next generation wlan
TRANSCRIPT
Next Generation WLANNext Generation WLAN
Samsung Advanced Institute of Samsung Advanced Institute of TechnologyTechnology
2005.01.272005.01.27
Dr.Dr. KyungHun JangKyungHun Jang
Global TrendsOu
tdoo
r
Fixed
Walk
Vehicle
Indo
or
Fixed/Desktop
Walk
Mobility
Wired LAN
High performance WLAN
802.11a/g
802.11b
WLAN
Mbps (PHY layer)1 10 1000,1
UMTSWideband Cellular
WANGS
M, IS
-95,
D-AM
PS
Bluetooth
802.11n
802.11 Data Rate
Rate, Mbps Single/Multi Carrier Mandatory Optional Mandatory Optional Mandatory Optional
1 Single Barker Barker
2 Single Barker Barker
5.5 Single CCK PBCC CCK PBCC
6 Multi OFDM CCK-OFDM OFDM
9 Multi OFDM, CCK-OFDM OFDM
11 Single CCK PBCC CCK PBCC
12 Multi OFDM CCK-OFDM OFDM
18 Multi OFDM, CCK-OFDM OFDM
22 Single PBCC
24 Multi OFDM CCK-OFDM OFDM
33 Single PBCC
36 Multi OFDM, CCK-OFDM OFDM
48 Multi OFDM, CCK-OFDM OFDM
54 Multi OFDM, CCK-OFDM OFDM
802.11b @2.4GHz 802.11g @2.4GHz 802.11a @5GHz
Regional Regulation for 2.4GHz
OFDM PHY frequency channel plan for the United States
OFDM in 802.11a
• OFDM with 52 used subcarriers (64 in total)• 48 data + 4 pilot (plus 12 virtual subcarriers)• 312.5 kHz spacing
802.11 - Infrastructure Mode
Distribution System
Portal
802.x LAN
AccessPoint
802.11 LAN
BSS2
802.11 LAN
BSS1
AccessPoint
• Station (STA)
– Wireless terminals
• Basic Service Area (BSA)
– Coverage area of one access point
• Basic Service Set (BSS)
– group of stations controlled by the same AP
• Distribution System (DS)
– Fixed infrastructure used to connect several BSS to create an Extended Service Set (EES)
• Portal
– bridge to other (wired) networks
STA1
STA2 STA3
ESS
802.11 – Ad Hoc mode
802.11 LAN
BSS1
STA1STA3 • Terminals communicate in a peer-
to-peer basis.
STA2
802.11 LAN
BSS2
STA5
STA4
802.11 Reference Model
StationManagement
Entity(SME)
MAC Sublayer
PLCP Sublayer
PMD Sublayer
MAC ManagementSublayer Entity
(MLME)
PHY ManagementSublayer Entity
(PLME)
MAC SAP
PHY SAP
PMD SAP
MLM
E S
AP
PLM
E S
AP
MAC
PHY
IEEE 802.2Logical Link Control
(LLC)
MLME_PLME SAP
Distributed Coordination Function (DCF)
Contentionwindow
DIFS
• DCF provides basic access service
– Asynchronous best-effort data transfer
– All stations contend for access to medium
• CSMA-CA
– Ready stations wait for completion of transmission
– All stations must wait Interframe Space (IFS)
PIFSDIFS
SIFS
Next frame
Defer access Wait for reattempt time
Busy medium
Time
Slot Time SIFS PIFS DIFS
802.11a 9 usec 16 usec 25 usec 34 usec
802.11b 20 usec 10 usec 30 usec 50 usec
Point Coordination Function (PCF)
CF End
NAV
PIFS
B D1 + Poll
SIFS
U 1 + ACK
D2+Ack+Poll
SIFS SIFS
U 2 + ACK
SIFS SIFS
Contention-free repetition interval
Contention period
CF_Max_duration
Reset NAV
TBTT
D1, D2 = frame sent by point coordinatorU1, U2 = frame sent by polled stationTBTT = target beacon transmission timeB = beacon frame
802.11b frame
0000 0101 1100 1111
scrambled “0” bits(seed: 0011011)
scrambled “1” bits(seed: 1101100)
1111 0011 1010 0000
802.11a frame
16usec 4usec
Security
• Wired Equivalent Privacy (WEP)– The objective is to provide confidentiality
similar to wired LAN.
• WEP is used to provide two types of security:– Authentication (to prevent unauthorized access
to the network)
– Encryption (to prevent eavesdropping)
• WEP uses an encryption algorithm based on RC4.
Basic Idea of RC4
Pseudo-random number generatorEncryption Key K
Plaintext bit stream p
Random bit stream b
⊕Ciphertext bit stream
cXOR
Decryption works in the same way: p = c ⊕ b
WEP
Shared Key Authentication It is assumed that the station and the AP somehow agrees on a shared secret key via a channel independent of IEEE 802.11.
Authentication Request (shared key)
128-byte “Challenge” text string, generated randomly
“Challenge” text string, encrypted with shared key
Station Access PointPositive or negative response based on decryption resultNote: “Challenge” is
encrypted by WEP algorithm.
표준화 기구(IEEE 802.11 WG)
PHYLayer
802.11 IR(1, 2Mbps)
2.4GHz(FHSS)Frequency Hopping Spread Spectrum
Infra-Red(IR)
2.4GHz(DSSS)Direct Sequence Spread Spectrum
802.11 FHSS(1, 2Mbps)
802.11 DSSS(1, 2Mbps)
5GHz(OFDM)Orthogonal Frequency Division Multiplexing
802.11a / TGaHigh Data Rate Extension
6,12,24 MbpsOptional 9,18,36,54Mbps
802.11 TGbHigh Data Rate Extension
(5 , 11Mbps)
MACLayer
802.11e / TGeMAC Enhancements - QoS
802.11i / TGiEnhanced Security Mechanisms
802.11f / TGfInter-Access Point Protocol
802.11 MAC
802.11h / TGhSpectrum Managed
802.11a
802.11b-cor1V/VTGb-cor1 Corrigendum MIB
802.11g / TGg(Data Rates > 20Mbps)
표준화 기구(IEEE 802.11 WG)
802.11n / TGn
WNGSC
High Data Rate
Radio Resource Measurement 802.11k / TGk
Fast Roaming 802.11r / TGr
ESS Mesh Networking 802.11s / TGs
Wireless Access for the Vehicle Environment 802.11p / TGp
Wireless Interworking withExternal Networks 802.11u / TGu
Wireless Performance Prediction 802.11t / TGt
Wireless Network Management 802.11v / TGv
Advanced Security ADS SG
AP Functionality APF ADHOC
Physical Layer
802.11a5GHzOFDM
54Mbps
802.11n100MHz
19991999 20012001 20032003 20052005 20072007
802.11g2.4GHz
CCK or OFDM11Mbps
802.11b2.4GHz
CCK11Mbps
Regulatory
802.11hEuropean RegulatoryExpansions
802.11dInternational
Roaming
20002000 20012001 20022002 20032003 20042004
802.11jJapanese RegulatoryExpansions
802.11c802.11 Bridging Tables
Incorporated into802.11d
Enhancement
802.11fInter-Access
Point Protocols
802.11eQuality ofService
20022002 20032003 20042004 20052005 20062006
802.11kRadio ResourceMeasurement
802.11iEnhancedSecurity
Wi-Fi Protected Access
Security-subset of802.11i Draft
802.11i
TKIP
* The MIC is based on seed value, destination MAC, source MAC, and payload* Any change to these will change MIC value
Authentication
802.11e
Access Category
EDCA mechanism
AC_VO [0] AC_VI [1] AC_BE [2] AC_BK [3]
AIFSN 2 2 3 7
CWmin 3 7 15 15
CWmax 7 15 1023 1023
DLP (Direct Link Protocol)
Immediate Block ACK
Delayed Block ACK
Hot Issues on IEEE 802.11
• 802.11n– Conexant, Intel, Broadcom, TI, Motorola, Sony, Samsung,
Atheros, Philips, Nokia, Nortel, Qualcom, Cisco, Airgo, Toshiba, Sanyo, Parasonioc, Mitubishi, Agere, etc.
• 802.11s– Motorola, Intel, BelAir, Nortel
• 802.11r– Symbol, Spectralink, Nokia, Nortel, STMicro, Trapez
Networks, NTT-DoCoMo, FranceTelecom, InterDigital, Agere
• 802.11u– Siemens, Qualcom, Nokia, FranceTelecom
CE Applications Helping to Define 802.11n
• Critical needs of CE products are shaping the expectations from the next 802.11 extension
• Robustness is paramount
• The Wi-Fi enabled CE industry will build upon these expectations
10 Mb/s
Throughput
SIR
Enterprise andBusiness
ConsumerElectronics &Multimedia
Hotspots
100 Mb/s
802.11a/g
802.11n Target
Target HT Robustness (rate Target HT Robustness (rate vsvs Signal to Interference Ratio (SIR)) vs. 802.11a/gSignal to Interference Ratio (SIR)) vs. 802.11a/g
Source: IEEE 802.11 WG DocumentsSource: IEEE 802.11 WG Documents
IEEE 802.11n
• The scope of this projectThe scope of this project is to define an amendment that shall define standardized modifications to both the 802.11 physical layers (PHY) and the 802.11 Medium Access Control Layer (MAC) so that modes of operation can be enabled that are capable of much higher throughputs, with a maximum throughput of at least 100Mbps, as measured at the MAC data service access point (SAP).
IEEE 802.11n
• The purpose of this projectThe purpose of the project is to improve the 802.11 wireless local area network (LAN) user experience by providing significantly higher throughput for current applications and to enable new applications and
market segments.
IEEE 802.11n
• Two big alliance groups– TGnSync
– WWiSE
• Big challenges…– MIMO-OFDM
– Channel Bonding
– Advanced Coding
– Aggregation
MIMO-OFDM boosts performancesin frequency selective environments
MIMOoffers:
-10 -5 0 5 10 15 20 25 300
2
4
6
8
10
12
14
16
18
20
Nt = Nr = 1Nt = Nr = 2Nt = Nr = 3Nt = Nr = 4Nt = Nr = 5Nt = Nr = 6
SISO
MIMOor
SISOCapacity
(bit/s/Hz)
SNR (dB)
MIMO 2x2
3x3
4x4
1x1
-10 -5 0 5 10 15 20 25 300
2
4
6
8
10
12
14
16
18
20
Nt = Nr = 1Nt = Nr = 2Nt = Nr = 3Nt = Nr = 4Nt = Nr = 5Nt = Nr = 6
SISO
MIMOor
SISOCapacity
(bit/s/Hz)
SNR (dB)
MIMO 2x2
3x3
4x4
1x1
Higher capacitySDM, SDMA
HStream 1
Stream N
Stream 1
Stream N… … … …HStream 1
Stream N
Stream 1
Stream N… … … …Higher robustnessDiversity (MRC, STBC)
H Stream 1Stream 1
…
HStream 1 Stream 1
…
H Stream 1Stream 1
…H Stream 1Stream 1
…
HStream 1 Stream 1
… HStream 1 Stream 1
…
Frequency
Mag
nitu
de
A wide variety of MIMO schemes are available
SDM
s1 s2
s1 s2
TX-SDM
SDMA
s1 s2
s1 s2
TX-SDMA
MRC
s1
s1
TX-MRC
STBC
s1
s1
STBC
STBC
STBC
s1
s1
STBC
stbc
Downlink H H H
SDMA
s1 s2
s1 s2
RX-SDMA
SDM
s1 s2
s1 s2
RX-SDM
MRC
s1
s1
RX-MRC
STBC
s1
s1
STBC
STBC
Uplink
• OEM / System Vendors– Cisco– Mitsubishi Electric– Nokia– Nortel– Panasonic– Samsung– Sanyo– Sharp– Sony– Toshiba– Wavebreaker/ATcrc– Wavion
• Semi Vendors– Agere– Atheros– Intel– Marvell– Philips– Qualcomm
PC
Enterprise
Consumer Electronics
Asia
Pacif
ic / E
urop
e / N
orth
Am
erica
Semiconductor
Handset
Public Access
Academia• Academia
– Infocomm– Tohoku University
TGnSync members
PHY Features of TGnSync• Mandatory Features:
– 1 or 2 Spatial Streams
– 20MHz and 40MHz* channelization
– 1/2, 2/3, 3/4, and 7/8 channel coding rates
– RX assisted Rate Control
– Optimized Interleaver for 20 & 40MHz
– 400ns & 800ns Guard Interval
– Full & seamless interoperability with a/b/g
• Optional Features:– Transmit Beamforming
– Low Density Parity Check (LDPC) Coding • Completed merger process with LDPC partial proposals
– support for 3 or 4 spatial streams
140Mbps in 20MHz
243Mbps in 40MHz
*Not required in regulatory domains where prohibited.
MAC Features of TGnSync• Mandatory Features:
– MAC level aggregation
– RX assisted link adaptation
– QoS support (802.11e)
– MAC header compression
– Block ACK compression
– Legacy compatible protection
– 20/40 MHz channel management
• Optional Features:– Bi-directional data flow
– MIMO RX Power management
TGnSync Aggregation- MPDU Aggregation
• Robust Structure• Aggregation is a purely-MAC function
– PHY has no knowledge of MPDU boundaries– Simplest MAC-PHY interface
• Control and data MPDUs can be aggregated
TGnSync Aggregation- MSDU Aggregation
•Efficient Structure
•MSDUs of the same TID can be aggregated
•MSDUs with differing SA/DA can be aggregated
WWiSE members
• Airgo Networks
• Broadcom
• Buffalo
• Conexant
• ETRI
• Hughes Network Systems
• Realtek
• STMicroelectronics
• Texas Instruments
• TrellisWare
• Winbond
PHY/MAC Features of WWiSE
• WWiSE proposes 2 transmitters in 20 MHz mandatory– Rates 54, 81, 108, 121.5, 135 Mbps
• Optional 40 MHz counterparts of all 20 MHz modes
• Optional extensions to 3 and 4 transmit antennas
• Optional space-time block codes for longer range
• Optional LDPC code
• MAC: HTP burst, aggregation, extended Block
WWiSE Aggregation
802.11e TXOP Access delay M1 M2 M3 M4 breq
ACK M1 M2 M3 M4 back
ACK
WithAggregation
Access delay M1 M2 M3 M4 breq
ACK M1 M2 M3 M4 back
ACK
WithHTP Burst Access delay M1 M2 M3 M4 breq
ACK M1 M2 M3 M4 back
ACK
WithHTP Burst& No-ACKBlock Ack
Access delay M1 M2 M3 M4 breq
M1 M2 M3 M4 back
HTP Burst of WWiSE
PSDUNs PSDUNs PSDUNs xIFS
No idle gap Optional normal ACK policy
Non-normal ACK
Np
PSDU can be an aggregate MSDU!
= N-PreambleNp Last PSDU bit set
Ns = N-Signal field @ robust encoding rate
• Multiple RA allowed within the burst• Block Ack Request and Block Ack frames allowed within
burst
• More IFS eliminated• RIFS and ZIFS allowed within burst
• PHY overhead reduced• “Last PSDU” bit indicates receiver should revert to preamble search
Comparisons (1)
Features TGnSync WWiSE
Bandwidth extension
20MHz 40MHz mode
(M) 20MHz mode(M) 40MHz, whenever regulatory
domain permits this extension
(M) 20 MHz mode
(O) 40 MHz mode
MIMO-OFDM-SDM (M) 2 spatial streams@ 20MHz mode
(M) 2 spatial streams@ 20MHz mode
Higher order modulation scheme
(O) 256 QAM (ABF-MIMO mode) (N)
Adaptive modulation (O) Bit loading (+ 256 QAM)
+ power weighting (ABF-MIMO)
(N)
Guard interval (GI) shortening ( 0.8us 0.4us )
(M) (N)
Higher code rate (R) (M) R= ½, 2/3, ¾, 7/8 (M) R= ½, 2/3, ¾, 5/6
Reserve more data tones (M) 48 (4 pilots) @ 20MHz
(M) 108 (6 pilots) @ 40MHz
(M) 54 (2 pilots) @ 20MHz
(O) 108 (4 pilots) @ 40MHz
(M) Mandatory (O) Optional (N) Not available
Comparisons (2)(Maximum achievable uncoded data rate @ 64QAM)
TGnSync WWiSE
20 MHz BW + 2 Tx (M) 108 (R=3/4)
(M) 140 (R=7/8 with ½ GI)
(M) 121.5 (R=3/4)
(M) 135 ( R=5/6 )
20 MHz BW + 4 Tx (O) 280 (R=7/8 with ½ GI) (O) 270 ( R=5/6 )
40 MHz BW + 2 Tx (M) 243 (R=3/4 )
(M) 315 (R=7/8 with ½ GI)
(O) 243 (R=3/4)
(O) 270 (R=5/6)
40 MHz BW + 4 TX (O) 630 (R= 7/8 with ½ GI) (O) 540 (R=5/6 )
(M) Mandatory (O) Optional
Observations:(1). T > W, between “R=7/8 with ½ GI” for T and “R=5/6” for W.(2). W >= T, at “ R=3/4 & 2Tx”
Comparisons (3)
Features TGnSync WWiSE
Bandwidth extension (M) (O)
Mandatory coding scheme (M) Convolutional code (M) Convolutional code
Advanced Coding scheme (O) LDPC
(O) RS+Conv (removed)
(O) LDPC
(O) Turbo
Duplicate format @ 40 MHz (O) 6Mbps BPSK, (R = ½) (N)
Spatial processing
a. Eigenvector steering (ES)
b. Spatial spreading (SS)
(O) SVD_MIMO
(O) Walsh+CS
(N)
(N)
Space Time Block Code (STBC) (N) (O)
(M) Mandatory (O) Optional (N) Not available
IEEE 802.11s
• The scope of this projectTo develop an IEEE 802.11 Extended Service Set (ESS) Mesh* with an IEEE 802.11 Wireless Distribution System (WDS) using the IEEE 802.11 MAC/PHY layers that supports both broadcast/multicast and unicast delivery over self-configuring multi-hop topologies.
IEEE 802.11s
• The purpose of this projectThe purpose of the project is to provide a protocol for auto-configuring paths between APs over self-configuring multi-hop topologies in a WDS to support both broadcast/multicast and unicast traffic in an ESS Mesh using the four-address frame format or an extension.
Possible Major Functional Components for 802.11s
IEEE802.11 a/b/g/j/n
MAC/MLME enhancement for .11s Mesh
Layer 2 Mesh Routing and Forwarding
.11s Mesh Security
IEEE802.11 MAC
IEEE802.11 PHY
.11s Mesh Network
Measurement
IEEE802.11s Amendment
InternetworkingConfiguration/ Management
Interfaces
Key Issues for 11s• Mesh Discovery and Mesh Link Establishment Issues
• Mesh discovery by a new Mesh Point• Link establishment between Mesh Points
• Mesh Media Access Coordination Issues• Manage interference to improve spatial reuse• Hidden terminal problem• Exposed terminal problem• Lack of flow control • Efficient scheduling across multi-hop forwarding path• Distributed admission control• Distributed QoS traffic management• The potential problem of mixing BSS traffic and forwarding traffic• Scalability to work across different usage scenarios• Channelization potential for single radio• Multi-radio support
References
• IEEE 802.11 WG standard documents, http://grouper.ieee.org/groups/802/11/
• IEEE 802.11 WG technical documents, http://802wirelessworld.com
Source: IEEE 802.11 WG DocumentsSource: IEEE 802.11 WG Documents