Link Adaptation in Type-II Relay Networks
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Solution Overview
Problem
Type-II relay networks in LTE-Advanced systems face challenges in link adaptation due to the lack of CRS and PDCCH, leading to conservative MCS selection and inefficient use of relaying gain, as well as difficulties in differentiating between macro-UE and relay-UE connections and dynamically adjusting CQI.
Innovation Solution
The eNodeB classifies UEs into macro-UEs and relay-UEs, applying conventional link adaptation for macro-UEs and a modified method for relay-UEs, including maintaining a UE list for relay-UE association, using CQI compensation and dynamic CQI adjustment to select aggressive MCS based on combined channel quality, and employing channel probing for optimal MCS selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If type-II relay uses transparent relaying without PDCCH and separate cell ID, then transmission rate is improved and relay is transparent to UEs, but link adaptation becomes difficult and CQI reporting is unreliable
Solution Approach 1:
The patent introduces a relay node as an intermediary that performs CQI measurement and reporting on behalf of the UE. The relay measures the downlink channel quality and reports it to the eNodeB, enabling link adaptation without requiring direct UE measurement capability in the transparent relay mode.
Solution Approach 2:
The patent replaces the traditional UE-based CQI measurement mechanism with a relay-based measurement mechanism. Instead of UEs measuring and reporting CQI directly, the relay nodes perform the measurement and reporting functions, substituting the mechanical measurement process with a different approach suitable for transparent relaying.
2Reliability
If conservative MCS is selected to ensure reliable transmission, then transmission reliability is improved, but spectrum utilization deteriorates
Solution Approach 1:
The patent implements dynamic MCS selection based on real-time CQI feedback from relay nodes. The MCS is adjusted dynamically according to channel conditions rather than being fixed or overly conservative, allowing the system to optimize between reliability and spectrum utilization based on actual transmission conditions.
Solution Approach 2:
The patent establishes a feedback mechanism where relay nodes report CQI information to the eNodeB, which then uses this feedback to select appropriate MCS values. This closed-loop feedback system enables adaptive MCS selection that balances reliability and spectrum efficiency.
3Speed
If CQI reporting delay is reduced for faster link adaptation, then adaptation speed is improved, but measurement accuracy deteriorates due to time-varying channel conditions
Solution Approach 1:
The patent performs CQI measurement in advance at the relay node before the actual data transmission begins. By pre-measuring the channel quality and reporting it to the eNodeB, the system prepares the necessary information ahead of time, enabling fast adaptation without sacrificing measurement accuracy since the measurement is performed under stable conditions.
Data Source
AI summary
This invention is related to the link adaptation for the downlink transmission in type-II relay network. An method in an eNodeB for adapting link for downlink transmission in type-II relay network, said type-II relay network comprises the eNodeB, one or more relay nodes and a plurality of User Equipments (UE), the method comprises the steps of: classifying the plurality of UEs into two groups: macro-UEs which are served directly by the eNodeB without the help of the one or more relay nodes, and relay-UEs which are served by the eNodeB and the one or more relay nodes; and adapting link for the macro-UEs and the relay-UEs separately.