152 research outputs found
A New Proposed PDF for the Sub-Optimum Receiver Architecture
The detection performance of communication systems in general is limited by the presence of undesirable energy in the received signal. And this undesirable energy at communication receiver is modeled as the sum of gaussian noise and impulsive interference for which closed form probability density function generally does not exist. Due to this implementation of optimum receivers becomes very difficult. In this paper an alternate PDF is proposed written in closed form which provides a much simple architecture
Multi-band OFDM UWB receiver with narrowband interference suppression
A multi band orthogonal frequency division multiplexing (MB-OFDM) compatible
ultra wideband (UWB) receiver with narrowband interference (NBI) suppression
capability is presented. The average transmit power of UWB system is limited to
-41.3 dBm/MHz in order to not interfere existing narrowband systems. Moreover, it
must operate even in the presence of unintentional radiation of FCC Class-B compatible
devices. If this unintentional radiation resides in the UWB band, it can jam the
communication. Since removing the interference in digital domain requires higher dynamic
range of analog front-end than removing it in analog domain, a programmable
analog notch filter is used to relax the receiver requirements in the presence of NBI.
The baseband filter is placed before the variable gain amplifier (VGA) in order to reduce
the signal swing at the VGA input. The frequency hopping period of MB-OFDM
puts a lower limit on the settling time of the filter, which is inverse proportional to
notch bandwidth. However, notch bandwidth should be low enough not to attenuate
the adjacent OFDM tones. Since these requirements are contradictory, optimization
is needed to maximize overall performance. Two different NBI suppression schemes
are tested. In the first scheme, the notch filter is operating for all sub-bands. In the
second scheme, the notch filter is turned on during the sub-band affected by NBI.
Simulation results indicate that the UWB system with the first and the second suppression
schemes can handle up to 6 dB and 14 dB more NBI power, respectively. The results of this work are not limited to MB-OFDM UWB system, and can be
applied to other frequency hopping systems
Modeling and Analysis of Cellular Networks Using Stochastic Geometry: A Tutorial
This paper presents a tutorial on stochastic geometry (SG)-based analysis for cellular networks. This tutorial is distinguished by its depth with respect to wireless communication details and its focus on cellular networks. This paper starts by modeling and analyzing the baseband interference in a baseline single-tier downlink cellular network with single antenna base stations and universal frequency reuse. Then, it characterizes signal-to-interference-plus-noise-ratio and its related performance metrics. In particular, a unified approach to conduct error probability, outage probability, and transmission rate analysis is presented. Although the main focus of this paper is on cellular networks, the presented unified approach applies for other types of wireless networks that impose interference protection around receivers. This paper then extends the unified approach to capture cellular network characteristics (e.g., frequency reuse, multiple antenna, power control, etc.). It also presents numerical examples associated with demonstrations and discussions. To this end, this paper highlights the state-of-the-art research and points out future research directions
Modeling and Mitigation of Wireless Communications Interference for Spectrum Sharing with Radar
Due to both economic incentives and policy mandates, researchers increasingly face the challenge of enabling spectrum sharing between radar and wireless communications systems. In the past eight years, researchers have begun to suggest a wide variety of approaches to radar-communications spectrum sharing, ranging from transmitter design to receiver design, from spatial to temporal to other-dimensional multiplexing, and from cooperative to non-cooperative sharing. Within this diverse field of innovation, this dissertation makes two primary contributions. First, a model for wireless communications interference and its effects on adaptive-threshold radar detection is proposed. Based on both theoretical and empirical study, we find evidence for both Gaussian and non-Gaussian communications interference models, depending on the modeling situation. Further, such interference can impact radar receivers via two mechanisms—model mismatch and boost to the underlying noise floor—and both mechanisms deserve attention. Second, an innovative signal processing algorithm is proposed for radar detection in the presence of cyclostationary, linearly-modulated, digital communications (LMDC) interference (such as OFDM or CDMA) and a stationary background component. The proposed detector consists of a novel whitening filter followed by the traditional matched filter. Performance results indicate that the proposed cyclostationary-based detector outperforms a standard equivalent detector based on a stationary interference model, particularly when the number of cyclostationary LMDC transmitters is small and their interference-to-noise ratio (INR) is large relative to the stationary background
Deliverable D4.1: VLC modulation schemes
This report presents the
analysis of different modulation schemes D4.1 for VLC systems
of
the VIDAS project.
Considering the final
prototype design and
application, the
deliverable D4.1 was projected.
The
detail analysis of various modulation schemes are carried out and a robust technique
based on direct sequence spread spectrum (DSSS) is followed. DSSS technique though
necessitates use of high bandwidth while minimizing the effect of noise. Since the final
application does not require very high dat
a rate of transmission but robustness against the
noise (external lights)
becomes necessary. The analysis is followed by model development
using Matlab/Simulink.
The performance of both of these systems are compared and
evaluated.
Some of the simulation
results are presented
Multi-band OFDM UWB receiver with narrowband interference suppression
A multi band orthogonal frequency division multiplexing (MB-OFDM) compatible
ultra wideband (UWB) receiver with narrowband interference (NBI) suppression
capability is presented. The average transmit power of UWB system is limited to
-41.3 dBm/MHz in order to not interfere existing narrowband systems. Moreover, it
must operate even in the presence of unintentional radiation of FCC Class-B compatible
devices. If this unintentional radiation resides in the UWB band, it can jam the
communication. Since removing the interference in digital domain requires higher dynamic
range of analog front-end than removing it in analog domain, a programmable
analog notch filter is used to relax the receiver requirements in the presence of NBI.
The baseband filter is placed before the variable gain amplifier (VGA) in order to reduce
the signal swing at the VGA input. The frequency hopping period of MB-OFDM
puts a lower limit on the settling time of the filter, which is inverse proportional to
notch bandwidth. However, notch bandwidth should be low enough not to attenuate
the adjacent OFDM tones. Since these requirements are contradictory, optimization
is needed to maximize overall performance. Two different NBI suppression schemes
are tested. In the first scheme, the notch filter is operating for all sub-bands. In the
second scheme, the notch filter is turned on during the sub-band affected by NBI.
Simulation results indicate that the UWB system with the first and the second suppression
schemes can handle up to 6 dB and 14 dB more NBI power, respectively. The results of this work are not limited to MB-OFDM UWB system, and can be
applied to other frequency hopping systems
An Investigation of Orthogonal Wavelet Division Multiplexing Techniques as an Alternative to Orthogonal Frequency Division Multiplex Transmissions and Comparison of Wavelet Families and Their Children
Recently, issues surrounding wireless communications have risen to prominence because of the increase in the popularity of wireless applications. Bandwidth problems, and the difficulty of modulating signals across carriers, represent significant challenges. Every modulation scheme used to date has had limitations, and the use of the Discrete Fourier Transform in OFDM (Orthogonal Frequency Division Multiplex) is no exception. The restriction on further development of OFDM lies primarily within the type of transform it uses in the heart of its system, Fourier transform. OFDM suffers from sensitivity to Peak to Average Power Ratio, carrier frequency offset and wasting some bandwidth to guard successive OFDM symbols. The discovery of the wavelet transform has opened up a number of potential applications from image compression to watermarking and encryption. Very recently, work has been done to investigate the potential of using wavelet transforms within the communication space. This research will further investigate a recently proposed, innovative, modulation technique, Orthogonal Wavelet Division Multiplex, which utilises the wavelet transform opening a new avenue for an alternative modulation scheme with some interesting potential characteristics. Wavelet transform has many families and each of those families has children which each differ in filter length. This research consider comprehensively investigates the new modulation scheme, and proposes multi-level dynamic sub-banding as a tool to adapt variable signal bandwidths. Furthermore, all compactly supported wavelet families and their associated children of those families are investigated and evaluated against each other and compared with OFDM. The linear computational complexity of wavelet transform is less than the logarithmic complexity of Fourier in OFDM. The more important complexity is the operational complexity which is cost effectiveness, such as the time response of the system, the memory consumption and the number of iterative operations required for data processing. Those
complexities are investigated for all available compactly supported wavelet families and their children and compared with OFDM. The evaluation reveals which wavelet families perform more effectively than OFDM, and for each wavelet family identifies which family children perform the best. Based on these results, it is concluded that the wavelet modulation scheme has some interesting advantages over OFDM, such as lower complexity and bandwidth conservation of up to 25%, due to the elimination of guard intervals and dynamic bandwidth allocation, which result in better cost effectiveness
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