Infrastructureless Wireless networks

Infrastructure-less Wireless Networks Gwendal Simon Department of Computer Science Institut Telecom 2009

Literature Books include: “Algorithms for sensor and ad hoc networks”, D. Wagner and R. Wattenhofer “Wireless sensor networks: an information processing approach”, F. Zhao and L. Guibas and journal/conferences include: ACM SigMobile (MobiHoc, SenSys, etc.) IEEE MASS and WCNC Elsevier Ad-Hoc Network, Wireless Networks 2 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Motivations Current wireless net. require an infrastructure: cellular network: interconnected base stations wiﬁ Internet: an access point and Internet 3 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Motivations Current wireless net. require an infrastructure: cellular network: interconnected base stations wiﬁ Internet: an access point and Internet Same ﬂaws than centralized architectures: cost scalability privacy dependability 3 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Motivations Sometimes, there is no infrastructure transient meeting disaster areas military interventions alter-communication 4 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Motivations Sometimes, there is no infrastructure transient meeting disaster areas military interventions alter-communication Sometimes not every station hear every other station limited wireless transmission range large-scale area 4 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Multi-hop Wireless Networks Nodes: portable wireless devices transmission ranges do not cover the area density ensures network connectivity Links: wireless characteristics transmission model: local broadcasting energy consumption: transmission is costly Behavior: devices emit, receive and forward data 5 / 41 Gwendal Simon Infrastructure-less Wireless Networks

A Taxonomy of Applications 6 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Ad-Hoc vs. Sensor Networks Ad-Hoc Networks Sensor Networks nodes powerful wiﬁ devices tiny zigbee nodes algorithms all-to-all routing echo to sink mobility human or car motions failures performance criteria quality of service energy consumption 7 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Ad-Hoc Applications Delay-Tolerant Network (social media application) assumption: no connectivity, but high mobility objective: ensuring eventual message delivery 8 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Ad-Hoc Applications Delay-Tolerant Network (social media application) assumption: no connectivity, but high mobility objective: ensuring eventual message delivery Mesh Networks (rural wireless coverage) assumption: some nodes have Internet access objective: maintaining path to these nodes 8 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Ad-Hoc Applications Delay-Tolerant Network (social media application) assumption: no connectivity, but high mobility objective: ensuring eventual message delivery Mesh Networks (rural wireless coverage) assumption: some nodes have Internet access objective: maintaining path to these nodes Vehicular Ad-Hoc Networks assumption: a particular mobility model objective: mostly services related to car safety 8 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Sensor Network Applications Sink-Based Networks (monitoring of natural areas) assumption: one sink retrieves all sensed data objective: increasing life-time 9 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Sensor Network Applications Sink-Based Networks (monitoring of natural areas) assumption: one sink retrieves all sensed data objective: increasing life-time Mobile Object Tracking (area surveillance) assumption: sensors know their location objective: determining hostile position 9 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Sensor Network Applications Sink-Based Networks (monitoring of natural areas) assumption: one sink retrieves all sensed data objective: increasing life-time Mobile Object Tracking (area surveillance) assumption: sensors know their location objective: determining hostile position Multi-Sink Networks (intervention teams) assumptions: mobile sinks and ﬁxed sensor objectives: increasing sink coverage 9 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Short Introduction to Popular Models 10 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Network as a Graph Unit-Disk Graph: 05 03 → node position 07 09 → circular transmission 12 11 06 10 01 → boolean connections 02 00 08 04 11 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Interferences Signal-to-noise-plus-interference (SINR) ratio Pu d(u,v )α Pw ≥β N+ w ∈V {u} d(w ,v )α Pu : power level of sender u d(u, v ): distance between u and v α: path-loss exponent N: noise β: minimum ratio 12 / 41 Gwendal Simon Infrastructure-less Wireless Networks

A Tour of the Most Studied Issues 13 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Broadcasting I: Stormy Effect Broadcast: a simple basic problem : a source emits a message all nodes within the network eventually receive the message a simple and efficient solution: upon first reception of message, forward it. Limits of flooding in wireless networks: redundant messages interferences 14 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Broadcasting II: Proposals Probabilistic ﬂooding: idea: forward the message with some probability p drawbacks: no guarantee of delivering reﬁnements: adjust p to node density 15 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Broadcasting II: Proposals Probabilistic flooding: idea: forward the message with some probability p drawbacks: no guarantee of delivering refinements: adjust p to node density Constrained flooding: idea: only some nodes forward the message implementation: build the Minimum Connected Dominating Set drawbacks: maintaining cost in dynamic systems 15 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Mobility Models I Few theoretical proof, few real implementations ⇒ generate realistic node motions for simulations 16 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Mobility Models I Few theoretical proof, few real implementations ⇒ generate realistic node motions for simulations The simplest model: Random Waypoint 1. each node picks a random position uniformly 2. it travels toward this destination with a speed v 3. once it reaches it, it stops during few seconds 4. back to 1 16 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Mobility Models II: Improvements Basic Structural Flaws: non-uniform distribution of node location: higher node distribution in the center average speed decay: low speed nodes spend more time to travel Realistic Mobility Models: group movement area popularity urban models community-based 17 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Mobility Models II: Improvements Basic Structural Flaws: non-uniform distribution of node location: higher node distribution in the center average speed decay: low speed nodes spend more time to travel Realistic Mobility Models: group movement area popularity urban models community-based the most realistic one : using real traces! 17 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Localized Data Gathering Basic idea: query data from sensors within an area two rounds: query diﬀusion retrieve data from sensors main objectives: minimize energy consumption minimize the delay A problem related with broadcasting except: only sensors from the queried area are reached: complex queries are possible (average, max, etc.) 18 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Time Synchronization I Different time on nodes: different oscillator frequency ⇒ frequency error absolute difference between clocks ⇒ phase error The need of a common clock localization protocols some MAC protocols data fusion in sensor network 19 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Time Synchronization II Broadcasting standard time via GPS system: √ precision, simple implementation × expensive devices × limited usage (outdoor environment) Achieve a common time distributively: √ (almost) no special devices required √ more tolerant to the environment × special protocols × message overhead, multi-hop delays 20 / 41 Gwendal Simon Infrastructure-less Wireless Networks

A Focus on Routing Protocols 21 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Routing Protocols Objective: select a path between a source and a destination Main design challenges: unstable network topology low-cost devices (energy, computing. . . ) Main routing mechanisms: neighbor discovering route setup route maintenance 22 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Proactive routing vs. On demand routing Proactive Reactive Setup all-to-all on demand Maintenance regularly during utilization Advantages no setup delay no unused routes Disadvantages ﬁxed overhead long setup delay Main examples OLSR AODV 23 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Discovery G F H S B E D A 24 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Discovery Broadcasting RREQ Mes- G sage. F H S B E D A 24 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Discovery Setting up G reverse path. F H S B E D A 24 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Discovery Replying RREP to G source. F H S B E D A 24 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Discovery Forward path G setup. F H S B E D A 24 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Maintenance Link breaks between B G and D. F H S B E D A 25 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Maintenance Sending RERR mes- G sage. F H S B E D A 25 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Maintenance Restarting route discov- G ery. F H S B E D A 25 / 41 Gwendal Simon Infrastructure-less Wireless Networks

AODV Route Maintenance New route G discovered. F H S B E D A 25 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Some Tricks Intelligent ﬂooding (detect close destination) idea: init TTL at 1, then 2, then 3. . . idea: ﬂood slowly and send message to stop it 26 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Some Tricks Intelligent flooding (detect close destination) idea: init TTL at 1, then 2, then 3. . . idea: flood slowly and send message to stop it Route caching (use past flooding) idea: during flood, answer for a distant node drawback: contradict reactive routing philosophy 26 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Some Tricks Intelligent flooding (detect close destination) idea: init TTL at 1, then 2, then 3. . . idea: flood slowly and send message to stop it Route caching (use past flooding) idea: during flood, answer for a distant node drawback: contradict reactive routing philosophy Local maintenance (almost unchanged route) idea: instead of NAK s, look for d by yourself drawback: sometimes it does not work 26 / 41 Gwendal Simon Infrastructure-less Wireless Networks

A Proactive Routing Protocol: OLSR Objective: make use of Multi-Point Relay (MPR) acting as super-peers easing topology discovery handling most of the traﬃc OLSR message types: HELLO: discover 1-hop and 2-hop neighbors topology discovery through MPR 27 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Neighbor sensing F G H S B D E A 28 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Neighbor sensing F G Nb:{S}, H 2hopNb:{} Broadcasting S B HELLO Message. Nb:{S}, 2hopNb:{} D E A Nb:{S}, 2hopNb:{} 28 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Neighbor sensing F G H S B Nb:{E}, Nb:{S,E}, 2hopNb:{} 2hopNb:{} D E A Nb:{E}, 2hopNb:{S} 28 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Neighbor sensing F G Nb:{F}, H 2hop Nb:{S} S B Nb:{E,F}, Nb:{S,E,F}, 2hop Nb:{} 2hop Nb:{} D E A 28 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Neighbor sensing F G Nb:{S,B,G}, Nb:{F,B,H}, H 2hopNb:{E,A,H} 2hopNb:{S,E,A,D} Nb:{G,D}, 2hopNb:{B,F,A} S B Nb:{E,F,B}, Nb:{S,E,F,A,G}, 2hopNb:{G,A} 2hopNb:{D,H} D E A Nb:{A,H}, Nb:{S,A,B}, Nb:{E,B,D}, 2hopNb:{B,E,G} 2hopNb:{F,G,D} 2hopNb:{S,F,G,H} 28 / 41 Gwendal Simon Infrastructure-less Wireless Networks

MPR selection F G Nb:{S,B,G}, H 2hopNb:{E,A,H} S B Nb:{E,F,B}, Nb:{S,E,F,A,G}, 2hopNb:{G,A} 2hopNb:{D,H} D E A Nb:{S,A,B}, 2hopNb:{F,G,D} 29 / 41 Gwendal Simon Infrastructure-less Wireless Networks

MPR selection F G HELLO message H indicating B as S B MPR of S and B note S as its MPR selector. D E A 29 / 41 Gwendal Simon Infrastructure-less Wireless Networks

MPR selection F G MPR Selector: MPR Selector: H {} {B,F,H} MPR Selector: {G,D} S B MPR Selector: MPR Selector: {} {S,G,E,F,A} D E A MPR Selector: MPR Selector: MPR Selector: {A,H} {} {B,E,D} 29 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Topology Table Each node maintains a Topology Table containing all possible destinations notifying a MPR to reach them Structure of Topology Table (on S for example): Dest Addr Last Hop Seq Holding Time G B 1 10 A B 4 20 D A 6 10 H G 5 15 ... ... ... ... 30 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Topology Table F G MPR Selector: H {B,F,H} S B D E A 31 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Topology Table F G H S B Topology Table Des Lhop Seq Htime D F E G 2 30 A H G 2 30 31 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Topology Table F G H MPR Selector: {G,D} S B MPR Selector: {S,G,E,F,A} D E A 31 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Topology Table F G H Topology Table Des Lhop Seq Htime S F G B2 30 H G 2 30 B G 2 30 D E A 31 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Topology Table F G H Broadcasting contin- S B ues. . . D E A MPR Selector: MPR Selector: {A,H} {B,E,D} 31 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Topology Table F G MPR Selector: MPR Selector: H {} {B,F,H} MPR Selector: {G,D} S B MPR Selector: MPR Selector: {} {S,G,E,F,A} D E A MPR Selector: MPR Selector: MPR Selector: {A,H} {} {B,E,D} 31 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Building the Routing Table Topology Table on S Neighbor Table on S Des Lhop Seq Htime Nb:{E,F,B}, F G 2 30 2hopNb:{G,A} H G 2 30 B G 2 30 Routing Table on S F B 3 30 Des Nhop Hops A B 3 30 E E 1 E B 3 30 F F 1 G B 3 30 B B 1 B A 6 30 E A 6 30 D A 6 30 A D 7 30 H D 7 30 D H 8 30 32 / 41 G Gwendal Simon8 H 30 Infrastructure-less Wireless Networks

Building the Routing Table Topology Table on S Neighbor Table on S Des Lhop Seq Htime Nb:{E,F,B}, F G 2 30 2hopNb:{G,A} H G 2 30 B G 2 30 Routing Table on S F B 3 30 Des Nhop Hops A B 3 30 E E 1 E B 3 30 F F 1 G B 3 30 B B 1 B A 6 30 A B 2 E A 6 30 G B 2 D A 6 30 A D 7 30 H D 7 30 D H 8 30 32 / 41 G Gwendal Simon8 H 30 Infrastructure-less Wireless Networks

Building the Routing Table Topology Table on S Neighbor Table on S Des Lhop Seq Htime Nb:{E,F,B}, F G 2 30 2hopNb:{G,A} H G 2 30 B G 2 30 Routing Table on S F B 3 30 Des Nhop Hops A B 3 30 E E 1 E B 3 30 F F 1 G B 3 30 B B 1 B A 6 30 A B 2 E A 6 30 G B 2 D A 6 30 H B 3 A D 7 30 D B 3 H D 7 30 D H 8 30 32 / 41 G Gwendal Simon8 H 30 Infrastructure-less Wireless Networks

Any Hybrid Approach ? Merging advantages from both approaches: build a routing table at 4 ∼ 5 hops launch a reactive process if d is not Applicative concerns: OLSR is attractive because networks often small AODV scales well but no all-to-all routing 33 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Research Activity: Multi-Sinks Query Range 34 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Multi-sink Multi-hop WSN 200 Target application: “fireman application” Many sensors (small, blue) and some firemen (large, green) 150 Firemen talk directly with the sensors Gather only local information On demand, fixed rate data gathering 100 Hop based query, constrained flooding Simple to deploy and scalable 50 0 50 100 150 200 250 300 35 / 0 41 Gwendal Simon Infrastructure-less Wireless Networks

Multi-sink Multi-hop WSN 200 Target application: “fireman application” Many sensors (small, blue) and some firemen (large, green) 150 Firemen talk directly with the sensors Gather only local information On demand, fixed rate data gathering 100 Hop based query, constrained flooding Simple to deploy and scalable Networking assumptions: 50 IEEE 802.15.4 MAC layer, ZigBee tree routing No in-network data aggregation, compression 0 Static sensors100 50 and sinks 150 (may extend to mobile 250 200 sinks) 300 35 / 0 41 Gwendal Simon Infrastructure-less Wireless Networks

Network Sharing Without Congestions 200 Capacity of sensors c = 5 Each flow consumes r = 1 Nodes within u hops generate traffic 150 Configurations Feasible? (5, 1) yes S1 100 u1 = 5 S2 50 u2 = 1 0 50 100 150 200 250 300 0 36 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Network Sharing Without Congestions 200 Capacity of sensors c = 5 Each flow consumes r = 1 Nodes within u hops generate traffic 150 Configurations Feasible? (5, 1) yes S1 100 (4, 2) no u1 = 4 S2 50 u2 = 2 0 50 100 150 200 250 300 0 36 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Network Sharing Without Congestions 200 Capacity of sensors c = 5 Each flow consumes r = 1 Nodes within u hops generate traffic 150 Configurations Feasible? (5, 1) yes S1 100 (4, 2) no (3, 2) yes u1 = 3 S2 50 u2 = 2 0 50 100 150 200 250 300 0 36 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Network Sharing Without Congestions 200 Capacity of sensors c = 5 Each flow consumes r = 1 Nodes within u hops generate traffic 150 Configurations Feasible? (5, 1) yes S1 100 (4, 2) no (3, 2) yes u1 = 2 (2, 3) yes S2 50 u2 = 3 0 50 100 150 200 250 300 0 36 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Network Sharing Without Congestions 200 Capacity of sensors c = 5 Each flow consumes r = 1 Nodes within u hops generate traffic 150 Configurations Feasible? (5, 1) yes S1 100 (4, 2) no (3, 2) yes u1 = 2 (2, 3) yes S2 50 u2 = 3 62 configurations 0 50 100 150 200 250 300 0 36 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Which Conﬁguration is Better? 200 Basic considerations: (4, 2): not feasible, (1, 1): ineﬃcient 150 100 50 0 50 100 150 200 250 300 37 / 0 41 Gwendal Simon Infrastructure-less Wireless Networks

Which Conﬁguration is Better? 200 Basic considerations: (4, 2): not feasible, (1, 1): ineﬃcient 150 Optimality criteria: 1 Maximum Impact Range 100 (5, 1): Sum up to 6 Max-Min Fairness 4 (2, 3) = (3, 2) (5, 1) 3 2 50 (?, ?, ?, ?) 0 50 100 150 200 250 300 37 / 0 41 Gwendal Simon Infrastructure-less Wireless Networks

Problem Formulation Multi-Dimensional Multiple Choice Knapsack Problem a NP-complete problem 38 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Problem Formulation Multi-Dimensional Multiple Choice Knapsack Problem a NP-complete problem Toward a distributed heuristic algorithm only local views of the network only local optimal solutions 38 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Protocol 200 At each sink: enlarge requirement periodically receive notiﬁcation from sensors 150 adjust requirement if it is smaller At each sensor: 3 100 measure the traﬃc detect congestion A 50 4 2 1 solve the local problem notify related sinks 0 50 100 150 200 250 300 39 / 0 41 Gwendal Simon Infrastructure-less Wireless Networks

Conclusion 40 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Personal Thoughts Great theoretical importance: a lot of new and scientiﬁcally exciting problems a multi-disciplinary ﬁeld (network, algorithms, computational geometry, probabilities) 41 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Personal Thoughts Great theoretical importance: a lot of new and scientiﬁcally exciting problems a multi-disciplinary ﬁeld (network, algorithms, computational geometry, probabilities) Unsure applicative importance: no killer application yet cellular networks just do what we want 41 / 41 Gwendal Simon Infrastructure-less Wireless Networks

Infrastructureless Wireless networks

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