Speaker: Yi-Lei ChangAdvisor: Dr. Kai-Wei Ke

2012/05/15

IPv6-based wireless sensor network

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Outline

• 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 ListeningChirp 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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• 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

Header compression Cont.

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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 ManagementIPv6 address auto-configuration

• Statelessly by combining a 64-bits IEEE EUI-64unique 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 ManagementIPv6 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

• Router solicitation (RS)• Router advertisement (RA)• Dynamic RA interval

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ForwardingHop-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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ForwardingQuality 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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