Brenton Walker

Leibniz Universität Hannover · Institut für Kommunikationstechnik

Models of parallel processing systems typically assume that one has $l$ workers and jobs are split into an equal number of $k=l$ tasks. Splitting jobs into $k \gt l$ smaller tasks, i.e. using “tiny tasks”, can yield performance and stability improvements because it reduces the variance in the amount of work assigned to each worker, but as $k...

Models of parallel processing systems typically assume that one has $l$ workers and jobs are split into an equal number of $k=l$ tasks. Splitting jobs into $k > l$ smaller tasks, i.e. using ``tiny tasks'', can yield performance and stability improvements because it reduces the variance in the amount of work assigned to each worker, but as $k$ incre...

Several network transport protocols have been developed to provide reliable connection-oriented multipath concurrent data transmission. One of their advantages is reducing end-to-end latency by redundantly transmitting data through multiple network paths. In this paper, we address the problem of redundant packet scheduling in MPTCP over networks wi...

Multi-Path TCP (MPTCP) is a protocol that allows many TCP connections, or flows, to be pooled together and to behave as a single flow from the perspective of the higher network layers. In situations with heterogeneous links, such as networks that combine high-latency infrastructure-based links and direct node-to-node wireless links, the low-latency...

Multi-server systems have received increasing attention with important implementations such as Google MapReduce, Hadoop, and Spark. Common to these systems are a fork operation, where jobs are first divided into tasks that are processed in parallel, and a later join operation, where completed tasks wait until the results of all tasks of a job can b...

Multi-server systems have received increasing attention with important implementations such as Google MapReduce, Hadoop, and Spark. Common to these systems are a fork operation, where jobs are first divided into tasks that are processed in parallel, and a later join operation, where completed tasks wait until the results of all tasks of a job can b...

We conduct large-scale cellular trace-driven experiments comparing different opportunistic network coded data dissemination strategies and different cache seeding strategies for distributing a large data object across a country scale network of thousands of local repositories. We compare fragmentation, source-only erasure coding, cache coding, netw...

A cellular association trace consists of timestamped events recording user activity in labeled cells in a cellular network. From such data one can infer that if a user appears in two different cells within a short span of time, that a handover took place, and that the coverage areas of the two cells overlap. That is, one can infer geographic inform...

Laboratory-based multi-node wireless testbeds are essential to building and experimenting with mobile wireless networks such as MANETs, DTNs, or custom radios and protocols. Several systems based on many-to-many channel emulators have been built, however these systems rely on either a simple deterministic channel model such as free-space path loss,...

Laboratory-based wireless testbeds are essential for performing repeatable experiments with experimental protocols and devices. Several many-to-many wireless emulators have been proposed and built, but existing systems still rely on simplified channel models, such as free-space path loss, or general stochastic fading models. We have begun using sit...

In a challenged network environment, where end-to-end connectivity may be a rare occurrence, delay-tolerant routing protocols must strike a balance between the increased robustness and reliability that comes with message replication and the resulting high bandwidth and storage overhead. Network coded routing, in which a node combines messages from...

In a challenged network environment, where end-to-end connectivity may be a rare occurrence, delay-tolerant routing protocols must strike a balance between the increased robustness and reliability that comes with message replication and the resulting high bandwidth and storage overhead. Network coded routing, in which a node combines messages from...

As delay-tolerant networking (DTN) finds applications in a wider variety of environments, DTN implementations have been ported to a variety of devices. Performance testing of DTN implementations has typically been carried out on powerful hardware, but there have been few performance evaluations on resource-constrained devices. We present the result...

In delay-tolerant networks, end-to-end routes are rarely available, and routing protocols must take advantage of the opportunistic interactions among nodes to deliver packets. Probabilistic routing performs well in such networks and has been the dominant focus of research in this area. However, creating efficient routing protocols is challenging be...

Biologists have observed that when a small colony breaks off from a larger population, the colony tends to have less genetic diversity. This phenomenon, called the "founder effect", has an analogy in delay-tolerant networks that employ network coded routing to disseminate large bundles of data. In this paper, we study the spread of information dive...

Laboratory-based mobile wireless testbeds such as MeshTest and the CMU Wireless Emulator are powerful platforms that allow users to perform controlled, repeatable, mobile wireless experiments in the lab. Unfortunately such systems can only accommodate 10-15 nodes in an experiment. We have designed and built a scalable wireless testbed that uses sof...

In this article we present the Mobility Data Contest. We discuss the motivation behind this competition and we present its goals. After explaining the rules of the contest, we focus on the evaluation criteria used for assessing the submitted work. Finally, we give three simple examples of experiments that would be eligible for the contest.

MeshTest is a laboratory-based mobile wireless testbed. The system offers more realism than simulation or network-level emulation because it uses real implementation running on real devices, communicating using real wireless hardware over an emulated RF environment. However it also pro-vides repeatability, control, and convenience not possible in f...

Over the last ten years interest in the field of delay and disruption-tolerant, challenged, and opportunistic networks has grown dramatically. Communication protocols originally designed to accommodate communication in the intermittent and high-delay environment of deep space have been applied to sensor networks, battlefield networks, and more rece...

In this talk, I will discuss a promising solution to the "last mile" problem of providing Internet connectivity in underserved rural areas of developing countries. The solution leverages existing road and vehicle infrastructure to create a digital wireless ...

The MeshTest wireless testbed allows users to conduct repeatable mobile experiments with real radio hardware under controlled conditions. The testbed uses shielded enclosures and a matrix switch of programmable attenuators to produce multi-hop scenarios and simulate the effects of mobility and fading. Previous work focused on the theory and perform...

Laboratory-based mobile wireless testbeds such as MeshTest and the CMU Wireless Emulator are powerful platforms that allow users to perform controlled, repeatable, mobile wireless experiments in the lab. Unfortunately such systems can only accommodate 10-20 nodes in an experiment. We have designed and built a prototype of a system that uses softwar...

MeshTest is a laboratory-based wireless testbed that can subject real wireless devices to reproducible mobile scenarios. It uses shielded enclosures and an RF matrix switch to dynamically control the attenuation experienced between pairs of nodes. The testbed can be controlled remotely, and is an ideal platform for development of and experimentatio...

MeshTest is a laboratory-based multi-hop wireless testbed that can subject real wireless nodes to reproducible mobile scenarios. It uses shielded enclosures and an RF matrix switch to dynamically control the attenuation experienced between pairs of nodes. The testbed is an ideal platform for experimenting with MANET and DTN implementations, offerin...

The MeshTest wireless testbed allows users to conduct repeatable mobile experiments with real radio hardware under controlled conditions. The testbed uses shielded enclosures and a matrix switch of programmable attenuators to produce multi-hop scenarios and simulate the effects of mobility and fading. Previous work focused on the theory and perform...

Mobile wireless delay-tolerant networks (DTNs) are wireless networks that suffer from intermittent connectivity, but enjoy the benefit of mobile nodes that can store, carry, and forward packets or messages, bringing them closer to their destinations through a selective forwarding policy. The evaluation of DTN routing protocols has primarily relied...

MeshTest is a laboratory-based multi-hop wireless testbed that can subject real wireless nodes running real DTN imple- mentations to reproducible mobile scenarios. It uses shielded enclosures and an RF matrix switch to dynamically control the attenuation experienced between pairs of nodes. The testbed is an ideal platform for DTN testing, oering co...

Delay Tolerant Networks (DTNs) are a class of networks in which a contemporaneous end-to-end path from source to destination generally does not exist. Such networks use on a store-carry-forward communication model which relies on the mobility of nodes to transfer data between geographi- cally separated nodes. DTN researchers have relied heavily on...

In order to better understand human and animal mobility and its potential eects on Mobile Ad-Hoc networks and Delay-Tolerant Networks, many researchers have conducted experiments which collect encounter data. Most analyses of these data have focused on isolated statistical properties such as the distribution of node inter-encounter times and the de...

The MeshTest testbed is designed to subject wireless de- vices and protocols to realistic and repeatable mobile scenar- ios, including multi-hop and disconnected topologies. The testbed makes it possible to ecien tly test real implementa- tions of ad-hoc and delay-tolerant routing protocols. With the completion of its mobility control software, the...

Mobile Wireless Delay-Tolerant Networks (DTNs) are wire- less networks that suer from intermittent connectivity, but enjoy the benet of mobile nodes that can store and forward packets or messages, and can act as relays, bringing packets and messages closer to their destination through a selective forwarding policy. Many DTN protocols compensate for...

Mobile, ad-hoc, wireless networks offer an interesting paradigm for ubiquitous connectivity. They have many proposed applications, and with every application comes new protocols. To test such protocols, one has two basic options: simulators and testbeds. We describe a novel wireless networks testbed called MeshTest, supporting mobile, ad-hoc, and m...