With a satellite waveform on your smartphone you could safely move outside normal GSM coverage and still have the connectivity you look for and with this utilising the smartphone that you normally use for communication to the surrounding world. Having a smartphone-based waveform provides benefits such as reduced costs and increased portability. In the following we will describe how such a smartphone waveform could be built.
Getting access to satellite data services often requires expensive end-user terminals to be acquired, set up and maintained. In this project, we studied, developed and successfully demonstrated a prototype smartphone based satellite software-defined radio waveform, that could in principle be used with a generic small and cheap radio module, while all waveform specific functions are delegated to run on the smartphone. Today’s smartphone are rich processing platforms that can easily handle the load of baseband modulation of a M2M satellite waveforms that do not support nor require high symbol rates.
The concept is to have a small radio module that connects to a smartphone via Bluetooth. The radio module performs the up/down conversion L-Band transmissions, while an app on the smartphone performs all base-band processing, modulation, receiver synchronisation and air interface protocol communications. The app presents a user interface with messaging/chat and status functions, or can provide remote control and monitoring for other devices.
The prototype was implemented using the Ettus Research E100 platform. A Bluetooth transport was used for exchange of digital base-band samples. The front-end module performs amplification and duplexing of the L-band RF signals. An off-the-shelf antenna was used for the prototype. For testing purposes, a network emulator was developed to run on a PC, using a separate USRP platform connected to the prototype. This allows system-level testing of the prototype before on-air trials. Finally, the prototype was tested on-air on a commercial service.
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- Thomas S. Jensen