IEEE 802.15.4 MAC and PHY Specifications for LR …read.pudn.com/downloads55/ebook/189875/IEEE802.15.4 MAC...TKU HSNL LR-WPAN - 1 IEEE 802.15.4 MAC and PHY Specifications for LR-WPANs

TKU HSNL LRTKU HSNL LR--WPAN WPAN -- 11

IEEE 802.15.4IEEE 802.15.4MAC and PHY Specifications MAC and PHY Specifications

for LRfor LR--WPANsWPANs

中央大學通訊系許獻聰

E-mail: [email protected]

mailto:[email protected]


Outline

1. IEEE 802.15.4 Architecture and Overview2. IEEE 802.15.4 PHY3. IEEE 802.15.4 MAC


1. 802.15.4 Architectureand Overview


IEEE 802.15 Working Group


Applications

• Sensors & actuators• Interactive toys• Smart badges• Health monitoring• Computing peripherals• Remote control• Home Automation• Automatic Meter Reading


New Trend of Wireless Technology

• Most Wireless industry focus on increasing increasing high data throughputhigh data throughput

• A set of applications requiring simple wireless connectivity, relaxed throughputrelaxed throughput, very low very low power, short distancepower, short distance and inexpensiveinexpensive– Industrial – Agricultural– Vehicular– Residential– Medical


Wireless MarketsSH

OR

T

<

RA

NG

ER

AN

GE

>

LON

G

LOW < DATA RATEDATA RATE > HIGH

PANPAN

LANLAN

TEXT GRAPHICS INTERNET HI-FI AUDIO

STREAMINGVIDEO

DIGITALVIDEO

MULTI-CHANNELVIDEO

Bluetooth1

Bluetooth 2ZigBee

802.11b

802.11a/HL2 & 802.11g

Reference from ZigBee Alliance Inc.


Wireless Technologies


10

100

1,000

10,000

10 100 1,000 10,000 100,000

Bandwidthkbps

GSM

802.11a/g

GPRS EDGE 20002003-4

2005

Bluetooth

3G

HiperLAN/2Bluetooth 2.0

RangeMeters

802.11bZigBee

WiMediaBluetooth 1.5


WLAN vs WPAN


Wireless Applications

ZigBeeLOW DATA-RATE RADIO DEVICES

HOME AUTOMATION

CONSUMER ELECTRONICS

TVVCRDVD/CDremote

securityHVAClightingclosures

PC & PERIPHERALS

TOYS & GAMES

consolesportables

educational

PERSONAL HEALTH CARE

INDUSTRIAL & COMMERCIAL

monitorssensors

automationcontrol

mousekeyboardjoystick

monitorsdiagnostics

sensors



Architecture

•• ZigBeeZigBee AllianceAlliance– 45+ companies: semiconductor

mfrs, IP providers, OEMs, etc.– Defining upper layers of protocol

stack: from network to application, including application profiles

– First profiles published mid 2003•• IEEE 802.15.4 Working GroupIEEE 802.15.4 Working Group

– Defining lower layers of protocol stack: MAC and PHY

– draft D18 (will be finalized 2003)

ZIGBEE STACKZIGBEE STACK

APPLICATIONAPPLICATION CustomerCustomer

IEEEIEEE802.15.4802.15.4

ZigBeeZigBeeAllianceAlliance

SILICONSILICON


What is unique about wireless PAN (WPAN)?

•• Wireless Personal Area Networks (Wireless Personal Area Networks (WPANsWPANs))– short distance– small (ultra low complexity)– low duty-cycle (<0.1%)– power efficient (the most important factor)(the most important factor)– inexpensive (ultra low cost) solutions.

• Typically operating in the Personal Operating Personal Operating Space (POSSpace (POS)) of 10 meters10 meters.

• Supporting starstar and peerpeer--toto--peerpeer topologies– controlled by the PAN coordinatorPAN coordinator


WPAN Features

• Media access is contention based.– Using carrier sense multiple access with collision carrier sense multiple access with collision

avoidance (CSMA/CA)avoidance (CSMA/CA) MAC protocol– Similar to IEEE 802.11 CSMA/CA protocol, but not the same

• Provide the optional SuperframeSuperframe structurestructure– The PAN coordinator periodically allocates guaranteed time guaranteed time

slotsslots (GTS)(GTS) to low latency devices• Dynamic device addressing

– Two kinds of address of a device–– 1616--bit Short Addressbit Short Address–– 6464--bit Extended Addressbit Extended Address

•• Fully acknowledged protocolFully acknowledged protocol for transfer reliability.


Device Classes in WPAN

• There are two different device types :–– A full function device (FFD)A full function device (FFD)–– A reduced function device (RFD)A reduced function device (RFD)

• The FFD can operate in three modes serving–– DeviceDevice–– CoordinatorCoordinator–– PAN coordinatorPAN coordinator

• The RFD can only operate in a mode serving:–– DeviceDevice

•• Coordinator provides Coordinator provides synchronization informationsynchronization information to to other devicesother devices


FFD vs RFD

• Full function device (FFD)–– AnyAny topology– Network coordinator capable– Talks to any other device

• Reduced function device (RFD)– Limited to starstar topology– Cannot become a network coordinator– Talks only to a network coordinator– Very simple implementation


Network Topologies

•• Star and Peer2Peer TopologiesStar and Peer2Peer Topologies


Network Topologies

•• Star network Star network formationformation:– An FFD may establish its own network and become the PAN

coordinator.– All star networks operate independently.– Choosing a PAN identifier, which is not currently used by any

other network within the radio sphere of influence.– Both FFDs and RFDs may join the network.

•• PeerPeer--toto--peer network peer network formationformation:– Each device is capable of communicating with any other

device.– One FFD device will be nominated as the PAN coordinator.


Network Topologies

•• Star TopologyStar Topology– In star topology, data may be exchanged only

between the coordinator (FFD) and a device (FFD or RFD).

•• PeerPeer--Peer TopologyPeer Topology– In a peer-to-peer topology,data may be exchanged

between any two devices (FFDs).


Star Topology

Full Function Device (FFD)Reduced Function Device (RFD)Communications Flow

Master/slave

NetworkNetworkcoordinatorcoordinator

Master/slave

NetworkNetworkcoordinatorcoordinator


Star Topology

•• Home ApplicationHome Application

FFDRFD

RFD

RFD

FFD

FFD

RFD

FFDRFD

RFD

RFD

FFD

FFD

RFD

PAN coordinatorPAN coordinator


Peer-Peer Topology

Communications FlowFull Function Device (FFD)

Point to pointPoint to point Tree


Cluster Tree Topology

• Only one PAN coordinator• No detail yet

PAN coordinatorPAN coordinatorCluster HeadCluster Head


Combined Topology (Cluster Star)

Peer2Peer Communications FlowStar Communications Flow

Full Function Device (FFD)Reduced Function Device (RFD)

Room 1Room 2

Room 3

Room 4


Cluster Tree Establishment

• The PAN coordinatorPAN coordinator forms the first cluster by establishing itself as the cluster head (CLH)cluster head (CLH) with a cluster identifier (CID) of zerocluster identifier (CID) of zero.

• Choosing an unused PAN identifierunused PAN identifier (PANID)(PANID) and broadcasting broadcasting beaconbeacon framesframes to neighboring devices.

• A candidate device receiving a beacon frame may request to join the network at the CLH.

• If the PAN coordinator permits the device, it will add the new device as a child device in its Access Control List (ACL).

• The newly joined device will add the CLH as its parent in its ACL, and begin transmitting periodic beacons.

• Other candidate devices may then join the network at that device. A larger network (PAN) is possible by forming a mesh of multiple neighboring clusters.

• The PAN coordinator may instruct a device to become the CLH of a new cluster adjacent to the first one.

• Other devices gradually connect and form a multi-cluster network structure.


Device Addressing

• All devices have IEEE addresses (64-bits)• Short addresses (16-bit) can be allocated• Addressing modes:

– Network + device identifier (star)– Source/destination identifier (peer-peer)– Source/destination cluster tree + device identifier

(cluster tree)


2. 802.15.4 Physical Layer


PHY Specifications

• The standard specifies twotwo PHYs :–– 868 MHz/915 MHz868 MHz/915 MHz direct sequence spread

spectrum (DSSS) PHY (11 channels)(11 channels)»» 11 channel (20Kb/s)(20Kb/s) in European 868MHz band»» 1010 channels (40Kb/s)(40Kb/s) inin 915 (902-928)MHz ISM band

–– 2450 MHz2450 MHz direct sequence spread spectrum (DSSS) PHY (16 channels)(16 channels)

»» 1616 channels (250Kb/s)(250Kb/s) in 2.4GHz band


Operating Frequency Range

• A total of 27 channels, numbered 0 to 26, are available across the three frequency bands.

• 16 channels are for 2450 MHz, 10 are for 915 MHz an 1 is for 868 MHz.

BANDBAND COVERAGECOVERAGE DATA RATEDATA RATE CHANNEL(S)CHANNEL(S)

2.4 GHz ISM Worldwide 250 kbps 16

868 MHz Europe 20 kbps 1

915 MHz ISM Americas 40 kbps 10


3. 802.15.4 MAC Layer


Protocol Layer

PHY LAYER2.4 GHz 915MHz 868 MHz

MAC LAYERMAC LAYER

DATA LINK LAYER

NETWORK LAYERStar/Cluster/Mesh

APPLICATION INTERFACE

APPLICATIONS

Silicon

ApplicationZigBee Stack

Customer

IEEE802.15.4

ZigBeeAlliance

SECURITY


IEEE 802.15.4 feature

•• Extremely low costExtremely low cost

•• Ease of installationEase of installation

•• Reliable data transferReliable data transfer

•• Short range operationShort range operation

•• Reasonable battery lifeReasonable battery life

Simple but flexible flexible protocol


General Frame Structure

•• FourFour Types of Frames StructureTypes of Frames Structure:–– Beacon FrameBeacon Frame - used by coordinator

–– Data FrameData Frame - used for all transfers of data

–– Acknowledgment FrameAcknowledgment Frame - used for confirming successful frame reception

–– MAC CommandMAC Command Frame Frame - used for handling all MAC peer entity control transfers


Superframe Structure

• The LR-WPAN allows the optional use of a superframestructure.

• The format of the superframe is defined by the coordinator.• The superframe is bounded by network beacons, is sent by the

coordinator and is divided into 16 equally sized slots.• The beacon frame is transmitted in the first slot of each

superframe.• If a coordinator does not wish to use a superframe structure it

may turn off the beacon transmissions.• The beacons are used to synchronize the attached devices, to

identify the PAN, and to describe the structure of the superframes.

• Any device wishing to communicate during the contentionaccess period (CAP) between two beacons shall compete with other devices using a slotted CSMA-CA mechanism.

• All transactions shall be completed by the time of the next network beacon.


Superframe Structure• The superframe can have an active and an inactive portion. During

the inactive portion the PAN enters a low power mode.• The PAN coordinator may dedicate portions of the active

superframe to some devices/applications. These portions are called guaranteed time slots (GTSs).

• The GTSs comprise the contention free period (CFP). • The PAN coordinator may allocate up to 7 of these GTSs and a

GTS may occupy more than one slot period. (Note:all slots may beallocated for CFP.)

• All contention based transactions shall be complete before the CFP begins. Also each device transmitting in a GTS shall ensure that its transaction is complete before the time of the next GTS or the end of the CFP.


Superframe Structure• The structure of this superframe is described by the

values of macBeaconOrder ((BOBO)) and macSuperframeOrder ((SOSO)).– The macBeaconOrder describes the interval at which the

coordinator shall transmit its beacon frames. – The macSuperframeOrder describes the length of the active

portion of the superframe, which includes the beacon frame.


Data Transfer Model

q There are three typesthree types of data transfer transactions.1) Device -> Coordinator2) Coordinator -> Device3) Device (coordinator) -> Device (coordinator)


Data Transmissions

(1)(1) Data transferred from device to coordinatorData transferred from device to coordinator– In a beaconbeacon--enableenable network, device finds the beaconbeacon to

synchronize to the superframe structure. Then using slotted CSMA/CAslotted CSMA/CA to transmit its data.

– In a non beaconnon beacon--enableenable network, device simply transmits its data using unslottedunslotted CSMA/CACSMA/CA

Communication to a coordinatorIn a beaconbeacon--enabled networkenabled network

Communication to a coordinatorIn a nonnon beaconbeacon--enabled networkenabled network


Data Transmissions

(2) Data transferred from coordinator to device(2) Data transferred from coordinator to device– In a beaconbeacon--enable networkenable network, the coordinator indicates in

the beacon that the data is pendingpending. Device periodically listens to the beacon and transmits a MAC command MAC command requestrequest using slotted CSMA/CAslotted CSMA/CA if necessary.

– In a non beaconnon beacon--enable networkenable network, a device transmits a MAC command requestMAC command request using unslottedunslotted CSMA/CACSMA/CA. If the coordinator has its pending data, the coordinator transmits data frame using unslottedunslotted CSMA/CACSMA/CA. Otherwise, coordinator transmits a data frame with zero lengthzero lengthpayloadpayload.


Data Transmissions (Indirect mode)

Communication from a coordinator in a non beaconnon beacon--enabled networkenabled network

Communication from a coordinatorIn a beaconbeacon--enabled networkenabled network

• indirect transmissionindirect transmission

pending listpending list


Indirect transmissions

• Since the standard favors very low cost devices that, in general, will be battery powered, transactions can be instigated from the devices themselves rather than from the coordinator.– either coordinator indicates in its beacon when messages

are pending for devices– or devices polls the coordinator to determine if they have any

messages pending. – Such transfers are called indirect transmissionsindirect transmissions.

• For each transaction sent, if another exists for the same device, the coordinator sets its frame pending pending subfieldsubfield to 1, indicating the additional pending data. – Like ‘more data’ flag used in IEEE 802.11


Pending Address Field

maximal 7 addressesmaximal 7 addresses

Beacon Frame


Peer-to-Peer Data Transfers

• In order to do this effectively, the devices wishing to communicate will either need to be receiving constantly or they will need to synchronize with each other.

• The device simply transmits its data using unslottedCSMA-CA. Other measures need to be taken in order to achieve synchronization.

• Incomplete approach


Frame Transmission

• If the source address (SA) field is not present, the originator of the frame shall be assumed to be the PAN coordinator.

• If the destination address (DA) field is not present, the recipient of the frame shall be assumed to be the PAN coordinator.

• If both SA and DA addresses are present, the MAC shall compare the destination and source PAN identifiersdestination and source PAN identifiers– If the PAN identifiers are identical, the intra PAN subfield of

the frame control field shall be set to 1 and the source PAN identifier shall be omitted from the transmitted frame.

» Save bandwidth, only carry the destination PAN identifier– If the PAN identifiers are different, the intra PAN subfield of

the frame control field shall be set to 0 and both destination and source PAN identifier fields shall be included in the transmitted frame.


Frame reception and rejection

1. The frame typeframe type subfield shall not contain an illegal frame type.2. If the frame type indicates that the frame is a beacon framebeacon frame,

the source PAN identifiersource PAN identifier shall match macPANIdmacPANId unless macPANId is equal to 0xffff0xffff,, in which case the beacon frame shall be accepted regardless of the source PAN identifier.

3. If a destination PAN identifierdestination PAN identifier is included in the frame, it shall match macPANIdmacPANId or shall be the broadcast PAN identifier broadcast PAN identifier (0xffff)(0xffff).

4. If a short DAshort DA is included in the frame, it shall match either macShortAddressmacShortAddress or the broadcast address (0xffff)broadcast address (0xffff). Otherwise, it shall match aExtendedAddressaExtendedAddress.

5. If only SA fieldsonly SA fields are included in a data or MAC command frame, the frame shall only be accepted if the device is a PAN coordinator and the source PAN identifier matches macPANIdmacPANId.

Documents

IEEE 802.15.4 MAC and PHY Specifications for LR …read.pudn.com/downloads55/ebook/189875/IEEE802.15.4 MAC...TKU HSNL LR-WPAN - 1 IEEE 802.15.4 MAC and PHY Specifications for LR-WPANs