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)

17

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/

19

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!

20

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

22

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

24

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

25

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

hron

izat

ion

prio

rity

dete

ctio

n

prio

rity

asse

rtio

n

t

user

dat

a

elim

inat

ion

burs

t

elim

inat

ion

surv

ival

ver

ifica

tion

yiel

d lis

teni

ng

IYSIPS IPA IES IESV

28

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

39

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

70

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)

74

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,

75

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

76

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

77

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.

78

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 )

80

Example: Bluetooth/USB adapter (2002: 50€)

81

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

82

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

83

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

84

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

85

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

86

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)

87

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)

88

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

89

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

91

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

92

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 …

93

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

94

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

95

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

97