RISET DAN PERKEMBANGAN TEKNOLOGIWIRELESS ACCESS NETWORKS

Adit Kurniawan (adit@stei.itb.ac.id)PROGRAM STUDI/KK TEKNIK TELEKOMUNIKASI

INSTITUT TEKNOLOGI BANDUNG

OUTLINES SEMINAR

• Introduction• Perkembangan dan evolusi teknologi wireless

access networks• Enabling technologies• Riset wireless access network• Penutup dan diskusi/tanya jawab

INTRODUCTION

TOPIK SEMINAR

EVOLUSI DAN PERKEMBANGAN TEKNOLOGI WIRELESS TELECOMMUNICATION

Evolusi standard/teknologi asksesEDGE

GPRSGSM HSCSD

cdmaOne(IS-95)

WCDMA FDD

HSDPA/HSUPA

cdma2000

TD-SCDMA TDD LCR

cdma20001XEV - DO

cdma20001XEV - DV

TD-CDMA TDD HCR

HSDPA/HSUPA

LTE

Mobilitas v/s Data rates

WiMAX – EKSPANSI COVERAGE

• World Interoperability for Microwave Access• There are two main applications of WiMAX:

1) Fixed WiMAX (IEEE 802.16-2004) - Fixed WiMAX applications are point-to-multipoint enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL for homes and businesses.

2) Mobile WiMAX (IEEE 802.16e-2005) - Mobile WiMAX offers the full mobility of cellular networks at true broadband speeds.

FIXED - WiMAX

Fixed WiMAX Architecture

FIXED - WiMAX

Mobile WiMAX Architecture

LTE – EKSPANSI DATA RATE

•LTE is the latest standard in the mobile network technology tree that previously realized the GSM/EDGE and UMTS/HSxPA network

• Characteristics :

Significantly increase peak data rates, scaled linearly according to spectrum allocation

improving spectral efficiencylowering costsimproving servicesmaking use of new spectrum opportunitiesImproved quality of servicebetter integration with other open standards

LTE Network Architecture

Wireless Mobile Broadband

Mobile Broadband Infrastructure

•

INTELLIGENT TRANSPORT SYSTEM (ITS)

High Altitude Stratospheric Platform Services(HAPS)

Menambah Coverage dan Capacity

ENABLING TECHNOLOGIES

PROBLEMS OF WIRELESS CHANNEL

• Incoming signal consists of several paths with different time delays (multiple copies of the same signal)

Intersymbol Interference leads to very slow data rate

Signal Fluctuation leads to loss of SNR

FREQ. SPECTRUM LIMITATION

20

FDM vs. OFDM

• Conventional v/s Modern FDM technique

21

LTE-Downlink (OFDM)

• Improved spectral efficiency

• Reduce ISI effect by multipath

• Against frequency selective fading

22

LTE Uplink (SC-FDMA)

• SC-FDMA is a new single carrier multiple access technique which has similar structure and performance to OFDMA

A salient advantage of SC-FDMA over OFDM is low to Peak to Average Power Ratio (PAPR) :

Increasing battery life

23

Multi-antenna techniques

• Beam-steering using phase shifters at each radiating element

Radiatingelements

Powerdistribution

Phaseshifters

Equi-phasewave front

= [(2/)d sin]

3 2 0

d

Beam direction

Phased Array Antenna...

MSC

BSBS

WLL

LOS

MSC

BS

multiple antennas at MS

NLOS

MIMO techniques<=> different propagation environment

Urban area

Rural area

SDMA concept

- expected up to 8 times capacity improvement

- power classes concept (can be dynamic or static)

- with ref. signal BF MSs can be separated even when they have the same angular position to BS !

- for DoABF MSs angular distribution is important (macrocell) - network planning (frequency) is simpler, but larger cell size can require new planning, more smooth migration into existing network

- more network management upgrade required

PCH 1 PCH 1

PCH 1PCH 1

RESEARCH WIRELESS ACCESS NETWORKS

28

Power

Frequency

TimeCode

FDMA TDMA CDMA

DS-CDMA Concepts– Freq domain

transmitted symbol

spreading

Despreading by correct spreading sequence

Communication Channel

Spread symbol

User 1 User 1

User 2

User 3 Despreading

by wrong spreading sequence

No signal

auxiliary

Signal-to-interference ratio (SIR)

• Desired SIR will limit the capacity• Wrong code will not detect signal• Non CDMA signal received at the Rx will be reduced by spreading and filtering jammer suppression Other non-

CDMA user

User’s code

r(t -1)

c(t - )

Despreader Demodulator/Detector

D1

D2

D3

r(t -2

r(t -3)

Multipath fading is unavoidable in wireless communications

CDMA is wideband Frequency Selective channel

Intersymbol Interference (ISI) can be better resolved

GSM use equalizer at bit level processing

CDMA Rake chip level processing

The number of resolvable paths is much higher.

Better performance !!

Problem of Power Control - CDMA• The main problems of cellular is multipath

propagation :– Frequency selective channel due to

delay spread propagation.– Signal fluctuation due to mobility

• CDMA is a spread spectrum multiple access technique that uses large bandwidth (1.25 MHz for narrowband and 5 MHz for wideband CDMA).

• Coherence Bandwidth for typical multipath

channel is in the order of hundreeds KHz CDMA channelis always frequency selective.

• Need to solve for both problems.

(b) Multipath fading problem

2

Pt1

Pr1

Pr2

Pt2

d1 d2

Signal fluctuation

User

(a) Near-far distance problem

Delay spread

Multi Carrier Technique (to solve for frequency selective channel)

1,cf 2,cf 3,cf4cf , jcf ,..

)Hz(f

dB

uB

Carrier bandwidth Bu is divided into J subcarriers of bandwidth Bd so that Bd = Bu/J or Bu = JBd

By Choosing a large number of J, bandwidth of each sub carrier can be made lower than the channel coherence bandwidth to produce a frequency non selective channel .

Multiuser Detection Receiver

• Conventional receiver detects the signal using each user’s code individually.

• Multiuser detection /receiver (MUD) use all user’s signal to detect each user signal iteratively.

• In MUD, MAI is reduced for each iteration

r(t -)

c(t - )

Despreader Demodulator

c(t - )

Demodulator

Interference component will decrease by iteration

Other user interference is subtracted using feedback

Performance Of multi user Detection

0 1 2 3 4 5 6 7 810

-3

10-2

10-1

Bit

erro

r ra

te,

BE

R

Eb/Io (dB)

2 users 5 users 8 users 10 users

0 1 2 3 4 5 6 7 810

-3

10-2

10-1

100

Bit

erro

r ra

te,

BE

R

Eb/Io (dB)

2 users 5 users 8 users 10 users

MULTI USER DETECTION IMPROVES DETECTION PERFORMANCE SIGNIFICANTLY

Multi User DetectionSingle User Detection

Penutup/Diskusi

Teknik Multi-Carrier merupakan trend teknologi wireless access network yang bisa mengatasi Problem Kanal Wirelss dan Keterbatasan Frequensi

Teknik Multi User Detection bisa menghilangkan/mengurangi interferensi, sehingga meningkatkan kapasitas.

Kapasitas dan laju data Wireless Communication meningkat tajam dalam 10 tahun terakhir.