Iago Alonso Gómez
Undoubtedly, one of the most important stages in the development of a communication system is the validation. During this phase, the proper operation of the devices in real scenarios is checked. However, if we think in space or underwater communications examples, the verification of these systems in real environments is extremely difficult and costly. Usually, in order to try to reduce the time and/or the cost of the validation phase, real-world conditions are reproduced in laboratory using channel simulation, which also allows the reproduction of the most adverse conditions where the communications system will work.
It could be said that a channel simulator is a tool for replacing the real-world communication channel between transmitter and receiver (the effects introduced in the signal in outer space or aquatic environments in the previous examples). This is done by providing the receiver with a distorted version of the signal generated by the transmitter, using mathematical models to characterize the effects of the real channel. Unlike the real-world channel, the simulator is configured by the system tester. This controlled environment is appropriate for automating quality measurements, testing special scenarios or playing with the same conditions as many times as you want. Gradiant has developed multiple physical layer communication systems (optical, wired or wireless) including both single carrier and multicarrier techniques and SISO, MISO, SIMO and MIMO systems. To validate these projects different channel simulation solutions have been used either hardware devices or software tools. In particular Gradiant has developed a hardware simulator that can emulate channel effects such as:
- Attenuation and fading according to different statistical models.
- Device imperfections modeled adding white Gaussian noise.
- Multipath produced by reflections and scattering in the environment objects.
- Doppler caused by relative motion between transmitter and receiver.
Gradiant has its own hardware channel simulator and continues this line of research in order to provide new functionalities and extend it to new platforms, thereby maximizing its potential to be transferred to technology companies.
Image source: http://www.kn-s.dlr.de/People/Haas/multipath_propagation.jpg
