UL-Assisted Mobility Using Candidate-Cell Uplink Signals
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Solution Overview
Problem
Existing 5G/NR communication systems do not adequately consider uplink (UL) channel conditions for mobility decisions, such as handovers, which can lead to suboptimal performance in scenarios with dominant UL traffic or when UL-only TRPs are involved.
Innovation Solution
The system enables UL assisted mobility by allowing UEs to transmit UL signals like SRS or PRACH to candidate cells based on configured conditions, enabling the network to evaluate UL channel conditions for more informed handover decisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mobility decisions are made based only on downlink channel conditions, then the decision process is simple, but the accuracy of mobility decisions deteriorates in scenarios with dominant UL traffic or UL-only TRPs
Solution Approach 1:
The system performs preliminary uplink signal transmissions (SRS or PRACH) from the UE to candidate cells before handover decisions are made. These preliminary actions provide the network with advance information about uplink channel conditions, enabling more accurate mobility decisions without increasing the complexity of the decision-making process itself.
Solution Approach 2:
The patent introduces uplink reference signals (SRS) or random access signals (PRACH) as intermediary elements that mediate between the UE and candidate cells. These signals serve as intermediaries to convey uplink channel quality information to the network, allowing the system to evaluate uplink conditions without requiring direct feedback mechanisms that would increase complexity.
2Productivity
If the network evaluates only downlink channel conditions, then the evaluation process is simple, but network performance deteriorates in scenarios with dominant UL traffic
Solution Approach 1:
The system extracts uplink channel condition information by having the UE transmit specific uplink reference signals (SRS) or random access signals (PRACH) to candidate cells. This extraction process isolates the uplink quality metric from the overall handover decision process, allowing the network to obtain necessary uplink information without being overwhelmed by excessive data collection requirements.
Solution Approach 2:
The network uses the uplink signals transmitted by the UE as feedback about uplink channel conditions. By analyzing the quality of these transmitted signals at the candidate cells, the network receives implicit feedback about uplink accessibility and channel quality, which complements downlink measurements and improves overall network performance in UL-dominated scenarios.
3Adaptability or versatility
If the system supports UL-only TRPs, then coverage is improved, but mobility decision accuracy deteriorates without UL channel condition evaluation
Solution Approach 1:
For UL-only TRPs, the system performs preliminary uplink signal transmissions from the UE to the candidate UL-only cell before handover decisions. Since these TRPs have no downlink capability, the preliminary uplink actions are essential for establishing any channel quality information, enabling the network to make informed mobility decisions despite the lack of downlink measurements.
Solution Approach 2:
The patent inverts the traditional mobility measurement approach by relying on uplink transmissions rather than downlink receptions for UL-only TRPs. Instead of the network transmitting reference signals for the UE to measure (downlink approach), the UE transmits signals that the network measures (uplink approach), thereby adapting the measurement paradigm to match the capabilities of UL-only TRPs.
Data Source
AI summary
Methods and apparatuses for uplink (UL) assisted mobility. A method of operating a user equipment (UE) includes receiving one or more signals from one or more candidate cells, receiving, from a serving cell, information including configuration for a first communication element and association of the one or more signal with the first communication element, and receiving information for a first threshold. The method further includes measuring first reference signal received powers (RSRPs) for each of the one or more signals, evaluating a condition based on the first RSRPs and the first threshold, and when the condition is satisfied, transmitting the first communication element to a corresponding one of the one or more candidate cells.