Robert Olsson

On powering communication networks in developing regions

The work behind this paper aims at demonstrating innovative solutions for the establishment of sustainable community broadband networks in areas where there is demand but no supply of broadband services. One of the major challenges turns out to be reliable power supply. To overcome this challenge, we explore how to decrease the demand for power as well as the feasibility of using alternative power sources, such as solar and wind, and alternative power storage technologies, such as batteries and ultra-capacitors. In this paper, we present data collected over 2 months from the Serengeti community network in rural Tanzania to discuss the quality of the existing power-grid and the feasibility of using solar and wind energy as alternative energy sources. The network backbone is based on 1Gbps Ethernet links over dark fibre while end-user connections are currently based on WiFi links. Our measurements regarding the quality of the power-grid show up to 21 power-outages in one single day, with an average of 2 outages per day. Some of the outages are due to planned rationing schemes caused by insufficient power generation while some outages are due to poor wiring or installations. Our measurements and analysis of the feasibility of using alternative power sources indicate wind speeds on the average 2m/s and a persistent high-level insolation, making solar energy the prime candidate as an alternative source of electricity. The relatively high cost of solar panels has to be mitigated by increased energy efficiency of the network elements. We also propose power management to be included in the network management system to maximize the availability of the network services and decrease operational costs due to damaged network elements.

Pktgen : Measuring performance on high speed networks

Abstract Pktgen is a tool for high-speed packet generation and testing. It runs in the Linux kernel, and is designed to accommodate a wide range of network performance tests. Pktgen consists of a p ...

On the design of inclusive ubiquitous access

The development towards ubiquitous network access requires innovative solutions to get remote areas included, especially rural areas of developing regions. The challenges include robustness of network components, poor or non-existent power supply and sustainable business models. We argue that large scale user-driven community networks are becoming technically viable to deploy in areas that are short of supply of telecommunication services due to little or no commercial interest. To support this claim, we discuss the design of key network elements and careful power management based on alternative energy sources and storage. We also provide a status report from ongoing field-tests regarding provisioning of broadband network services in Serengeti, Tanzania, and outline briefly our strategy to achieve sustainability. On the technical side, we first discuss an affordable, high-performance, low-effect router based on open source software and standard off-the-shelf hardware offering both copper and fibre links. Our design is capable of forwarding more than 700kpps at 22.3W. The power consumption is considerably less than all alternatives in our comparison. Then we discuss power management and the use of batteries and super-capacitors as backup and storage solutions.

On the design of affordable and green high-performance routers for community networks: short paper

We argue that large scale user-driven community networks are becoming viable in areas without access to telecommunication services due to lack of commercial interest. We discuss the design of a key component supporting this claim: a high-performance, low-power-consuming and affordable router with fibre optic capable of forwarding 2 Gbps, 220kpps, powered by only 25W, which is between 7% and 17% of the alternatives in our comparison. The cost of the one-off prototype was below a third of the prices of comparable proprietary solutions and half of other open source alternatives. It can be reduced further in series production. Future work will include widening of bottlenecks without increasing cost and field tests in rural African settings.

Inclusive Ubiquitous Access - A Status Report

The development towards ubiquitous network access requires innovative solutions to get remote areas included, especially rural areas of developing regions. We report on recent progress in the Serengeti Broadband Network, one of the first pilots established in the Tanzania ICT for Rural Development programme with the mission to design and validate a method to establish sustainable broadband markets in under-served areas. The challenges include ownership and leadership, sustainable business models, robustness of network components and poor or non-existent supply chains, including power supply.

Powering devices using ultra-capacitor batteries

We explore the use of ultra-capacitors as backup storage for solar powered electronic devices. We discuss two use cases: routers in off-grid broadband networks consuming a few Watt and wireless sensor network nodes using a few mW when operating and a few μW in quiescent mode. We have been testing batteries with ultra-capacitor based cells, both EDLC and LIC, in the range from 40 to 3000F. We found them viable alternatives in some applications and started long term field tests to sort out some unclear aspects regarding maximum discharge levels. Besides the traditional function of a backup battery storage in low-power applications, the very low internal resistance of capacitors make them useful also in hybrid solutions to accommodate transient needs for high currents that traditional batteries cannot deliver. Due to the low resistance, charging/discharging can be very fast. We also show how a very simple design requiring only one LIC capacitor can power a WSN mote sending at 1 packet/minute for 6 weeks on a single charge.

Design and implementation of an IoT-controlled DC-DC converter

In line with the shift towards renewable energy, small-scale solar panels have become commonly available. Solar panels are intermittent energy sources producing direct current, and DC-DC converters are needed to convert between different voltage levels, both for different power loads and for storing energy. DC-DC converters typically have a very limited functionality and are statically configured for specific voltage levels. In this paper, we propose a new generation of flexible DC-DC converters with software and communication support (through Contiki and CoAP) for remote power monitoring and control. We present a prototype design and implementation of a DC-DC converter including a microprocessor, a lean operating system, and networking support. With such a DC-DC converter, controlled over the Internet, we can address various types of power and energy related issues and advance the state-of-the-art of green networked applications.

IoT-Grid: IoT Communication for Smart DC Grids

IoT technology is considered an essential imperative for Smart Grids (SGs). However, IoT devices have inherently limited responsiveness that may not be sufficient for a time critical SG with stringent demands on communication delay. In practice, it remains an outstanding problem to combine IoT technology with existing grids. To facilitate deployment of IoT-based grids in domestic environments, we propose IoT-grid, a programmable, small-scale, direct current (DC) grid, that can be easily implemented with low-power hardware with limited processing capacity. The proposed grid adopts relatively cheap DC-DC converters which not only provide high conversion efficiency but also accommodate existing small-scale DC power systems (e.g. solar panels). We then explore the communication aspects of IoT-grid, namely, control and monitoring functions. We observe that processing delays of IoT devices have large impact on IoT-grid, which cause a chain of control commands to take considerable longer time as the number of commands increases. To mitigate this problem, we propose a mechanism based on sending burst commands with scheduled responses. Our experimental results show that, in the presence of processing delays, this method can significantly reduce the overall response time.