Compact DCI Format for Partial-Adaptive HARQ Retransmissions
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Solution Overview
Problem
Current HARQ systems in LTE Rel-13 MTC require significant control overhead and power consumption for full-adaptive HARQ retransmissions, which is not necessary for coverage enhancement mode, and existing solutions do not efficiently support channel repetition for HARQ retransmissions.
Innovation Solution
A compact DCI format with truncated control information is proposed to support partial-adaptive HARQ retransmissions, using secondary resource grants that carry partial control information for UE in coverage enhancement mode, reducing the number of repetitions and improving spectrum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full-adaptive HARQ retransmission is used, then data transmission reliability is improved, but control overhead and power consumption increase significantly
Solution Approach 1:
The DCI format is segmented into essential fields only, separating critical retransmission parameters (resource allocation, MCS, HARQ process ID) from optional fields. This segmentation allows the system to transmit minimal control information for HARQ retransmissions while maintaining reliability, directly reducing control overhead compared to full-adaptive HARQ
Solution Approach 2:
The patent extracts and removes non-essential control fields from the DCI format for HARQ retransmissions, keeping only the minimum necessary information. This extraction principle eliminates redundant control signaling while preserving the core retransmission function, thereby reducing control overhead and power consumption
2Reliability
If full-adaptive HARQ retransmission is used, then data transmission reliability is improved, but power consumption increases
Solution Approach 1:
By segmenting the DCI format to include only essential fields for HARQ retransmission, the patent reduces the number of bits that need to be transmitted and received. This directly lowers the power consumption of the UE for receiving and processing control channels while maintaining transmission reliability through preserved critical parameters
Solution Approach 2:
The patent applies partial action by transmitting only the necessary subset of control information for HARQ retransmissions rather than complete control information. This partial transmission approach reduces power consumption while still achieving the essential retransmission function
3Productivity
If repetition number is reduced for retransmission, then spectrum efficiency is improved, but coverage enhancement capability decreases
Solution Approach 1:
The patent introduces dynamic adaptation of repetition numbers for HARQ retransmissions based on channel conditions and initial transmission outcomes. This dynamic approach allows the system to reduce repetition numbers (improving spectrum efficiency) when conditions permit, while maintaining coverage enhancement capability by increasing repetitions when needed, resolving the contradiction between the two objectives
Data Source
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AI summary
Methods are provided for HARQ with channel repetitions. In one novel aspect, the user equipment (UE) receives the resource grant and determines the type of the grant as being the initial resource grant or the secondary resource grant. The initial resource grant carries full control information and the secondary resource grant carries partial control information. In some embodiments, the determination of the type of the grant is based on the RNTI or the payload size. In another embodiment, the UE performs data retransmission based on information from the secondary resource grant and the initial resource grant. In another novel aspect, the UE receives higher layer, such the RRC layer. The UE subsequently receives UL or DL secondary resource grant for both initial transmission and the re-transmission. The UE combines the parameters in the UE-specific configuration and the received secondary resource grants for its UL transmission or DL reception.