879 research outputs found
Novel wireless modulation technique based on noise
In this paper, a new RF modulation technique is presented. Instead of using sinusoidal carriers as information bearer, pure noise is applied. This allows very simple radio architectures to be used. Spread-spectrum based technology is applied to modulate the noise bearer. Since the transmission bandwidth of the noise bearer can be made very wide, up to ultra-wideband regions, extremely large processing gains can be obtained. This will provide robustness in interference-prone environments. To avoid the local regeneration of the noise reference at the receiver, the Transmit-Reference (TR) concept is applied. In this concept, both the reference noise signal and the modulated noise signal are transmitted, together forming\ud
the bearer. The reference and modulated signals are separated by applying a time offset. By applying different delay times for different channels (users) a new multiple access scheme results based on delay: Delay Division Multiple Access (DDMA). A theoretical analysis is given for the link performance of a single-user and a multi-user system. A testbed has been built to demonstrate the concept. The demonstrator operates in a 50 MHz bandwidth centered at 2.4 GHz. Processing gains ranging from 10¿30 dB have been tested. The testbed confirms the basic behavior as predicted by the theory
Improved detection scheme for chipless RFIDs using prolate spheroidal wave function-based noise filtering
A novel, highly sensitive scheme to detect the resonance peaks in the spectrum of chipless RFID signals is presented. The detection is based on finding the zeros in the derivative of the group delay of the received signal. In order to be able to accurately detect these zeros in the presence of noise, the received signal is filtered using a prolate spheroidal wave function-based model. This allows great increases in the distance at which chipless RFIDs can be accurately read. The detection method can be used standalone or in addition to traditional amplitude-based detection schemes
A low-cost time-hopping impulse radio system for high data rate transmission
We present an efficient, low-cost implementation of time-hopping impulse
radio that fulfills the spectral mask mandated by the FCC and is suitable for
high-data-rate, short-range communications. Key features are: (i) all-baseband
implementation that obviates the need for passband components, (ii) symbol-rate
(not chip rate) sampling, A/D conversion, and digital signal processing, (iii)
fast acquisition due to novel search algorithms, (iv) spectral shaping that can
be adapted to accommodate different spectrum regulations and interference
environments. Computer simulations show that this system can provide 110Mbit/s
at 7-10m distance, as well as higher data rates at shorter distances under FCC
emissions limits. Due to the spreading concept of time-hopping impulse radio,
the system can sustain multiple simultaneous users, and can suppress narrowband
interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special
Issue on UWB - State of the Art
Performance of Bit Error Rate and Power Spectral Density of Ultra Wideband with Time Hopping Sequences.
This thesis focuses on several modulation methods for an ultra wideband (UWB) signal. These methods are pulse position modulation (PPM), binary phase shift keying (BPSK), on/off key shifting (OOK), and pulse amplitude modulation (PAM). In addition, time hopping is considered for these modulation schemes, where the capacity per time frame of time hopping PPM is studied using different spreading ratios. This thesis proves that with the addition of time hopping to all types of modulated UWB signals, the performance of power spectral density improves in all aspects, despite the increase of data per time frame. Note that despite the increase of data per frame, the bit error rate remains the same as standard non-time hopping UWB modulated signals
A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals
Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility
Radio channel characterisation and system-level modelling for ultra wideband body-centric wireless communications
PhDThe next generation of wireless communication is evolving towards user-centric networks,
where constant and reliable connectivity and services are essential. Bodycentric
wireless network (BCWN) is the most exciting and emerging 4G technology
for short (1-5 m) and very short (below 1 m) range communication systems. It has
got numerous applications including healthcare, entertainment, surveillance, emergency,
sports and military. The major difference between the BCWN and conventional
wireless systems is the radio channel over which the communication takes place. The
human body is a hostile medium from the radio propagation perspective and it is
therefore important to understand and characterise the effect of the human body on
the antenna elements, the radio propagation channel parameters and hence the system
performance. In addition, fading is another concern that affects the reliability and
quality of the wireless link, which needs to be taken into account for a low cost and
reliable wireless communication system for body-centric networks.
The complex nature of the BCWN requires operating wireless devices to provide
low power requirements, less complexity, low cost and compactness in size. Apart
from these characteristics, scalable data rates and robust performance in most fading
conditions and jamming environment, even at low signal to noise ratio (SNR) is
needed. Ultra-wideband (UWB) technology is one of the most promising candidate for
BCWN as it tends to fulfill most of these requirements. The thesis focuses on the characterisation
of ultra wideband body-centric radio propagation channel using single
and multiple antenna techniques. Apart from channel characterisation, system level
modelling of potential UWB radio transceivers for body-centric wireless network is
also proposed. Channel models with respect to large scale and delay analysis are derived
from measured parameters. Results and analyses highlight the consequences
of static and dynamic environments in addition to the antenna positions on the performance
of body-centric wireless communication channels. Extensive measurement
i
campaigns are performed to analyse the significance of antenna diversity to combat
the channel fading in body-centric wireless networks. Various diversity combining
techniques are considered in this process. Measurement data are also used to predict
the performance of potential UWB systems in the body-centric wireless networks.
The study supports the significance of single and multiple antenna channel characterisation
and modelling in producing suitable wireless systems for ultra low power
body-centric wireless networks.University of Engineering and Technology Lahore Pakista
Ultra-Wideband Technology: Characteristcs, Applications and Challenges
Ultra-wideband (UWB) technology is a wireless communication technology
designed for short-range applications. It is characterized by its ability to
generate and transmit radio-frequency energy over an extensive frequency range.
This paper provides an overview of UWB technology including its definition, two
representative schemes and some key characteristics distinguished from other
types of communication. Besides, this paper also analyses some widely used
applications of UWB technology and highlights some of the challenges associated
with implementing UWB in real-world scenarios. Furthermore, this paper expands
upon UWB technology to encompass terahertz technology, providing an overview of
the current status of terahertz communication, and conducting an analysis of
the advantages, challenges, and certain corresponding solutions pertaining to
ultra-wideband THz communication
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