Discovery Reference Signal Design for Small Cell Detection
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Solution Overview
Problem
Existing reference signal designs for small cell discovery in OFDM/OFDMA systems face challenges such as high inter-cell interference and large reference signal overhead, which hinder efficient detection and measurement of multiple small cells, especially in scenarios with varying cell loading and timing/frequency synchronization offsets.
Innovation Solution
A discovery reference signal (DRS) with low transmission frequency is introduced, comprising multiple reference signal types for timing and frequency synchronization, cell detection, RSRP/RSRQ measurements, and interference mitigation, utilizing RE muting to reduce interference and optimize resource element allocation for efficient small cell detection and measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing reference signal designs are reused for small cell discovery, then small cell detection can be enabled, but inter-cell interference level increases and reference signal overhead becomes large
Solution Approach 1:
The patent segments the reference signal into two distinct types: discovery reference signals (DRS) for small cell detection and cell-specific reference signals (CRS) for macrocell operations. This segmentation allows DRS to be transmitted only during small cell discovery periods with reduced frequency, thereby enabling small cell detection while minimizing inter-cell interference and reference signal overhead compared to continuously transmitting full reference signals.
2Reliability
If existing reference signal designs are reused for small cell discovery, then small cell detection can be enabled, but reference signal overhead becomes large
Solution Approach 1:
The patent implements periodic transmission of discovery reference signals (DRS) during specific discovery periods rather than continuous transmission. The DRS is transmitted at reduced frequency with periodic intervals, enabling small cell detection while significantly reducing reference signal overhead. The network can configure the periodicity and duration of DRS transmission based on small cell density and traffic conditions.
3Productivity
If small cells are deployed to enhance spectrum utilization efficiency, then system throughput improves, but inter-cell interference handling complexity increases
Solution Approach 1:
The patent introduces discovery reference signals (DRS) as an intermediary mechanism that facilitates small cell discovery and measurement without requiring complex inter-cell interference coordination. The DRS provides a dedicated reference signal specifically for small cell detection, separating the discovery function from the data transmission function, thereby simplifying interference handling compared to using existing CRS designs for both purposes.
4Measurement precision
If discovery reference signals are transmitted at high frequency, then small cell detection accuracy improves, but power consumption increases
Solution Approach 1:
The patent employs periodic transmission of discovery reference signals (DRS) at reduced frequency instead of continuous high-frequency transmission. The DRS is transmitted during specific discovery periods with configurable periodicity, enabling small cell detection while significantly reducing power consumption. The network can adjust the periodicity based on requirements for detection accuracy and power efficiency.
Data Source
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AI summary
A method of small cell discovery and RSRP/RSRQ measurements in OFDM/OFDMA systems is proposed. A discovery reference signal (DRS) with low transmission frequency is introduced to support small cell detection within a short time, multiple small cell discovery, and accurate measurement of multiple small cells. The DRS consists of one or multiple reference signal types with the functionalities including timing and frequency synchronization, cell detection, RSRP/RSSI/RSRQ measurements, and interference mitigation. RE muting is configured for the DRS to reduce interference level from data to DRS for discovery and RSRP/RSRQ measurements for small cells.