Relay Link HARQ Timing for MBSFN Subframes
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Solution Overview
Problem
Relay nodes in wireless communication systems often miss acknowledgments (ACK/NACK) from access nodes due to simultaneous transmission and reception constraints, leading to interference and retransmission issues, particularly with different MBSFN subframe periodicities.
Innovation Solution
Implementing a multi-mode HARQ transmission scheme with synchronous retransmission for 10 ms periodicity and asynchronous retransmission for 40 ms periodicity, adjusting timing and granting mechanisms to ensure relay nodes receive ACK/NACKs without interference, and using smart NACKs and aggregation techniques to manage collisions and retransmissions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If relay nodes transmit and receive simultaneously on the same frequency, then communication efficiency is improved, but self-interference occurs causing ACK/NACK messages to be missed
Solution Approach 1:
The patent segments the transmission and reception operations into separate time slots. Specifically, it divides the communication process into forward transmission slots (relay receiving from UE) and backward transmission slots (relay transmitting to eNB), preventing simultaneous transmission and reception on the same frequency and eliminating self-interference.
Solution Approach 2:
The patent implements periodic transmission and reception slots with fixed timing relationships. The eNB transmits downlink data in specific subframes, the relay node receives and processes them, then transmits acknowledgments in predetermined subsequent subframes, creating a periodic pattern that avoids self-interference while maintaining efficient communication.
2Device complexity
If ACK/NACK timing is fixed for all MBSFN periodicities, then system complexity is reduced, but reliability decreases when relay nodes miss acknowledgments
Solution Approach 1:
The patent dynamically adjusts the ACK/NACK timing based on the MBSFN subframe periodicity. For 10ms periodicity, ACK/NACK is transmitted in the 4th subframe after the uplink transmission, while for 40ms periodicity, it is transmitted in the 8th subframe. This dynamic timing adjustment ensures reliable ACK/NACK reception for different periodicities without significantly increasing system complexity.
Solution Approach 2:
The patent changes the timing parameter (k value) based on the MBSFN periodicity configuration. When periodicity is 10ms, k=4; when periodicity is 40ms, k=8. This parameter adaptation allows the system to maintain high reliability for ACK/NACK reception across different operational modes while keeping the underlying mechanism simple.
3Stability of the object's composition
If relay nodes use synchronous HARQ retransmission, then timing alignment is improved, but adaptability to different MBSFN periodicities deteriorates
Solution Approach 1:
The patent makes the HARQ retransmission timing dynamic based on the MBSFN periodicity configuration. For 10ms periodicity, retransmission occurs after a fixed 4-subframe delay (synchronous behavior), while for 40ms periodicity, the timing is adjusted to 8 subframes (asynchronous behavior). This dynamic adjustment provides adaptability to different periodicities while maintaining timing alignment within each mode.
Solution Approach 2:
The patent creates a universal HARQ mechanism that can function in both synchronous and asynchronous modes depending on the MBSFN periodicity configuration. The same relay node and eNB infrastructure support both 10ms and 40ms periodicities with appropriate timing adjustments, making the system versatile without requiring separate dedicated systems for each periodicity type.
Data Source
AI summary
A method for preventing a first network node from missing a transmission from a second network node. The method includes, when a ten millisecond periodicity is used for Multicast/Broadcast Single Frequency Network (MBSFN) subframes, setting a time between an uplink grant from the second network node to the first network node and an acknowledgement/negative-acknowledgement message (ACK/NACK) from the second network node to the first network node equal to ten milliseconds. The method further includes, when a forty millisecond periodicity is used for MBSFN subframes, the second network node sending the first network node an asynchronous grant for an uplink retransmission when a data packet is missed, and when the first network node receives the grant for the uplink retransmission, the first network node retransmitting the missed data packet.