cours 8: systèmes sans fil
TRANSCRIPT
Cours 8: Systèmes sans fil Communications sans fil, M2 ISIM 2012-2012
Iryna Andriyanova
Tuesday, November 13, 12
Design des réseaux sans fil
Tuesday, November 13, 12
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
Typical Frequency Reuse N=4
Typical Frequency Reuse N=1
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
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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
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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
Tuesday, November 13, 12
Architecture d’un réseau sans fil11/13/12 9:34 PMgsm_e2_jpg.jpg 572×348 pixels
Page 1 of 1https://www.bsi.bund.de/SharedDocs/Bilder/DE/BSI/Publikationen/GSM/gsm_e2_jpg.jpg?__blob=normal&v=2
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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
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Téléphonie mobile
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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
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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
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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
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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
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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
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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
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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
Tuesday, November 13, 12
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, ...
Tuesday, November 13, 12
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)
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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
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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
Tuesday, November 13, 12
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
Tuesday, November 6, 12
- Pas d’infrastructure pre-définie - CSMA - Beaucuop d’attention sur le routage (AODV, ...)
Tuesday, November 13, 12
Réseaux ad-hoc : applications
Tuesday, November 13, 12
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
Page 1 of 1http://www.cse.wustl.edu/~jain/cse574-08/ftp/medical/figure9.jpg
Tuesday, November 13, 12