IPv6-based wireless sensor
network
Speaker: Yi-Lei Chang
Advisor: Dr. Kai-Wei Ke
2012/05/15
1
Outline
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•
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•
•
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Introduction
Challenges of IP over WSNs
Things we can do in link layer
Add an adaptation layer
Make network layer more suitable for WSNs
Conclusions
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Introduction
• WSN
– Limited power
• Low TX power, unstable link…etc.
– Limited computing ability
– Low cost  lots of nodes
• IP over WSN
– Why need IP in WSNs
– IPv6 vs. IPv4
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Challenges of IP over WSNs
• WSNs are...
– Limited node energy
• Less transmitting and computing power
– High packets loss rate
– Limited bandwidth
• 250 Kbps for IEEE 802.15.4
• So, when IP over WSNs…
– Large header overhead
• 40 bytes IPv6 header
– Global addressing scheme
• Need auto-configuration
– Other implementation challenges
• 127 bytes maximum physical layer packet size (IEEE 802.15.4) work with 1280 bytes
minimum MTU (IPv6)
• Transport protocol
• …
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Things we can do in link layer
• Lower energy cost
– Duty-cycled link
• Sampled Listening
– Scheduling
– Listen-After-Send
• More quality link
– Streaming
– Redefined ACK Frame
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Sampled Listening
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Sampled Listening
Chirp Frame
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Scheduling (Optimization)
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Redefined ACK Frame
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Listen-After-Send
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Adaptation Layer ?
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Node Software Architecture
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Adaptation Layer
• Transmission of IPv6 Datagram over IEEE
802.15.4
– IPv6 header compression
• To reduce header overhead
– Datagram fragmentation
• Fragmentation header
• To support the IPv6 minimum MTU
– Support for layer-two forwarding
• Layer3 routing, layer2 forwarding
• Reduce processing power
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IPv6 header compression
Header stack
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IPv6 header compression
IPv6 header
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Header compression
HC1 encoding (1byte)
Non-Compressed fields
source
address
destination
address
Traffic
Class
and
Flow
Label
Next
Header
HC2
encoding
2bit
2bit
1bit
2bit
1bit
Smaller !!
Find mostly used parameter, encode into less bit.
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Header compression Cont.
• Source/destination address
–
–
–
–
00: PI, II
01: PI, IC
10: PC, II
11: PC, IC
–
–
–
–
PI: Prefix carried in-line
PC: Prefix compressed (link-local prefix assumed).
II: Interface identifier carried in-line
IC: Interface identifier elided (derivable from the
corresponding link-layer address)
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Header compression Cont.
• Traffic Class and Flow Label
– 0: not compressed; full 8 bits for Traffic Class and
20 bits for Flow Label are sent
– 1: Traffic Class and Flow Label are zero
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Header compression Cont.
• Next Header
– 00: not compressed; full 8 bits are sent
– 01: UDP
– 10: ICMP
– 11: TCP
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Header compression Cont.
• HC2 encoding
• 0: No more header compression bits
• 1: HC1 encoding immediately followed by
more header compression bits per HC2
encoding format.
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Make network layer more suitable
for WSNs
• Configuration and Management
– IPv6 address auto-configuration
– IPv6 neighbor discovery
• Forwarding
– Hop-by-Hop Recovery
– Quality of Service
• Routing
– DAG (Directed acyclic graph)
– distance-vector protocol
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Configuration and Management
IPv6 address auto-configuration
• Statelessly by combining a 64-bits IEEE EUI64unique identifier with an IPv6 address prefix
(e.g., link-local or subnet ID) server
• Using DHCPv6 to assign an address
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Configuration and Management
IPv6 neighbor discovery
• Neighbor Table
– Cache  Table
– Reduce address resolution exchange
• Address Resolution
– Link-local multicast query
 router advertisement
• Neighbor Unreachability Detection (NUD)
– Neighbor solicitation (NS)
– Neighbor advertisement (NA)
 link-layer acknowledgments
• Router Discovery
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•
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Router solicitation (RS)
Router advertisement (RA)
Dynamic RA interval
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Forwarding
Hop-by-Hop Recovery
• The two most common reasons for delivery
failures
– Link transmission failures
– Queue congestion at the receiver
• Detected using hop-by-hop acknowledgments
• Using flag to tell the difference
• Forwarder can retransmit/reroute
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Forwarding
Quality of Service
• Classes
– ND, routing protocols, and local communication
– Upward traffic towards edge routers for data
collection
– Downward traffic away from edge routers for
configuration or control traffic
• Queue reservations
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Conclusions
• We can use link layer mechanism to lower power
consumption and improve link quality, make
WSNs more powerful to carry IP.
• For transmission of IPv6 Datagram (big packets)
over IEEE 802.15.4(more smaller packets), add an
adaptation layer
• We can modify some network layer mechanism
so they can be more suitable to WSNs
• And more…
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Reference
[1]J.W. Hui and D.E. Culler, "IPv6 in Low-Power Wireless Networks,“ Proceedings of the
[1]IEEE, vol. 98, no. 11, pp. 1865-1878, November 2010.
[2]J.W. Hui, "An Extended Internet Architecture for Low-Power Wireless Networks
[1]Design and Implementation,” PhD thesis, University of California at Berkeley,
[1]Berkeley, CA, USA, 2008.
[3]Joel J. P. C. Rodrigues , Paulo A. C. S. Neves "A survey on IP-based wireless sensor
[1]network solutions", Int. J. Communication Systems, vol. 23, pp. 963–981, 2010.
[4]G. Montenegro, N. Kushalnagar, J. Hui, and D. Culler, “Transmission of IPv6 Packets
[1]Over IEEE 802.15.4 Networks,” RFC 4944 (Proposed Standard), September 2007.
[5] S. Deering and R. Hinden, “Internet Protocol, Version 6 (IPv6) Specification,” RFC
[1]2460 (Draft Standard), December 1998.
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Thanks for Listening
Q&A
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