INTRODUCTION

Nowadays smartphones, internet of things (IoT) and many other wireless
devices are carried around by everyone and have to work in environments
that from a technical perspective are very far from ideal. Wireless
channels have many complex problems that need to be solved to guarantee
a reliable communication link.

Among the multitude of problems, a common issue that observed in
wireless channels is what is called "multipath fading effect". Multipath
refers to the fact electromagnetic waves (EMWs) radiated from a sender
antenna may take different paths by reflecting on multiple surfaces
before reaching the receiver (see figure). Because EMWs travel at a
constant speed, and some paths are longer than others, the receiver sees
multiple overlapped (superimposed) copies of the sent signal, each with
a different phase shift. In practice only one path is desirable, thus
the other delayed copies cause a degradation of the received signal
(fading).

TASK DESCRIPTION

The goal of the project is to develop a platform to illustrate the
impact of different fading effects on the received signal. The platform
is thus built for pedagogical purposes and ought to show the various
parts of the signal processing chain of a receiver.

METHODS

Two USRP B210 software defined radio (SDR) devices from Ettus Reasearch,
together with the open source software libraries GNU Radio and Dear
PyGUI were used to create a graphical user interface to display
waveforms from either a simulated or real wireless links affected by
multipath fading. The platform transmits a picture either using QPSK or
16ary QAM over a 2.4 GHz carrier and computes the empirical bit error
rate of the link.