Efficient and Reliable Broadcast in ZigBee Networks

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Efficient and Reliable Broadcast in ZigBee
Networks

• Purdue University, Mitsubishi Electric Lab.
• To appear in SECON 2005

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Outline

• ZigBee network
• Broadcast problem
• Efficient and reliable forward node selection
• Performance evaluation

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ZigBee

• ZigBee Alliance an industrial consortium has
  100 companies working on low-power wireless
  networked products
• ZigBee spec chooses IEEE 802.15.4 (low-rate,
  low-power) as MAC and PHY layer
• Network and higher layer is ratified in Dec. 2004

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IEEE 802.15.4

• PHY layer 16 channels in 2.4 2.4835 GHz
  (250kb/s) 10 channels in 915 MHz (40kb/s) and
  868 MHz (20kb/s)
• Provides link quality indication (LQI) quality
  of the received packet
• MAC layer CSMA/CA (optional slotted CSMA/CA)

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ZigBee network layer

• The network layer builds a logical topology
• A coordinator starts the network and assigns
  network addresses
• The address is in a tree hierarchy
• Given the address, all its tree neighbors can be
  derived

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Example
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Broadcast problem

• Efficient reduce the number of rebroadcast nodes
• Reliable packets are received even packet loss
• Fast to cover the network timely
• Simple low complexity in computation and storage

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ZiFA

• ZigBee forward node selection algorithm
• Selects a subset of the sources one-hop
  neighbors as forwarding node
• Remove redundant broadcast
• Assumption every node knows its 1-hop neighbors
  addresses and children
• Every node knows its own tree hierarchy

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ZiFA
Draw the tree hierarchy
Start from the bottom level
Check whether the children are already the
one-hop neighbor M a set of nodes already covered
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ZiFA
Parent nodes may be missed recheck
Do the same check for every node to assign state
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Further improve

• The broadcast message comes from node u. If we
  know F(u), we can remove F(u) in our tree topology

v receives from u8 F(u8)v,u2)
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Illustrative example
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ZiFA-R

• Reliability extension of ZiFA
• The source node will wait until all its neighbors
  rebroadcast data. If not received,
  retransmission.
• For ZiFA, non-forward node will not rebroadcast

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ZiFA-R

• Observation broadcast data has higher
  probability to be received if sent by tree
  neighbors
• At least one tree neighbor of a non-forward node
  should be a forward node

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Example
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Rebroadcast - ZiRA

• Now its efficient and reliable, but may not be
  fast
• Collisions occur if nodes blindly broadcast
  simultaneously
• Solution add a random waiting time
• While waiting, it can reduce its candidate set
  based on the newly arrived data

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Determine random wait

• LQI smaller LQI, longer distance
• Might cover more nodes
• Smaller waiting time
• Degree N(v) - TN(u)
• Larger degree, more new nodes covered
• Smaller waiting time
• T k ?LQI / Degree

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Simulation

• ZigBee1 only tree neighbors as forward nodes
• ZigBee2 all 1-hop neighbors rebroadcast
• To avoid redundancy, ZiRA is implemented in
  ZigBee1,2
• Global lower bound of forward node
  (approximation)
• Other existing algorithms requires 2-hop neighbor
  information
• Not suitable for ZigBee

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Number of rebroadcast node
Radio range 25m
Radio range 55m

• Varying network density (increase)
• Varying radio range (more neighbor nodes)

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Coverage time

• Flooding is faster

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Performance of ZiFA-R

• Introduce packet loss and retransmission

ZiFA-R has more forward node
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Performance of ZiFA-R
Highest flooding ZiFA-R
Global is low cause it chooses min forward nodes
Coverage ratio
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Performance of ZiRA
ZiRA is lower in coverage time
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Conclusion

• Introduce ZigBee network into academic research
• A solution especially for zigbee network