[PDF] Mobile Communications Chapter 7: Wireless LANs

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83067_3wireless_lans.pdf Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.1

Mobile Communications

Chapter 7: Wireless LANsSlides by Jochen Schiller

with modifications by Emmanuel Agu qCharacteristics qIEEE 802.11 qPHY qMAC qRoaming q.11a, b, g, h, i ...qHIPERLAN qBluetooth/ IEEE 802.15.x qIEEE 802.16/.20/.21/.22 qRFID qComparison Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.2

Mobile CommunicationTechnology accordingto IEEE

Localwirelessnetworks

WLAN802.11802.11a

802.11b

802.11i/e/.../w802.11gWiFi

802.11hPersonal wirelessnw

WPAN802.15802.15.4

802.15.1

802.15.2Bluetooth

802.15.4a/bZigBee

802.15.3Wirelessdistributionnetworks

WMAN802.16 (BroadbandWirelessAccess)

802.20 (Mobile BroadbandWirelessAccess)+ MobilityWiMAX802.15.3a/b802.15.5

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.3

Characteristics of wireless LANs

Advantages

qvery flexible within reception area qAd-hoc networks do not need planning q(almost) no wiring difficulties (e.g. historic buildings, firewalls) qmore robust against disasters like, e.g., earthquakes, fire

Disadvantages

qlow bandwidth compared to wired networks (1-10 Mbit/s) qmany proprietary solutions, especially for higher bit-rates, standards take their time (e.g. IEEE 802.11) qmany national restrictions for wireless, long time to establish global solutions like, e.g., IMT-2000 Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.4

Design goals for wireless LANs

qglobal, seamless operation qlow power for battery use qno special permissions or licenses needed to use the LAN qrobust transmission technology qsimplified spontaneous cooperation at meetings qeasy to use for everyone, simple management qprotection of investment in wired networks qsecurity (no one should be able to read my data), privacy (no one should be able to collect user profiles), safety (low radiation) qtransparency concerning applications and higher layer protocols,but also location awareness if necessary Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.5

Comparison: infrared vs. radio transmission

Infrared

quses IR diodes, diffuse light, multiple reflections (walls, furniture etc.)

Advantages

qsimple, cheap, available in many mobile devices qno licenses needed qsimple shielding possible

Disadvantages

qinterference by sunlight, heat sources etc. qmany things shield or absorb IR light qlow bandwidth

Example

qIrDA (Infrared Data Association) interface available everywhereRadio qtypically using the license free

ISM band at 2.4 GHz

Advantages

qexperience from wireless WAN and mobile phones can be used qcoverage of larger areas possible (radio can penetrate walls, furniture etc.)

Disadvantages

qlimited license free frequency bands qshielding more difficult, electrical interference

Example

qMany different products Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.6

Comparison: infrastructure vs. ad-hoc networks

infrastructure network ad-hoc networkAPAPAP wirednetworkAP: Access Point Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.7

802.11 -Architecture of an infrastructure network

Station (STA)

qterminal with access mechanisms to the wireless medium and radio contact to the access point

Basic Service Set (BSS)

qgroup of stations using the same radio frequency

Access Point

qstation integrated into the wireless

LAN and the distribution system

Portal

qbridge to other (wired) networks

Distribution System

qinterconnection network to form one logical network (EES:

Extended Service Set) based

on several BSSDistribution SystemPortal

802.x LANAccess

Point

802.11 LAN

BSS

2802.11 LAN

BSS

1Access

PointSTA

1STA

2STA3ESS

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.8

802.11 -Architecture of an ad-hoc network

Direct communication within a limited

range qStation (STA): terminal with access mechanisms to the wireless medium qIndependent Basic Service Set (IBSS): group of stations using the same radio frequency802.11 LANIBSS

2802.11 LAN

IBSS 1STA 1STA 4STA 5STA 2STA 3 Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.9

IEEE standard 802.11

mobile terminal access pointfixed terminalapplication TCP

802.11 PHY802.11 MACIP

802.3 MAC

802.3 PHYapplication

TCP

802.3 PHY802.3 MACIP

802.11 MAC

802.11 PHYLLCinfrastructure

networkLLCLLC Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.10

802.11 -Layers and functions

PLCP PhysicalLayerConvergenceProtocol

qclear channel assessment signal (carrier sense)

PMD PhysicalMedium Dependent

qmodulation, coding

PHY Management

qchannel selection, MIB

Station Management

qcoordination of all management functionsPMDPLCPMACLLC

MAC Management

PHY ManagementMAC

qaccess mechanisms, fragmentation, encryption

MAC Management

qsynchronization, roaming, MIB, power managementPHY DLC

Station Management

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.11

802.11 -Physical layer (classical)

3 versions: 2 radio (typ. 2.4 GHz), 1 IR

qdata rates 1 or 2 Mbit/s

FHSS (Frequency Hopping Spread Spectrum)

qspreading, despreading, signal strength, typ. 1 Mbit/s qmin. 2.5 frequency hops/s (USA), two-level GFSK modulation

DSSS (Direct Sequence Spread Spectrum)

qDBPSK modulation for 1 Mbit/s (Differential Binary Phase Shift Keying),

DQPSK for 2 Mbit/s (Differential QuadraturePSK)

qpreamble and header of a frame is always transmitted with 1 Mbit/s, rest of transmission 1 or 2 Mbit/s qchipping sequence: +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1 (Barker code) qmax. radiated power 1 W (USA), 100 mW(EU), min. 1mW

Infrared

q850-950 nm, diffuse light, typ. 10 m range qcarrier detection, energy detection, synchronization Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.12

802.11 -MAC layer I -DFWMAC

Traffic services

qAsynchronous Data Service (mandatory) lexchange of data packets based on "best-effort" lsupport of broadcast and multicast qTime-Bounded Service (optional) limplemented using PCF (Point Coordination Function)

Access methods

qDFWMAC-DCF CSMA/CA (mandatory) lcollision avoidance via randomized "back-off" mechanism lminimum distance between consecutive packets lACK packet for acknowledgements (not for broadcasts) qDFWMAC-DCF w/ RTS/CTS (optional) lDistributed Foundation Wireless MAC lavoids hidden terminal problem qDFWMAC-PCF (optional) laccess point polls terminals according to a list Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.13

802.11 -MAC layer II

Priorities

qdefined through different inter frame spaces qno guaranteed, hard priorities qSIFS (Short Inter Frame Spacing) lhighest priority, for ACK, CTS, polling response qPIFS (PCF IFS) lmedium priority, for time-bounded service using PCF qDIFS (DCF, Distributed Coordination Function IFS) llowest priority, for asynchronous data servicetmediumbusySIFSPIFS

DIFSDIFS

nextframecontention directaccessif mediumisfree³DIFS Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.14 tmediumbusyDIFSDIFS nextframecontentionwindow (randomizedback-off mechanism)802.11 -CSMA/CA access method I qstation ready to send senses medium (based on PHY layer CCA,

Clear Channel Assessment)

qif the medium is free for the duration of an Inter-Frame Space (IFS), the station can start sending (IFS depends on service type) qif the medium is busy, the station has to wait for a free IFS, then the station must additionally wait a random back-off time (collision avoidance, multiple of slot-time) qif another station occupies the medium during the back-off time of the station, the back-off timer stops (fairness) qIf multiple stations have backed off, when 1 timer expires, other timers frozenslottimedirectaccessif mediumisfree³DIFS Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.15

802.11 -CSMA/CA access method II

Sending unicastpackets

qstation has to wait for DIFS before sending data qreceivers acknowledge at once (after waiting for SIFS) if the packet was received correctly (CRC) qautomatic retransmission of data packets in case of transmissionerrors tSIFS

DIFSdataACK

waitingtimeother stationsreceiversenderdata DIFS contention Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.16

802.11 -DFWMAC

Sending unicastpackets

qstation can send RTS with reservation parameter after waiting for DIFS (reservation determines amount of time the data packet needs themedium) qacknowledgement via CTS after SIFS by receiver (if ready to receive) qsender can now send data at once, acknowledgement via ACK qother stations store medium reservations distributed via RTS andCTS tSIFS

DIFSdataACK

deferaccessother stationsreceiver senderdata DIFS contentionRTS

CTSSIFSSIFS

NAV (RTS)

NAV (CTS)

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.17

Fragmentation

tSIFS

DIFSdataACK

1other

stationsreceiver senderfrag 1DIFS contentionRTS

CTSSIFSSIFS

NAV (RTS)

NAV (CTS)

NAV (frag

1)NAV (ACK

1)SIFSACK

2frag 2SIFS Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.18

DFWMAC-PCF IPIFS

stations'

NAVwireless

stationspoint coordinatorD 1U 1SIFS

NAVSIFSD

2U

2SIFSSIFSSuperFramet

0mediumbusyt

1 Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.19

802.11 -Frame format

Types qcontrol frames, management frames, data frames

Sequence numbers

qimportant against duplicated frames due to lost ACKs

Addresses

qreceiver, transmitter (physical), BSS identifier, sender (logical)

Miscellaneous

qsending time, checksum, frame control, dataFrame

ControlDuration/

IDAddress

1Address

2Address

3Sequence

ControlAddress

4DataCRC

2

26666240-2312bytesProtocol

versionTypeSubtypeTo

DSMore

FragRetryPower

MgmtMore

DataWEP

2241From

DS1Order

bits111111 Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.20

802.11 -MAC management

Synchronization

qClock skew may happen qInfrastructure:AP broadcasts beacons, other nodes correct skew qAd hoc:All nodes broadcast beacons

Power management

qSave battery, nodes can go to sleep, wake up periodically to receive qInfrastructure: AP buffers packets for sleeping nodes qAd hoc: sender buffers packets for sleeping destinations

Association/Reassociation

qRoaming: Move from access point to access point as user moves qscanning, i.e. active search for a network qNode sends message to new AP, says goodbye to old AP

MIB -Management Information Base

qAll information for managing network, node stored in SNMP MIB qMIB can be read (access) or written to (update) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.21

WLAN: IEEE 802.11b

Data rate

q1, 2, 5.5, 11 Mbit/s, depending on SNR qUser data rate max. approx. 6

Mbit/s

Transmission range

q300m outdoor, 30m indoor qMax. data rate ~10m indoor

Frequency

qFree 2.4 GHz ISM-band

Security

qLimited, WEP insecure, SSID

Availability

qMany products, many vendorsConnection set-up time qConnectionless/always on

Quality of Service

qTyp. Best effort, no guarantees (unless polling is used, limited support in products)

Manageability

qLimited (no automated key distribution, sym. Encryption)

Special Advantages/Disadvantages

qAdvantage: many installed systems, lot of experience, available worldwide, free ISM-band, many vendors, integrated in laptops, simple system qDisadvantage: heavy interference on ISM-band, no service guarantees, slow relative speed only Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.22

Channelselection(non-overlapping)2400

[MHz]24122483.524422472 channel1channel7channel13Europe (ETSI)

US (FCC)/Canada(IC)2400

[MHz]24122483.524372462 channel1channel6channel1122 MHz

22 MHz

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.23

WLAN: IEEE 802.11a

Data rate

q6, 9, 12, 18, 24, 36, 48, 54 Mbit/s, depending on SNR qUser throughput (1500 byte packets): 5.3 (6), 18 (24), 24 (36), 32 (54) q6, 12, 24 Mbit/s mandatory

Transmission range

q100m outdoor, 10m indoor lE.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

qFree 5.15-5.25, 5.25-5.35, 5.725-5.825

GHz ISM-band

Security

qLimited, WEP insecure, SSID

Availability

qSome products, some vendorsConnection set-up time qConnectionless/always on

Quality of Service

qTyp. best effort, no guarantees (same as all 802.11 products)

Manageability

qLimited (no automated key distribution, sym. Encryption)

Special Advantages/Disadvantages

qAdvantage: fits into 802.x standards, free

ISM-band, available, simple system,

uses less crowded 5 GHz band qDisadvantage: stronger shading due to higher frequency, no QoS Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.24

WLAN: IEEE 802.11 -future developments (03/2005)

802.11c: Bridge Support

qDefinition of MAC proceduresto supportbridgesas extensionto 802.1D

802.11d: Regulatory Domain Update

qSupport of additional regulations related to channel selection, hopping sequences

802.11e: MAC Enhancements -QoS

qEnhance the current 802.11 MAC to expand support for applications with Quality of Service requirements, and in the capabilities and efficiency of the protocol qDefinition of a data flow ("connection") with parameters like rate, burst, period... qAdditional energy saving mechanisms and more efficient retransmission

802.11f: Inter-Access Point Protocol

qEstablish an Inter-Access Point Protocol for data exchange via the distribution system qCurrently unclear to which extend manufacturers will follow thissuggestion

802.11g: Data Rates > 20 Mbit/s at 2.4 GHz; 54 Mbit/s, OFDM

qSuccessful successor of 802.11b, performance loss during mixed operation with 11b

802.11h: Spectrum Managed 802.11a

qExtension 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) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.25

WLAN: IEEE 802.11-future developments (03/2005)

802.11i: Enhanced Security Mechanisms

qEnhance the current 802.11 MAC to provide improvements in security. qTKIP enhances the insecure WEP, but remains compatible to olderWEP systems qAES provides a secure encryption method and is based on new hardware

802.11j: Extensions for operations in Japan

qChanges of 802.11a for operation at 5GHz in Japan using only half the channel width at larger range

802.11k: Methods for channel measurements

qDevices 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

qChanges of PHY and MAC with the goal of 100Mbit/s at MAC SAP qMIMO antennas (Multiple Input Multiple Output), up to 600Mbit/s are currently feasible qHowever, still a large overhead due to protocol headers and inefficient mechanisms

802.11p: Inter car communications

qCommunication between cars/road side and cars/cars qPlanned for relative speeds of min. 200km/h and ranges over 1000m qUsage of 5.850-5.925GHz band in North America Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.26

WLAN: IEEE 802.11-future developments (03/2005)

802.11r: Faster Handover between BSS

qSecure, fast handover of a station from one AP to another withinan ESS qCurrent mechanisms (even newer standards like 802.11i) plus incompatible devices from different vendors are massive problems for the use of, e.g., VoIPin WLANs qHandover should be feasible within 50ms in order to support multimedia applications efficiently

802.11s: Mesh Networking

qDesign of a self-configuring Wireless Distribution System (WDS) based on 802.11 qSupport of point-to-point and broadcast communication across several hops

802.11t: Performance evaluation of 802.11 networks

qStandardization of performance measurement schemes

802.11u: Interworkingwith additional external networks

802.11v: Network management

qExtensions of current management functions, channel measurements qDefinition of a unified interface

802.11w: Securing of network control

qClassical 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/ Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.27

ETSI -HIPERLAN (historical)

ETSI standard

qEuropean standard, cf. GSM, DECT, ... qEnhancement of local Networks and interworkingwith fixed networks qintegration of time-sensitive services from the early beginning

HIPERLAN family

qone standard cannot satisfy all requirements lrange, bandwidth, QoSsupport lcommercial constraints qHIPERLAN 1 standardized since 1996 -no products!physicallayerchannelaccess controllayermediumaccess

controllayerphysicallayerdatalink layerHIPERLAN layersOSI layersnetworklayerhigherlayersphysicallayermediumaccess

controllayerlogicallink controllayer

IEEE 802.x layers

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.28

Overview: original HIPERLAN protocol family

HIPERLAN 1HIPERLAN 2HIPERLAN 3HIPERLAN 4

Applicationwireless LANaccess to ATM

fixed networkswireless local looppoint-to-point wireless ATM connections

Frequency5.1-5.3GHz17.2-17.3GHz

Topologydecentralized ad-

hoc/infrastructurecellular, centralizedpoint-to- multipointpoint-to-point

Antennaomni-directionaldirectional

Range50 m50-100 m5000 m150 m

QoSstatisticalATM traffic classes (VBR, CBR, ABR, UBR)

Mobility<10m/sstationary

Interfaceconventional LANATM networks

Data rate23.5 Mbit/s>20 Mbit/s155 Mbit/sPower

conservationyesnot necessary

HIPERLAN 1 neverreachedproductstatus,

theotherstandardshavebeenrenamed/modfied! Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.29

HIPERLAN 1 -Characteristics

Data transmission

qpoint-to-point, point-to-multipoint, connectionless q23.5 Mbit/s, 1 W power, 2383 byte max. packet size

Services

qasynchronous and time-bounded services with hierarchical priorities qcompatible with ISO MAC

Topology

qinfrastructure or ad-hoc networks qtransmission range can be larger then coverage of a single node ("forwarding" integrated in mobile terminals)

Further mechanisms

qpower saving, encryption, checksums Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.30

HIPERLAN 1 -CAC sublayer

Channel Access Control (CAC)

qassure that terminal does not access forbidden channels qpriority scheme, access with EY-NPMA q3 EY-NPMA phases: priority resolution, contention resolution, transmission

Priorities

q5 priority levels for QoSsupport qQoSis mapped onto a priority level with the help of the packet

lifetime (set by an application) prioritizationcontentiontransmissiontransmissionsynchronizationpriority detectionpriority assertiont

user data elimination burstelimination survivalverificationyield listeningI

YSIPSIPAIESIESV

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.31

HIPERLAN 1 -EY-NPMA II

Several terminals can now have the same priority and wish to send qcontention phase lElimination Burst: all remaining terminals send a burst to eliminate contenders (11111010100010011100000110010110, high bit-rate) lElimination Survival Verification: contenders now sense the channel, if the channel is free they can continue, otherwise they have been eliminated lYield Listening: contenders again listen in slots with a nonzeroprobability, if the terminal senses its slot idle it is free to transmit at the end of the contention phase lthe important part is now to set the parameters for burst duration and channel sensing (slot-based, exponentially distributed) qdata transmission lthe winner can now send its data (however, a small chance of collision remains) lif 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 qsynchronization using the last data transmission Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.32

HIPERLAN 1 -MAC layer

Compatible to ISO MAC

Supports time-bounded services via a priority scheme

Packet forwarding

qsupport of directed (point-to-point) forwarding and broadcast forwarding (if no path information is available) qsupport of QoSwhile forwarding

Encryption mechanisms

qmechanisms integrated, but without key management

Power conservation mechanisms

qmobile terminals can agree upon awake patterns (e.g., periodic wake-ups to receive data) qadditionally, some nodes in the networks must be able to buffer data for sleeping terminals and to forward them at the right time (so called stores) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.33

Some history: Why wireless ATM?

qseamless connection to wired ATM, a integrated services high- performance network supporting different types a traffic streams qATM networks scale well: private and corporate LANs, WAN qB-ISDN uses ATM as backbone infrastructure and integrates several different services in one universal system qmobile phones and mobile communications have increasing importance in everyday life qcurrent wireless LANs do not offer adequate support for multimedia data streams qmerging mobile communication and ATM leads to wireless ATM from a telecommunication provider point of view qgoal: seamless integration of mobility into B-ISDN Problem: very high complexity of the system -never reached products Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.34

ATM -basic principle

qfavored by the telecommunication industry for advanced high-performance networks, e.g., B-ISDN, as transport mechanism qstatistical (asynchronous, on demand) TDM (ATDM, STDM) qcell header determines the connection the user data belongs to qmixing of different cell-rates is possible ldifferent bit-rates, constant or variable, feasible qinteresting for data sources with varying bit-rate: le.g., guaranteed minimum bit-rate ladditionally burstytraffic if allowed by the network

ATM cell:

5 48 [byte]

connectionidentifier, checksumetc.cellheaderuserdata Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.35

Cell-based transmission

qasynchronous, cell-based transmission as basis for ATM qcontinuous cell-stream qadditional cells necessary for operation and maintenance of the network (OAM cells; Operation and Maintenance) qOAM cells can be inserted after fixed intervals to create a logical frame structure qif a station has no data to send it automatically inserts idle cells that can be discarded at every intermediate system without further notice Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.36 physical layer

ATM layerATM adaptation layerhigher

layershigher layerscontrol planelayer management plane managementuser planeplanes layersB-ISDN protocol reference model

3 dimensional reference model

qthree vertical planes (columns) luser plane lcontrol plane lmanagement plane qthree hierarchical layers lphysical layer lATM layer lATM adaptation layer

Out-of-Band-Signaling: user data is

transmitted separately from control informationmanagement plane Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.37

ATM Forum Wireless ATM Working Group

qATM Forum founded the Wireless ATM Working Group June 1996 qTask: development of specifications to enable the use of ATM technology also for wireless networks with a large coverage of current network scenarios (private and public, local and global) qcompatibility to existing ATM Forum standards important qit should be possible to easily upgrade existing ATM networks with mobility functions and radio access qtwo sub-groups of work items

Mobile ATM Protocol Extensions

qhandover signaling qlocation management qmobile routing qtraffic andQoSControl qnetwork managementRadio Access Layer (RAL) Protocols qradio access layer qwireless media access control qwireless data link control qradio resource control qhandover issues Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.38

WATM services

Office environment

qmultimedia conferencing, online multimedia database access

Universities, schools, training centers

qdistance learning, teaching

Industry

qdatabase connection, surveillance, real-time factory management

Hospitals

qreliable, high-bandwidth network, medical images, remote monitoring Home qhigh-bandwidth interconnect of devices (TV, CD, PC, ...)

Networked vehicles

qtrucks, aircraft etc. interconnect, platooning, intelligent roads Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.39

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 (LocationServer)

AUS (AuthenticationServer)

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.40

Reference model

WMT

WMTEMAS-EEMAS-NEMAS-NM-NNIRAS

RAS LS AUS Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.41

BRAN -Broadband Radio Access Networks

Motivation

qderegulation, privatization, new companies, new services qHow to reach the customer? lalternatives: xDSL, cable, satellite, radio

Radio access

qflexible (supports traffic mix, multiplexing for higher efficiency, can be asymmetrical) qquick installation qeconomic (incremental growth possible)

Market

qprivate customers (Internet access, tele-xy...) qsmall and medium sized business (Internet, MM conferencing, VPN)

Scope of standardization

qaccess networks, indoor/campus mobility, 25-155 Mbit/s, 50 m-5 km qcoordination with ATM Forum, IETF, ETSI, IEEE, .... Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.42

Broadbandnetworktypes

Common characteristics

qATM QoS(CBR, VBR, UBR, ABR)

HIPERLAN/2

qshort range (< 200 m), indoor/campus, 25 Mbit/s user data rate qaccess to telecommunication systems, multimedia applications, mobility (<10 m/s)

HIPERACCESS

qwider range (< 5 km), outdoor, 25 Mbit/s user data rate qfixed radio links to customers ("last mile"), alternative to xDSLor cable modem, quick installation qSeveral (proprietary) products exist with 155 Mbit/s plus QoS

HIPERLINK -currently no activities

qintermediate link, 155 Mbit/s qconnection of HIPERLAN access points or connection between

HIPERACCESS nodes

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.43

BRAN and legacy networks

Independence

qBRAN as access network independent from the fixed network qInterworkingof TCP/IP and ATM under study

Layered model

qNetwork Convergence Sub-layer as superset of all requirements for IP and

ATMcorenetwork

ATMcorenetwork

IPnetworkconvergencesublayerBRAN datalink controlBRAN PHY-1BRAN PHY-2...Coordination qIETF (TCP/IP) qATM forum (ATM) qETSI (UMTS) qCEPT, ITU-R, ... (radio frequencies) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.44

HiperLAN2 (historical)

Official name: BRAN HIPERLAN Type 2

qH/2, HIPERLAN/2 also used

High data rates for users

qMore efficient than 802.11a

Connection oriented

QoSsupport

Dynamic frequency selection

Security support

qStrong encryption/authentication

Mobility support

Network and application independent

qconvergence layers for Ethernet, IEEE 1394, ATM, 3G

Power save modes

Plug and Play

No products -but several mechanisms have been

Adopted by other standards (e.g. 802.11a)

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.45 231AP
HiperLAN2 architecture and handover scenariosAPTAPCCore

Network

(Ethernet,

Firewire,

ATM,

UMTS)APT

APTAPCAP

MT 4MT 3MT 2MT 1 Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.46

HiperLAN2 protocol stack

HigherlayersConvergencelayerDatalink control-

basicdata transportfunctionScope of

HiperLAN2

standardsDLC control

SAPDLC user

SAPRadio link controlsublayerPhysicallayerRadio

resource controlAssoc. controlDLC conn. controlError controlRadio link control

Medium access control

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.47

Operating channels of HiperLAN2 in Europe

5150
[MHz]518053505200

364416.6 MHz

center frequency =

5000 + 5*channel number [MHz]channel

4048525660645220524052605280530053205470

[MHz]550057255520

10010816.6 MHz

channel104112116120124128554055605580560056205640132136140566056805700 Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.48

Bluetooth

Idea qUniversal radio interface for ad-hoc wireless connectivity qInterconnecting computer and peripherals, handheld devices, PDAs, cell phones -replacement of IrDA qEmbedded in other devices, goal: 5€/device (2005: 40€/USB bluetooth) qShort range (10 m), low power consumption, license-free 2.45 GHz ISM qVoice and data transmission, approx. 1 Mbit/s gross data rate

One of the first modules (Ericsson).

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.49

Bluetooth

History

q1994: Ericsson (Mattison/Haartsen), "MC-link" project qRenaming of the project: Bluetooth according to Harald"Blåtand"Gormsen [son of Gorm], King of Denmark in the 10thcentury

q1998: foundation of Bluetooth SIG, www.bluetooth.orgq1999: erection of a rune stone at Ercisson/Lund ;-)

q2001: first consumer products for mass market, spec. version 1.1released q2005: 5 million chips/week

Special Interest Group

qOriginal founding members: Ericsson, Intel, IBM, Nokia, Toshiba qAdded promoters: 3Com, Agere(was: Lucent), Microsoft, Motorola q> 2500 members qCommon specification and certification of products (was: ) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.50

Historyand hi-tech...

1999:

Ericsson mobile

communicationsAB restedennastentill minneavHarald

Blåtand, somfick ge

sittnamnåten ny teknologiförtrådlös, mobil kommunikation. Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.51

Characteristics

2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing

qChannel 0: 2402 MHz ... channel 78: 2480 MHz qG-FSK modulation, 1-100 mWtransmit power

FHSS and TDD

qFrequency hopping with 1600 hops/s qHopping sequence in a pseudo random fashion, determined by a master qTime division duplex for send/receive separation

Voice link -SCO (Synchronous Connection Oriented)

qFEC (forward error correction), no retransmission, 64 kbit/s duplex, point- to-point, circuit switched

Data link -ACL (Asynchronous ConnectionLess)

qAsynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched

Topology

qOverlapping piconets(stars) forming a scatternet Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.52

Piconet

Collection of devices connected in an ad hoc

fashion

One unit acts as master and the others as slaves

for the lifetime of the piconet

Master determines hopping pattern, slaves have

to synchronize

Each piconethas a unique hopping pattern

Participation in a piconet= synchronization to

hopping sequence

Each piconethas one masterand up to 7

simultaneous slaves (> 200 could be parked)M=Master

S=SlaveP=Parked

SB=StandbyMS

PSBS SP P SB Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.53

Forming a piconet

All devices in a piconethop together

qMaster gives slaves its clock and device ID lHopping pattern: determined by device ID (48 bit, unique worldwide) lPhase in hopping pattern determined by clock

Addressing

qActive Member Address (AMA, 3 bit) qParked Member Address (PMA, 8 bit)SBSB

SBSBSB

SBSB SB SBMS PSBS SP P

SB¿

¸ ¾ Á

¹»·

½

¸»»

» Á

»»»

» ¸ Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.54

Scatternet

Linking of multiple co-located piconetsthrough the sharing of common master or slave devices qDevices can be slave in one piconetand master of another

Communication between piconets

qDevices jumping back and forth between the piconets

M=Master

S=Slave

P=Parked

SB=StandbyMS

PSBS SP P SBMS SP

SBPiconets

(each with a capacity of

720 kbit/s)

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.55

Bluetooth protocol stack

RadioBasebandLink ManagerControl

Host

Controller

InterfaceLogical Link Control and Adaptation Protocol (L2CAP)AudioTCS BINSDPOBEXvCal/vCardIPNW apps.

TCP/UDP

BNEP

RFCOMM (serial line interface)AT modem

commandstelephony apps.audio apps.mgmnt. apps.AT: attention sequence

OBEX: object exchange

TCS BIN: telephony control protocol specification -binary BNEP: Bluetooth network encapsulation protocolSDP: service discovery protocol

RFCOMM: radio frequency comm.PPP

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.56 S

Frequency selection during data transmissionf

k625µsf k+1fk+2fk+3fk+4f k+3fk+4fk f kf k+5 f k+5 f k+1f k+6f k+6f k+6MMMM M MMMM t t tSS SS S Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.57

SCO payload types

payload (30) audio (30)audio (10) audio (10)

HV3HV2HV1

DVFEC (20)

audio (20)FEC (10) header (1)payload (0-9)2/3 FECCRC (2) (bytes) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.58

Basebandlink types

Polling-based TDD packet transmission

q625µs slots, master polls slaves

SCO (Synchronous Connection Oriented) -Voice

qPeriodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point

ACL (Asynchronous ConnectionLess) -Data

qVariable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint

MASTER

SLAVE 1

SLAVE 2f

6f 0f 1f 7f 12f 13f 19f

18SCOSCOSCOSCOACLf

5f 21f
4f

20ACLACLf

8f 9f 17f 14ACL Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.59

Robustness

Slow frequency hopping with hopping patterns determined by a master qProtection from interference on certain frequencies qSeparation from other piconets(FH-CDMA)

Retransmission

qACL only, very fast

Forward Error Correction

qSCO and ACLMASTER

SLAVE 1SLAVE 2ACCHF

GGBDENAKACKError in payload

(not header!) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.60

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) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.61

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

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.62 L2CAP -Logical Link Control and Adaptation Protocol

Simple data link protocol on top of baseband

Connection oriented, connectionless, and signallingchannels

Protocol multiplexing

qRFCOMM, SDP, telephony control

Segmentation & reassembly

qUp to 64kbyte user data, 16 bit CRC used from baseband

QoSflow specification per channel

qFollows RFC 1363, specifies delay, jitter, bursts, bandwidth

Group abstraction

qCreate/close group, add/remove member Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.63

Security

E 3E

2link key (128 bit)

encryption key (128 bit) payload keyKeystreamgenerator Data

DataCipher dataAuthentication key generation

(possibly permanent storage)Encryption key generation (temporary storage)PIN (1-16 byte)User input (initialization)

Pairing

Authentication

Encryption

CipheringE

3E

2link key (128 bit)

encryption key (128 bit) payload keyKeystreamgeneratorPIN (1-16 byte) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.64

SDP -Service Discovery Protocol

Inquiry/response protocol for discovering services qSearching for and browsing services in radio proximity qAdapted to the highly dynamic environment qCan be complemented by others like SLP, Jini, Salutation, ... qDefines discovery only, not the usage of services qCaching of discovered services qGradual discovery Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.65 Additional protocols to support legacy protocols/apps.

RFCOMM

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

Telephony Control Protocol Specification (TCS)

qCall control (setup, release) qGroup management OBEX qExchange of objects, IrDA replacement WAP qInteracting with applications on cellular phones Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.66

Profiles

Represent default solutions for a certain usage model qVertical slice through the protocol stack qBasis 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 ProfileAdditional Profiles

Advanced Audio Distribution

PAN

Audio Video Remote Control

Basic Printing

Basic Imaging

Extended Service Discovery

Generic Audio Video Distribution

Hands Free

Hardcopy Cable ReplacementProfilesProtocolsApplications Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.67

WPAN: IEEE 802.15-1 -Bluetooth

Data rate

qSynchronous, connection-oriented:

64 kbit/s

qAsynchronous, connectionless l433.9 kbit/s symmetric l723.2 / 57.6 kbit/s asymmetric

Transmission range

qPOS (Personal Operating Space) up to 10 m qwith special transceivers up to 100 m

Frequency

qFree 2.4 GHz ISM-band

Security

qChallenge/response (SAFER+), hopping sequence

Availability

qIntegrated into many products, several vendorsConnection set-up time qDepends on power-mode qMax. 2.56s, avg. 0.64s

Quality of Service

qGuarantees, ARQ/FEC

Manageability

qPublic/private keys needed, key management not specified, simple system integration

Special Advantages/Disadvantages

qAdvantage: already integrated into several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets qDisadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.68

WPAN: IEEE 802.15 -future developments 1

802.15-2: Coexistence

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

802.15-3: High-Rate

qStandard for high-rate (20Mbit/s or greater) WPANs, while still low- power/low-cost qData Rates: 11, 22, 33, 44, 55 Mbit/s qQuality of Service isochronous protocol qAd hoc peer-to-peer networking qSecurity qLow power consumption qLow cost qDesigned to meet the demanding requirements of portable consumer imaging and multimedia applications Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.69

WPAN: IEEE 802.15 -future developments 3

802.15-4: Low-Rate, Very Low-Power

qLow data rate solution with multi-month to multi-year battery life and very low complexity qPotential applications are sensors, interactive toys, smart badges, remote controls, and home automation qData rates of 20-250 kbit/s, latency down to 15 ms qMaster-Slave or Peer-to-Peer operation qUp to 254 devices or 64516 simpler nodes qSupport for critical latency devices, such as joysticks qCSMA/CA channel access (data centric), slotted (beacon) or unslotted qAutomatic network establishment by the PAN coordinator qDynamic device addressing,flexible addressing format qFully handshakedprotocol for transfer reliability qPower management to ensure low power consumption q16 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 ZigBeetechnology -www.zigbee.org

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.70

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

qPromoter (40000$/Jahr), Participant (9500$/Jahr), Adopter (3500$/Jahr) No free access to the specifications (only promoters and participants)

ZigBeeplatforms comprise

qIEEE 802.15.4 for layers 1 and 2 qZigBeeprotocol stack up to the applications

802.15.5: Mesh Networking

qPartial meshes, full meshes qRange extension, more robustness, longer battery live Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.71 Some more IEEE standards for mobile communications IEEE 802.16: Broadband Wireless Access / WirelessMAN/ WiMax qWireless distribution system, e.g., for the last mile, alternative to DSL q75 Mbit/s up to 50 km LOS, up to 10 km NLOS; 2-66 GHz band qInitial standards without roaming or mobility support q802.16e adds mobility support, allows for roaming at 150 km/h lUnclear relation to 802.20, 802.16 started as fixed system... IEEE 802.20: Mobile Broadband Wireless Access (MBWA) qLicensed bands < 3.5 GHz, optimized for IP traffic qPeak rate > 1 Mbit/s per user qDifferent mobility classes up to 250 km/h and ranges up to 15 km IEEE 802.21: Media Independent Handover Interoperability qStandardize handover between different 802.x and/or non 802 networks IEEE 802.22: Wireless Regional Area Networks (WRAN) qRadio-based PHY/MAC for use by license-exempt devices on a non- interfering basis in spectrum that is allocated to the TV Broadcast Service Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.72

WLAN: Home RF -yet another standard, no success

Data rate

q0.8, 1.6, 5, 10 Mbit/s

Transmission range

q300m outdoor, 30m indoor

Frequency

q2.4 GHz ISM

Security

qStrong encryption, no open access Cost qAdapter 130€, base station 230€

Availability

qSeveral products from different vendors, no more supportConnection set-up time q10 ms bounded latency

Quality of Service

qUp to 8 streams A/V, up to 8 voice streams, priorities, best-effort

Manageability

qLike DECT & 802-LANs

Special Advantages/Disadvantages

qAdvantage: extended QoSsupport, host/client and peer/peer, power saving, security qDisadvantage: future uncertain due to DECT-only devices plus

802.11a/b for data

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.73

RFID -Radio Frequency Identification (1)

Data rate

qTransmission of ID only (e.g., 48 bit,

64kbit, 1 Mbit)

q9.6 -115 kbit/s

Transmission range

qPassive: up to 3 m qActive: up to 30-100 m qSimultaneous detection of up to, e.g.,

256 tags, scanning of, e.g., 40 tags/s

Frequency

q125 kHz, 13.56 MHz, 433 MHz, 2.4 GHz,

5.8 GHz and many others

Security

qApplication dependent, typ. no crypt. on

RFID device

Cost qVery cheap tags, down to 1€ (passive)

Availability

qMany products, many vendorsConnection set-up time qDepends on product/medium access scheme (typ. 2 ms per device)

Quality of Service

qnone

Manageability

qVery simple, same as serial interface

Special Advantages/Disadvantages

qAdvantage: extremely low cost, large experience, high volume available, no power for passive RFIDsneeded, large variety of products, relative speeds up to

300 km/h, broad temp. range

qDisadvantage: no QoS, simple denial of service, crowded ISM bands, typ. one- way (activation/ transmission of ID) Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.74

RFID -Radio Frequency Identification (2)

Function

qStandard: In response to a radio interrogation signal from a reader (base station) the RFID tags transmit their ID qEnhanced: additionally data can be sent to the tags, different media access schemes (collision avoidance)

Features

qNo line-of sight required (compared to, e.g., laser scanners) qRFID tags withstand difficult environmental conditions (sunlight, cold, frost, dirt etc.) qProducts available with read/write memory, smart-card capabilities

Categories

qPassive RFID: operating power comes from the reader over the airwhich is feasible up to distances of 3 m, low price (1€) qActive RFID: battery powered, distances up to 100 m Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.75

RFID -Radio Frequency Identification (3)

Applications

qTotal asset visibility: tracking of goods during manufacturing, localization of pallets, goods etc. qLoyalty cards: customers use RFID tags for payment at, e.g., gasstations, collection of buying patterns qAutomated toll collection: RFIDsmounted in windshields allow commuters to drive through toll plazas without stopping qOthers: access control, animal identification, tracking of hazardous material, inventory control, warehouse management, ...

Local Positioning Systems

qGPS useless indoors or underground, problematic in cities with high buildings qRFID tags transmit signals, receivers estimate the tag location by measuring the signal's time of flight Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.76

RFID -Radio Frequency Identification (4)

Security

qDenial-of-Service attacks are always possible lInterference of the wireless transmission, shielding of transceivers qIDs via manufacturing or one time programming qKey exchange via, e.g., RSA possible, encryption via, e.g., AES

Future Trends

qRTLS: Real-Time Locating System -big efforts to make total asset visibility come true qIntegration of RFID technology into the manufacturing, distribution and logistics chain qCreation of "electronic manifests" at item or package level (embedded inexpensive passive RFID tags) q3D tracking of children, patients Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.77

RFID -Radio Frequency Identification (5)

Devices and Companies

qAXCESS Inc., www.axcessinc.com qCheckpoint Systems Group, www.checkpointsystems.com qGEMPLUS, www.gemplus.com/app/smart_tracking qIntermec/Intellitag, www.intermec.com qI-Ray Technologies, www.i-ray.com qRF Code, www.rfcode.com qTexas Instruments, www.ti-rfid.com/id qWhereNet, www.wherenet.com qWireless Mountain, www.wirelessmountain.com qXCI, www.xci-inc.com

Only a very small selection...

Prof. Dr.-Ing. JochenSchiller, http://www.jochenschiller.de/MC SS057.78

ISM band interference

Many sources of interference

qMicrowave ovens, microwave lightning q802.11, 802.11b, 802.11g, 802.15, Home RF qEven analog TV transmission, surveillance qUnlicensed metropolitan area networks q...

Levels of interference

qPhysical layer: interference acts like noise lSpread spectrum tries to minimize this lFEC/interleaving tries to correct qMAC layer: algorithms not harmonized lE.g., Bluetooth might confuse 802.11 Bluetooth may act like a rogue member of the 802.11 network

IEEE 802.15-2 discusses these problems

qProposal: Adaptive Frequency Hopping OLD

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