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RISET DAN PERKEMBANGAN TEKNOLOGIWIRELESS ACCESS NETWORKS
Adit Kurniawan ([email protected])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
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.