NEC sensor visualizes spectrum in real time to aid sharing
It is clear that spectrum sharing will be an essential element of enhanced 4G HetNets and of 5G, as virgin airwaves become hard to find. NEC has developed a radio sensing system which it says can operate in real time to visualize the state of the spectrum and enable the most effective usage.
The system supports emerging practices such as the dynamic allocation of spectrum for IoT services or for special events or emergency situations.
The solution consists of a small radio spectrum sensor and software, which extract only the signals within a target frequency between 30 MHz and 3 GHz. According to NEC tests, the system claims to perform measurements with 100 times greater sensitivity than existing technologies.
“This technology makes it possible to identify the actual use of radio frequency resources, including unused frequencies,” said Yuichi Nakamura, general manager of system platform research labs at the Japanese vendor. “This is accomplished by measuring the distribution of a radio frequency signal’s intensity and its variation over time for each frequency at each point and visualizing the measurements in real time.”
The sensor is sensitive enough to perform high precision measurements of weak radio signals in areas that are close to transmitter stations radiating strong radio signals.
NEC developed a MEMS-based tuneable filter that extracts only the radio signals at the frequency to be measure,d from the RF signals received by the antenna, combining the functions of five filters into just one, while reducing its size to about that of a smartphone. This means that a spectrum sensor no longer needs to be installed in a tower, but can be mounted on walls or street lights to increase measurement precision.
The company also says that its sensor picks up only the signals in the target direction, eliminating 99% of unnecessary signals.
The accompanying software automatically estimates the status of spectrum in places where there are no sensors installed by collecting and using a variety of actual measurement data, such as frequencies, signal intensities and measurement times. NEC hopes to have this technology adopted in a wide variety of scenarios, such as monitoring signals in crowded areas (such as stadiums, rail stations or airports), for optimization of wireless infrastructure, and detection of illegal radio stations.