Cours 8: Systèmes sans fil

Cours 8: Systèmes sans fil Communications sans fil, M2 ISIM 2012-2012

Iryna Andriyanova

Tuesday, November 13, 12

Design des réseaux sans fil


1. Re-utilisation du spectreDesign des systèmes cellulaires

La bande passantee est limitée, alors la réutilisation du spectreSpectral ReuseDue to its scarcity, spectrum is reused

BS

In licensed bands

Cellular, Wimax Wifi, BT , UWB,…

and unlicensed bands

Reuse introducesinterference

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1. Re-utilisation du spectreInterférence dans les systèmes cellulaires

Le réutilisation du spectre cause l’interférence.L’interférence :

augmente la probabilité d’erreur et réduit la capacité si traitéecomme bruitpeut être parfaitement supprimée, si elle est décodablepeut être utilisée pour la coopération et la cognition (futuresgénérations ?)

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1. Re-utilisation du spectreSystèmes cellulaires

• Frequencies (or time slots or codes) are reused at spatially-

separated locations ! exploits power falloff with distance.

• Base stations perform centralized control functions

(call setup, handoff, routing, etc.)

• Best efficiency obtained with minimum reuse distance

• System capacity is interference-limited.

8C32810.43-Cimini-7/98

Cellular System Overview

Les fréquences (ou les slots de temps ou les codes) sontréutilisés dans les cellules situées assèz loin l’une de l’autre.Les stations de base effectuent le controle centralisé(etablissement de l’appel, handover, routage,...).La meilleure efficacité est obtenue avec la distance deréutilisation grande.

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Re-utilisation du spectre et capacité totale du système

58

Spectrum Usage and System Capacity:Signal Bandwidth, C/I and Frequency Reuse

GSM

AMPS, D-AMPS, N-AMPS

CDMA

30 30 10 kHz Bandwidth

200 kHz

1250 kHz

1 3 1 Users

8 Users

22 Users1

1

11

11

11

111

111

1 23

4

43

2

56 17

Typical Frequency Reuse N=7



Vulnerability:C/I #�17 dB

Vulnerability:C/I #�6.5-9 dB

Vulnerability:EbNo #�6 dB

Each wireless technology (AMPS, NAMPS, D-AMPS, GSM, CDMA) uses a specific modulation type with its own unique signal characteristics

� Signal Bandwidth determines how many RF signals will “fit” in the operator’s licensed spectrum

� Robustness of RF signal determines tolerable level of interference and necessary physical separation ofcochannel cells

� Number of users per RF signal directly affects capacity

59

Capacity Comparison of Wireless Technologies:800 MHz. Cellular Applications

AMPS

730

416593118118

54

TDMA

730

416593118354

162

CDMA

11250

9930817

136

408

12.5 MHz

17 17 6

11.5 44 123.1

34.5 132 369.3

Band 800 (A,B)

TechnologyFwd or Rev Spectrum

Freq Reuse Factor NReq’d C/I or Eb/No, dB

RF Signal BW, kHzTotal # RF SignalsRF Sigs per Cell @ N# Sectors per Cell# CCH per SectorRF Signals per SectorVoicepaths/RF SignalVoicepaths per Sector

Voicepaths per SiteP.02 Erlangs per Sector

Capacity vs AMPS @800P.02 Erlangs per Site

1 3.8 10.7


2. Considérations du design des couches basses et de la planification des fréquencesConsidérations de design

Partage du spectre

TD, CD ou hybrides (TD/FD)Distance de réutilisation

Distance ente les cellules avec la même fréquence, le mêmeslot ou le même codeLa petite distance augmente le nombre des utilisateurs maiségalement augmente l’interférenceRayon de la cellule

La diminution de la taille de cellule augmente la capacité maiscomplique le routage et le handoverAllocation des ressources

Puissance, bande passante, ...Techniques de coopération

Le relayage entre les terminaux et la station de base;Coopération entre les stations de base


3. Gestion de la communication

• Canaux de communication sont utilisés pas les utilisateurs individuels pendant leur communication active avec la station de base (BTS)

• Canaux d’accès sont utilisés par les utilisateurs pas encore actifs pour s’enregistrer, faire la demande de communication ou toute autre signalisation


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Exemple : architecture du réseau CDMA

69

Basic CDMA Network Architecture

Ch. Card ACC

6D6E6F

TFU1

GPSRBSM

CDSU

CDSU

SBSVocodersSelectors

CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

GPS

IOC

PSTN

CDSU DISCOCDSU

DISCO 1

DISCO 2

DS0 in T1Packets

Chips

Access Manageror BSC/BSM

Switch BTSGPS

GPSR

TFU

LPP

Vocoder RFChannelElement


Téléphonie mobile


1-2G design : accent sur la voix1-2G design: accent sur la voix

La couverture des cellules est construite pour la voixService minimal mais "égal" et "partout"Les systèmes cellulaires sont basés sur la voixStructure des données (paquets de 20ms)Codage de canal, les délais du décodage et d’entrelacementEfficacité spectrale0.04-0.07 bits/Hz/secteurComparable pour les TDMA et CDMA

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GSM (TD/FD+FH)GSM (TD et FH)

FDD sépare les uplink et downlinkL’accès est une combination de FD, TD et des sauts lents defréquence (FH)

La bande passante est divisée sur les canaux de 200 kHz.Les canaux sont réutilisés dans les cellules en basant sur lesmesures de l’interférence.Tous les signaux sont modulés avec un code FH

Les codes FH d’une cellule sont orthogonauxLes codes FH des différentes cellules sont semi-orthoogonaux

Le FH diminue l’interférence par le codage.Le FH moyenne l’interférence par les sauts pseudo-aléatoires

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Tableau GSM de “Wireless Communications” de Molisch’11Tableau GSM de "Wireless Communications" de Molisch’11608 Wireless Communications

Table 24.1 Key parameters of the Global System for Mobile communications

Parameter Value

Frequency rangeGSM900 880–915 MHz (uplink)

925–960 MHz (downlink)GSM1800 1710–1785 MHz (uplink)

1805–1880 MHz (downlink)GSM1900 1850–1910 MHz (uplink – U.S.A.)

1930–1990 MHz(downlink – U.S.A.)

Multiple access FDMA/TDMA/FDDSelection of physical channel Fixed channel allocation/intracell

handover/frequency hoppingCarrier distance 0.2 MHzModulation format GMSK (BGT = 0.3)

Effective frequency usage per duplex speechconnection

50-kHz/channel

Gross bit rate on the air interface 271 kbit/sSymbol duration 3.7 µsChannels per carrier 8 full slots (13 kbit/s user data)Frame duration 4.6 msMaximal RF transmission power at the MS 2 WVoice encoding 13 kbit/s RPE-LTPDiversity Channel coding with interleaving

Channel equalizationAntenna diversity (optional)Frequency hopping (optional)

Maximal cell range 35 kmPower control 30-dB dynamics

In general, the circuit-switched data transmission modes of GSM have severe disadvantages. Amain issue is the low data rate of less than 10 kbit/s.13 Furthermore, the long time needed to set upa connection, as well as the relatively high costs of holding a connection, make it very unattractive,e.g., for Internet browsing. There was simply a significant mismatch between the low-data-rateconnection-based services offered by GSM, and the new Web applications, which require highdata volumes in bursts interrupted by long idle periods. Only SMS text messaging proved to besuccessful. For these reasons, packet-switched (also known as connectionless) transmission (seeSection 17.4) was introduced later on.

24.9 Establishing a Connection and HandoverIn this section, we discuss initial establishing of a connection, and the handover procedure, usingthe logical channels described in Section 24.4. Furthermore, we explore the kind of messages that

13 The High Speed Circuit Switched Data (HSCSD) mode provides higher data rates based on circuit-switchedtransmission.

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Tableau GSM : cont’dTableau GSM : cont’d

608 Wireless Communications

Table 24.1 Key parameters of the Global System for Mobile communications

Parameter Value

Frequency rangeGSM900 880–915 MHz (uplink)

925–960 MHz (downlink)GSM1800 1710–1785 MHz (uplink)

1805–1880 MHz (downlink)GSM1900 1850–1910 MHz (uplink – U.S.A.)

1930–1990 MHz(downlink – U.S.A.)

Multiple access FDMA/TDMA/FDDSelection of physical channel Fixed channel allocation/intracell

handover/frequency hoppingCarrier distance 0.2 MHzModulation format GMSK (BGT = 0.3)

Effective frequency usage per duplex speechconnection

50-kHz/channel

Gross bit rate on the air interface 271 kbit/sSymbol duration 3.7 µsChannels per carrier 8 full slots (13 kbit/s user data)Frame duration 4.6 msMaximal RF transmission power at the MS 2 WVoice encoding 13 kbit/s RPE-LTPDiversity Channel coding with interleaving

Channel equalizationAntenna diversity (optional)Frequency hopping (optional)

Maximal cell range 35 kmPower control 30-dB dynamics

In general, the circuit-switched data transmission modes of GSM have severe disadvantages. Amain issue is the low data rate of less than 10 kbit/s.13 Furthermore, the long time needed to set upa connection, as well as the relatively high costs of holding a connection, make it very unattractive,e.g., for Internet browsing. There was simply a significant mismatch between the low-data-rateconnection-based services offered by GSM, and the new Web applications, which require highdata volumes in bursts interrupted by long idle periods. Only SMS text messaging proved to besuccessful. For these reasons, packet-switched (also known as connectionless) transmission (seeSection 17.4) was introduced later on.

24.9 Establishing a Connection and HandoverIn this section, we discuss initial establishing of a connection, and the handover procedure, usingthe logical channels described in Section 24.4. Furthermore, we explore the kind of messages that

13 The High Speed Circuit Switched Data (HSCSD) mode provides higher data rates based on circuit-switchedtransmission.

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GSM : timeslot et structure du réseauGSM : timeslot et structure du réseau

GSM – Global System for Mobile Communications 595

Timeslot (normal burst)

156.25 bits576.92µs

Tailbits

Data

Controlbit

Midamble

Controlbit

Data Guardperiod

Tailbits

Bits8.253571261573

Figure 24.6 Functions of the bits of a normal transmission burst.

of the detection of burst data. This reduces the complexity and increases the performance ofdecoding (see also Chapter 14). The timeslots end with a guard period of 8.25 bits. Apart from“normal” transmission bursts, there are other kinds of bursts. MSs transmit access bursts to establishinitial contact with the BS. Frequency correction bursts enable frequency correction of the MSs.Synchronization bursts allow MSs to synchronize to the frame timing of BSs. These bursts will beexplained in more detail in Section 24.4.2.

24.4 Logical and Physical ChannelsIn addition to the actual payload data, GSM also needs to transmit a large amount of signalinginformation. These different types of data are transmitted via several logical channels . The namestems from the fact that each of the data types is transmitted on specific timeslots that are parts ofphysical channels . The first part of this section discusses the kind of data that is transmitted vialogical channels. The second part describes the mapping of logical channels to physical channels.

24.4.1 Logical ChannelsTraffic CHannels (TCHs)

Payload data are transmitted via the TCHs. The payload might consist of encoded voice data or“pure” data. There is a certain flexibility regarding the data rate: Full-rate Traffic CHannels (TCH/F)and Half-rate Traffic CHannels (TCH/H). Two half-rate channels are mapped to the same timeslot,but in alternating frames.

Full-Rate Traffic CHannels

• Full-rate voice channels: the output data rate of the voice encoder is 13 kbit/s. Channel codingincreases the effective transmission rate to 22.8 kbit/s.

• Full-rate data channels: the payload data with data rates of 9.6, 4.8, or 2.4 kbit/s are encoded withForward Error Correction (FEC) codes and transmitted with an effective data rate of 22.8 kbit/s.

Half-Rate Traffic CHannels

• Half-rate voice channels: voice encoding with a data rate as low as 6.5 kbit/s is feasible. Channelcoding increases the transmitted data rate to 11.4 kbit/s.

Standard ouvertRéseau: BS, MSC, OSSSignalisation: canaux "logiques"canaux de données, de broadcast, de synchronisation, du contrôle debroadcast, du controôle général, d’accès aléatoire,...

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IS-95 (CDMA)IS-95 (CDMA)

Les utilisateurs possèdent les codes d’étalement de type DS(uniques)

Les codes orthogonaux sur le downlinkLes codes semi-orhtogonaux sur l’uplink

Le code est réutilisé dans chaque cellulePas de plannification des fréquencesHandover progressif entre les cellules

Le controle des puissances est nécessaire à cause de "near-farproblem"

Augmentation de l’interférence crée par les terminaux, setrouvant loin de la station de base


IS-95 (CDMA)IS-95

en addition du CDMA, le FDMA est aussi utilisé (FDD)fréquences: 1850–1910MHz (uplink) et 1930–1990MHz(downlink), avec 1.25 MHz pour un canalSpread factor = 64Théoriquement, 64 appels simultanés par cellule, en pratique –entre 12 et 18Asymmetry dans le codage pour uplink et downlinkSignalisation: canal de contrôle de puissance

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DECT (Digital Enhanced Cordless Telephone)

DECT (Digital Enhanced Cordless Telephone)

1.8-1.9 GHzFDMA-TDMADébit: 32 kbps120 connections simultanées au maximum2 applications: grande marché et entreprises

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3G design : voix et données3G design : voix et données

Objectif: le même interface sans fil pour tout le mondeLa transmission par paquets due à la nature des donnéesAugmentation du débit384Kbps à l’exterieur, 1 Mbps à l’interieurAmélioration du qualité de service (QoS)passage de "faire au mieux" à "garantir"Techniques adaptativesDébit (étalement, modulation/codage), puissance, ressources,traitement en espace, MIMO

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2.5G (EDGE) basé sur le GSM2.5G basé sur le GSM

EDGE (2.5G): transmission des données par paquets, modulation etcodage adaptatifs;8PSK/GMSK à 271 ksps offrent de 9 à 52 Kbps par un slot detemps, avec 8 slots disponibles;Le débit maximum est de 384 Kbps;La voix et les données sont transmis en paquets.

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3G UMTS (WCDMA et cdma2000) 3G basé sur le CDMA (W-CDMA et cdma2000)

cdma2000 est construit pour être compatible avec le IS-95WCDMA utilise la puissance et l’étalement adaptatifs, les servicedifférents peuvent être mixer dans un code pour un utilisateur

10

3G CDMA Approaches W-CDMA and cdma2000

!! cdma2000 uses a multicarrier overlay for IS-95 compatibility

!! WCDMA designed for evolution of GSM systems !! Current 3G services based on WCDMA

!! Voice, streaming, high-speed data

!! Multirate service via variable power and spreading

!! Different services can be mixed on a single code for a user

CC

CD

CA


WCDMAPropriétés de WCDMA

Bande passante 5, 10, 20 MHz

Codes d’étalement Facteur d’étalement = 4...256(codes différents pour "data" et "control")

Division en temps intervales de 10ms avec des slots de 0.67ms

Modulation QPSK pour le downlinkBPSK pour l’uplink

Débit 144 Kbps, 1 Mbps, 2 Mbps

Duplexage FDD


WCDMA cont’dWCDMA cont’d

Structure du réseau hiérarchique

Classes des débits Conversation, streaming, interactif, de fond

Codage codes convolutifs et turbo codes

MIMO 2 antennes (downlink) en option


Evolution des standardsEvolution des standardsCellular Standards Evolution to date

Japan Europe Americas

1st Gen TACS NMT/TACS/Other AMPS

2nd Gen PDC GSM TDMA CDMA

Global strategy based on W-CDMA and EDGE networks,

common IP based network, and dual mode W-CDMA/EDGE phones.

3rd Gen (EDGE in Europe and Asia outside Japan) EDGE WCDMA W-CDMA/EDGE

cdma2000 was the initial

standard, which evolved

To WCDMA

1st Gen

3rd Gen

2nd Gen


4G and beyond4G and Beyond

Evolution vers la transmission des donnéesDébits plus importants (au moins pour le downink)Plus de contenu multimedia– Voix, données, video, accès Internet– Broadcast & cellulaireBandes passantes larges (10 MHz et plus)

Les candidats principaux étaient– WOFDM– WCDMA– CDMA à multi-porteuses

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4G and beyondContinuation de l’evolutionEvolution going forward

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4G and beyond

34

Rel’99Rel’99 Rel’4Rel’4 Rel’5Rel’5 Rel’6Rel’6 Rel’7Rel’7 Rel’8Rel’8

UMTS FDDUMTS FDD

NGN

FDD

repeaters

1.28Mcps

TDD

NGN

FDD

repeaters

1.28Mcps

TDD

HSDPA

IMS

HSDPA

IMS

HSUPA

MBMS

HSUPA

MBMS

HSPA+

i.e. MIMO,

CPC, DL

64-QAM,

UL 16-QAM

HSPA+

i.e. MIMO,

CPC, DL

64-QAM,

UL 16-QAM

LTELTE

3GPP Specifications Releases

3GPP

Release

Mohamed Moussaoui, ENSA, Tanger

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NGN = Next Generation NetworkHSDPA = High Speed Downlink Packet AccessIMS = IP Multimedia Sub-SystemHSUPA = High Speed Uplink Packet AccessMBMS = Multimedia Broadcast/Multimedia Services

43

Interface radio de HSDPA

Concepts de HSDPA

Hybrid ARQ

Adaptive Modulation and Coding

Higher Troughput Rates in Dwnlink

Modulation Types - QPSK

- 16-QAM

Transmission and Retransmission Scheduling

in NodeB


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Evolution de l’interface radio

41

Évolution de l’interface radio

~10 ms 50ms (max) 100 ms 150 ms

Latencyround trip time

approx

WCDMA(UMTS)

HSPAHSDPA / HSUPA

HSPA+ LTE

Max downlink speed(bps)

384 k 14 M 28 M 100M

Max uplink speed(bps)

128 k 5.7 M 11 M 50 M

TTI 10 ms 2 ms 2 ms 1 ms

3GPP releases Rel 99/4 Rel 5 / 6 Rel 7 Rel 8

Approx years of initial roll out

2003 / 4 2005 / 6 HSDPA2007 / 8 HSUPA

2008 / 9 2009 / 10

Access method CDMA CDMA CDMA OFDMA / SC-FDMA


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LTE (Long-Term Evolution)

68

DL/UL modulations: QPSK, 16QAM, and 64QAMConvolutional code and Rel-6 turbo code

Adaptive modulation and coding

QPSK, 16QAM, 64QAM (Uplink and downlink) Modulation types supportedConvolutional coding and turbo codingChannel coding

Parameter Details

Peak downlink speed64QAM (Mbps)

100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO)

Peak uplink speeds (Mbps) 50 (QPSK), 57 (16 QAM), 86 (64 QAM) Data type All packet switched data (voice and data).

No circuit switched. Channel bandwidths (MHz) 1.4, 3, 5, 10, 15, 20

Duplex schemes FDD & TDD Mobility 0 - 15 km/h (optimised),

15 - 120 km/h (high performance) Latency Idle to active less than 100ms

Small packets ~10 ms Spectral efficiency Downlink: 3 - 4 times Rel 6 HSDPA

Uplink: 2 -3 x Rel 6 HSUPA Access schemes OFDMA (Downlink)

SC-FDMA (Uplink)

H-ARQ mobility support, rate control, security, and etc

Interface Radio LTE


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Architecture LTE

65

Architecture LTE

eNB eNB

eNB

S1 S1

S1 S1

X2

X2X2

MMES-GW/P-GW

MMES-GW/P-GW

E-UTRAN (Evolved Universal Terrestrial Radio Access Network)

IMS (IP Multimedia Subsystem)PSTN

HSS

Application Servers

IMS

Internet

SAE (System Architecture Evolution) orEPC (Evolved Packet Core)•- MME (Mobility Management Entity)- Serving Gateway (S-GW)

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Architecture LTE

• eNB– All radio interface-related functions

• MME– Manages mobility, UE identity, and

security parameters.

• S-GW– Node that terminates the interface

towards E-UTRAN.

• P-GW– Node that terminates the interface

towards PDN.

eNB eNB

eNB

S1 S 1

S1 S1

X2

X2X2

MMES-GW/P-GW

MMES-GW/P-GW

eNB: E-UTRAN NodeBMME: Mobility Management EntityS-GW: Serving GatewayP-GW: PDN (Packet Data Network) Gateway


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Transmission des données sans fil/ Internet sans fil


BluetoothBluetooth (PAN)

2.4 GHz de la bande passanteFHSS (Frequency Hopping Spread Spectrum)Distances courtes (pas plus de 10 m)Regimes asynchrone (données) et synchrone (voix)Jusqu’au 700 kbpsPas d’infrastructure (ad hoc)Petite consommation

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1300 entreprises au support de BT : Intel, IBM, Nokia, Toshiba, ...


802.11 et Wi-Fi802.11 et Wi-Fi

802.11b– Premier standard devenu populaire– 2.4 GHz de la bande passante– variation du DSSS (Direct Sequence Spread Spectrum)– Les débits sont 11, 5.5, 2 and 1 Mbps (en pratique, 6-7 Mbps aumaximum)– Carrier Sense Multiple Access/Collision Avoidance– Interfère avec Bluetooth! (CSMA/CA)

802.11a/g– 5 GHz de la bande passante– OFDM– 54 Mbps (en pratique, aux alentours de 50%)– Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)


Exemple : 802.11a (Molisch’11)Exemple: 802.11a [Molisch’11]

734 Wireless Communications

LLC

MSDU

MPDU

PSDU

PPDU

PHY

MAC

Figure 29.1 Relations among the MAC service data unit, MAC protocol data unit, physical layer service dataunit, and physical layer protocol data unit.Reproduced with permission from IEEE 802.11 ! IEEE.

29.2 802.11a/g – Orthogonal Frequency Division Multiplexing-BasedLocal Area Networks

In an attempt to attain higher data rates, the 802.11 Working Group (WG) published their 802.11astandard defining a PHY for high-speed data communications based on OFDM in 1999. The standardis defined for the 5-GHz band, where more bandwidth is available, and less interference is present.However, the achievable range is not as good as in the 2.45-GHz band. Therefore, the same PHY,but working in the 2.45-GHz band, was introduced as 802.11g standard. It is currently the dominantversion of WLAN standards. Its main properties are the following (see also Table 29.2):

• use of the 5.15–5.825 GHz band (in the U.S.A.) for 11a and 2.4-2.27 GHz for the 11g standard;• 20-MHz channel spacing;• data rates include 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, where support of 6, 12, and 24 Mbps is

mandatory;• OFDM with 64 subcarriers, out of which 52 are user modulated with Binary or Quadrature-Phase

Shift Keying (BPSK/QPSK), 16-Quadrature Amplitude Modulation (16-QAM), or 64-QAM;• forward error correction, using convolutional coding with coding rates of 1/2, 2/3, or 3/4 as

Forward Error Correction (FEC) coding.

Table 29.2 Important parameters of the 802.11a PHY layer

Information data rate 6, 9, 12, 18, 24, 36, 48, 54 Mbit/sModulation BPSK, OPSK, 16-QAM, 64-QAMFEC K = 7 convolutional codeCoding rate 1/2, 2/3, 3/4Number of subcarriers 52OFDM symbol duration 4 µsGuard interval 0.8 µsOccupied bandwidth 16.6 MHz

Wireless Local Area Networks 737

Input data

Output data B

Output data A

Tb Tb Tb Tb Tb Tb

Figure 29.4 Convolutional encoder (K = 7).Reproduced with permission from IEEE 802.11 ! IEEE.

The second ensures that adjacent coded bits are mapped alternately onto both less and moresignificant bits of the constellation and, thereby, long runs of low-reliability bits are avoided.

Table 29.4 summarizes the rates that can be achieved with different combinations of alphabetsand coding rates, as well as the OFDM modulation parameters.

Table 29.4 Data rates in 802.11a

Data rate (Mbit/s) Modulation Coding rate Coded bits per Coded bits Data bits persubcarrier per OFDM OFDM symbol

symbol

6 BPSK 1/2 1 48 249 BPSK 3/4 1 48 3612 QPSK 1/2 2 96 4818 QPSK 3/4 2 96 7224 16-QAM 1/2 4 192 9636 16-QAM 3/4 4 192 14448 64-QAM 2/3 6 288 19254 64-QAM 3/4 6 288 216

29.2.3 HeadersFor transmission, a preamble and a PLCP header are prepended to the encoded PSDU data3 thatare received from the MAC layer, creating a PPDU. At the receiver (RX), the PLCP preambleand header are used to aid demodulation and data delivery. A PPDU frame format is shown inFigure 29.5.

The PLCP header is transmitted in the SIGNAL field of the PPDU. It incorporates the RATEfield, a LENGTH field, a TAIL field, and so on:

• RATE (4 bits): indicates transmission data rate.• LENGTH (12 bits): indicates the number of octets in the PSDU.• Parity (1 bit): parity check.• Reserved (1 bit): future use.

3 Plus pilot tones.

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802.11 et Wi-Fi802.11 et Wi-Fi

802.11n– jusqu’au 540 Mbps grâce au MIMO– release en Septembre 2009

Wi-Fi (Wireless Fidelity)Une organisation non-profitable s’assurant l’inter-operationalité desproduits basés sur 802.11


HiperMAN+802.16 = WiMaxHiperMAN+802.16 =WiMax

WiMax: Worldwide Interoperability for Microwave Access10-66 GHz, pour les connexions en ligne de vue, ou 2-11 GHz,en non-ligne de vue; 1-15 km de distanceDébits: dizaines MbpsMIMOOFDMScalable OFDMACSMA pour la couche MAC

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Quelques autres applications sans fil


Réseaux ad-hoc

Wireless Environment and Wireless LANs

Ad Hoc Mode

● Independent Basic Service Set (IBSS) or Peer to Peer● Stations communicate directly with each other● When no direct link is feasible between two station, a

third station may act as a relay (multi-hop communications)

Server

Mobile Stations


- Pas d’infrastructure pre-définie - CSMA - Beaucuop d’attention sur le routage (AODV, ...)


Réseaux ad-hoc : applications


Surveillance medicale

• Wireless Medical Telemetry Service (WMTS) aux US : 608 – 614, 1395 – 1400, et 1427 – 1432 MHz; Terminaux “in/on-body” + station de base “nursery station”

• WBAN (Wireless Body Area Network)

11/13/12 10:56 PMfigure9.jpg 468×300 pixels

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Cours 8: Systèmes sans fil