Auxiliary Synchronization Signal for Dormant Cell Detection
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Solution Overview
Problem
In LTE systems, the detection of cells with dormant or low-activity states is challenging due to the absence of primary and secondary synchronization signals (PSS/SSS) and cell-specific reference signals (CRS), leading to difficulties in radio link monitoring and higher latency, especially in dense small cell deployments with high interference.
Innovation Solution
The introduction of an auxiliary synchronization signal (AuSS) or discovery signal that includes cell detection information, allowing wireless transmit/receive units (WTRUs) to autonomously determine cell states and timing information, even when legacy signals are not transmitted, by processing the AuSS with respect to the serving cell's timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If cells apply discontinuous transmission or on/off operation to reduce energy consumption and interference, then energy efficiency and interference reduction are improved, but cell detection and radio link monitoring become difficult or impossible
Solution Approach 1:
The patent extracts the essential cell detection function from the traditional continuous transmission framework by introducing a separate discovery signal mechanism. This discovery signal is transmitted independently of the main data transmission, allowing cells to remain dormant for energy savings while still providing detectable signals for cell search and radio link monitoring purposes.
Solution Approach 2:
The discovery signal acts as an intermediary between dormant cells and wireless transmit/receive units. It mediates the communication by providing timing information and cell identification without requiring continuous transmission from the cell, thus enabling detection while maintaining energy efficiency.
2Reliability
If cells transmit continuously to ensure reliable detection and monitoring, then cell detection reliability is improved, but energy consumption and interference increase
Solution Approach 1:
The patent implements periodic transmission of discovery signals at specific intervals rather than continuous transmission. This periodic action maintains sufficient detection reliability by ensuring cells are detectable at regular intervals while significantly reducing overall energy consumption compared to continuous transmission.
3Object-generated harmful factors
If cells use discontinuous transmission to reduce interference in dense deployments, then interference reduction is improved, but access latency increases
Solution Approach 1:
The discovery signal provides preliminary timing and identification information that enables wireless transmit/receive units to quickly identify and access cells when needed. This preliminary action reduces access latency by eliminating the need for extensive signal scanning during cell search, even though cells transmit discontinuously.
4Loss of energy
If cells remain in dormant state to save energy and reduce interference, then energy efficiency and interference reduction are improved, but radio link monitoring cannot be performed
Solution Approach 1:
The discovery signal serves multiple functions simultaneously: it enables cell detection, provides timing synchronization, and supports radio link monitoring even when cells are in dormant state. This multi-functionality allows the system to maintain monitoring capabilities while cells remain energy-efficient dormant.
Data Source
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AI summary
Cell detection information, such as cell identity, frequency, dormant/active mode, etc. may be determined. This cell detection information may be reported based on properties of a received Auxiliary Synchronization Signal (AuSS) or discovery signal. The received signal may be processed as a function of its timing, for example, with respect to timing of a serving cell. A WTRU may obtain cell detection information for a neighbor cell. A cell may also be detected by surrounding WTRUs. A WTRU may determine timing of cell reactivation from a detected property of the AuSS or discovery signal. A WTRU may trigger an RRC procedure upon selecting a dormant but temporarily reactivated cell. An eNB may transmit AuSS for a dormant cell based on detection of signals received from neighbor cells. Quasi-colocation (QCL) demodulation may be performed based on the detected signal. The on/off state of a cell may be indicated.