Transparent Relay Downlink Retransmission Coordination
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Solution Overview
Problem
In wireless communication systems employing transparent relays, coordinating concurrent downlink HARQ retransmissions between base stations and relay stations is challenging due to asynchronous nature of HARQ, making it difficult for relay stations to switch between reception and transmission modes within the same subframe, especially when control signaling and data transmission regions are multiplexed without guard time.
Innovation Solution
A method where the base station receives a retransmission request from a mobile station, schedules resources, signals scheduling information to a transparent relay station via a control link, enabling the relay station to send the retransmission in a retransmit subframe on a specific frequency band, allowing concurrent transmission with the base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay stations switch between reception and transmission modes within the same subframe to enable concurrent downlink retransmissions, then system robustness and performance are improved, but coordination complexity increases due to asynchronous HARQ nature
Solution Approach 1:
The base station sends scheduling information to the relay station in advance via a control link before the actual retransmission occurs. This preliminary signaling allows the relay station to prepare for mode switching and coordinate its transmission timing with the base station, resolving the complexity of asynchronous HARQ coordination while enabling concurrent retransmissions that improve system robustness
2Productivity
If control signaling and data transmission regions are multiplexed without guard time to increase spectral efficiency, then spectral efficiency is improved, but difficulty in mode switching between reception and transmission increases
Solution Approach 1:
The patent applies different multiplexing strategies to different parts of the transmission structure. Specifically, control signaling and data transmission regions are multiplexed without guard time in contexts where mode switching is not required, while guard times are introduced specifically at boundaries where relay station mode switching occurs. This localized application of guard times maintains high spectral efficiency while enabling successful mode switching when needed
3Adaptability or versatility
If relay stations participate in concurrent downlink retransmissions to reduce scheduler constraints, then scheduler flexibility is improved, but coordination overhead increases
Solution Approach 1:
The base station acts as an intermediary that sends scheduling information via a control link to coordinate relay station participation in concurrent retransmissions. This intermediary signaling mechanism enables the relay station to align its transmissions with the base station without requiring complex direct coordination between relay stations, thereby increasing scheduler flexibility while minimizing coordination overhead
Data Source
AI summary
In a method of providing downlink retransmissions to a mobile station in a wireless communication network, the wireless communication network comprising a base station communicatively linked to a transparent relay station, the base station receives a request for a retransmission from the mobile station; schedules resources for the retransmission; signals scheduling information for the retransmission to the transparent relay station via a control link; and the transparent relay station receives the scheduling information for the retransmission on the control link; and sends the retransmission to the mobile station in a retransmit subframe on a retransmit frequency band.