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초고속 무선 초고속 무선 LAN LAN 기술 동향기술 동향
2001. 9. 11
중앙대학교 전자전기공학부디지털통신 연구실
조 용 수
(02) [email protected]
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