lecture 14
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1
No or bad connection? Then perform: Scanning : scan the environment, i.e., listen into the medium for beacon
signals Passive scan : listen to the beacons send by other stations and choose a stn based on
power levels. Active scan : or send probes into the medium and wait for an answer
Reassociation Request station sends a request to one or several AP(s)
Reassociation Response success: AP has answered, station can now participate failure: continue scanning
AP accepts Reassociation Request signal the new station to the distribution system the distribution system updates its data base (i.e., location information) typically, the distribution system now informs the old AP so it can release
resources
Roaming
2
IEEE 802.11b
Just after the introduction of the IEEE802.11 standard, a few companies started some enhancements to achieve 11 Mbps data rates. To avoid market segmentation, a new standard
IEEE 802.11b emerged.
The change is mainly in the physical layer. This is a more3 successful standard as regards the industry adaptation.
3
WLAN: IEEE 802.11b
Data rate 1, 2, 5.5, 11 Mbit/s, depending
on SNR User data rate max. approx. 6
Mbit/s Transmission range
300m outdoor, 30m indoor Max. data rate ~10m indoor
Frequency Free 2.4 GHz ISM-band
Security Limited, WEP insecure, SSID
Availability Many products, many vendors
Connection set-up time Connectionless/always on
Quality of Service Typ. Best effort, no guarantees
(unless polling is used, limited support in products)
Manageability Limited (no automated key
distribution, sym. Encryption) Special Advantages/Disadvantages
Advantage: many installed systems, lot of experience, available worldwide, free ISM-band, many vendors, integrated in laptops, simple system
Disadvantage: heavy interference on ISM-band, no service guarantees, slow relative speed only
4
802.11b…Commercially …..on Lap Tops
5
IEEE 802.11b – PHY frame formats
synchronization SFD signal service HEC payload
PLCP preamble PLCP header
128 16 8 8 16 variable bits
length
16
192 µs at 1 Mbit/s DBPSK 1, 2, 5.5 or 11 Mbit/s
short synch. SFD signal service HEC payload
PLCP preamble(1 Mbit/s, DBPSK)
PLCP header(2 Mbit/s, DQPSK)
56 16 8 8 16 variable bits
length
16
96 µs 2, 5.5 or 11 Mbit/s
Long PLCP PPDU format: mandatory
Short PLCP PPDU format (optional)
@@Physical Layer Convergence Protocol
Difference : Rate encoded; hex code for 1, 2, 5.5, 11 Mbps
6
Channel selection (non-overlapping)
2400
[MHz]
2412 2483.52442 2472
channel 1 channel 7 channel 13
Europe (ETSI)
US (FCC)/Canada (IC)
2400
[MHz]
2412 2483.52437 2462
channel 1 channel 6 channel 11
22 MHz
22 MHz
Depending on national restrictions, a max of 14 channels can be used. Center freq. To be displaced by 25 MHz.
7
WLAN: IEEE 802.11a Data rate
6, 9, 12, 18, 24, 36, 48, 54 Mbit/s, depending on SNR
User throughput (1500 byte packets): 5.3 (6), 18 (24), 24 (36), 32 (54)
6, 12, 24 Mbit/s mandatory Transmission range
100m outdoor, 10m indoor E.g., 54 Mbit/s up to 5 m, 48 up to
12 m, 36 up to 25 m, 24 up to 30m, 18 up to 40 m, 12 up to 60 m
Frequency Free 5.15-5.25, 5.25-5.35, 5.725-
5.825 GHz ISM-band Requires carrier sense every 4
ms to avoid interference Security
Limited, WEP insecure, SSID Availability
Some products, some vendors
Connection set-up time Connectionless/always on
Quality of Service Typ. best effort, no guarantees
(same as all 802.11 products) Manageability
Limited (no automated key distribution, sym. Encryption)
Special Advantages/Disadvantages Advantage: fits into 802.x
standards, free ISM-band, available, simple system, uses less crowded 5 GHz band
Disadvantage: stronger shading due to higher frequency, no QoS
8
WLAN: IEEE 802.11a
To achieve upto 54 Mbps, it uses technologies such as BPSK, QPSK, 16-QAM or 64 QAM.
To minimize transmission errors, PEC is used with coding rates of 1/2, 2/3 or 3/4.
9
IEEE 802.11a – PHY frame format
rate service payload
variable bits
6 Mbit/s
PLCP preamble signal data
symbols12 1 variable
reserved length tailparity tail pad
616611214 variable
6, 9, 12, 18, 24, 36, 48, 54 Mbit/s
PLCP header
10
Frame format
PCLP Preamble (Physical Layer Convergence Protocol)
- 12 symbols and used for freq acquisition, channel estimation, synchronization).- 16 micro secs.
Signal(made of rate – 0x3 for 54 Mbps, 0x9 for 24 Mbps etc,
length : no. of bytes in payload, parity for parity check).
DATA
- service field (to synchronize the descrambler- data scrambled using the poly x7 + x4 + 1)
- payload contains MAC PDU
- tail : used to reset the encoder
- pad : ensures that the no. of bits in PDU maps to an integer no. of OFDM symbols.
11
Operating channels for 802.11a / US U-NII
5150 [MHz]5180 53505200
36 44
16.6 MHz
center frequency = 5000 + 5*channel number [MHz]
channel40 48 52 56 60 64
149 153 157 161
5220 5240 5260 5280 5300 5320
5725 [MHz]5745 58255765
16.6 MHz
channel
5785 5805
12
Operating channels for 802.11a / US U-NII
Provides a unique numbering of channels with 5 MHz spacing starting from 5 GHz.
Eight channels defined in the lower two bands (Indoor use)
- 36, 40, 44, 48, 52, 56, 60, 64 Four more channels in the High band (for out door as well as
indoor use)
- 149, 153, 157, 161 Channels spacing is 20MHz.
13
OFDM in IEEE 802.11a (and HiperLAN2)
subcarriernumber
1 7 21 26-26 -21 -7 -1
channel center frequency
312.5 kHzpilot
OFDM with 52 used subcarriers (64 in total) 48 data + 4 pilot (plus 12 virtual subcarriers) 312.5 kHz spacing
Each channel occupies : 312.5 * 52 + centre freq. = approx. 16.6 MHz.
14
Distinctions
IEEE 802.11b IEEE 802.11a2.4 GHz 5 GHz
Data rates up to 11 Mbps Data rates up to 54 Mbps - Depending on SNR,
signal conditions and
distance b/w sender and
receiver, data rates may
drop.
- MAC layer adds
overheads
5.3(6), 18(24), 24(36), 32(54)
15
OFDM in IEEE 802.11a (and HiperLAN2)
The 52 sub-carriers are equally spaced around the centre frequency.
Spacing between sub-carriers is 312.5 kHz. 26 sub-carriers are to the left and 26 are to the right of
the centre frequency. The sub-carriers -21, -7, 7, 21 are used as pilot signals
to enable signal detection robust against frequency offsets.
16
WLAN: IEEE 802.11 – future developments (03/2005)
802.11c: Bridge Support Definition of MAC procedures to support bridges as extension to 802.1D
802.11d: Regulatory Domain Update Support of additional regulations related to channel selection, hopping sequences
802.11e: MAC Enhancements – QoS Enhance the current 802.11 MAC to expand support for applications with Quality of
Service requirements, and in the capabilities and efficiency of the protocol Definition of a data flow (“connection”) with parameters like rate, burst, period… Additional energy saving mechanisms and more efficient retransmission
802.11f: Inter-Access Point Protocol Establish an Inter-Access Point Protocol for data exchange via the distribution
system Currently unclear to which extend manufacturers will follow this suggestion
802.11g: Data Rates > 20 Mbit/s at 2.4 GHz; 54 Mbit/s, OFDM Successful successor of 802.11b, performance loss during mixed operation with 11b
802.11h: Spectrum Managed 802.11a Extension for operation of 802.11a in Europe by mechanisms like channel
measurement for dynamic channel selection (DFS, Dynamic Frequency Selection) and power control (TPC, Transmit Power Control)
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WLAN: IEEE 802.11– future developments (03/2005)
802.11i: Enhanced Security Mechanisms Enhance the current 802.11 MAC to provide improvements in security. TKIP enhances the insecure WEP, but remains compatible to older WEP systems AES provides a secure encryption method and is based on new hardware
802.11j: Extensions for operations in Japan Changes of 802.11a for operation at 5GHz in Japan using only half the channel width at
larger range 802.11k: Methods for channel measurements
Devices and access points should be able to estimate channel quality in order to be able to choose a better access point of channel
802.11m: Updates of the 802.11 standards 802.11n: Higher data rates above 100Mbit/s
Changes of PHY and MAC with the goal of 100Mbit/s at MAC SAP MIMO antennas (Multiple Input Multiple Output), up to 600Mbit/s are currently feasible However, still a large overhead due to protocol headers and inefficient mechanisms
802.11p: Inter car communications Communication between cars/road side and cars/cars Planned for relative speeds of min. 200km/h and ranges over 1000m Usage of 5.850-5.925GHz band in North America
18
WLAN: IEEE 802.11– future developments (03/2005)
802.11r: Faster Handover between BSS Secure, fast handover of a station from one AP to another within an ESS Current mechanisms (even newer standards like 802.11i) plus incompatible devices from different
vendors are massive problems for the use of, e.g., VoIP in WLANs Handover should be feasible within 50ms in order to support multimedia applications efficiently
802.11s: Mesh Networking Design of a self-configuring Wireless Distribution System (WDS) based on 802.11 Support of point-to-point and broadcast communication across several hops
802.11t: Performance evaluation of 802.11 networks Standardization of performance measurement schemes
802.11u: Interworking with additional external networks 802.11v: Network management
Extensions of current management functions, channel measurements Definition of a unified interface
802.11w: Securing of network control Classical standards like 802.11, but also 802.11i protect only data frames, not the control frames. Thus,
this standard should extend 802.11i in a way that, e.g., no control frames can be forged.
Note: Not all “standards” will end in products, many ideas get stuck at working group level Info: www.ieee802.org/11/, 802wirelessworld.com, standards.ieee.org/getieee802/
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ETSI – HIPERLAN (historical)
ETSI standard European standard, cf. GSM, DECT, ... Enhancement of local Networks and interworking
with fixed networks integration of time-sensitive services from the early
beginning HIPERLAN family
one standard cannot satisfy all requirements range, bandwidth, QoS support commercial constraints
HIPERLAN 1 standardized since 1996 – no products!
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Overview: original HIPERLAN protocol family
HIPERLAN 1 HIPERLAN 2 HIPERLAN 3 HIPERLAN 4
Application wireless LAN access to ATMfixed networks
wireless localloop
point-to-pointwireless ATMconnections
Frequency 5.1-5.3GHz 17.2-17.3GHz
Topology decentralized ad-hoc/infrastructure
cellular,centralized
point-to-multipoint
point-to-point
Antenna omni-directional directionalRange 50 m 50-100 m 5000 m 150 mQoS statistical ATM traffic classes (VBR, CBR, ABR, UBR)Mobility <10m/s stationaryInterface conventional LAN ATM networks
Data rate 23.5 Mbit/s >20 Mbit/s 155 Mbit/sPowerconservation
yes not necessary
HIPERLAN 1 never reached product status, the other standards have been renamed/modfied !
21
HIPERLAN 1 - Characteristics
Data transmission point-to-point, point-to-multipoint, connectionless 23.5 Mbit/s, 1 W power, 2383 byte max. packet size
Services asynchronous and time-bounded services with hierarchical
priorities compatible with ISO MAC
Topology infrastructure or ad-hoc networks transmission range can be larger then coverage of a single node
(„forwarding“ integrated in mobile terminals) Further mechanisms
power saving, encryption, checksums
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Highlights of Hyperlan-1
Ability to transfer packets using several relays Supports p-savers. A node sets up specific wake-up
patterns Need p-supporters that contain info about wake-up
times P-supporters (forwarding entities) need buffering
mechanisms.
23
HIPERLAN 1 - Physical layer
Scope modulation, demodulation, bit and frame synchronization forward error correction mechanisms measurements of signal strength channel sensing
Channels 3 mandatory and 2 optional channels (with their carrier frequencies) mandatory
channel 0: 5.1764680 GHz channel 1: 5.1999974 GHz channel 2: 5.2235268 GHz
optional channel 3: 5.2470562 GHz channel 4: 5.2705856 GHz
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HIPERLAN 1 - Physical layer frames
Maintaining a high data-rate (23.5 Mbit/s) is power consuming - problematic for mobile terminals packet header with low bit-rate comprising receiver information only receiver(s) address by a packet continue receiving
Frame structure LBR (Low Bit-Rate) header with 1.4 Mbit/s 450 bit synchronization minimum 1, maximum 47 frames with 496 bit each for higher velocities of the mobile terminal (> 1.4 m/s) the maximum
number of frames has to be reduced
Modulation GMSK for high bit-rate, FSK for LBR header
LBR synchronization data0 data1 datam-1. . .
HBR
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HIPERLAN 1- MAC
EY-NPMA : Elimination yield, non-preemptive, multiple-access: Divides the medium access of competing nodes into three phases:
(i) Prioritization : highest priority of data packet ready to be sent
(ii) Contention : Eliminate all but one contender
(iii) Transmission : Finally, transmit the packet of the remaining node.
26
HIPERLAN 1 - CAC sublayer
Channel Access Control (CAC) assure that terminal does not access forbidden channels priority scheme, access with EY-NPMA
Priorities 5 priority levels for QoS support QoS is mapped onto a priority level with the help of the packet
lifetime (set by an application) if packet lifetime = 0 it makes no sense to forward the packet to
the receiver any longer standard start value 500ms, maximum 16000ms if a terminal cannot send the packet due to its current priority,
waiting time is permanently subtracted from lifetime based on packet lifetime, waiting time in a sender and number of
hops to the receiver, the packet is assigned to one out of five priorities
the priority of waiting packets, therefore, rises automatically
27
HIPERLAN 1 - EY-NPMA I
EY-NPMA (Elimination Yield Non-preemptive Priority Multiple Access) 3 phases: priority resolution, contention resolution, transmission finding the highest priority
every priority corresponds to a time-slot to send in the first phase, the higher the priority the earlier the time-slot to send
higher priorities can not be preempted if an earlier time-slot for a higher priority remains empty, stations with the next
lower priority might send after this first phase the highest current priority has been determined
prioritization contention transmissiontransmission
sync
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prio
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dete
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prio
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asse
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t
user
dat
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elim
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burs
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surv
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yiel
d lis
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ng
IYSIPS IPA IES IESV
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HIPERLAN 1 - EY-NPMA II
Several terminals can now have the same priority and wish to send contention phase
Elimination Burst: all remaining terminals send a burst to eliminate contenders (11111010100010011100000110010110, high bit- rate)
Elimination Survival Verification: contenders now sense the channel, if the channel is free they can continue, otherwise they have been eliminated
Yield Listening: contenders again listen in slots with a nonzero probability, if the terminal senses its slot idle it is free to transmit at the end of the contention phase
the important part is now to set the parameters for burst duration and channel sensing (slot-based, exponentially distributed)
data transmission the winner can now send its data (however, a small chance of collision remains) if the channel was idle for a longer time (min. for a duration of 1700 bit) a terminal
can send at once without using EY-NPMA synchronization using the last data transmission
29
WATM services
Office environment multimedia conferencing, online multimedia database access
Universities, schools, training centers distance learning, teaching
Industry database connection, surveillance, real-time factory management
Hospitals reliable, high-bandwidth network, medical images, remote monitoring
Home high-bandwidth interconnect of devices (TV, CD, PC, ...)
Networked vehicles trucks, aircraft etc. interconnect, platooning, intelligent roads
30
Modication for Wireless ATM : WATM
Seamless integration of wireless terminals to ATM network Mobility is needed for ATM support networks in local and global
situations. ATM should have a wireless extension. Other wireless services offer best effort services and at tiles, time
bounded services; WATM offers QoS to the level of ATM networks.
31
WATM components
WMT (Wireless Mobile ATM Terminal) RAS (Radio Access System) EMAS-E (End-user Mobility-supporting ATM Switch - Edge) EMAS-N (End-user Mobility-supporting ATM Switch - Network) M-NNI (Network-to-Network Interface with Mobility support) LS (Location Server) AUS (Authentication Server)
32
Reference model
WMT
WMT
EMAS-E
EMAS-N
EMAS-N
M-NNI
RAS
RAS
LSAUS
33
User plane protocol layers
WATMterminaladapter
MATMtermi-
nalRAS
EMAS-E
EMAS-N
ATM-Switch
fixedend
system
radio segment fixed network segment
34
Reference model with further access scenarios I
1: wireless ad-hoc ATM network2: wireless mobile ATM terminals3: mobile ATM terminals4: mobile ATM switches5: fixed ATM terminals6: fixed wireless ATM terminals
WMT: wireless mobile terminal WT: wireless terminal MT: mobile terminal T: terminal AP: access point EMAS: end-user mobility supporting ATM switch (-E: edge, -N: network) NMAS: network mobility supporting ATM switch MS: mobile ATM switch
35
Reference model with further access scenarios II
RAS ACT WMT
WMT
NMAS
RAS
RASMS
T
EMAS-EMT
WTRAS
EMAS-N TRAS
EMAS-EWMT
1
2
3
4
5
6
36
BRAN – Broadband Radio Access Networks
Motivation deregulation, privatization, new companies, new services How to reach the customer?
alternatives: xDSL, cable, satellite, radio Radio access
flexible (supports traffic mix, multiplexing for higher efficiency, can be asymmetrical)
quick installation economic (incremental growth possible)
Market private customers (Internet access, tele-xy...) small and medium sized business (Internet, MM conferencing, VPN)
Scope of standardization access networks, indoor/campus mobility, 25-155 Mbit/s, 50 m-5 km coordination with ATM Forum, IETF, ETSI, IEEE, ....
37
Broadband network types
Common characteristics ATM QoS (CBR, VBR, UBR, ABR)
HIPERLAN/2 short range (< 200 m), indoor/campus, 25 Mbit/s user data rate access to telecommunication systems, multimedia applications,
mobility (<10 m/s) HIPERACCESS
wider range (< 5 km), outdoor, 25 Mbit/s user data rate fixed radio links to customers (“last mile”), alternative to xDSL or
cable modem, quick installation Several (proprietary) products exist with 155 Mbit/s plus QoS
HIPERLINK – currently no activities intermediate link, 155 Mbit/s connection of HIPERLAN access points or connection between
HIPERACCESS nodes
38
BRAN and legacy networks
core networkATM
core networkIP
network convergence sublayer
BRAN data link control
BRAN PHY-1 BRAN PHY-2 ...
Coordination IETF (TCP/IP) ATM forum (ATM) ETSI (UMTS) CEPT, ITU-R, ... (radio frequencies)
IndependenceBRAN as access network independent from the fixed networkInterworking of TCP/IP and ATM under study
Layered modelNetwork Convergence Sub-layer as superset of all requirements for IP and ATM
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HiperLAN2 (historical)
Official name: BRAN HIPERLAN Type 2 H/2, HIPERLAN/2 also used
High data rates for users More efficient than 802.11a
Connection oriented QoS support Dynamic frequency selection Security support
Strong encryption/authentication Mobility support Network and application independent
convergence layers for Ethernet, IEEE 1394, ATM, 3G Power save modes Plug and Play
40
HiperLAN2 architecture and handover scenarios
2
3
1
AP
APT APC CoreNetwork
(Ethernet,Firewire,
ATM,UMTS)APT
APT
APC
AP
MT4
MT3
MT2
MT1
Access Point Transceiver
Access Point controller
41
Centralized vs. direct mode
MT1
AP/CCAP
MT2
data
control control
MT1 MT2
data
control
Centralized Direct
MT1 MT2 +CCdata
control
42
HiperLAN2 protocol stack
Higher layers
Convergence layer
Data link control - basic data
transport functionScope of HiperLAN2standards
DLC controlSAP
DLC userSAP
Radio link control sublayer
Physical layer
Radioresourcecontrol
Assoc.control
DLCconn.
controlError
controlRadio link control
Medium access control
SAP : Service Access Point
43
Physical layer reference configuration
scrambling FEC coding interleaving
mapping OFDMPHY bursts
(PPDU)
PDU train from DLC(PSDU)
radiotransmitter
PDU : protocol Data Units
44
Operating channels of HiperLAN2 in Europe
5150 [MHz]5180 53505200
36 44
16.6 MHz
center frequency = 5000 + 5*channel number [MHz]
channel40 48 52 56 60 64
5220 5240 5260 5280 5300 5320
5470
[MHz]
5500 57255520
100 108
16.6 MHz
channel104 112 116 120 124 128
5540 5560 5580 5600 5620 5640
132 136 140
5660 5680 5700
45
Basic structure of HiperLAN2 MAC frames
MAC frame MAC frame MAC frame MAC frame
2 ms 2 ms 2 ms 2 ms
broadcast phase downlink phase uplink phaserandom
access phase
. . .
TDD, 500 OFDMsymbolsper frame
variable variable variable
LCH PDU typesequencenumber
payload CRC UDCH transfer syntax(long PDU)
54 byte
2 10 396 24 bit
LCH PDU type payload CRC
2 406 24
LCH transfer syntax
bit
46
Valid configurations of HiperLAN2 MAC frames
MAC frame MAC frame MAC frame MAC frame
2 ms 2 ms 2 ms 2 ms
BCH FCH ACH DL phase DiL phase UL phase RCHs
. . .
BCH FCH ACH DiL phase UL phase RCHs
BCH FCH ACH DL phase UL phase RCHs
BCH FCH ACH UL phase RCHs
BCH FCH ACH DL phase DiL phase RCHs
BCH FCH ACH DiL phase RCHs
BCH FCH ACH DL phase RCHs
BCH FCH ACH RCHs
Validcombinationsof MAC framesfor a single sector AP
broadcast downlink uplink
randomaccess
BCH : Broadcast Channel
FCH : Frame Channel
ACH : Association Control Function
RCH : Random Channel
47
Mapping of logical and transport channels
BCCH FCCH RFCH LCCH RBCH DCCH UDCH UBCH UMCH
BCH FCH ACH SCH LCH
downlink
UDCH DCCH LCCH ASCH
SCHLCH RCH
uplink
UDCH UBCH UMCH
LCH
DCCH RBCH
SCH
LCCH
direct link
48
Blue Tooth
Idea – Universal radio interface for ad-hoc wireless connectivity – Interconnecting computer and peripherals, handheld devices,
PDAs, cell phones – replacement of IrDA – Embedded in other devices, goal: 5€/device (2002: 50€/USB
bluetooth) – Short range (10 m), low power consumption, license-free 2.45
GHz ISM – Voice and data transmission, approx. 1 Mbit/s gross data rate One of the first modules (Ericsson)
49
Blue Tooth
50
Blue Tooth
51
Characteristics
2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing Channel 0: 2402 MHz … channel 78: 2480 MHz G-FSK modulation, 1-100 mW transmit power
FHSS and TDD Frequency hopping with 1600 hops/s Hopping sequence in a pseudo random fashion, determined by a
master Time division duplex for send/receive separation
Voice link – SCO (Synchronous Connection Oriented) FEC (forward error correction), no retransmission, 64 kbit/s duplex,
point-to-point, circuit switched Data link – ACL (Asynchronous ConnectionLess)
Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched
Topology Overlapping piconets (stars) forming a scatternet
52
Piconet
53
Piconet
Parked Devices : Have no connection with the network. But are known to the network and can be activated in milli seconds. If a parked device has to participate, one slave has to go to parked mode
and the slave can enter the network.
Devices in Standby do not participate in the network.
All devices adjust their clock w.r.t the master.
54
Piconet
All Active devices are assigned a 3-bit AMA (Active Member Address)
All parked devices are assigned a 8-bit PMA(Parked Member Address)
Standby Devices do not need an address.
55
History
– 1994: Ericsson (Mattison/Haartsen), “MC-link” project – Renaming of the project: Bluetooth according to Harald
“Blåtand” Gormsen [son of Gorm], King of Denmark in the 10th century
– 1998: foundation of Bluetooth SIG, www.bluetooth.org – 2001: first consumer products for mass market, spec. version
1.1 released • Special Interest Group – Original founding members: Ericsson, Intel, IBM, Nokia,
Toshiba – Added promoters: 3Com, Agere (was: Lucent), Microsoft,
Motorola – > 2500 members – Common specification and certification of products
56
Characteristics
2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing– Channel 0: 2402 MHz … channel 78: 2480 MHz– G-FSK modulation, 1-100 mW transmit power• FHSS and TDD– Frequency hopping with 1600 hops/s– Hopping sequence in a pseudo random fashion, determined by a master– Time division duplex for send/receive separation• Voice link – SCO (Synchronous Connection Oriented)– FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point,circuit switched• Data link – ACL (Asynchronous ConnectionLess)– Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric or723.2/57.6 kbit/s asymmetric, packet switched• Topology– Overlapping piconets (stars) forming a scatternet
57
User Scenarios
Connection to Peripheral Devices PC connections namely Keyboard, mouse, Joystick, speakers etc can be
linked in a wireless manner using bluetooth.
Support fro Adhoc Networking Several Devices (lap tops, PDA’s etc can talk to each other)
Bridging Networks A Mobile phone can act as a bridge between a local Piconet and a Global GSM
(and other global networks)
58
Piconet
59
Forming a Piconet
60
61
Scatternet
62
Scatternet
If a device wants to participate in a Piconet, it has to Sync with the hopping sequence of that Piconet.
Bluetooth applies FH-CDMA to separate the piconets. Adding Piconets increases collision. If the hopping sequences are not properly coordinated, two
devices may use the same frequency and so collisions may occur.
If a slave wants to participate in another piconet, it informs the current master that it will be unavailable for a certain duration.
When a Master leaves the piconet to participate as a slave for anothet piconet, all activities in this piconet are suspended till it returns.
Two devices can not be masters for two piconets since the common hopping sequence is not possible.
63
Scatternet
What happens to a device that moves to another piconet? Once a slave is attached to another piconet, it no more
participates in the formet piconet. Before leaving the piconet, it informs the former that it wants to
join the new piconet for a specific duration. If a device shunts back and forth between piconets,
communication(asynchronous) between piconets can be established.
64
Bluetooth protocol stack
65
Bluetooth layers in a nutshell
Radio : Specifications for frequencies, modulation and transmit power. Packet format, timing and QoS parameters
Link Manager : Link management between devices Security functions
Service Discovery Protocol (SDP) Querying of service characteristics Device discovery
RFCPM Cable Replacement Protocol Emulates replacement of cables in serial devices (management of legacy devices working on serial ports)
66
Bluetooth layers in a nutshell
Telephony Control Protocol Specs (TCS-BIN) Call Control Signaling Mechanism for voice and data between Bluetooth devices
Host Controller Interface (HCI) Command Interface between baseband and L2CAP Provides access to the HW status and registers
Bluetooth network Encapsulation Protocol (BNEP) More efficient than TCP/IP for networking applications
AT Modems For conventional telephone applications
Calender & Business Card(vCalendar /vCard) Can be exchanged using Object Exchange Protocol (OBEX)
Audio Application Use Baseband Layer directly after encoding audio signals
67
RADIO
License-Free 2.4 GHz bandwidth FH /Time Division Duplex used for transmission Hopping Rate : 1600 hops/sec
Bluetooth Receivers use GFSK for modulation and are available in three classes:
Class 1: Max Power of 100 mW and min power of 1 mW. (100 m range without obstacles) – power control mandatory
Class 2 : Max Power 2.5 mA and min power 0.25mW (10m range without obstacles) – Power control optional
Class 3: Max Power is 1 mW
68
Baseband Layer
Determines frequency hopping and also packet formats. Master sends a data fk, Slave answers at fk+1. The upper portion of the figure shows a 1-slot packets as the data
uses 625 micro secs- slot. A device may use a 3-slot or 5-slot transmission for larger size
packets But it reverts back to 1-slot transmission(as defined by the
hopping sequence) for the next Master/Slave transmission.
69
Frequency Selection during Transmission
S
fk
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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Baseband Piconet/channel definition Low-level packet definition
Access code Channel, device access, e.g., derived from master
Packet header 1/3-FEC, active member address (broadcast + 7 slaves), link
type, alternating bit ARQ/SEQ, checksum
access code packet header payload
68(72) 54 0-2745 bits
AM address type flow ARQN SEQN HEC
3 4 1 1 1 8 bits
preamble sync. (trailer)
4 64 (4)
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Baseband
Access Code: Needed for timing synchronization and piconet identification
Packet Header : Contains address, packet type, flow & Error control, Checksum
3-bit active address will specify address of the slave If Master sends the address, it is the receiver address If a slave sends the address, it is the sender address 0-value represents the broadcast type of data.
Flow : If Flow=0, transmission must stop If flow=1, transmission must resume
72
SCO payload types (Synchronous Connection Oriented)
payload (30)
audio (30)
audio (10)
audio (10)
HV3
HV2
HV1
DV
FEC (20)
audio (20) FEC (10)
header (1) payload (0-9) 2/3 FEC CRC (2)
(bytes)
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ACL Payload types (ex., web traffic)
payload (0-343)
header (1/2) payload (0-339) CRC (2)
header (1) payload (0-17) 2/3 FEC
header (1) payload (0-27)
header (2) payload (0-121) 2/3 FEC
header (2) payload (0-183)
header (2) payload (0-224) 2/3 FEC
header (2) payload (0-339)DH5
DM5
DH3
DM3
DH1
DM1
header (1) payload (0-29)AUX1
CRC (2)
CRC (2)
CRC (2)
CRC (2)
CRC (2)
CRC (2)
(bytes)
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Baseband data ratesPayload User Symmetric AsymmetricHeader Payload max. Rate max. Rate [kbit/s]
Type [byte] [byte] FEC CRC [kbit/s] Forward Reverse
DM1 1 0-17 2/3 yes 108.8 108.8 108.8
DH1 1 0-27 no yes 172.8 172.8 172.8
DM3 2 0-121 2/3 yes 258.1 387.2 54.4
DH3 2 0-183 no yes 390.4 585.6 86.4
DM5 2 0-224 2/3 yes 286.7 477.8 36.3
DH5 2 0-339 no yes 433.9 723.2 57.6
AUX1 1 0-29 no no 185.6 185.6 185.6
HV1 na 10 1/3 no 64.0
HV2 na 20 2/3 no 64.0
HV3 na 30 no no 64.0
DV 1 D 10+(0-9) D 2/3 D yes D 64.0+57.6 D
ACL
1 slot
3 slot
5 slot
SCO
Data Medium rate, Data High rate, High Quality Voice, Data & Voice,
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Baseband link types
f6f0
f1 f7
f12
f13 f19
f18
SCO SCO SCO SCOACL
f5 f21
f4 f20
ACLACLf8
f9
f17
f14
ACL
Polling-based TDD packet transmission 625µs slots, master polls slaves
SCO (Synchronous Connection Oriented) – Voice Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point
ACL (Asynchronous ConnectionLess) – Data Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint
Master
Slave-1
Slave-2
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Robustness
Slow frequency hopping with hopping patterns determined by a master Protection from interference on certain frequencies Separation from other piconets (FH-CDMA)
Retransmission ACL only, very fast
Forward Error Correction SCO and ACL
A C C HF
G G
B D E
NAK ACK
Error in payload(not header!)
Master
Slave-1
Slave-2
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Robustness
FH-CDMA separates different Piconets within a Scatternet. Additionally, FEC can bet used.
Bluetooth’s 1/3 FEC sends 3 copies of the same bit. Receiver performs a majority decision Each receiver bit is subjected to a majority decision.Whichever bit is
in majority is used. It takes care of single bit errors.
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Baseband states of a Bluetooth device
standby
inquiry page
connectedAMA
transmitAMA
parkPMA
holdAMA
sniffAMA
unconnected
connecting
active
low power
Standby: do nothingInquire: search for other devicesPage: connect to a specific deviceConnected: participate in a piconet
detach
Park: release AMA, get PMA Sniff: listen periodically, not each slotHold: stop ACL, SCO still possible, possibly
participate in another piconet
79
Example: Power consumption/CSR BlueCore2
Typical Average Current Consumption (1) VDD=1.8V Temperature = 20°C Mode SCO connection HV3 (1s interval Sniff Mode) (Slave) 26.0 mA SCO connection HV3 (1s interval Sniff Mode) (Master) 26.0 mA SCO connection HV1 (Slave) 53.0 mA SCO connection HV1 (Master) 53.0 mA ACL data transfer 115.2kbps UART (Master) 15.5 mA ACL data transfer 720kbps USB (Slave) 53.0 mA ACL data transfer 720kbps USB (Master) 53.0 mA ACL connection, Sniff Mode 40ms interval, 38.4kbps UART 4.0 mA ACL connection, Sniff Mode 1.28s interval, 38.4kbps UART 0.5 mA Parked Slave, 1.28s beacon interval, 38.4kbps UART 0.6 mA Standby Mode (Connected to host, no RF activity) 47.0 µA Deep Sleep Mode(2) 20.0 µA Notes: (1) Current consumption is the sum of both BC212015A and the flash. (2) Current consumption is for the BC212015A device only. (More: www.csr.com )
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Example: Bluetooth/USB adapter (2002: 50€)
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L2CAP - Logical Link Control and Adaptation Protocol
Simple data link protocol on top of baseband
Connection oriented, connectionless, and signalling channels
Protocol multiplexing RFCOMM, SDP, telephony control
Segmentation & reassembly Up to 64kbyte user data, 16 bit CRC used from baseband
QoS flow specification per channel Follows RFC 1363, specifies delay, jitter, bursts, bandwidth
Group abstraction Create/close group, add/remove member
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L2CAP logical channels
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
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L2CAP
L2CAP available for ACLs only SCOs have to use baseband frequencies directly
L2CAP provides three types of logical channels: Connectionless – Unidirectional channels used for broadcast
from master to slaves Connection-oriented – Bi-directional, supports QoS Signaling : exchanging signaling info between L2CAP entities Signaling Channels use signaling id of 1 2 reserved for connectionless channels For connection oriented channels, a unique CID (>= 64) is
dynamically assigned at each end of the channel to identify connection
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L2CAP
In the figure: Master has a bi-directional signaling channel to each slave CID for this master is 1 Also, master maintains a connectionless uni-directional channel
ato both slaves. CID of slave is 2 while the CID at the beginning of the
connectionless channel is dynamically assigned. L2CAP provides features to add / remove slaves from the group. Dynamically assigned Ids are from 64 to 65535
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L2CAP packet formats
length
2 bytes
CID=2
2
PSM
2
payload
0-65533
length
2 bytes
CID
2
payload
0-65535
length
2 bytes
CID=1
2
One or more commands
Connectionless PDU
Connection-oriented PDU
Signalling command PDU
code ID length data
1 1 2 0
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Security
E3
E2
link key (128 bit)
encryption key (128 bit)
payload key
Keystream generator
Data DataCipher data
Authentication key generation(possibly permanent storage)
Encryption key generation(temporary storage)
PIN (1-16 byte) Pairing
Authentication
Encryption
Ciphering
E3
E2
link key (128 bit)
encryption key (128 bit)
payload key
Keystream generator
PIN (1-16 byte)
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SDP – Service Discovery Protocol
Inquiry/response protocol for discovering services Searching for and browsing services in radio proximity Adapted to the highly dynamic environment Can be complemented by others like SLP, Jini, Salutation, … Defines discovery only, not the usage of services Caching of discovered services Gradual discovery
Service record format Information about services provided by attributes Attributes are composed of an 16 bit ID (name) and a value values may be derived from 128 bit Universally Unique Identifiers (UUID)
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Additional protocols to support legacy protocols/apps.
RFCOMM Emulation 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
OBEX Exchange of objects, IrDA replacement
WAP Interacting with applications on cellular phones
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Profiles Represent default solutions for a certain usage model
Vertical slice through the protocol stack Basis for interoperability
Generic Access Profile Service Discovery Application Profile Cordless Telephony Profile Intercom Profile Serial Port Profile Headset Profile Dial-up Networking Profile Fax Profile LAN Access Profile Generic Object Exchange Profile Object Push Profile File Transfer Profile Synchronization Profile
Additional ProfilesAdvanced Audio DistributionPANAudio Video Remote ControlBasic PrintingBasic ImagingExtended Service DiscoveryGeneric Audio Video DistributionHands FreeHardcopy Cable Replacement
Profiles
Pro
toco
ls
Applications
90
WPAN: IEEE 802.15-1 – BluetoothData rate
Synchronous, connection-oriented: 64 kbit/s
Asynchronous, connectionless 433.9 kbit/s symmetric 723.2 / 57.6 kbit/s asymmetric
Transmission range POS (Personal Operating Space) up to
10 m with special transceivers up to 100 m
Frequency Free 2.4 GHz ISM-band
Security Challenge/response (SAFER+), hopping
sequenceAvailability
Integrated into many products, several vendors
Connection set-up time Depends on power-mode Max. 2.56s, avg. 0.64s
Quality of Service Guarantees, ARQ/FEC
Manageability Public/private keys needed, key
management not specified, simple system integration
Special Advantages/Disadvantages Advantage: already integrated into
several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets
Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency
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WPAN: IEEE 802.15 – future developments 1
802.15-2: Coexistance Coexistence of Wireless Personal Area Networks (802.15) and Wireless
Local Area Networks (802.11), quantify the mutual interference 802.15-3: High-Rate
Standard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost
Data Rates: 11, 22, 33, 44, 55 Mbit/s Quality of Service isochronous protocol Ad hoc peer-to-peer networking Security Low power consumption Low cost Designed to meet the demanding requirements of portable consumer imaging
and multimedia applications
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WPAN: IEEE 802.15 – future developments 2
Several working groups extend the 802.15.3 standard
802.15.3a: Alternative PHY with higher data rate as extension to 802.15.3 Applications: multimedia, picture transmission
802.15.3b: Enhanced interoperability of MAC Correction of errors and ambiguities in the standard
802.15.3c: Alternative PHY at 57-64 GHz Goal: data rates above 2 Gbit/s
Not all these working groups really create a standard, not all standards will be found in products later …
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WPAN: IEEE 802.15 – future developments 3
802.15-4: Low-Rate, Very Low-Power Low data rate solution with multi-month to multi-year battery life and very low complexity Potential applications are sensors, interactive toys, smart badges, remote controls, and
home automation Data rates of 20-250 kbit/s, latency down to 15 ms Master-Slave or Peer-to-Peer operation Up to 254 devices or 64516 simpler nodes Support for critical latency devices, such as joysticks CSMA/CA channel access (data centric), slotted (beacon) or unslotted Automatic network establishment by the PAN coordinator Dynamic device addressing, flexible addressing format Fully handshaked protocol for transfer reliability Power management to ensure low power consumption 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and
one channel in the European 868 MHz band Basis of the ZigBee technology – www.zigbee.org
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ZigBee
Relation to 802.15.4 similar to Bluetooth / 802.15.1
Pushed by Chipcon, ember, freescale (Motorola), Honeywell, Mitsubishi, Motorola, Philips, Samsung
More 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 2 ZigBee protocol stack up to the applications
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WPAN: IEEE 802.15 – future developments 4
Several working groups extend the 802.15.4 standard
802.15.4a: Alternative PHY with lower data rate as extension to 802.15.4 Properties: precise localization (< 1m precision), extremely low power consumption,
longer range Two PHY alternatives
UWB (Ultra Wideband): ultra short pulses, communication and localization CSS (Chirp Spread Spectrum): communication only
802.15.4b: Extensions, corrections, and clarifications regarding 802.15.4 Usage of new bands, more flexible security mechanisms
802.15.5: Mesh Networking Partial meshes, full meshes Range extension, more robustness, longer battery live
Not all these working groups really create a standard, not all standards will be found in products later …
96
Some more IEEE standards for mobile communications
IEEE 802.16: Broadband Wireless Access / WirelessMAN / WiMax Wireless distribution system, e.g., for the last mile, alternative to DSL 75 Mbit/s up to 50 km LOS, up to 10 km NLOS; 2-66 GHz band Initial standards without roaming or mobility support 802.16e 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 traffic Peak rate > 1 Mbit/s per user Different mobility classes up to 250 km/h and ranges up to 15 km
IEEE 802.21: Media Independent Handover Interoperability Standardize handover between different 802.x and/or non 802 networks
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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