Mobile Communications : Present and the Future

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


3rd Generation Mobile

Communications


Vision


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


IMT2000 Radio Transmission Technologies

UMTS

OFDMA TDD

WMAN

WiMAX

OFDMA


What is CDMA ?What is CDMA ?


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


CDMA ReceiverCDMA Receiver


Code Division Multiple Access


Capacity and interference


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


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


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


UMTS Network Architecture


Simplified UMTS Architecture

Handles switching, routing calls and data connections to external networks


General UMTS Architecture


UE

RAB

End to end services

RNC

End-to-end servicesor Applications(i.e.Video gameInternet access)

MSC

UMTS network

External network

SGSN


Signal flow


UMTS Radio Network PlanningUMTS Radio Network Planning


“Spreadsheet” Analysis

Radio Network PlanningRadio Network Planning


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


•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


Data rate vs Coverage

IET Vodafone lecture


Capacity planning


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


Increased Sectorisation- Antenna patterns are not perfect and will result in increased interference

Impact on the capacity growth for network elements


UMTS Optimization


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”


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


Drive tests/Walk tests


Roaming and network sharing


Roaming


Network/Spectrum sharing


•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