HARQ-ACK Transmission Scheduling in LTE D2D Coexistence
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Solution Overview
Problem
In LTE systems, User Equipment (UE) faces challenges in transmitting Hybrid Automatic Repeat reQuest-Acknowledge (HARQ-ACK) signals when uplink subframes are occupied by Device-to-Device (D2D) channels or signals, as it cannot simultaneously transmit both D2D and cellular channels on the same subframe, affecting HARQ-ACK transmission efficiency.
Innovation Solution
A method and UE for transmitting HARQ-ACK in LTE systems, where the UE receives information from an evolved Node B (eNB) to determine uplink subframe assignments, allowing for the prioritization and scheduling of HARQ-ACK transmissions based on D2D and cellular channel priorities, and adjusting timing to avoid conflicts with D2D subframes, ensuring uninterrupted HARQ-ACK transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If uplink subframes are allocated for D2D channel transmission, then D2D communication capability is improved, but HARQ-ACK transmission reliability deteriorates
Solution Approach 1:
The patent implements dynamic subframe configuration where the eNB can flexibly assign uplink subframes for either D2D communication or cellular uplink transmission based on traffic conditions. The UE receives dynamic indications via PDCCH/ePDCCH to determine whether to transmit D2D signals or HARQ-ACK in configured subframes, allowing the system to adaptively switch between D2D and cellular functions to maintain both capabilities without permanent resource allocation conflicts
Solution Approach 2:
The patent introduces priority-based arbitration mechanisms as intermediaries to resolve conflicts between D2D and cellular transmissions. When both D2D and HARQ-ACK transmissions are scheduled in the same subframe, priority rules determine which transmission takes precedence, with the ability to drop lower-priority transmissions to ensure high-priority transmissions succeed, thus maintaining overall system reliability
2Adaptability or versatility
If uplink subframes are occupied by D2D channels, then device-to-device communication is enabled, but HARQ-ACK transmission efficiency deteriorates
Solution Approach 1:
The patent employs preliminary configuration of D2D subframes through higher-layer signaling (RRC configuration) where the eNB pre-assigns specific uplink subframes for potential D2D use. This allows the system to prepare D2D resources in advance without permanently blocking cellular uplink transmissions, as the actual D2D transmission only occurs in these pre-configured subframes when needed, while HARQ-ACK can use other subframes or fallback mechanisms
Solution Approach 2:
The patent changes the timing parameters of HARQ-ACK transmission dynamically based on D2D subframe configurations. When D2D subframes are detected, the system adjusts HARQ-ACK timing offsets (k values) to transmit acknowledgments in alternative uplink subframes, modifying transmission timing parameters to avoid conflicts and maintain transmission efficiency
3Productivity
If the UE transmits both D2D and cellular channels on the same subframe, then resource utilization is maximized, but transmission conflict occurs
Solution Approach 1:
The patent segments uplink subframes into different functional categories: cellular uplink subframes for traditional eNB-UE communication, D2D subframes for device-to-device communication, and flexible subframes that can be dynamically assigned. This segmentation is achieved through separate configuration mechanisms (SIB19 for D2D subframes, RRC for cellular uplink) and dynamic indication via PDCCH, allowing the system to divide time resources into distinct transmission domains to avoid simultaneous conflicting transmissions
Data Source
AI summary
The provided is a method for transmitting HARQ-ACK in a LTE system, which is applicable to a situation that an uplink subframe is occupied in an FDD or TDD system. The method is implemented as follows. A UE receives information from an eNB, and determines the assignment of uplink subframes in a cell. The UE determines the transmission of HARQ-ACK according to the assignment of uplink subframes in the cell. By the provided method, the transmission of HARQ-ACK of PDSCH is less influenced when an uplink subframe in the FDD or TDD system is occupied.