Joint Communication and Sensing Systems

Introduction

Figure 1: Sketch of a Join Communication and Sensing System.

In the vast field of modern wireless communication systems, Joint Communication and Sensing (JCAS) systems are like smart buddies for devices. They help smartphones, cars, airplanes, robots and many other electronic equipped devices talk to each other and understand what’s going on around them. Two important team players in JCAS are Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Time-Frequency Space (OTFS) modulation techniques – let’s dive into what they do.

OFDM: Sorting Data Efficiently

Imagine the air as a busy highway, and information is like cars trying to get to their destination. OFDM acts like a traffic manager, dividing the highway into lanes (we call them frequencies) so that lots of cars (data) can travel without crashing into each other. This way, devices can share information without causing chaos – it’s like organized data traffic.

OTFS: Navigating Changing Environments

Now, let’s talk about OTFS. It’s a bit like a super-smart GPS for signals. In a world where things can change quickly, OTFS helps signals find their way through different conditions. It’s like having a guide that helps your device stay connected even when things get a bit tricky – a reliable navigation system for signals.

How JCAS, OFDM, and OTFS Work Together

JCAS with OFDM and OTFS is like having smart helpers for devices, making sure they can talk and understand their surroundings easily. It’s all about organized data traffic and a reliable guide for signals, working together to keep our tech world, going towards sixth generation (6G) running smoothly. The typical operating frequencies of such systems are increasing to mmWave bands, i.e. to frequencies whose wavelengths are in the order of millimeters. You can imagine the precision of such systems are comparable to those wavelengths.

In a nutshell, a communicating device transmits an OFDM or OTFS modulated signal, which travels through the air, and whose journey can be a bit bumpy. Channel estimation is like the radar system figuring out the bumps in the road – understanding how the signals change as they travel. Once the radar has a good estimate of the channel, it can use this information to “equalize” the signals. In this phase, the communication signal is used as a radar device.

Figure 2: Range-Velocity map of four point targets (like cars or pedestrian) analysing the received OFDM radar echo.

Figure 3: example of scattering points of a vehicle, at mmWave.

Figure 4: performance of novel algorithms for radar sensing using commercial sensors (radar and lidar).

Equalization is like having a correction tool. If the radar knows how the signals got a bit distorted on their journey, equalization helps to straighten them out. This is crucial because it allows both trasmitting and receiving device to get a clear picture of what’s out there. It’s similar to fixing a blurry image – channel estimation and equalization work together to make sure the radar sees things clearly and can extract useful data.

Figure 5: received OTFS data after channel equalization (yellow points). The true data symbols are in red.

In summary, a JCAS system based on OFDM or OTFS sends out organized signals, analyzes the echoes, estimates how the signals change in the air, and then uses equalization to correct any distortions. This process helps the radar and, possibly, any other receiver provide accurate and reliable information about the surroundings.

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Introduction

OFDM: Sorting Data Efficiently

OTFS: Navigating Changing Environments

How JCAS, OFDM, and OTFS Work Together

Open positions

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