4,291 research outputs found
A Signal-Space Analysis of Spatial Self-Interference Isolation for Full-Duplex Wireless
The challenge to in-band full-duplex wireless communication is managing
self-interference. Many designs have employed spatial isolation mechanisms,
such as shielding or multi-antenna beamforming, to isolate the
self-interference wave from the receiver. Such spatial isolation methods are
effective, but by confining the transmit and receive signals to a subset of the
available space, the full spatial resources of the channel be under-utilized,
expending a cost that may nullify the net benefit of operating in full-duplex
mode. In this paper we leverage an antenna-theory-based channel model to
analyze the spatial degrees of freedom available to a full-duplex capable base
station, and observe that whether or not spatial isolation out-performs
time-division (i.e. half-duplex) depends heavily on the geometric distribution
of scatterers. Unless the angular spread of the objects that scatter to the
intended users is overlapped by the spread of objects that backscatter to the
base station, then spatial isolation outperforms time division, otherwise time
division may be optimal.Comment: To Appear at 2014 International Symposium on Information Theor
Spatial isolation implies zero knowledge even in a quantum world
Zero knowledge plays a central role in cryptography and complexity. The seminal work of Ben-Or et al. (STOC 1988) shows that zero knowledge can be achieved unconditionally for any language in NEXP, as long as one is willing to make a suitable physical assumption: if the provers are spatially isolated, then they can be assumed to be playing independent strategies. Quantum mechanics, however, tells us that this assumption is unrealistic, because spatially-isolated provers could share a quantum entangled state and realize a non-local correlated strategy. The MIP* model captures this setting. In this work we study the following question: does spatial isolation still suffice to unconditionally achieve zero knowledge even in the presence of quantum entanglement? We answer this question in the affirmative: we prove that every language in NEXP has a 2-prover zero knowledge interactive proof that is sound against entangled provers; that is, NEXP ⊆ ZK-MIP*. Our proof consists of constructing a zero knowledge interactive PCP with a strong algebraic structure, and then lifting it to the MIP* model. This lifting relies on a new framework that builds on recent advances in low-degree testing against entangled strategies, and clearly separates classical and quantum tools. Our main technical contribution is the development of new algebraic techniques for obtaining unconditional zero knowledge; this includes a zero knowledge variant of the celebrated sumcheck protocol, a key building block in many probabilistic proof systems. A core component of our sumcheck protocol is a new algebraic commitment scheme, whose analysis relies on algebraic complexity theory
Live-Cell Imaging of Single Receptor Composition Using Zero-Mode Waveguide Nanostructures
We exploit the optical and spatial features of subwavelength nanostructures to examine individual receptors on the plasma membrane of living cells. Receptors were sequestered in portions of the membrane projected into zero-mode waveguides. Using single-step photobleaching of green fluorescent protein incorporated into individual subunits, the resulting spatial isolation was used to measure subunit stoichiometry in α4β4 and α4β2 nicotinic acetylcholine and P2X2 ATP receptors. We also show that nicotine and cytisine have differential effects on α4β2 stoichiometry
Spatial degrees-of-freedom in large-array full-duplex: the impact of backscattering
The key challenge for in-band full-duplex wireless communication is managing self-interference. Many designs have employed spatial isolation mechanisms, such as shielding or multi-antenna beamforming, to isolate the self-interference waveform from the receiver. Because such spatial isolation methods confine the transmit and receive signals to a subset of the available space, the full spatial resources of the channel may be under-utilized, expending a cost that may nullify the net benefit of operating in full-duplex mode. In this paper, we leverage an antenna-theory-based channel model to analyze the spatial degrees of freedom available to a full-duplex capable base station. We observe that whether or not spatial isolation out-performs time-division (i.e., half-duplex) depends heavily on the geometric distribution of scatterers. Unless the angular spread of the objects that scatter to the intended users is overlapped by the spread of objects that backscatter to the base station, then spatial isolation outperforms time division, otherwise time division may be optimal
The Cost of Coexistence between Bt Maize and Open Pollinated Maize Varieties in Lowland Coastal Kenya
Kenya is currently in the process of introducing genetically modified maize (Bt maize). A major concern is that the Bt gene might cross into local varieties through cross pollination. Current regulatory strategies to ensure coexistence of the two cropping systems at the farm level rely on spatial isolation measures-separation distances and/or buffer zones. However, the interaction of practical measures and costs of spatial isolation with the farmer’s economic incentive to plant a Bt maize crop have not been studied in Kenya. The purpose of this study was to analyze the technical and economic feasibility of the implementation of spatial coexistence measures. Using spatial geo-referenced data from the actual agricultural landscape in lowland coastal Kenya, the study finds that flexible separation distances hold the possibility of ensuring coexistence in the region, but will be difficult to implement. Rigid buffer strips on the other hand are not consistent with the producers’ economic incentive to plant a Bt maize crop.Coexistence, Regulatory, Spatial, Agro-ecological zone, GM crops, Resource /Energy Economics and Policy,
Spatial Isolation Implies Zero Knowledge Even in a Quantum World
Zero knowledge plays a central role in cryptography and complexity. The
seminal work of Ben-Or et al. (STOC 1988) shows that zero knowledge can be
achieved unconditionally for any language in NEXP, as long as one is willing to
make a suitable physical assumption: if the provers are spatially isolated,
then they can be assumed to be playing independent strategies. Quantum
mechanics, however, tells us that this assumption is unrealistic, because
spatially-isolated provers could share a quantum entangled state and realize a
non-local correlated strategy. The MIP* model captures this setting. In this
work we study the following question: does spatial isolation still suffice to
unconditionally achieve zero knowledge even in the presence of quantum
entanglement? We answer this question in the affirmative: we prove that every
language in NEXP has a 2-prover zero knowledge interactive proof that is sound
against entangled provers; that is, NEXP \subseteq ZK-MIP*. Our proof consists
of constructing a zero knowledge interactive PCP with a strong algebraic
structure, and then lifting it to the MIP* model. This lifting relies on a new
framework that builds on recent advances in low-degree testing against
entangled strategies, and clearly separates classical and quantum tools. Our
main technical contribution consists of developing new algebraic techniques for
obtaining unconditional zero knowledge; this includes a zero knowledge variant
of the celebrated sumcheck protocol, a key building block in many probabilistic
proof systems. A core component of our sumcheck protocol is a new algebraic
commitment scheme, whose analysis relies on algebraic complexity theory.Comment: 55 pages. arXiv admin note: text overlap with arXiv:1704.0208
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