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Mobile communications: present and future(Part I)Dr. Abhaya Sumanasena MSc PhD CEng MIET MIEEE Delivered 22 January 2009 @ SLINTEC
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Mobile communications:
present and future(Part I)
Dr. Abhaya Sumanasena MSc PhD CEng MIET MIEEE
22 January 2009
Dr. Abhaya Sumanasena
Dr. Abhaya Sumanasena PhD CEng MIEEE MIET
Dr. Abhaya Sumanasena is currently working as a Technical Policy Manager at Ofcom, the government regulator in UK. Prior to Ofocm, Abhaya has worked as a Principal Engineer in Ericsson, a global vendor, and in Hutchison 3UK, the first mobile operator dedicated to 3G services in the UK. During this period Abhaya has taken a leading role in designing, rolling out and optimization of 3G and the first HSDPA network in the UK. Before joining 3UK, Abhaya worked as a Researcher at Mitsubishi Electric research laboratory where he conducted research work for beyond 3G systems. During that period he also represented the company at IEEE standardisation meetings and European Union project consortiums.After obtaining his MSc in Radio & Communications Engineering at King's College London, Abhaya completed his Ph.D. in "Adaptive Physical layer for 3rd Generation Mobile Satellite Systems" from University of Surrey, Guildford. He has published 12 papers in international journals/major international conferences and obtained two patent rights. While pursuing his PhD, he won a special award for Research Excellence from Inmarsat. After his PhD, Abhaya has served as a Post Doctoral Research Fellow in CCSR, at University of Surrey. At a very early stage during his academic career Abhaya has been recognized for his design skills by winning "Junior Inventor of the year award" twice in Sri Lanka and the best award for Electronics design twice in India. Abhaya has evaluated number of IET and IEEE papers in the area of mobile communications. His industry knowledge and expertise crosses a broad range of technologies, including 3G, Satellite, HSDPA, WiMAX and DVB. Abhaya has been involved in IET committee activities for about 9 years. After serving as the Chairman of the IET Surrey, he joined Berkshire area local network where he currently serves as the vice chairman.
• Some basics of mobile communications
• Third generation (3G) mobile communication systems
• High speed data transmission (HSDPA) • Practical challenges: capacity, coverage and optimization of a mobile network • Future directions: long term evolution (LTE)
• Regulatory aspects
OverviewOverview
Dr. Abhaya Sumanasena
3rd Generation Mobile
Communications
Dr. Abhaya Sumanasena
Vision
Dr. Abhaya Sumanasena
Data rate (Mbps)
Spectrum Allocation WRC 92
1850 1900 1950 2000 2050 2100 2150 2200
1850 1900 1950 2000 2050 2100 2150 2200
NorthAmericaMSS
PCSReserve
EuropeUMTSGSM 1800 DECT MSS
1880 MHz 1980 MHz
JapanKorea (w/o PHS)MSSIMT 2000PHS MSSIMT 2000
2160 MHz1895 MHz
1918 MHz1885 MHz
ITU Allocations
1885 MHz 2025 MHz
IMT 2000
2010 MHz
2110 MHz 2170 MHz
China MSSIMT 2000IMT 2000
IMT 2000
MSSUMTS2170 MHz
MSS
1885 MHz 1980 MHz
AA D B E F C AA D B E F C
MDS
GSM 1800
1850 MHz WLL WLL
Identified the bands 1710 - 1885 and 2500 - 2690 MHz for IMT-2000
Dr. Abhaya Sumanasena
IMT2000 Radio Transmission Technologies
UMTS
OFDMA TDD
WMAN
WiMAX
OFDMA
Dr. Abhaya Sumanasena
What is CDMA ?What is CDMA ?
Dr. Abhaya Sumanasena
Multiple Access SchemesMultiple Access Schemes
How does CDMA work ? How does CDMA work ?
• Higher rate-of transition, causes spectral spreading • Higher spreading factor gives higher processing gain
Dr. Abhaya Sumanasena
CDMA ReceiverCDMA Receiver
Dr. Abhaya Sumanasena
Code Division Multiple Access
Dr. Abhaya Sumanasena
Capacity and interference
Dr. Abhaya Sumanasena
Situation is more complex when neighbour cells contribute to interferenceHence reduce the capacity
Cell Breathing & soft capacity
Low traffic load
Cell edge C/I > required C/I for the service
Loaded network
C
IDr. Abhaya Sumanasena
“Near far problem”
Close mobile will cause interference to distant mobile
Dr. Abhaya Sumanasena
Transmit Power control (TPC)
Solution to “near far problem”
Open-Loop•MS adjusts Tx level based on Received
signal.•Reacts to Shadow signal variations
(fading)•Slow Response time.
Closed-Loop•MS adjusts Tx level based on received control commands.•BS commands MS for adjustments based on Rx SNR.•Control frequency = 1500 Hz
Dr. Abhaya Sumanasena
Node B1 Node B2
Macrodiversity
Seamless Coverage
Size of overlap area
On average 30-40% of users are expected to be in soft handover mode
Soft Handover
Dr. Abhaya Sumanasena
UMTS Network Architecture
Dr. Abhaya Sumanasena
Simplified UMTS Architecture
Handles switching, routing calls and data connections to external networks
Dr. Abhaya Sumanasena
General UMTS Architecture
Dr. Abhaya Sumanasena
UE
RAB
End to end services
RNC
End-to-end servicesor Applications(i.e.Video gameInternet access)
MSC
UMTS network
External network
SGSN
Dr. Abhaya Sumanasena
Signal flow
Dr. Abhaya Sumanasena
UMTS Radio Network PlanningUMTS Radio Network Planning
Dr. Abhaya Sumanasena
“Spreadsheet” Analysis
Radio Network PlanningRadio Network Planning
Dr. Abhaya Sumanasena
Coverage • The only way to get more coverage is to:
- Transmit more power - Transmit data slower - Use bigger/higher antennas
- Use a lower frequency- Use somebody else’s network
Dr. Abhaya Sumanasena
•Uplink transmit power likely to be the limiting factor in range
• Downlink transmit power and peak data rate determine downlink range.
Peak data rate then needs to be shared between users.
Terminal vs Coverage
IET Vodafone lecture
Dr. Abhaya Sumanasena
Data rate vs Coverage
IET Vodafone lecture
Dr. Abhaya Sumanasena
Capacity planning
Dr. Abhaya Sumanasena
Use of enhanced technologies-Transmit diversity: Fairly easy- Intelligent antenna: Technology not mature enough- Multiuser Detectors: Technology not mature enough
Solutions to for capacity growth
Reduced cell radius- Increased number of sites / equipment hence increased infrastructure cost
Use of additional carrier- Increased number of sites / equipment hence increased infrastructure cost
Dr. Abhaya Sumanasena
Increased Sectorisation- Antenna patterns are not perfect and will result in increased interference
Impact on the capacity growth for network elements
Dr. Abhaya Sumanasena
UMTS Optimization
Dr. Abhaya Sumanasena
Some Optimisation parameters
Cell availability
Call blocking probability
Call drop rate
Call completion success rate
Throughput at the edge of the cell (packet and voice calls)
End-to-end packet delay transfers
Cell search time
Call set up time
handover success rate
Measures from KPIs
What does operator mean by “quality”
Dr. Abhaya Sumanasena
C/I Plots Before and After Optimisation
Non optimised antenna tiltsPoor C/I
Downtilts of up to 6°Improved C/I
Un-optimised Optimised
C/I > 12 dB
C/I < 12 dB
C/I < 9 dB
C/I < 6 dB
C/I < 3 dB
C/I <-6 dB
C/I <-3 dB
C/I < 0 dB
Dr. Abhaya Sumanasena
Drive tests/Walk tests
Dr. Abhaya Sumanasena
Roaming and network sharing
Dr. Abhaya Sumanasena
Roaming
Dr. Abhaya Sumanasena
Network/Spectrum sharing
Dr. Abhaya Sumanasena
•RAN and backhaul cost about 50 % from the budget•Site sharing can provide 30% cost saving for an operator [PA consulting group, LTE World Summit, Berlin, 2008]
•Trunking gain
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