A Route Discovery Method based on
Limited Flooding in
ZigBee Networks
Zijing Lin1,2, Max Q.-H. Meng 1,3 and Huawei Liang1
1 Institute of Intelligent Machines, Chinese Academy of Sciences
Hefei, Anhui Province, China
2 Department of Automation, University of Science and Technology of China
Hefei, Anhui Province, China
3 Department of Electronic Engrineering, Chinese University of Hong Kong
Shatin, Hong Kong
Proceedings of the IEEE
International Conference on Automation and Logistics
Qingdao, China September 2008
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Outline
• ZigBee Network Device
• ZigBee Routing protocol
– Simple Tree Routing Protocol(TR)
– ZigBee-AODV(ZAODV)
• LR-ZAODV
• Conclusion
2
ZigBee Network Device
• ZigBee Coordinator (ZC): The manager of the
WPAN.
• ZigBee Router (ZR): The devices that can act
as intermediate routers.
• ZigBee End Device (ZED): The devices just
have enough functionality to communicate
with the parent node and do not have the
ability of routing.
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Simple Tree Routing Protocol
• The tree network addresses are assigned using a
distributed addressing scheme.
• These addresses are unique within a particular
network. As a result, a router can acquire the
relationship of two nodes through their network
addresses.
• The ZC becomes the root of the tree.
• Every device except the ZC has a parent node,
while a ZR may also has one or more child nodes.
• A ZED acts as a leaf in the tree topology.
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Tree Architecture
圖片引用自Reference 1.
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Tree – Address assignment
• Cm: The maximum number of children a parent may have.
• Rm: The maximum number of router children a parent may
have.
• Lm: The maximum depth in the network.
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Tree – Address allocation (cont.)
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圖片引用自Reference 2.
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Tree - Determine the location of the
destination
• For a ZigBee router with network address A at
depth d, if the following logical expression is true,
the destination device with network address D is
one of its descendants.
• A < D < A + Cskip(d −1)
• If a ZigBee router receives a packet and the
destination is a descendant,
– Then the router shall relay the packet to the
corresponding child.
– Otherwise, the router forwards it to the parent node.
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Tree - summary
• Advantages
– No communication overhead
• Disadvantages
– More transmission delay (not optimal path)
– Single point of failure
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ZigBee-AODV(ZAODV)
• Another routing protocol in ZigBee (called ZAODV in
this paper) is a route discovery protocol similar to Adhoc On-demand Distance Vector Routing.
• In ZAODV, when a node desires to send data to another
node without having the related routing information, it
buffers the data and then initiates a route discovery
process to find the optimal path for the destination.
–
–
–
–
Routing Table(RT)
Route Discovery Table(RDT)
Route Request Command Frame (RREQ)
Route Reply Command Frame(RREP)
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ZAODV - Table
圖片引用自Reference 2.
Route Table
Route Discovery Table
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ZAODV - Route Cost
• The ZigBee routing algorithm uses a path cost
metric for route comparison during route
discovery and maintenance.
– It is supposed that the length of path P is L as an
ordered set of devices [D1,D2,…,DL] and a link,
[Di,Di+1], as a sub-path of length 2, then the path
cost
– Where pl is defined as
the probability of packet
delivery on the link l.
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ZAODV – Route Discovery
RREQ
RREP
圖片引用自Reference 1.
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Route Request and Reply
• RREQ
– The source node broadcasts a route request (RREQ) packet.
– If a intermediate router receives an new RREQ, it add RDT entry and
rebroadcast the RREQ.
– If a intermediate router receives an old RREQ, it shall compare the Forward
Cost in the RREQ to the one stored in the RDT entry.
If the Cost is less, the router shall update the RDT entry and rebroadcast the
RREQ again.
– Using Source Address and Route Request ID, the RREQ can be uniquely
identified.
• RREP
– The destination node receives the RREQ, it responds by unicasting a route
reply (RREP) packet to its neighbor from which it received the RREQ.
– The destination will choose the routing path with the lowest cost and then
send a route reply.
– Finally, when the RREP reaches the originator, the route discovery process is
finished.
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圖片引用自Reference 5.
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圖片引用自Reference 5.
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圖片引用自Reference 5.
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圖片引用自Reference 5.
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圖片引用自Reference 5.
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ZAODV - summary
• ZAODV can effectively reduce the transmission
delay.
• However, the procedure of flooding RREQ
wastes significant amount of bandwidth,
memory and device energy, and might cause a
“broadcast storm” problem.
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LF-ZAODV
• In order to reduce the communication overhead
of route discovery in ZigBee networks, this paper
proposes a novel route discovery method based
on limited flooding(LF-ZAODV).
• In LF-ZAODV, TR routing information is utilized to
obtain the maximum number of flooding hops
Hm, which limited the flooding of RREQ in Hm
hops.
• In LF-ZAODV, the key lies in the choice of an
appropriate Hm.
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LF-ZAODV - Condition
• To simplify the study, we make the following
assumptions in this paper:
– The nodes are constantly turned on.
– Link between neighbor nodes is symmetry.
– The nodes stay static without any movement.
– The shortest path is the optimal path.
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LF-ZAODV - Calculate Hm
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Special Case of LF-ZAODV
• Most of the time, the TR path is not optimal:
• In LF-ZAODV, the Hm is set to
.
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LF-ZAODV - Upon receipt of a RREQ
圖片引用自Reference 1.
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LF-ZAODV - Upon receipt of a RREP
圖片引用自Reference 1.
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圖片引用自Reference 1.
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Conclusion
• Advantages
– LF-ZAODV reduces about 50 percent of the
communication overhead for route discovery in sparse
networks.
– When the destination is the coordinator, LF-ZAODV
performs better and about 80 percent of
communication overhead can be reduced.
• Disadvantages
– The nodes are constantly turned on.
– The nodes stay static without any movement.
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Reference
1.
2.
3.
4.
5.
Zijing Lin, Max Q.-H. Meng, and Huawei Liang, "A Route Discovery
Method based on Limited Flooding in ZigBee Networks", Automation
and Logistics, 2008. ICAL, pp. 3039-3044, September 2008.
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