3,225 research outputs found
Joint Source-Channel Coding over a Fading Multiple Access Channel with Partial Channel State Information
In this paper we address the problem of transmission of correlated sources
over a fast fading multiple access channel (MAC) with partial channel state
information available at both the encoders and the decoder. We provide
sufficient conditions for transmission with given distortions. Next these
conditions are specialized to a Gaussian MAC (GMAC). We provide the optimal
power allocation strategy and compare the strategy with various levels of
channel state information.
Keywords: Fading MAC, Power allocation, Partial channel state information,
Correlated sources.Comment: 7 Pages, 3 figures. To Appear in IEEE GLOBECOM, 200
Distributed Nonparametric Sequential Spectrum Sensing under Electromagnetic Interference
A nonparametric distributed sequential algorithm for quick detection of
spectral holes in a Cognitive Radio set up is proposed. Two or more local nodes
make decisions and inform the fusion centre (FC) over a reporting Multiple
Access Channel (MAC), which then makes the final decision. The local nodes use
energy detection and the FC uses mean detection in the presence of fading,
heavy-tailed electromagnetic interference (EMI) and outliers. The statistics of
the primary signal, channel gain or the EMI is not known. Different
nonparametric sequential algorithms are compared to choose appropriate
algorithms to be used at the local nodes and the FC. Modification of a recently
developed random walk test is selected for the local nodes for energy detection
as well as at the fusion centre for mean detection. It is shown via simulations
and analysis that the nonparametric distributed algorithm developed performs
well in the presence of fading, EMI and is robust to outliers. The algorithm is
iterative in nature making the computation and storage requirements minimal.Comment: 8 pages; 6 figures; Version 2 has the proofs for the theorems.
Version 3 contains a new section on approximation analysi
Capacity of Fading Gaussian Channel with an Energy Harvesting Sensor Node
Network life time maximization is becoming an important design goal in
wireless sensor networks. Energy harvesting has recently become a preferred
choice for achieving this goal as it provides near perpetual operation. We
study such a sensor node with an energy harvesting source and compare various
architectures by which the harvested energy is used. We find its Shannon
capacity when it is transmitting its observations over a fading AWGN channel
with perfect/no channel state information provided at the transmitter. We
obtain an achievable rate when there are inefficiencies in energy storage and
the capacity when energy is spent in activities other than transmission.Comment: 6 Pages, To be presented at IEEE GLOBECOM 201
Combined Integer and Floating Point Multiplication Architecture(CIFM) for FPGAs and Its Reversible Logic Implementation
In this paper, the authors propose the idea of a combined integer and
floating point multiplier(CIFM) for FPGAs. The authors propose the replacement
of existing 18x18 dedicated multipliers in FPGAs with dedicated 24x24
multipliers designed with small 4x4 bit multipliers. It is also proposed that
for every dedicated 24x24 bit multiplier block designed with 4x4 bit
multipliers, four redundant 4x4 multiplier should be provided to enforce the
feature of self repairability (to recover from the faults). In the proposed
CIFM reconfigurability at run time is also provided resulting in low power. The
major source of motivation for providing the dedicated 24x24 bit multiplier
stems from the fact that single precision floating point multiplier requires
24x24 bit integer multiplier for mantissa multiplication. A reconfigurable,
self-repairable 24x24 bit multiplier (implemented with 4x4 bit multiply
modules) will ideally suit this purpose, making FPGAs more suitable for integer
as well floating point operations. A dedicated 4x4 bit multiplier is also
proposed in this paper. Moreover, in the recent years, reversible logic has
emerged as a promising technology having its applications in low power CMOS,
quantum computing, nanotechnology, and optical computing. It is not possible to
realize quantum computing without reversible logic. Thus, this paper also paper
provides the reversible logic implementation of the proposed CIFM. The
reversible CIFM designed and proposed here will form the basis of the
completely reversible FPGAs.Comment: Published in the proceedings of the The 49th IEEE International
Midwest Symposium on Circuits and Systems (MWSCAS 2006), Puerto Rico, August
2006. Nominated for the Student Paper Award(12 papers are nominated for
Student paper Award among all submissions
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Comparison of the effects of high and low milk-replacer feeding regimens on health and growth of crossbred dairy heifers
Context: Pre-weaning growth in dairy heifers is highly dependent on the amount of milk fed. Both milk replacer (MR) and associated labour are costly, encouraging restricted milk rations and once-a-day feeding.
Aims: This study compared performance relating to the growth and health of calves receiving one of two commercial feeding regimens: High or Low.
Methods: All heifers born during the Spring (January–March) calving block on a commercial UK farm with mixed-breed genetics were recruited at birth, randomly assigned to the High (n = 104, receiving MR-A) or Low (n = 88, receiving MR-B) feed group and reared indoors on straw bedding, with free access to concentrate. Both groups initially received MR twice daily. The High group continued to receive MR twice daily throughout the experiment, whereas the Low group calves were reduced to a single MR feed daily during Weeks 4–8. Blood samples were taken in Weeks 1 and 6 to assess passive transfer and measure circulating insulin-like growth factor 1 (IGF1). The Wisconsin calf-scoring system was used to assess health of calves in Weeks 1, 2, 4, 6 and 8 and at 6 months and size was also measured at these times. Data were analysed by univariate and multivariate models.
Key results: Passive transfer was good in both groups (serum total protein (mean ± s.d.) 60.9 ± 9.1 mg/mL) with no differences in pre-weaning disease incidence; diarrhoea occurred in 64.5% and bovine respiratory disease in 26.3% of calves. High group calves were significantly heavier, taller and longer at all pre-weaning examinations except recruitment owing to more growth in the first month, and remained significantly larger at 6 months: weight 157 ± 8 vs 149 ± 7 kg, height 103 ± 5 vs 100 ± 5 cm, length 90 ± 4 vs 88 ± 5 cm. Plasma IGF1 concentrations at around Week 6 were doubled in the High group (101 ± 38.6 vs 55 ± 34.1 ng/mL). Bovine respiratory disease was associated with reduced weight gain. Heifers with diarrhoea were leaner at weaning. High feed group, weight at recruitment and good passive transfer were positively associated with weight at 6 months.
Conclusions: Higher feeding levels pre-weaning increased growth rates and IGF1, although the disease incidence was unaffected.
Implications: Previous studies have shown that more growth and higher IGF1 pre-weaning are associated with a lower age at first calving and an increased chance of reaching the end of first lactation. These in turn improve long-term performance
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