulation scheme, and coding rate based on channel quality indicators and power headroom reports, allowing the HARQ process to optimize performance without requiring multiple parallel processes operating at high power levels
2Device complexity
If the same transport block size is used for retransmission to simplify the HARQ process, then device complexity is reduced, but puncturing increases and error probability increases
Solution Approach 1:
The patent enables dynamic adaptation of transport block size for retransmissions based on channel conditions. When channel quality deteriorates or puncturing is detected, the system reduces the transport block size for retransmission, thereby maintaining reliability without requiring complex multi-process HARQ mechanisms
Solution Approach 2:
The system uses feedback from channel quality indicators, hybrid automatic repeat request acknowledgments, and power headroom reports to dynamically adjust retransmission parameters. This feedback mechanism allows the system to optimize transport block size based on actual channel conditions rather than using fixed sizes
3Reliability
If transmit power is increased for retransmission to overcome poor channel conditions, then reliability is improved, but maximum power is exceeded and system capacity is reduced
Solution Approach 1:
Instead of increasing power, the system changes other transmission parameters including reducing transport block size, adjusting modulation and coding schemes, and modifying resource allocation. This allows the system to maintain reliability while staying within power constraints and preserving system capacity
Solution Approach 2:
The system dynamically adjusts transmission parameters based on real-time channel conditions and power availability. When power headroom is limited, the system adapts by selecting appropriate transport block sizes and modulation schemes that achieve reliable transmission without exceeding maximum power limits
4Reliability
If E-DCH serving grant is increased to support higher retransmission power, then reliability is improved, but interference increases and overall system capacity is affected
Solution Approach 1:
The system optimizes the E-DCH serving grant by dynamically adjusting transport block size and transmission parameters based on channel conditions and interference levels. This allows the system to achieve reliable retransmissions with moderate grant sizes, avoiding the need to increase grants to levels that would cause excessive interference
Solution Approach 2:
The system implements dynamic serving grant allocation where the granted resources are adjusted based on real-time channel quality, buffer status, and interference conditions. This dynamic approach ensures that sufficient resources are allocated for reliable retransmissions while minimizing interference to other users in the system
Data Source
AI summary
A method and apparatus for hybrid automatic repeat request (HARQ) transmission are disclosed. If a packet has not been successfully transmitted, it is determined whether an HARQ early termination condition is met. If the HARQ early termination condition is met, the HARQ process is terminated and the packet is discarded at the HARQ level. The HARQ early termination condition is met if a positive acknowledgement (ACK) has not been received until the number of retransmissions reaches a predetermined limit that is dynamically configured based on channel condition, measurement, etc. Alternatively, the HARQ early termination condition is met if a transmit power required for successful transmission of the packet is much higher than an actual transmit power. Alternatively, the HARQ early termination condition is met if a transport format combination (TFC) selected for retransmission is different from an optimal TFC. A higher layer may be notified of the early HARQ termination.