Phase Reciprocity Calibration for Non-Codebook UL MIMO
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Solution Overview
Problem
Conventional UL MIMO procedures, both codebook-based and non-codebook-based, suffer from sub-optimal performance due to non-reciprocity between the Radio Frequency Front End (RFFE) of User Equipment (UE) in uplink and downlink, leading to inefficient non-codebook-based pre-coding and transmission.
Innovation Solution
Implementing a phase reciprocity calibration procedure using a two-part process involving downlink and uplink Phase Differential Calibration Signals (PDCS) to calibrate the UE's RFFE, utilizing an Analogue Differential Phase Estimation Circuit (A-DPEC) for dynamic calibration, ensuring phase coherence between reception and transmission paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full channel reciprocity is assumed between UL and DL for non-codebook based UL MIMO, then pre-coding can be derived without predetermined codebooks, but the RFFE non-reciprocity causes sub-optimal performance
Solution Approach 1:
The patent changes the phase parameters of the RFFE by introducing calibration signals (DL PDCS and UL PDCS) that allow the system to measure and compensate for phase non-reciprocity. The gNB transmits DL PDCS with specific phase configurations, and the UE responds with UL PDCS, enabling the calculation of phase differences that are used to adjust pre-coding parameters and achieve accurate beamforming despite hardware non-reciprocity
Solution Approach 2:
The patent implements a feedback mechanism where the UE measures the phase of received DL PDCS, calculates phase differences, and reports this information back to the gNB. The gNB uses this feedback to determine accurate pre-coding matrices for UL MIMO transmission, thereby compensating for RFFE non-reciprocity and improving uplink performance
2Ease of operation
If conventional codebook based UL MIMO procedure is used, then predetermined codebooks provide a solution, but the performance is sub-optimal due to reliance on predetermined configurations
Solution Approach 1:
The patent performs preliminary phase calibration actions before the actual UL MIMO data transmission. The gNB first transmits DL PDCS for phase reference, the UE measures and calculates phase differences, and this preliminary calibration information is stored and used to guide the subsequent data transmission pre-coding, ensuring optimal performance from the start
Solution Approach 2:
The patent transitions from static predetermined codebooks to dynamic pre-coding matrices that are adapted based on real-time channel conditions and measured phase reciprocity characteristics. The pre-coding matrices are dynamically calculated using the phase difference information obtained from PDCS measurements, allowing the system to adapt to changing conditions and achieve optimal performance
Data Source
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AI summary
Certain examples provide an apparatus (10, 110) comprising: means (11, 15) for transmitting, to a network node (101), first information (702) indicative of a capability (702) of the apparatus to perform a phase reciprocity calibration procedure (704), wherein the phase reciprocity calibration procedure comprises the apparatus performing: a first part of the phase reciprocity calibration procedure (704_1) using at least one downlink, DL, Phase Differential Calibration Signal, PDCS (707), and a second part of the phase reciprocity calibration procedure (704_2) using at least one uplink, UL, PDCS (708); means (11, 15) for receiving, from the network node, second information (706), wherein the second information is received based at least in part on the transmitted first information, and wherein the second information comprises information for configuring the apparatus to: receive, from the network node, the at least one DL PDCS for enabling the apparatus to perform the first part of the phase reciprocity calibration procedure, and transmit the at least one UL PDCS for enabling the apparatus to perform the second part of the phase reciprocity calibration procedure; means (11, 15) for receiving, from the network node and based at least in part on the received second information, the at least one DL PDCS for enabling the apparatus to perform the first part of the phase reciprocity calibration procedure; and means (11, 15) for transmitting, based at least in part on the received second information, the at least one UL PDCS for enabling the apparatus to perform the second part of the phase reciprocity calibration procedure.