27 research outputs found
Optimising node selection probabilities in multi-hop M/D/1 queuing networks to reduce latency of Tor
In this paper the expected cell latency for multi-hop M/D/1 queuing
networks, where users choose nodes randomly according to some
distribution, is derived. It is shown that the resulting optimisation surface
is convex, and thus gradient based methods can be used to find the optimal
node assignment probabilities. This is applied to a typical snapshot of the
Tor anonymity network at 50%usage, and leads to a reduction in expected
cell latency from 11.7 ms using the original method of assigning node
selection probabilities to 1.3 ms. It is also shown that even if the usage is
not known exactly, the proposed method still leads to an improvement.This is the accepted manuscript version. The final version is available from IET at http://digital-library.theiet.org/content/journals/10.1049/el.2014.2136
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Particle filtering for joint symbol and code delay estimation in DS spread spectrum systems in multipath environment
We develop a new receiver for joint symbol, channel characteristics, and code delay estimation for DS spread spectrum systems under conditions of multipath fading. The approach is based on particle filtering techniques and combines sequential importance sampling, a selection scheme, and a variance reduction technique. Several algorithms involving both deterministic and randomized schemes are considered and an extensive simulation study is carried out in order to demonstrate the performance of the proposed methods.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Optimising node selection probabilities in multi-hop M/D/1 queuing networks to reduce latency of Tor
The expected cell latency for multi-hop M/D/1 queuing networks, where users choose nodes randomly according to some distribution, is derived. It is shown that the resulting optimisation surface is convex, and thus gradient-based methods can be used to find the optimal node assignment probabilities. This is applied to a typical snapshot of the Tor anonymity network at 50% usage, and leads to a reduction in expected cell latency from 11.7 ms using the original method of assigning node selection probabilities to 1.3 ms. It is also shown that even if the usage is not known exactly, the proposed method still leads to an improvement