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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



22 Single PBCC


33 Single PBCC




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

WithHTP Burst Access delay M1 M2 M3 M4 breq


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