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Research in Wireless Ad-Hoc Sensor Networks: Routing and data transport protocols

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Research in Wireless Ad-Hoc Sensor Networks: Routing and data transport protocols Edo Biagioni presenting work done in collaboration with Kim Bridges and Brian Chee, and – PowerPoint PPT presentation

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Title: Research in Wireless Ad-Hoc Sensor Networks: Routing and data transport protocols


1
Research in Wireless Ad-Hoc Sensor
NetworksRouting and data transport protocols
  • Edo Biagioni
  • presenting work done in collaboration with
  • Kim Bridges and Brian Chee, and
  • Shu Chen, Wei Chen, Lisa Fan, Dan Morton,
  • Ben Roy, Yihua Xie
  • April 23, 2004

2
Wireless Ad-Hoc networks
  • Each node has a radio transceiver
  • Each node generates and receives data
  • Each node must also transport data for other
    senders
  • Node distribution is planned or random
  • Some issues where to send data (routing)? how to
    send data efficiently?
  • Could be mobile (MANet), fixed, or both

3
Sensor Networks
  • sensors are low-power (often battery powered),
    deployed for long periods in remote locations
  • data can be retrieved manually, but it is better
    to do so automatically over a network
  • some sensor networks might be very large, so
    scalability is an issue

4
Ad-hoc Wireless Sensor Networks
  • monitor remote sites over extended periods at low
    cost science, agriculture, tourism, military
    applications
  • e.g. study endangered plants to find out why they
    are endangered
  • e.g. monitor crops to determine when to water or
    apply fertilizer
  • environmental monitoring, and also images, and
    intrusion or herbivore detection

5
Mobile Ad-Hoc Networks
  • Nodes are assumed to be moving continuously and
    at random
  • must minimize routing overhead
  • many protocols, including DSR, AODV
  • few applications UAVs, vehicles
  • little study (so far) on performance e.g.
    transmitting TCP content

6
Challenges in WirelessAd-Hoc Sensor Networks
  • make sense of large amounts of data
    visualization
  • minimize the data transmitted model generation,
    distributed event detection
  • conserve power, e.g. by sleeping
  • re-route around nodes that have failed and nodes
    that are congested
  • deal sanely with disconnection
  • support encryption, heterogeneity

7
Protocol Design
  • efficient, reliable, high throughput, low delay
    (not unusual)
  • low power requires low delay to completion (low
    packet delay and high throughput) and high
    efficiency (do not transmit unnecessary packets)
  • low power also requires synchronization
  • baseline is flooding broadcast

8
Wireless Ad-Hoc Sensor Network Protocol Examples
9
WSNs and MANets
  • Wireless sensor network nodes are even lower
    power than MANet nodes
  • nodes may be simpler than MANet nodes
  • no motion (fixed) or limited motion
    (fixed-mobile)
  • worth discovering and using good routes
  • nodes may know position

10
building an environmental sensor network PODS
  • http//www.pods.hawaii.edu
  • high resolution images
  • sunlight, temperature, rain
  • V0 wired sensor boards
  • V1 PC-104, PC-compatibles running Linux, 802.11
    for communications, BasicStamp power control
    board
  • V2 Compaq Ipaq, Linux, 802.11
  • V3 in the planning stages

11
Multipath On-Demand Routing
  • Shu Chen
  • protocol to carry IP packets
  • establish routes on demand only send a
    broadcast, reply along the reverse path
  • may be multiple routes to a destination using
    all of them in turn provides load balancing,
    redundancy, and reliability
  • put routes on probation if they fail keep trying
    them for a little while

12
MOR performance
  • faster transmission of fixed payload (over TCP)
    than DSR, AODV
  • multipath with reliability layer effectively
    routes around congestion
  • podr long-term uninterrupted service in deployed
    pods, also works under ns-2
  • hop-by-hop ack (e.g. 802.11) to decide whether to
    retransmit on this hop

13
Lusus Protocol
  • Dan Morton
  • Really low power is only available on really
    simple processors such as PIC and AVR, with lt 1KB
    RAM, small programs
  • Need a really simple protocol
  • only send data (not IP)
  • only send to nearest base station
  • hop-by-hop, not end-to-end reliability
  • short packets, very low overhead

14
Lusus Techniques
  • base stations regularly broadcast synchronization
    messages
  • each retransmission increases the distance
  • only send to nearest base station
  • data from different sources may be combined
    enroute
  • messages are retransmitted if there is no ack
    from the next hop
  • implementation is in progress

15
Sensor Network Data Transmission ProtocolSNDT
  • Lisa Fan and Yihua Xie
  • IP over MOR, can use ssh, but
  • ssh has high overhead for small transfers
  • want connectionless, secure, and efficient
    protocol
  • use UDP, with explicit acks to minimize the
    overhead
  • rate-limit transmission to avoid generating
    congestion

16
SNDT security issues
  • initial secret is part of a node config
  • authentication to prevent bad data
  • encryption data and commands should not be
    visible without the key
  • initial secret is leveraged to exchange session
    keys
  • nodes send data to base station
  • base station sends commands and configuration to
    nodes

17
SNDT open issues
  • distributing time must be done quickly, but
    authentication takes time
  • measuring RTT is hard if decryption is needed
    before ack
  • each key must have an ID, which must be present
    on packets does this make the attacker's life
    easier?
  • maintaining session keys, and recovering from
    reboots, can be challenging

18
Distributed Route Table (DiRT)
  • Ben Roy
  • routing or forwarding to many hosts requires
    large routing tables
  • distribute the routing tables so each node has at
    most O(log(N)) routes, yet every node can reach
    every other
  • node IDs are set to be 0..N-1
  • each node i has source routes for i1, i2, i4,
    i8, etc.

19
DiRT routing
  • for node i, if the destination D is in the
    routing table, send to it
  • otherwise, compute ?D-i, the difference in
    addresses
  • for each destination j in i's routing table, find
    the one with the smallest ?, (will have at least
    one) and send to that node
  • packets require at most O(log(N)) legs, each of
    maximum length the diameter of the network

20
Distributed Routing TablesOpen Issues
  • Are there better ways to distribute large routing
    tables?
  • for example, among neighbors
  • if DiRT is used, what is the likelyhood of
    packets being rerouted along a better route
    encountered along the way?
  • analysis how much better are we really doing
    than broadcast?
  • how does network geometry affect that?

21
Geographic Routing
  • each node knows its own position, e.g. via GPS
  • if the destination is identified by position,
    simply route to the neighbor nearest the
    destination
  • can cause routing loops, e.g. at dead ends
  • many refinements, but no good solutions

22
Geometric Routing GEO
  • geographic routing works fine as long as the
    network is densely connected
  • only problems are at the edges of a connected
    area
  • communicate the geometry of the connected areas,
    and route around any holes
  • all the nodes on an edge must keep track of the
    geometry of that edge

23
GEO implementation
  • Wei Chen
  • on the ns-2 simulator
  • complex topologies simulated
  • many nodes simulated
  • scalability is good

24
Related work
  • Lots of protocols and ideas Berkeley motes,
    diffusion, Zigbee
  • The Capacity of Wireless Networks, by Gupta and
    Kumar there are limits to how much we can send
  • SPINS security protocols for sensor networks, by
    Perrig et al. --practical secure transmission on
    tiny processors
  • http//www2.ics.hawaii.edu/esb/prof/pub/ijhpca02.
    html, Biagioni and Bridges

25
Interesting Issues
  • new network, e.g. IP assumptions don't work,
    connectivity may be intermittent, and it is OK to
    design from scratch
  • low power operation is required, but there may be
    different ways to achieve it physical layer,
    data link, network layer
  • should there ever be networks where data is
    unencrypted? How can automatic encryption be set
    up effectively?

26
More issues
  • Are there better ways of routing?
  • Are there reasonable standard benchmarks for
    routing?
  • Many problems to be solved power aware routing,
    position determination, optimal node placement,
    architecture, operating system (e.g. TinyOS),
    scheduling, etc

27
Summary
  • Protocols to support goals of sensor network
    deployment MOR, Lusus, SNDT, DiRT, GEO
  • building actual sensor networks to evaluate and
    motivate the ideas
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