682 research outputs found
On Optimal Neighbor Discovery
Mobile devices apply neighbor discovery (ND) protocols to wirelessly initiate
a first contact within the shortest possible amount of time and with minimal
energy consumption. For this purpose, over the last decade, a vast number of ND
protocols have been proposed, which have progressively reduced the relation
between the time within which discovery is guaranteed and the energy
consumption. In spite of the simplicity of the problem statement, even after
more than 10 years of research on this specific topic, new solutions are still
proposed even today. Despite the large number of known ND protocols, given an
energy budget, what is the best achievable latency still remains unclear. This
paper addresses this question and for the first time presents safe and tight,
duty-cycle-dependent bounds on the worst-case discovery latency that no ND
protocol can beat. Surprisingly, several existing protocols are indeed optimal,
which has not been known until now. We conclude that there is no further
potential to improve the relation between latency and duty-cycle, but future ND
protocols can improve their robustness against beacon collisions.Comment: Conference of the ACM Special Interest Group on Data Communication
(ACM SIGCOMM), 201
Photonic realization of topologically protected bound states in domain-wall waveguide arrays
We present an analytical theory of topologically protected photonic states
for the two-dimensional Maxwell equations for a class of continuous periodic
dielectric structures, modulated by a domain wall. We further numerically
confirm the applicability of this theory for three-dimensional structures.Comment: 6 pages, 5 figures. To appear in the Phys. Rev.
Recommended from our members
A low-frequency chip-scale optomechanical oscillator with 58 kHz mechanical stiffening and more than 100th-order stable harmonics.
For the sensitive high-resolution force- and field-sensing applications, the large-mass microelectromechanical system (MEMS) and optomechanical cavity have been proposed to realize the sub-aN/Hz1/2 resolution levels. In view of the optomechanical cavity-based force- and field-sensors, the optomechanical coupling is the key parameter for achieving high sensitivity and resolution. Here we demonstrate a chip-scale optomechanical cavity with large mass which operates at ≈77.7 kHz fundamental mode and intrinsically exhibiting large optomechanical coupling of 44 GHz/nm or more, for both optical resonance modes. The mechanical stiffening range of ≈58 kHz and a more than 100th-order harmonics are obtained, with which the free-running frequency instability is lower than 10-6 at 100 ms integration time. Such results can be applied to further improve the sensing performance of the optomechanical inspired chip-scale sensors
- …