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Study the MAC Solution IEEE802.15.4 for Wireless Sensor Networks

JasminFlorian
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Study the MAC Solution IEEE802.15.4 for Wireless Sensor Networks

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    1. Study the MAC Solution IEEE802.15.4 for Wireless Sensor Networks Azar Shamseh Wireless Ad Hoc Networking Department of Systems and Computer Engineering Carleton University, Ottawa, Canada ashamseh@yahoo.com

    3. General Characteristics Low rate Short distance Low power consumption Small memory size Low cost Star, Peer-to-Peer , Cluster-tree topologies Data rates of 250 kb/s, 40 kb/s and 20 kb/s. Support for low latency devices CSMA-CA channel access. Dynamic device addressing. Fully handshaked protocol for transfer reliability Frequency Bands of Operation

    4. Devices Full function device (FFD) Capable of being PAN coordinator Capable of being Cluster coordinator Capable of being an ordinary node Talks to any other devices (FFD, RED) Capable of any topology Reduced function device (RFD) Capable of being an ordinary node Talks only to a FFD Limited of star topology Basic communication ability limited computational ability All devices have IEEE addresses Short addresses can be allocated

    5. Supported Topology Network topology: Star topology Peer-to-peer topology (mesh-based) Cluster-tree-Topology

    6. Star Topology

    7. Peer-Peer Topology

    8. Cluster-tree-Topology

    9. Combined Topology (Cluster star)

    10. Architecture

    11. PHY Overview The PHY is responsible for: Activation and deactivation of the radio transceiver ED within the current channel LQI for received packets CCA for CSMA-CA Channel frequency selection Data transmission and reception

    12. PHY Overview The radio shall operate at one of the following license free bands: 868-868.6 MHz (e.g., Europe) 902-928 MHz (e.g., North America) or 2400-2483.5 MHz (worldwide)

    13. MAC sub-layer specification

    14. MAC Overview Frame Structure

    17. Optional Superframe Structure

    18. Guaranteed Time Slot (GTS) Certain applications require dedicated bandwidth to achieve low latency and it can operate in optional superframe mode using Guaranteed Time Slot (GTS) The rule of GTS usage is decided by the coordinator and is broadcast by the beacon frame Certain applications require dedicated bandwidth to achieve low latency and it can operate in optional superframe mode using Guaranteed Time Slot (GTS) The rule of GTS usage is decided by the coordinator and is broadcast by the beacon frame

    19. Slotted and Unslotted CSMA-CA

    20. Data Transfer Model Device to Coordinator(Uplink)

    21. Data Transfer Model Coordinator to Device(Downlink)

    22. Process of Data Access CSMA/CA MAC Protocol

    23. Zigbee IEEE 802.15.4 deals with only PHY layer and MAC layer. The higher-layer protocols are left to industry and the individual applications. The Zigbee Alliance is an association of companies involved with building higher-layer standards based on IEEE 802.15.4. This includes network, security, and application protocols.

    24. Problems Trade-off between Delay and Overhead Hidden Node Co-existence with 802.11 WLAN Shortage of GTS Beacon Collision

    25. Trade-off between Delay and Overhead Problem Small BO and SO can provide well real-time services but bring lots overhead of beacon frames

    26. Trade-off between Delay and Overhead Problem Small BO and SO can provide well real-time services but bring lots overhead of beacon frames

    27. Hidden Node Problem Caused by blind back off scheme Lake of RTS/CTS handshaking The probability of any two nodes having hidden node problem: 41% Two kinds of collision situations Caused by blind back off scheme Lake of RTS/CTS handshaking The probability of any two nodes having hidden node problem: 41% Two kinds of collision situations

    28. Beacon Collusion In a beacon enabled mode within a multi-hop network where more than one coordinators exist in the same rang, there is problem of beacon collision. The beacon may collide with another coordinator beacon or with data/control frames.

    29. Shortage of GTS Only maximum of seven time slots can be allocated for GTS Those that receive time slots may partially use it (waste of bandwidth) Many nodes may not benefit of receiving guaranteed time slots

    30. Conclusion Even though the MAC introduced in IEEE802.15.4 still is so young but I believe it is a promising technology Allow multiple topologies without complexity support FFD and RFD (low cost, small size, and simplicity) GTS (suitable for real-time applications) CSMA/CA (collusion avoidness) MAC frame provides a reasonable tradeoff between simplicity and robustness. Beacon (synchronization mechanism) I think it is best available MAC for sensor devices. It provides low-cost, low-rate and low-power consumption. It provides flexibility and simplicity which make it possible to be used by various applications. wireless connectivity among inexpensive devices. The raw data rate will be high enough (maximum of 250kbs) to satisfy a set of simple needs such as interactive toys, but scaleable down to the needs of sensor and automation needs (20kbps or below) for wireless communications. Multiple network topologies are supported including star, peer to peer. There are some issues, solutions and improvement requiredwireless connectivity among inexpensive devices. The raw data rate will be high enough (maximum of 250kbs) to satisfy a set of simple needs such as interactive toys, but scaleable down to the needs of sensor and automation needs (20kbps or below) for wireless communications. Multiple network topologies are supported including star, peer to peer. There are some issues, solutions and improvement required

    31. References Jelena Misic and Vojislav B. Misic Wireless Personal Area Network (Book) C.Siva Ram Murthy B. S. Manoj Ad Hoc Wireless Networks (Book) IEEE Standards Online http://profsite.um.ac.ir/~hyaghmae/ACN/WSNMAC1.pdf Jos�A.�Guti�rrez http://www.springerlink.com/content/a122710161r40pr1/ stsheu@ce.ncu.edu.tw http://www.csie.ntu.edu.tw/announce/news/20070112.pdf AVR Z-Link for IEEE 802.15.4 and ZigBee Applications Go wireless with AVR Z-Link http://www.atmel.com/dyn/resources/prod_documents/doc7911.pdf 802.15.4/ZigBee research center: Wireless / Mobile http://www.networkworld.com/details/6549.html A Comprehensive Performance Study of IEEE�802.15.4 by Jianliang Zheng and Myung J. Lee http://alkautsarpens.wordpress.com/2008/02/18/a-comprehensive-performance-study-of-ieee-802154/ Hwang L, Sheu ST, Shih YY, and Cheng YC (2005) Grouping strategy for solving hidden terminal problem in IEEE 802.15.4 LR-WPAN. In Proc. of the 1st International Conference on Wireless Internet (WICON'05), pp. 26-32. Many more references are used will be referred in report

    32. Q & A

    34. Q2: list the supported topology by IEEE802.15.4? What is the different between them regarding to communication? 1- star 2- peer-to-peer In star topology the communication is established between PAN coordinator and device. But in peer-to-peer any device can communicate with any other device as long as they are in the range of one another.

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