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IEEE 802.15.4 Overview 2007/11/28 Chia-Hung Tsai.

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Presentation on theme: "IEEE 802.15.4 Overview 2007/11/28 Chia-Hung Tsai."— Presentation transcript:

1 IEEE 802.15.4 Overview 2007/11/28 Chia-Hung Tsai

2 yctseng: 2 IEEE 802.15 working group

3 yctseng: 3 Comparison between WPAN

4 yctseng: 4 ZigBee/IEEE 802.15.4 market feature Low power consumption Low cost Low offered message throughput Supports large network orders (<= 65k nodes) Low to no QoS guarantees Flexible protocol design suitable for many applications

5 yctseng: 5 ZigBee/802.15.4 architecture ZigBee Alliance Defining upper layers of protocol stack: from network to application, including application profiles First profiles published mid 2003 IEEE 802.15.4 Working Group Defining lower layers of protocol stack: MAC and PHY

6 yctseng: 6 IEEE 802.15.4 device types There are two different device types : A full function device (FFD) A reduced function device (RFD) The FFD can operate in three modes by serving as Device Coordinator PAN coordinator The RFD can only serve as: Device

7 yctseng: 7 Star topology Full Function Device (FFD) Reduced Function Device (RFD) Communications Flow Network coordinator Master/slave Network coordinator

8 yctseng: 8 Tree topology Communications Flow Full Function Device (FFD) Tree

9 yctseng: 9 Device addressing Two or more devices communicating on the same physical channel constitute a WPAN. A WPAN includes at least one FFD (PAN coordinator) Each independent PAN will select a unique PAN identifier All devices operating on a network shall have a unique 64-bit extended address. This address can be used for direct communication in the PAN A device can also have a 16-bit short address, which is allocated by the PAN coordinator when the device associates with its coordinator.

10 yctseng: 10 Superframe A superframe is divided into two parts Inactive: all station sleep Active: Active period will be divided into 16 slots 16 slots can further divided into two parts »Contention access period »Contention free period

11 yctseng: 11 Superframe Beacons are used for starting superframes synchronizing with other devices announcing the existence of a PAN informing pending data in coordinators In a beacon enabled network, Devices use the slotted CAMA/CA mechanism to contend for the usage of channels FFDs which require fixed rates of transmissions can ask for guarantee time slots (GTS) from the coordinator

12 yctseng: 12 Superframe The structure of superframes is controlled by two parameters: beacon order (BO) and superframe order (SO) BO decides the length of a superframe SO decides the length of the active potion in a superframe For a beacon-enabled network, the setting of BO and SO should satisfy the relationship 0 SO BO 14 For channels 11 to 26, the length of a superframe can range from 15.36 msec to 215.7 sec (= 3.5 min).

13 yctseng: 13 Superframe Each device will be active for 2 -(BO-SO) portion of the time, and sleep for 1-2 -(BO-SO) portion of the time In IEEE 802.15.4, devices duty cycle follow the specification BO-SO0123456789 10 Duty cycle (%)1005025126.253.1251.560.780.390.195< 0.1

14 yctseng: 14 Starting and Maintaining PANs Scanning Through Channels Energy scan Active scan Devices are instructed to begin a channel scan through MLME-SCAN.request primitive The scan results shall be returned via the MLME-SCAN.confirm primitive During the scan, device shall suspend beacon transmission

15 yctseng: 15 Starting a PAN A PAN shall be started by an FFD only after an active channel scan and a suitable PAN ID has been selected An FFD uses the MLME-START.request primitive to begin operating a PAN The MAC sublayer shall set the logical channel in phyCurrentChannel and the PAN identified in macPANId Then this FFD can begin operating as a PAN coordinator

16 yctseng: 16 Beacon Generation An FFD shall use the MLME-START.request primitive to begin transmitting beacon BeaconOrder SuperframeOrder The FFD may either begin beacon transmission as The PAN coordinator of a new PAN A device on previously established PAN

17 yctseng: 17 Association procedures (1/2) A device becomes a member of a PAN by associating with its coordinator Procedures

18 yctseng: 18 Association procedures (2/2) In IEEE 802.15.4, association results are announced in an indirect fashion A coordinator responds to association requests by appending devices long addresses in beacon frames Devices need to send a data request to the coordinator to acquire the association result After associating to a coordinator, a device will be assigned a 16-bit short address.

19 yctseng: 19 Association A device shall only attempt to associate after having completed either an active channel scan or passive channel scan The results of channel scan would have then been used to choose a suitable PAN A coordinator shall only allow association if macAssociationPermit is set to TRUE

20 yctseng: 20 Association The device shall set the necessary values for association phyCurrentChannel shall be set to an appropriate channel macPANId shall be set to the identifier of the PAN with which to associate macCoordShortAddress or macCoordExtendedAddress, depending on which is knowing from the beacon frame of the coordinator

21 yctseng: 21 Association An unassociated device shall initiate the association procedure by sending an associate request command to the coordinator of an existing PAN The coordinator that successfully receives this request will reply an acknowledgment frame The ACK frame to an request command does not mean that this device has associated. The coordinator needs time to determine whether the resource available on the PAN are sufficient

22 yctseng: 22 Association If sufficient resources are available, the coordinator shall allocate a short address to the device and generate an association response command containing the new address and a status indicating a success association If sufficient resources are not available, the coordinator shall generate an association response command containing the status indicating a failure association The association response command frame shall be added to the list of pending transaction stored on the coordinator

23 yctseng: 23 Association After receiving the ACK, the device shall wait for at most aResponseWaitTime symbols for the decision The device attempt to track the beacon for the association response command If the device does not extract the response after timeout, the association attempt shall be deemed a failure The device shall terminate any tracking of the beacon

24 yctseng: 24 Association On receiving the association response command, the device shall send an ACK frame If successfully associated, the device shall store the short address and extended address of coordinator If unsuccessfully associated, the device shall set macPANId to the default value (0xffff)

25 yctseng: 25 Lab report Analyze the WUART application Trace code Sniffer - TestUtility.bin Hand in a lab report Due day 12/11 Describe the procedure of building a 802.15.4 network in WUART application Include the log analysis about sniffer

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