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

Application-level Data Dissemination in Multi-hop Wireless Networks

Abstract-We investigate different schemes for data dissemination in multi-hop ad-hoc networks using network coding. We study the performance of these schemes in terms of the completion time when a set of data packets must be disseminated from a single source to all nodes in a multi-hop network, i.e. a network where at least one node is several hops away from the source. Therefore some network nodes must relay information to other nodes that are farther away from the source. In this setting, a relay node does not send a particular data packet, but a linear combination of the packets that it has previously received. The selection of such relays has a significant impact on performance. We present a graphical simulator based on OpenGL that allows to study performance and illustrate the status of network nodes in real time during the dissemination of an image file. Features of real-life ad-hoc networks such as packet losses and collisions are taken into consideration in our simulator. Numerical results are presented for simple linear meshed networks and for arbitrary topologies. Results indicate that schemes promoting parallel non-interfering transmissions complete the dissemination process faster

Round-robin streaming with generations

We consider three types of application layer coding for streaming over lossy links: random linear coding, systematic random linear coding, and structured coding. The file being streamed is divided into sub-blocks (generations). Code symbols are formed by combining data belonging to the same generation, and transmitted in a round-robin fashion. We compare the schemes based on delivery packet count, net throughput, and energy consumption for a range of generation sizes. We determine these performance measures both analytically and in an experimental configuration. We find our analytical predictions to match the experimental results. We show that coding at the application layer brings about a significant increase in net data throughput, and thereby reduction in energy consumption due to reduced communication time. On the other hand, on devices with constrained computing resources, heavy coding operations cause packet drops in higher layers and negatively affect the net throughput. We find from our experimental results that low-rate MDS codes are best for small generation sizes, whereas systematic random linear coding has the best net throughput and lowest energy consumption for larger generation sizes due to its low decoding complexity.Comment: NetCod'1