SCell Precoder Prediction Using PCell CSI Spatial Information
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Solution Overview
Problem
Existing 5G/NR communication systems face inefficiencies in obtaining channel state information (CSI) for secondary cells (SCells) due to the high cost of obtaining CSI at the base station using uplink sounding reference signals (SRS) on SCells, which is not very efficient, and the precoders obtained from user equipment (UE) feedback are also not optimal.
Innovation Solution
Utilize the channel state information from the primary cell (PCell) to predict wideband precoders for secondary cells (SCells) by deriving spatial information from the uplink sounding reference signal (SRS) on the PCell, which remains invariant across frequency translations, and apply these precoders for data transmission in SCells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSI is obtained using uplink sounding reference signals on SCells, then channel state information for SCell is obtained, but computational expense and complexity increase significantly
Solution Approach 1:
The patent performs preliminary spatial information extraction from PCell SRS before SCell data transmission. The base station identifies spatial information from uplink SRS on PCell in advance, then uses this pre-extracted information to predict SCell precoders, avoiding the need for real-time CSI acquisition on SCell.
Solution Approach 2:
The patent creates a copy of spatial information from PCell to predict SCell precoders. Instead of directly measuring SCell channel, the system copies spatial characteristics from PCell SRS and applies them to SCell precoder prediction, significantly reducing measurement and computation overhead.
2Loss of information
If precoders are obtained from UE feedback, then precoder information is available, but transmission efficiency decreases due to feedback overhead
Solution Approach 1:
The patent introduces spatial information extracted from uplink SRS as an intermediary to obtain precoder information. Instead of direct UE feedback, the base station uses the SRS signal as a mediator to infer spatial characteristics and predict precoders, eliminating the need for explicit UE feedback while maintaining information availability.
Solution Approach 2:
The system uses the uplink SRS signal that UE transmits for other purposes (channel estimation) to also provide spatial information for precoder prediction. The SRS signal serves multiple functions simultaneously, allowing the system to extract needed information without additional overhead or dedicated feedback mechanisms.
3Ease of operation
If frequency gap exists between UL and DL centers, then spatial information can be derived from PCell, but frequency mismatch may affect accuracy
Solution Approach 1:
The patent changes the approach from frequency-specific channel measurement to spatial parameter extraction. By focusing on angular/spatial parameters that are relatively frequency-invariant rather than frequency-specific channel coefficients, the system can derive spatial information from PCell and apply it to SCell despite frequency gaps between uplink and downlink centers.
Data Source
AI summary
Apparatuses and methods for a precoder prediction for SCell using a PCell CSI in a wireless communication system. A method of a BS in a wireless communication system includes: receiving an uplink (UL) sounding reference signal (SRS) on a primary cell (PCell); identifying, based on the UL SRS, spatial information associated with a frequency within a center frequency gap between a UL and a downlink (DL); identifying, based on the spatial information, one or more wideband (WB) precoders for at least one user equipment (UE) camping in a secondary cell (SCell); and transmitting, to the UE, a signal based on the one or more WB precoders.