Romana Challans

The serval mesh: A platform for resilient communications in disaster & crisis

The challenges of many crisis communication needs can be summarised as: the need to allow civilians to safely communicate with one another, and with the outside world, without reliance on any domestic terrestrial infrastructure, or on the import of physical materials. Therefore, any solution should place high precedence on infrastructure-independent operation, and the re-use of existing hardware technology. Expanding on this concept, we present a prototype solution, the Serval Mesh, and briefly discuss the design decisions that were made, and summarise the trial and pilots conducted to date. Together, these show that the Serval Mesh is well placed to provide secure, resilient mobile communications services in a variety of situations, and in conjunction with the air-droppable UHF-packet-radio enabled Serval Mesh Extender concept, to provide such services over longer distances than is possible for Wi-Fi based mobile mesh networks. Thus we argue by example that it is possible to enable effective use of mobile phones during periods of infrastructure-deprivation.

THE RATIONAL BEHIND THE SERVAL NETWORK LAYER FOR RESILIENT COMMUNICATIONS

The Internet Protocol is the dominant network protocol used in public networks today and has proven to be highly effective for wired networks and wireless networks alike, provided network address allocation can be coordinated. Mesh networks consisting of highly mobile devices present new challenges, especially when the assumption of coordination does not apply. One situation where coordination is not readily possible is ad-hoc networks in isolated areas and in disaster zones, both of which are characterized by deprivation of infrastructure. This study describes our realizations of several problems that IPv4 and IPv6 networking faces in such contexts and provides a brief description of an alternative network architecture for such situations, the Serval Network Layer and provides some of the reasoning behind the design decisions made. The Serval Network Layer is implemented as an open-source user-space network layer with strong intrinsic security characteristics and is able to be deployed without any centralized coordination.

Succinct data: Extreme compression for ODK forms making digital field assessment practical during disasters by minimizing data transmission size and costs

Field communications play a vital role in disaster relief and other humanitarian responses. However, the acute phase of these events is frequently characterized by scarcity of communications capacity, confounding the efforts of responders to develop the situational awareness that would enable them to maximize the effectiveness of their activities. Access to high-bandwidth global connectivity is often limited to a few sites where existing infrastructure is still functional, or where temporary access has been rapidly deployed. The need to gather data, e.g., standardized field assessment reports, is not limited to these locations. A related problem is that any available communications links are likely to be overloaded. Therefore it is desirable to create a system that can make use of hand-held and low-cost global communications options. One such family of devices is those that provide access to the Iridium constellations Short Burst Data capability, effectively providing a satellite based SMS service. However making use of such devices is problematic because of the extremely limited bandwidth they offer, and high cost-per-byte. New Zealand Red Cross and the Serval Project [1 - 6] at Flinders University have responded to this need by creating the Succinct Data concept, wherein the salient information from a field report is automatically extracted, compressed and transmitted via any available means, with the full report following when the collection device, or another collection device it comes into contact with, eventually reaches a high-bandwidth communications link. In this way rich field assessment reports can be collected, with the highest priority information transmitted immediately, such as numbers of persons requiring assistance and basic assessment of dwellings, and with the additional rich information following when possible, such as detailed commentary, images and other media where appropriate. In this paper we describe the work to date on implementing Succinct Data, and the creation of a new compression scheme that can compress ODK form instances to less than 1/12th of their size - less than half the size achievable using gzip.