Network-Centric Link Adaptation for CoMP Downlink
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Solution Overview
Problem
Conventional UE-centric link adaptation in wireless communication networks is inefficient due to rapid changes in own-cell and other-cell interference, leading to underutilization of radio resources and reduced spectral efficiency, as UE-reported SINR measurements are poor predictors of future channel conditions.
Innovation Solution
A network-centric link adaptation process where CoMP cell controllers estimate downlink channel quality, intra-CoMP cell interference, and thermal noise, allowing for accurate selection of modulation and coding schemes without relying on frequent UE reports, by coordinating scheduling and signal processing across CoMP cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If UE-centric link adaptation is used with periodic SINR reporting, then the system can operate with simple UE measurements, but the spectral efficiency is reduced due to poor prediction of future channel conditions
Solution Approach 1:
The patent inverts the conventional UE-centric link adaptation approach by implementing a network-centric approach. Instead of having UEs measure and report SINR periodically, the network transceiver performs channel quality estimation using downlink reference signals and combines this with scheduling information to predict future SINR values. This inversion allows the network to proactively determine optimal modulation and coding schemes without relying on delayed UE reports, thereby improving spectral efficiency while maintaining operational simplicity.
2Measurement precision
If CQI reporting frequency is increased to improve SINR prediction accuracy, then the predictive value of SINR improves, but uplink congestion and interference increase
Solution Approach 1:
The patent extracts the channel quality estimation function from the UE and relocates it to the network transceiver. By having the network perform channel quality estimation using downlink reference signals and combine it with scheduling information, the system eliminates the need for frequent uplink CQI reports. This extraction of the estimation function resolves the contradiction by achieving accurate SINR prediction without increasing uplink traffic, thereby avoiding additional interference.
3Power
If frequent UE SINR reports are used for link adaptation, then the data rate can be optimized, but radio resources are underutilized due to delays in reporting
Solution Approach 1:
The patent implements preliminary action by having the network transceiver perform channel quality estimation in advance using downlink reference signals before actual data transmission occurs. The network combines this pre-estimated channel quality with scheduling information to predict future SINR values and determine optimal modulation and coding schemes proactively. This preliminary estimation eliminates the need for waiting for UE reports, thereby optimizing data rate while eliminating reporting delays.
Data Source
AI summary
A Coordinated MultiPoint (CoMP) cell controller performs network-centric link adaptation for User Equipment (UE) in the CoMP cell. The CoMP cell controller receives at least infrequent channel estimates from a UE in the CoMP cell, from which it estimates downlink channel and thermal noise at the UE. The CoMP cell controller is aware of the desired signal to be received at the UE, and the intra-CoMP cell interference to the UE caused by transmissions to other UEs in the CoMP cell. The CoMP cell receives from the UE reports of inter-CoMP cell interference caused by transmissions by other CoMP cells. Based on the downlink channel quality, the desired signal, the intra-CoMP cell interference, the inter-CoMP cell interference, and the thermal noise, the CoMP cell controller performs link adaptation by selecting modulation and coding schemes, and other transmission parameters, for an upcoming transmission duration (such as a TTI).