Prof. Younghee Lee 1 1 u Lecture 15: MANET, Wireless Mesh and Sensor networks Prof. Younghee Lee...
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Transcript of Prof. Younghee Lee 1 1 u Lecture 15: MANET, Wireless Mesh and Sensor networks Prof. Younghee Lee...
1Prof. Younghee Lee1
Lecture 15: MANET, Wireless Mesh
and Sensor networks
Prof. Younghee Lee
Computer Networks
2Prof. Younghee Lee2
Taxonomy
WirelessNetworking
Multi-hop
Infrastructure-less(ad-hoc)
Infrastructure-based(Hybrid)
Infrastructure-less(MANET)
SingleHop
CellularNetworks Wireless Sensor
Networks(?)Wireless Mesh
Networks
Car-to-car Networks(VANETs)
Infrastructure-based(hub&spoke)
802.11 802.16 Bluetooth802.11
3Prof. Younghee Lee3
Mobile Ad hoc Networks
Not using a pre-existing infrastructure– traditional cellular systems (base station infrastructure)
May need multiple hops to reach a destination Applications
– Military environments: was major motivation» soldiers, tanks, planes
Need mobility, avoid SPF, rapidly deployable, Multi-hop to reach to person outside of LOS(line of sight), when existing infrastructure is unavailable
» Survivable Radio Network(SURAN), Global Mobile(GloMo) Information System
– Civilian environments» taxi cab network, automobile communications(Cellular + ad hoc+..)» Meetings/conferences, sports stadiums, super market, Hotel…» boats, small aircraft
– Emergency operations» search-and-rescue» policing and fire fighting
– Personal area networking» cell phone, laptop, head phone, wrist watch, multimedia devices» Wearable computing
4Prof. Younghee Lee4
Routing Protocols Proactive protocols
– Establish routes in advance– Determine routes independent of traffic pattern– Traditional link-state and distance-vector routing protocols are proactive– Table driven Routing protocol
» Destination Sequenced Distance Vector Routing(DSDV)» Clusterhead Gateway Switch Routing(CGSR)
Reactive protocols– Establish routes only if needed– Less routing overhead, but higher latency in establishing the path– Source-initiated on-demand
» AODV, DSR, LMR, TORA, ABR, SSR Hybrid protocols
– Proactive within a restricted geographic area, reactive if a packet must traverse several of these areas
– ZRP, LANMAR
5Prof. Younghee Lee5
Trade-Off Latency of route discovery
– Proactive protocols:Little or no delay for route determination» since routes are maintained at all times
– Reactive protocols: Significant delay in route determination» Employ flooding (global search)» Control traffic may be bursty
Overhead of route discovery/maintenance– Proactive protocols: Consume bandwidth to keep routes up-to-date
» Maintain routes which may never be used
– Reactive protocols: Lower overhead since routes are determined on demand
Which approach achieves a better trade-off depends on the traffic and mobility patterns– Low traffic with high mobility : Reactive– High traffic with low mobility : Proactive
6Prof. Younghee Lee6
Ad hoc routing protocols
Ad hoc routing protocols
Table-drivenSource-initiated
On-demand
DSDV WRP AODV ABRDSR LMR
TORA SSRCGSR
7Prof. Younghee Lee7
Proactive Protocols
Proactive schemes based on distance-vector and link-state mechanisms– Distance vector
» Finding shortest path to destination using the route information from neighbor nodes
Bellman-ford Count to infinity problem
– Link state» Each node advertise link information using flooding
» Each node calculate shortest path
8Prof. Younghee Lee8
Destination-Sequenced Distance-Vector (DSDV) [Perkins94Sigcomm]
Each node maintains a routing table which stores– next hop towards each destination
– a cost metric for the path to each destination
– a destination sequence number that is created by the destination itself
– Sequence numbers used to avoid formation of loops Each node periodically forwards the routing table to its neighbors
– Each node increments and appends its sequence number when sending its local routing table
– This sequence number will be attached to route entries created for this node Each route is tagged with a sequence number; routes with greater
sequence numbers are preferred: newer one When a node decides that a route is broken, it increments the sequence
number of the route and advertises it with infinite metric Node mobility : routing data update period
9Prof. Younghee Lee9
Destination-Sequenced Distance-Vector (DSDV)
Assume that node X receives routing information from Y about a route to node Z
Let S(X) and S(Y) denote the destination sequence number for node Z as stored at node X, and as sent by node Y with its routing table to node X, respectively
Node X takes the following steps:– If S(X) > S(Y), then X ignores the routing information received from Y
– If S(X) = S(Y), and cost of going through Y is smaller than the route known to X, then X sets Y as the next hop to Z
– If S(X) < S(Y), then X sets Y as the next hop to Z, and S(X) is updated to equal S(Y)
Avoid Count to infinity problem
X Y Z
10Prof. Younghee Lee10
Optimized Link State Routing (OLSR) [Jacquet00ietf]
Routers maintain awareness of current network topology by exchanging beacons(“HELLO messages”)
Each nodes tells the entire network about its immediate neighbors– So each node forms a picture of the entire network topology– Each node can then calculate the best route to any destination
Flooding the network with HELLO messages incurs too much overhead– OLSR uses multi-point relay(MPR) nodes to decrease the
number of unnecessary broadcasts (only selected nodes broadcast HELLO)
11Prof. Younghee Lee11
Optimized Link State Routing (OLSR) Multi-point relays of node X are its neighbors such that each two-hop neig
hbor of X is a one-hop neighbor of at least one multipoint relay of X– Each node transmits its neighbor list in periodic beacons, so that all nodes ca
n know their 2-hop neighbors, in order to choose the multipoint relays.– The sender can select its multipoint relays (MPR) based on the one hop node
which offer the best routes to the two hop nodes.– Upon receiving a packet, a node checks it's MPRSelector set to see if the sen
der has chosen the node as a MPR. If so, the packet is forwarded, else the packet is processed and discarded.
A
B F
C
D
E H
GK
J
Node that has broadcast state information from A
12Prof. Younghee Lee12
OLSR
OLSR floods information through the multipoint relays
The flooded itself is for links connecting nodes to respective multipoint relays
Routes used by OLSR only include multipoint relays as intermediate nodes
13Prof. Younghee Lee13
A simple, efficient LS type routing protocol FSR exchanges the entire link state information only with neighbors Link state exchange is periodical Periodical broadcasts of LS info are conducted in different frequencies
depending on the hop distances– Bigger hop distance : less frequent– Smaller hop distance : more frequent
for fairly large ad-hoc network
The bold entries in figure 2 are propagated to the neighbors at the highest frequency, as they have low hop counts. The GST entry shows the neighbors corresponding to each node in the network.
FSR (Fisheye State Routing)
14Prof. Younghee Lee14
Each node maintains 4 tables - Distance table, Routing table, Link-cost table & Message retransmission list table
Link changes are propagated using update messages sent between neighboring nodes
Hello messages are periodically exchanged between neighbors to ensure connectivity
Avoids count-to-infinity problem by forcing each node to check predecessor information
» checks for consistency of all its neighbors every time it detects a change in link of any of its neighbors
The Wireless Routing Protocol (WRP) (‘96)
15Prof. Younghee Lee15
TBRPF(Topology Broadcast Based on Reverse Path Forwarding)
Full-topology link-state protocol (unlike OLSR) Each link-state update is broadcast reliably along a dynamic
min-hop-path tree rooted at the source u of the update.
16Prof. Younghee Lee16
TBRPF(Topology Broadcast Based on Reverse Path Forwarding)
Consists of two modules: the neighbor discovery module (TND) and the routing module
TND send differential HELLO messages that reports only the changes of neighbors.
The routing module operates based on partial topology information
TBRPF only propagates LS updates in the reverse direction on the spanning tree formed by the minimum-hop paths.
Only the links that will result in changes to the source tree are included in the updates
17Prof. Younghee Lee17
Reactive Routing Protocols
On demand routing protocol Large, high mobility ad hoc network Source build routes on-demand by “flooding” Maintain only active routes Route discovery cycle Typically, less control overhead, better scaling
properties Drawback: route acquisition latency
DSR, AODV, LMR, TORA, ABR
18Prof. Younghee Lee18
Dynamic Source Routing (DSR)
When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery
Source node S floods Route Request (RREQ)
Each node appends own identifier when forwarding RREQ
19Prof. Younghee Lee19
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
Represents transmission of RREQ
Z
YBroadcast transmission
M
N
L
[S]
[X,Y] Represents list of identifiers appended to RREQ
20Prof. Younghee Lee20
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
• Node D does not forward RREQ, because node D is the intended target of the route discovery
M
N
L
[S,E,F,J,M]
21Prof. Younghee Lee21
Route Discovery in DSR
Destination D on receiving the first RREQ, sends a Route Reply (RREP)
RREP is sent on a route obtained by reversing the route appended to received RREQ
RREP includes the route from S to D on which RREQ was received by node D
22Prof. Younghee Lee22
Route Reply in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
RREP [S,E,F,J,D]
Represents RREP control message
23Prof. Younghee Lee23
Dynamic Source Routing (DSR)
Node S on receiving RREP, caches the route included in the RREP
When node S sends a data packet to D, the entire route is included in the packet header– hence the name source routing
Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded
24Prof. Younghee Lee24
Data Delivery in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
DATA [S,E,F,J,D]
Packet header size grows with route length
25Prof. Younghee Lee25
Ad Hoc On-Demand Distance Vector Routing (AODV) [Perkins99Wmcsa]
DSR includes source routes in packet headers– Resulting large headers can sometimes degrade performance
AODV attempts to improve on DSR by maintaining routing tables at the nodes, so that data packets do not have to contain routes
When a node re-broadcasts a Route Request, it sets up a reverse path pointing towards the source– AODV assumes symmetric (bi-directional) links
When the intended destination receives a Route Request, it replies by sending a Route Reply
Route Reply travels along the reverse path set-up when Route Request is forwarded
26Prof. Younghee Lee26
Reverse Path Setup in AODV
B
A
S E
F
H
J
D
C
G
IK
• Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once
Z
Y
M
N
L
27Prof. Younghee Lee27
Route Reply in AODV
B
A
S E
F
H
J
D
C
G
IK
Z
Y
Represents links on path taken by RREP
M
N
L
28Prof. Younghee Lee28
Forward Path Setup in AODV
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
Forward links are setup when RREP travels alongthe reverse path
Represents a link on the forward path
Routing table entries used to forward data packet.
Route is not included in packet header.
29Prof. Younghee Lee29
AODV and DSR Differences DSR uses source routing; AODV uses next hop entry
DSR uses route cache; AODV uses route table
DSR route cache entries do not have lifetimes; AODV route table entries do have lifetimes
DSR nodes respond to each RREQ duplicate; AODV nodes only respond to first RREQ, unless one
arrives along a better path
30Prof. Younghee Lee30
DYMO – an integration of AODV and DSR
The Dynamic MANET On-demand (DYMO) routing protocol
Descendant of DSR and AODV a rewrite of AODV, using different terminology and packet
format, but having the same basic functionality IETF Draft submitted by MANET WG
– Work in progress => 4th revision Makes use of the generalised MANET packet format
– Extensible through tlvs
Path accumulation (cf. DSR) is optional No precursor list in routing table entries
31Prof. Younghee Lee31
DYMO – Route Discovery
Same as for AODV, except:– RREQ and RREP share the same message format
– Address blocks can be added to indicate path accumulation along route or addresses that need processing at each node
Originating node causes dissemination of a Routing Message (RM) throughout the network to find the target node.
Each intermediate node creates a route to the originating node. When target node receives the RM it responds with RM unicast toward
originating node. During propagation each node creates a route to the target node. When the originating node is reached routes have been established
between the originating node and the target node in both directions.
32Prof. Younghee Lee32
DYMO – Route Management
To react quickly to changes in the network topology nodes should maintain their routes and monitor their links.
When a packet is received for a route that is no longer available the source of the packet should be notified.
RERR) is sent to the packet source to indicate the current route is broken.
Once the source receives the RERR, it will re-initiate route discovery if it still has packets to deliver.
33Prof. Younghee Lee33
Flooding of Control Packets
How to reduce the scope of the route request flood ?– LAR [Ko98Mobicom]– Query localization [Castaneda99Mobicom]
How to reduce redundant broadcasts ?– The Broadcast Storm Problem [Ni99Mobicom]
34Prof. Younghee Lee34
(Flooding) Advantages
– Simplicity– May be more efficient than other protocols when rate of information
transmission is low enough» small data packets relatively infrequently, and many topology changes occur between
consecutive packet transmissions
– Potentially higher reliability of data delivery» Multiple path
Disadvantages– Potentially, very high overhead– Potentially lower reliability of data delivery
» Flooding uses broadcasting -- hard to implement reliable broadcast delivery without significantly increasing overhead
– Broadcasting in IEEE 802.11 MAC is unreliable» nodes J and K may transmit to node D simultaneously, resulting in loss of the packet
Flooding of Control Packets– The control packets are used to discover routes
35Prof. Younghee Lee35
Solutions for Broadcast Storm
Probabilistic scheme: On receiving a route request for the first time, a node will re-broadcast (forward) the request with probability p
Also, re-broadcasts by different nodes should be staggered by using a collision avoidance technique (wait a random delay when channel is idle)– this would reduce the probability that nodes B and C would forward
a packet simultaneously in the previous example Counter-Based Scheme: If node E hears more than k
neighbors broadcasting a given route request, before it can itself forward it, then node E will not forward the request– Intuition: k neighbors together have probably already forwarded the
request to all of E’s neighbors
36Prof. Younghee Lee36
Temporally-Ordered Routing Algorithm(TORA) [Park97Infocom]
TORA modifies the partial link reversal method to be able to detect partitions
When a partition is detected, all nodes in the partition are informed, and link reversals in that partition cease
Gradient based. Height Hi (τi, oidi, ri, δi, i)
– δi : order nodes w.r.t. common reference level
37Prof. Younghee Lee37
Temporally-Ordered Routing Algorithm(TORA) [Park97Infocom]
Source
Destination
Ad hoc node
Height metric
• DAG
38Prof. Younghee Lee38
Hierarchical Routing Protocols
1.CGSR (Clusterhead-Gateway Switch Routing) 2.HSR (Hierarchical State Routing) 3.ZRP (Zone Routing Protocol) 4.LANMAR (Landmark Ad Hoc Routing
Protocol)
39Prof. Younghee Lee39
CGSR (cont’d)
40Prof. Younghee Lee40
Hybrid Protocols
Zone Routing Protocol (ZRP) [Haas98] combines
– Intra-zone routing: Pro-actively maintain state information for links within a short distance from any given node
» Routes to nodes within short distance are thus maintained proactively (using, say, link state or distance vector protocol)
– Inter-zone routing: Use a route discovery protocol for determining routes to far away nodes. Route discovery is similar to DSR with the exception that route requests are propagated via peripheral nodes. => Reactive
41Prof. Younghee Lee41
Routing Summary Protocols
– Proactive, reactive and hybrid – Plenty of routing protocols
Performance Studies– Typically studied by simulations using ns, discrete event simulator– Nodes (10-30) remains stationary for pause time seconds (0-900s) and then
move to a random destination (1500m X300m space) at a uniform speed (0-20m/s). CBR traffic sources (4-30 packets/sec, 64-1024 bytes/packet)
– Attempt to estimate latency of route discovery, routing overhead …– Still many things to be done
Actual trade-off depends a lot on traffic and mobility patterns– Higher traffic diversity (more source-destination pairs) increases overhead in
on-demand protocols– Higher mobility will always increase overhead in all protocols
42Prof. Younghee Lee42
Existing Ad Hoc Multicast Routing Protocols
Tree based multicast– Source Based Tree: DVMRP, MOSPF, PIM-DM
» Scalability problem, require prior knowledge of topology information – frequent topological change !
– Core Based Tree: AODV, CBT, PIM-SM, AmRoute, AMRIS» Concentration on the shared link
Mesh based multicast– Multicast Mesh: CAMP
» Single mesh structure spanning all multicast group member» Multiple redundant paths -> avoiding frequent mesh reconfiguration, unnecessary forw
arding of multicast packet
– Group Based Forwarding: ODMRP, LBM» Location Based: LBM» A group of node: multicast forwarding nodes for each multicast group,
Is maintained instead of the links that constitute the tree or mesh» multicast packets are forwarded only by forwarding nodes: rebroadcast
Redundant path are available
43Prof. Younghee Lee43
QoS in Ad Hoc Networks QoS support in Mobile Ad hoc NETworks
– QoS support in the Internet can’t be directly used in MANETs» Bandwidth constraints» Dynamic network topology» Link state information such as delay, bandwidth, cost, error rate
Difficult to get and to manage because link states change with the surrounding circumstance
– The research on QoS support in MANETs» QoS models: feasible model» QoS resource reservation signaling: acts as control center. Coordinates the beha
viors of QoS routing, QoS MAC and other components such as scheduling, admission control..
» QoS routing: search for path with enough resource(does not reserve resources). QoS signaling without QoS routing can still work. But it works better with QoS routing.
» QoS MAC: essential component » Other components: scheduling, admission control <- can be borrowed from the othe
r network architectures without or with few modification
44Prof. Younghee Lee44
Multilayer approach to mobile networking
Why multilayer?– Layered design approach can’t meet the technical challenges of mobi
le networks– QoS can’t be provided unless it is supported across all layer of the ne
twork
Major challenge: What is the interface? Between wired network and various kinds of wireless networks (cellular, ad hoc, broadband,….)
Multilayer synergy
45Prof. Younghee Lee45
Wireless routers
Gateways
Printers, servers
Mobile clients
Stationary clients
Intra-mesh wireless links
Stationary client access
Mobile client access
Internet access links
Node Types Link Types
Overview
46Prof. Younghee Lee46
Broadband Internet Access
CableDSL
WMAN(802.16)
Cellular(2.5-3G)
WMN
Bandwidth VeryGood
VeryGood
Limited Good
Upfront Investments
VeryHigh
High High Low
Total Investments
VeryHigh
High High Moderate
Market Coverage Good Good GoodModest
47Prof. Younghee Lee47
Existing Routing Protocols
Internet routing protocols (e.g., OSPF, BGP, RIPv2)– Well known and trusted– Designed on the
assumption of seldom link changes
– Without significant modifications are unsuitable for WMNs in particular or for ad hoc networks in general.
Ad-hoc routing protocols (e.g., DSR, AODV, OLSR, TBRPF)– Newcomers by comparison
with the Internet protocols– Designed for high rates of
link changes; hence perform well on WMNs
– May be further optimized to account for WMNs’ particularities
Ad HocNetworks
Wireless MeshNetworks
48Prof. Younghee Lee48
Routing – Cross-Layer Design (cont)
Routing – Transport– Choosing routes with low
error rates may improve TCP’s throughput.
– Especially important when multiple routes are used
– Freezing TCP when a route fails.
Routing – Application– Especially with respect of sa
tisfying QoS constraints
49Prof. Younghee Lee49
Embedded Networked Sensing: Motivation
Examples; high-rise buildings self-detect structural faults (e.g., weld cracks) schools detect airborne toxins at low concentrations, trace contaminant t
ransport to source buoys alert swimmers to dangerous bacterial levels earthquake-rubbled building infiltrated with robots and sensors: locate su
rvivors, evaluate structural damage ecosystems infused with chemical, physical, acoustic, image sensors to t
rack global change parameters battlefield sprinkled with sensors that identify track friendly/foe air, groun
d vehicles, personnel Micro-sensors, on-board processing, wireless interfaces feasible at very
small scale--can monitor phenomena “up close”– Embedded Networked Sensing will reveal previously unobservable phe
nomena
50Prof. Younghee Lee50
Overall Design of Sensor Networks
One possible solution?– Internet technology coupled with ad-hoc routing mechanism
Each node has one IP address. Each node can run applications and services Application instances running on each node can communicate with each other
Why must it be different and difficult?– A sensor node is not an identity (address): Content based and data centric
» Where are nodes whose temperatures will exceed more than 10 degrees for next 10 minutes?
» Tell me the location of the object ( with interest specification) every 100ms for 2 minutes.
– Multiple sensors collaborate to achieve one goal.
– Intermediate nodes can perform data aggregation and caching in addition to routing.: where, when, how?
– Not node-to-node packet switching, but node-to-node data propagation.
– High level tasks are needed:» At what speed and in what direction was that elephant traveling?
» Is it the time to order more inventory?
51Prof. Younghee Lee51
Classifications of Sensor Nets
Sensor position– Static (Habitat, CORIE, Biomedical) – Mobile (Smart Dust, Biomedical)
Goal-driven– Monitoring: Real-time/Not-real-time (Habitat, Smart
Dust)– Forecasting (CORIE)– Function substitution (Biomedical)– …
Communication medium– Radio Frequency (Habitat, CORIE, Biomedical)– Light (Smart Dust)
52Prof. Younghee Lee52
Wireless Communication: Topology
Fixed topology– Tree based– Cluster basedCluster-based approach provides better energy-
efficiency than the tree-based approach. Dynamic topology - mobility
– Ad hoc– Infrastructure– Mixed
53Prof. Younghee Lee53
802.15 WG is developing 3 MACs and 5 PHYs, TG3a is the 6th PHY
= Draft in process or complete
= Draft not defined e.g., CFP, etc.
1 Mb/s
2.4 GH zW PAN-Bluetooth
Bluetooth(TM)802.15.1
MAC Sublayer802.15.1
11 Mb/s22 Mb/s55 Mb/s
2.4 GH zW PAN-HRHigh Rate802.15.3
110 Mb/s? Mb/s
?W PAN-HR
Higher Rate802.15.3a
MAC Sublayer802.15.3
2 kb /s20 kb /s
868-868.6 MH zW PAN-LRLow Rate802.15.4
2 kb /s20 kb /s
902-928 MH zW PAN-LRLow Rate802.15.4
2 kb /s250 kb /s
2400-2483.5 GH zW PAN-LRLow Rate802.15.4
MAC Sublayer802.15.4
802.15
802.2 LLC
PhysicalLayer
Medium AccessControl Sublayer
Logical LinkControl Sublayer
{
{
{
= Other LLC
Service SpecificConvergence Sublayer
(SSCS)
54Prof. Younghee Lee54
Comparison of routing algorithms Attributes
Algo.
Data EfficiencyEnergy Efficiency
(data/energy ratio)State complexity
Flooding Fastest Low b/c
ImplosionSmall, upstream
GossipingSlowest
No. 7
Lowest
Random walkNone
Rumor RoutingVery slow
No. 6Very low Some
SPIN Very Fast Higher than above, SPIN-EC close to ideal
Data- neighbor pairs
Directed DiffusionQuite Fast
No. 3Higher than TTDD global flooding + strong aggregation
Complex:
Neighbor X Interest
TTDDVery Fast
No.2
Reasonable
local flooding+ reasonable aggregation
OK:
Four neighbor, Constant
IP Multicast Fastest Low: b/c heavy machinery, ‘big’ node
Most complex
55Prof. Younghee Lee55
Sensor node
Sensing:– Temperature– Humidity– Light – Present of chemical– Vehicular movement– Pressure, noise level…
Data processing:– Partially process data before sending
Communicating:– Send only required data– Sensor node to base node– Base node to end user
Base node:– Gateway to user or external networks
56Prof. Younghee Lee56
Variety of Real-life Sensor Node Platforms
RSC WINS & Hidra Sensoria WINS UCLA’s iBadge UCLA’s Medusa MK-II Berkeley’s Motes Berkeley Piconodes MIT’s AMPs And many more…
Different points in (cost, power, functionality, form factor) space
57Prof. Younghee Lee57
Rockwell WINS & Hidra Nodes Consists of 2”x2” boards in a 3.5”x3.5”x
3” enclosure– StrongARM 1100 processor @ 133 MH
z» 4MB Flash, 1MB SRAM
– Various sensors» Seismic (geophone)» Acoustic» magnetometer,» accelerometer, temperature, pressure
– RF communications» Connexant’s RDSSS9M Radio @ 100 kbps, 1-
100 mW, 40 channels
– eCos RTOS Commercial version: Hidra
C/OS-II– TDMA MACwith multihop routing
http://wins.rsc.rockwell.com/
58Prof. Younghee Lee58
Berkeley Motes
Devices that incorporate communications, processing, sensors, and batteries into a small package
Atmel microcontroller with sensors and a communication unit – RF transceiver, laser module,
or a corner cube reflector
– temperature, light, humidity, pressure, 3 axis magnetometers, 3 axis accelerometers
TinyOS
light, temperature,10 kbps @ 20m
59Prof. Younghee Lee59
TinyOS System composed of concurrent FSM modules
– Single execution context Component model
– Frame (storage)– Commands & event handlers– Tasks (computation)– Command & Event interface – Easy migration across h/w -s/w boundary
Two level scheduling structure– Preemptive scheduling of event handlers– Non-preemptive FIFO scheduling of tasks
Compile time memory allocation NestC http://webs.cs.berkeley.edu
Messaging Component
Internal StateInternal Tasks
Commands Events
bit_cnt++ bit_cnt==8
Send Byte Eventbit_cnt = 0
DoneNo
Yes
Bit_Arrival_Event_Handler
State: {bit_cnt}Start
Ref: from Hill, Szewczyk et. al., ASPLOS 2000
60Prof. Younghee Lee60
UCLA iBadge
Wearable Sensor Badge– acoustic in/out + DSP– temperature, pressure, humid
ity, magnetometer, accelerometer
– ultrasound localization– orientation via magnetometer
and accelerometer– bluetooth radio
Sylph Middleware
61Prof. Younghee Lee61
Processing Common sensor node processors:
– Atmel AVR, Intel 8051, StrongARM, XScale, ARM Thumb, SH Risc Power consumption all over the map, e.g.
– 16.5 mW for ATMega128L @ 4MHz– 75 mW for ARM Thumb @ 40 MHz
But, don’t confuse low-power and energy-efficiency!– Example
» 242 MIPS/W for ATMega128L @ 4MHz (4nJ/Instruction)» 480 MIPS/W for ARM Thumb @ 40 MHz (2.1 nJ/Instruction)
– And, the above don’t even factor in operand size differences! However, need power management to actually exploit energy efficiency
– Idle and sleep modes, variable voltage and frequency
62Prof. Younghee Lee62
Sensing Several energy consumption sources
– transducer– front-end processing and signal conditioning
» analog, digital
– ADC conversion Diversity of sensors: no general conclusions can be drawn
– Low-power modalities» Temperature, light, accelerometer
– Medium-power modalities» Acoustic, magnetic
– High-power modalities» Image, video, beamforming
63Prof. Younghee Lee63
Putting it All Together: Power-aware Sensor Node
Sensors RadioCPU
Energy-aware RTOS, Protocols, & Middleware
PA-APIs for Communication, Computation, & Sensing
Dynamic Voltage & Freq.
Scaling
Scalable Sensor
Processing
Freq., Power, Modulation, & Code Scaling
Coordinated Power Management
PASTA Sensor Node Hardware Stack
64Prof. Younghee Lee64
Tracking: Mobile Script Flooding
Sensor Node
User Node
Video Node
Monitoring Target
“Tracking Script Code” injecting
65Prof. Younghee Lee65
Tracking: Event Sensing
Sensor Node
User Node
Video Node
Monitoring Target
Event Sensing
Event Sensing
Event Sensing
Event Sensing
Event Sensing
Event Sensing
Event Sensing
Event Sensing
66Prof. Younghee Lee66
Tracking: Mobile Script Activation
Tracking Code Activated
Sensor Node
User Node
Video Node
Target
Tracking Code Activated
67Prof. Younghee Lee67
Tracking: Position Notification and Code Migration
Position Information
Tracking Sensor
Node
User Node
Video Node
Target
Position Information
Tracking Script Migration
Script Migration
Monitoring
68Prof. Younghee Lee68
Tracking: Position Notification
Tracking
Sensor Node
User Node
Video Node
Target
Position Information
Tracking Script Migration
Script Migration
Monitoring
Tracking
69Prof. Younghee Lee69
Elements of Directed Diffusion
Naming– Data is named using attribute-value pairs
Interests – A node requests data by sending interests for named
data Gradients
– Gradients is set up within the network designed to “draw” events, i.e. data matching the interest.
Reinforcement– Sink reinforces particular neighbors to draw higher
quality ( higher data rate) events
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Interest Propagation
Flooding Constrained or Directional flooding based on location. Directional Propagation based on previously cached data.
Source
Sink
Interest
Gradient
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Data Propagation
Reinforcement to single path delivery.
Multipath delivery with probabilistic forwarding.
Multipath delivery with selective quality along different paths.
Source
Sink
Gradient
Data
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Reinforcement
Reinforce one of the neighbor after receiving initial data.– Neighbor(s) from whom new events received.– Neighbor who’s consistently performing better than others.– Neighbor from whom most events received.
Source
Sink
Gradient
Data
Reinforcement
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Naming
Content based naming– Tasks are named by a list of attribute – value pairs– Task description specifies an interest for data
matching the attributes – Animal tracking:
Interest ( Task ) DescriptionType = four-legged animalInterval = 20 msDuration = 1 minuteLocation = [-100, 100; 200, 400]
RequestRequest
Node dataType =four-legged animalInstance = elephantLocation = [125, 220]Confidence = 0.85Time = 02:10:35
ReplyReply
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Interest
The sink periodically broadcasts interest messages to each of its neighbors
Every node maintains an interest cache– Each item corresponds to a distinct interest
– No information about the sink
– Interest aggregation : identical type, completely overlap rectangle attributes
Each entry in the cache has several fields– Timestamp: last received matching interest
– Several gradients: data rate, duration, direction
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WSN (ZigBee) vs. IP-USN (6LoWPAN)
Transport Layer(TCP/UDP)
Network Layer(IPv6)
Adaptation Layer
Application Layer
IEEE 802.15.4MAC/PHY
Transport Layer(TCP/UDP)
Network Layer(IP)
Ethernet of otherMAC/PHY
Application Layer
Network Layer(IP)
Ethernet of otherMAC/PHY
Adaptation LayerIEEE 802.15.4
MAC/PHY
IP network 의 호스트
Data
6LowPAN 의 호스트
Data
Application Layer
Application SupportLayer
ZigBee NetworkLayer
IEEE 802.15.4MAC/PHY
Application Layer
Application SupportLayer
ZigBee NetworkLayer
IEEE 802.15.4MAC/PHY
Application Layer
Transport Layer(TCP/UDP)
Network Layer(IP)
Ethernet of other MAC
Transport Layer(TCP/UDP)
Network Layer(IP)
Ethernet of other MAC
IP network 의 호스트
Data
ZigBee 센서노드
Data
ZigBee 게이트웨이
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WSN (ZigBee) vs. IP-USN (6LoWPAN)
Sink Node
Coordinator
Sensor Node (16bit ZigBee ID)
EventRequest / Response
6LoWPAN Gateway
Coordinator
Sensor Node (IPv6 address)
EventRequest / Response
Event DB
Monitoring Center
Monitoring Center
Monitoring Center
EventUpdate
- Breaking end-to-end transparency- Limited adaptation for generic Service Architecture