UE Localization in C-RAN via Downlink Signal Grouping
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Solution Overview
Problem
In centralized or cloud radio access networks (C-RAN), there is a need to efficiently localize user equipment (UE) among multiple radio units (RUs) for effective wireless communication, as existing methods based on uplink reference signals are not suitable for all deployment scenarios, particularly in C-RAN with downlink only carrier aggregation and non-collocated RUs.
Innovation Solution
The method involves grouping RUs and configuring them to transmit unique downlink signals at specific time instances or in distinct sub-bands, with measurement reports from UE used to select the optimal RUs for serving user equipment based on signal strength measurements, allowing for efficient UE localization across various RAN deployments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If uplink reference signals are used for UE localization, then existing methods can be applied, but they are not suitable for C-RAN with downlink only carrier aggregation and non-collocated RUs
Solution Approach 1:
The patent inverts the traditional uplink-based localization approach by implementing downlink-based localization. Instead of having UE transmit uplink reference signals for measurement, the base station transmits downlink reference signals (CSI-RS) and the UE performs measurements and reports back, making the method suitable for downlink-only carrier aggregation scenarios in C-RAN.
Solution Approach 2:
The patent changes the fundamental parameter of signal direction from uplink to downlink. By transmitting reference signals in the downlink direction and having UE perform measurements, the system achieves compatibility with C-RAN architectures that use non-collocated RUs and downlink-only carrier aggregation, where uplink signals cannot be effectively utilized for localization.
2Measurement precision
If multiple downlink signals are transmitted for UE localization, then accurate RU selection can be achieved, but the number of CSI reports increases system overhead
Solution Approach 1:
The patent segments the large set of RUs into multiple smaller groups, where each group is associated with a specific downlink reference signal. Instead of transmitting separate signals from all RUs individually, RUs within each group transmit the same downlink signal, reducing the total number of distinct signals while maintaining the ability to differentiate between RUs through group-based measurement and reporting.
Solution Approach 2:
The patent makes a single downlink reference signal serve multiple RUs simultaneously by having RUs within a group transmit the same signal. This multi-functional approach allows one reference signal to represent multiple RUs, reducing the number of CSI reports needed while still enabling accurate RU selection through the grouping mechanism.
3Adaptability or versatility
If RUs are non-collocated for flexibility, then network deployment adaptability improves, but signal strength measurements become less reliable for localization
Solution Approach 1:
The patent applies preliminary grouping of RUs into sets that share common downlink reference signals before actual signal transmission and measurement. This pre-organization allows the system to handle non-collocated RUs effectively by ensuring that even geographically dispersed RUs within a group transmit coordinated signals, maintaining measurement reliability despite physical separation.
Solution Approach 2:
The patent changes the localization approach from relying on physical proximity (collocated RUs) to relying on logical grouping and signal association. By using downlink reference signals that can be transmitted by any RU in a group regardless of physical location, the system maintains measurement precision while achieving deployment flexibility with non-collocated RUs.
Data Source
AI summary
The present disclosure describes techniques of user equipment localization in centralized or cloud radio access networks (C-RANs). In the UE localization techniques of the present disclosure, a base station (gNB) configures a plurality of radio units (RUs) serving a cell to transmit one or more downlink signals using various time and/or frequency resources to user equipment (UEs) of the cell. The UEs use the one or more downlink signals to measure quality of downlink channels between the UEs and the plurality of RUs and reports the measured qualities in uplink using one or more CSI reports. The gNB then selects one or more RUs from the plurality of RUs for each UE based on the received CSI reports. Finally, the gNB transmits downlink data towards the UEs and receives uplink data from the UEs using their respective RUs.