Signal Processing Device for Wireless Reception Sensitivity
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Solution Overview
Problem
In the 920 MHz band, the restriction on continuous transmission time limits the implementation of low-band phase locked loop (PLL) or delayed locked loop (DLL) systems, resulting in reduced reception sensitivity compared to systems without such restrictions, such as GPS, where sensitivity is limited to approximately −100 dBm to −120 dBm.
Innovation Solution
A signal processing device and method that transmit data as wireless signals in frames, with a carrier sense unit repeating carrier sense in the frequency band and a transmission control unit transmitting data frames and synchronous frames only when the frequency band is vacant, using a pseudo random number sequence known by the reception side to enhance sensitivity detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuous transmission time is restricted to short durations (e.g., 0.2 seconds), then more channels can be allocated and crosstalk is reduced, but reception sensitivity deteriorates because low-band PLL or DLL cannot be implemented
Solution Approach 1:
The transmission is divided into multiple short frames (e.g., 0.2 seconds each) instead of continuous transmission. Each frame is transmitted independently, allowing the system to comply with short transmission time restrictions while accumulating sufficient signal energy through multiple frames to maintain reception sensitivity.
Solution Approach 2:
A synchronous frame containing a known pseudo-random number sequence is transmitted before data frames. This preliminary action enables the reception device to establish phase and code synchronization in advance, allowing accurate detection of subsequent data frames even with short transmission durations.
2Productivity
If data is transmitted in short frames to comply with transmission time restrictions, then channel capacity increases, but signal-to-noise ratio decreases making detection more difficult
Solution Approach 1:
The synchronous frame is transmitted beforehand to establish synchronization. This preliminary action prepares the reception device with the correct phase and code alignment, significantly reducing the difficulty of detecting subsequent short data frames embedded in noise.
Solution Approach 2:
The system uses a known pseudo-random number sequence with specific correlation properties. By changing the parameter of using a predetermined sequence with high autocorrelation and low cross-correlation, the system can detect weak signals more easily even when transmission time is short.
3Measurement precision
If transmission power is increased to improve reception sensitivity, then signal strength increases, but power consumption of the transmitter increases
Solution Approach 1:
Instead of transmitting one long high-power signal, the system transmits multiple short frames with lower power. The segmentation of transmission time allows energy to be distributed across multiple intervals, reducing peak power consumption while maintaining cumulative signal energy for sensitive reception.
Solution Approach 2:
The synchronous frame is transmitted with sufficient power to establish synchronization, enabling subsequent data frames to be transmitted at lower power levels. This preliminary high-power transmission facilitates energy-efficient operation during the actual data transmission phase.
Data Source
AI summary
The present technology relates to a signal processing device and a method thereof that inhibits deterioration in reception sensitivity. In a case where a frequency band is vacant on the basis of a result of carrier sense, a data frame is transmitted as a wireless signal in the frequency band, and further, a synchronous frame formed of predetermined information different from that of the data frame is transmitted as a wireless signal in the frequency band in a case where the data frame is transmitted predetermined number of times within first time. In a case where the synchronous frame is detected, the data frame is detected from a reception signal of predetermined time before the synchronous frame.