Direct-to-Cell is a technology which allows common smartphone to communicate directly with satellites. The explanation is on this post.
How it works?
4G and 5G cellphones will be able to connect with satellites, without hardware modification.
The satellites
Satellites on Low Earth Orbit (LEO) play the role of cellphone towers, they are at an altitude from 500 km (310 miles) to 2000 km (1242 miles). The low altitude in relation to other satellites reduce latency, which is delay on communication. With the big satellite number on each LEO constellation, at least one will be always be available to receive and transmit cellphone signals. Currently, the largest LEO satellite constellation is the SpaceX’s Starlink.
eNodeB and 3GPP NTN
To communicate with smartphones, the satellites must have a phased antenna array and a eNodeB modem. It uses MIMO system and follows the 3GPP NTN standard, this is the release number 17 of 3GPP (Third Generation Partnership Project), specially created for mobile phone integration with satellites. This standard has a protocol which considers altitude, satellites’ speed (approximately 7.5 km/s or 16,777.02 mph) and the doppler effect.
Direct-to-Cell advantages and applications
- This technology will be useful in remote areas, where there is no cellphone towers and in case of natural disasters.
- Can allow connection and monitoring of ships, aircrafts and land transports, regardless of locais networks.
- On precision agriculture, it will possible to monitor crops, soil conditions and the weather.
- In the future, will appear Direct-to-Device, which will connect sensors and devices with satellites. Another application of Internet of Things.
Limitations of Direct-to-Cell communication
- Due to the great distance between cellphone and satellite, battery consumption increases, accelerating its discharge.
- Connection with the satellite can’t be made in close spaces. In addition, it’s necessary a clear sky, with few clouds and no rain.
- It’s vulnerable to interferences.
- Currently, its only possible to send messages.
