Telecooperation III –Chapter 3: Mobile Networksafn48922/downs/wireless/TK3-K3-MobNetSys.pdfJoe: 555-1287 Gotta remember to ... – Internal timer runs, connection maintained •

Telecooperation

Darmstadt University of Technology

Telecooperation Telecooperation III III –– Chapter Chapter 3:3:Mobile Mobile NetworksNetworks

Max Mühlhäuser

Copyrighted material; for TUD student use only

Mühlhäuser: Telecooperation III/3 - 2

Telecom & Telecom & WirelessWireless WorldWorld

wired networks (ITU-T) wireless networks (ITU-R)

wired mobile communication

switched networks broadcast networks

wirelesspt-2-pt

mobile networks positioning(GPS...)

TV Radio

analog/digital × terrestr./satellite

...

Telecommunications (ITU)

...

data diffusiondata diffusion: e.g.,: e.g.,RDSRDS--based pagingbased paging

−×− architecturecommunity(i.e.: band)

sovereign(mil, pol...)

long haul(ship...)

consumer

amateur

industrial(ISM)

business


Wireless ClassificationWireless Classification: : ArchitectureArchitecture(note: acronym / classification babylon reigns!)

1. Pico Network2. Trunked Mobile Radio System3. Paging Network4. cellular / PLMN (PLMTS)5. packet data (wWAN)6. satellite (!cellular)7. cordless Telephony (CT) ! wPABX8. wLAN9. broadcast networks (radio, TV...)10. ad-hoc net (packet radio PRN)

! subchapters

personal personal commcomm. (PCS), e.g.. (PCS), e.g.GSM1800GSM1800!!UMTSUMTS!!IMT2000IMT2000

mobile mobile broadband broadband (MBS),(MBS),e.g. e.g. HiperlanHiperlan, , wATMwATM

22--5 5 yearsyears::

++

++? ? wBroadcastwBroadcast ??

55--10+ 10+ yearsyears:: ??


1. 1. PiconetsPiconets / / ScatternetsScatternets

piconet A

e.g., Bluetooth: max. 8 active devices per piconet—one masterScatternet: several piconets with overlapping coverage

piconet B

?=

TDK's 8 node BT Access Point

BT & Internet:“Last Hop”


BluetoothBluetooth: Goals: Goals• Provide small, inexpensive, power-conscious radio system• Bluetooth says, „cables! Bah!“• Personal short-range ad-hoc networks• Device communication and cooperation• Not really intended as wLAN technology; rather: low volume

1. The cordless desktop(headset, loudspeacker... ! audio!)

2. Communicating Appliances(includes ad-hoc networking)

3. Bridging(cf. PC-Outlook ! GSM phone)


BluetoothBluetooth: : OriginOrigin• of technology:

– five founders: Nokia, Ericsson, Intel, IBM, Toshiba)– consortium (1000++)– cell phone industry + computer industry + ...– idea: advance „wireless car key“ chip („1$-world“) to appliances

• of name:– Danish king Bluetooth II (940-981)– Lived to a ripe old age (~ 70 years)– First baptized Danish king– Significance in this context?

• The „Blue“ in IBM?– Deep Blue– Big Blue…

• The Ericsson Scandinavian connection?


BluetoothBluetooth: “Vision”: “Vision”„goodbye cables ... hello cooperation

Joe: 555-1287

Gotta remember totell the pager Joe’snumber changed...

XX

X


BluetoothBluetooth: Vision: Vision, Future, FutureVision „Send & Forget“:

– like IP: no „ack/reply“– reliable care-takers??

Concerns about BT future:• frequency overlaps 802.11 standard

– „always on" may cause problems…– worries the FAA, may endanger aircraft

• definitely need integration w/ software, not just HW compatibility• 1Mb/sec isn't fast enough for some applications…• …and it isn't enough to enable truly cordless desk (USB, SCSI, etc.)• but next generation spec may hit 2-20Mb/sec


BluetoothBluetooth HardwareHardware• Predicted long term: < $5/unit• but first first products, e.g.:

– headset & base station: > 500 $

• Low-cost radio operates in 2.4GHz band• Maximizes international acceptance!• bandwidth ~1Mb/sec over several meters• Range can be extended with an external power amplifier• Up to 7 simultaneous links• ~75 hours voice, 3 months standby w/ 600mAh battery


BluetoothBluetooth: : ConfigConfig, „Radio“ Basics, „Radio“ Basics• Each piconet has one master and ≥ 7 slaves (mac addr. 000 … 111)• Master determines hopping sequence, slaves have to synchronize

– Look for access code (72 bit) = f(master-ID) in wake-up carrier– then: follow master’s hopping scheme

• Participation in a piconet = synchronization to hopping sequence• Scatternet - communication between piconets:

– devices jumping back and forth between the piconets– different MAC addr in different piconets– Device can be master in one piconet only

• “Radio” Layer: TDD, FH-CDMA (1600 hops/s: slot 625µs)– 79 (in countries .fr, .jp, .es: 23) frequencies (“hop carriers”)– 32 (…: 16) of them: “wake-up carriers”– Radio layer spec: details of GFSK, power, signal strength/tolerance etc.– Bands used (USA, most of Europe: 2.4 – 2.4835 GHz) etc.


LMPLMP

BBluetoothluetooth Protocol StackProtocol Stack

RadioRadio

BasebandBaseband

SpeechSpeechSync CtrlSync Ctrl

AT.AT.CmdCmd

SCOSCO

RFCOMMRFCOMM

OBEXOBEX

ObjObj--Exch.Exch.ApplAppl..objobj.push.push

synchronizsynchroniz..file transferfile transfer

TCSTCS--BinaryBinary

ACLACL

LMPLMPL2CAP L2CAP

SDPSDP

LMPLMP

Telephony Telephony ApplAppl..-- Cordless TelCordless Tel-- IntercommIntercomm..

HeadHeadsetset

PPPPPPIPIP

TCP/TCP/UDPUDP

FaxFaxDialDialUpUpNetNet

LANLANAcc.Acc. (all)(all)

HCIInterf.

MMEE


Bluetooth Protocol Stack Bluetooth Protocol Stack (2)(2)• HCI: Host Controller Interface: device " driver in PC

– may shield differences of USB, PCcard BT device etc. – position may vary dependent on HW/SW tradeoff

• radio, baseband: see below, voice (SCO) / data (ACL) links• Link Manager Protocol LMP responsible for SCO/ACL link mgmt.• L2CAP: logical link control & adaptation protocol: general API• TCS-bin (telephony control protocol specification binary)

common mgmt. for telephony applications• RFCOMM emulates serial link „cable“ (up to 60 logical links)• AT command emulation for modem compatibility• SDP (service discovery protocol) in later chapter• Mgmt. Entity ME provides overall config. Managment• OBEX (object exchange) is compatible w/ IrDA

– Object push, e.g., for biz card exchange– Synchronization: e.g., organizer and PC


BBluetoothluetooth BasebandBasebandCDMA, 1Mbps (per channel i.e. piconet), remember slot size 625 µs;

– Hop frequency changes per-packet if packet < slot– „multi-slot packets“: 3 or 5 slots (hop frequency unchanged)– TDD: all even-numbered slots reserved for master (except multi-slot)

• SCO (synch. connection-oriented) link, telephony: „reserve each n-th slot“• ACL (asynch. connectionless) links for everything else

BT device has 48bit address; first 24 (LAP lower addr. part) used to compute „Access Codes“ CAC and DAC (cf. address field in BT packets)

Use of ACs in three important phases of building a piconet:1. InquiryAC: General (GIAC) or Dedicated (DIAC, for device classes)

(initial broadcast addr. for „inquiry“ by future master in wake-up carriers) 2. DeviceAC: DAC ∈ reply-msg of reachable devices (or those of DIAC class)3. ChannelAC: CAC sent master ! chosen Piconet nodes, becomes piconet-AC(CAC derived from master‘s LAP, DAC from slave‘s LAP)


BBTT Device Connection StatesDevice Connection States• Standby – waiting to join a piconet (look for paging msg every 1.28s)• Inquire – looking for other Bluetooth devices• Page – connecting to a specific device• Connected – actively involved in a piconet• Hold – power conservation state

– Internal timer runs, connection maintained

• Park – power conservation state– Connection "broken„:

forgets member address, but can be reactivated

• Sniff – listen at reduced rate

StandbyStandby

InquiryInquiry PagePage

TransmitTransmitConnectedConnected

ParkPark HoldHold power conservation

idle

SniffSniff


Bluetooth MAC Bluetooth MAC layerlayer

• 68/72b access codes AC – for DAC and CAC:– ƒ(24bit-LAP) ! 64bit (ƒ such that robust, easy correlation)– +4bit-preamble (synchronization) [+4bit-trailer IF header follows]

• Error correction schemes: none, „1/3“ or „2/3“– 1/3: each bit individually repeated 3 times– 2/3: groups of ten bits always expanded to 15 bits (5bit-FEC)

• Header contains „link type“ i.e. packet class with or w/o payload, such as– ID (68 bit): IAC, DAC– POLL (126b, master polls slave), NULL (126b, ack only, nothing to send)– HV1/2/3 (hiFi voice, all 1-slot, SCO, reserves every 2nd/ 4th /6th slot), – DM 1/3/5 (data medium), DH 1/3/5 (3 and 5 are multislot), all ACL(HV1/2/3 payload uses FEC1/3, 2/3, and none; all have 240B payload)(DM uses FEC1/3, DH uses none)

access code packet header payload72 (68) 54 0-2745 bits


BluetoothBluetooth MACMAC layerlayer(note: comm.protocol is of class „stop-&-wait ARQ“ i.e. „ping-pong“ per packet)header contains, apart from link type:• MAC address: 000 … 111• Flow bit: tells other end to (temporarily) stop sending (overflow!)• ARQN: acknowledges last packet (pos./neg)• SEQN: alternates, needed to distinguish „resent copy“ from „new“• HEC: 8b header specific error check (cyclic redundancy check CRC)• ∑ 18bit ! FEC1/3 ! 54 bit

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

payload (0-2745b) may start with „payload header“:• HV packets have none, DM/DH have 2Byte, plus 2 CRC• DH5: 2B header, ≤339B data, 2B CRC ! 343B (=2744b) payload• DM5: 2B + ≤224B + 2B ! 228B=1824b, FEC2/3 (on 1830) ! 2745b

header:


IrDAIrDA ((compared compared to to BluetoothBluetooth))IrDA: advantages and disadvantages

– IrDA: Line of sight (LOS); BT: omnidirectional

– LOS ! „lowTech security for data transfer…“ (e.g., business cards)

– LOS inconvenient for Internet bridge solutions (walk to bridge?)

– Connected IrDA devices must remain relatively stationary

– IrDA has higher bandwidth than BT (115kbps ! 1 … 4 … 16M)

– Similar high-level standards (e.g., OBEX)

– But BT supports multipoint communication

– Current costs for IrDA deployment are much lower (< $2/unit)

Future: „dispersed light“? (research issues, energy vs. bandwidth, ...)

Electrosmog research very immature ! future, consequences?


2.2. TrunkedTrunked Mobile Radio SystemsMobile Radio SystemsCharacteristics:• typical application: short voice (/data) msg (half-duplex HDX?),

broadcast (point-2-multipoint PMP) + point2point (P2P)• typical community: closed user group (taxi, police, company...)preceeded by „PMR“ (private mobile radio):

– user group owns BTS (antenna tower!) ! bad frequency economy! MPT-1327 standard in GB ! world (D: Telecom „Checker“)

– shared ‚trunk‘ of frequencies, public provider for user groups– cheaper, higher throughput (, more features)– headquarter/switching ctr. of user group becomes ~standard node– cell based ! ≈roaming support (no handover needed: short msgs)– „organization channel“: digital signalling (S-Aloha) 1.2 kbps– analog transmission (PSK), 2.4 kbps data (fast-FSK)– MPT anywhere 80...900 MHz, checker 410-418 (up) / 420-428 (down)– P2P & PMP: several types (prio, normal, polled, ...), data/status...– may connect to fixed net („short call“: no handover)


Trunk: TETRATrunk: TETRA• TETRA: trans european trunked radio; fully digital; since ‘96/‘97

– FDD duplex-distance 10 MHz (or more in some countries), πDQPSK– bands, e.g., 380..390(up)/390..400 or: 410..420/420..430 or 870..888/915..933

– FDMA: 25kHz channels, TDMA: 4 slots (V+D only)– both „ad-hoc“ (no central station) and „infrastructure“ configurations supported– variant V+D: voice+data standard, replaces MPT-1327– variant PDO: packet data optimized: data only– data rate 36kbaud/s, raw 28.8 kbps; SNR-dependent rate:

• 7.2-28.8 raw, 4.6-19.2 / 2.4-9.6 data (lo/hi redundancy)– call types:

• P2P a) via BTS, b) from MS to MS (in proximity)!!• PMP (fast connect [no accept]),

HDX; a) normal b) w/ protocol c) listen-only• various features, gateways, ... (e.g., „emergency“: fast guaranteed connect)

– roaming/handover: limited (not in HLR/VLR sense: small roaming radius!);„cell reselect“ (~handover) automatic, but may cause interrupt for >300 ms

• police: might switch to more „secure“(?) Tetropol standard


Trunk: TETRA (2)Trunk: TETRA (2)TDMA frame hierarchy:• frame: 4 slots, i.e. max 4 channels per frequency• multiframes used to insert 1 „control frame“ after 17*4 frames• hyperframe for protocol design only (numbering scheme etc.)• 510 symbols in 14.17ms ! raw rate of 36k symbols /sec ! 28.8 kbit/s• 1 channel (slot): 7.2 kbps (TCH/S: traffic channel speech, TCH/7.2 data, ...)

hyperframe0 1 2 57 58 59...

0 1 2 15 16 17...multiframe

0 1 2 3

0 slot 509

frame

14.17 ms

56.67 ms

1.02 s

61.2 s

CF

Control Frame:system / signalling data


3.3. PagingPagingCharacteristics:• broadcast, pager (device) recognizes, filters, ‚displays‘ „its“ msgs.• unidirectional (but USA++: Motorola „Flex“ ! „ReFlex“: 2way)• usually, sender may access thru „other“ network (phone, Web...)• traditional: reachability restricted regions like ≈ city, province;• trend: roaming: user can „book“ different region (e.g., calls phone#)• handover: „no need“

message (! pager) classes:– cap code pager (tone): sender dials phone no., 1-2 digits added: cap code

• pager receives „its“ ID + cap code ! predef. sound (user interprets!)– voice: receives audio-msg., „expensive“ (bandwidth!)– digital display: receives sender‘s phone no. – or arbitrary numeric data

(note: num. code human-translated into text by „cool“ people, e.g.,D: „Scall“ ! „Scode“ (1187 ! c11 c87 in letter/syllable/...-matrix C))

– alphanumerical (cf. SMS)


PagingPaging (2)(2)• generations“ rather debatable:

– G1: analog, e.g., Eurosignal– G2: based on „Pocsag“– G3: Ermes in Europe (various in USA++ like SkyTel, Motorola: G2,3,4?)

• still in use: Eurosignal (F, CH, D) since 1974, 87 MHz– device beeps (blinks) only: „alert, call office“– BTS emits „call“: (sync-freq, f1, f2, ..., f6, pause), each 100ms ! 800ms– f1-f6 = „address of receiver“ ! beeps

• Pocsag‚ post office standardization advisory group‘ (british telecom)– 512 (...2400) bps, 32b-words; typical: 8 subgroups in system (~TDM)– (several) binary frames: [frame-sync, block-sync, block of 16 words]– 18bit address (part of frame 1) ! ~250k users * 8 subgroups

• public services, e.g. Cityruf (D), Scall (D), CallMe (A)(often: no receiver charge ! UbiComp relevance? or rather: SMS/UMTS?)

• private services, e.g. in hospitals (bidirectional?)


Paging Paging (3)(3)ERMES: digital, EU (memo of understanding in 30 countries)

– in D: 13 licences; (problem: some interference w/ CATV air freq.)– 6.25 kbps; access via center and ≥1 computer net (typical: email)– 4 service classes: tone, numeric (msg-size <16k), α−num (<9k), data (opt.)– coding may vary for different users / groups

• main features:– roaming (intelligence ∈ pager: „I‘m not in my region ! I will rebook“)– numbered messages– grouping (send msg. to group)– authentication of sender

Flex (Motorola):– 6.4 kbps (max.msg: 30k chars), 4bit checksum– approved ITU standard, US ! Europe (D, UK)– ReFlex extension: two-way– faster learning curve (more relevant in US since cell phone less advanced)

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Paging ValueAdPaging ValueAd, Market, MarketAdded Value increasingly important in wireless market:• Often: call center: voice!text (! pager)• Motorola: FlexServer (~unified msging): urgent email/call ! pager• Motorola. FlexScript (SDK), WAPlike for „thinnest of all clients“• 2 markets („systems“): cheap (kids/youth) - valueAdded (biz)

Future?– ReFlex because of 2way?– Satellite-based because of global coverage?– competitive or shrinking in light of SMS & UMTS?– broadcast-based (see subchapter)?

Note:– leader in wireless-data market– 2001: sales forecast 220 M devices (70M in US, ~20% annual growth)– chinese market grows by 5M/year currently


2Way Pagers & „2Way Pagers & „PushbackPushback““• 2way-pagers part of „pushback“ philosophy:

– „important event“ ! msg (e.g., news, email) to pager („push“)– user can request „more info“ etc. („pull“)

• example: © 1999 ProxiNet, Inc.


4. PLMN4. PLMNCharacteristics• origin ‚car phone‘ ! „mobile phone“, but increasing ‚data‘ component • first wide-spread cellular technologies (US: „cell phone“)• roaming + handover common today• European GSM standard dominates on global scale (future?)

analog: • NMT–450,-800 (nordic mob.tel; Ericsson 1981) scandinavia ! world• C-Netz (D 1985, A, ZA!, ...) ! D-Netz (still some use, „cheap“)• AMPS (USA 1979): still in wide use!

digital: present systems called 2nd generation(sigh! acronyms with no common definition ! no real meaning: personal/digital comm./cordless standard/sys/net: DCS, PCN, ...)

• UMTS & advanced current sys. (GPRS, EDGE, ...; IS-95+, -136+): 3rd gen.• weaknesses appear ! discussion about 4th gen.


PLMN (2)PLMN (2)• GSM as GSM900, DCS1800, PCS1900 (US); End of 2000:

>140 countries >400 operators (40% Eur.), >350M users (65% Eur.)• US standards as IS (interim standard) –54, -95, -135

– IS-54: D-AMPS, ! „USDC“ (~20 countries), see below– IS-95: „invented“ by Qualcomm

• „narrowband CDMA“, spread-spectrum• each station uses same chip (spread) code!!, difference: time shift• ! needs precise synchronization of BTSes (GPS+-based), small cells

– IS-136: digital signalling TDMA, closest to GSM– IS-95 &-136 & GSM coexist in 1850-1990MHz in US, all called PCS1900

(1910-1930 for unlicenced)• Japan:

– PDC (IS-54), 800 & 1500 MHz bands– PHS pers. handyphone sys.: TDD!! ! <3km reach!, HiQuality voice


AMPS, USDCAMPS, USDC

• analog ! no TDMA possible ! only 30kHz per channel (FM-voice)• 416 channels per operator (A,B), of which 21 are reserved for control• partly in-band signalling (net mgmt. protocol over traffic channel)

D-AMPS (USDC), based on IS-54:– coexists w/ AMPS (same band & same analog signalling)– 3slot-TDMA in 30kHz ! triple capacity


GSM GSM OverviewOverviewOrigin: Intl. Telecom. Union ITU ! Eur. branch CEPT ! groupe spéciale mobiletoday: a) european standards rather by ETSI (telecoms+vendors+...)

b) name change: global system for mobile communication

• frequencies: #890-915MHz; $935-960 (1710-85/1805-80; US: 19xx)• per frequency channel: 200kHz, 256kbps raw symbols + slot guard time

– 8 slots ! phys.channel: pair (freq. channel no. Cn; timeslot no. tm), tm=0..7– 32kbps raw symbols per channel; 24,7 kbps raw bits per channel– multiframes within (Cn, tm): 26 (or 51) slots; x-in26/51: logical channels– Full rate channel: 24 of 26 slots ! 22,8 kbps– Half rate channel: 12 of 26 slots ! 11,4 kbps– Full rate speech: 13kbps voice + 9,8 kbps FEC (forward error correction)– Full rate data: 2,4 / 4,6 / 9,6 kbps plus CRC plus FEC

(CRC: cyclic redundancy check: checksum)


GSM GSM ArchitectureArchitecture

SS#7

PLMN (e.g. D1, Eplus)

ISDN &phone

(=“PSTN”)

datanetworks

etc.

MSC

IWF

net&switching subsys NSSradio subsystem RSS wired networks

BSC/BSS: base station controller / subsystemMSC: mobile switching center (G:gateway)EIR: equipment identity registerAUC: authentication ctr.

OMC: operation&mgmt. centerIWF: interworking function SS#7: signalling system no. 7(intl. standard for dialing, mgmt., ...)

…MS MS

BSS

…

BTS

BTSBSC

GM

SC

HLRHLR HLRVLR

MSC

EIR

AUC

OMC

operation subsys OSS

Um

A

Abis

O

interfaces:A: 64kbpsAbis: 16kUm: (below)


GSM Air Interface Um: GSM Air Interface Um: Data Data RateRate• remember: TDMA: 8 slots, FMDA: 2* 124 (DCS1800: 374) *200kHz• Layer 1: data rate?? look at time slot (length: 577 µs)

– carries „bursts“; for „normal bursts“ (channel in operation):

– 2*12 frames w/ 8 traffic slots, 13th/26th frame w/ 8 „associated“ slots

! raw rate 24/26 of (114b per (8*577µs)) = (114*12) / (8*577*13*10-6) ≈ 22.8 kbps

– typical packet size: 456 bits (= 8 blocks of 57 bits ^= 20ms, see next slide)

– interleaving of blocks&bits (e.g.: bit 1-8 of 456 ! bit 1 of blocks 1-8 etc.)

Note: GSM channel always frequency ch. number Cn plus timeslot no. tn (Cn, tn)

546.5 µs577 µs

tail user data TrainingSguardspace S user data tail

guardspace

3 bits 57 bits 26 bits 57 bits1 1 3


GSM Frame GSM Frame HierarchyHierarchy

0 1 2 2045 2046 2047...hyperframe

0 1 2 48 49 50...

0 1 24 25...

superframe

0 1 24 25...

0 1 2 48 49 50...

0 1 6 7...

multiframe-26

frame

burstslot

577 µs

4.615 ms

120 ms

235.4 ms

6.12 s

3 h 28 min 53.76 s

multiframe-51

or:

or:


GSM GSM logical channel data rateslogical channel data ratesData rate for logical channel LC?

– how many bursts out of 26 (51) in given (Cn, tn) are used for LC?may be 24in26 (full rate traffic), 1in26, xin51

– „data“ bit percentage („raw“ msg. usually 8 blocks, 4 bursts, 456 bits)?note: for 24in26-types, 4 bursts take 1/6 in multiframe26, i.e. 20ms

n data/voice bits m CRC/FEC bits

114 bits

456 bits as

114 bits– e.g., voice data rate: 13 kbps (samples of 20ms ! 260 bits)

Note:– GSM-„vocoder“: LPC : linear prediction codec

with long-term prediction LTP (of waveform) – plus „error correction“ called RPE (regular pulse excitation)

– e.g., data channel: 9.6 kbps ! 192 bit in 20 msin RLP (radio link protocol) frame: 240 bit (12 kbps)

– e.g., fast signalling channel: 9.2 kbps ! 184 bit in 20 ms

114 bits 114 bits 456 bits (in 20ms for „full rate“)


GSMGSM Data bits Data bits !!!!!!!! Channel bitsChannel bits

50 most important C 132 medium important T 78 least

important

(2,1,5) convolution code: double size (½ rate) ! 2*189 = 378 bit 78 leastimportant

260 bits (50/132/78) +C: 3b CRC +T: 4*zero tail = 267

456 bits ! 8 * 57 bits(4 bursts)

4*60 + T: 4b tail = 244 (24 Byte data in 20ms ! 9.6 kbps)

456 bits ! 8 * 57

2-3B RLP (radio link prot.) header, 3B CRC-Check, 24B(+1) Data = 240bit T

(2,1,5) convolution code: double size (½ rate) ! 2*244 = 488 bit

„code puncturing“: 32 of the redundantbits erased (receiver inserts random)

Full rate speech:

TCH/F9.6 data (non-transparent; for transparent mode: fill bits instead of RLP header):

244 bits + T: 4b tail = 228

456 bits ! 8 * 57

Typical signalling channel:

(2,1,5) convolution code: double size (½ rate) ! 2*228 = 456 bit

184 most important T40 bit CRC


GSM Air Interface: GSM Air Interface: ChannelsChannels

Channel (Group) Name mf use raw data ∈ 456 dat.rate dir remarksTCH: Traffic ChannelTCH/FS speech full rate 24in26 22,8 260 13 %

TCH/F9.6 9.6kbps data full rate 24in26 22,8 240/192 12/9,6 % RLP rate 12; user rate 9,6TCH/F4.8 4.8kbps data full rate 24in26 22,8 120/96 6/4,8 % 120bit +32 tail; 1/3 convol.rateTCH/H4.8 4.8kbps data half rate 12in26 11,4 240/192 6/4,8 % (even or odd frames only)DCCH: Dedicated Control Channel (for (pre/post)connected MS)SACCH/T Slow Associated w/ T 1in26 0,95 0,383 % slot 13, sys/signal-power infoFACCH Fast Ass. (in TCH slots) 24in26 22,8 184 9,2 % shortterm (for handover etc.)SDCCH Stand-Alone 4in51 1,94 184 0,782 % pre/post connection info/mgmtSACCH Slow Assoc. w/ SDCCH 4in102 0,97 184 0,391 % slot 13, sys/signal infoCCCH: Common Control Channel (for new/nonconnected MS) such as:PCH Paging Channel MS wakeUp! (call/handover)AGCH Access Grant reply to RACH-msg.

≤24,7 $ Slotted-Aloha among MSesBCCH: Broadcast Control Channel (Broadcast of Cell Info to all) such as:BCCH 4in51 0,95 184 0,782 # net/cell ID, options, ....SCH(synch.),FCCH(freq.correct.) # adjusts TimeBase / Freq.

#

n.a.: special bursts5in51 p. Ch.

RACH Random Access 27or 51in51 n.a.: 8bit-slots

Σ: 12or 36in51

5,81/ 17,44 184

2,35/ 7,04


GSM ServicesGSM ServicesService: „communication and more“• Three classes: bearer s., tele-s., supplementary s.• Bearer Services: make use of logical channels

– voice, circuit-switched data (≤ 9.6), packet-switched data (≤ 9.6)• TeleServices: „complete“ application by net operator

– voice: mobile telephony, emergency-no. (112: all Europe), multiple no.‘s– non-voice: faxG3, voice mailbox, SMS– note: efficient vocoder ! modem‘s won‘t work!

• Supplementary S.: cf. ISDN (rerouting, CLIP/CLIR, auto-callback, ...)

GSM-PLMNtransit

network(PSTN, ISDN)

source/destination

networkTE TE

bearer services

tele services

R, S (U, S, R)Um

MT

MS


MS:

GSM GSM Mobile stationMobile station (MS)(MS)• Terminal for use of GSM services, comprises

– MT (Mobile Terminal):• offers common functions used by all services the MS offers• corresponds to the network termination (NT) of an ISDN access• end-point of the radio interface (Um)

– TA (Terminal Adapter):• terminal adaptation, hides radio specific characteristics• data terminal w/ ISDN capabilities may connect directly to S-IF

– TE (Terminal Equipment): no more GSM specific functions• peripheral device of the MS, offers services to a user• data terminal: 300-9600 (14.4k) bps, asy/synch.

– SIM (Subscriber Identity Module – separate part):• personalization of the mobile terminal, stores user parameters

R S UmTE TA MT


GSM „User Plane“GSM „User Plane“• data services: various rate adaptations RAn (overhead bandwidth!)• shown here: „non-transparent“ example (employs RLP)• application-specific L.2 connects terminals (TE); RA0 only for asynch. data• 80bit-blocks on 8/16bps <> 60bit-blocks on radio <> nn-bit (user data rate)

RA1(+0)

RA2

RA1(+0)

RA2

RA1‘

(±FEC)

L.2 RLP

22.8 kbps

S Um A

64 kbps

TA MT BSS (BTS/BSC) MSC/IWF

TE

R

user rate 64 kbps

8/16 8/16 6/12(±FEC) RA2

8/16 6/12

radio

RA1‘ RA1 RA1

RA2

modemRLP L.2

ISDN or PSTN

64 kbps

TE

TE


PCM

GSM „GSM „Signalling Signalling Plane“ Plane“ ProtocolsProtocols

• CM (call mgmt.) = CC (call control) + SS (suppl. services) + SMS• MM (mobility mgmt): localization & security (involves HLR / VLR)• RR (radio resource mgmt): radio connection mgmt., handover• L2-protocols RLP, LAPDm, LAPD, SS7-MTP: all variants of HDLC• BTSMgmt. & BSS-ApplicationPart GSM specific• ISDN-UserPart extended by Mobile Application Part to cope w/ mobility• SS7: world-wide telephone signalling system (called „no.7“)

CM

MM

RR

MM

LAPDm

radio

LAPDm

radio

LAPD

PCM

RR’ BTSM

CM

LAPD

PCM

RR’BTSM

16/64 kbit/s

Um Abis A

SS7

PCM

SS7

PCM

64k/ 2.048 Mbps

MS BTS BSC MSC

BSSAP BSSAP MAP

ISUP

ISDN/PSTN

L.3

L.2

L.1


GSM GSM Protocol ExampleProtocol Example: : Call Call SetupSetupBTSMS

paging requestchannel requestimmediate assignmentpaging responseauthentication requestauthentication responseciphering commandciphering completesetupcall confirmedassignment commandassignment completealertingconnectconnect acknowledgedata/speech exchange

MTC BTSMS

channel requestimmediate assignmentservice requestauthentication requestauthentication responseciphering commandciphering completesetupcall confirmedassignment commandassignment completealertingconnectconnect acknowledgedata/speech exchange

MOC„mobileterminatedcall“

„mobileoriginatedcall“


GSM: GSM: added valueadded value, , problemsproblems• SMS: short msg service

– „2way-paging“, 160B messages, packet-switched (SMS centre)– uses SACCH, SDCCH (works while connection active)

• SIM-card: ~ unique feature, widely distributed– seals identity, key; core of „personal mobility“

• authentication (user: PIN, net: challenge/response)• encryption: session key generation• anonymity: temporary identity TMSI (note: 1of6 GSM „identities)

– plus memory (SMS, ...) plus applications (applets etc. – „in principle“)

• retain (some of the major) problems:– low data rates, overhead– considerable delays (interleaving! may be well >100ms)– potential of SIMcards hardly exploitable


Data services in GSM Data services in GSM • Data transmission standardized with only 9.6 kbit/s

– advanced coding allows 14,4 kbit/s– not enough for Internet and multimedia applications

HSCSD (High-Speed Circuit Switched Data)– already standardized– bundling of several time-slots to get higher AIUR

(Air Interface User Rate), e.g., 57.6 kbit/s using 4 slots, 14.4 each– advantage: ready to use, constant quality, simple– disadvantage: channels blocked (no voice transmission; cost!)– disadv.: equipment not ready for simultaneous xmit/rcv ! ≤4 (2?) slots

AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.44.8 19.6 2 1

14.4 3 119.2 4 228.8 3 238.4 443.2 357.6 4


Data services in GSM IIData services in GSM IIGPRS (General Packet Radio Service)

– packet switching– using free slots only if data packets ready to send

(e.g., 115 kbps using 8 slots temporarily: 8*14.4)– standardization 1998, introduction 2000?– advantage: one step towards UMTS, more flexible– disadvantage: more investment needed

• GPRS network elements– GSN (GPRS Support Nodes): GGSN and SGSN– GGSN (Gateway GSN)

• interworking unit between GPRS and PDN (Packet Data Network)– SGSN (Serving GSN)

• supports the MS (location, billing, security)– GR (GPRS Register)

• user addresses


GPRS quality of serviceGPRS quality of service

Reliabilityclass

Lost SDUprobability

DuplicateSDU

probability

Out ofsequence

SDUprobability

Corrupt SDUprobability

1 10-9 10-9 10-9 10-9

2 10-4 10-5 10-5 10-6

3 10-2 10-5 10-5 10-2

Delay SDU size 128 byte SDU size 1024 byteclass mean 95 percentile mean 95 percentile

1 < 0.5 s < 1.5 s < 2 s < 7 s2 < 5 s < 25 s < 15 s < 75 s3 < 50 s < 250 s < 75 s < 375 s4 unspecified


GPRSGPRS:: protocolprotocols, s, interfacesinterfaces

apps.

IP/X.25

LLC

GTP

MAC

radio

MAC

radioFR

RLC BSSGP

IP/X.25

FR

Um Gb Gn

L1/L2 L1/L2

MSBSS SGSN GGSN

UDP/TCP

Gi

SNDCP

RLC BSSGP IP IP

LLC UDP/TCPSNDCP GTP

MS BSS GGSNSGSN

MSC

Um

EIR

HLR/GR

VLR

PDN

Gb Gn Gi

SGSNGn


33rdrd Generation PLMN (3G)Generation PLMN (3G)1G: analog, 2G: digital (voice, low bandw. data, circuit-centric)3GVision: faster, better, „everything“ (public), „everyone“ (worldwide)• ITU renamed „FPLMN (f=future)“ into „IMT-2000“ (m=mobile)• ETSI started UMTS to succeed (success of) GSM• Today in IMT-2000: many players, competition

– Organizations (all „worldwide“) such as• 3GPP (3G Partnership Prog.):

Japan (Arib, TTC)& Korea (TTA) with Europe (ETSI), and others• 3GPP2: Japan and Korea (same bodies) with US (TIA), and others• Upcoming Partnerships of Developing Countries• DECT („we know how to do TDD“)

– Air Interfaces: CDMA-FDD, CDMA-TDD, CDMA2000 (evol. from IS95)– Core Networks: SS7-like (GSM), ANSI, Internet-IP (!)

• Summary: „forget the U in UMTS“


UMTUMTS, S, architecturearchitectureUMTS: learning from enhancements of GSM

• EDGE (Enhanced Data rates for GSM Evolution): GSM up to 384 kbps• CAMEL (Customized Application for Mobile Enhanced Logic)• VHE (virtual Home Environment)

– fits into GMM (Global Multimedia Mobility) initiative from ETSI– requirements

• min. 144 kbit/s rural (goal: 384 kbit/s) at up to 500 km/h• min. 384 kbit/s suburban (goal: 512 kbit/s) at up to 120 km/h• up to 2 Mbit/s city at up to 10 km/h

– main standard today: UTRA (UMTS Terrestrial Radio Access)

UTRANUE CN

IuUu

UTRAN: UTRA Net, i.e.– cell level mobility; – Radio Net Subsystem (RNS)

UE: (User Equipment)CN: Core Network: inter sys handover

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ion

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-49

UMTS

& I

MT

UMTS

& I

MT --

2000

2000


UMTS FDD UMTS FDD frame structureframe structure

0 1 2 69 70 71...superframe

0 1 2 13 14 15...frame

pilot TPC TFIslot

625 µs

10 ms

720 ms

data

pilot

uplink DPDCH

uplink DPCCH

downlink DPCHTPC TFI data

625 µs

625 µs

DPCCH DPDCH

W-CDMA• 1920-1980 MHz uplink• 2110-2170 MHz downlink• chipping rate:

4.096 Mchip/s• soft handover• localization of

MS (ca. 20 m precision)• complex power control

(1600 power control cycles/s)

TPC: Transmit Power ControlTFI: Transport Format IdentifierDPCCH: Dedicated Physical Control ChannelDPDCH: Dedicated Physical Data ChannelDPCH: Dedicated Physical Channel


UMTS TDD UMTS TDD frame structureframe structure

0 1 2 13 14 15...frame

data midample dataslot

625 µs

10 ms

traffic burstGP

W-TDMA/CDMA• 2560 chips per slot• symmetric or asymmetric

slot assignment to up/downlink• tight synchronization needed• simpler power control

(100-800 power control cycles/s)

GP: Guard Period


5. Packet 5. Packet DataDatapast:• US networks and early GSM: (almost) no data support• connection-based structure /tariffs of voice-centric PLMNs! dedicated data networkspresent:• declining importance

– GSM, UMTS, paging, trunc: all include data– CDMA etc.: more flexible, (some) volume based capacity assignment

• tariff of non voice net? (+: volume based; -: lower learning curve)• related to or intertwined with either mobile phone or paging sys.future:• UMTS, IMT2000: vision is to fully integrate network „types“• but: competition, non licenced: may survive• US metropolitan? ! world? „overlay network“ concept (see ch. 1)


Packet Packet DataData: a : a few examplesfew examplesD (Telecom): Modacom – basically end-of-lifeEricsson: Mobitex• 19.2 „virtual connection“: wired-PC ! (MOX-MHX-MOX)-BS !mPC• mPC (mobile) has „radio modem“; infrastructure: MOX/MHX & BSIBM&Motorola (´98: bought by AmericanMobile): ARDIS• initially planned for „service dispatch“• now: 19.2k two-way; 400 metro areas in US (90% biz coverage!)Paging-like, e.g.:• MobileComm, Nextel, EMBARC, RadioMail (on Ardis or Ram)• usually have „delivery priorities“ (asap, express (1h), prio (15min.)...)• RAM mob.data (by Ram broadcasting, NY, based on Mobitex)• SkyTel satellite paging, ! 2wayMetricom: towards ad-hoc, see point 10


Packet Packet DataData: CDPD: CDPDUS pecularity!CDPD = cellular digital packet data• provides for IP connectivity• „channel stealing(sniffing)“: use free capacities in AMPS voice• 19.2kbps, authentication & all data routed through home (HLR-like)• 3 types of connectivity:

– connection-less / -oriented: no guaranteed delivery, no ACK– connection-oriented w/ ACK and flow control

• Architecture: „Mobile Data“ Components MD– End System ES, Base Station BS, Intermediate Sys. IS, Gateway GW– BS, IS co-located w/ AMPS components

Channel allocations

list of hop channels

list of neighbours

MD-ISMD-BSMD-ES

MD-GWMD-ES Data

Net

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Pack

et

Pack

et D

ata

Data

(an

d Al

tern

atives

)(a

nd A

lter

native

s)


6. 6. Satellite Satellite SystemsSystemstrends, reminders, categories:• trends:

– today: phone, paging, ... (sat. not architecture category in our sense?)– tomorrow: integrated services, overlay nets

• orbit categories: GEO ! MEO (=ICO intermediate, circular) ! LEO(HEO: highly elliptical irrelevant here)

• connection categories (=different nets, all evolve towards digital):– P2P-immobile: Intelsat etc.: „big cable in the sky“ (600+ phone, 10+ TV)– PMP-immobile: TV (100+ channels; big-dish transmission trucks)– P2P mobile: personal comm.– many community specific sys (maritime, mil., ...)

• history: ‘57: Sputnik, ‘65: Intelsat (240 phone, 1 TV)‘82 Inmarsat-A (mobile phone cost 100.000 DM)‘98 Iridium (77 ! 66 satellites ! †) !!!


Satellite Satellite Systems: TermsSystems: Terms

Inter Satellite Link (ISL)

Gateway Link (GWL)

footprint

small cells(spotbeams)

GWL

MUL

base stationor gateway

transponder (up- + down-link + „freq.translation“, forone connection (e.g., A+V)

VSAT: very smallaperture terminal(mobile Snd/Rcv)

typical bands(up/down):C: 6 / 4 GHzKu: 14 / 12 GHzKa: 30 / 20 GHz

uplink: ~ focussed beamdownlink: ~ broadcast

ε

Mobile UserLink (MUL)

elevation

satellite sophistication:– amplification ! focus of beams (spotbeam)– inter-sat routing (cheaper terrest. equipment, lower latency)


Satellite Satellite Systems: G/M/L EOSystems: G/M/L EOGEO:

– useless near poles(elevation should be >10°)

– high latency (~250 ms)– large footprint (<34% of earth)

! no roaming / handover– high energy / large dishes– very few satellites

LEO:– sat visible for 20-40 min.– ! roaming/handover mandatory,

• even for gateways• within sat, if spotbeam changes

– latency 5-10ms like long-distance earth– cheap mobiles, expensive orbital equipment

MEO/ICO: compromise?– latency ~70 ms, <10 satellites– energy? sat. sophistication?

earth

km35768

10000

1000

LEO (Globalstar,

Teledesic)

HEO

inner and outerVan Allen belts

MEO (ICO)

GEO (Inmarsat)

LEO registers (cf. GSM):- HLR: static data- VLR: (last) user location- SUMR:

sat./user mapping (SUM)+ sat. positions


Satellite Satellite LEO / MEO LEO / MEO comparisoncomparisonIridium Globalstar ICO Teledesic

# satellites 66 + 6 48 + 4 10 + 2 288altitude(km)

780 1414 10390 ca. 700

coverage global ±70° latitude global globalmin.elevation

8° 20° 20° 40°

frequencies[GHz(circa)]

1.6 MS29.2 ↑19.5 ↓23.3 ISL

1.6 MS ↑2.5 MS ↓5.1 ↑6.9 ↓

2 MS ↑2.2 MS ↓5.2 ↑7 ↓

19 ↓28.8 ↑62 ISL

accessmethod

FDMA/TDMA CDMA FDMA/TDMA FDMA/TDMA

ISL yes no no yesbit rate 2.4 kbit/s 9.6 kbit/s 4.8 kbit/s 64 Mbit/s ↓

2/64 Mbit/s ↑# channels 4000 2700 4500 2500Lifetime[years]

5-8 7.5 12 10

costestimation

4.4 B$ 2.9 B$ 4.5 B$ 9 B$


Special: TFTSSpecial: TFTSTerrestrial Flight Telephone System• 1670-1675 MHz ↑, 1800-1805 ↓, 4-slot TDMA• cell size ~240km• 9.6 kbps voice codec• 4.8 kbps fax


InletInlet: Global : Global PositioningPositioningGPS, GLONASS, ...: increasing imporance (UbiComp location awareness)• not part of classification (broadcast, one-way)• GPS: DoD sat‘s emit messages [satID, pos., timestamp] (precise clock)• 4 equations, 4 variables: x,y,z, δ (clock bias of receiver)• 4 satellites, speed-of-light

→ compute receiver position• plausibility, earth geometry

→ 3 sat‘s needed only• GPS: DoD-induced „error“

! ~ 10-100m precision• DGPS („differential“):

– non-mobile station (d<100km)– known pos. ! compute time– xmit !mobile ! known δ– 100km? ! same 3 satellites


7. 7. Cordless Telephony Cordless Telephony CT: CT: HistoryHistory• CT0: US, FarEast; radio interface f. home base stations; analog FM.

– first: „base station @ phone plug“; no authentication & security– analog FM 1.6/4.7 MHz, 8x25kHz (FDMA/FDD like all analog)

• CT1: Europe, authentication, 914-915 MHz↑, +45↓ (40*25kHz-ch.)– CT1+: Germany, double capacity (885-887: 2MHz)

• CT2: UK!ETSI, early 90s, digital, wPABX, limited roaming– 864-868 MHz (40*100kHz); TDD; GFSK– 32kbps-ADPCM voice ! 72kbps channels– UK vision: Telepoint

• public operators install poletop base stations• e.g., on public phones, in airports, ...• ! cheap mobile phone system, mainly outgoing calls

(„stop car near public phone“, ...)• 4 operators in UK, F: BiBop, D: Birdie• never really took off


CT CT PresentPresentEvolution CT ! „low mobility services“ (incl. IMT2000 integration)• DECT: Digital European (! „Enhanced“) Cordless Telecomm.

– ETSI standard (ETS 300.175-x) is for „air interface“– potential competitor of cellular systems in some cases (cf. Telepoint)– 1880-1900 MHz as 10 1728kHz spaced carriers, GFSK– per carrier: 2*12 (TDD) 10ms-slots ! 120 FDX channels– 32 kbps ADPCM voice (GSM: 13), ≤ 10*25.6 k data (mux) per direction– range: ca 50 m in buildings, 300 m open space

• PHS: Personal Handyphone System (Japan)– more outdoor support (densely pop. cities!)– success (7M users), 32 kbps data

• US: PWT (personal wireless telephony)– QPSK instead of common GMSK– unlicenced 1910-1920, extension to licenced/PCS band! (1850 .... 1990)


DECT architecture reference modelDECT architecture reference model• Portable „application“ (PA) + ... „termination“ (PT) = PP (port. part)• Fixed radio termination FT in ... „system“ FS: FP (fixed part)• ...and much more typical european terminology inflation

globalnetwork

localnetwork

localnetwork

FT

FT

PTPA

PTPAVDB

HDB

D1

D2

D3D4


DECT time multiplex frameDECT time multiplex frame

slot

sync

A field

DATA

DATA64

C16

DATA64

C16

DATA64

C16

DATA64

C16

B field

D field

1 frame = 10 ms

12 down slots 12 up slots

0 419

0 31 0 387

0 63 0 319

protected mode

unprotected mode

simplex bearer25.6 kbit/s

32 kbit/s

420 bit + 52 µs guard time („60 bit“) in 0.4167 ms

guard

X field 0 3A: network controlB: user dataX: transmission quality


physical layer

medium access control

data linkcontrol

data linkcontrol

networklayer

OSIL1

OSIL.2

OSIL.3

U-PlaneC-Planesignalling,interworking

applicationprocesses

DECT reference modelDECT reference model: Air IF: Air IF• several services in C(ontrol)/U(ser)-plane • close to OSI reference model• management plane across all layers• Physical layer

– (de)modulation, generation of physicalchan. structure (guaranteed throughput)

– controlling of radio transmission• chan. assignment on MAC layer request• detection of incoming signals• sender/receiver synchronization• collecting status info. for mgmt plane

• MAC layer (basic services)– (de)activating physical channels– multiplexing of logical channels (P: paging,

I: user data, C: signalling, Q: broadcast, ...)– segmentation/reassembly– error control/error correction

man

agem

ent


DECT DECT Air IF: Air IF: further layersfurther layers• Data link control layer DLC

– create / retain reliable connections mobile term. ↔ base station – 2 DLC protocols for C-Plane

• connectionless broadcast service: paging functionality• „Lc+LAPC“: in-call signaling (cf. ISDN-LAPD), adapted to DECT-MAC

– several services specified for the user plane (U-Plane)• frame relay / frame switching : simple / time bound packet Xmission• error correcting Xmission: FEC (delay critical time bounded services)• bandwidth adaptive transmission• „null“ / „escape“ services: direct MAC access / future enhancements

• Network layer (cf. ISDN Q.931, and GSM-04.08)– request/check/reserve/ctrl/release resources @ PP & FP– resources for both wireless & DECT-fixedNet connection– call control: setup, release, negotiation, control – call independent services: call forward, redirect, accounting, ...– mobility mgmt: ID mgmt, authentication, location register mgmt


DECT DECT EnhancementsEnhancements• Several „DECT Application Profiles“ in addition to DECT spec.

– GAP (Generic Access Profile) standardized by ETSI in 1997• assures interoperability between DECT equipment of different

manufacturers (minimal requirements for voice communication)• enhanced mgmt capabilities thru FixedNet: „CT Mobility“ (CTM)

– ! CTM Access Profile (CAP): support for user mobility

– Interworking Profiles: with GSM (GIP), ISDN (IAP, IIP)– Radio Local Loop Access Profile (RAP): public telephone service– Radio Packet Service plus Multimedia Access Profile

(1.88-1.90 GHz res., 32k…2Mbps, …20m „direct link acc. DLA“ intracell)

DECTbasestation

GAP

DECTCommonAir Interface

DECTPortable Part

fixed network


8. 8. wLANswLANs

– Pico vs. wLAN: desktop ... building ... metroArea– adHoc vs. wLAN: wLAN standards today „~support“ adHoc config,

but adHoc networking needs more– LowMob: different past, different mid term future (<> UMTS?)

• wLAN perspective:– past: different proprietary solutions– present: IEEE802.11 (multi)standard– mid term future: HiperLan <> wATM <> ??– longer term future: MBS; (MBS & IMT2000 & broadcast ! ???)

• wLAN frequencies:– unlicenced ISM band (industry, science, med.) [PCS: licenced extension]– ISM: 0.9 (not europe!) / 2.4 / 5.8 / ~60? MHz

PicoNetadHocNet

CT!LowMob

wLAN


wLANwLAN „„cellscells““

HUBHUB

„cell“ 2

HUB

„cell“ 3

„cell“ 1

FH: same pseudo random hopping per domain (cf. Bluetooth)DS: standard chipping sequence; different time shift, stations „know“ domain

Bridge

Bridge


IInfrastructurenfrastructure vs. vs. AAddHHococ NNetetinfrastructurenetwork

ad-hoc network

APAP

AP

wired network

AP: Access Point


Distribution System

Portal

802.x LAN

AccessPoint

802.11 LAN

BSS2

802.11 LAN

BSS1

AccessPoint

802.11 802.11 –– Infrastructure NetInfrastructure NetStation (STA)

– terminal with access mechanisms to the wireless medium and radio contact to the access point

Basic Service Set (BSS)– group of stations using the same

radio frequencyAccess Point

– station integrated into the wireless LAN and the distribution system

Portal– bridge to other (wired) networks

Distribution System– interconnection network to form

one logical network (EES: Extended Service Set) based on several BSS

STA1

STA2 STA3

ESS


wLANwLAN: 802.11, : 802.11, HiperlanHiperlanIEEE 802.11, Hiperlan (ETSI)• ISM bands plus 16 & 60 GHz, IR• 10-100 Mbps (multimedia!), isochronous support (voice++)• both variants of „spread spectrum“ continue to exist• „infrastructure“ and „ad-hoc“ Nets (Hiperlan: MS = router!)• IEEE802.11 challenge: transparent introduction into “802 family“• roaming: access point learns about „its“ MSes (infrastr. net)

802.2 Data Link

802.10 Security

802.11 wireless MAC 802.3 CSMA/CD MAC

ISM | IR | 16GHz | 60 GHz 10BaseT | 10BaseF | ……other

802-LANs

(z.B.)


802.11 802.11 -- Layers and functionsLayers and functionsPLCP Phys. Layer Convergence Prot.

– clear channel assessment signal (carrier sense)

PMD Physical Medium Dependent– modulation, coding

PHY Management– channel selection, MIB

Station Management– coordination of all mgmt functions

PMD

PLCP

MAC

LLC

MAC Management

PHY Management

MAC– access mechanisms, fragmentation,

encryption MAC Management

– synchronization, roaming, MIB, power management

PHY

DLC

Stat

ion

Man

agem

ent


802.11 802.11 -- Physical layerPhysical layer• 3 versions: 2 radio (typical 2.4 GHz), 1 IR

– data rates 1 or 2 Mbps ! 3 (FHSS) & 11 (DSSS) Mbps• FHSS (Frequency Hopping Spread Spectrum)

– spreading, despreading, signal strength, typ. 1 Mbps– min. 2.5 frequency hops/s (USA), two-level GFSK modulation

• DSSS (Direct Sequence Spread Spectrum)– DBPSK modulation for 1 Mbps (Differential Binary Phase Shift Keying),

DQPSK for higher rates (Differential Quadrature PSK)– preamble and header of a frame is always transmitted with 1 Mbit/s,

rest of transmission 1 or 2 Mbps– chipping sequence: +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1 (Barker code)– max. radiated power 1 W (USA), 100 mW (EU), min. 1mW

• Infrared– 850-950 nm, diffuse light, typ. 10 m range– carrier detection, energy detection, synchonization


FHSS PHY packetFHSS PHY packet formatformat• Synchronization

– synch with 010101... pattern• SFD (Start Frame Delimiter)

– 0000110010111101 start pattern• PLW (PLCP_PDU Length Word)

– length of payload incl. 32 bit CRC of payload, PLW < 4096• PSF (PLCP Signaling Field)

– data of payload (1 or 2 Mbit/s)• HEC (Header Error Check)

– CRC with x16+x12+x5+1

synchronization SFD PLW PSF HEC payload

PLCP preamble PLCP header

80 16 12 4 16 variable bits


DSSS PHY packetDSSS PHY packet formatformat• Synchronization

– synch., gain setting, energy detection, frequency offset compensation• SFD (Start Frame Delimiter)

– 1111001110100000• Signal

– data rate of the payload (0A: 1 Mbit/s DBPSK; 14: 2 Mbit/s DQPSK, ...)• Service / Length

– future use, 00: 802.11 compliant / length of the payload• HEC (Header Error Check)

– protection of signal, service and length, x16+x12+x5+1

synchronization SFD signal service HEC payload

PLCP preamble PLCP header

128 16 8 8 16 variable bitslength

16


802.11 802.11 -- MAC layer I MAC layer I -- DFWMACDFWMAC• Traffic services

– Asynchronous Data Service (mandatory)• exchange of data packets based on “best-effort”• support of broadcast and multicast

– Time-Bounded Service (optional)• implemented using PCF (Point Coordination Function)

• Access methods: DFWMAC = Distributed Foundation Wireless MAC(distributed „D“ or polling based „P“ access ctrl. functions DCF/PCF)– DFWMAC-DCF CSMA/CA (mandatory)

• collision avoidance via randomized „back-off“ mechanism• minimum distance between consecutive packets• ACK packet for acknowledgements (not for broadcasts)

– DFWMAC-DCF w/ RTS/CTS (optional)• avoids hidden terminal problem

– DFWMAC- PCF (optional)• access point polls terminals according to a list


802.11 802.11 -- CSMA/CA CSMA/CA detaildetail• CSMA/CA: see chapter 2• here: acknowledging unicast packets

– station has to wait for DIFS before sending data– receivers acknowledge at once (after waiting for SIFS) if the packet

was received correctly (CRC)– automatic retransmission of data packets in case of transmission errors

t

SIFS

DIFS

data

ACK

waiting time

otherstations

receiver

sender data

DIFS

contention


802.11 802.11 –– DFWMACDFWMAC w/ RTS/CTSw/ RTS/CTS• Sending unicast packets

– station can send RTS with reservation parameter after waiting for DIFS (reservation determines amount of time the data packet needs medium)

– acknowledgement via CTS after SIFS by receiver (if ready to receive)– sender can now send data at once, acknowledgement via ACK– other stations store medium reservations distributed via RTS and CTS

t

SIFS

DIFS

data

ACK

defer access

otherstations

receiver

sender data

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)


802.11 CTS/RTS:802.11 CTS/RTS: FragmentationFragmentationPurpose: reduce error probability per packet (=fragment)

t

SIFS

DIFS

data

ACK1

otherstations

receiver

sender frag1

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

NAV (frag1)NAV (ACK1)

SIFSACK2

frag2

SIFS

NAV: Net allocation vector (min. forbidden time for other stations)


802.11: DFWMAC w/ PCF802.11: DFWMAC w/ PCF

PIFS

stations‘NAV

wirelessstations

pointcoordinator

D1

U1

SIFS

NAV

SIFS D2

U2

SIFS

SIFS

SuperFramet0

med. busy

t1

point coordinator determines access (down/up link); polling & contention phases may alter

tstations‘NAV

wirelessstations

pointcoordinator

D3

NAV

PIFS D4

U4

SIFS

SIFS CFend

contentionperiod

contention free period

t2 t3 t4


802.11 802.11 -- Frame formatFrame format• Types

– control frames, management frames, data frames• Sequence numbers

– important against duplicated frames due to lost ACKs • Addresses

– receiver, transmitter (physical), BSS identifier, sender (logical)• Miscellaneous

– sending time, checksum, frame control, data

FrameControl

DurationID

Address1

Address2

Address3

SequenceControl

Address4 Data CRC

2 2 6 6 6 62 40-2312bytes

version, type, fragmentation, security, ...


MAC address formatMAC address formatscenario to DS from

DSaddress 1 address 2 address 3 address 4

ad-hoc network 0 0 DA SA BSSID -infrastructurenetwork, from AP

0 1 DA BSSID SA -

infrastructurenetwork, to AP

1 0 BSSID SA DA -

infrastructurenetwork, within DS

1 1 RA TA DA SA

DS: Distribution SystemAP: Access PointDA: Destination AddressSA: Source AddressBSSID: Basic Service Set IdentifierRA: Receiver AddressTA: Transmitter Address


802.11 802.11 -- MAC managementMAC management• Synchronization

– try to find a LAN, try to stay within a LAN– timer etc.

• Power management– sleep-mode without missing a message– periodic sleep, frame buffering, traffic measurements

• Association/Reassociation– integration into a LAN– roaming, i.e. change networks by changing access points – scanning, i.e. active search for a network

• MIB - Management Information Base– managing, read, write


802.11802.11 Synchronization via BeaconSynchronization via Beaconbeacon interval

tmedium

accesspoint

busy

B

busy busy busy

B B B

infrastructure net:

AdHoc net:

tmedium

station1

busy

B1

beacon interval

busy busy busy

B1

value of the timestamp B beacon frame

station2B2 B2

random delay


802.11 802.11 Power managementPower management• Idea: switch the transceiver off if not needed• States of a station: sleep and awake• Timing Synchronization Function (TSF)

– stations wake up at the same time• Infrastructure

– Traffic Indication Map (TIM)• list of unicast receivers transmitted by AP

– Delivery Traffic Indication Map (DTIM)• list of broadcast/multicast receivers transmitted by AP

• Ad-hoc– Ad-hoc Traffic Indication Map (ATIM)

• announcement of receivers by stations buffering frames• more complicated - no central AP• collision of ATIMs possible (scalability?)


802.11 802.11 -- RoamingRoaming• No or bad connection? Then perform:• Scanning

– scan the environment, i.e., listen into the medium for beacon signals 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


Original Original HIPERLAN protocol familyHIPERLAN protocol family

HIPERLAN 1 HIPERLAN 2 HIPERLAN 3 HIPERLAN 4Application wireless LAN access to ATM

fixed networkswireless local

looppoint-to-pointwireless ATMconnections

Frequency 5.1-5.3GHz 17.2-17.3GHzTopology decentralized ad-

hoc/infrastructurecellular,

centralizedpoint-to-

multipointpoint-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

name under ETSI BRAN (wATM): HIPERACCESS | HIPERLINK


HIPERLAN 1 HIPERLAN 1 -- CharacteristicsCharacteristicsHiperLan: ETSI standards family (start ‘96)Characteristics of Hiperlan 1:

– point-to-point & point-to-multipoint comm., connectionless– 23.5 Mbit/s, 1 W power, 2383 byte max. packet size– asynchronous and time-bounded services, QoS, hierarchical priorities– infrastructure or ad-hoc networks– beyond 802.11: mobile „forwarding“ nodes ! towards true AdHoc nets– power saving, encryption, checksums

PMD

PLCP

MAC

LLC

PHY

DLC

PHY: physical layer

CAC: channel access ctrl

MAC: medium access ctrl

HIPERLAN layers

PHY

DLC

LLC

802.11 layers

?


HIPERLAN 1 HIPERLAN 1 -- Physical layerPhysical layerScope/Characteristics:

– modulation, demodulation, bit and frame synchronization– forward error correction mechanisms– measurements of signal strength, channel sensing– 3 mandatory channels: 5.1764680/ 5.1999974/ 5.2235268 GHz– 2 optional ch. (not in all countries): 5.2470562/ 5.2705856 GHz

Maintaining high data-rate (23.5 Mbs) power-consuming – bad for MS– packet header: low bit-rate LBR, 1.4 Mbps, comprises receiver info– only receiver(s) addressed by a packet continue receiving:

• 450 bit synchronization• minimum 1, maximum 47 frames with 496 bit each

– higher velocities of MS (> 1.4 m/s): max. no. of frames reduced– GMSK for high bit-rate, FSK for LBR header

LBR synchronization data0 data1 datam-1. . .

HBR


HIPERLAN 1 HIPERLAN 1 –– CACCAC, MAC, MAC layerlayerss• CAC layer: • 5 Priority levels for QoS support (access w/ EY-NPMA see below)

– QoS mapped onto Prio level via packet lifetime (set by application) • if lifetime = 0: useless to forward packet to receiver• standard start value 500ms, maximum 16000ms• packet waiting @MS (low prio): waiting time permanently subtracted• prio = f (lifetime, waiting time in a sender, no. of remaining hops)• ! priority of waiting packets rises automatically

• MAC Layer: compatible to ISO (IEEE) MAC• Supports time-bounded services via a priority scheme• Packet forwardg: P2P & broadcast (if no path info available), QoS

support• Encryption mechanisms (but no key mgmt.)• Power conservation mechanisms

– MS can agree upon awake patterns (e.g., periodic wake-ups to rcv data)– in addition, some nodes in the net must buffer data for sleeping

terminals and to forward them at the right time (so-called stores)


prioritization

HIPERLAN 1 HIPERLAN 1 -- EYEY--NPMA INPMA IElimination Yield Non-preemptive Priority Multiple Access• Phases: prio resolution, contention resolution, transmission• Basis: slots, bursts: k*“11111010100010011100000110010110“ in HBR

(slot sizes 168/212/256 HBR bit times)• Phase 1: each MS has prio p ∈ {0,...,4} and performs as follows:

• wait&sense for p slots: prio. detection (abort if slots not idle)• send burst in slot p+1 iff no burst sensed before: prio. assertion

only highest existing prio „survives“ (sending == survival)

contention transmissiontransmission

sync

hron

izat

ion

prio

rity

dete

ctio

n

prio

rity

asse

rtion

tus

er d

ata

elim

inat

ion

burs

t

elim

inat

ion

surv

ival

verif

ivca

tion

yiel

d lis

teni

ng

IYSIPS IPA IES IESV


• Phase 2a: elimination (who sends longest burst? maybe several!)– random drawing of burst length n per station: n ∈ {0,...,12} slots

• probabilities: p(n) = 2-(n+1) for 0 ≤ n < 12, p=2-12 for n=12• sending (skipped if n=0) phase called elimination burst

– then sense for 1 slot: if idle ! „my burst was (one of) the longest“! station survives, else withdraws; called elim. survival verification

• Phase 2b: yield listening: similar to CSMA/CA– wait&sense for n slots, n ∈ {0,...,9}, equal distribution p(n)=0.1– transmit iff (n=0 or sense=idle), else withdraw

• Phase 3: transmission– small chance of collision remains!!– if channel was idle for ≥ 1700 bit times: send without EY-NPMA– synchronization using the last data transmission

note: prio. detection, elim. burst, yield listening have variable-but-max. length

HIPERLAN 1 HIPERLAN 1 -- EYEY--NPMA IINPMA II


ATM ATM -- basic principlebasic principle• ATM once advocated by telcom industry as all-integrating B-ISDN• statistical (asynchronous, on demand) TDM (ATDM, STDM)• miniature fixed-size cell ! idea: circuit- & packet switching merge• header: user conn.ID (virtual path/circuit id.: VPI, VCI); checksum...• mixing of cell-rates, connection types, guarantees, bursts, ...

– e.g., guaranteed minimum bit-rate– additionally bursty traffic if net permits

• asyn. ATM stream + „oper./maintenance cells“ ! cont. cell-streamarchitecture:• out-of-band signalling (cf. SS#7): user/control/mgmt. plane• layers:

– physical layer: coding/xmission, header error correction, ...– ATM layer: VPI & VCI translation, multiplexing, ...– ATM adaption layer AAL (+sublayers):

5B 48Bheader user data


ATM ATM services services and and wATMwATM• ATM Forum has specified, e.g., QoS support:

– services: VBR, CBR, ABR, UBR – var, const, available, unspecified bitrate– detailed parameters like max. cell delay CTD, delay variation CDV,

cell loss ratio CLR, peak/min./sustainable cell rate PCR, MCR, PCR, ...• 1996: wireless ATM working group within ATM Forum

– Radio Access Layer (RAL) Protocols:• radio access/resource, DLC & MAC, low-layer handover...

– Mobile ATM Protocol Extensions: 6 new protocols• Mobile Connection Management Protocol• Mobile Handover Management Protocol• Mobile Location Management Protocol• Mobile Routing Protocol• Mobile Media Access Control Protocol• Mobile Data-Link Control Protocol


wATM wATM Reference modelReference model

WMT

WMT

RT

RT

RT

AP

AP

EMAS-E

EMAS-N

EMAS-N

APCPUNI+M

NNI+M

WMT (Wireless Mobile ATM Terminal)RT (Radio Transceiver)AP (Access Point)EMAS-E (End-user mob.-supporting

ATM Switch - Edge)EMAS-N (.... - Network)APCP (Access Point Control Protocol)UNI+M (User-to-Net Interface w/ mob. support)NNI+M (Net-to-Net Interface w/ mob. support)

RAL

ATM

RAL PHY

ATM

PHY PHY

ATM

PHY PHY

ATM

PHY PHY

ATM

PHY

AAL

user process

PHY

ATMATM

AAL

user process

PHY

radio segment fixed network segment

MATMterminal

WATMadapter

WATMaccess point EMAS-E EMAS-N ATM switch ATM

terminal


RAL RAL functionsfunctions//requirementsrequirements• Phy Layer: definition of cell characteristics

– frequencies, efficient re-use of frequencies, antennas, power, range – Carrier freq., symbol rate, modulation, coding, training sequences...– Data and control interfaces to the radio unit – requirement: Bit Error Rate (BER) <= 10-4, availability 99.5 %– requirement: 25 Mbps, indoor 30-50/outdoor 200-300m (100 mW)

• MAC Layer: simultaneous access of several MS to medium– ATM service classes (CBR, VBR, ABR, UBR) including QoS ctrl.– Support of user mobility– MAC efficiency: 60-75 % (over 90% is possible)– data rates: peak 25 Mbps, sustained 6M, yet efficient for low rates

• LLC Layer– wireless header, control messages– Special functions for ATM service classes

• error control (ARQ mandatory)• forward error correction (optional)• meta-signaling to support handover (optional) 8.20.1


ETSI Broadband Radio Access NetETSI Broadband Radio Access Net• BRAN: Hiperlan-2, -3 (as „Hiperaccess“), -4 (as „Hiperlink“)• ATM+Internet: net convergence layer = superset of requirements• ATM-QoS (VBR, CBR, ABR, UBR)• Hiperlan-2: wireless access ≥ 25 Mbps; candidate for wATM-RAL• connection to private and public networks• scope of specifications:

– PHY, DLC; interworking, especially to fixed ATM net & TCP/IP – coordination with ATM Forum, IEEE 802.11, IETF, ITU-R, ...

userwirelessterminaladapter

APtransceiver

APcontroller

mobilityenhanced

switch externalnetwork

mobile nodewireless sub-system

wireless access point

H2.0 H2.1.1 H2.1.1.1 H2.2 H2.3

H2.1.2


Other Other „„next stepsnext steps““Several US mobile broadband activities around wATMMBS was EU Race-Project, followed by SAMBA (EU ACTS). Goals:

– transmission of ATM cells over radio at 34 Mbit/s user bit rate. – portable millimetre-wave transceiver at 40 GHz including antennas. – design of state-of-the-art baseband processing ASICs. – dynamic channel allocation in ATM mobile broadband systems. – radio handover and mobility management functions. – suitable medium access techniques.


9.9.Broadcast NetworksBroadcast NetworksAsymmetric communication environments

– bandwidth limitations of transmission medium differ up-/downstream– depends on applications, type of information– examples

• wireless networks with base station and mobile terminals• client-server environments (diskless terminal)• cable TV with set-top box• information services (pager, SMS)

Special case: unidirectional distribution systems• high bandwidth server ! client, no bandwidth upstream• problems:

– a sender can optimize transmitted information only for one group of users/terminals (see below)

– special functions needed to personalize requirements/applications– usually complemented w/ lower-bandwidth upstream net (e.g., phone)


BroadcastBroadcast: : UnidirUnidir.. DDistributionistributionservice provider service user

sender

receiver

receiver

receiver

.

.

.

unidirectionaldistribution

medium

A

A

A

A

A

A

A B

B

B

B

optimized for expected access pattern

of all users

individual accesspattern of one user≠≠≠≠


BBroadcastroadcast DiDiskssks: : Xmit StructuringXmit Structuring• Sender

– cyclic repetition of data blocks– different patterns possible (optimization only for known content)

• Receiver– use of caching

• cost-based strategy: what are the costs for a user (waiting time) if a data block has been requested but is currently not cached

• application and cache have to know content of data blocks and access patterns of user to optimize

A B C A B Cflat disk

A A B C A Askewed disk

A B A C A Bmulti-disk


DAB: Digital Audio BroadcastingDAB: Digital Audio BroadcastingMedia access:• COFDM (Coded Orthogonal Frequency Division Multiplex)• SFN (Single Frequency Network)• 192 to 1536 subcarriers within a 1.5 MHz frequency band

Frequencies (2 phases):• Ph.1: 1 in 32 freq.blocks, terrestrial TV chan. 5..12 (174..230MHz, 5A - 12D)• Ph.2: 1 in 9 freq.blocks in L-band (1452..1467.5 MHz, LA - LI)

Further Characteristics:• Sending power: 6.1 kW (VHF, Ø 120 km) or 4 kW (L-band, Ø 30 km) • Data rates: 2.304 Mbit/s (net 1.2 to 1.536 Mbit/s)• Modulation: Differential 4-phase modulation (D-QPSK)• Audio channels per frequency block: typ. 6, max. 192 kbit/s• Digital services: 0.6 - 16 kbit/s (PAD), 24 kbit/s (NPAD)• Stream mode: transparent, w/ fixed bit rate• Packet mode: addressable packets


DAB DAB SSenderender

Trans-mitter

Trans-missionMulti-plexer

MSCMulti-plexer

ODFM

PacketMux

ChannelCoder

AudioEncoder

ChannelCoder

DAB Signal

Service Information FICMultiplex Information

DataServices

AudioServices Radio Frequency

MSC (Main Service Channel)– carries all user data (audio, multimedia, ...)– consists of CIFs (Common Interleaved Frames)– each CIF 55296 bit, every 24 ms (depends on mode)– CIF contains CU (Capacity Units), 64 bit each

FIC (Fast Information Channel)– carries control information– consists of FIBs (Fast Information Block)– each FIB 256 bit (incl. 16 bit checksum)– defines configuration and content of MSC


DAB DAB Transmission Transmission FFramerame

synchronizationchannelSC

main servicechannel

FIC

MSC

nullsymbol

phase referencesymbol

datasymbol

datasymbol

datasymbol

. . . . . .

symbol Tu

frame duration TF

guard interval Td

L 0 0 12 L-11 L

fast informationchannelFIC


DAB DAB Audio Audio CCodingoding• What?

– audio transmission almost with CD quality– robust against multipath propagation, minimal distortion of fading signal

• How?– 16 bit, 48 kHz, stereo PCM ! MPEG (MUSICAM), compression 1:10– redundancy bits for error detection and correction– burst errors typical for radio transmissions ! signal interleaving – low symbol-rate, many symbols

• Xmit via long symbol sequences, separated by guard spaces • delayed symbols, e.g., reflection, still remain within the guard space

• Bit rate management via multiplexer:– „DAB ensemble“ = audio program & data services & different

requirements for transmission quality and bit rates– standard foresees dynamic reconfig. of DAB multiplexing scheme– data rate may be varied, free capacities used for other services– multiplexer autonomy ! diff. providers may add services


DAB: DAB: Reconfiguration Reconfiguration ExampleExample

D1 D2 D3 D4 D5 D6 D7 D8 D9

Audio 1192 kbit/s

PAD

Audio 2192 kbit/s

PAD

Audio 3192 kbit/s

PAD

Audio 4160 kbit/s

PAD

Audio 5160 kbit/s

PAD

Audio 6128 kbit/s

PAD

DAB - Multiplex

D1 D2 D3 D4 D5 D6 D7 D8 D9

Audio 1192 kbit/s

PAD

Audio 2192 kbit/s

PAD

Audio 3128 kbit/s

PAD

Audio 4160 kbit/s

PAD

Audio 5160 kbit/s

PAD

Audio 796 kbit/s

PAD

DAB - Multiplex - reconfigured

Audio 896 kbit/s

PADD10 D11


DAB: DAB: MOTMOTMOT: Multimedia Object Transfer Protocol

• Problem:– broad range of receiver capabilities

audio-only devices with single/multiple line text display, additional color graphic display, PC adapters etc.

– all receivers should at least be able to recognize all kinds of program associated and program independent data and process some of it

• Solution:– common standard for data transmission: MOT– important for MOT is the support of data formats used in other

multimedia systems (e.g., online services, Internet, CD-ROM)– DAB can therefore transmit HTML documents from the WWW with

very little additional effort


MOT structureMOT structure• MOT formats

– MHEG, Java, JPEG, ASCII, MPEG, HTML, HTTP, BMP, GIF, ...• Header core

– size of header and body, content type• Header extension

– handling information, e.g., repetition distance, segmentation, priority– information supports caching mechanisms

• Body– arbitrary data

• DAB allows for many repetition schemes– objects, segments, headers

header core

header extension body

7 byte


Digital Video BroadcastingDigital Video Broadcasting• 1991 foundation of the ELG (European Launching Group)

goal: development of digital television in Europe• 1993 renaming into DVB (Digital Video Broadcasting)

goal: introduction of digital television based on– satellite transmission– cable network technology– later also terrestrial transmission

SDTVEDTVHDTV

Multimedia PC

B-ISDN, ADSL,etc. DVD, etc. DVTR, etc.

TerrestrialReceiver

Cable

Multipoint Distribution

System

Satellites DVBDigital VideoBroadcastingIntegrated

Receiver-Decoder


DVB ContainerDVB Container• DVB transmits MPEG-2 container

– high flexibility for the transmission of digital data– no restrictions regarding the type of information– support for Set Top Boxes STB– DVB Service Information specifies the content of a container

• NIT (net info table): lists services of a provider (+. info f. STBs)• SDT (Service Description Table): list of names and parameters for

each service within a MPEG multiplex channel• EIT (event info table): status of current Xmission (+ info for STBs)• TDT (Time & Date Table): Update info. for STBs

multimediadata broadcasting

MPEG-2/DVBcontainer

single channelhigh definition television

MPEG-2/DVBcontainer

HDTV

multiple channelsstandard definition

MPEG-2/DVBcontainer

SDTV

multiple channelsenhanced definition

MPEG-2/DVBcontainer

EDTV


Example: Example: HHighigh SSpeed Internetpeed Internet• Asymmetric data exchange

– downlink: DVB receiver, data rate per user 6-38 Mbit/s– return channel from user to service provider: e.g., modem with 33

kbit/s, ISDN with 64 kbit/s, ADSL with several 100 kbit/s etc.

DVB adapter

PCInternet

TCP/IP

leased line

serviceprovider

informationprovider

satellite provider

satellite receiverDVB/MPEG2 multiplexsimultaneous to digital TV


10. Ad Hoc 10. Ad Hoc NetworksNetworks• many terms, such as PRN: packet radio network• example US Metricom (Bay Area):

– „poletop“ hubs, routing between poletops, 1-5 mile cells– wired-net access every 2-3 hubs (latency!)– 100kbps raw, 20-30 kbps effective throughput

• support in 802.11 & Hiperlan partly discussed („infrastructure net“)• history: military use• further push may come from vehicle-vehicle, robot-robot nets

– decentralized traffic / route control– robots: cf. airport cleaning etc.

• most AdHoc networking tbd in later chapters (higher layers)– such as: large-scale mobile routing, service discovery, ...

• summary:– AdHoc networking still in its infancy!– imagine taxi drivers starting public network infrastructure !?


HiperLanHiperLan 1: 1: Information Information BBasesases• Route Information Base (RIB) - how to reach a destination

– [destination, next hop, distance]• Neighbor Information Base (NIB) - status of direct neighbors

– [neighbor, status]• Hello Information Base (HIB) - status of destination (via next hop)

– [destination, status, next hop]• Alias Information Base (AIB) - address of nodes outside the net

– [original MSAP address, alias MSAP address]• Source Multipoint Relay Info Base (SMRIB) - current MP status

– [local multipoint forwarder, multipoint relay set]• Topology Information Base (TIB) - current HIPERLAN topology

– [destination, forwarder, sequence]• Duplicate Detection Information Base (DDIB) - remove duplicates

– [source, sequence]


AdAd--HHococ NNetsets using HIPERLAN 1using HIPERLAN 1

neighborhood(i.e., within radio range)

Information Bases (IB):RIB: RouteNIB: Neighbor HIB: Hello AIB: AliasSMRIB: Source Multipoint RelayTIB: TopologyDDIB: Duplicate Detection

RIBNIBHIBAIBSMRIBTIBDDIB



RIBNIBHIBAIBDDIB

RIBNIBHIBAIBDDIB

RIBNIBHIBAIBDDIB

12

345

6

Forwarder

Forwarder

Forwarder

Documents

Telecooperation III –Chapter 3: Mobile Networksafn48922/downs/wireless/TK3-K3-MobNetSys.pdfJoe: 555-1287 Gotta remember to ... – Internal timer runs, connection maintained •