Power Control Offset Scaling for Coherent Joint Transmission
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Solution Overview
Problem
In wireless networks, particularly in 3GPP New Radio (NR) Release 18, the current agreement for Type-II-CJT CSI reporting assumes a commonly configured powerControlOffset for all CSI-RS resources, which may lead to overestimation of CQI when a UE selects fewer TRPs for transmission, resulting in biased TRP selection.
Innovation Solution
The proposed solution involves modifying the UE assumption to scale the powerControlOffset by N/N TRP for each CSI-RS resource, ensuring that the PDSCH signals' EPRE to CSI-RS EPRE ratio is adjusted based on the number of active TRPs, thereby correcting the CQI calculation and preventing overestimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a commonly configured powerControlOffset is assumed for all CSI-RS resources, then the CQI calculation is simplified, but the CQI is overestimated when fewer TRPs are selected, leading to biased TRP selection
Solution Approach 1:
The patent changes the parameter used for CQI calculation from a fixed common powerControlOffset to a scaled powerControlOffset that varies based on the number of selected TRPs. Specifically, the UE scales the powerControlOffset by the ratio N/N_TRP where N is the number of selected TRPs and N_TRP is the maximum configurable TRPs. This parameter change ensures that the PDSCH EPRE assumption accurately reflects the actual transmission power when fewer TRPs are active, thereby improving CQI accuracy without significantly complicating the calculation process.
2Device complexity
If the UE assumes a common powerControlOffset for all TRPs, then the configuration is simpler, but the TRP selection becomes biased due to CQI overestimation
Solution Approach 1:
The patent modifies the powerControlOffset parameter from a static common value to a dynamic scaled value that depends on the number of selected TRPs. The scaling factor N/N_TRP is calculated based on the ratio of selected TRPs to maximum configurable TRPs. This change introduces minimal additional complexity in the form of a simple scaling calculation while significantly improving TRP selection reliability by preventing CQI overestimation that would otherwise bias the selection process.
3Ease of operation
If the PDSCH EPRE ratio is not scaled with the number of active TRPs, then the calculation is more straightforward, but the CQI reporting becomes inaccurate
Solution Approach 1:
The patent introduces a scaling parameter to the PDSCH EPRE ratio calculation. Instead of using a fixed powerControlOffset, the UE now scales this parameter by the ratio of the number of selected TRPs (N) to the maximum number of configurable TRPs (N_TRP). This scaling adjustment ensures that the assumed PDSCH EPRE accurately represents the actual transmission power when fewer than the maximum number of TRPs are active, thereby improving CQI reporting accuracy while maintaining calculation straightforwardness through a simple multiplicative scaling operation.
Data Source
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AI summary
In accordance with an example embodiment of the present invention, provided are methods, apparatuses and computer program products configured at least to: select an integer number N0 of channel state information reference signal (CSI-RS) resources out of an integer number of NTRP network configured CSI-RS resources to a resource set associated with a CSI report configuration, wherein N < NTRP; determine a scaling factor for the resource set; determine at least one CSI component, based at least in part on an assumption that a ratio of a transmitted energy per resource element (EPRE) of a PDSCH signal and a transmitted EPRE of the nth CSI-RS resource is equal to the scaling factor times a power control offset configured for the nth CSI-RS resource of the resource set, wherein n ∈ [1, N]; and transmit a CSI report to a network comprising the determined at least one CSI component.