Operating outside LTE service areas

NEC Corporation has developed device-to-device communication technology that enables emergency response personnel to transmit high-quality images from the scene of a disaster or accident when outside of the service area of the public safety long-term evolution (PS-LTE) network.

Images are essential to enabling authorities to make swift and accurate assessments in response to large-scale disasters and in the provision of security for major events. The technology is designed to support the reliable transmission of these images by enabling terminals outside of the PS-LTE network service area to detect terminals within the service area, and then access the network via the terminal that provides the fastest communication with base stations.

“By utilising this technology, images from large-scale disasters and major accidents can be transmitted via a high-speed LTE network, even when outside of the public safety LTE service area,” said Yuichi Nakamura, general manager, System Platform Research Laboratories, NEC Corporation.

“This makes it possible to obtain accurate information from the scene and to implement a swift response. We believe this technology can contribute substantially to the development of secure and safe infrastructure that reliably supports society.”

The technology was tested in a simulated disaster relief scenario where approximately 90% of terminals located indoors — which tends to fall outside of the service area — achieved communications sufficient for the transmission of images. In LTE networks, if a terminal falls outside of its service area, other terminals may act as relay stations between the isolated terminal and connected base stations. However, when selecting a relay terminal it has conventionally been difficult to detect the communication route (relay link) that enables the highest quality images.

NEC’s new technology was developed using the Relay Link Throughput Estimation Method, which estimates communication throughput based on the quality of wireless communications, taking into account the differences in the resources available for wireless communications as well as modulation/coding schemes, and then integrates the relay link. With this technology, the communications speed from an isolated terminal cooperating with a relay terminal to connect to a base station can fully be estimated and the ‘total communication speed’ can be more accurately assessed.

Communication route selection from a terminal outside of the communication area to a base station.

The relay terminal estimates the upstream speed and the terminal outside the service area estimates the speed of communications between the terminals. Based on this result, the throughput of the relay link (total communication speed from the terminal to the base station) is calculated and a relay terminal capable of generating the highest speed is selected.

The company said device-to-device communication technology was developed as part of the Ministry of Internal Affairs and Communications’ Research and Development of Device-to-Device Communication Technology for High-reliability, Low-latency Network program, which it has been involved with since 2014.

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