7,553 research outputs found
Genet: A Quickly Scalable Fat-Tree Overlay for Personal Volunteer Computing using WebRTC
WebRTC enables browsers to exchange data directly but the number of possible
concurrent connections to a single source is limited. We overcome the
limitation by organizing participants in a fat-tree overlay: when the maximum
number of connections of a tree node is reached, the new participants connect
to the node's children. Our design quickly scales when a large number of
participants join in a short amount of time, by relying on a novel scheme that
only requires local information to route connection messages: the destination
is derived from the hash value of the combined identifiers of the message's
source and of the node that is holding the message. The scheme provides
deterministic routing of a sequence of connection messages from a single source
and probabilistic balancing of newer connections among the leaves. We show that
this design puts at least 83% of nodes at the same depth as a deterministic
algorithm, can connect a thousand browser windows in 21-55 seconds in a local
network, and can be deployed for volunteer computing to tap into 320 cores in
less than 30 seconds on a local network to increase the total throughput on the
Collatz application by two orders of magnitude compared to a single core
Efficient Integer Coefficient Search for Compute-and-Forward
Integer coefficient selection is an important decoding step in the
implementation of compute-and-forward (C-F) relaying scheme. Choosing the
optimal integer coefficients in C-F has been shown to be a shortest vector
problem (SVP) which is known to be NP hard in its general form. Exhaustive
search of the integer coefficients is only feasible in complexity for small
number of users while approximation algorithms such as Lenstra-Lenstra-Lovasz
(LLL) lattice reduction algorithm only find a vector within an exponential
factor of the shortest vector. An optimal deterministic algorithm was proposed
for C-F by Sahraei and Gastpar specifically for the real valued channel case.
In this paper, we adapt their idea to the complex valued channel and propose an
efficient search algorithm to find the optimal integer coefficient vectors over
the ring of Gaussian integers and the ring of Eisenstein integers. A second
algorithm is then proposed that generalises our search algorithm to the
Integer-Forcing MIMO C-F receiver. Performance and efficiency of the proposed
algorithms are evaluated through simulations and theoretical analysis.Comment: IEEE Transactions on Wireless Communications, to appear.12 pages, 8
figure
US Army remotely piloted vehicle supporting technology program
Essential technology programs that lead to the full scale engineering development of the Aquila Remotely Piloted Vehicle system for U.S. Army are described. The Aquila system uses a small recoverable and reusable RPV to provide target acquisition, designation, and aerial reconnaissance mission support for artillery and smart munitions. Developments that will provide growth capabilities to the Aquila RPV system, as well as future RPV mission concepts being considered by the U.S. Army are presented
The 30/20 GHz communications system functional requirements
The characteristics of 30/20 GHz usage in satellite systems to be used in support of projected communication requirements of the 1990's are defined. A requirements analysis which develops projected market demand for satellite services by general and specialized carriers and an analysis of the impact of propagation and system constraints on 30/20 GHz operation are included. A set of technical performance characteristics for the 30/20 GHz systems which can serve the resulting market demand and the experimental program necessary to verify technical and operational aspects of the proposed systems is also discussed
Energy Harvesting Wireless Communications: A Review of Recent Advances
This article summarizes recent contributions in the broad area of energy
harvesting wireless communications. In particular, we provide the current state
of the art for wireless networks composed of energy harvesting nodes, starting
from the information-theoretic performance limits to transmission scheduling
policies and resource allocation, medium access and networking issues. The
emerging related area of energy transfer for self-sustaining energy harvesting
wireless networks is considered in detail covering both energy cooperation
aspects and simultaneous energy and information transfer. Various potential
models with energy harvesting nodes at different network scales are reviewed as
well as models for energy consumption at the nodes.Comment: To appear in the IEEE Journal of Selected Areas in Communications
(Special Issue: Wireless Communications Powered by Energy Harvesting and
Wireless Energy Transfer
- …