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Scaling network-based spectrum analyzer with constant communication cost
e propose a spectrum analyzer that leverages many networked commodity sensor nodes, each of which sam- ples its portion in a wideband spectrum. The sensors operate in parallel and transmit their measurements over a wireless network without performing any significant computations such as FFT. The measurements are forwarded to the backend of the system where spectrum analysis takes place. In particular, we propose a solution that compresses the raw measurements in a simple random linear projection and combines the compressed measurements from multiple sensors in-network. As a result, we achieve a substantial reduction in the network bandwidth requirement to operate the proposed system. We discover that the overall communication cost can be independent of the number of sensors and is affected only by sparsity of discretized spectrum under analysis. This principle founds the basis for a claim that our network-based spectrum analyzer can scale up the number of sensor nodes to process a very wide spectrum block potentially having a GHz bandwidth. We devise a novel recovery algorithm that systematically undoes compressive encoding and in-network combining done to the raw measurements, incorporating the least squares and l1-minimization decoding used in compressive sensing, and demonstrate that the algorithm can effectively restore an accurate estimate of the original data suitable for fine- rained spectrum analysis. We present mathematical analysis and empirical evaluation of the system with software-defined radios.Engineering and Applied Science
Integrated phased array systems in silicon
Silicon offers a new set of possibilities and challenges for RF, microwave, and millimeter-wave applications. While the high cutoff frequencies of the SiGe heterojunction bipolar transistors and the ever-shrinking feature sizes of MOSFETs hold a lot of promise, new design techniques need to be devised to deal with the realities of these technologies, such as low breakdown voltages, lossy substrates, low-Q passives, long interconnect parasitics, and high-frequency coupling issues. As an example of complete system integration in silicon, this paper presents the first fully integrated 24-GHz eight-element phased array receiver in 0.18-μm silicon-germanium and the first fully integrated 24-GHz four-element phased array transmitter with integrated power amplifiers in 0.18-μm CMOS. The transmitter and receiver are capable of beam forming and can be used for communication, ranging, positioning, and sensing applications
The Physics of Communicability in Complex Networks
A fundamental problem in the study of complex networks is to provide
quantitative measures of correlation and information flow between different
parts of a system. To this end, several notions of communicability have been
introduced and applied to a wide variety of real-world networks in recent
years. Several such communicability functions are reviewed in this paper. It is
emphasized that communication and correlation in networks can take place
through many more routes than the shortest paths, a fact that may not have been
sufficiently appreciated in previously proposed correlation measures. In
contrast to these, the communicability measures reviewed in this paper are
defined by taking into account all possible routes between two nodes, assigning
smaller weights to longer ones. This point of view naturally leads to the
definition of communicability in terms of matrix functions, such as the
exponential, resolvent, and hyperbolic functions, in which the matrix argument
is either the adjacency matrix or the graph Laplacian associated with the
network. Considerable insight on communicability can be gained by modeling a
network as a system of oscillators and deriving physical interpretations, both
classical and quantum-mechanical, of various communicability functions.
Applications of communicability measures to the analysis of complex systems are
illustrated on a variety of biological, physical and social networks. The last
part of the paper is devoted to a review of the notion of locality in complex
networks and to computational aspects that by exploiting sparsity can greatly
reduce the computational efforts for the calculation of communicability
functions for large networks.Comment: Review Article. 90 pages, 14 figures. Contents: Introduction;
Communicability in Networks; Physical Analogies; Comparing Communicability
Functions; Communicability and the Analysis of Networks; Communicability and
Localization in Complex Networks; Computability of Communicability Functions;
Conclusions and Prespective
Massive MIMO for Next Generation Wireless Systems
Multi-user Multiple-Input Multiple-Output (MIMO) offers big advantages over
conventional point-to-point MIMO: it works with cheap single-antenna terminals,
a rich scattering environment is not required, and resource allocation is
simplified because every active terminal utilizes all of the time-frequency
bins. However, multi-user MIMO, as originally envisioned with roughly equal
numbers of service-antennas and terminals and frequency division duplex
operation, is not a scalable technology. Massive MIMO (also known as
"Large-Scale Antenna Systems", "Very Large MIMO", "Hyper MIMO", "Full-Dimension
MIMO" & "ARGOS") makes a clean break with current practice through the use of a
large excess of service-antennas over active terminals and time division duplex
operation. Extra antennas help by focusing energy into ever-smaller regions of
space to bring huge improvements in throughput and radiated energy efficiency.
Other benefits of massive MIMO include the extensive use of inexpensive
low-power components, reduced latency, simplification of the media access
control (MAC) layer, and robustness to intentional jamming. The anticipated
throughput depend on the propagation environment providing asymptotically
orthogonal channels to the terminals, but so far experiments have not disclosed
any limitations in this regard. While massive MIMO renders many traditional
research problems irrelevant, it uncovers entirely new problems that urgently
need attention: the challenge of making many low-cost low-precision components
that work effectively together, acquisition and synchronization for
newly-joined terminals, the exploitation of extra degrees of freedom provided
by the excess of service-antennas, reducing internal power consumption to
achieve total energy efficiency reductions, and finding new deployment
scenarios. This paper presents an overview of the massive MIMO concept and
contemporary research.Comment: Final manuscript, to appear in IEEE Communications Magazin
High Linearity Millimeter Wave Power Amplifiers with Novel Linearizer Techniques
Millimeter-wave communications have experienced phenomenal growth in recent
years when limited frequency spectrum is occupied by the ever-developing communication
services. The power amplifier, as the key component in the transmitter/receiver module
of communication systems, affects performance of the whole system directly and receives
much attention.
For minimized distortion and optimum system performance, the non-constant en-
velope modulation schemes used in communication systems have challenging requirements
on linearity. As linearity is related to communication quality directly, several linearization
techniques, such as predistortion and feedforward, are applied to power amplifier design.
Predistortion method has the advantages over other techniques in relatively simple struc-
ture and reasonable linearity improvement. But current predistortion circuits have quite
limited performance improvement and relatively large insertion loss, which indicate the
need for further research. In most of millimeter-wave amplifier design, great effort has
been spent on output power or gain, while linearity is often ignored. As almost all the
predistortion circuits operate at the RF frequencies, the linearized millimeter-wave com-
munication circuit is still relatively immature and very challenging.
This project is dedicated to solve the linearity problem faced by millimeter-wave
power amplifier in communication systems, which lacks of e®ective techniques in this field.
Linearity improvement with the predistortion method will be the key issue in this project
and some original ideas for predistortion circuit design will be applied to millimeter-wave
amplifiers.
In this thesis, several predistortion circuits with novel structure were proposed,
which provide a new approach for linearity improvement for millimeter-wave power am-
plifier. A millimeter-wave power ampli¯er for LMDS applications built on GaAs pHEMT
technology was developed to a high engineering standard, which works as the test bench
for linearization. Actual operation and parasitic elements at tens of gigahertz have been
taken into consideration during the design.
Firstly, two novel predistorter structures based on the amplifier were proposed, one
is based on an amplifier with a fixed bias circuit and the other is based on an amplifier with
a nonlinear signal dependant bias circuit. These novel structures can improve the linearity
while improving other metrics simultaneously, which can effectively solve the problem of
insertion loss faced by the conventional structures. Besides this, an original predistortion
circuit design methodology derived from frequency to signal amplitude transformation was
proposed. Based on this methodology, several transfer functions were proposed and related
predistortion circuits were built to linearize the power amplifier. As this methodology is
quite different from the traditional approach, it can improve the linearity signifficantly
while other metrics are affected slightly and has a broad prospect for application
High Linearity Millimeter Wave Power Amplifiers with Novel Linearizer Techniques
Millimeter-wave communications have experienced phenomenal growth in recent
years when limited frequency spectrum is occupied by the ever-developing communication
services. The power amplifier, as the key component in the transmitter/receiver module
of communication systems, affects performance of the whole system directly and receives
much attention.
For minimized distortion and optimum system performance, the non-constant en-
velope modulation schemes used in communication systems have challenging requirements
on linearity. As linearity is related to communication quality directly, several linearization
techniques, such as predistortion and feedforward, are applied to power amplifier design.
Predistortion method has the advantages over other techniques in relatively simple struc-
ture and reasonable linearity improvement. But current predistortion circuits have quite
limited performance improvement and relatively large insertion loss, which indicate the
need for further research. In most of millimeter-wave amplifier design, great effort has
been spent on output power or gain, while linearity is often ignored. As almost all the
predistortion circuits operate at the RF frequencies, the linearized millimeter-wave com-
munication circuit is still relatively immature and very challenging.
This project is dedicated to solve the linearity problem faced by millimeter-wave
power amplifier in communication systems, which lacks of e®ective techniques in this field.
Linearity improvement with the predistortion method will be the key issue in this project
and some original ideas for predistortion circuit design will be applied to millimeter-wave
amplifiers.
In this thesis, several predistortion circuits with novel structure were proposed,
which provide a new approach for linearity improvement for millimeter-wave power am-
plifier. A millimeter-wave power ampli¯er for LMDS applications built on GaAs pHEMT
technology was developed to a high engineering standard, which works as the test bench
for linearization. Actual operation and parasitic elements at tens of gigahertz have been
taken into consideration during the design.
Firstly, two novel predistorter structures based on the amplifier were proposed, one
is based on an amplifier with a fixed bias circuit and the other is based on an amplifier with
a nonlinear signal dependant bias circuit. These novel structures can improve the linearity
while improving other metrics simultaneously, which can effectively solve the problem of
insertion loss faced by the conventional structures. Besides this, an original predistortion
circuit design methodology derived from frequency to signal amplitude transformation was
proposed. Based on this methodology, several transfer functions were proposed and related
predistortion circuits were built to linearize the power amplifier. As this methodology is
quite different from the traditional approach, it can improve the linearity signifficantly
while other metrics are affected slightly and has a broad prospect for application
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