Beamformed Reference Signal Reporting for Wireless Channel Estimation
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Solution Overview
Problem
Current channel estimation procedures in wireless communications, particularly in high-frequency bands, face challenges with high overhead due to the large number of antennas used in network nodes, leading to inefficient channel state information acquisition and increased signaling overhead.
Innovation Solution
A method where a network node transmits a first set of beam-formed reference signals reflecting channel coefficients, with the number of beams reduced compared to the number of receive antennas, allowing for efficient channel estimation and reduced overhead, and enabling the wireless device to estimate its uplink channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network node uses a large number of antennas for beamforming to counteract poor radio channel propagation properties at high frequencies, then the network coverage and link budget are improved, but the signaling overhead and system complexity increase significantly
Solution Approach 1:
The patent segments the channel estimation process into two parts: the network node performs downlink channel estimation using DL-RS, and the wireless device performs uplink channel estimation using the estimated downlink channel and uplink reference signals. This segmentation allows the network node to use fewer antennas while still achieving reliable channel state information acquisition, thereby reducing the device complexity and signaling overhead associated with having a large number of antennas at the network node.
2Loss of information
If the network node forwards all received sounding reference signals from each antenna to the wireless device, then complete channel state information is obtained, but the overhead increases to M times N where M is the number of SRS and N is the number of receive antennas
Solution Approach 1:
The patent extracts only the essential channel state information from the downlink channel estimation and uses it to guide the uplink channel estimation process at the wireless device. Instead of forwarding all M×N reference signals, the network node provides compressed channel state information that captures the essential channel characteristics. This extraction approach maintains the necessary information for accurate channel estimation while dramatically reducing the overhead from M×N to a much smaller quantity.
Solution Approach 2:
The network node performs preliminary downlink channel estimation using downlink reference signals before the wireless device needs to perform uplink channel estimation. This preliminary action provides the wireless device with advance channel state information that it can use to efficiently estimate the uplink channel, reducing the need for extensive reference signal forwarding and thereby reducing overhead.
3Measurement precision
If additional downlink reference signals are transmitted to support full loop precoding, then accurate uplink channel estimation is enabled, but extra signaling overhead is introduced
Solution Approach 1:
The patent implements a feedback mechanism where the wireless device estimates the downlink channel using DL-RS, then uses this estimated channel information along with uplink reference signals to determine uplink channel state information. The wireless device feeds back this channel state information to the network node, which uses it for precoding. This feedback approach achieves accurate channel estimation without requiring the network node to transmit additional downlink reference signals, thereby maintaining measurement precision while reducing signaling overhead.
Data Source
AI summary
There are provided mechanisms for reporting channel coefficients to a wireless device. A method is performed by a network node. The method includes receiving reference signals from the wireless device. The method includes transmitting a first set of beam-formed reference signals. The first set of beam-formed reference signals reflects channel coefficients and is based on the received reference signals and the number of beams in the first set of beam-formed reference signals is less than the number of receive antennas in which the reference signals are received, thereby reporting the channel coefficients to the wireless device.