84 research outputs found
a novel physical layer scheme based on superposition codes
Abstract The recently proposed superposition codes (SCs) have been mathematically proved to be decoded at any rate below the capacity, for additive white Gaussian noise (AWGN) channels. The main objective of this paper is to study the feasibility of a novel SC approach as an alternative to the traditional way of designing modern physical (PHY) layer schemes. Indeed, currently, PHY solutions are based on the decomposition into two separate problems of modulation shaping and coding over finite alphabets. Since superposition codes are defined over real numbers, modulation and coding can be jointly realized. Moreover, a fast decoding method is developed and tested by comparing the obtained results with both the uncoded system performance and two approximate message passing (AMP) algorithms. Finally, possible perspective to fifth generation (5G) applications exploiting SC solutions are outlined in the paper, and some interesting relations with sparse signal recovery are analyzed for further future research lines
Intra-Body Communications for Nervous System Applications: Current Technologies and Future Directions
The Internet of Medical Things (IoMT) paradigm will enable next generation
healthcare by enhancing human abilities, supporting continuous body monitoring
and restoring lost physiological functions due to serious impairments. This
paper presents intra-body communication solutions that interconnect implantable
devices for application to the nervous system, challenging the specific
features of the complex intra-body scenario. The presented approaches include
both speculative and implementative methods, ranging from neural signal
transmission to testbeds, to be applied to specific neural diseases therapies.
Also future directions in this research area are considered to overcome the
existing technical challenges mainly associated with miniaturization, power
supply, and multi-scale communications.Comment: https://www.sciencedirect.com/science/article/pii/S138912862300163
A Kalman Based Hybrid Precoding for Multi-User Millimeter Wave MIMO Systems
Millimeter-wave communication in the 60-GHz band requires large antenna arrays at both the transmit and receive terminals to achieve beamforming gains, in order to counteract the high pathloss. Fully digital techniques are infeasible with large antenna arrays due to hardware constraints at such frequencies, while purely analog solutions suffer severe performance limitations. Hybrid analog/digital beamforming is a promising solution, especially, when extended to a multi-user scenario. This paper conveys three main contributions: 1) a Kalman-based formulation for hybrid analog/digital precoding in multi-user environment is proposed; 2) an analytical expression of the error between the transmitted and estimated data is formulated, so that the Kalman algorithm at the base station does not require information on the estimated data at the mobile stations, and instead, relies only on the precoding/combining matrix; and 3) an iterative solution is designed for the hybrid precoding scheme with affordable complexity. Simulation results confirm significant improvement of the proposed approach in terms of both bit error rate and spectral efficiency–achieving almost 7 b/s/Hz, at 20 dB with 10 channel paths with respect to the analog-only beamsteering, and almost 1 b/s/Hz with respect to the hybrid minimum mean square error precoding under the same conditions
Linear approximation of CPM signals for a reduced-complexity, multi-mode telemetry transmitter
In space applications, hardware (HW) implementation is made more expensive
not only by the levels of performance required, but also by complex and
rigorous HW qualification tests. Reducing qualification cost and time is thus a
key design requirement. In this paper, a new versatile transmitter is proposed
for space telemetry, capable of soft-switching across different linear and
continuous phase modulation schemes while maintaining the same hardware
structure. This permits a single HW qualification to ``cover'' diverse uses of
the same hardware, and thus avoid re-qualification in case of configuration
changes. The envisaged solution foresees the use of a single filter, suitable
not only for linear modulations such as M-QAM, but also for continuous phase
modulation methods. At this stage, we focus on pulse code modulation/frequency
modulation (PCM/FM), for which we propose a minimum mean square error (MMSE)
algorithm. The proposed algorithm, which adds to the system flexibility and
effectiveness, may use a single first filter based on Laurent decomposition for
initialization, if needed. Performances are assessed using the mean square
error (MSE) measure between the proposed MMSE-modulated signal and the
completely modulated signal. Simulation results confirm that the proposed
algorithm leads to MSE values that are lower than the case of Laurent
decomposition using the first component only.Comment: to be published in the IEEE ICC 2023 Conference Proceedings: SAC
Satellite and Space Communications Trac
Backscattering UWB/UHF hybrid solutions for multi-reader multi-tag passive RFID systems
Ultra-wideband (UWB) technology is foreseen as a promising solution to overcome the limits of ultra-high frequency (UHF) techniques toward the development of green radio frequency identification (RFID) systems with low energy consumption and localization capabilities. While UWB techniques have been already employed for active tags, passive tags solutions are more appealing also due to their lower cost. With the fundamental requirement of maintaining backward compatibility in the RFID domain, we propose a hybrid UWB/UHF architecture to improve passive tag identification both in single-reader and multi-reader scenarios. We then develop two hybrid algorithms: the first one exploits the UWB signal to improve ISO/IEC 18000-6C UHF standard, while the other one exploits UWB to enhance a compressive sensing (CS) technique for tag identification in the multi-reader, multi-tag scenario. Both solutions are able to improve success rate and reading speed in the tag identification process and reduce the energy consumption. The multi-reader version of the proposed approaches is based on a cooperative scheme in order to manage reader-tag collisions and reader-reader collisions besides the typical tag-tag collisions. Furthermore, timing synchronization non-idealities are analyzed for the proposed solutions and simulation results reveal the effectiveness of the developed schemes
Please, sir, pull down your socks!
A 48-year-old male patient presented at the regular followupvisit seven months after a successful kidney transplant.After discussion of blood chemistries with the doctor, thepatient underwent a physical examination. As usual, heunbuttoned his shirt and undid his trouser belt. Inspectionof the limbs, after pulling up his trousers, confirmed thepresence of ankle oedema; the graft was quite firm, with nomurmurs in the area
Modem asincrono giga ethernet con interfaz ip para equipos de radio enlace.
Módem asíncrono giga ethernet con interfaz IP para
equipos de radio enlace.
El módem comprende un modulador y un
demodulador de tipo convencional que presenta la
novedad de utilizar un único oscilador fijo (7) para
gobernar el funcionamiento del modulador y
demodulador. El demodulador comprende un módulo
recuperador de tiempo de símbolo en el que se utiliza
una de las componentes Y-Q de la modulación en
cuadratura, como maestra y la otra como esclava,
para recuperar la señal digital de las componentes de
cada símbolo de forma totalmente ciega sin ayuda de
secuencias de alineamiento.
Además permite su aplicación para realizar el envío
de señales mediante polarización horizontal y vertical
integrando en un único módem tanto las señales
polarizadas verticalmente como el de las polarizadas
horizontalmente; que mediante un multiplexor de
polarización cruzada integrado en una ODU, se
conecta a una única antena (24) para
emisión/recepción de señales polarizadas vertical y
horizontalmente, con una alta capacidad de
transmisión/recepción
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