Post on 16-Oct-2021
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
W.wan.4-2
PANs: Bluetooth & 802.15
BluetoothOverviewPiconets & ScatternetsPHY layerMAC layerLogical Link ControlManagement
802.15 & othersEnd
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-3
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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W.wan.4-4
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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W.wan.4-5
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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W.wan.4-6
Bluetooth history
History and Hi-techThe name "Bluetooth" is taken from
the 10th century Danish King Harald Blatand - or Harold BluetoothBluetooth in English.
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-7
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).
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-8
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-9
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
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)
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-11
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-12
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-13
Bluetooth: protocol stack
RadioBaseband
Frequency hopping selectionConnection creation & managementMAC
Link managementPower managementSecurity management
LLC & adaptation protocol
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-14
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-15
Bluetooth PHY: radio
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-16
Bluetooth PHY: radio
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-17
Bluetooth PHY: radio
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-18
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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W.wan.4-19
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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W.wan.4-20
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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W.wan.4-21
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-22
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-23
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-24
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-25
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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W.wan.4-26
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-27
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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W.wan.4-28
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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W.wan.4-29
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-30
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
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Bluetooth MAC: low power
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-32
Bluetooth MAC: low power
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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W.wan.4-33
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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W.wan.4-34
PANs: Bluetooth & 802.15
BluetoothOverviewPiconets & ScatternetsPHY layerMAC layerLogical Link ControlManagement
802.15 & othersEnd
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-35
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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W.wan.4-36
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-37
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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W.wan.4-38
PANs: Bluetooth & 802.15
BluetoothOverviewPiconets & ScatternetsPHY layerMAC layerLogical Link ControlManagement
802.15 & othersEnd
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-39
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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W.wan.4-40
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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W.wan.4-41
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-42
PANs: Bluetooth & 802.15
BluetoothOverviewPiconets & ScatternetsPHY layerMAC layerLogical Link ControlManagement
802.15 & othersEnd
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-43
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
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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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-45
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-46
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
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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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W.wan.4-48
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
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-49
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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W.wan.4-50
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.
@ by Dr.Shu@UNM & Dr.Wu@SJTU
W.wan.4-51
PANs: Bluetooth & 802.15
BluetoothOverviewPiconets & ScatternetsPHY layerMAC layerLogical Link ControlManagement
802.15 & othersEnd