Emerging Prototyping Activities in Joint Radar-Communications

The previous chapters have discussed the canvas of joint radar-communications (JRC), highlighting the key approaches of radar-centric, communications-centric and dual-function radar-communications systems. Several signal processing and related aspects enabling these approaches including waveform design, resource allocation, privacy and security, and intelligent surfaces have been elaborated in detail. These topics offer comprehensive theoretical guarantees and algorithms. However, they are largely based on theoretical models. A hardware validation of these techniques would lend credence to the results while enabling their embrace by industry. To this end, this chapter presents some of the prototyping initiatives that address some salient aspects of JRC. We describe some existing prototypes to highlight the challenges in design and performance of JRC. We conclude by presenting some avenues that require prototyping support in the future.Comment: Book chapter, 54 pages, 13 figures, 10 table

AirSync: Enabling Distributed Multiuser MIMO with Full Spatial Multiplexing

The enormous success of advanced wireless devices is pushing the demand for higher wireless data rates. Denser spectrum reuse through the deployment of more access points per square mile has the potential to successfully meet the increasing demand for more bandwidth. In theory, the best approach to density increase is via distributed multiuser MIMO, where several access points are connected to a central server and operate as a large distributed multi-antenna access point, ensuring that all transmitted signal power serves the purpose of data transmission, rather than creating "interference." In practice, while enterprise networks offer a natural setup in which distributed MIMO might be possible, there are serious implementation difficulties, the primary one being the need to eliminate phase and timing offsets between the jointly coordinated access points. In this paper we propose AirSync, a novel scheme which provides not only time but also phase synchronization, thus enabling distributed MIMO with full spatial multiplexing gains. AirSync locks the phase of all access points using a common reference broadcasted over the air in conjunction with a Kalman filter which closely tracks the phase drift. We have implemented AirSync as a digital circuit in the FPGA of the WARP radio platform. Our experimental testbed, comprised of two access points and two clients, shows that AirSync is able to achieve phase synchronization within a few degrees, and allows the system to nearly achieve the theoretical optimal multiplexing gain. We also discuss MAC and higher layer aspects of a practical deployment. To the best of our knowledge, AirSync offers the first ever realization of the full multiuser MIMO gain, namely the ability to increase the number of wireless clients linearly with the number of jointly coordinated access points, without reducing the per client rate.Comment: Submitted to Transactions on Networkin

Terahertz wireless communication

The goal of this thesis is to explore Terahertz (THz) wireless communication technology. More specifically the objective is to develop and characterize several THz communication systems and study the effect of atmosphere propagation through fog droplets and dust particles on THz communications. For demonstration, a THz continuous wave (CW) photomixing system is designed. Terahertz signals are phase encoded with both analog ramp signals and pseudorandom binary data, transmitted over a short distance, and detected. The limitation of transmission bandwidth, low single to noise ratio, vibration effects are also analyzed. In order to study and compare propagation features of THz links with infrared (IR) links under different weather conditions, a THz and IR communications lab setup with a maximum data rate of 2.5 Gb/s at 625 GHz carrier frequency and 1.5 gm wavelength, have been developed respectively. A usual non return-to-zero (NRZ) format is applied to modulate the IR channel but a duobinary coding technique is used for driving the multiplier chain-based 625 GHz source, which enables signaling at high data rate and higher output power. The bit-error rate (BER), signal-to-noise ratio (SNR) and power on the receiver side have been measured, which describe the signal performance. Since weather conditions such as fog and dust exhibit a spectral dependence in the atmospheric attenuation, the corresponding impact on THz in comparison with IR communications is not equivalent. Simulation results of attenuation by fog and dust in the millimeter and sub-millimeter waveband (from 0.1 to 1 THz) and infrared waveband (1.5 µm) are presented and compared. Experimentally, after THz and IR beams propagated through the same weather conditions (fog), performance of both channels are analyzed and compared. The attenuation levels for the IR beam are typically several orders of magnitude higher than those for the THz beam. Mie scattering theory was used to study the attenuation of THz and IR radiation due to the dust particle. Different amounts of dust are loaded in the chamber to generate a variety of concentration for beam propagation. As the dust loading becomes heavier, the measured attenuation becomes more severe. Under identical dust concentrations, IR wavelengths are strongly attenuated while THz shows almost no impact

Ultra-Wideband Secure Communications and Direct RF Sampling Transceivers

Larger wireless device bandwidth results in new capabilities in terms of higher data rates and security. The 5G evolution is focus on exploiting larger bandwidths for higher though-puts. Interference and co-existence issues can also be addressed by the larger bandwidth in the 5G and 6G evolution. This dissertation introduces of a novel Ultra-wideband (UWB) Code Division Multiple Access (CDMA) technique to exploit the largest bandwidth available in the upcoming wireless connectivity scenarios. The dissertation addresses interference immunity, secure communication at the physical layer and longer distance communication due to increased receiver sensitivity. The dissertation presents the design, workflow, simulations, hardware prototypes and experimental measurements to demonstrate the benefits of wideband Code-Division-Multiple-Access. Specifically, a description of each of the hardware and software stages is presented along with simulations of different scenarios using a test-bench and open-field measurements. The measurements provided experimental validation carried out to demonstrate the interference mitigation capabilities. In addition, Direct RF sampling techniques are employed to handle the larger bandwidth and avoid analog components. Additionally, a transmit and receive chain is designed and implemented at 28 GHz to provide a proof-of-concept for future 5G applications. The proposed wideband transceiver is also used to demonstrate higher accuracy direction finding, as much as 10 times improvement

A Vector Channel Based Approach to MIMO Radar Waveform Design for Extended Targets

Radar systems have been used for many years for estimating, detecting, classifying, and imaging objects of interest (targets). Stealthier targets and more cluttered environments have created a need for more sophisticated radar systems to gain more precise information about the radar environment. Because modern radar systems are largely defined in software, adaptive radar systems have emerged that tailor system parameters such as the transmitted waveform and receiver filter to the target and environment in order to address this need. The basic structure of a radar system exhibits many similarities to the structure of a communication system. Recognizing the parallel composition of radar systems and information transmission systems, initial works have begun to explore the application of information theory to radar system design, but a great deal of work still remains to make a full and clear connection between the problems addressed by radar systems and communication systems. Forming a comprehensive definition of this connection between radar systems and information transmission systems and associated problem descriptions could facilitate the cross-discipline transfer of ideas and accelerate the development and improvement of new system design solutions in both fields. In particular, adaptive radar system design is a relatively new field which stands to benefit from the maturity of information theory developed for information transmission if a parallel can be drawn to clearly relate similar radar and communication problems. No known previous work has yet drawn a clear parallel between the general multiple-input multiple-output (MIMO) radar system model considering both the detection and estimation of multiple extended targets and a similar multiuser vector channel information transmission system model. The goal of this dissertation is to develop a novel vector channel framework to describe a MIMO radar system and to study information theoretic adaptive radar waveform design for detection and estimation of multiple radar targets within this framework. Specifically, this dissertation first provides a new compact vector channel model for representing a MIMO radar system which illustrates the parallel composition of radar systems and information transmission systems. Second, using the proposed framework this dissertation contributes a compressed sensing based information theoretic approach to waveform design for the detection of multiple extended targets in noiseless and noisy scenarios. Third, this dissertation defines the multiple extended target estimation problem within the framework and proposes a greedy signal to interference-plus-noise ratio (SINR) maximizing procedure based on a similar approach developed for a collaborative multibase wireless communication system to optimally design wave forms in this scenario

COMPUTATIONAL ANALYSIS OF CODE-MULTIPLEXED COULTER SENSOR SIGNALS

Nowadays, lab-on-a-chip (LoC) technology has been applied in a variety of applications because of its capability to perform accurate microscale manipulations of cells for point-of-care diagnostics. On the other hand, such a result is not readily available from an LoC device and typically still requires a post-inspection of the chip using traditional laboratory equipment such as a microscope, negating the advantages of the LoC technology. To solve this dilemma, my doctoral research mainly focuses on developing portable and disposable biosensors for interfacing with and digitizing the information from an LoC system. Our sensor platform, integrated with multiple microfluidic impedance sensors, electrically monitors and tracks manipulated cells on an LoC device. The sensor platform compresses information from each sensor into a 1-dimensional electrical waveform, and therefore, further signal processing is required to recover the readout of each sensor and extract information of detected cells. Furthermore, with the capability of the sensor platform, we have introduced integrated microfluidic cytometers to characterize properties of cells such as cell surface expression and mechanical properties.Ph.D

Analysis and correction of the helium speech effect by autoregressive signal processing

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