Discovery Reference Signal for Small Cell Detection
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Solution Overview
Problem
In densely deployed small cell environments, user equipment (UE) faces difficulties in detecting small cells within a short time due to mutual interference and overlapping synchronization signals, making it challenging to achieve efficient cell discovery.
Innovation Solution
The introduction of a discovery reference signal (DRS) comprising a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), which can be transmitted with a different period and configuration than legacy signals, to facilitate faster and more accurate cell detection, including the use of DRS-PSS and DRS-SSS, along with other reference signals like CSI-RS, to support coarse time and frequency synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If small cells are disposed densely in the coverage of a macro cell, then the traffic handling capacity is improved, but the difficulty of detecting small cells increases
Solution Approach 1:
The discovery signal is segmented into multiple components (discovery reference signal, synchronization signals, channel estimation signals) transmitted at different time instances and frequency resources. This segmentation allows the UE to detect small cells step-by-step without being overwhelmed by the dense deployment environment, resolving the contradiction between high traffic capacity and detection difficulty.
Solution Approach 2:
The discovery signal is transmitted periodically with configurable periods and offsets. This periodic transmission pattern enables UEs to detect small cells at regular intervals without continuous interference, allowing dense small cell deployment while maintaining detectability through time-separated transmission opportunities.
2Speed
If discovery signal transmission is performed continuously, then the cell detection speed is improved, but the interference between small cells increases
Solution Approach 1:
The discovery signal uses periodic transmission with configurable periods and time offsets instead of continuous transmission. This allows cells to take turns transmitting, reducing mutual interference while maintaining acceptable detection speeds through regular periodic opportunities.
Solution Approach 2:
The discovery signal transmission is extended into the time dimension with configurable periods and offsets, rather than only frequency separation. This temporal dimension provides additional interference management capability while maintaining detection speed through optimized transmission timing.
3Device complexity
If the discovery signal uses the same time-frequency resources as legacy synchronization signals, then the device complexity is reduced, but the measurement precision deteriorates
Solution Approach 1:
The synchronization function is segmented from the legacy synchronization signals and implemented through dedicated discovery signal components (DRS-PSS, DRS-SSS) with separate time-frequency resources. This segmentation improves measurement precision by avoiding resource conflicts while maintaining manageable device complexity through standardized signal structures.
Solution Approach 2:
The discovery reference signal acts as an intermediary between the legacy synchronization signals and the channel estimation requirements. It provides a dedicated reference signal structure that mediates between the need for simple device implementation and the need for precise channel measurements in dense small cell environments.
Data Source
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AI summary
One disclosure of the present invention provides a discovery signal receiving method. The method may comprise the steps of: identifying, through a physical control format indicator channel (PCFICH) received from a small-scale cell over a first orthogonal frequency division multiplexing (OFDM) symbol of a downlink sub-frame, the position of an OFDM symbol over which a downlink control channel is received; and determining a resource region on which a discovery signal is received from the small-scale cell. In the determining step, it can be assumed that the resource region on which the discovery signal is received does not overlap a resource region on the OFDM symbol over which the downlink control channel is received.