arXiv subjects

Nozhan Hosseini

Publications and source records attributed to Nozhan Hosseini.

7 recordsLinked to original sources

arXiv2020

DFT-spread-OFDM Based Chirp Transmission

In this study, we propose a framework for chirp-based communications by exploiting discrete Fourier transform-spread orthogonal frequency division multiplexing (DFT-s-OFDM). We show that a well-designed frequency-domain spectral shaping (FDSS) filter for DFT-s-OFDM can convert its single-carrier nature to a linear combination of chirps circularly translated in the time domain. Also, by exploiting the properties of the Fourier series and Bessel function of the first kind, we analytically obtain the FDSS filter for an arbitrary chirp. We theoretically show that the chirps with low ripples in the frequency domain result in a lower bit-error ratio (BER) via less noise enhancement. We also address the noise enhancement by exploiting the repetitions in the frequency. The proposed framework offers a new way to efficiently synthesize chirps that can be used in Internet-of-Things (IoT), dual-function radar and communication (DFRC) or wireless sensing applications with existing DFT-s-OFDM transceivers.

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arXiv2020

Noncoherent Multiuser Chirp Spread Spectrum: Performance with Doppler and Asynchronism

In this paper, we investigate multi user chirp spread spectrum with noncoherent detection as a continuation of our work on coherent detection in [1]. We derive the analytical bit error ratio (BER) expression for binary chirp spread spectrum (BCSS) in the presence of multiple access interference (MAI) caused by correlation with other user signals because of either asynchronism or Doppler shifts, or both, and validate with simulations. To achieve this we analyze the signal cross correlations, and compare traditional linear chirps with our recently-proposed nonlinear chirps introduced in [1] and with other nonlinear chirps from the literature. In doing so we illustrate the superior performance of our new nonlinear chirp designs in these practical conditions, for the noncoherent counterpart of [1].

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arXiv2020

Nonlinear Quasi-Synchronous Multi User Chirp Spread Spectrum Signaling

Multi user orthogonal chirp spread spectrum (OCSS) can improve the spectral inefficiency of chirp spread spectrum (CSS) but is only feasible with perfect synchronism and without any channel dispersion. Asynchronism, channel dispersion, or unexpectedly large Doppler shifts can cause multiple access interference (MAI), which degrades performance. Conditions with small timing offsets we term quasi-synchronous (QS). In this paper, we propose two new sets of nonlinear chirps to improve CSS system performance in QS conditions. We analytically and numerically evaluate cross-correlation distributions. We also derive the bit error probability for Binary CSS analytically and validate our theoretical result with both numerical and simulation results; our error probability expression is applicable to any binary time-frequency (TF) chirp waveform. Finally, we show that in QS conditions our two new nonlinear chirp designs outperform the classical linear chirp and all existing nonlinear chirps from the literature. To complete our analysis, we demonstrate that our nonlinear CSS designs outperform existing chirps in two realistic (empirically modeled) dispersive air to ground channels.

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arXiv2020

Requirements and Technologies Towards UAM: Communication, Navigation, and Surveillance

Urban air mobility (UAM) is a concept for creating an airborne transportation system that operates in urban settings with an on-board pilot and/or remote pilot in command (RPIC), or with a fully autonomous architecture. Although the passenger traffic will be mostly in and near urban environments, UAM is also being considered for air cargo, perhaps between cities. Such capability is pushing the current communication, navigation and surveillance (CNS) / air traffic management (ATM) systems that were not designed to support these types of aviation scenarios. The UAM aircraft will be operating in a congested environment, where CNS and ATM systems need to provide integrity, robustness, security, and very high availability for safety of UAM operations while evolving. As UAM is under research by academia and government agencies, the industry is driving technology towards aircraft prototypes. Critical UAM requirements are derived from command and control (C2) (particularly for RPIC scenario), data connectivity for passengers and flight systems, unmanned aircraft systems (UAS) to UAS communication to avoid collision, and data exchange for positioning and surveillance. In this paper, we study connectivity challenges and present requirements towards a robust UAM architecture through its concept of operations. In addition, we review the existing/potential CNS technologies towards UAM, i.e., 3rd generation partnership project (3GPP) fifth generation (5G) new radio (NR), navigation detect & avoid (DAA), and satellite systems and present conclusions on a future road-map for UAM CNS architecture.

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arXiv2020

Attenuation of Several Common Building Materials in Millimeter-Wave Frequency Bands: 28, 73 and 91 GHz

Future cellular systems will make use of millimeter wave (mmWave) frequency bands. Many users in these bands are located indoors, i.e., inside buildings, homes, and offices. Typical building material attenuations in these high frequency ranges are of interest for link budget calculations. In this paper, we report on a collaborative measurement campaign to find the attenuation of several typical building materials in three potential mmWave bands (28, 73, 91 GHz). Using directional antennas, we took multiple measurements at multiple locations using narrow-band and wide-band signals, and averaged out residual small-scale fading effects. Materials include clear glass, drywall (plasterboard), plywood, acoustic ceiling tile, and cinder blocks. Specific attenuations range from approximately 0.5 dB/cm for ceiling tile at 28 GHz to approximately 19 dB/cm for clear glass at 91 GHz.

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arXiv2020

UAV Command and Control, Navigation and Surveillance: A Review of Potential 5G and Satellite Systems

Drones, unmanned aerial vehicles (UAVs), or unmanned aerial systems (UAS) are expected to be an important component of 5G/beyond 5G (B5G) communications. This includes their use within cellular architectures (5G UAVs), in which they can facilitate both wireless broadcast and point-to-point transmissions, usually using small UAS (sUAS). Allowing UAS to operate within airspace along with commercial, cargo, and other piloted aircraft will likely require dedicated and protected aviation spectrum at least in the near term, while regulatory authorities adapt to their use. The command and control (C2), or control and non-payload communications (CNPC) link provides safety critical information for the control of the UAV both in terrestrial-based line of sight (LOS) conditions and in satellite communication links for so-called beyond LOS (BLOS) conditions. In this paper, we provide an overview of these CNPC links as they may be used in 5G and satellite systems by describing basic concepts and challenges. We review new entrant technologies that might be used for UAV C2 as well as for payload communication, such as millimeter wave (mmWave) systems, and also review navigation and surveillance challenges. A brief discussion of UAV-to-UAV communication and hardware issues are also provided.

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arXiv2020

Chirp Spread Spectrum Signaling for Future Air-Ground Communications

In this paper, we investigate the use of chirp spread spectrum signaling over air-ground channels. This includes evaluation of not only the traditional linear chirp, but also of a new chirp signal format we have devised for multiple access applications. This new format is more practical than prior multi-user chirp systems in the literature, because we allow for imperfect synchronism. Specifically we evaluate multi-user chirp signaling over air-ground channels in a quasi-synchronous condition. The air-ground channels we employ are models based upon an extensive NASA measurement campaign. We show that our new signaling scheme outperforms the classic linear chirp in these air-ground settings.

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