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NASA Ad Hoc Networking Demonstration Dave Johnson Computer Science Department Rice University 30 September 2003 Traditional Wireless Networks Many forms, but all have similar architecture: • Wireless cellular networks, wireless LANs, … Relies on a fixed infrastructure: • Centralized base station or access point • All users within wireless range of it • Needs planning, installation, management, … Wireless Cellular Dave Johnson Rice University Wireless LAN [email protected] 30 September 2003 Wireless Ad Hoc Networking May be no network infrastructure available: • Remote areas • Unplanned meetings • Emergency relief personnel quickly deployed • Military troops May not want to use the available infrastructure: • Time or cost to access and register on the service • Performance or capacity of existing service and infrastructure Dynamically extend coverage of infrastructure: • Allow users to be further away from infrastructure Dave Johnson Rice University [email protected] 30 September 2003 Ad Hoc Network Routing A B C • May be out of wireless transmitter range of others • Need to use other nodes as routers for forwarding • Find new routes after movement or change Dave Johnson Rice University [email protected] 30 September 2003 Example NASA Uses Dave Johnson Rice University [email protected] 30 September 2003 DSR Overview Dynamic Source Routing: • Divides routing problem into two parts: – Route Discovery: only try to find route when you don’t have one and need one – Route Maintenance: only while you’re actually using a route, try to keep working or fix it • All parts of protocol operate entirely on-demand • Ignores all topology changes not affecting you • Overhead scales automatically with movement • No overhead when stationary and found routes Dave Johnson Rice University [email protected] 30 September 2003 Basic DSR Route Discovery To discover a route to some address: • Broadcast ROUTE REQUEST with unique request id • When receiving a ROUTE REQUEST: – If target is yourself, return the recorded route to the initiator in a ROUTE REPLY – Else, if recently seen this id, drop the REQUEST – Otherwise, append your own address and rebroadcast the ROUTE REQUEST Dave Johnson Rice University [email protected] 30 September 2003 Basic DSR Route Maintenance After transmitting a packet to the next hop: • Listen for link-level per-hop acknowledgement, or • Listen for that node sending packet to next hop, or • Set a bit in the packet to request explicit next-hop acknowledgement When a problem with forwarding is detected: • Send a ROUTE ERROR to original sender • Sender removes the broken link from its cache Dave Johnson Rice University [email protected] 30 September 2003 Ad Hoc Network Simulation Example: Compared DSR with 3 other routing protocols: • 50 nodes moving maximum 20 m/s • Route lengths: average 3 hops, max 8 Fraction of data packets successfully delivered Dave Johnson Rice University Number of routing overhead packets sent [email protected] 30 September 2003 NASA Demo Overview A six-node ad hoc network: • Two mobile Koala robots: – FreeBSD 5.1 DSR implementation – Microsoft Windows NetMeeting video with Logitech QuickCam USB cameras • Four stationary nodes: – FreeBSD 5.1 DSR implementation – Automatically used as part of routes as needed for mobile communication • Each robot sends continuous video back to stationary endpoint node to display on screen in control room • Robots are remotely driven by user controls on this stationary endpoint node Dave Johnson Rice University [email protected] 30 September 2003 Demo Area Map Duncan Hall third floor: Dave Johnson Rice University Control Room [email protected] 30 September 2003 Demo Area Map Duncan Hall third floor: Dave Johnson Rice University Control Room [email protected] 30 September 2003 DSR Implementation Overview A new DSR implementation: • Runs almost entirely in a single user-level process • Only very small tap inserted in kernel IP input and output • DSR code is shared with ns simulator DSR source code: – DSR is the identical code used in ns simulator – Just a few #ifdef’s due to different interface to link level • Advantages of the new implementation: – Runs on up-to-date versions of FreeBSD – Designed to be very portable to other Unix-like systems (NetBSD, OpenBSD, Linux, Mac OS X), and even Windows – Only need to implement protocol once, share with simulation – Can test real system in simulation – Can validate simulation in real experiments Dave Johnson Rice University [email protected] 30 September 2003 Control Room Configuration Dave Johnson Rice University [email protected] 30 September 2003 Stationary Node Configuration Dave Johnson Rice University [email protected] 30 September 2003 Robot Configuration Dave Johnson Rice University [email protected] 30 September 2003 Robots in the Hall Dave Johnson Rice University [email protected] 30 September 2003 Active Route Display Dave Johnson Rice University [email protected] 30 September 2003 Remote Robot Driving Interface • Can control by the mouse (FORWARD, BACKWARD, LEFT, RIGHT, STOP) • Can control by cursor keys (space bar for stop) Dave Johnson Rice University [email protected] 30 September 2003 The Whole Screen Dave Johnson Rice University [email protected] 30 September 2003 Challenges: FreeBSD Video FreeBSD doesn’t support video as well as we expected: • FreeBSD supports more desktop video hardware than laptop • FreeBSD’s USB support also could be better • The routing protocol and the network can carry the video, but we had to find a way to interface the camera • Solution: Two laptops on each robot: – One running FreeBSD for the routing software – One running Windows for the video – Plugged together with a cross-over Ethernet cable • Also demonstrates DSR protocol features: – Compatible with standard IP applications (running unmodified Windows and unmodified NetMeeting) – Can route to/from nodes behind DSR “gateway” into the ad hoc network Dave Johnson Rice University [email protected] 30 September 2003 Challenges: Weight and Robots • The Koala robots can only carry limited weight: • K-Team specification says 3 kg (6.6 lbs) • Our weight problem was made worse by the video solution: – The two laptops alone weigh about 6.5 lbs • K-Team said extra weight can’t break the robots: – It monitors current draw from motor, shuts down before overload – We have had problems with this, but the robots generally tolerate the load – Could be solved better by running everything on a single laptop, or by using ultra-lightweight laptops • We also had one robot die during development: – The wheel motor doesn’t turn on its right side Dave Johnson Rice University [email protected] 30 September 2003 Thanks! My students: • Santashil PalChaudhuri • Amit Saha • Shu Du • Khoa To • Jorjeta Jetcheva • Yih-Chun Hu (now graduated) Rice CS administrative support: • Darnell Price • Rhonda Guajardo Funding: • NASA, NSF, Schlumberger Dave Johnson Rice University [email protected] 30 September 2003