pans: bluetooth & 802.15 wireless lans & pans

Wireless LANs & PANsCase Study: Bluetooth & IEEE802.15

W.lan.4

Dr.M.Y.Wu@CSEShanghai Jiaotong University

Shanghai, China

Dr.W.Shu@ECEUniversity of New Mexico

Albuquerque, NM, USA

@ by Dr.Shu@UNM & Dr.Wu@SJTU

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PANs: Bluetooth & 802.15

BluetoothOverviewPiconets & ScatternetsPHY layerMAC layerLogical Link ControlManagement

802.15 & othersEnd


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PANs: Personal area networks

PAN = Networks that connect devices within a small range

Typically 10-100 meters

ApplicationsRealtime data and voice transmissionsCable replacement, get rid off net of wiresHook laptop, PDA, headphones,printer, cameraAd hoc networkingSensor networksRFIDs


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Bluetooth overviewOverview

Universal radio interface for ad-hoc wireless connectivityShort range (10 m), low power consumption, license-free 2.45 GHz ISM Interconnecting laptop, PDA, headphones,printer, camera, replacement of IrDA

Specifies the physical, link, and MAC layersApplications built on top of Bluebooth using HCI (Host Control Interface)


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Bluetooth history

History1994: Ericsson “MC-link” project1998: foundation of Bluetooth SIG, at www.bluetooth.org2001: spec. version 1.1 released2005: 5 million chips/week

SponsorsInitial: Ericsson, Nokia, IBM, Intel, ToshibaExpended in 1999: 3Com, Microsoft, Motorola, Agere (was: Lucent), More than 2500 members in SIG as adoptersCommon specification and certification of products


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Bluetooth history

History and Hi-techThe name "Bluetooth" is taken from

the 10th century Danish King Harald Blatand - or Harold BluetoothBluetooth in English.


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Bluetooth designDesign goals

Global operation on voice & dataNo fixed infrastructure required for network setupSmall, low-power, low-cost radio, embedded in devices,

goal: $5-10/node; in 2005: $50/USB bluetoothTopology

Overlapping piconets (stars) forming a scatternetMaster-slave connection

One of the first modules (Ericsson).


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Bluetooth architecture: piconetComponents

Master nodeOne per piconet

Slave nodeUp to 7 per piconet

Parked nodeConnected, but not actively participating, up to 256 per piconet, limited listening

Standby nodeNot connected, only native clock is running

M=MasterS=Slave

P=ParkedSB=Standby

MS

P

SB

S

S

P

P

SB


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Bluetooth architecture: piconet

Collection of devices connected in an ad hoc fashion

One unit acts as master and the others (max 7) as slaves

Each piconet has a unique hopping pattern

Master announce its clock & IDMaster determines hopping pattern (by its 48-bit device address)Slaves have to synchronize (Participation in)

M=MasterS=Slave

P=ParkedSB=Standby

MS

P

SB

S

S

P

P

SB


W.wan.4-10

Bluetooth architecture: scatternets

Scatternets: Linking of multiple co-located piconets through the sharing of common master or slave devicesCommunication between piconets

Devices jumping back and forth between the piconets

M=MasterS=SlaveP=ParkedSB=Standby

M

S

P

SB

S

S

P

P

SB

M

S

S

P

SB

Piconets(each with a capacity of 720 kbit/s)


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Bluetooth architecture: scatternets

Within a piconetEvery active members (master/slaves) share 1 MHz bandwidth

Among co-located piconetsThey can co-exist by hopping independentlyAggregately share 79 MHz bandwidth

Interconnect of co-located piconets scatternetsNodes can belong to multiple piconets by TDM

Can be a slave in two different piconetsCan be a master in one piconet and a slave in another piconetCannot be a master in two different piconets, since master defines a piconet

No standard for synchronize between piconetsInefficient use of resources, cause drop of connection


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Bluetooth protocol stack

PHYPHYBaseband

RAdio

Link Manager

ManagementApps

LinkLink

NetworkNetwork

AppApp

TransportTransport

Audio

Hos

t Co

ntro

l In

terf

ace

(HCI

)

Logical Link Control & Adaptation Protocol (L2CAP)

Serv

ice

Dis

cov

Prot

ocol

(SD

P)

AudioApps

RFCOMM (Serial Line Interface)PPPIP

TCP/UDP

InternetApps

TelephonyApps

vCardApps

AT Modem

interface


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Bluetooth: protocol stack

RadioBaseband

Frequency hopping selectionConnection creation & managementMAC

Link managementPower managementSecurity management

LLC & adaptation protocol


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Bluetooth PHY: radio

2.4 GHz ISM band (2402-2480)79 RF hopping channels 1 MHz carrier spacingGFSK modulationDevices within 10m can share up to 865 kbps (<1 mbps)Peak Tx power 20 dBm

FHSS/TDD/TDMAFrequency hopping, good protection against interferenceHopping sequence with 1600 hops/s in a pseudo random fashion, determined by a master, Time division duplex for send/receive separationLow cost, low power implementation


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All devices in a piconet hop togetherMaster gives slaves its clock and device ID

Hopping pattern: determined by device ID Phase in hopping pattern determined by clock

Channels79 1 MHz channels, each divided into 625 μs slots

1600 hops/s, hop occurs after each packet transmittedPackets can be 1, 3, or 5 slots in length

ClocksNative clock, 28-bit, ticks 3,200 times/s

312.5 μs, ½ length of hopping slot


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Transmitting packets in multiple slotsHop freq used for 1st slot will remain for othersFreq used with the following slots are catching back to the regular sequence

Sfk

625 µs

fk+1 fk+2 fk+3 fk+4

fk+3 fk+4fk

fk

fk+5

fk+5

fk+1 fk+6

fk+6

fk+6

MM M M

M

M M

M M

t

t

t

S S

S S

S


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TDD (Time Division Duplex)Transmit and receive in alternate time slotsMaster-slave architecture

Master transmits in an even-numbered slotSlave transmits in following odd-numbered slot

Traffic schedulingMaster polls slaves explicitly or implicitly

Sending a master-to-slave data/control packet

Master can adjust scheduling algorithm dynamicallyScheduling algorithms are not specified in Bluetooth standard


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Bluetooth PHY: radioLow power design

Transmission1 mW to reach 10m, to reach 100m, amplify signal to 100mWClass 1: greatest distance

Max 100mW (+20dBm), min 1mW, power control requiredClass 2:

Max 2.4mW (+4dBm), min .25mW, power control optionalClass 3: lowest power, 1mW

Active50-100mW active power

Voice mode, 8-30 mA, 75 hoursData mode, average 5 mA at 20 kbps, 120 hours

StandbyStandby current < 0.3 mA, 3 months


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Bluetooth MAC: link types

Voice link – SCO (Synchronous Connection Oriented)FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switchedPeriodic single slot packet assignmentMaster can support up to 3 SCO links at the same time

Data link – ACL (Asynchronous ConnectionLess)Asynchronous, fast acknowledge, point-to-multipoint, packet switchedVariable packet size (1,3,5 slots), asymmetric bandwidth

up to 433.9 kbps symm or 723.2/57.6 kbps asymmetricForward error detection (2/3 FEC) and retransmission


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Bluetooth MAC: link types

Achievable data rate on the ACL linkDMx = x-slot 2/3 FEC protected; DHx = x-slot unproteted

57.6721.0432.6DH536.3477.8286.7DM586.4576.0384.0DH354.4384.0256.0DM3172.8172.8172.8DH1108.8108.0 108.8DM1

Asymmetric(kbps)

Symmetric(kbps)

Type


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Baseband MAC: link types

Polling-based TDD packet transmission625µs slots, master polls slaves

SCO & ACL can co-exist

MA

STER

SLA

VE 1

SLA

VE 2

f6f0

f1 f7

f12

f13 f19

f18

SCO SCO SCO SCOACL

f5 f21

f4 f20

ACLACLf8

f9

f17

f14

ACL


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Bluetooth: baseband

Standby: do nothingInquire: search for other devicesPage: connect to a specific deviceConnected: participate in a piconet

Park: release AMA, get PMA Sniff: listen periodically, not each slotHold: stop ACL, SCO still possible, possibly participate in another piconet

standby

inquiry page

connectedAMA

transmitAMA

parkPMA

holdAMA

sniffAMA

unconnected

connecting

active

low power

detach


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Bluetooth: basebandAddressing

Logical addressActive Member Address (AM_ADDR, 3 bit)

Max 23 = 8 active membersParked Member Address (PM_ADDR, 8 bit)

Max 28 = 256 parked membersDevice address, 48-bit,

unique worldwide, is partitioned into 3 partsthe lower address part (LAP) is used in piconetID, error checking, security check, etc. the remaining two parts are proprietary address of the manufacture organizations


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Bluetooth: connection management

Initially, all the nodes in standby mode. Someone begins Inquiry/Page to form a new piconetInquiry, to collect information about nearby devices

Potential master:Inquiry: follow a known frequency hopping sequence (only 32 frequencies used with the fixed IAC (Inquiry Access Code)) to announce the master ID

Upon receipt of DAC, goto Page statePotential slaves:

Inquiry Scan: hopping at very slow speed for the same 32 frequenciesInquiry Response: upon receiving IAC, wait for a random time, then send DAC (Device Access Code) to request to join to the new piconet, goto Page Scan state


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Bluetooth: connection managementPage, to establish connection

Master to be:Page: adjust frequency and send a paging message to the slave to be to allow it join, with slave’s FHS known

Responded back in previous InquiryIn an existing piconet, the master helped two slaves to form a new piconet

Page Response: Upon receipt of a slave’s DAC, send page response message including CAC (Channel Access Code); Connection established

Slave to bePage scan: upon receipt of Paging message, respond back its DAC (Device Access Code)Waiting for CAC and then adjust clock to join piconet


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Bluetooth: basebandAccess code

derived from the masterThree types

CAC (Channel Access Code):Used to identify a piconet

DAC (Device Access Code)Used for paging & its subsequent response

IAC (Inquiry Access Code)Used for inquiry phase


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Bluetooth: baseband

Low-level packet definitionAccess code derived from the masterPacket header, 18-bit, with 1/3 FEC to have 54-bit

3-bit AM_ADDR (broadcast + 7 slaves), 4-bit packet type, 1-bit flow control, alternating bit ARQ/SEQ, 8-bit header-error-control

access code packet header payload68(72) 54 0-2745 bits

AM address type flow ARQN SEQN HEC3 4 1 1 1 8 bits

preamble sync. (trailer)

4 64 (4)


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Bluetooth MAC: packets

Packet formatsAccess Code, 48-bit, 2/3 FEC 72-bitPacket Header, 18-bit, 1/3 FEC 54-bitPayload, max 2745

Signaling (control) packetsID, Null, Poll, FHS, DM1,…

Data/voice packetsSCO: Voice

HV1, HV2, HV3, DV,…ACL: Data

DM1, DM2, DM3,…


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Bluetooth MAC: LMP

LMP (Link Management Protocol)Power managementSecurity management

Authentication on deviceChallenge-response mechanismBased on a commonly shared secret key

Generated by PIN (personal identification number)

Encryption on link


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Bluetooth MAC: low power

Power saving in an active stateReceiver can determine quickly if continued reception needed or not by correlating incoming packet with piconet access code

If not (takes 100μs), return to sleep for this receiving slot, as well as the following sending slot unless it’s masterIf yes, detect the destination slave address

If matched, continue receivingOtherwise, go back to sleep for this receiving slot, as well as the following sending slot

Low power states Park, Hold, Sniff


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HOLD mode Low power stateDevices connected but not participating

If no communication needed for some time, master can put slave in HOLD mode to allow a slave to

Goto sleepSwitch to another piconetPerform scanning, inquiry or paging

After Hold expires, slave returns to channelSCO: Synchronization remains during HOLD period, no ACL

SNIFF mode, similar to HOLD modeSlave can skip some receive slots to save powerMaster and slave agree on which slots slave will listen to channel


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PARK mode -- Low power stateMotivation

Low duty-cycle mode low powerHelp master to handle more than 7 slaves

Give up its AM_ADDR, obtain a 8-bit PM_ADDRSlave wakes up occasionally to resynchronize with master & check for broadcastingMaster establishes beacon channel

Enable parked slaves to remain synchronized to piconetAllow master to broadcast (dest addr: all 0s)

Slave cannot communication until unpacked


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Bluetooth: low power examplePower consumption in BlueCore 2: typical Average Current Consumption, with VDD=1.8V Temperature = 20°CActive Mode

SCO connection HV3 (1s interval Sniff Mode) (Slave) 26.0 mASCO connection HV3 (1s interval Sniff Mode) (Master) 26.0 mASCO connection HV1 (Slave) 53.0 mASCO connection HV1 (Master) 53.0 mAACL data transfer 115.2kbps UART (Master) 15.5 mAACL data transfer 720kbps USB (Slave) 53.0 mAACL data transfer 720kbps USB (Master) 53.0 mAACL connection, Sniff Mode 40ms interval, 38.4kbps UART 4.0 mAACL connection, Sniff Mode 1.28s interval, 38.4kbps UART 0.5 mA

Low power modeParked Slave, 1.28s beacon interval, 38.4kbps UART 0.6 mAStandby Mode (Connected to host, no RF activity) 47.0 µADeep Sleep Mode(2) 20.0 µA

Source: www.csr.com


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802.15 & othersEnd


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Bluetooth: L2CAP

L2CAP (Logical Link Control and Adaptation Protocol)Simple data link protocol on top of baseband

Connection orientedConnectionless, and Signaling channels

Protocol multiplexingRFCOMM, SDP, telephony control

Segmentation & reassemblyUp to 64kbyte user data, 16 bit CRC used from baseband

QoS flow specification per channelFollows RFC 1363, specifies delay, jitter, bursts, bandwidth

Group abstractionCreate/close group, add/remove member


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Bluetooth: L2CAP

baseband

L2CAP

baseband

L2CAP

baseband

L2CAP

Slave SlaveMaster

ACL

2 d 1 d d 1 1 d 21

signalling connectionless connection-oriented

d d d

Establish logical channels over baseband


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L2CAP packet formats

length2 bytes

CID=22

PSM≥2

payload0-65533

length2 bytes

CID2

payload0-65535

length2 bytes

CID=12

One or more commands

Connectionless PDU

Connection-oriented PDU

Signaling command PDU

code ID length data1 1 2 ≥0

L2CAP packet formatsCID=1, signalCID=2, ACLCID, SCO


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802.15 & othersEnd


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Bluetooth: SDP

SDP (Service Discovery Protocol)Inquiry/response protocol for discovering services

Searching for and browsing services in radio proximityAdapted to the highly dynamic environmentCan be complemented by others like SLP, Jini, Salutation, …Defines discovery only, not the usage of servicesCaching of discovered servicesGradual discovery

Service record formatInformation about services provided by attributesAttributes are composed of an 16 bit ID (name) and a valuevalues may be derived from 128 bit Universally Unique Identifiers (UUID)


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Bluetooth: apps support

RFCOMMEmulation of a serial port (supports a large base of legacy applications)Allows multiple ports over a single physical channel

Telephony Control Protocol Specification (TCS)Call control (setup, release)Group management

OBEXExchange of objects, IrDA replacement

WAPInteracting with applications on cellular phones


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Bluetooth: profilesRepresent default solutions for a certain usage model

Vertical slice through the protocol stackBasis for interoperability

13 profiles group into 4 categories:Generic profiles:

Generic Access SDP

Telephony profilesCordless, Intercom Headset Profile

Networking profilesLAN, FAX, dialup

Serial profilesSerial port, USB

ProfilesP

roto

cols

Applications


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802.15 & othersEnd


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WPAN: IEEE 802.15802.15-2: Coexistance

Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference

802.15-3: High-RateStandard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost Data Rates: 11, 22, 33, 44, 55 Mbit/sQoS isochronous protocol Ad hoc peer-to-peer networking Security Designed to meet the demanding requirements of portable consumer imaging and multimedia applications


W.wan.4-44

WPAN: IEEE 802.15

Several working groups extend the 802.15.3 standard

802.15.3a:Alternative PHY with higher data rate as extension to 802.15.3Applications: multimedia, picture transmission

802.15.3b:Enhanced interoperability of MACCorrection of errors and ambiguities in the standard

802.15.3c:Alternative PHY at 57-64 GHzGoal: data rates above 2 Gbps


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WPAN: IEEE 802.15 & ZigBee802.15-4: Low-Rate, Very Low-Power

Low data rate solution with multi-month to multi-year battery life and very low complexityPotential applications are sensors, interactive toys, smart badges, remote controls, and home automationData rates of 20-250 kbit/s, latency down to 15 msMaster-Slave or Peer-to-Peer operationUp to 254 devices or 64516 simpler nodesSupport for critical latency devices, such as joysticks16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band


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ZigBee

Relation to 802.15.4 similar to Bluetooth / 802.15.1Pushed by Chipcon, ember, freescale (Motorola), Honeywell, Mitsubishi, Motorola, Philips, SamsungMore than 150 members

Promoter (40000$/Jahr), Participant (9500$/Jahr), Adopter (3500$/Jahr)

No free access to the specifications (only promoters and participants)ZigBee platforms comprise

IEEE 802.15.4 for layers 1 and 2ZigBee protocol stack up to the applications


W.wan.4-47

WPAN: IEEE 802.15.4

802.15.4a:Alternative PHY with lower data rate as extension to 802.15.4Properties: precise localization (< 1m precision), extremely lowpower consumption, longer rangeTwo PHY alternatives

UWB (Ultra Wideband): ultra short pulses, communication and localizationCSS (Chirp Spread Spectrum): communication only

802.15.4b:Extensions, corrections, and clarifications regarding 802.15.4Usage of new bands, more flexible security mechanisms

802.15.5: Mesh NetworkingPartial meshes, full meshesRange extension, more robustness, longer battery live


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Other IEEE802.xx

IEEE 802.16: Broadband Wireless Access/ WirelessMAN/WiMax

Wireless distribution system, e.g., for the last mile, alternative to DSL75 Mbit/s up to 50 km LOS, up to 10 km NLOS; 2-66 GHz bandInitial standards without roaming or mobility support802.16e adds mobility support, allows for roaming at 150 km/h

Unclear relation to 802.20, 802.16 started as fixed system…IEEE 802.20: Mobile Broadband Wireless Access (MBWA)

Licensed bands < 3.5 GHz, optimized for IP trafficPeak rate > 1 Mbit/s per userDifferent mobility classes up to 250 km/h and ranges up to 15 km

IEEE 802.22: Wireless Regional Area Networks (WRAN)Radio-based PHY/MAC for use by license-exempt devices on a non-interfering basis in spectrum that is allocated to the TV Broadcast Service


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Bluetooth may act like a rogue member of the 802.11 networkDoes not know anything about gaps, inter frame spacing etc.

IEEE 802.15-2 discusses these problemsProposal: Adaptive Frequency Hopping

a non-collaborative Coexistence MechanismReal effects? Many different opinions, publications, tests, formulae, …

Results from complete breakdown to almost no effectBluetooth (FHSS) seems more robust than 802.11b (DSSS)

802.11 vs. 802.15/Bluetooth

t

f [MHz]

2402

2480 802.11b 3 channels(separated by installation)

AC

K

DIF

S

DIF

S

SIF

S

1000 byte

SIF

S

DIF

S

500 byte AC

K

DIF

S

500 byteS

IFS

AC

K

DIF

S

500 byte

DIF

S 100byte S

IFS

AC

K

DIF

S 100byte S

IFS

AC

K

DIF

S 100byte S

IFS

AC

K

DIF

S 100byte S

IFS

AC

K

DIF

S 100byte S

IFS

AC

K

802.15.1 79 channels(separated by hopping pattern)


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Readings

TextbooksC. S. Ram Murthy & B. S. Manoj, “Ad Hoc Wireless

Networks”, Chapter 2.5, Bluetooth, pages 88-98.W. Stallings, “Wireless Communications & Networks”,

Chapter 15, Bluetooth and IEEE 802.15, pages 463-510.


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802.15 & othersEnd

pans: bluetooth & 802.15 wireless lans & pans

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