AdHocDroid: mobile connectivity without infrastructure
Wed 15 Feb 2017
Researchers in Portugal have developed an IP-based mesh network that uses rooted Android phones to allow connectivity even where there is no provider-based signal.
Mobile AdHoc NETworks (MANETs) that attempt to create device-based webs from which information can hop through participating users are not a new field of pursuit – the U.S. military is developing systems which can attempt to transmit field data even through the least likely pieces of equipment; a Chinese network service provider in Hong Kong has experimented with similar concepts in order to let signal-blocked building dwellers reach a better throughput; and CCTV cameras have come under criticism of security exploits that are made possible by their own use of the mesh.
But in the field of mobile-based mesh networks, the MANET has more urgent promise as a possible solution to communications in disaster situations, as well as potentially helping to span connectivity-starved and sparsely populated areas.
But the new solution, dubbed AdHocDroid, from researchers at two Portuguese universities provides a framework which, uncommonly amongst similar efforts, supports standard TCP/IP applications and generates a genuine IEEE 802.11 MANET, initially using Android-based smartphones which have been rooted.
Similar applications which have exploited WiFi Direct or a commingling of IEEE 802.1 and Bluetooth – such as the Serval Project – need overlay routing and dedicated applications which are able to take advantage of the resulting proprietary protocols.
The researchers used the Gigabyte Gsmart G1305 running Android 2.3 with CyanogenMod 7, and the Samsung Nexus S running Android 4.3 and CyanogenMod 10.2.1. Additionally they enabled AdHocDroid on the Samsung Galaxy Tab 10.1 tablet running Android 3.2.
AdHocDroid first systematically disables network connectivity using the Android API, in order to stop individual applications attempting to re-enable or reconfigure network settings on the phone. The application then rewrites the text file which stores all known network configuration in order to make the MANET the default connectivity path.
The researchers claim that AdHocDroid is the only MANET to date which satisfies the full definition of the term: WiFi Direct cannot perform multi-hop, in addition to requiring a dedicated framework; Open Garden shares this latter flaw, in addition to requiring a wireless network at one point in the mesh; while Serval again needs dedicated systems. However, WiFi Direct is currently the only MANET which has support for other systems, such as the PC platform – functionality that’s partly enabled on AdHocDroid and completely absent from Open Garden and Serval.
To test their system the researchers undertook a series of experiments using standard multiplayer game apps from the Android Store, using the Nexus S for these. The game 2048 Battle worked well out of the box on the new network, but Spaceteam initially failed to get multi-hop working, since the game by default uses multicast DNS to locate the opponent – traffic which is not forwarded by the router. However after discovery the game worked well, and could even switch comfortably between single-hop and multi-hop.
Measuring throughput on AdHocDroid, the team found contention to be comparable to a standard network connection using multi-hop, but doubly speedy on single hop, due to the absence of an intermediate node.
Power consumption was broadly equivalent to standard network usage, except in certain configurations of the mesh protocol.