3,288 research outputs found
Feasibility of In-band Full-Duplex Radio Transceivers with Imperfect RF Components: Analysis and Enhanced Cancellation Algorithms
In this paper we provide an overview regarding the feasibility of in-band
full-duplex transceivers under imperfect RF components. We utilize results and
findings from the recent research on full-duplex communications, while
introducing also transmitter-induced thermal noise into the analysis. This
means that the model of the RF impairments used in this paper is the most
comprehensive thus far. By assuming realistic parameter values for the
different transceiver components, it is shown that IQ imaging and
transmitter-induced nonlinearities are the most significant sources of
distortion in in-band full-duplex transceivers, in addition to linear
self-interference. Motivated by this, we propose a novel augmented nonlinear
digital self-interference canceller that is able to model and hence suppress
all the essential transmitter imperfections jointly. This is also verified and
demonstrated by extensive waveform simulations.Comment: 7 pages, presented in the CROWNCOM 2014 conferenc
Design and construction of a Cherenkov imager for charge measurement of nuclear cosmic rays
A proximity focusing Cherenkov imager called CHERCAM, has been built for the
charge measurement of nuclear cosmic rays with the CREAM instrument. It
consists of a silica aerogel radiator plane across from a detector plane
equipped with 1,600 1" diameter photomultipliers. The two planes are separated
by a ring expansion gap. The Cherenkov light yield is proportional to the
charge squared of the incident particle. The expected relative light collection
accuracy is in the few percents range. It leads to an expected single element
separation over the range of nuclear charge Z of main interest 1 < Z < 26.
CHERCAM is designed to fly with the CREAM balloon experiment. The design of the
instrument and the implemented technical solutions allowing its safe operation
in high altitude conditions (radiations, low pressure, cold) are presented.Comment: 24 pages, 19 figure
Reference Receiver Based Digital Self-Interference Cancellation in MIMO Full-Duplex Transceivers
In this paper we propose and analyze a novel self-interference cancellation
structure for in-band MIMO full-duplex transceivers. The proposed structure
utilizes reference receiver chains to obtain reference signals for digital
self-interference cancellation, which means that all the transmitter-induced
nonidealities will be included in the digital cancellation signal. To the best
of our knowledge, this type of a structure has not been discussed before in the
context of full-duplex transceivers. First, we will analyze the overall
achievable performance of the proposed cancellation scheme, while also
providing some insight into the possible bottlenecks. We also provide a
detailed formulation of the actual cancellation procedure, and perform an
analysis into the effect of the received signal of interest on
self-interference coupling channel estimation. The achieved performance of the
proposed reference receiver based digital cancellation procedure is then
assessed and verified with full waveform simulations. The analysis and waveform
simulation results show that under practical transmitter RF/analog impairment
levels, the proposed reference receiver based cancellation architecture can
provide substantially better self-interference suppression than any existing
solution, despite deploying only low-complexity linear digital processing.Comment: 7 pages, 4 figures. To be presented in the 2014 IEEE Broadband
Wireless Access Worksho
Simultaneous Transmission and Reception: Algorithm, Design and System Level Performance
Full Duplex or Simultaneous transmission and reception (STR) in the same
frequency at the same time can potentially double the physical layer capacity.
However, high power transmit signal will appear at receive chain as echoes with
powers much higher than the desired received signal. Therefore, in order to
achieve the potential gain, it is imperative to cancel these echoes. As these
high power echoes can saturate low noise amplifier (LNA) and also digital
domain echo cancellation requires unrealistically high resolution
analog-to-digital converter (ADC), the echoes should be cancelled or suppressed
sufficiently before LNA. In this paper we present a closed-loop echo
cancellation technique which can be implemented purely in analogue domain. The
advantages of our method are multiple-fold: it is robust to phase noise, does
not require additional set of antennas, can be applied to wideband signals and
the performance is irrelevant to radio frequency (RF) impairments in transmit
chain. Next, we study a few protocols for STR systems in carrier sense multiple
access (CSMA) network and investigate MAC level throughput with realistic
assumptions in both single cell and multiple cells. We show that STR can reduce
hidden node problem in CSMA network and produce gains of up to 279% in maximum
throughput in such networks. Finally, we investigate the application of STR in
cellular systems and study two new unique interferences introduced to the
system due to STR, namely BS-BS interference and UE-UE interference. We show
that these two new interferences will hugely degrade system performance if not
treated appropriately. We propose novel methods to reduce both interferences
and investigate the performances in system level.Comment: 20 pages. This manuscript will appear in the IEEE Transactions on
Wireless Communication
Solid motor diagnostic instrumentation
A review of typical surveillance and monitoring practices followed during the flight phases of representative solid-propellant upper stages and apogee motors was conducted to evaluate the need for improved flight diagnostic instrumentation on future spacecraft. The capabilities of the flight instrumentation package were limited to the detection of whether or not the solid motor was the cause of failure and to the identification of probable primary failure modes. Conceptual designs of self-contained flight instrumentation packages capable of meeting these reqirements were generated and their performance, typical cost, and unit characteristics determined. Comparisons of a continuous real time and a thresholded hybrid design were made on the basis of performance, mass, power, cost, and expected life. The results of this analysis substantiated the feasibility of a self-contained independent flight instrumentation module as well as the existence of performance margins by which to exploit growth option applications
On-Orbit Validation of a Framework for Spacecraft-Initiated Communication Service Requests with NASA's SCaN Testbed
We design, analyze, and experimentally validate a framework for demand-based allocation of high-performance space communication service in which the user spacecraft itself initiates a request for service. Leveraging machine-to-machine communications, the automated process has potential to improve the responsiveness and efficiency of space network operations. We propose an augmented ground station architecture in which a hemispherical-pattern antenna allows for reception of service requests sent from any user spacecraft within view. A suite of ground-based automation software acts upon these direct-to-Earth requests and allocates access to high-performance service through a ground station or relay satellite in response to immediate user demand. A software-defined radio transceiver, optimized for reception of weak signals from the helical antenna, is presented. Design and testing of signal processing equipment and a software framework to handle service requests is discussed. Preliminary results from on-orbit demonstrations with a testbed onboard the International Space Station are presented to verify feasibility of the concept
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