ACK/NACK-Based Relaying for Uplink Coverage
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in improving uplink coverage and reducing latency due to signal quality issues between user equipment (UE) and base stations.
Innovation Solution
The implementation of an ACK/NACK-based relaying scheme, where a relay station receives and forwards uplink data transmissions from UE to the base station, along with feedback information to improve coverage and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct uplink transmission from UE to base station is used, then system complexity is low, but uplink coverage is insufficient and transmission reliability deteriorates
Solution Approach 1:
A relay station is introduced as an intermediary node between the UE and base station to forward uplink data transmissions. The relay station receives data from the UE, processes it, and forwards it to the base station, thereby extending uplink coverage and improving transmission reliability without requiring complex changes to the UE or base station themselves.
Solution Approach 2:
The uplink transmission path is segmented into two independent links: UE-to-relay and relay-to-base station. This segmentation allows each link to be optimized independently and provides diversity gain, as the base station can combine signals from both direct and relayed paths, improving overall reliability while keeping individual node complexity manageable.
2Reliability
If relay station is introduced to improve uplink coverage, then transmission success rate improves, but system latency increases
Solution Approach 1:
The relay station performs preliminary actions by buffering and processing relayed data before forwarding to the base station. HARQ processes are initiated at the relay station level, allowing local retransmissions that can resolve errors before data reaches the base station, thereby reducing the need for additional round-trip delays at the core network level.
Solution Approach 2:
HARQ feedback mechanisms are implemented at multiple levels: the base station provides feedback to both the UE and relay station about transmission success, and the relay station provides feedback to the UE. This multi-level feedback enables early detection and correction of transmission errors, reducing the average latency compared to single-level feedback systems that require longer round trips.
3Area of stationary object
If relay station forwards all uplink data, then coverage is improved, but signal quality and transmission efficiency deteriorate due to unnecessary relaying
Solution Approach 1:
The relay station dynamically adapts its relaying behavior based on real-time channel conditions. When the direct UE-to-base station link is strong, the relay station reduces or stops relaying to avoid unnecessary processing and potential degradation. When the direct link deteriorates, the relay station activates relaying functions, thereby maintaining transmission efficiency while providing coverage extension when needed.
Solution Approach 2:
The system changes operational parameters such as relay gain, forwarding probability, and resource allocation based on channel quality indicators. These parameter adjustments allow the relay station to optimize the balance between coverage extension and transmission efficiency, ensuring that relaying is performed at optimal levels rather than at fixed maximum capacity.
Data Source
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Figure 2A~2D
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AI summary
An acknowledgment (ACK)/negative-ACK (NACK)-based relaying scheme for uplink coverage improvement is provided. A relay station receives, from a destination device, a first feedback transmission associated with the first data transmission. The relay station determines whether the destination device successfully receives the first data transmission based on the first feedback transmission. The relay station communicates, with the destination device, a second feedback transmission associated with the first data transmission when the destination device does not successfully receive the first data transmission. The relay station communicates, with the destination device, a second data transmission associated with the second feedback transmission, in which the second data transmission comprises at least a portion of the first data transmission.