초고속 무선 초고속 무선 LAN LAN 기술 동향기술 동향

2001. 9. 11

중앙대학교 전자전기공학부디지털통신 연구실

조 용 수

(02) 820-5299yscho@cau.ac.kr

21 세기 유망핵심부품 기술 세미나

ContentsContents

고속 무선 LAN 의 표준화 동향

IEEE 802.11b 기술

HIPERLAN/2 표준안

OFDM 기본 이론

IEEE 802.11a 모뎀 설계

고속 무선 LAN 의 표준화 동향

Wireless Access Beyond 3Wireless Access Beyond 3rdrd Generation Generationin

door

outd

oor

IMT-2000 Phase 2 IMT- 2000

Wireless LAN(IEEE 802.11)

HS Wireless LAN (IEEE802.11a, HIPERLAN/1)

Ultra High-Speed WirelessLAN (MMAC)

Broadband Wireless Local Loop (LMDS, HIPERACCESS)

Wireless BroadbandInternet (HIPERLINK)

2 Mbps 25 Mbps 155 Mbps

mobile

still

fixed

fixed

still

BroadbandRadio AccessNetwork(HIPERLAN/2, MMAC)

Wireless Data SolutionsWireless Data Solutions

Standardization of Broadband Wireless Standardization of Broadband Wireless Access NetworkAccess Network

광대역 무선 엑세스 네트워크 표준화 추진 관련도

USA

ATM Forum WATM-WG Network inter-connecting protocol concerning WATM Radio access concerning 5GHz-band WATM

WIN Forum

SUPERNet

Short and medium range transmission media for computer internetworking

JAPAN

MMAC-PC

Radio access concerning MMAC

Network inter-connecting protocol

concerning MMAC

Europe

ETSI-BRAN 5 GHz-band radio access in ATM-based HIPERLAN Network inter-connecting protocol concerning WATM

IEEE 802.11

Standardization of 5GHz-band

Ethernet-based wireless LAN

BRAN (1)BRAN (1)

BRAN 의 목표 기존의 음성 , ISDN 서비스외에 미래의 다양한 멀티미디어 서비스 제공 엑세스 채널 : 사용자와 망간의 인터페이스를 통해 25Mbps 155Mbps 제공 사용자 데이터 전송률 : 회선방식과 ATM 을 포함한 패킷 방식으로

16Kbps 16Mbps 제공 고속 무선 LAN 또는 고정 광대역 무선 엑세스 네트워크에서의 무선 접속 계층과 ATM 및 IP 코어 네트워크와의 연동을 위한 표준화

물리계층의 전송방식 : OFDM 방식

Medium Access Control (MAC) 중앙집중방식으로 AP (Access Point) 에서 Scheduler 에 의해 동적 슬롯 할당 ( 고정 프레임 ) Dynamic Reservation TDMA/TDD 기반

HIPERACCESS

SERVER

HIPERLINK

BRAN 시스템의 망 구성

BRAN (2)BRAN (2)

Type 기 술 특 성 표 준 화 현 황 응 용 환 경

HIPERLAN/1

- 전송률 : 19 Mbps

- MAC : 경쟁방식 CSMA/CD 기반- 변조방식 : GMSK

- 거리 : 최대 200 m

- 대역 : 5.2 GHz ( 비허가 대역 )

ETS 300 652

규격ISO 8802 와 연동 가능한 최대 20 Mbps 의 고속 무선 LAN

HIPERLAN/2

- 전송률 : 6-54 Mbps

- MAC : Dynamic Reservation TDMA/TDD

- 변조방식 : OFDM

- 거리 : 최대 200 m

- 대역 : 5.2GHz ( 비허가 대역 )

EP-BRAN 에서 2000 년 4 월

완료

- HIPERLAN/1 보완- IMT-2000, ATM, IP 망 등의 이동단말과 유선 광대역망의 접속을 위한 고속 무선 전송 시스템- WATM-WG 와 함께 무선 ATM 표준화 작업

HIPERACCESS

/

HIPERMAN

- 전송률 : 25 Mbps

- MAC : Dynamic Reservation TDMA/TDD

- 거리 : 최대 5 Km ( 중거리 )

- 대역 : 40.5-43.5 GHz

EP-BRAN 에서 진행 중

(2001. 12)

- 댁내 또는 중 / 소형 사업장의 가입자를 위한 광대역 고정 가입자망 (B-WLL)

- HIPERACCESS for LOS : milimeter wave

- HIPERMAN for NLOS : below 10 GHz

- IEEE 802.16 과 연관

HIPERLINK

- 전송률 : 155 MHz

- MAC : Dynamic Reservation TDMA/TDD

- 거리 : 최대 150 m

- 대역 : 17.1 GHz ( 비허가 대역 )

EP-BRAN

시작되지 않았음

HIPERACCESS 노드와 HIPERLAN 간의 초고속 (155 Mbps) 점대점 연결 링크로 기간망 역할의 고속 무선 시스템

Standardization of IEEE 802.11Standardization of IEEE 802.11Task Group 표 준 화 목 표 현 황

IEEE 802.11 TG a

- 기존 IEEE 802.11 규격 확장- U-NII 의 5GHz 대역에서 6~54Mbps

전송속도 지원- 휴대 및 이동성 지원

- 1999 년 7 월 OFDM 방식의 물리계층 표준안 확정- ETSI BRAN, MMAC 등에서 유사한 물리계층 표준안으로 추진- 일본 NTT, 미국 Lucent, 이스라엘 BreezeCom 등 추진

IEEE 802.11 TG b

- 기존 IEEE 802.11 규격 기반- 2.4GHz 대역에서 10Mbps 급으로 전송속도 고속화

- 1999 년 7 월 표준안 확정- Alantro, Lucent/Harris, Micrilor 사등 추진

IEEE 802.11 TG d

- 새로운 regulatory domains (countries)

에서의 동작을 위해 필요한 물리계층 요구사항 제정

표준 승인 예정

IEEE 802.11 TG e - QoS 요구사항을 고려한 MAC 계층 강화- Security 강화

제안서 검토 중

IEEE 802.11 TG f - Inter AP 간의 Protocol 제안서 검토 중

IEEE 802.11 TG g

- 2.4 GHz 에서 20 Mbps 이상의 속도 지원- Intersil 의 OFDM 방식 TI 의 PBCC 방식

표결

IEEE 802.11 TG h - DFS 및 TPC 제안 제안서 접수 중

MMAC : Multimedia Mobile Access Communication Ultra high speed, high quality Multimedia information “anytime and anywhere” with seamless connections to optical fiber networks Launch target date : 2002

MMAC - PC (MMAC Promotion Council) Technical Committee

시스템 시스템 개요 대역 응용 서비스

High Speed Wireless

Access

옥내외에서 최대 30Mbps 까지전송할 수 있는 이동 통신 시스템

SHF 및기타 3-60 GHz

이동 비디오 전화

Ultra High Speed

Wireless LAN

옥내에서 최대 155Mbps 까지전송할 수 있는 무선 ATM 방식의액세스 시스템 및 이더넷 방식의무선 LAN

밀리미터파 대역 (30 – 300GHz)

고품질 화상 회의

5GHz Band Mobile

Access

옥내외에서 최대 20–25Mbps 까지전송할 수 있는 무선 ATM 방식의 무선 LAN

5GHz 멀티미디어 정보 접속

Wireless Home-link가정 내의 PC 및 음향 / 영상 기기간의상호 접속과 멀티미디어 정보 교환을위한 100Mbps 급 무선 시스템

SHF 및기타 3-60 GHz

댁내 멀티미디어 매체 정보기기 (IEEE1394) 간의

상호 무선 접속

MMAC in JAPANMMAC in JAPAN

Spectrum Allocation in 5GHzSpectrum Allocation in 5GHz

Europe

US

Japan

Korea

5100 5200 5300 5600 57005400 5500 5800 MHz

HIPERLAN (Indoor, 200mW EIRP) HIPERLAN (In-and outdoor, 1W EIRP)5.15-5.35 GHz / 8 channels 5.470-5.725 GHz / 11 channels

High Speed Wireless Access (Indoor, 200mW)5.15-5.25 5.25-5.35 5.470 - 5.725

U-NII (Indoor, 200mW) (In- and outdoor, 1W)5.15-5.25 5.25-5.35

U-NII (In- and outdoor, 4W)5.725-5.825

5.725-5.825

License exempt,455MHz

Sharing rules,100MHz

Unlicensed,300MHz

: Under consideration

20Mhz Channel separation ⇒ few carrier frequencies

Coexistence with other radio systems

⇒ Need for a Dynamic Frequency Selection (DFS) Technique

Other ForumsOther Forums

OFDM Forum

To foster a single, compatible OFDM standard, needed to implement cost-effective, high-speed wireless networks on variety of devices

Launched in Mar. 2000 by Wi-LAN, Phillips, Ericsson, Nokia, Samsung EM and Caltrans. Later Alcatel, Intersil, Solectek, Infineon Tech., Motorola joined.

www.OFDM-Forum.com

HIPERLAN2 Global Forum (H2GF)

To drive the adoption of HIPERLAN/2 as a global broadband wireless technology in 5GHz, with bandwidth anywhere between 6 - 54Mbps using OFDM.

Launched in Sep. 1999 by 6 founding members, Bosch, Dell, Ericsson, Nokia, Telia and TI. Later Nortel and Xilinx joined.

www.HIPERLAN2.com

고속 무선 고속 무선 LAN LAN 관련 국내 동향관련 국내 동향 정보 통신부 「 5 GHz 무선 접속망 Task Group 」

• 연구 1 반 : 5 GHz 대 국내 전파환경 측정 연구

• 연구 2 반 : 국제적 기술동향을 고려한 국내 초고속 무선 접속망 기능 및 규격연구 ,

국내외 기술개발 동향 조사 및 기술개발 분야 발굴

• 연구 3 반 : 주파수 간섭 및 공유방안 연구

국내에 적합한 초고속 무선 접속망용 주파수 이용대역 연구

초고속 무선 LAN 포럼

• 정보통신부 주관 , ETRI 와 한국통신사업자연합회 주최로 2001. 5. 30 창립

• 제 1 분과 : 표준 규격개발 분과 위원회

• 제 2 분과 : 서비스 품질 분과 위원회

• 제 3 분과 : 운용제도 개선 분과 위원회

IEEE 802.11b 기술

IEEE 802.11 Chipset (1) Intersil PRISM Chipset

PRISM I 2 Mbps, 2.4 GHz, IEEE 802.11

PRISM II (5 chip solution) 11 Mbps, 2.4 GHz, IEEE 802.11b

– HFA3983 – 2.4 GHz Power Amplifier and Detector– HFA3683A – 2.4 GHz RF/IF Converter and Synthesizer

(RF/IF)– HFA3783 – IQ Modulator/Demodulator and Synthesizer (IF)– HFA3861B – Baseband Processor with Rake Receiver and

Equalizer (BBP)– HFA3842 – MAC

PRISM 2.5 (4 chip solution) 11 Mbps, 2.4 GHz, IEEE 802.11b

– ISL3984 – 2.4 GHz Power Amplifier and Detector (die shrinks)– ISL3685 – 2.4 GHz RF/IF Converter and Synthesizer

(die shrinks)

IEEE 802.11 Chipset (2)

– HFA3783 – IQ Modulator/Demodulator and Synthesizer– ISL3873 – Integrated MAC and Baseband Processor

PRISM 3 (2 chip solution ) 11 Mbps, 2.4 GHz, Direct Down Conversion architecture

– ISL3684 – Direct Up/Down Converter – Single Chip PHY– ISL3871 – Integrated Baseband/MAC

PRISM Indigo (4 chip solution) 54 Mbps, 5 GHz, IEEE 802.11a, HIPERLAN/2

– ISL3987 – 5 GHz Power Amplifier– ISL3877 – MAC with Baseband Processor– ISL3787 – 1.2 GHz IF/BB Converter with AGC and Synthesizer– ISL3687 – 5 GHz RF/IF Converter with Integrated Synthesizer

IEEE 802.11b (1)IEEE 802.11b (1)

IEEE 802.11b (2)IEEE 802.11b (2)

IEEE 802.11b 2.4GHz High Rate PHY SpecificationHigh rate extension of the PHY for the DSSS system

Direct Sequence Spread Spectrum frequency band: 2.4~2.4835GHz ISM band data rate: 1, 2, 5.5, 11Mbps modulation: DBPSK / DQPSK / CCK 11-chip Barker sequence

same occupied channel bandwidth same PLCP preamble and header

→ basic HR/DSSS and DSSS PHY can co-exist in the same BSS optional modes

CCK → PBCC(Packet Binary Convolutional Coding)shorter PLCP preamble mode (2, 5.5, 11M)

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1

IEEE 802.11b (3)

Modulation Modes

4 possiblespreading sequences

64 possiblespreading sequences

IEEE 802.11b (4) Long PLCP PPDU Format

SYNC: scrambled one’s (scrambler initial state: [1101100]) SFD: [1111 0011 1010 0000] preamble and header: 1Mbps DBPSK

Short PLCP PPDU Format shortSYNC: 56 bits scrambled zero’s (scrambler initial state: [0011011])

shortSFD: 16 bits backward SFD preamble: 1Mbps DBPSK / header: 2Mbps DQPSK – 96us

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits

PLCP Preamble144 bits

PLCP Header48 bits

PSDU

PPDU

192 us

- SIGNAL Field

X’0A’ / X’14’ / X’37’ / X’6E’

for 1 / 2 / 5.5 / 11 Mbps

- CRC Field16 12 5 1x x x

IEEE 802.11b (5) Block Diagram (DSSS)

Performance processing gain: 11 (10.4dB) AWGN / Indoor Model

DPSKmod

channelX +

PN code AWGN

CMF X

PN code

DPSKdemod

0 4 8 12 16Eb/N0

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

BE

R

AW G N

Analytica l

BPSK

Q P SK

D BPSK

D Q PSK

0 4 8 12 16Eb/N0

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

BE

R

AW G N

Saleh (Rake)

IEEE 802.11 MAC (1)

Multiple/random Access ProtocolALOHA : send packet, receive packet, send ACK packet success

if no ACK received during 200 ~ 1500ns, fail

then retransmit packet after random backoff delay

simple but low throughput(max. 18%) for a large

no. of stations

Multiple/random Access ProtocolSlotted ALOHA : max. throughput 37%

CSMA : Sense the status of a channel before transmitting (max. 80%)

CSMA/CD(IEEE 802.3, Ethernet) : sense the carrier by measuring the current or voltage in the cable

CSMA/CA(IEEE 802.11) : avoid collision by random backoff procedure

IEEE 802.11 MAC (2)

IEEE 802.11 MAC (3)

Coordination FunctionsDistributed coordination function(DCF) : contention –based protocol,CSMA/CA

DCF with handshaking (DFW : distribution four-way handshake)

if collision occurs, far less BW is wasted for a large data MPDU

hidden node problem(63%) can be alleviated

Point coordination function(PCF)

Contention-free(priority-based, polling) access protocol usable on infrastructure network containing a controller called a point coordinator within AP

DCF optionsNever use RTS/CTS

Use RTS/CTS whenever MSDU size > RTS_Threshold

Always use RTS/CTS

IEEE 802.11 MAC (4)

DCFCarrier sense mechanism

physical carrier sense (channel assessment)virtual carrier sense : duration field is placed

in the station’s Network Allocation Vector(NAV)

Inter Frame Space(IFS)Short IFS(SIFS) : highest priority level

ACK, CTS framePCF IFS(PIFS)DCF IFS(DIFS)

Large MSDU is broken up into multiple fragments

MediumBusy

SIFS

PIFS

DIFS

Time

< The Inter Frame Space(IFS) >

NAV=0 ?

Mediumidle ?

Collision?

Sense the medium(perform physical

channel assessment)

Transmit Frame

Random Backoff Time

Start(frame needing transmission)

No

Yes

Yes

No

Yes

No

< Flowchart of DCF >

IEEE 802.11 MAC (5)

rts

cts

fragment0

ack0

fragment1

ack1

sifs sifs sifs sifssifs

pifs

nav(rts) nav(fragment1)nav(cts) nav(ack1)

sifs

difs

source

destination

all

< RTS/CTS/Data/ACK transmission and NAV setting >

HIPERLAN/2 표준안

Core network independent with QoS support Support of IP transporting networks, ATM networks, 3rd Generation, Firewire, etc.

Radio access network specifications (physical layer, data link control layer and convergence layer)

Interoperability standard with conformance test specifications

A cellular multi-cell radio network capable of offering access, switching and management functions within a large coverage area

Centralized mode (mandatory) and direct mode (optional)

Mobility management

Power management

- Uplink power control, downlink power setting, sleep mode

Capable of handling different interference and propagation situations “Link Adaptation” with multiple modulation and channel coding schemes

HIPERLAN/2 Main Requirements (1)HIPERLAN/2 Main Requirements (1)

Supporting asymmetrical traffic load fluctuating in uplink and downlink as well as for different users

Range of radio cell: 30-40 m in a typical office indoor environment, 150 m in a large open indoor or typical outdoor environment

No frequency planning Dynamic Frequency Selection

Multicast and broadcast

HIPERLAN/2 Main Requirements (2)HIPERLAN/2 Main Requirements (2)

HIPERLAN/2 Protocol ArchitectureHIPERLAN/2 Protocol Architecture

Standardization scope : air interface, service interfaces of the radio access system and the convergence layer functions

Data Link Control - Basic Data Transport Function

(User plane)

Radio Link Control sublayer(Control plane)

Higher Layers

PPP/IP IEEE 1394 SSCS Ethernet SSCS

Packet based Common part CL

Physical Layer

RLC Error Control

Medium Access Control

ConvergenceLayer

Data LinkControl Layer

PhysicalLayer

Scope ofHIPERLAN/2standards

TDMA/TDD with a fixed frame duration of 2 ms

3 transmission possibilities: AP to MT (Downlink), MT to AP (Uplink), and MT to MT (Direct Link)

Centralized scheduling (not specified) Air interface frame creation in the AP Resource allocation by the AP Resource requests from MTs Dynamic assignment of capacity in uplink and downlink – no fixed slot structure Could consider QoS and link adaptation modes

Random access scheme Association and resource request transmissions from MTs Random access in mobile stations: slotted ALOHA

with exponential increase of contention window

Peer-to-peer and multicast support

Sector antenna support

HIPERLAN/2 DLC: Medium Access ControlHIPERLAN/2 DLC: Medium Access Control

Basic MAC Frame StructureBasic MAC Frame Structure

A Single Sector System

A Multiple Sectors System

Protocol Stack: RLC Functional EntitiesProtocol Stack: RLC Functional Entities

Association Control

Radio Resource Control

DLC User Connection Control

Main difference between 802.11a and HIPERLAN/2: Preamble due to different multiple access scheme Several physical layer modes are provided

Link Adaptation selects the “most appropriate” mode. Physical layer modes of HIPERLAN/2 & IEEE 802.11a:

Physical Layer ModesPhysical Layer Modes

Modulation Code rate Net bit rate System

BPSK 1/2 6 Mbps H/2 and IEEE

BPSK 3/4 9 Mbps H/2 and IEEE

QPSK 1/2 12 Mbps H/2 and IEEE

QPSK 3/4 18 Mbps H/2 and IEEE

16 QAM 1/2 24 Mbps IEEE

16 QAM 9/16 27 Mbps H/2

16 QAM 3/4 36 Mbps H/2 and IEEE

64 QAM 2/3 48 Mbps IEEE

64 QAM 3/4 54 Mbps H/2 and IEEE

OFDM 기본 이론

Transmission Techniques for Wireless LANTransmission Techniques for Wireless LAN

대역확산 (DSSS, FHSS) 협대역 마이크로웨이브 적외선 OFDM

주파수902 ~ 928 MHz

2.4 ~ 2.4835 GHz5.725 ~ 5.850 GHz

18.825 ~ 19.205 GHz3×1011 Hz

(LED 사용 )

5.15 ~ 5.24 GHz5.25 ~ 5.35 GHz

5.725 ~ 5.825 GHz

허가 불필요 (ISM 밴드 ) 필요 불필요 불필요

최대 도달 범위 105 ~ 800 ft(32 ~ 244 m)

40 ~ 130 ft(12 ~ 40 m)

30 ~ 80 ft(9 ~ 24 m)

80 ~ 600 ft(24 ~ 183 m)

장점

- 잡음이나 전파방해 간섭 에 강함- 보안성 강함- 사물투과 가능 (폐쇄 사무실 )

- 이더넷 데이터 전송률 (10Mbps) 구현 가능- 이 대역의 전자기적 장비없어 간섭 없음

- 속도 빠름- 전자기적 간섭 적음

- 속도 빠름- 사물투과 가능 ( 폐쇄 사무실 )

단점

-속도 느림 DSSS: Chip rate 높음 FHSS: 주파수 동기회로 구현 어려움

-다중경로 페이딩 해결위해 수신단 복잡

- 전달범위 작음 ( 가시거리 )-사물투과성 없음 ( 개방사무실 )- 햇빛에 민감

- FFT 구현 필요- 수신단 동기화부 복잡- 최대크기 대 평균크기가 큼

대표 제품( 회사 , 속도 )

Orinoco(Lucent, 11Mbps, DSSS)

Altair(Motorola, 10Mbps)

Infra LAN(BICC, 4.16Mbps)

IEEE 802.11a (54Mbps)HIPERLAN/2 (54Mbps)

Frequency Division Multiplexing

• entire bandwidth is divided into many narrow subchannels• serial-to-parallel conversion, parallel transmission• low bit rate transmission at each subchannel : flat fading• ideally bandlimited transmission spectrum: no ISI and ICI• practical case: guard band is needed lower bandwidth efficiency

Multicarrier Modulation (1)Multicarrier Modulation (1)

( )H f1

sT

f

Multicarrier Modulation (2)Multicarrier Modulation (2)

bandpass filter and oscillator bank

scheme 1: high complexity due to the filters with sharp transition scheme 2: orthogonally overlapped spectrum for high bandwidth efficiency

and lower filter complexity

Encoder Filter

Encoder Filter

Encoder Filter

f0

f1

fN-1

.

.

.

.

.

.

R/N b/s

R/N b/s

R/N b/s

R b/s

0 ( )x t

1( )x t

1( )Nx t

RF( )x t

. . .

f0

f1 f

N-1

ff2

Scheme 1

. . .

f0 f1 fN-1

ff2

Scheme 1

Orthogonal Frequency Division Multiplexing (1)Orthogonal Frequency Division Multiplexing (1)

QAM S/P

RF

Transmitter

R b/s

..

....

Time-LimitedSignals

(Block Processing) 1

0

( ) Re expN

n nn

x t X j t

nX

0X

1X

1NX

0f

1f

1Nf

( )x t

all subchannels are orthogonally overlapped without bandlimiting filter efficient implementation by use of IFFT / FFT transmission signal is rectangular windowed in time-domain each subchannel’s spectrum is sinc function

Orthogonal Frequency Division Multiplexing (2)Orthogonal Frequency Division Multiplexing (2)

Transmitter

P/S

t

0X 1X 2X 3X

sT

sym sT NT

3f

2f

1f

0f 0f

3f

2f

1f

0X

1X

3X

2X

Receiver

01

,nsym

f f n f fT

Cyclic Prefix (1)Cyclic Prefix (1)

OFDM symbol 1

OFDM symbol 2

( )h t

Delayed OFDM symbol 1

interferingregion

OFDM transmission is block processing inter-block interference (ISI) guard interval insertion between two

successive OFDM symbols zero-valued guard interval vs. cyclic prefix

OFDM symbol 1

OFDM symbol 2

( )h t

Delayed OFDM symbol 1

noiterference

Guard Interval

Cyclic Prefix (2)Cyclic Prefix (2)

GT subT

sym G subT T T

time

copy of NG samples

cyclic prefix

zero-valued guard interval cyclic prefix

no ISI but ICI no ISI and ICI

Filtering and WindowingFiltering and Windowing

Transmission Spectrum• no bandlimits in frequency-domain• rectangular window in time-domain • large spectrum outside transmission band

Filtering or Windowing• raised-cosine window in time-domain• bandlimit filter in frequency-domain

Virtual Carriers• unused subcarriers

COFDM (1)COFDM (1)

Frequency-Selective Fading Channel• deep fading over several subcarriers• burst error: error floor

OFDM combined with Forward Error Correction Coding• coded OFDM (COFDM)• convolutional coding and Reed-Solomon coding• concatenated coding, TCM, turbo coding• interleaving: bit or/and symbol or/and OFDM symbol

frequency

average SNR

requiredSNR

SNR

burst error

COFDMCOFDM

DataSource

OuterCoder

OuterInterleaver

InnerCoder Inner

InterleaverMapper

OFDMSystem

TCM

DataSink

OuterDecoder

OuterDeinterleaver

InnerDecoder Inner

DeinterleaverDemapper

VA

RS(204, 188, t=8)shortend code

correct up to 8error bytes in

204 bytes

RS(255, 239, t=8)original code

Convolutionalinterleaving

seperate errorbursts frominner coding

system

puncturedconvolutional

coding

mother code: 1/2, k=7C(71, 133)

puncturing: 1/2 ~ 7/8

All block-based time (bit-wise)

interleaving

symbol

frequency(symbol)

interleaver(permutation)

Multiple Access SchemesMultiple Access Schemes

For single carrier systems, multiple access techniques for multi-user system• FDMA, TDMA, CDMA (conflict-free access methods)

For OFDM systems• uplink and downlink : TDD• uplink : OFDM/TDMA• downlink : OFDM-FDMA, OFDM-TDMA, OFDM-CDMA

TDMA : centralized node (Hub)• CSMA : peer-to-peer

time

frequency

code

Spatial Division Multiple Access (SDMA)Spatial Division Multiple Access (SDMA)

Improves bandwidth efficiency System capacity increases with number of antennas

by exploiting spatial diversity Antenna array processing at base station for Tx and Rx OFDM reduces the complexity of baseband SDMA processing

wired backbone

Frame Structure of Spatially Extended MAC ProtocolFrame Structure of Spatially Extended MAC Protocol

Broadcast Downlink phase Uplink phase Random access

AC

H

SCH,LCH SCH,LCHPilottones SCH,LCH SCH,LCH

1MAC - Frame = 2 ms

Time domain

SCH: Short channelRCH-P: Random access channel - partitionedRCH-UP: Random access channel - unpartitionedTTA: Transceiver turnaround timeBCH: Broadcast channel

FCH TTA RCH-PRCH-UP TTA

Frame channel

OFDM/SDMA Architecture with OFDM/SDMA Architecture with Per-carrier ProcessingPer-carrier Processing

OFDMmodem

OFDMmodem

OFDMmodem

RFFront End

RFFront End

RFFront End

Pre/postcomp

r2

Pre/postcomp

r1

Pre/postcomp

rk

ApplicationsApplications

Military Application (1950’s – 1960’s)• KINEPLEX and Kathryn

Broadcasting• Digital Audio Broadcasting(DAB) , Digital Terrestrial TV Broadcasting(DVB)

Wired Communications (DMT)• Asymmetric Digital Subscriber Line(ADSL)• Very-High-Bit-Rate Digital Subscriber Line(VDSL)• Power-Line Communication

Wireless ATM and Wireless LAN• Magic WAND, IEEE 802.11a, HIPERLAN/2, IEEE 802.16, Wireless IEEE 1394

Cellular-based Communications• Advanced Cellular Internet Service(ACIS)

Disadvantages of Multicarrier Transmission• Sensitive to carrier frequency offset and timing offset• High PAR(peak-to-average ration), sensitive to nonlinear distortion

IEEE 802.11a

모뎀 설계

IEEE 802.11a PHY (1)IEEE 802.11a PHY (1) HIPERLAN/2 Physical layer : OFDM Frequency band : 5.15-5.24, 5.25-5.35, 5.725-5.825GHz 의 U-NII band Data rate : 6, 9, 12, 18, 24, 36, 48, 54 Mbps (variable rate); 6,12,24 Mbps (mandatory) Subcarriers : 52 (N=64) Modulation : BPSK/QPSK/16QAM/64QAM FEC : 1/2, 2/3, 3/4 convolutional code

Information data rate 6, 9, 12, 18, 24, 36, 48 and 54 Mbit/s (6, 12, 24 Mbit/s are mandatory)

Modulation

BPSK-OFDM QPSK-OFDM 16-QAM-OFDM 64-QAM-OFDM

Error Correction Code K=7 (64 states) Convolutional code Coding rate 1/2, 2/3, 3/4

Number of subcarriers 52 OFDM symbol duration 4.0 us

Guard interval 0.8 us (TGI)

Occupied Bandwidth 16.6 MHz

IEEE 802.11a PHY (2)IEEE 802.11a PHY (2)

IEEE 802.11a 무선 모뎀 블록도

Data Rate ModulationCoding rate

R

Coded bits per subcarrier

NBPSC

Coded bits per OFDM symbol

NCBPS

Data bits per OFDM symbol

NDBPS

6 Mbit/s BPSK 1/2 1 48 24

9 Mbit/s BPSK 3/4 1 48 36

12 Mbit/s QPSK 1/2 2 96 48

18 Mbit/s QPSK 3/4 2 96 72

24 Mbit/s 16QAM 1/2 4 192 96

36 Mbit/s 16QAM 3/4 4 192 144

48 Mbit/s 64QAM 2/3 6 288 192

54 Mbit/s 64QAM 3/4 6 288 216

IEEE 802.11a PHY (3)IEEE 802.11a PHY (3)

시간 관련 OFDM 심볼 파라미터

Parameter Value

Sampling rate fs=1/T 20 MHz

Useful symbol part duration TU

64*T

3.2 s

Cyclic prefix duration TCP

16*T

0.8 s (mandatory)

8*T

0.4 s (optional)

Symbol interval Ts80*T

4.0 s (TU + TCP)

72*T

3.6 s (TU + TCP)

Number of data sub-carriers NSD 48

Number of pilot sub-carriers NSP 4

Total number of sub-carriers NST 52 (NSD + NSp)

Sub-carriers spacing f 0.3125 MHz (1/ TU)

Spacing between the two outmost sub-carriers 16.25 MHz (NST* f )

Workstation area

Reception

Study cubiclesRoomServer

Office OfficeOfficeOfficeOffice

Conferance room

Study cubicles

OfficeOffice

Office

Main entrance

PC area

(Brick tiles on the floor)

Laboratory area

10 cm

20M15M

10M

5M

NA

Rx1

Measurement Site and Location of AntennasMeasurement Site and Location of Antennas

1

0

2

1

0

2

)(N

kk

N

kakk

m

c

c

Statistics of RMS Delay Spread (threshold=30dB)Statistics of RMS Delay Spread (threshold=30dB)

Ant. Sep. Mean Std. Dev Min Max

5MLOS 26.3 4.9 20.9 36.6

5MNLOS 66.2 12.1 49.1 87.3

10MLOS 44.4 7.7 28.4 61.9

10MNLOS 61.9 13.2 31.4 87.3

15MNLOS 64.7 7.3 43.1 78.7

20MNLOS 70.5 14.2 31.0 103.7

Performance of IEEE 802.11a (1)Performance of IEEE 802.11a (1)

Ideal Condition

- AWGN, Hard decision, Truncation depth = 35

- BPSK, QPSK :

- M - QAM :

0

2 bb

EP Q

N

12

22 0

2(1 ) 3log 2

log 1

bb

L L EP Q

L L N

( )L M

0 2 4 6 8 10Eb/N 0(dB)

1E -6

1E -5

1E -4

1E -3

1E -2

1E -1

1E +0

BE

R

B P S K

A na lytic

N o cod ing (64)

N o cod ing (48)

1 /2 cod ing

3/4 cod ing

0 2 4 6 8 10Eb/N 0(dB)

1E -6

1E -5

1E -4

1E -3

1E -2

1E -1

1E +0

BE

R

Q P S K

A na lytic

N o cod ing (64)

N o cod ing (48)

1 /2 cod ing

3/4 cod ing

0 4 8 12 16Eb/N 0(dB)

1E -6

1E -5

1E -4

1E -3

1E -2

1E -1

1E +0

BE

R

16Q AM

A nalytic

N o cod ing (64)

N o cod ing (48)

1 /2 cod ing

3/4 cod ing

0 4 8 12 16 20Eb/N 0(dB)

1E -6

1E -5

1E -4

1E -3

1E -2

1E -1

1E +0

BE

R

64Q AM

A nalytic

N o cod ing (64)

N o cod ing (48)

2 /3 cod ing

3/4 cod ing

AWGN Indoor Channel

Performance of IEEE 802.11a (2)Performance of IEEE 802.11a (2)

0 4 8 12 16Eb/N 0(dB)

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

BE

R

AW G N

6 M bps

9 M bps

12 M bps

18 M bps

24 M bps

36 M bps

48 M bps

54 M bps

0 4 8 12 16 20Eb/N 0(dB)

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

BE

R

Channel+AW G N

6 M bps

9 M bps

12 M bps

18 M bps

24 M bps

36 M bps

48 M bps

54 M bps

IEEE 802.11a PLCPIEEE 802.11a PLCP

PLCP Transmit Procedure

PLCP Receive Procedure

IEEE 802.11a PLCP Frame FormatIEEE 802.11a PLCP Frame Format

IEEE 802.11a 의 PPDU 프레임 포맷

IEEE 802.11a 훈련신호

t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 CP L1 L2

(1) (2) (3)

(1) Signal Detection, AGC

(2) Estimate Coarse Carrier Frequency Offset

Estimate Symbol Timing Offset

(3) Estimate Fine Carrier Frequency Offset

Estimate Channel

IEEE 802.11a PreambleIEEE 802.11a Preamble

Short Training Symbol (B)

}1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1

,1,1,1,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1{26,26

L

Long Training Symbol

0 10 20 30 40 50 60F re q u e n c y S h ift

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Abs

olut

e V

alue

0 10 20 30 40 50 60T im e S h ift

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Nor

mal

ized

Abs

olut

e V

alue

0 10 20 30 40 50 60T im e

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

Mag

nitu

de

IEEE 802.11a Training SymbolsIEEE 802.11a Training Symbols

26,26 13/ 6 *{0,0,1 ,0,0,0, 1 ,0,0,0,1 ,0,0,0, 1 ,0,0,0, 1 ,0,0,0,1 ,0,0,0,

0,0,0,0, 1 ,0,0,0, 1 ,0,0,0,1 ,0,0,0,1 ,0,0,0,1 ,0,0,0,1 ,0,0}

S j j j j j j

j j j j j j

0 8 16 24 32 40 48 56 64Frequency Shift

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Abs

olut

e Va

lue

0 8 16 24 32 40 48 56 64T ime Shift

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Abs

olut

e Va

lue

0 8 16 24 32 40 48 56 64T ime Shift

0.06

0.08

0.10

0.12

0.14

Mag

nitu

de

HIPERLAN/2 Broadcast Burst PreambleHIPERLAN/2 Broadcast Burst Preamble

Enables

signal detection, automatic gain control

symbol timing synchronization

(coarse and fine) carrier frequency synchronization

channel estimation and equalization

Preamble has a low PAR (3dB) so nonlinearities of PA do not affect AGC

Copy

A CCPIBBBBBIAIAAIA C

5* 0.8μ s=4.0μ s 5* 0.8μ s=4.0μ s 2* 0.8μ s+2* 3.2μ s=8.0μ sSection 1 Section 2 Section 3

tPREA MBL E=16.0μ s

H/W Block Diagram for IEEE 802.11a ModemH/W Block Diagram for IEEE 802.11a Modem

VCO VCO OSC

Frequency SynthesizerFrequency Synthesizer

I/Q LO

RSSI

RXI

RXQ

TXI

TXQ

BPF

BPF

BPF

BPF

BPF

BPF

BPF

LPF

LPF

UP/DOWNmixer

UP/DOWNmixer

1st LNA

HPA PreAmp.

2nd LNA IF Amp

IF AGC

AGCCTL

OFDMDEMOD

I/O

OFDMMOD

TXALC

Q ADC

I ADC

I DAC

Q DAC

TX DAC

TX ADC

RX ADC

RX DAC

ExternalMemory

HostInterface

MACController

OFDM ModemChip

H/W Block Diagram for OFDM Modem ASICH/W Block Diagram for OFDM Modem ASIC

RAM

counteraddress-

generator

8

Modulator

din

imag

start_sp

clk_RC

clk_RI

rst

CE

RD

WE

S/P

RAM

counteraddress-

generator

X

24

16 16

1/H(k)

Demo-dulator

real

imag

real8

imag8

start_psclk_Rc

rst

CE

RD

WE

Deinterleaver P/S Convertor Demodulator Equalizer FFT TOP BLOCK(R4SDC)

Removing CyclicPrefix

IFFT TOP BLOCK(R4SDC)

Adding Cyclic Prefix(16 symbols)

Adding virtualcarrier(12)

Pilot tones(4)

ModulatorS/P

ConvertorInterleaver

Removing virtualcarrier(12)

Pilot tones(4)

P/S16/

16/

RS 20MHz

20MHzRs

Convolutional

EncoderData

SourceVariable

/

clk_Rs

RC RI

VitebiDecoder

DescramblerDataSink

clk_Rs

clk_RI

Rc RI

Scrambler

ViterbiDecoderDescramblerData Sink

ConvolutionalEncoder

ScramblerData

Source

variable

Guard IntervalInsertion

RAM

(12 x 53) bit

Windowing

DAC

DAC

8/

8/

TxI

TxQ

Windowing Digtal/AnalogConverter

Synchro-nizationBlock

ADC

ADC

8/

8/

SynchronizationBlock

Analog/DigitalConverter

RxI

RxQ

VirtualCarrier &Pilot Tones

Remove

GuardIntervalRemove

VirtualCarrier &Pilot TonesInsertion

8real

RAM

( 28bit X 64)

RAM

( 28bit X 64)

De-MUX

0

1

MUX

0

1

ADDRESSGenerator

6

ADDRESSGenerator

6

16

28

28 28

28SDC(16)

SDC(16)

R4SBF

ComplexMultiplier

SDC(4)

SDC(4)

R4SBF

ComplexMultiplier

SDC(1)

SDC(1)

R4SBF

8

8

TwiddleFactor

TwiddleFactor

Control Block

RAM

( 28bit X 64)

RAM

( 28bit X 64)

De-MUX

0

1

MUX

0

1

ADDRESSGenerator

6

ADDRESSGenerator

6

16

28

2828

28 SDC(16)

SDC(16)

R4SBF

ComplexMultiplier

SDC(4)

SDC(4)

R4SBF

ComplexMultiplier

SDC(1)

SDC(1)

R4SBF

8

8

TwiddleFactor

TwiddleFactor

Control Block

Development Environment for Development Environment for OFDM MODEM ASIC ChipOFDM MODEM ASIC Chip

Floating Point Simulation• SPW, C, MATLAB 을 사용한 OFDM 모뎀의 각 블록 설계• 무선 채널 simulator 를 사용하여 설계된 각 블록의 성능 분석

Fixed Point Simulation• Fixed Point Simulator 를 설계하여 각 블록의 최적 bit 수 결정

- ADC, DAC, FFT(external, internal), Equalizer, 동기부 ( symbol, coarse/fine frequency offset, estimator, compensator, tracking)

VHDL Coding 을 사용한 FPGA 구현• APEC 100 만 Gate, QUARTUS

ASIC Chip 설계• I&C Tech 와 중앙대 개발 • 현대 0.25 um 공정• 208 MQFP package• Soft-decision Viterbi detector• Full-digital synchronization and tracking• On-chip ADC and DAC

Block Diagram of OFDM ASIC ChipBlock Diagram of OFDM ASIC Chip

IEEE 802.11 vs. HIPERLAN/2IEEE 802.11 vs. HIPERLAN/2

Characteristics 802.11 802.11b 802.11a HIPERLAN/2

Modulation FH/DSSS DSSS OFDM OFDM

Carrier frequency 2.4 GHz 2.4 GHz 5 GHz 5 GHz

Max. physical rate 2 Mb/s 11 Mb/s 54 Mb/s 54 Mb/s

Max. data rate, layer 3 1.2 Mb/s 5 Mb/s 32 Mb/s 32 Mb/s

Medium access control/ Media sharing

CSMA/CA CSMA/CA CSMA/CACentral resource control

/ TDMA / TDD

Connectivity Conn.-less Conn.-less Conn.-less Conn.-oriented

Multicast Yes Yes Yes Yes

QoS support PCF PCF PCFATM / 802.1p / RSVP/ DiffServ (full control)

Authentication No No No No

Encription 40-bit RC4 40-bit RC4 40-bit RC4 DES, 3DES

Handover support No No No No

Fixed network support Ethernet Ethernet EthernetEthernet, IP, ATM,

UMTS, FireWire, PPP

Management 802.11 MIB 802.11 MIB 802.11 MIB HIPERLAN/2 MIB

Radio link quality control No No No Link Adaptation

초고속 무선 초고속 무선 LAN LAN 요소기술요소기술분 류 내 용 비 고

안테나 및RF 기술

o 5GHz Access Point/ 단말 카드용 안테나o 5GHz SSPA 칩 및 CMOS RF 트랜시버 (LAN 내장 ) 칩o Access Point 용 섹터 / 적응 능동형 안테나

모뎀 및 MAC 칩기술

o IEEE 802.11a 및 HIPERLAN/2 모뎀 칩o IEEE 802.11a 및 HIPERLAN/2 MAC 프로세서 칩 (54Mbps)

o 모뎀 및 MAC 프로세서 통합 칩

무선 LAN

고도화 기술

o QoS 지원 MAC 프로토콜 고도화 기술o DFS 및 TPC 기술o 물리계층 / 모뎀 성능 개선 기술 - 송신 / 수신 다이버시티 , MIMO, OFDM/SDMA 기술 - 적응형 변조 , 등화 기술 - PAPR 및 비선형 특성 대책 기술o 무선 LAN 에서의 TCP 성능 개선 기술o 5GHz 무선 LAN 단일 표준화 기술 - 통합 Access Point(802.11a 및 H/2 동시 지원 ) 기술 - 통합 MAC 프로토콜 기술

- 모뎀 및 MAC 칩 기 술 개발과 연계 - Access Point

및 단 말 카드 개발 표함

이동성 지원및 핵심망연동 기술

o 무선 LAN Macro 및 Micro 이동성 지원 기술o IMT-2000 시스템 연동기술o IEEE1394 연동 ( 무선 1394) 기술

 

※ 전파연구소 「 5GHz 무선 접속망 TFT 」중간보고서 참조

ETSI BRAN, Broadband Radio Access Networks(BRAN); HIgh Performance Radio Local Area Network (HIPERLAN) Type 2; requirements and architectures for wireless broadband access and interconnection, TR 101 031 v2.2.1 Jan. 1990

ETSI BRAN, Broadband Radio Access Networks(BRAN) HIPERLAN Type 2; Physical (PHY) layer, TS 101 475 v1.2.1 Nov. 2000

ETSI BRAN, Broadband Radio Access Networks(BRAN) HIPERLAN Type 2; Data Link Control (DLC) Layer Part 1: Basic Data Transport Functions, TS 101 761-1, v1.1.1 Apr. 2000

ETSI BRAN, Broadband Radio Access Networks(BRAN) HIPERLAN Type 2; Data Link Control (DLC) Layer Part 2: Radio Link Control (RLC) sublayer, TS 101 761-2, v1.1.1 Apr. 2000

IEEE 802.11a, High Speed Physical Layer in the 5 GHz Band, 1999 ETSI BRAN web page, http://www.etsi.org/bran IEEE 802.11 web page, http://grouper.ieee.org/groups/802/11 OFDM Forum web page, http://OFDM-Forum.com HIPERLAN2 Global Forum web page, http://hiperlan2.com 무선 멀티미디어 통신을 위한 OFDM 기초 , 대영사 , 2001 이동통신용 모뎀의 VLSI 설계 - CDMA, OFDM, MC-CDMA, 대영사 , 2001 IEEE 802.11a 고속 무선 LAN 모뎀 기술 , 한국통신학회지 , 16권 10호 , pp. 42-63, 1999 무선 LAN 기술 동향 (HIPERLAN/2), 한국통신학회지 , 17권 11호 , pp. 1566-1581, 2000 광대역 무선 액세스 특집 , 한국통신학회지 , 18권 4호 , 2001

ReferencesReferences