Speaker: Yi-Lei Chang Advisor: Dr. Kai-Wei Ke 2012/05/15 IPv6-based wireless sensor network 1

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 2

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 3

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 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 ) work with 1280 bytes minimum MTU (IPv6) Transport protocol … 4

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 5

Sampled Listening 6

Sampled Listening Chirp Frame 7

Scheduling (Optimization) 8

Redefined ACK Frame 9

Listen-After-Send 10

Adaptation Layer ? 11

Node Software Architecture 12

Adaptation Layer Transmission of IPv6 Datagram over IEEE – 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 13

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IPv6 header compression Header stack 15

IPv6 header compression IPv6 header 16

Header compression HC1 encoding (1byte)Non-Compressed fields source address destination address Traffic Class and Flow Label Next Header HC2 encoding 2bit 1bit2bit1bit Smaller !! Find mostly used parameter, encode into less bit. 17

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) 18

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. 19

Header compression Cont. Next Header – 00: not compressed; full 8 bits are sent – 01: UDP – 10: ICMP – 11: TCP 20

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. 21

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 22

Configuration and Management IPv6 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 23

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 Router solicitation (RS) Router advertisement (RA) Dynamic RA interval 24

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 25

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 26

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 (more smaller packets), add an adaptation layer We can modify some network layer mechanism so they can be more suitable to WSNs And more… 27

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 , November [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, [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, [4]G. Montenegro, N. Kushalnagar, J. Hui, and D. Culler, “Transmission of IPv6 Packets [1]Over IEEE Networks,” RFC 4944 (Proposed Standard), September [5] S. Deering and R. Hinden, “Internet Protocol, Version 6 (IPv6) Specification,” RFC [1]2460 (Draft Standard), December

Thanks for Listening Q&A 29