Multibasestation Sensor Network Hybrid MAC

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Multi-base-station Sensor Network Hybrid MAC
Route protocol

• Jian-chuan Lu
• visiting scholar
• DAWN Lab
• EECS of Washington State University
• 19th January 2001

2
Outline of Topics

• Network architecture and hybrid protocol
• Key issues
• Route based on S/N
• Time delay and overhead of network
  self-organization
• Problems related to base-station mobility
• Performance simulation metrics
• Further research

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Hybrid multi-base-station architecture
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Hybrid type station , hybrid protocol

• sensor synchronize to basestation
• 5 phase network self-organization
• topology discovery, adaptation
• Hybrid TDMA/CSMA
• Downlink,direct TDMA broadcast
• Uplink, multi-hop CSMA with priority
• Sensor broadcast 1 time/superframe
• to discovery neighbor, basestation
• need to know all of its member sensor
• node but not their connection relation
• Basetation acts as a local switch center
• each packet to local sensor node must
• pass through it
• Inter-cluster communication through
• relay of gateway sensor nodes
• Uplink route based on S/N value measured
• by sensor node
• Can adapt to basestation mobility
• Support multi mode communication

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Key problems

• Route based on S/N
• Time delay and overhead of network
  self-organization
• Problems related to base-station mobility

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Route based on S/N

• S/N based route choice for intra-cluster uplink
  communication
• the value of S/N indicate the relative distance
  between base-station and sensor node
• by choice the node of larger S/N as next hop
  will hopefully finally transfer data packets to
  base-station.
• Limitation and precondition
• Signal strength irregular variation as distance
  multipath, fading, scattering, shadowing
• Measure accuracy long enough measure time,
  average of multiple measurement
• Effectiveness of S/N due to base-station
  mobility periodically update, 1update/superframe(
  1 minute). Multiple measurement during
  receiving/monitoring downlink signal
• HOW to cope with random signal level variation
  and fading?

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Route based on S/N

• Log-normal-shadowing model
• PrPo-10n log(r/ro)X
• How to guarantee to choice
• right next hop node?
• assume
• Sth Minimum S/N resolution
• Dmaxmaxim sensor Tx distance
• n RF signal propagation factor
• a signal level variance
• then ,probability of right choice is
• (choice the node more near to FaN as next hop)
• Q(2(Sth-10nlogDmax)/a)

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network self-organization

• The completion of networking self-organization
  means
• every sensor node knows its NCT
• every FaN know its MNT and other FaNs MNT
• At the end of sensor node broadcast phase, every
  sensor node should form its NCT
• Key time delay is for MNT construction and
  dissemination (to whole network range)

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Measurements to reduce network organization
delay

• Improved CSMA/CA, give MNT related packets high
  priority
• Reduce possible collision, let nodes of lower S/N
  transmit first.
• Each node monitor and wait all its neighbor
  nodes packets,
• only after all of its neighbor of lower S/N
  have sent their
• RequestRegiste packet, this node start to
  contend channel.
• The direct effects of this algorithm are
• reduce possible collision
• reduce transmission times of intermediate node to
  relay other nodes packets,
• each node only need to transmit one time
• increase channel utilization.

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CSMA/CA with priority

• Purpose of CSMA with priority
• .Reduce delay for high priority traffic
• .Stagger channel contending window to reduce
  collision

DIFS
1
2
3
4
812
1216
04
48
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Outward nodes first
Monitor channel
Analysis packets type and source/destination
Case RequestRegiste from outwards node
CaseMNT to me
Caseapplication data
1
Add to Request node list
2
3
no
2
4
All outward nodes issued RequeseRegist packet?
4
3
1
5
yes
5
4
2
5
3
Contend channel for transfer To inward node
2
3
4

• Guarantee FaN get its MNT in less than one
  uplink frame2s

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Dissemination of MNT

• After receive a MNT packet, node retransmits it
  immediately. MNT traverses through one subnet
  need at least one downlink frame (1s) and one
  uplink frame(2s)

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Problems related to base-station mobility

• Base-station moving may cause
• 1st hop node cant reach basestation directly
• Gateway node cant receive downlink packets
• Some node cant receive downlink packets.

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Problems related to base-station mobility

• Solution for
• Problem 1)
• Store the packets received until next
  superframe, then transmit them to its new inward
  node. Maximum time delay1 superframe
• Problem 2)
• Active response Gateway node monitor
  basestations signal, once its S/N is lower than
  threshold value, inform basestation
• Passive response basestation cant receive ACK
  in the preceding uplink frame after it transmits
  a packet to Gateway node.
• After discover Gateway node cant reach,
  basestation start to poll other candidate Gateway
  nodes in the downlink frame, which have suitable
  S/N value pair .
• Once received polling message, these nodes
  monitor another subnets signal, if its
  S/Ngtthreshold, then it response to polling and
  start to issue NeighborFinding packet. Time to
  spend about 6s
• Problem 3)
• Just retransmit them in the next superframe
  if there is no ACK received.

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Performance simulation metrics

• Time performance
• network organization time
• route table update delayNCT, MNT
• data packets average transmission delay
  multi hop, multi round
• CSMA with priority Delay performance
  analysis, how many delay gains
• can be obtained for high priority packets?
  How the low priority traffic be suffered?
• Throughput performance
• overhead calculate
• channel utility efficient
• maxim simultaneous transmission packets
• Energy performance
• life time
• number of packets transmitted/energy
• Parameter optimization
• eg. Back-off time,
• Comparative analysis with other protocol
  

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Further research

• Protocol simulation, emulation, and
  implementation
• Theory analysis and modeling
• Improve energy conserving
• Combination with rendezvous protocol

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RTS/CTS 4 way handshake access method

• Channel access using RTS/CTS

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Multi mode communication requirement
User or LRP
Node to User
Node Broadcast to all Neighbors
Node to Specific Neighbor
Multicast among Set of Nodes (e.g., corroborate)
User Broadcast to all Nodes
User to Specific Node
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Sensor network characteristics

• Low power consumption
• Low bandwidth, single channel and short range
• Periodic with low or high duty cycle
• Mostly send and route network
• Small packet and no streaming
• A dynamic network