Simulating Satellite Internet Performance on a Small Island

Small remote islands often rely on satellites forInternet access, a scenario especially common in the author’s own“backyard,” the South Pacific. In most cases, a local InternetService Provider (ISP) on the island connects via a narrowbandsatellite link carrying IP traffic from and to some mainlandteleport connected to the wider Internet. The ISP then providesthis connectivity to end users via a comparatively low-latencynetwork on the island. Users on such links commonly reportproblems with downloads even when ISPs report significantspare link capacity.This paper reports on the design of a hardware-basedsimulator capable of simulating such traffic scenarios and theconsiderations underpinning its design

Can network coding bridge the digital divide in the Pacific?

Conventional TCP performance is significantly impaired under long latency and/or constrained bandwidth. While small Pacific Island states on satellite links experience this in the extreme, small populations and remoteness often rule out submarine fibre connections and their communities struggle to reap the benefits of the Internet. Network-coded TCP (TCP/NC) can increase goodput under high latency and packet loss, but has not been used to tunnel conventional TCP and UDP across satellite links before. We report on a feasibility study aimed at determining expected goodput gain across such TCP/NC tunnels into island targets on geostationary and medium earth orbit satellite links.Comment: 5 pages, 3 figures, conference (Netcod2015

RAODV: An Entropy-based Congestion Control for the AODV Routing Protocol

In networks, congestion causes packet loss and transmission delays. This paper presents a modified AODV routing protocol to detect and relieve congestion: R-AODV. We add an early congestion detection and avoidance mechanism to the route discovery process to achieve this purpose. In most previous congestion detection schemes, the affected node itself detects whether it is congested or not. The early detection and avoidance algorithm in this paper employs entropy estimation to determine the congestion status of a node’s neighbours and establish a less congested route by avoiding the congested nodes. Moreover, RAODV presents a multipath routing mechanism to support a backup route for the sender nodes. Finally, R-AODV provides a local replacement mechanism for route maintenance to improve the network performance

The effect of Hamming distances on permutation codes for multiuser communication in the power line communications channel

We partition permutation sequences into groups to form permutation codes for multiuser communication. Each group becomes a codebook for each user in a multiuser communication system. We present simulation results for the performance of different partitions of permutation codes for multiuser communication, where the codes are to be used in channels with background noise and jamming, such as the Power Line Communications (PLC) channel. With the help of the simulation results, we show that by partitioning codebooks according to distance properties we can affect the performance of the codes. The permutation codes have codewords of length M with symbols taken from an alphabet whose cardinality is M, where M is any integer. Each symbol may be seen as representing one out of the M frequencies in an M-ary Frequency Shift keying modulation scheme, for example. Each user has a codebook of cardinality greater or equal to M and there can be a maximum of M - 1 users communicating at the same time through a multiple access OR channel

T-Complexity and T-Information Theory – an

This paper describes the derivation of the T-complexity and T-information theory from the decomposition of finite strings, based on the duality of strings and variable-length T-codes. It further outlines its similarity to the string parsing algorithm by Lempel and Ziv. In its first version [15], it was intended as a summary of work published mainly by Titchener and Nicolescu. Apart from minor corrections, the present extended version incorporates feedback from previous readers and presents new results obtained since. 1 A brief introduction to T-codes This paper first gives an introduction to T-codes and their construction technique, as this is fundamental for the understanding of the T-decomposition algorithm that underpins the T-complexity measure. It also assists in its physical interpretation. T-codes [3, 4, 11] are similar to Huffman codes in that they are codes wit

A Fast T-decomposition Algorithm

T-decomposition was first proposed and implemented as an algorithm by Mark Titchener. It has applications in communication of code sets and in the fields of entropy and similarity measurement. The first implementation of a T-decomposition algorithm by Titchener was subsequently followed by a faster version named tcalc, developed in conjunction with Scott Wackrow. An improved T-decomposition algorithm was published in 2003 by the authors with the implementation tlist. This paper introduces a new algorithm that builds on our 2003 algorithm. Comparative experimental results are given to show that the new version has a significantly better time performance than previous algorithms

Theoretical Computer Science Network Event Detection with T-Entropy

This paper describes an entropy-based approach for the detection of network events. This is achieved by first converting a stream of network packets into a string and then computing its approximate average entropy rate using a computable complexity measure. Changes in the average entropy rate are interpreted as events. The computational complexity of the presented approach is nearly linear which makes this technique suitable for online scenarios. We present the results of several measurements on actual network data and show that it is indeed possible to associate actual network events with changes in entropy. Providing a reliable network service to users is important to many Internet businesses and organizations. This requires a facility for the early detection of network events such as DDoS attacks [9] so that countermeasures can be taken. Network event detection is not a simple task on machines that are not immediately involved in the event. For instance, it may be difficult for the border gateways of a network to detect an attack against a machine inside the network

A Comparison of Practical Information Measures

This report compares a variety of computable information measures for finite strings. These include Shannon’s n-block entropy, the three best known versions of the Lempel-Ziv production complexity (LZ-76, LZ-77, and LZ-78), and the lesser known T-entropy. We apply these measures to strings of known entropy, each derived from the logistic map. Pesin’s identity allows us to deduce corresponding Shannon entropies (Kolmogorov-Sinai entropies) for the sample strings, without resorting to probabilistic methods. I