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A survey of handover algorithms in DVB-H
Digital Video Broadcasting for Handhelds (DVB-H) is a standard for
broadcasting IP Datacast (IPDC) services to mobile handheld terminals.
Based on the DVB-T standard, DVB-H adds new features such as time
slicing, MPE-FEC, in-depth interleavers, mandatory cell id identifier,
optional 4K-modulation mode and the use of 5 MHz bandwidth in addition
to the usually used 6, 7, or 8 MHz raster. IPDC over DVB-H is proposed
for ETSI to complement the DVB-H standard by combining IPDC and
DVB-H in an end-to-end system. Handover in such unidirectional broadcasting
networks is a novel issue. In the last few years since the birth of
DVB-H technology, great attention has been given to the performance
analysis of DVB-H mobile terminals. Handover is one of the main research
topics for DVB-H in mobile scenarios. Better reception quality and greater
power efficiency are considered to be the main targets of handover
research for DVB-H. New algorithms for different handover stages in
DVB-H have been the subject of recent research and are currently being
studied. Further novel algorithms need to be designed to improve the
mobile reception quality. This article provides a comprehensive survey of
the handover algorithms in DVB-H. A systematic evaluation and categorization
approach is proposed based on the problems the algorithms solve
and the handover stages being focused on. Criteria are proposed and analyzed
to facilitate designing better handover algorithms for DVB-H that
have been identified from the research conducted by the author
Optimal waste stream discharge temperature selection for dryer operations using thermo-economic assessment
A typical drying process that has liquid and gas discharge streams has been analysed and the impact of selecting various combinations of soft temperatures on heat recovery, utility targets, area targets, capital cost and total cost is reported. The method is based on the plus-minus principle and traditional pinch analysis methods for utility, area and capital cost targeting with the modification of using a ΔT contribution. Results show that there is significant benefit from optimising discharge temperatures for total cost. To achieve minimum energy consumption and total cost, heat recovery from the dryer exhaust air is necessary. Heat recovery from liquid heat sources is shown to be preferable over gas streams due to a higher film coefficient resulting in less heat exchanger area and capital cost. There is also value in making process modifications, such as combining streams or removing small streams to be solely heated by utility, to reduce the number of network heat exchangers. For the best case, the discharge temperatures of the leaving streams are 18.0 °C for water condensate (liquid stream) and 52.4 °C for the exhaust air (gas stream)
Adaptive and Iterative Multi-Branch MMSE Decision Feedback Detection Algorithms for MIMO Systems
In this work, decision feedback (DF) detection algorithms based on multiple
processing branches for multi-input multi-output (MIMO) spatial multiplexing
systems are proposed. The proposed detector employs multiple cancellation
branches with receive filters that are obtained from a common matrix inverse
and achieves a performance close to the maximum likelihood detector (MLD).
Constrained minimum mean-squared error (MMSE) receive filters designed with
constraints on the shape and magnitude of the feedback filters for the
multi-branch MMSE DF (MB-MMSE-DF) receivers are presented. An adaptive
implementation of the proposed MB-MMSE-DF detector is developed along with a
recursive least squares-type algorithm for estimating the parameters of the
receive filters when the channel is time-varying. A soft-output version of the
MB-MMSE-DF detector is also proposed as a component of an iterative detection
and decoding receiver structure. A computational complexity analysis shows that
the MB-MMSE-DF detector does not require a significant additional complexity
over the conventional MMSE-DF detector, whereas a diversity analysis discusses
the diversity order achieved by the MB-MMSE-DF detector. Simulation results
show that the MB-MMSE-DF detector achieves a performance superior to existing
suboptimal detectors and close to the MLD, while requiring significantly lower
complexity.Comment: 10 figures, 3 tables; IEEE Transactions on Wireless Communications,
201
Recurrent geomagnetic storms and relativistic electron enhancements in the outer magnetosphere: ISTP coordinated measurements
New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth\u27s magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent geomagnetic activity. It is concluded that even during extremely quiet solar conditions (sunspot minimum) there are discernible coronal holes and resultant solar wind streams which can produce intense magnetospheric particle acceleration. As a practical consequence of this Sun-Earth connection, it is noted that a long-lasting E\u3e1MeV electron event in late March 1996 appears to have contributed significantly to a major spacecraft (Anik E1) operational failure
Magnetic inversion as a mechanism for the spectral transition of black hole binaries
A mechanism for the transition between low/hard, high/soft, and steep power
law (SPL) spectral states in black hole X-ray binaries is proposed. The
low/hard state is explained by the development of a magnetically arrested
accretion disk attributable to the accumulation of a vertical magnetic field in
a central bundle. This disk forms powerful jets and consists of thin spiral
accretion streams of a dense optically thick plasma surrounded by hot,
magnetized, optically thin corona, which emits most of the energy in hard
X-rays. State transition occurs because of the quasi-periodic or random
inversion of poloidal magnetic fields in the accretion flow supplied by the
secondary star. The inward advection of the inverted field results in a
temporal disappearance of the central bundle caused by the annihilation of the
opposed fields and restoration of the optically thick disk in the innermost
region. This disk represents the high/soft state. The SPL state develops at the
period of intensive field annihilation and precedes the high/soft state. The
continuous supply of the inverted field leads to a new low/hard state because
of the formation of another magnetically arrested disk.Comment: 5 plot files are attached separately. Accepted by the ApJ
Multi-wavelength diagnostics of accretion in an X-ray selected sample of CTTSs
High resolution X-ray spectroscopy has revealed soft X-rays from high density
plasma in Classical T-Tauri stars (CTTSs), probably arising from the accretion
shock region. However, the mass accretion rates derived from the X-ray
observations are consistently lower than those derived from UV/optical/NIR
studies. We aim to test the hypothesis that the high density soft X-ray
emission is from accretion by analysing optical accretion tracers from an X-ray
selected sample of CTTSs in a homogeneous manner. We analyse optical spectra of
a sample of CTTSs and calculate the accretion rates based on measuring optical
emission lines. These are then compared to the accretion rates derived from the
X-ray spectroscopy. We find that, for each CTTS in our sample, the different
optical tracers predict mass accretion rates that agree within the errors,
albeit with a spread of ~1 order of magnitude. Typically, mass accretion rates
derived from Halpha and HeI 5876 Ang are larger than those derived from Hbeta,
Hgamma and OI. When comparisons of the optical mass accretion rates are made to
the X-ray derived mass accretion rates, we find that: a) the latter are always
lower (but by varying amounts); b) the latter range within a factor of ~2
around 2x10^{-10} M_odot yr^{-1}, despite the fact that the former span a range
of ~3 orders of magnitude. We suggest that the systematic underestimation of
the X-ray derived mass accretion rates could depend on the density distribution
inside the accretion streams, where the densest part of the stream is not
visible in the X-ray band because of the absorption by the stellar atmosphere.
We also suggest that a non-negligible optical depth of X-ray emission lines
produced by post-shock accreting plasma may explain the almost constant mass
accretion rates derived in X-rays if the effect is larger in stars with larger
optical mass accretion rates.Comment: 12 pages, 4 figures. Accepted for publication by A&
A novel probabilistic data association based MIMO detector using joint detection of consecutive symbol vectors
A new probabilistic data association (PDA) approach is proposed for symbol detection in spatial multiplexing multiple-input multiple-output (MIMO) systems. By designing a joint detection (JD) structure for consecutive symbol vectors in the same transmit burst, more a priori information is exploited when updating the estimated posterior marginal probabilities for each symbol per iteration. Therefore the proposed PDA detector (denoted as PDA-JD detector) outperforms the conventional PDA detectors in the context of correlated input bit streams. Moreover, the conventional PDA detectors are shown to be a special case of the PDA-JD detector. Simulations and analyses are given to demonstrate the effectiveness of the new method
A probabilistic data association based MIMO detector using joint detection of consecutive symbol vectors
A new probabilistic data association (PDA) approach is proposed for symbol detection in spatial multiplexing multiple-input multiple-output (MIMO) systems. By designing a joint detection (JD) structure for consecutive symbol vectors in the same transmit burst, more a priori information is exploited when updating the estimated posterior marginal probabilities for each symbol per iteration. Therefore the proposed PDA detector (denoted as PDA-JD detector) outperforms the conventional PDA detectors in the context of correlated input bit streams. Moreover, the conventional PDA detectors are shown to be a special case of the PDA-JD detector. Simulations and analyses are given to demonstrate the effectiveness of the new method
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