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Wireless Sensor Networks: a Survey on the State of the Art and the 802.15.4 and ZigBee Standards

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Title: Wireless Sensor Networks: a Survey on the State of the Art and the 802.15.4 and ZigBee Standards


1
Wireless Sensor Networks a Survey on the State
of the Artand the 802.15.4 and ZigBee Standards
  • Final Presentation
  • 5 August 2008
  • Omer Alkhnbashi

2
Content
  • ZigBee and IEEE802.15.4 Overview
  • IEEE 802.15.4 PHY.
  • IEEE 802.15.4 MAC.
  • ZigBee Functional Layers Architecture Protocol
    Stack.
  • Security.
  • Routing.
  • Energy Efficiency.
  • Localization.

3
Introduction
  • 802.15.4 standard defines the characteristics of
  • the physical and MAC
    layers for LR WPANs.
  • ZigBee builds upon the IEEE 802.15.4 standard
    and
  • defines the network layer
    specifications and
  • provides a framework for
    application programming
  • in the application layer.

Motorola www.motorola.com/zigbee
4
ZigBee Responsibilities
  • Designed for wireless controls and sensors
  • Operates in Personal Area Networks (PANs) and
    device-to-device networks
  • Connectivity between small packet devices
  • Control of lights, switches, thermostats,
    appliances, etc.

5
Why do we need ZigBeetechnology?
  • No standard approach today that addresses the
    unique
  • needs of most remote monitoring and control
    applications
  • Enables the broad-based deployment of reliable
    wireless networks with low-complexity, low-cost
    solutions.
  • Provides the ability to run for years on
    inexpensive primary batteries for a typical
    monitoring application.
  • Capable of inexpensively supporting robust mesh
    networking technologies.

6
IEEE 802.15.4 PHY Operating Frequency Bands
  • Direct Sequence Spread Spectrum (DSSS)
  • Channel switching, link quality estimation,
    energy detection measurement and clear channel
    assessment to assist the channel selection

ZigBee Alliance Homepage
7
IEEE 802.15.4 PHY Packet Structure
  • PHY Packet Fields
  • - Preamble (32 bits) synchronization
  • - Start of Packet Delimiter (8 bits) -
    specifies one of 3 packet types
  • - PHY Header (8 bits) PSDU length, Sync
    Burst flag
  • - PSDU (0 to 127 bytes) Data field

Start of Packet Delimiter
PHY Header
PHY Service Data Unit (PSDU)
Preamble
6 Bytes
0-127 Bytes
ZigBee Alliance Homepage
8
IEEE 802.15.4 MACDevice Classes
  • Full function device (FFD)
  • Any topology
  • Network coordinator capable
  • Talks to any other device
  • Reduced function device (RFD)
  • Limited to star topology
  • Cannot become a network coordinator
  • Talks only to a network coordinator
  • Very simple implementation

9
IEEE 802.15.4 MAC modes of operation
  • Non-beacon mode
  • 802.15.4 makes use of CSMA-CA (carrier sense
    multiple access with collision avoidance)
  • A clear channel assessment (CCA) is carried out
    before sending on the radio channel.
  • If the channel is NOT clear, we wait for a random
    period of time, before trying to retransmit.
  • Beacon mode
  • Beacon mode introduces the superframe structure
    to divide time into different transmission
    periods (Beacon, CAP, CFP and inactive)
  • During the CAP (Contention Access Period)
    communication is carried out like in non-beacon
    mode. CCAs are aligned with the
    transmission/reception of the beacon.

10
IEEE 802.15.4 MAC Frame Structure
  • A beacon frame - used by a coordinator to
    transmit beacons.
  • A data frame - used for all transfers of data.
  • An acknowledgment frame - used for confirming
    successful frame reception.
  • A MAC command frame - used for handling all MAC
    peer entity control transfers.

11
IEEE 802.15.4 MAC Super-frame
Guarantee Time Slot
Contention Access period
12
IEEE 802.15.4 MAC Super-frame
13
IEEE 802.15.4 MAC Super-frame
Data for node B
14
IEEE 802.15.4 MAC Super-frame
Ack
Store message
15
IEEE 802.15.4 MAC Super-frame
bacon Data pending For B
16
IEEE 802.15.4 MAC Super-frame
Data request
17
IEEE 802.15.4 MAC Super-frame
Data reply
Beacon
18
ZigBee Functional Layers Architecture Protocol
Stack
19
Network Layer Functions
  • Starting a network Able to establish a new
    network.
  • Joining and Leaving Network Nodes are able to
    become members of the network as well as quit
    being members.
  • Configuration Ability of the node to configure
    its stack to operate in accordance with the
    network type.
  • Addressing The ability of a ZigBee coordinator
    to assign addresses to devices joining the
    network.
  • Synchronization Ability of a node to
    synchronize with another node by listening for
    beacons or polling for data.
  • Security Ability to ensure end-to-end integrity
    of frames.
  • Routing Nodes can properly route frames to
    their destination (AODV, etc.).

20
Application Support Layer Functions
  • Zigbee Device Object (ZDO) maintains what the
    device is capable of doing and makes binding
    requests based on these capabilities.
  • Discovery Ability to determine which other
    devices are operating in the operating space of
    this device.
  • Binding Ability to match two or more devices
    together based on their services and their needs
    and allow them to communicate.

ZigBee Alliance Homepage
21
Routing
22
Routing
  • Ad hoc On Demand Distance Vector (AODV)
  • Used for mesh topologies
  • Cluster-Tree Algorithm
  • Form clusters of nodes that make a tree

ZigBee Coordinator
ZigBee Router
ZigBee End Device
Heile, B. Wireless Sensor and Control Networks,
2006
23
RoutingTreebased Routing
  • Routing only along parent-child links.
  • Routers maintain their address and the address
    info associated with their children and parent.
  • Given an address assignment in treebased network,
    router can determine if the destination belongs
    to a tree rooted at one of its router children or
    is one of its enddevice children
  • If destination belongs to one of its children, it
    routes the packet to appropriate child.
  • If destination does not belong to one of its
    children, it routes the packet to its parent

24
Routing
  • Simplified execution flow of the routing
    algorithm
  • A device is said to have routing table capacity
    if
  • It is a ZigBee coordinator or ZigBee router.
  • It maintains a routing table.
  • It has a free routing table entry or it already
    has a routing table entry corresponding to the
    destination

25
RoutingRouter Discovery(1)
  • Route Request message processing
  • RREQ when node
  • S wants to send
  • packet to node D.
  • - Setup forward
  • router (to D).

26
RoutingRouter Discovery(2)
No
  • Route Reply message processing
  • RREP from node D to
  • node S

Yes
No
Yes
Yes
No
No
No
Yes
Yes
27
Ad hoc On Demand Distance Vector (AODV)
D
  • The Ad hoc On-Demand Distance Vector protocol is
    both an on-demand and a table-driven protocol.
  • AODV supports multicasting and unicasting within
    a uniform framework.
  • Each route has a lifetime after which the route
    expires if it is not used.
  • A route is maintained only when it is used and
    hence old and expired routes are never used.

S
H. Karl, A. Willig Protocols and Architectures
for Wireless Sensor Networks, 2005
28
Cluster-Tree Algorithm
  • Protocol of logical link and network layers.
  • Forms single/multi cluster tree networks.
  • Forms self-organizing network with redundancy and
    self-repair capabilities.
  • Nodes select cluster heads and form clusters in a
    self-organized manner.
  • Self-developed clusters then connect to each
    other through a designated Device (DD).

H. Karl, A. Willig Protocols and Architectures
for Wireless Sensor Networks, 2005
29
Security
30
WSNs Security Requirements for WSN Security
  • Data Confidentiality - omission of data leaks to
    neighboring networks. Relies on centralized
    infrastructure.
  • Data Authentication - verification of
    sender/receiver.
  • Data Integrity - non altered transmission of
    data.
  • Data Freshness - ensuring data is recent while
    allowing for delay estimation.
  • .

31
WSNs Security Approaches to Security
  • Key management and Trust setup
  • Single network-wide key.
  • Using pairwise-shared key.
  • Hybrid-wide key approach.
  • Trusted server approach.
  • Asymmetric cryptography.
  • Random key pre-distribution scheme.
  • Cryptographic mechanisms
  • Secure network encryption protocol (SNEP).

32
ZigBee Security
  • ZigBee is touted as highly secure
  • Relies on centralized infrastructure
  • Coordinator acts as trust center
  • Types of keys
  • Master key
  • Installed out-of-band
  • Network key
  • Shared by all devices
  • No protection against insider attacks
  • Link key
  • Derived from master key

33
ZigBee Security Trust Center
  • Can be the coordinator or a dedicated device on
    the network
  • Trust during Join
  • Authenticate join requests
  • Network
  • Updates and distributes network key
  • End-to-End Configuration
  • Assists link key setup

ZigBee Alliance, ZigBee Security Specification
Overview, 2005
34
Energy Efficiency
35
Energy Efficiency
  • Connected Dominating Set (CDS) Approaches
  • MAC Layer Approaches
  • Slot-based Protocols.
  • S-MAC and T-MAC.
  • B-MAC.
  • Cross Layer Approaches
  • Network Support.
  • Tree-based Stream Scheduling.
  • Flexible Stream Scheduling.
  • Topology Control
  • A Model for Topology Control
  • A Taxonomy of Topology Control Approaches

36
Localization
37
Localization
  • What is Localization in WSN ?
  • Ability to determine the locations of sensors.
  • Utilize some help from localization services like
    GPS.
  • Importance of Localization
  • Identifying the location of an event or a sensor
    of interest.
  • Helping in routing and coverage optimization.
  • Some Localization Challenges
  • Accuracy VS Complexity/Cost
  • Availability and Feasibility of accurate location
    systems. (e.g. GPS is not available indoor).

38
Localization Range-Based Methods
  • Sensors calculate absolute point-to-point
    distance estimates (range) to anchors or angle
    estimates by utilizing one of the following
  • Time of Arrival (TOA).
  • Time Difference of Arrival (TDOA)
  • Angle of Arrival (AOA)
  • Received Signal Strength Indicator (RSSI)
  • Utilize some help from localization services like
    GPS.
  • Complex and depends on medium conditions and
    time synchronization
  • High computational power or requirements in
    sensors.
  • Too expensive for a large-scale WSN

TOA (GPS)
AOA
Wireless Sensor Network, An information
Processing Approach by F. Zhoa L. Guibas
39
Localization Range-Based Methods
  • Sensors never tries to estimate the absolute
    point to-point distance between anchors and the
    sensors.
  • Advantages
  • Cheap sensor hardware.
  • Low computational power
  • Disadvantages
  • Less accuracy than Region-Based methods

Wireless Sensor Network, An information
Processing Approach by F.Zhoa L.Guibas
40
ZigBee vs. Bluetooth
  • ZigBee
  • Smaller packets over large network.
  • Data rate 250 Kbps _at_2.4
  • GHz.
  • Allows up to 254 nodes.
  • Home automation, toys, remote controls, etc.
  • Bluetooth
  • Larger packets over Smaller network.
  • Data rate 1Mbps _at_2.4
  • GHz.
  • Allows up to 7 nodes.
  • Screen graphics, pictures, hands-free audio,
    Mobile phones, headsets, PDAs, etc.

ZigBee Alliance Homepage
41
What Does ZigBee Do?
  • Designed for wireless controls and sensors
  • Operates in Personal Area Networks (PANs) and
    device-to-device networks
  • Connectivity between small packet devices
  • Control of lights, switches, thermostats,
    appliances, etc.

ZigBee Alliance Homepage
42
References
  • Paolo Baronti, Prashant Pillai, Vince Chook,
    Stefano Chessa, Alberto Gotta, Y.Fun Hu,
    Wireless Sensor Networks a Survey on the State
    of the Art and the 802.15.4 and ZigBee
    Standards, Computer Communication, Volume 30 ,
    Issue 7, pages 16551695,2007.
  • ZigBee Alliance home page
  • http//www.zigbee.org/en/index.asp
  • IEEE 802.15.4 task group
  • http//www.ieee802.org/15/pub/TG4.html
  • Wireless Sensor Network, An information
    Processing Approach by F. Zhoa L.Guibas.
  • H. Karl, A. Willig Protocols and Architecture for
    Wireless Sensor Networks,2005.
  • Heile, B Wireless Sensor and Control Networks,
    2006

43
Questions
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