Ad-hoc Ad-hoc networking networking with with low-cost low-cost devices: devices: how how to to do do itit right right Pawel Gburzynski & Wlodek Olesinski Olsonet Communications 1 What is wrong? Industry Industry has has been been making making aa lot lot of of noise noise (and (and we we are arealready alreadyblessed blessedwith withZigBee®) ZigBee®) Lots Lots of of academic academic work: work: “problems” “problems” identified, identified, “solutions” “solutions”abound abound So Sowhere whereare arethose thosemesh meshnetworks? networks?Have Haveyou youseen seen one onelately? lately? 2 What is the goal? application application protocols protocols OS OS hardware hardware 3 What is the goal? application application protocols protocols This is what appears to be exciting research-wise OS OS hardware hardware 4 What is the goal? application application protocols protocols OS OS hardware hardware This is what you have to build, if you are serious 5 What is the goal? application application protocols protocols OS OS This has the largest and direct impact on unit cost and feasibility hardware hardware 6 What is the goal? application application protocols protocols OS OS This determines how much you can do (and how easily) hardware hardware 7 What is the goal? application application protocols protocols OS OS But again, this is what you have to build: the WHOLE thing hardware hardware Here Here we we have have it: it: the the notorious notorious (although (although not not often often realized) realized) layering layering problem problem inin the the standard standard approach approachto tosolutions: solutions: 8 What is wrong with academic research: Most Mostresearch researchignores ignoresmundane mundaneaspects, aspects,like: like: device devicefootprint footprintand andend endcost cost realistic realisticproperties propertiesof ofwireless wirelesschannels channels ease easeof ofapplication applicationdevelopment development portability portability maintenance maintenance 9 What is wrong with the industry: standards standardsand andlayers layersstructured structuredby byconsortia, consortia, i.e., i.e.,the thelarger largerthe thebetter better trying trying to to solve solve general general problems problems with with conflicting conflicting specs: specs: you you cannot cannot produce produce anything anythingtruly trulysimple simpleand andsmall smallthis thisway way no no early early view view of of the the actual actual software: software: itit will will be beoutsourced; outsourced;design designand andimplementation implementationare are two twocompletely completelydifferent differentthings things the the application application isis just just aa layer layer on on top top of of aa large largemess messof ofvarious various“stacks” “stacks” 10 Our holistic ideas Simple Simple isis beautiful, beautiful, e.g., e.g., the the word word “stack” “stack” has has been been removed removedfrom fromour ourdictionary dictionary AA flexible flexible plug-in plug-in model: model: tools tools facilitating facilitating structured structured interplay interplay of of modules modules without without restricting restrictingtheir theirreach reach Ease Easeof ofaccommodating accommodatingnew newdevices devices AAsimple, simple,auto-scalable, auto-scalable,stage-less stage-lessrouting routingscheme scheme Authoritative Authoritative product product development development and and testing testing without truly without hardware hardware deployment! deployment! truly rapid rapid development! development! 11 The principle of collaboration Nodes Nodescome comeand andgo, go,nothing nothingisisever everguaranteed. guaranteed. The Themore morenodes nodesare are involved involved ininsome someaction, action, the the more more likely likelythat thatsome someof ofthem themwill willfail failto tokeep keeptheir theirend endup. up. Do Do not not use use contrived contrived schemes, schemes, i.e., i.e., ones ones that that break break irreparably irreparablywhen whenone oneof ofthe thecollaborating collaboratingnodes nodesfails. fails. AA node node should should idempotently idempotently push push the the system system towards towards the the goal. goal. It It should should never never be be aa critical critical member member of of the the team, team,unless unlessthe theteam teamisissmall smalland andthe theaction actionisisshort. short. 12 The principle of participation Your Yourresources resourcesare arelimited. limited. You You should should be be able able to to tailor tailor the the extent extent of of your your participation participationinincollaborative collaborativetasks tasksto toyour yourresources. resources. The The collaborative collaborative schemes schemes should should be be scalable scalable to to the the amount amountof ofresources resourcesof ofthe theteam teammembers. members. Say, Say, aa node node with with small small memory memory should should be be able able to to contribute, contribute, too, too, albeit albeit at at proportionately proportionately reduced reduced quality qualitycompared comparedto toaaresourceful resourcefulnode. node. 13 These principles are mostly violated E.g., E.g., popular popular ad-hoc ad-hoc routing routing protocols protocols operate operate inin two two phases phaseswhereby: whereby: paths pathsare areidentified, identified,maintained, maintained,recovered recovered actual actualhop-by hop-byhop hopforwarding forwardingtakes takesplace place Don't Don't be be fooled! fooled! Even Even ifif the the two two phases phases are are interleaved interleaved and and not not blatantly blatantly visible, visible, they they are are still still there. there. Those Thosepaths pathsemulate emulatewires wires(in (inaapathetic patheticsort sortof ofway). way). The The collaboration collaboration isis contrived: contrived: every every node node along along aa path pathisisaacritical criticalmember memberof ofaapotentially potentiallylarge largeteam. team. 14 Mesh networking P->P P->P ? This is how everybody (including Zigbee®) does it Where Where should should II send send the the packet packet on on its its way way to tothe thedestination? destination? 15 Mesh networking: TARP P->P P->P ? TARP TARP ? ? ? ? Where Where should should II send send Should Should II rebroadcast rebroadcast the the the the packet packet on on its its way way received received packet? packet? Will Will II help help to when tothe thedestination? destination? whenIIdo dothat? that? 16 Flooding controlled by a chain of rules am amIIthe the recipient? recipient? YES NO too many hops? rule rule11 fail rule rule22 seen already? receive receiveand and forget forget Suboptimal Path Discard drop drop fail rule rulenn drop fail rebroadcast rebroadcast 17 Path convergence D S 18 Path convergence D S 19 Path convergence D D S S 20 Don't let them fool you! This This isis not not fundamentally fundamentally worse worse than than point-to-point point-to-point forwarding! forwarding! Flooding Flooding may may have have negative negative connotations, connotations, so socall callititsomething somethingelse, else,e.g., e.g.,re-casting. re-casting. All Allthose those“sophisticated” “sophisticated”point-to-point point-to-pointschemes schemesmust must at atleast leaststart startthis thisway, way,i.e., i.e.,from fromflooding. flooding. Everything Everything isis broadcast broadcast inin wireless: wireless: there there isis no no such such thing thingas aspoint-to-point; point-to-point;they theycan canonly onlypretend. pretend. In In TARP TARP the the “paths” “paths” can can converge converge to to essentially essentially the the same same narrow narrow stripe stripe of of nodes nodes as as inin AODV, AODV, DSR, DSR, ...... ifif you youREALLY REALLYwant wantthem themto. to.You Youdon't! don't! 21 Advantages No No need need for for data-link data-link encapsulation: encapsulation: packets packets are are forwarded forwardedinintheir their“original” “original”shape. shape. Rules Rulesare arecache-driven cache-drivenand andfailsafe: failsafe:ififthe thecache cacheisis too too short, short, the the packet packet will will not not be be dropped dropped on on the the rule's rule'sbehalf. behalf. This This makes makes the the rules rules scalable scalable to to resources: resources: preserving preservingthe theprinciple principleof ofparticipation. participation. Tuneability: Tuneability:easy easyto totrade tradebandwidth bandwidthfor forreliability reliability (PDF) (PDF)ininthe theface faceof ofmobility. mobility. Single Single phase, phase, automatic automatic redundancy, redundancy, no no critical critical nodes: nodes:follows followsthe theprinciple principleof ofcollaboration. collaboration. 22 Node software layout praxis (application) other plugins TARP API plugs VNETI phy PicOS kernel driver driver microcontroller UART ... GPIO, ADC, DAC RF module other network devices 23 2 VUE : the same thing run virtually praxis (application) other plugins TARP API plugs VNETI Channel model phy Virtual network VUEE = Virtual Underlay Emulation Engine Virtual I/O pins Virtual UART Interface daemon Other virtual hardware Virtual RF module Remote agents 24 SMURPH -> PicOS -> VUE 2 SMURPH SMURPH== ==simulation simulationand andspecification specificationsystem system SIDE SIDE== ==SMURPH SMURPH++interface interfaceto toreal-life real-life reactive reactiveenvironment environment PicOS PicOS== ==SMURPH SMURPHlingo lingoused usedas asthe thethread thread paradigm paradigmininour ourmicroscopic microscopicOS OS 2 VUE VUE2== ==macros macrosand andfunctions functionsturning turningaaPicOS PicOS application application(praxis) (praxis)into intoaaSMURPH SMURPHmodel model 25 A PicOS thread fsm hrate { state HR_INIT: delay (3 * 1024, HR_SEND); Release; state HR_SEND: if ((HeartRate = hrc_get ()) > 255) HeartRate = 255; if (XWS == 0) { // Don't do this if a sample is being sent address packet = tcv_wnp (HR_SEND, BSFD, 2); put1 (packet, PT_HRATE); put1 (packet, HeartRate); tcv_endp (packet); } proceed HR_INIT; } 26 A PicOS thread fsm hrate { INIT INIT state HR_INIT: delay (3 * 1024, HR_SEND); Release; 33sec sec SEND SEND calculate calculate HR HR state HR_SEND: if ((HeartRate = hrc_get ()) > 255) HeartRate = 255; yes if (XWS == 0) { XWS? // Don't do this if a sample is being sentXWS? address packet = tcv_wnp (HR_SEND, BSFD, 2); no put1 (packet, PT_HRATE); get xmt put1 (packet, HeartRate); tcv_endp (packet); buffer } proceed HR_INIT; send send HR HR } 27 What does it buy us? x code code shared, shared,ROM ROM(flash) (flash) data data needed neededanyway anyway(small, (small, mostly mostlyglobal) global) stack stack unacceptable unacceptable 28 What does it buy us? x 1 code code shared, shared,ROM ROM(flash) (flash) data data needed neededanyway anyway(small, (small, mostly mostlyglobal) global) stack stack unacceptable unacceptable Multiple Multiple threads threads (FSM's) (FSM's) operating operating as as coroutines coroutines with with implicit implicit control control transfer transfer and and multiple multipleentry entrypoints. points.They Theyall allexecute executeon onthe the same same single single stack stack within within aa trivial trivial prerequisite prerequisite amount amountof ofRAM RAM(like (like20 20bytes bytesper perthread). thread). 29 Summary Something Something simple simple that that works works wins wins with with anything anything complex complexthat thatisismerely merelysupposed supposedto towork. work. We We only only demonstrate demonstrate whole whole solutions, solutions, not not their their parts parts of ofallegedly allegedlysuperb superb(albeit (albeitisolated) isolated)quality. quality. 1000+ 1000+ nodes nodes industrial industrial grade grade ad-hoc ad-hoc setup setup based based on on node nodewith withcomponent componentcost costbelow below$20. $20. An An IL IL (Independent (Independent Living) Living) monitoring monitoring system system inin aa leading leadingIL ILfacility facilityininNJ. NJ. 30