Tracking Reference Signal Allocation in mmWave LBT Systems
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Solution Overview
Problem
The limited effective isotropic radiated power (EIRP) at millimeter wave (mmWave) frequencies, particularly in the 60 GHz band, restricts the number of antenna elements, leading to wider antenna radiation patterns and increased inter-beam interference, which negatively impacts communication and necessitates a robust tracking reference signal (TRS) transmission mechanism.
Innovation Solution
The proposed solution involves determining synchronization signal blocks, receiving group and mapping information for tracking reference signals, and calculating time domain positions for TRS transmission based on this information, allowing for efficient and robust TRS allocation and transmission in beam-based systems using listen-before-talk (LBT) mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If listen-before-talk (LBT) mechanism is used for fair spectrum sharing, then inter-beam interference is reduced, but periodic tracking reference signals (TRS) cannot be transmitted, impacting communication reliability
Solution Approach 1:
The patent applies preliminary action by configuring TRS transmission opportunities in advance through RRC signaling, where the network node pre-determines when TRS can be transmitted based on LBT outcomes. The TRS configuration includes timing information that allows the UE to expect TRS at specific slots, enabling the system to prepare for communication while respecting LBT constraints. This resolves the contradiction by establishing communication reliability through pre-planned TRS transmission slots that accommodate LBT's interference mitigation requirements.
Solution Approach 2:
The patent implements dynamics by making TRS transmission adaptive to LBT outcomes. When LBT indicates the channel is busy, TRS transmission is dynamically adjusted or postponed. The network node and UE continuously monitor LBT results and modify TRS transmission timing accordingly. This dynamic adjustment allows the system to maintain communication reliability by ensuring TRS are transmitted when the channel is available, while still benefiting from LBT's interference reduction capability.
2Use of energy by stationary object
If limited EIRP is used due to regulations, then power consumption is controlled, but the number of antenna elements is reduced, leading to wider beams and increased inter-beam interference
Solution Approach 1:
The patent applies segmentation by dividing the TRS transmission task across multiple antenna elements and time slots. Instead of requiring all antenna elements to transmit simultaneously with high power, the system segments the TRS transmission into different spatial and temporal resources. This allows the system to work within EIRP regulations while still providing sufficient reference signals to reduce inter-beam interference through coordinated transmission across multiple elements.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting TRS transmission parameters such as timing, frequency, and spatial distribution based on the actual antenna configuration and interference conditions. The system modifies these parameters to optimize the balance between power consumption and interference reduction, allowing the limited EIRP to be utilized efficiently while maintaining communication quality through adaptive parameter adjustment.
3Device complexity
If wider antenna radiation patterns are used due to limited antenna elements, then system complexity is reduced, but the likelihood of inter-beam interference or collisions increases
Solution Approach 1:
The patent applies periodic action by implementing periodic TRS transmission at configured intervals. The TRS are transmitted periodically according to a configured pattern that allows the UE to synchronize and track the signals reliably. This periodic transmission structure simplifies the system by using regular timing patterns rather than complex adaptive modulation, while the periodic nature allows interference to be managed through time-division and the UE to expect and prepare for TRS at predictable intervals, reducing the impact of wider beams.
Data Source
AI summary
There is provided an apparatus comprising at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform: determining synchronization signal block(s) that have been transmitted in a serving cell; receiving group information of tracking reference signals, the group information comprising an indication on the synchronization signal block(s) for which a tracking reference signal has been configured in the serving cell; receiving mapping information comprising an indication on how individual tracking reference signal is mapped to a slot structure; and determining time domain position(s) of tracking reference signal(s) of the apparatus based on the group information and the mapping information.