Wireless Man

The IEEE 802.16x WMAN for Broadband Wireless Access

Dr. R. V. Raja Kumar

Professor, Dept. of E & ECE,Indian Institute of Technology, Kharagpur – [email protected]

A Tutorial presentation at Vijayawada

© Prof. R. V. Raja Kumar Dept. of E & ECE

Broadband Services and ApplicationsIIT

Kharagpur

Mobile2/2.5/3/4G

Portable802.11 hotspots Fixed

(homes/small business802.16

• Last mile local connection to internet. • Traditional voice communication. • Video distribution, IP multicasting. • Video conferencing.• Streaming media services.• Broadband connectivity to fixed, portable and

mobile users.


ApplicationsIIT

Kharagpur

• Traditional voice communication.• Mobile education.• Mobile video conferencing.• Streaming media services.• Telemedicine and education.• Mobile IP services. • Access for enterprise networks

• Internet access to WLAN hotspots• Backhaul networks.


Broadband Access SolutionsIIT

Kharagpur

• xDSL• FTTH• Cable modem• 3G Cellular – WCDMA• HSDPA, EVDO, EVDV• The IEEE 802/16x• WiFi. • 4G Cellular• Others


Wireless Networks in Different Scenarios

Personal Area

Different Technologies:• Personal area networks• Local area networks• Metropolitan area networks• Wide area networks

IIT Kharagpur


Wireless Metropolitan Area Networks (WMANs)

BS

Company

HomeMobile

Office

PDA Up to 35 miles

IIT Kharagpur

SSSS

Prof. R. V. Raja Kumar Dept. of E & ECE

WMAN Standards and Harmonization

WiMAX

EuropeNorth America

IEEE 802.16/20 ETSI HiperMAN

Promotion of compatibility and interoperability of broadband wireless products.

IIT Kharagpur

WiBro

N. Korea

IIT Kharagpur


Technologies for Wireless Broadband

high

medium

fixed

Mobility

3G3G

4G cellular

0.01 0.1 1.0 10 100

IEEE 802.16a

Bit rate (Mbps)

EVDOEVDO

IEEE 802.16e

HSDPA

IEEE 802.20

4G cellular


IEEE and ETSI StandardsIIT

Kharagpur

• MMDS – Point to Multipoint (2.5 – 2.7 GHz)• LMDS –Point to Multipoint (28 & 31 GHz)• Point-to-multipoint with sector antennas• Point-to-point with directional antennas• Throughput to 60 Mbps shared per sector (5.8 GHz)• Multiple manufacturers (non-standard based today)• TDM


Legacy - LMDS and MMDSIIT

Kharagpur


Network ArchitectureIIT

Kharagpur

Radio AccessNetwork

PSTN

All IPCore NW

PSTNGateway

Internet


WiMax ForumIIT

Kharagpur

NEOTEC

•An industry-led, non-profit corporation formed to promote and certify compatibility and interoperability of broadband wireless products. •wide acceptance of the IEEE 802.16 and ETSI HiperMANwireless MAN standards.


IEEE 802.16/20 WMAN StandardsIIT

Kharagpur Standard 802.16 802.16a/d 802.16e 802.20

2005 2005-06

WWAN

NLOS

<3.5 GHzLicensedVehicular Mob.-Global Roaming1.25 or 5 MHz

< 1.25 bps/Hz

< 6 Mbps(5 MHz BW)

WMAN

Average Cell Radius 1-3 miNLOS

2-6 GHz

Regional RoamingScalable1.5-5 MHz< 3 bps/Hz

15 Mbps(5 MHz BW)

2004

WMAN

Average Cell Radius 4-6 miNLOS

2-11 GHz

Fixed

Scalable1.5-20 MHz< 3.75 bps/Hz

< 75 Mbps(20 MHz BW)

2001

WMAN

Average Cell Radius 1-3 miLOS

10-66 GHzLicensed

Fixed

Scalable1.5-20 MHz< 4.8 bps/Hz

< 96Mbps(20 MHz BW)

Status

Target App.

Range

Channel ConditionsSpectrum

Mobility SupportChanneli-zationSpectral EfficiencyBit Rate


Comparison of Wireless Broadband SolutionsIIT

Kharagpur


Multiaccess and ModulationIIT

Kharagpur

• OFDM (WirelessMAN-OFDM Air Interface)• 256-point FFT with TDMA (TDD/FDD)• OFDMA (WirelessMAN-OFDMA Air Interface)• 2048-point FFT with OFDMA (TDD/FDD)• Single-Carrier (WirelessMAN-SCa Air

Interface)• TDMA (TDD/FDD)• BPSK, QPSK, 4-QAM, 16-QAM, 64-QAM,

256-QAM• Most vendors will use Frequency-Domain

Equalization• Carrier bandwidth 20 MHz


Other FeaturesIIT

Kharagpur

• High bandwidth

– Up to 134 Mbit/s (28 MHz ch., 10-66 GHz AI

• Point-to-multipoint topology; BS to Multiple SSs.

• Point-to-point mesh topology.

• Simultaneous multiservice support with full QoS

– Efficient transport: IPv4, IPv6, ATM, Ethernet, etc.

• Bandwidth on demand (frame by frame)

• Supports multiple freq. allocations from 2-66 GHz

• Support for mobility.


ChannelizationChannelization in UNI Bandsin UNI BandsIIT

Kharagpur

5250 5270 5290 5310 5330 5350 5725 5745 5765 5785 5805 5825 5845

5480 5500 5520 5540 5560 5580 5600 5620 5640 5660 5680 5700 5720

5720 5740 5760 5780 5800 5820 5840 5860

U-NII middle and upper band

CEPT 5GHz, band B

CEPT 5GHz, band C


Uplink PHY Med. Dep. SublayerIIT

Kharagpur

Rando-mization

FECEncoder

Prea-amble

prepend

SymbolMapper

BBPulse

Shaping

FECDecoder

SymbolDemapper

MatchedFilter

PhysicalInterface

andBurst

Demod.

De-Rando-mization

DataO/P

DataI/P

FromRF

ToRF

Mod.AndPhy.

Interface

Subscriber Station

Base Station


QAMQAMIIT

Kharagpur

-3 -1 31

-3-1

31

11 10 0001

1110

0001

Modulation Scheme Normalization constant for unity

Average power

QPSK C= 1/√2

16-QAM C= 1/√10

64-QAM C= 1/√42

256-QAM C= 1/√170

-7 -5 -3 -1 1 3 5 7

1

3

5

7

-1

-3

-5

-7

111 110 100 101 011 010 000 001

111

110

100

101

011

010

000

001

Constellation of 64 - QAM

Constellation of 16 - QAM


Base band Pulse Shaping for Base band Pulse Shaping for Single Carrier ApplicationSingle Carrier ApplicationIIT

Kharagpur

• Square-root raised Cosine shape with a roll-off factor of 0.25 is supported.

• Roll-off of 0.15 and 0.18 (optional) are also available.

1 1 | |2 2 2

N

N

f rf

πα

⎛ ⎞−⎡ ⎤+ ⎜ ⎟⎢ ⎥⎣ ⎦⎝ ⎠

1

0

( ) ( )1 | | 1N Nf f fα α− ≤ ≤ +

( )| | 1Nf f α≥ +

( )| | 1Nf f α< −

( )H f =

12 2

sN

s

RfT

= =


Permitted EIRPPermitted EIRPIIT

Kharagpur

Terminal Reg. LimitdBW/MHz

Desirable limit

BS -6 + 19dBi < 14 0 dBm

SS -6 + 34dBi < 30 15 dBm

PTP 30 15 dBm

RS facing BS 30

TS facing SS 14

Mesh 30

For the specific subband 25.25–25.75 GHz, as stated in ITU-R Recommendation F.1509 (02/01).Carrier bandwidth = 28 MHz.


Min. Receiver SensitivityMin. Receiver SensitivityIIT

Kharagpur

QPSK 16-QAM 64-QAM

1/2 3/4 1/2 3/4 2/3 3/4

14 -81 -79 -74 -72 -68 -66

1.5 -91 -89 -84 -82 -78 -76

1.75 -90 -87 -83 -81 -77 -75

3 -88 -86 -81 -79 -75 -73

3.5 -87 -85 -80 -78 -74 -72

5 -86 -84 -79 -77 -72 -71

6 -85 -83 -78 -76 -72 -70

7 -84 -82 -77 -75 -71 -69

10 -83 -81 -76 -74 -69 -68

12 -82 -80 -75 -73 -69 -67

-73 -71 -6620 -80 -78 -65

Bandwidth


Min. E/Min. E/ηη Requirement Requirement IIT

Kharagpur

Modulation Eb/No(dB) Coding rate Receiver SNR (dB)

1/2 9.4QPSK 10.5

3/4 11.2

1/2 16.416-QAM 14.5

3/4 18.2

2/3 22.764-QAM 19.0

3/4 24.4


Transmit Spectral MaskTransmit Spectral MaskIIT

Kharagpur

A B D MHzf0

-32

-50

-27

0dBr

Channelization(MHz) A B C D

20 9.5 10.5 19.5 29.5

14.7510 4.75 5.25 9.75

Adjacent channel interference is to be limited.


Dependence of Speed on RangeIIT

Kharagpur

QAM-64QPSK

Up to 35 miles

QAM-16


Forward Error Correcting Code (FEC) Types IIT

Kharagpur

• A concatenation of Reed-Solomon (RS) code and a rate-compatible Convolutional inner code in both the UL and DL.

• Support of Block Turbo Code (BTC) and Convolutional Turbo Code (CTC) are optional.

Code type Outer code Inner code Application

1 RS over GF(256) None High coding rate

2 RS over GF(256) (24, 16) Block CC Low-mod. Coding rate

3 (optional) RS over GF(256) (9, 8) Parity ch. C Mod-high Coding Rate

4 (optional) Block Turbo Code ----- To work at low C / I


Mandatory Channel CodingIIT

Kharagpur

Modulation Uncodedblock size (bytes)

Coded block size (RS-bytes)

Coding rate

RS code CC code rate

QPSK 24 48 1/2 (32,24,4) 2/3

QPSK 36 48 3/4 (40,36,2) 5/6

16-QAM 48 96 1/2 (64,48,8) 2/3

16-QAM 72 96 3/4 (80,72,4) 5/6

64-QAM 96 144 2/3 (108,96,6) 3/4

64-QAM 108 144 3/4 (120,108,6) 5/6

When subchannelization is used, CC only is used.


Data Rates at Different Bandwidths

IIT Kharagpur

Modulation/Code Rate

QPSK1/2

QPSK3/4

16 QAM1/2

16 QAM3/4

64 QAM2/3

4.36 5.94

11.88

23.75

33.25

66.49

8.73

17.45

24.94

49.87

2.19

5.82

11.64

16.63

33.25

2.18

4.37

8.73

12.47

24.94

1.04

2.08

4.15

8.31

16.32

64 QAM3/4

1.7 MHZ 6.55

3.5 MHZ 13.09

26.18

37.40

74.81

7.0 MHZ

10.0 MHZ

20.0 MHZ


TDD and FDD

SubscriberStation

Base stationFDD

time slot

TDD

fupUplink band

fdownDownlink band

IIT Kharagpur


TDD Frame StructureIIT

Kharagpur

Frame j-2 Frame j-1 Frame j Frame j+1 Frame j+2

Adaptive

Downlink subframe Uplink subframe

n = (symbol rate X frame duration) / 4

PS 0 PS n-1


FDD OperationIIT

Kharagpur

timetime

frame

Uplink

Downlink

Broadcast

Full duplex cap. SS

Half duplex SS #1

Half duplex SS #2


Down Link Sub-frame (TDD) Structure

Tx/Rx Transition Gap

TDMDIUC c

prea

mbl

e

DL-MAP UL-MAP

prea

mbl

e

TDMDIUC a

TDMDIUC b

BroadcastControlDIUC=0

TDM Portion

• DIUC stands for Downlink Interval Usage Code

• Preamble used for synchronization and equalization

• Downlink and uplink maps stating the physical slots at which burst begins

• TDM portion caries the data • Data organized into bursts with

different burst profiles• Each subscriber station (SS) receives

and decodes the control information

IIT Kharagpur


Down Link Sub-frame Structure (FDD)

TDMDIUC f

prea

mbl

eTDMDIUC e

TDMDIUC d

prea

mbl

e

prea

mbl

e

prea

mbl

e TDMDIUC g. . .

BroadcastControlDIUC=0

TDM Portion

TDMDIUC cpr

eam

ble

TDMDIUC a

TDMDIUC b

TDMA Portion

prea

mbl

e

DL-MAP UL-MAP

Burst Start Points

•An extra preamble allows better support of half-duplex SSs

•Due to half-duplex nature, some SSs loose synchronization

•TDMA preamble allows SSs to regain synchronization

IIT Kharagpur


Up Link

• Uplink access uses TDMA • Burst transmission supports adaptive burst profiling• Modulation and coding schemes adjusted individually

to each SS• FDD case supports both full duplex SSs and half

duplex SSs• Uplink PHY is based on combination of TDMA and

demand assigned multiple access• Uplink channel is divided into number of slots • Number of slots assigned for various uses

Ex: registration, contention or user traffic• UL-MAP grants bandwidth to specific SSs.

IIT Kharagpur


Up Link Sub-frame Structure

Initial maintenance Opportunities

(UIUC=2)

RequestContention

Opps(UIUC=1)

SS 1Scheduled

Data(UIUC = i )

. . .SS N

Scheduled Data

(UIUC = j)

SS transitiongap Tx/Rx transition

Gap (TDD)

Accessburst

Collision Accessburst

Bandwidthrequest

Collision Bandwidthrequest

IIT Kharagpur


DL and UL PreamblesIIT

Kharagpur

CP 128 128

Tg Tb

UL Preamble:• Short preamble• UL AAS preamble

CP

Tg Tb

CP 128 128

Tg Tb

64 64 64 64

DL Preamble:• First preamble• Initial ranging preamble• Long preamble


OFDM TransceiverIIT

Kharagpur

Mappi-ng of Symb-

ols

IFFT TDMcyclicPre-

fixingDAC

Compa-rison FFT DeMUX

cyclicPrefixRemo-

val

ADC

Demap-ping

ofSymb-

ols

DataO/P

DataI/P

Rx.I/P

Tx.O/P

Mix.

FS

Mix.

FS

fc


Features of OFDM IIT

Kharagpur

• No intercarrier guard bands• Orthogonal carriers and controlled overlapping

of bands• Maximum spectral efficiency (Nyquist rate)• Robustness against frequency selective fading• Immunity to inter-symbol-interference• Simplified equalization• Very sensitive to time-freq. synchronization• Easy and efficient implementation using IFFT

OFDM and TDMA combination for multiaccess.


SubcarriersSubcarriers in OFDMin OFDMIIT

Kharagpur


OFDM Symbol ParametersIIT

Kharagpur

Parameters ValueTotal subcarriers 256

Used carriers, N 192

fs / BW Licensed channels: multiple of 1.75 and license exempt: 8/7; Others: 7/6

Tg / Tb 1/4, 1/8, 1/16, 1/32

Guard Band 28 low and 28 high SCs

No. of pilot car. 8

• Long range high Tg 25% guard time• Small range low Tg 3% guard time• 10 MHz < 5.24 μSec. 1/4 Tg.


OFDM Symbol ParametersOFDM Symbol ParametersIIT

KharagpurParameter Value

NFFT 256NUSED 200Fs/BW licensed channel bandwidths which are

multiples of 1.75MHz and license-exempt: 8/7Any other bandwidth: 7/6

Ts/Tb 1/4,1/8, 1/16,1/32Number of lower frequency guard carriers

28

Number of higher frequency guard carriers

27

Frequency offset indices of guard carriers

-128,-127…, -101+101,+102,…127

Frequency offset indices of Basics Fixed Location Pilots

-84,-60,-36,-12: 12,36,60,84

Subchannel number: Allocated frequency offset indices of carriers

1: (-88,…-76),(-50,…-39),(1,…13),(64,…75)2: (-63,…-51),(-25,…-14),(26,…38),(89,…100)3: (-100,…-89),(-38,…-26),(14,…25),(51,…63)4: (-75,…-64),(-13,…-1),(39,…50),(76,…88)


Sub – ChannelizationProvision

IIT Kharagpur

• Provides optional sub-channelization in UL.

• Useful for power limited platform.

• 16 of 12 subcarier sets are used.

• One/two/four/eight/sixteen sets are assigned to an SS for UL.

• All the eight pilot carriers are used.


OFDM ScalabilityOFDM ScalabilityIIT

Kharagpur

Parameters Values

System bandwidth (MHz)

1.5 2.5 5 10 20

Sampling frequency(Fs,MHz)

1.429 2.825 5.714 11.429 22.857

Sample time(1/Fs,nsec)

700 350 175 88 44

FFT size(NFFT)

128 256 512 1024 2048

Sub carrier frequency spacing 11.16071429 kHz

Useful symbol time(Tb=1/Δƒ)

89.6 µs

11.2 µs

100.8 µs

Guard time(Tg=Tb/8)

OFDMA symbol time(Ts=Tb+Tg)


ExtnExtn. for Mobility. for MobilityIIT

Kharagpur

Coherence time, Tc = = 1.03 mSec

Coherence BW, Bc = 1/5σ ~ 10 KHz (for σ = 20 μ Sec.)~ 40 KHz (for σ = 5.23 μ Sec.)

• Sub carrier spacing > 10 KHz• Pilot rep time < 1 mSec.

When the carrier freq. = 6 GHz, the max. Doppler shift for a vehicle running at 125 km/hr (35 m/s) = 700 Hz

16πfm2

9


Performance of Coded OFDMIIT

KharagpurETSI Vehicular-A: rms Ds= 370nS, BPSK, CC, RS+CC, Turbo coded OFDM using 256 SC, rate ½, no CP.


Down Link PerformanceIIT

Kharagpur

Reported on Web (French operator-Altitude Telecom):For symmetrical TCP/IP transmission, LoS paths 10 Mbit/s over 10km, but this fell to 4 Mbit/s over 5km for non-LoS paths


Test ResultsIIT

Kharagpur

Tests of Pipex Wireless:• Speeds > 2Mbps (up/down) at indoors at 1.2km

(non LOS)

• Speeds of 5Mbps were observed in vehicles at different places.

• With external antennas, speeds of around 10 Mbps (up/down) in indoors at 1.2km (non LOS)

• Speeds of 6Mbps down and 4Mbps up at a range of 6km with external antennas.


PacketizationIIT

Kharagpur

• Application packets Service packets MAC packets• MSDU: MAC service data units• MPDU: MAC packet data units• ARQ: Aut. Tx. Req. for MSDUs

Application Packets

MSDU MSDU MSDU

MPDU MPDU


The Protocol StructureIIT

Kharagpur

MAC Convergence Sublayer

(ATM, Ethernet, 802.1Q, IP)

MAC

MAC Privacy Sublayer

Physical Layer

ATMEthernet, 802.1QInternet Protocol

Packing,FragmentationARQ, QOS

Authentication,Key exchangePrivacy (encryption)

OFDM, rangingPower control, DFS, Tx, Rx

Conv. Sublayer specific SAP

MAC SAP

PHY SAP


QOS Service ClassesIIT

Kharagpur

• Constant bit rate grant, • Real time polling, • Non-real-time polling, • Best effort

• MAC provides a connection oriented service to upper layers,

• QOS parameters can vary over a connection, • The convergence sublayer enables Ethernet,

ATM, TDM voice and IP (Internet Protocol) services to be offered over 802.16.


Traffic TypesIIT

Kharagpur Traffic Type Traffic Model Service FlowHttp Self-Similar Best- EffortFtp Self-Similar NRTPSVideo 2IRP(Interrupted Renewal RTPS

Process)VoIP 2IDP(Interrupted UGS

Deterministic Process)

BW Request Mechanisms:UGS: No separate BW request RTPS: Unicast PollingNRTPS: Unicast Polling BE :Contention Resolution

An example:• Service discipline at each flow is FIFO( both at SS and BS)• Weighted Max-Min scheduling algorithm is used at the BS• Scheduling is done on frame-to-frame basis• It is assumed that all traffic is already admitted to network• Packet Size=800bytes • Upstream frame size=1msec• Max. upstream rate =120Mbps• BW assigned for UGS =48Mbps(40% of max.upstream rate)


PerformanceIIT

KharagpurBW assigned for BW requestsRTPS : 640Kbps NRTPS: 160KbpsBE : 320KbpsBW available for RTPS, NRTPS and BE data transmission= (120-0.640-0.160-0.320-48)Mbps= 70.88MbpsFrom Fig1.Max.throughput of RTPS=120*0.325Mbps=39.0MbpsMax.throughput of NRTPS=(120*0.211)Mbps=25.2MbpsMax.throughput of BE=(120*0.05)Mbps=6MbpsTotal BW utilized=( Data) +( requests)=(48.0Mbps+39.0Mbps+25.2Mbps+6Mbps)

+(1.12Mbps)=119.32MbpsFigure1.

• Load is aggregate of all services• UGS=40%,RTPS=30%,NRTPS=20% and BE=10% of aggregated load• The excess BW of high priority services would be shared by unsatisfied

low priority services• Due to this fact, throughput of BE increases upto 90% of load and decreases

as load increases.

Network Load Vs Throughput

0

10

20

30

40

50

60

70

80

90

100

10 20 30 40 50 60 70 80 90 100 110 120 130

Network Load(% of Upstream peak rate)

Thro

ughp

ut(%

)

UGSRTPSNRTPSBE ServiceAggregated


Open IssuesIIT

Kharagpur

• Complete performance understanding.

• Scheduling at SS and Radio resource management.

• Cost effective implementation.

• Interoperation with legacy systems.

• Mobility and handoff• A road towards 4G cellular?.

Thank You


Comparison of Wireless Broadband SolutionsIIT

Kharagpur


The IEEE 802.16x StandardsIIT

Kharagpur


Channel Data RatesIIT

Kharagpur


APPLICATIONSIIT

Kharagpur

Wireless Man

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