energy aware routing for picoradio
DESCRIPTION
Energy Aware Routing for PicoRadio. Rahul C. Shah Berkeley Wireless Research Center. Wireless Sensor Networks. Dominant trend in wireless industry: More bits/sec/Hz Wireless sensor networks offer: More bits/$/nJ. PicoRadio System Design. Wireless Sensor Nodes – Constraints. - PowerPoint PPT PresentationTRANSCRIPT
Energy Aware Routing for PicoRadio
Rahul C. Shah
Berkeley Wireless Research Center
Wireless Sensor Networks Dominant trend in wireless industry:
More bits/sec/Hz Wireless sensor networks offer:
More bits/$/nJ
PicoRadio System Design
Wireless Sensor Nodes – Constraints Low Data Rates << 10 kbps Self-configuring, maintenance-free and robust
Aggressive networking protocol stack Redundancy in deployment
Low cost: < 1$ Small size: < 1 cm3
Low power/energy Long lifetime of product requires energy-
scavenging Plausible scavenging level: < 100 W
Energy Scavenging
Practical Means of Energy Scavenging
Protocol StackIssues at the network layer: Addressing
Addressing will be class based: <location, node type, sub type>
Symbolic addressing may be supported Routing
Should route packets to the destination Given:
Destination location Position of self Position of the neighbors
PhysicalData LinkNetwork
Application
Distributed Positioning
010
2030
4050
0
20
40
600
2
4
6
8
10
Initial Position Error (%)
10 nodes, 25 waves, anchor weight=5, 30 iterations, 30% anchors, NO gradients
Range Error (%)
Ave
rage
Pos
ition
Err
or (
% o
f gr
id d
imen
sion
s)
2
1
3
4
5
6
7
89
10
1112
13
14
15
16
17
18 1920
[Chris Savarese(UCB)]
Data Link Layer Functions Transfers data
between network and physical layers;
Maintains neighborhood info
Power control, error control and access control
Computes location
ControllerSensors
Actuators
Mostly-Sleepy MAC Layer Protocols
Receiving a bit is computationally more expensive than transmitting one (receiver has to discriminate and synchronize)
Most MAC protocols assume that the receiver is always on and listening!
• Activity in sensor networks is low and randomActivity in sensor networks is low and random• Careful scheduling of activity pays off big time, but … has to Careful scheduling of activity pays off big time, but … has to
be performed in distributed fashionbe performed in distributed fashion
A Reactive PicoMAC Truly Reactive Messaging
Power Down the Whole Data Radio Reduce Monitoring Energy Consumption by 103 Times Wakeup Radio will Power Up Data Radio for Data
Reception Multi-Channel Access Scheme
To Reduce Collision Rate To Reduce Signaling Overhead (Shrink Address
Space)
Multi-Channel Access Scheme
SCA
TCARCA
Channel AssignmentUsing Distributed GraphColoring (combined with discovery)
Receiver-based ChannelAssignment: Channel code used as address
[Chunlong Guo(UCB)]
Reactive Radio Issues Broadcast and data communication modes
must co-exist simultaneously
Sleeping nodes
Communicating nodes
• Sleeping nodes have to wake-up to broadcast signals, and not to any signal leaking from surrounding communicating nodes• Broadcast signals should not disrupt data transmission
PicoRadio Routing Protocol
PicoNetwork Specifications Density of nodes – 1 node every 1 to 20
sq. m. Radio range – 3 to 10 m Average bit rate per node ~ 100-500 bps Peak bit rate per node ~ 10 kbps Very low mobility of nodes Loose QoS requirements:
Sensor data is redundant, so reliability is not required
Most data is delay insensitive
Routing Protocol Characteristics Ensure network survivability Low energy (communication and
computation) Tolerant and robust to topology
changes Scalable with the number of nodes Light weight
Network Survivability
Critical node to maintain network connectivity (network issue)
Critical node as it is the only one of its type
Network survivability is application-dependent – coverage may also be an issue
Proactive vs. Reactive Routing Proactive routing
maintains routes to every other node in the network
Regular routing updates impose large overhead
Suitable for high traffic networks
Reactive routing maintains routes to only those nodes which are needed
Cost of finding routes is expensive since flooding is involved
Good for low/medium traffic networks
Traditional Reactive Protocols
Finds the best route and then always uses that!
But that is NOT the best solution! Energy depletion in certain nodes Creation of hotspots in the network
SourceDest
Directed Diffusion†
Destination
Source
Setting up gradients
Destination
Source
Sending data
•Destination initiated•Multiple paths are kept alive
†C. Intanagonwiwat, R. Govindan and D. Estrin, “Directed Diffusion: A scalable and robust communication paradigm for sensor networks”, IEEE/ACM Mobicom, 2000
Energy Aware Routing Destination initiated routing Do a directional flooding to determine
various routes (based on location) Collect energy metrics along the way Every route has a probability of being
chosen Probability 1/energy cost
The choice of path is made locally at every node for every packet
Setup Phase
Controller
Sensor
Directional flooding
10 nJ
30 nJ
(0.75*10) + (0.25*30) = 15 nJp1 = 0.75
p2 = 0.25
Local Rule
Data Communication Phase
1.01.0
0.6
0.4
Controller
Sensor0.3
0.7
Each node makes a local decision
What’s The Advantage? Spread traffic over different paths; keep
paths alive without redundancy Mitigates the problem of hot-spots in
the network Has built in tolerance to nodes moving
out of range or dying Continuously check different paths
Energy Cost
The metric can also include: Information about the data buffered for a
neighbor Regeneration rate of energy at a node Correlation of data
initial
remainingrxtx E
EEEC )(
Simulation Setup Simulations done in Opnet 76 nodes in a typical office setup
47 light sensors 18 temperature sensors 7 controllers 4 mobile nodes
Light sensors send data every 10 seconds, while the temperature data is sent every 30 seconds
Comparison with directed diffusion routing
Simulation Model
Office layout
Nodelayout
Networkmodel
Simulation Measurements Energy used is measured:
For reception: 30 nJ/bit For transmission: 20 nJ/bit + 1 pJ/bit/m3
Packet sizes are ~ 256 bits 1 hour simulation time
Energy (mJ) Avg. Std. Dev.
Max Min
Diffusion 14.99 12.28 57.44 0.87Energy Aware Routing
11.76 9.67 41.11 0.98
Energy Usage ComparisonDiffusion Routing Energy Aware Routing
Peak energy usage was ~50 mJ for 1 hour simulation
Normalized Energy Comparison
Diffusion Routing Energy Aware Routing
Energy of each node is normalized with respect to the average energy
Bit Rate ComparisonDiffusion Routing Energy Aware Routing
Peak bit rate was 250 bits/sec.Average bit rate was 110 bits/sec.
Network Lifetime Nodes have fixed initial energy – 150 mJ Measure the network lifetime until the
first node dies out Diffusion: 150 minutes Energy Aware Routing: 216 minutes
44% increase in network lifetime
Funneling Algorithm
Controller Sensors
Border Nodes
Controller Sensors
Border Node
Interest Flooding Data Communication[w/ Dragan Petrović (UCB)]
PicoRadio Implementations
PicoNode I
sensor digital power radio
Off-the-shelf fully programmable communication/computation node
PN3 Architecture - Rx
• Two Channel• Channel Spacing ~ 50MHz• 10kbps/channel• Issues include noise suppression and isolation between RF filters• Prototype Target: 3mA @ 1V
RF Filter LNA
fclock
RF Filter PeakDet
fclock
RF Filter PeakDet
PN3 Architecture - Tx
• Use simple modulation scheme (OOK)• Allows efficient non-linear PA• Target output power: 0dBm• Prototype Target: 4mA @ 1V
PA MatchingNetwork
MOD1
MOD2
OSC1
OSC2 Preamp
PN3 Cycled Receiver
RX0
TX0
RX1
TX1