CQI Headroom Reporting for SINR Saturation in 5G
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Solution Overview
Problem
In Active Antenna Systems (AAS) for 4G LTE and 5G NR, CQI saturation leads to issues like high interference and power waste due to unknown actual SINR at the wireless device, causing inappropriate power control and rank estimation, especially in MU-MIMO scenarios.
Innovation Solution
The system configures wireless devices to provide an extended CQI report with CQI headroom, allowing network nodes to determine actual SINR and adjust power settings, thereby enabling power back-off and split to mitigate interference and optimize energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If maximum CQI value is reported when SINR surpasses threshold, then network node can maintain simple CQI reporting structure, but network node loses ability to determine actual SINR at wireless device
Solution Approach 1:
The CQI report is segmented into two parts: the maximum CQI value (indicating saturation) and an additional indicator providing headroom information. This segmentation allows the network to understand both that saturation occurred and by how much the actual SINR exceeds the threshold, preserving information while maintaining reporting simplicity.
Solution Approach 2:
Instead of reporting actual SINR directly (one-dimensional), the patent adds a second dimension by reporting CQI headroom as a separate indicator. This dimensional approach allows the network to infer actual SINR range based on the headroom value, solving the information loss problem without complicating the base CQI structure.
2Loss of energy
If network node transmits at full power when CQI 15 is received, then power efficiency is improved, but interference to neighboring cells increases due to unknown actual SINR
Solution Approach 1:
The CQI headroom indicator provides feedback to the network about the actual SINR margin. The network uses this feedback to adjust transmit power appropriately - transmitting at full power when headroom indicates sufficient margin, and reducing power when headroom is small, thus balancing power efficiency with interference control.
Solution Approach 2:
The patent changes the parameter being reported from a static maximum CQI value to a dynamic headroom value that reflects actual channel conditions. This parameter change enables the network to adapt power transmission levels based on real-time SINR margins, resolving the contradiction between power efficiency and interference control.
3Loss of time
If CQI saturation is used to simplify reporting, then reporting overhead is reduced, but rank estimation and power control become inaccurate
Solution Approach 1:
The patent performs preliminary action by having the wireless device calculate and report the CQI headroom value in advance. This pre-calculated headroom information enables the network to perform accurate rank estimation and power control without requiring complex real-time measurements, maintaining precision while keeping reporting overhead low.
Data Source
AI summary
According to one or more embodiments, a wireless device configured to report one of a plurality of predefined Channel Quality Indicator (CQI) values is provided. A maximum CQI value of the plurality of predefined CQI values corresponds to any one of a plurality of signal characteristic values greater than or equal to a threshold signal characteristic value. The wireless device includes processing circuitry configured to determine a first signal characteristic value associated with a received signal. The processing circuitry is further configured to if the first signal characteristic value is greater than or equal to the threshold signal characteristic value associated with the maximum CQI value, generate a CQI report indicating: the maximum CQI value, and a power backoff from the first signal characteristic value that results in the threshold signal characteristic value.