4,019 research outputs found
Fuzzy Logic Control of Adaptive ARQ for Video Distribution over a Bluetooth Wireless Link
Bluetooth's default automatic repeat request (ARQ) scheme is not suited to video distribution resulting in missed display and decoded deadlines. Adaptive ARQ with active discard of expired packets from the send buffer is an alternative approach. However, even with the addition of cross-layer adaptation to picture-type packet importance, ARQ is not ideal in conditions of a deteriorating RF channel. The paper presents fuzzy logic control of ARQ, based on send buffer fullness and the head-of-line packet's deadline. The advantage of the fuzzy logic approach, which also scales its output according to picture type importance, is that the impact of delay can be directly introduced to the model, causing retransmissions to be reduced compared to all other schemes. The scheme considers both the delay constraints of the video stream and at the same time avoids send buffer overflow. Tests explore a variety of Bluetooth send buffer sizes and channel conditions. For adverse channel conditions and buffer size, the tests show an improvement of at least 4 dB in video quality compared to nonfuzzy schemes. The scheme can be applied to any codec with I-, P-, and (possibly) B-slices by inspection of packet headers without the need for encoder intervention.</jats:p
Power-Constrained Fuzzy Logic Control of Video Streaming over a Wireless Interconnect
Wireless communication of video, with Bluetooth as an example, represents a compromise between channel conditions, display and decode deadlines, and energy constraints. This paper proposes fuzzy logic control (FLC) of automatic repeat request (ARQ) as a way of reconciling these factors, with a 40% saving in power in the worst channel conditions from economizing on transmissions when channel errors occur. Whatever the channel conditions are, FLC is shown to outperform the default Bluetooth scheme and an alternative Bluetooth-adaptive ARQ scheme in terms of reduced packet loss and delay, as well as improved video quality
A model of gravitation with global U(1)-symmetry
It is shown that an embedding of the general relativity space into a flat
space gives a model of gravitation with the global symmetry and the
discrete one. The last one may be transformed into the symmetry
of the unified model, and the demand of independence of and
transformations leads to the estimate where
is an analog of the Weinberg angle of the standard model.Comment: 7 page
The energy scale behind the metallic behaviors in low-density Si-MOSFETs
We show that the unexpected metallic behavior (the so-called two-dimensional
metal-insulator transition) observed in low-density Silicon
metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) is controlled
by a unique characteristic energy scale, the polarization energy. On one hand,
we perform Quantum Monte Carlo calculations of the energy needed to polarize
the two dimensional electron gas at zero temperature, taking into account
Coulomb interactions, valley degeneracy and electronic mobility (disorder). On
the other hand, we identify the characteristic energy scale controlling the
physics in eight different sets of experiments. We find that our {\it
ab-initio} polarization energies (obtained without any adjustable parameters)
are in perfect agreement with the observed characteristic energies for all
available data, both for the magnetic field and temperature dependence of the
resistivities. Our results put strong constraints on possible mechanisms
responsible for the metallic behavior. In particular, there are strong
indications that the system would eventually become insulating at low enough
temperature.Comment: two references added, corrected typos, minor changes, final version
as publishe
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