UMTS Radio Access Network Planning
School of Engineering Design & Technology 1
Universal Mobile Telecommunication System
Radio Access Network Planning
Uday Raktale
Project Report submitted in partial fulfillment of the requirements for the
Degree of Masters by advanced study in Personal, Mobile and Satellite Communication.
Supervisor: Professor Y. F. Hu
School of Engineering Design & Technology
University of Bradford
23th May 2005
UMTS Radio Access Network Planning
School of Engineering Design & Technology 2
ABSTRACT Today telecommunication is one of the fastest growing sectors of the world economy. One in
every six people owns a cellular/mobile phone operating on cellular radio technology, one of the
most successful mobile communication system adapted worldwide. We are presently on Second
Generation of wireless communication (2.5G) and at the verge of moving towards third
generation (3G) i.e. Universal Mobile Telecommunication System (UMTS), which is based on
Wideband Coded Division Multiple Access (WCDMA) technology as its access scheme.
By 2006, some 2 billion people will be using mobile phones and devices, in many cases to
access advanced data services. Against this backdrop, the need for efficient and effective
network design will be critical to the success of increasingly complex mobile networks.
Network Planning of a UMTS network poses a much greater challenge then planning a non
CDMA Network as the relationship between coverage and capacity differs from that of a 2.5G
system. One of the basic differences between 3G and previous systems is that there will be
different services, requiring the power level received at the base station from a given subscriber
to be dependent on the service in use at the time. This in turn will create a situation in which the
‘coverage map’ will also depend on the service in use.
The project report encompasses the concept of radio network planning for UMTS networks
and addresses the various issues concerning capacity, coverage, quality of service and
interference. The report concludes the key parameters of Radio network desigining and the
methodes to design a 3G state of art network by establishing a balance between the parameters,
followed by suggested future work.
Key Words: UMTS, WCDMA, URTAN, Link Budget
UMTS Radio Access Network Planning
School of Engineering Design & Technology 3
ACKNOWLEDGEMENT Ruskin says, “Many men fail to achieve success not through insufficiency of means or
impatience of labor but because of confused ideas of the things to be done” and as a matter of
fact it is through Professor Yim Fun Hu’s constructive suggestions which helped me in dragging
out the very route of the confused ideas and thus the project has been brought to a competitive
form. I am grateful to Professor Yim Fun Hu for her kind guidance throughout the project.
I would like to thank Dr. R.A.A. Alhameed, Research Head, for his guidance and moral
support, which helped me, focus on my project.
I would like to thank my parents and my friend Sudhir Aggarwal, in special, for their support
and pushing me to complete my project quickly. I would also like to thank all my friends and
colleagues who believed in me and supported me throughout, giving me the confidence whilst I
was working on my project.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 4
TABLE OF CONTENTS
ABSTRACT……………………………………………………………………………..….……..i
ACKNOWLEDGEMENT………..………………………………………………………….……ii
1 INTRODUCTION..……..………………………………………………….………………….1
2 UNIVERSL MOBILE TELECOMMUNICATIONS SYSTEM- UMTS ……………….....…2
2.1 Radio Access Network Overview……………………………………………….….….3
2.1.1 UTRAN Network Elements..………….………………………………………3
2.2 WCDMA (Wideband Direct-Sequence Code Division Multiple Access) .……………8
2.3 Frequency Bands in WCDMA ………….……………………………………………..9
2.3.1 UTRAN Modes .……………………………….………………….…………..9
3 CELLULAR CONCEPT ……..……………………………………………………………...10
4 RADIO NETWORK PLANNING PROCESS ………….…………………..……………….12
4.1 Planning Process Overview ………………….………………………………….12
4.1.1 Radio Network Design Requirements ………………………………………13
4.1.2 Model Tuning..…..…………………………………………………………...15
4.1.3 Nominal Cell Planning……………………………………………………….15
4.2 CCQ Model (Coverage, Capacity and Quality of Service Model)…………………...16
4.3 Basic Traffic Dimensioning Input……..…………………………………………..…18
4.3.1. Traffic Classes…………………………..………………………………..….18
4.3.2 Input Analysis…………………………………………………………..……19
4.3.3 Determining the Average User Profile..……..………………………………21
4.4 Basic Traffic Dimensioning………………………………………………………….22
UMTS Radio Access Network Planning
School of Engineering Design & Technology 5
5 COVERAGE AND CAPACITY DIMENSIONING……………………………..…………..25
5.1 Capacity……………………………………………………………………..………..25
5.1.1 Effects of Loading………………………………………………………..…..27
5.1.2 Effects of Sectorization………………………………………………………29
6 LINK BUDGET OVERVIEW………………………………………………………………..30
6.1 WCDMA Technology Review ………………………………………………………32
6.2 Link Budget ………………………………………………………………………….33
6.3 Uplink Dimensioning………………………………………………………………....36
6.3.1 Uplink Capacity……………………………………………………………...36
6.3.2 Uplink Coverage……………………………………………………………..38
6.3.3 Uplink budget ...……………………………………………………………...38
6.4 Cell size……………………………………………………………………………...41
6.5 Downlink Dimensioning…………………………………………………………….43
6.5.1 Downlink Curves………………………………………………………….....43
6.5.2 Downlink Link Budget………………………………………………………44
6.6 Link Budget Margins…………………………………………………………..…...47
6.6.1 Log –Normal Fading…………………………………………………………47
6.6.2 Handover gain………………………………………………………………..48
6.6.3 Power Control Margin………………………………………………………..48
6.6.4 Slant Loss…………………………………………………………………….49
6.6.5 Body Loss.……………………………………………………………………49
6.6.6 Car Penetration Loss…………………………………………………………50
6.6.7 Indoor Margins……………………………………………………………….50
6.6.8 Interference Margin ....……...………………………………………………..51
UMTS Radio Access Network Planning
School of Engineering Design & Technology 6
7 LINK BUDGET –Examples………………………………………………………………….52
7.1 Maximum allowed Path Loss for – 12.2 kbps ...………..………………………….52
7.2 Maximum allowed Path Loss for – 144 kbps……………………….……………...53
7.3 Maximum allowed Path Loss for – 384 kbps ….……………………….…………...54
7.4 Cell Size Calculation………………………………………………………………..55
7.5 Calculation of number of sites required in a region ………………………………..56
8 EXPANDING CAPACITY BY CONFIGURATION MODIFICATION………………...…57
8.1 Adding new frequency carriers……………………………………………...………57
8.2 Increase number of sectors………………………………………..…………………57
8.3 Using repeater solutions…………………………………………….…………….…58
8.4 Adding distributed antennas………………………...……………………………….58
8.5 Sites Addition…………………………………………………….………….………58
8.6 Cell split…………………………………………………………….……….………59
8.7 Layered Network…………………………………………………………………….59
9 PRODUCT EVOLUTION………………………………………………….………………...60
9.1 Adaptive Antenna.………………………………………………….……………….60
9.2 Interference Cancellation.....……………………………………….….…………….60
9.3 Transmit Diversity.……………………………………………….….…………..….60
10 CONCLUSION & FUTURE WORK……………………………………………….………61
REFERENCES.………………………………………………………….……………………….63
GLOSSARY..…..……………………………………………………….…………….………….67
UMTS Radio Access Network Planning
School of Engineering Design & Technology 7
Table of Figures
Figure 2.1 UMTS Network Architecture ……………………………………………………..…2
Figure 2.2 Radio network overview…..…………………………………………………….…....3
Figure 2.3 Node B block diagram….…………………………………………………………….4
Figure 2.4 OTSR (Omni Transmit Sector Receiver) Node B…………..……………….……….6
Figure 2.5 STSR (Sectorial Transmit Sector Receive) Node B ..………………………..………6
Figure 2.6 V800 3G handset..………………..…………………………………………………..7
Figure 3.1 Mobile Telephone System Using a Cellular Architecture…………………………..10
Figure 3.2 Cell Distribution in a Network……………………………………………………...11
Figure 4.1 CCQ (Capacity, coverage &Quality of Service) model ……………..……….…….16
Figure 4.2 Erlang-B blocking probability..……………………………………………….….....22
Figure 4.3 Example of multi-rate blocking probability calculations (%)………..………..……23
Figure 4.4 Channel utilization example…..………………………………………………..…...24
Figure 5.1 SNR (Signal to noise) experienced by a user ..……………..…………………..…..26
Figure 5.2 Interference introduced by users in the neighboring cell. ……………....…..……....28
Figure 5.3 Loading factor as perceived by cell………………………………………..…..……28
Figure 6.1 Link Budget Process flow block diagram ..………………………………………....30
Figure 6.2 Link Budget Flow Chart..……..…………………………………………….……....31
Figure 6-3 Schematics of components included in the link budget….……………………….….39
Figure 6.4 Example of capacity versus cell range in an urban environment…..………….……43
Figure 6.5 Lognormal fading margins. Handover gain is included in these curves. …………...48
Figure 7.1 Cell coverage comparision….……………………………………………………….63
UMTS Radio Access Network Planning
School of Engineering Design & Technology 8
List of Tables
Table 2.1 Frequency Band in WCDMA …………..……………………………….……………9
Table 4.1 Cell type classification……………………………………………..…...……..……..13
Table 4.2 Area type classification …………..……………………………………………….…13
Table 4.3 Examples of input data………………………………………………….…..…….….19
Table 4.4 Example of mapping of services to Radio Access Bearers..……………….…….…..20
Table 4.5 Example of an average user profile………………………………………….…...…..21
Table 6.1 Uplink values of Eb/I0..……..……………………………………………….………..37
Table 6.2 Uplink values of Mpole ….…………..………………………………………..………37
Table 6.3 Uplink link budget for voice 12.2 kbps and 95% probability of coverage….…….…42
Table 6.4 Downlink values of Mpole (three-sector site) ………..……………………..…….…..44
Table 6.5 Typical values of building penetration loss ….………………………………..…….50
Table 7.1 Link budget example 12.2 kbps voice ....…...……………………………..…………52
Table 7.2 Link budget example 144 kbps …………..………………………………………….53
Table 7.3 Link budget example 384 kbps …………...…………………………………………54
UMTS Radio Access Network Planning
School of Engineering Design & Technology 9
1. INTRODUCTION
After the explosion in the mobile telecommunication back in the late 1990s with second
generation (2G) networks springing up all over the world, the race was on for the next generation
of wireless communication. The Universal Mobile Telephony System (UMTS), or 3G as it is
known, is the next big thing in the world of mobile telecommunications. It provides convergence
between mobile telephony broadband access and Internet Protocol (IP) backbones [1].
The success of the technology lies in optimum utilisation of resources by efficient planning of
the network for maximum coverage, capacity and quality of service. The report aims to detail
method of UMTS Radio Network (UTRAN) Planning.
The new technologies and services have brought vast changes within the network planning; the
planning of a 3G network is now a complex balancing act between all the variables in order to
achieve the optimal coverage, capacity and Quality of Service simultaneously.
The layout of this report is as follows. In Section 1 we shall talk about the telecommunication
in general followed by section 2 which provides an understanding of UMTS technology, then in
section 3 we shall talk about the Cellular Network Principal followed by section 4 detailing
Network planning process and various parameters to be considered. Section 5 encompasses
coverage and capacity dimensioning, section 6 gives a comprehensive review of WCDMA
technology and Link budget calculation, followed by examples in section 7. Section 8 comprises
of various metholodology for capacity expansion followed by section 9 giving a brief description
on the product evolution. Section 10 presents an overall summary and conclusions from the
project work, suggestions for further work are also included.
In present telecommunication scenario, it is a must for a telecommunication engineer to have
good understanding of cellular network. Keeping in view the topic of the report was chosen. It
provides a clear understanding of basic fundamentals of 3G cellular network designing, and
describes a method of designing a modern 3G Radio Access Network.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 10
2. UNIVERSL MOBILE TELECOMMUNICATIONS SYSTEM- UMTS
Figure 2.1. UMTS Network Architecture [2]
Qualcomm developed the world's first commercially available, fully integrated WCDMA
network, also known as UMTS [3]. The UMTS network architecture is depicted in figure 2.1.
The core network (CN) handles call control and mobility management functionalities, while the
UTRAN (UMTS terrestrial radio access network) manages the radio packet transmission and
resource management. CN consists of two domains Circuit Switched (CS) and Packet Switched
(PS). CS handles the real time traffic & PS handles the other traffic. CS connects to other
communication network (e.g PSTN & PLMN) and PS connects to IP backbone. The major
elements of CN are MSC/VLR, HLR, GMSC and SGSN, GGSN on PS side [2].
In the core network logical network nodes GGSN (Gateway GPRS [General Packet Radio
System] Support Node) and SGSN (Serving GPRS Support Node) support packet routing and
transfer. The GGSN is basically a packet router and acts as a physical interface to the external
packet data networks. The SGSN handles packet delivery to and from mobile terminals. GGSN
and SGSN are capable of supporting terminal data rates up to 2 Mbps. [4]
A UTRAN consists of one or more RNSs (radio network subsystems), which in turn consist of
base stations (Node Bs) and RNCs (radio network controllers). The RNS performs all of the
radio resource and air interface management functionalities. [4]
Node B
Node B
Node B
RNC
Node B
Node B
Node B
RNC
MSC
SGSN
GMSC
GGSN
AuC
VLR
EIR
PSTN, PLMN
PSPDN
RAN CN
UE
UE
lub
lub
Uu
Uu
luCS
luCS
luPS
luPS
HLR
CS
PS
UMTS Radio Access Network Planning
School of Engineering Design & Technology 11
2.1 Radio Access Network Overview
Figure 2-2 Radio network overview [5]
The figure 2.2 depicts various network elements and the interface. The RNC manages Radio
Access Bearers (RABs) for user data, the radio network and mobility. The RBS provides the
radio resources.
The key external interfaces are the Iu interface between RNC and core network and the Uu
between User Equipment (UE) and NodeB, RBS. Within the RAN, the RNCs communicates
with each other over Iur and with RBSs over Iub See Figure 2.2.
2.1.1 UTRAN Network Elements
• RNC (Radio Network Controller)
• Node B (Radio Base Station)
• UE (User Equipment, Mobile terminal)
2.1.1.1 RNC (Radio Network Controller) Radio Network Controller is responsible for RRC (Radio Resource Control), RRM, QoS, Call
Admission Control, Channel Allocation, Power Control Settings, Handover Control, Ciphering,
Broadcast Signalling, Open Loop Power Control. Some of them are described in brief under this
section. [6]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 12
• RRC (Radio Resource Control)
1 Management of radio resources (establishment, release and termination of connection)
2 Management of RRC connection between the UE and network (establishment, release)
• RRM (Radio Resource Management)
1 The RRM is the most critical resource in wireless systems.
2 It is in charge of allocating and managing radio resources in the most effective way.
• QoS (Quality of Service)
1 High QoS (ensuring subscribers satisfaction)
2 High spectrum efficiency (maximum operator revenue)
3 Easy (re) configuration (lowering operational cost)
2.1.1.2 Node B
Node B functions as a RBS (Radio Base Station) and provides radio coverage to a
geographical area, by providing physical radio link between the UE (User Equipment) and the
network. Along with the transmission and reception of data across the radio interface the Node B
also applies the codes that are necessary to describe channels in a WCDMA system. [7]
It contains the RF transceiver, combiner, network interface and system controller, timing card,
channel card and backplane. A typical Node B is shown in figure 2.3 below.
Figure 2.3 Node B block diagram. [8]
RF Modules (DDMs, Pas, Tx Splitters)
RF Feeders
Interconnect Module
Digital Shelf
CCM CEMs GPSAM TRM(s)
GPS Receiver (Optional)
Functions : •Tx amplification •Coupling
External Alarms
RNC lub
Functions: •Network Interface •Call processing •Signal Processing •Frequency up/down conversion
Power Supply - 48 V DC nominal
UMTS Mark – II BTS
Sector à Sector ß Sector ý
UMTS Radio Access Network Planning
School of Engineering Design & Technology 13
• The Functions of Node B are: [6]
• Air interface Transmission /Reception
• Modulation /Demodulation
• CDMA Physical Channel coding
• Micro Diversity
• Error Handing
• Closed loop power control
Depending on sectoring (omni/sector cells), one or more cells may be served by a Node B. A
Single node B can support both FDD and TDD modes, and it can be co-located with a GSM BTS
to reduce implementation costs. Nmode B connects with the UE via the WCDMA Uu radio
interface and with the RNC via the lub asynchronous transfer mode (ATM) – based interface.[9]
The main task of the Node B is the conversion of data to and from the Uu radio interface,
including Forward Error Correction (FEC) , rate adaption , WCDMA spreading /dispreading ,
and quadrature phase shift keying (QPSK) modularion on the air interface. It measures quality
and strength of the connection and determines the Frame Error Rate (FER), transmitting these
data to the RNC as a measurement report for handover and macro diversity combining . The
Node B is also responsible for the FDD softer hadover. This micro diversity combining is carried
out independently , eliminating the need for additional transmission capacity in the lub. [9]
The Node B also participates in power control, as it enables the UE to adjust its power using
downlink (DL) Transmission Power Control(TPC) commands via the inner –loop power control
on the basis of uplink (UL) TPC information. The predefined values for inner –loop power
control are derived from the RNC via outer –loop power control. [9]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 14
On the baisis of coverage, capacity and antenna arrangement node B can be catageorises as
Omnidirectional and Sectorial. Later can further be categorised as OTSR (Omni Transmitter
Sector Receiver) and STSR (Sector Transmitter Sector Receiver).
Figure 2.4 OTSR (Omni Transmit Sector Receiver) Node B. [10] The OTSR configuration uses a single (PA)Power Amplifier (figure2.4), whose output is fed
to a transmit splitter. The power of the RF signal is divided by three and fed to the duplexers of
the three sectors, which are connected to sectorized antennas. [10]
Figure 2.5 STSR (Sectorial Transmit Sector Receive) Node B. [10]
The STSR configuration uses three (PA) Power Amplifier (figure 2.5), whose output is fed
directly to the duplexers of the three sectors, which are connected to sectorized antennas.
Transmit path : 3 cells, 3 antennas
1 Watt
1 Watt
1 Watt
Transmit path : 1 cell, 3 antennas DDM – Dual Duplexer module (for Main and Diversity)
Receive path : continuous softer handover
TRM
Tx Splitter
PA
DDM DDM DDM
DDM DDM DDM
PA PA PA
Receive path : Possible softer handover
TRM
UMTS Radio Access Network Planning
School of Engineering Design & Technology 15
• OTSR vs STSR
OTSR uses only one PA, so compared to an STSR configuration, two power amplifiers are
saved, with the associated cost savings, which means the OTSR configuration is up to 30%
cheaper than the STSR configuration hence at the initial phase of network deployment** OTSR
is preffered over STSR. When the traffic demands grow and thus the interference created by the
users, there may be a need to provide more capacity, upgrading to STSR, which multiplies
between 2.4 and 3.3 times the capacity. This can be done simply by adding two more power
amplifiers, and removing the transmit splitters from the OTSR configuration. The cell planning
does not need to be changed and no site alterations of antenna, cabling, or other hardware is
necessary. [10]
This “pay as you grow” method is consequently a good use of resources, both in terms of
initial expenditure and engineering Opex. So by starting with an OTSR configuration an operator
may in fact end up spending less money in the long term than it would with an STSR
configuration that might never be used to its full potential. [10]
2.1.1.3 User Equipment
The radio terminal that a subscriber uses to receive service from the UTRAN is
known as the UE. The UMTS Subscriber or UE (User Equipment) is a combination
of ME (Mobile Equipment) and SIM /USIM (Subscriber Identity Module / UMTS
Subscriber Identity Module).[7]
It is in the form of PDA terminals or a handset similar to GSM mobiles. The UE
supports multimode GSM, GPRS and UMTS services and support multi-band
GSM900, DCS1800 and PCS1900 systems. Figure 2.6 shows the best 3G handset of
year 2004 manufactured by Sony Ericsson. [9]
Figure 2.6. V800 3G handset
** For UMTS, O2 has chosen OTSR for the launch of their networks in Germany and UK.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 16
2.2. WCDMA (Wideband Direct-Sequence Code Division Multiple Access)
In UMTS access scheme is DS-CDMA (The name “direct sequence CDMA” means that a
code sequence is directly used to modulate the transmitted radio signal) with information spread
over approximately 5 MHz bandwidth.[11].
Each information bit is coded with a pseudo random sequence or code. Each information bit is
thus represented by a sequence of “chips”. This gives a considerable bandwidth expansion, as the
chip rate is much higher than the information rate. The number of chips per data symbol is called
the Spreading Factor (SF). In WCDMA the basic chip rate is set to 3.84 Mcps which leads to a
carrier spacing of around 5 MHz. [11]
In WCDMA all users share the same band. Their signals are spectrally much wider than the
information data rate. The reason for that is the use of a spreading sequence of much higher data
(chip rate) than the information data rate. Ideally the sequences of different users do not interfere
with each other because they are mutually orthogonal. Thus taking advantage of this property,
though the correlation of the received signal generated by many users with the spreading
sequence uniquely assigned to a particular user, we extract the interesting signal, zeroing the
remaining signals due to the orthogonality of applied spreading sequences.[12].
Every user is assigned a separate code/s depending upon the transaction, thus separation is not
based on frequency or time but on the basis of codes. The major advantage of using WCDMA is
that there is no plan for frequency re-use [13]. (WCDMA technology is explained in detail in
section 6.1).
WCDMA is intended for wideband multimedia services and support for bit-rates of at-least 384
kbit/s with good coverage and full mobility. Up to 2 Mb/s can be supported with one 5 MHz
carrier with local coverage.[14]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 17
2.3 Frequency Bands in WCDMA The air interface transmission direction are separated at different frequencies with a duplex
distance of 190 MHz (Table 2.3.1) the uplink frequency band is 1920-1980MHz and the
downlink is 2110-2170 MHz. 5 MHZ bandwidth is currently being used in network
development.[2].
Table 2.1 Frequency Band in WCDMA [15]
* The center frequency must be an integer multiple of 200 kHz.
** The TDD mode is viewed to be a complement to WCDMA to boost the capacity.
In WCDMA networks there is no frequency planning, because all cells use the same frequency.
A typical WCDMA operator may be given, for example 35 MHZ slice, which is enough for 7*5
MHz WCDMA frequency channels.
2.3.1 UTRAN Modes
• FDD (Frequency Division Duplex): A duplex method whereby uplink and downlink
transmissions use two separated radio frequencies. In the FDD, each uplink and downlink
uses the different frequency band. [16]
• TDD (Time Division Duplex): A duplex method whereby uplink and downlink
transmissions are carried over same radio frequency by using synchronized time
intervals. In the TDD, time slots in a physical channel are divided into transmission and
reception part. Information on uplink and downlink are transmitted reciprocally. [16]
MODE UP-LINK DOWN-LINK NOMINAL CHANNEL CHANNELWCDMA MHz MHz SPACING RASTER
FDD 1920-1980 2110-2170 5MHz 200kHz*
1900-1920 1900-19202010-2025 2010-2025
5 MHz 200kHzTDD**
UMTS Radio Access Network Planning
School of Engineering Design & Technology 18
3. CELLULAR CONCEPT The UMTS network is third generation of cellular radio network which operate on the principle
of dividing the coverage area into zones or cells (node B in this case), each of which has its own
set of resources or transceivers (transmitters /receivers) to provide communication channels,
which can be accessed by the users of the network [17].
A cellular mobile communications system uses a large number of low-power wireless
transmitters to create cells as shown in figure 3.1. Variable power levels allow cells to be sized
according to the subscriber density and demand within a particular region. As mobile users travel
from cell to cell, their conversations are handed off between cells to maintain seamless service.
Cells can be added to accommodate growth. [18]
Communication in a cellular network is full duplex, which is attained by sending and receiving
messages on two different frequencies. The cellular topology of the network enables frequency
re-use (cells at a certain distance apart can reuse the same frequencies), which ensures the
efficient usage of limited radio resources.[2]
Figure 3.1 Mobile Telephone System Using a Cellular Architecture [17]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 19
In order to increase the frequency reuse capability to promote spectrum efficiency of a
system, it is desirable to reuse the same channel set in two cells which are close to each other as
possible, however this increases the probability of co-channel interference .[19]
The performance of cellular mobile radio is affected by co channel interference (due to the
interference caused by the other radio users). Co-channel interference, when not minimized,
decreases the ratio of carrier to interference powers (C/I) at the periphery of cells, causing
diminished system capacity, more frequent handoffs, and dropped calls.
Usually cells are represented by a hexagonal cell structure (Figure. 3.2), to demonstrate the
concept, however, in practice the shape of cell is determined by the local topography [17].
Figure 3.2 Cell Distribution in a Network [20]
Fading is another major constraint in wireless communication. All signals regardless of the
medium used, lose strength this is known as attenuation/fading. There are three types of fading
• Pathloss : Occours as the power of the signal steadily decreases over distance from the
transmitter.
• Shadowing : or Log normal Fading is causes by the presence of building , hills or even
tree foilage.
• Rayleigh Fading : or multipath fading is a sudden decrease in signal strength as a result
of interference between direct and reflected signal reaching the mobile station. [8]
Highway Town Suburb
Rural
UMTS Radio Access Network Planning
School of Engineering Design & Technology 20
4. RADIO NETWORK PLANNING PROCESS The aim of Network Planning is to provide a cost effective solution for the radio network in
terms of coverage, capacity and quality of service. The network planning process and design
criteria vary from region to region depending upon the dominating factor, could be capacity or
coverage [2].
4.1. Planning Process Overview In the following figure, the workflow of the planning process is illustrated
1. Definition of the Requirements: At the beginning, it is necessary to define the
performance requirements of the WCDMA network to be implemented.
2. Radio Propagation Model tuning Activity: In order to obtain more reliable radio
propagation predictions, it is suitable to tune the models implemented in WCDMA
planner for the most important and critical areas to be covered.
3. Nominal Cell Planning: The requirements, defined in the first phase, are the input to
dimensioning of the network in terms of nominal number of sites, using dimensioning
and/or design tools.
4. Site Search and Survey: The cell planner, with the support of the site hunters, finds the
most appropriate sites to achieve the radio coverage, according to the general criteria.
5. Radio Network Design: Different network design aspects are analyzed, in particular
-downlink common channel power allocation
-frequency planning in the case of cells with more than one carrier for capacity
requirement
-code planning
-parameters involved in the handover algorithms
6. Initial Tuning: The default setting of the cell data parameters and the site configuration
are optimized using measurements in the field.
DEFINITION OF THE REQUIREMENTS
RADIO PROPAGATION MODEL TUNING ACTIVITY
NOMINAL CELL PLANNING
SITE SEARCH AND SURVEY
RADIO NETWORK DESIGN
INITIAL TUNING
UMTS Radio Access Network Planning
School of Engineering Design & Technology 21
The work flow of the planning process is described in brief in the following part of this chapter.
The table 4.1 provides the typical cell range for various types and can be considered for use,
based on the coverage and capacity requirement. [8]
Table 4.1 Cell type classification [21] 4.1.1. Radio Network Design Requirements The radio network design requirements are related to coverage, capacity and services and they
are specified for each area type: dense urban, urban, suburban and rural (see Table 4.2 ).
Table 4.2 Area type classification [8]
C ell typ e T yp ica l ce ll ra d iu s T y p ica l p osition o f b ase sta tio n an ten n a
M acro C ell .. . .(L arge ce ll)
1 k m to 30 k mO utdo o r , m o unted abo u ve m ed iu m ro o fto pleve l heights o f a ll su rro u nd ing bu ild ing s arebelo w bare sta t io n an tenna height .
S m all m acro - ce ll 0 .5 km to 3 k mO utdo o r , m o unted abo u ve m ed iu m ro o fto pleve l heights o f a ll su rro u nd ing bu ild ing s arebelo w bare sta t io n an tenna height .
M icro ce ll U p to 1 k m O utdo o r , m o u nted abo uve m ed iu m ro o fto p
P ico -cell/indo o r U p to 5 00 mIndo o r o r o u tdo o r (m o unted be lo w m ed iumro o f - to p level)
DENSE
Areas within the urban perimeter. This includers densely developed areas wherebuilt up features do not appear distinct from each other. The typical street is notparallel.
URBANThe average building height is below 40 m. the average building density is >35%.
Built up areas with buildings blocks, where features do appear more distinct fromeach other in comparision to Dense Urban. The street pattern could be parallel ornot.The Average building height is below 40 m. the average building density is from 8%to 35%.Suburban density typically involves laid out street patterns in which streets arevisible. Building blocks may be as small as 30 by 30 m, but are typically larger andinclude vegetation cover. Individual houses are frequently visible.The Average building height is below 20 m. the average building density is from 3%to 8%.
Small and scattered built up areas in the outskirts of larger built up environments.
The Average building height is below 20 m. the average building density is <3%.RURAL
URBAN
SUBURBAN
UMTS Radio Access Network Planning
School of Engineering Design & Technology 22
4.1.1.1. Coverage Requirements
• For each area, the extension in km2 of coverage area is defined. The value of required
coverage area may increase through several phases in the evolution of the network.
• The coverage priority is normally identified according to land usage, population
distribution and/or vehicular distribution. The high traffic areas (the highest priority
coverage) where a continuous coverage has to be guaranteed, are, for example, highways
or roads with high vehicular traffic, business areas and other hot spots like Airport, train
station, Interchange etc. [8]
4.1.1.2. Capacity Requirements
• For each area, the number of subscribers and their “profile” (business, conventional, data
or/and speech user) is defined. This value can be obtained considering census data. An
annual subscriber forecast is required in order to plan the network growth.
• The traffic volume per subscriber and service type is determined on average during the
busy hour. Typically, this amount is given in Erlang for speech service and in kbyte/h for
data services. [8]
4.1.1.3. Service Requirements
• The types of service offered must be given for each area, the estimated usage of each
service should also be given. The services are characterized by the QoS (Quality of
Service) parameter related to different radio access bearer attributes. The main attributes
to define a service are, Bit Error Rate (BER) and Block Error Rate (BLER).
• The areas with different coverage reliability should be distinguished to determine which
service could be guaranteed. [8]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 23
4.1.2. Model Tuning In the cell planning process, the WCDMA planner tool is used to predict the radio coverage by
means of propagation models, for a particular site configuration.
Different propagation models are considered according to the different environments and site
configurations. The Okumura-Hata model, is recommended for macrocell configuration, in
urban, suburban and rural environments. [22]
The model tuning (model calibration) is performed in order to obtain more reliable radio
propagation predictions. Measured and predicted signal strength samples are compared, and the
mean error between them minimized.
4.1.3. Nominal Cell Planning A nominal cell plan shows the mast sites of the base stations, the coverage of each antenna and
the distribution of frequencies among the cells. These factors and others are based on the forecast
of traffic demand. The nominal cell plan often takes the form of a hexagonal pattern.[23]
While preparing the nominal cell plan, not only current traffic demand but also the possibility of
future traffic growth and cell splitting is considered and accordingly, mast sites are planned to
permit use in future network configurations.[23]
The scope of a nominal cell planning activity depends usually on requirements according to the
particular phase of the network planning process e.g. license application or radio network design.
In the case of a license application activity, the site count needed to achieve the required
coverage/capacity. [24]
Radio network design is an activity based on predictions by the design tool and knowledge of the
actual local environment. The result of this activity is a complete radio network plan with a
realistic number of sites and RBS (Radio Base Station/ Node B) configurations.[24]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 24
4.2. CCQ Model (Coverage, Capacity and Quality of Service Model) Designing a UMTS network is a multi-dimensional process due to the large number of
different design requirements and system parameters. In addition, when the number of users
increases, the interference in the coverage area also increases, thus causing the cell size to shrink.
Thus 3G planning is a complex and challenging task. The three factors affecting the 3G network
performance are coverage, capacity and Quality of Service, Figure 4.1 shows the CCQ model.
This is the basis of quality 3G planning [1].
Figure 4.1 CCQ (Capacity, coverage &Quality of Service) model [A]
Firstly, it is necessary to estimate the number of cell sites, the type of base stations and their
configurations (including the number of network elements, and antenna configurations). In order
to attain the number of cell sites and their configurations we need to assess the coverage capacity
and Quality of Service (QoS) requirements together with the type of area to be covered, such as a
dense urban area. With this information available it will be possible to start the dimensioning,
coverage and capacity planning [1].
Optimisation
Capacity
Quality of Service
Coverage
Infrastruct
Number of Users
UMTS Radio Access Network Planning
School of Engineering Design & Technology 25
The radio network planning starts with collection of the input parameters such as the network
requirements of capacity, coverage and quality.
The definition of coverage would include defining the coverage area ( e.g. 1000 km2), service
probability (e.g. 75 % voice, 25 % data subscribers etc), related signal strength (e.g. 106 db for
voice, 90dBm for data) etc.
The definition of capacity would include subscriber and traffic profile in the region of whole
area, availability of frequency band e.g. (35MHZ = 7 *5 MHz WCDMA frequency channels),
and frequency planning methods.
The penetration of the UMTS at the introduction will not necessarily include all populated
environments. Thus, starting in the main cities, and suburban areas, 3G network coverage can
progress in phases, i.e. 50 %, 75%, 99% for business strategic reasons within a region. With the
above data, a theoretical coverage and capacity plan is determined [25].
UMTS Radio Access Network Planning
School of Engineering Design & Technology 26
4.3. Basic Traffic Dimensioning Input 4.3.1. Traffic Classes From end-user and application point of view four major traffic classes can be identified:
• Real time applications
o Conversational class (e.g. voice), where the fundamental characteristics for QoS
are to preserve time relation (variation) between information entities of the stream
and to have a low delay [26] [27]
o Streaming class (e.g. streaming video), where the fundamental characteristics for
QoS are to preserve time relation (variation) between information entities of the
stream. [26] [27]
• Non-real time applications
o Interactive class (e.g. web browsing), where a request/response pattern is of
importance and the payload content must be preserved. [26] [27]
o Background class (e.g. background download of emails), where the destination is
not expecting the data within a certain time but with preserved payload content.
Conversational and streaming classes are intended to carry real-time traffic flows, like speech
and video streaming.
Interactive class and background class are mainly meant to be used by traditional Internet
applications like WWW, e-mail and by a number of vertical applications like Telemetry and E-
Commerce. [26] [27]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 27
4.3.2 Input Analysis One of the most important steps in any dimensioning process is defining the input data
thoroughly. This can be difficult in some circumstances due to limited or vague input
requirements. It is up to the dimensioning engineer to interpret the input data so that it reflects
reasonable values. Table 4.3 depicts a typical example of the input data needed for network
dimensioning.
Table 4.3 Examples of input data [8]
4.3.2.1 Required Services
The required services are then mapped onto the existing Radio Access Bearers. The number of
required individual bearers (RABs) are kept to a minimum. Up to five-six bearer types is
reasonable for a typical dimensioning case; one RAB can handle several different services.
Table-4.4 depicts a typical example of various RABs required for different services.
The following items can be useful to consider when selecting RAB:
Service Traffic during BH Speech - AMR 12000 Erl Video service 38.4 Mbps
UL : 19.2 Mbps DL : 38.4 Mbps UL : 16 Mbps DL : 64 Mbps
Total Environment Service City area Indoor- all services
In car for web service and voice
Subscriber distributionSpectrum
2 x 10 MHz50 % city area50 % suburban
Coverage70 km sq
1600 km sq
600k
50k
130k
400k Subscribers
20kTraffic Loadand Capacity
Environment and services
Miscellaneous
Ftp service
Suburban /outskirts
Internet web service
UMTS Radio Access Network Planning
School of Engineering Design & Technology 28
• Delay Criteria
Delay criteria indicate whether to use a conversational/streaming or interactive/background
type RAB. As a rule of thumb use conversational if the delay requirement is less than 0.5
seconds. In case the delay is greater than 1 second an interactive/background RAB can be used.
• Maximum User Data Rate/Throughput
This gives some indication as to which type of bearer to use. It is not necessary to have a RAB
that conforms exactly to the maximum user data rate. The given service may be specified with a
lower data rate than the RAB rate.
• Other Service Requirements
Some of the information given may not be expressed as hard numbers specifying delay criteria
and throughput. Often the service is described from the end user perspective. Then the service
has to be interpreted based on those criteria.
Table 4.4. Example of mapping of services to Radio Access Bearers [8]
Service RAB MotivationSpeech - AMR Speech
Video serviceCircuit 128. . .(conversational )
A video service requires data transfer at lowdelay. A high data rate is required for the qualityaspect of the video link.
Ftp serviceCircuit 64 ..(Conversational)
A conversational class bearer is used since it isexpected that the user does not send burstytraffic but long constant streams of data. Themedium data rate is a design choice; norequirements for the maximum data rate havebeen given.
Internet Web . .service
Packet 64/384(interactive)
This service does not require low delay data andtherefore an interactive (packet) RAB can beused. The medium /high data rate in the UL/DLis a design choice chosen due to the strongasymmetry of the traffic volume.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 29
4.3.3. Determining the Average User Profile It is often convenient to define an “average user” to obtain a good feeling for the traffic
distribution generated by the service provider. The “average user” defines the traffic for all
services during the busy hour. Besides defining the average traffic during the busy hour several
other parameters must be defined that describes quality parameters for the users: [8]
• Activity factor
This has an impact on the air interface dimensioning as well as the hardware dimensioning. A
low activity factor allows more users to share the same spectrum. This however, requires more
allocation of hardware resources. The activity factor for speech cannot be used directly to obtain
a capacity gain since there is no activity factor to the signaling overhead. Instead, the capacity is
modeled through the pole capacity. For higher data rates however the signaling overhead is
negligible and for dimensioning purposes it is possible to utilize the gain fully.
• Retransmission rate
In the radio interface there are always retransmissions due to frame errors. This reduces the
total throughput of the channel and must be compensated for in the dimensioning. (Estimated
10%)
• Grade of service (GoS)
Used for circuit switched traffic, GoS defines how many calls that are allowed to be blocked.
Table 4.5 shows acceptable GOS for various services and an average user profile.
BH Traffic Average bit Retrans - (UL/DL) rate/user mission
Speech AMR 20 mErl 0.5 2% Video service C128 0.5 mErl 1 2% Ftp service C64 0.5 / 1m Erl 1 2%
Best effort, maxsystem throughput
10kbps 10% Web service P64/384 27/ 107 bps
Service RAB Activity factor GOS
Table 4.5 Example of an average user profile [8]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 30
4.4. Basic Traffic Dimensioning The purpose of the basic traffic dimensioning is to find the maximum number of users
supported by the actual cell under investigations. In a WCDMA network this process becomes
quite complex. Three types of services can be supported in a cell; voice, circuit switched data
and packet switched data services. The different service types must be treated differently as they
are carrying different applications. Voice and circuit switched data services require allocation of
fixed rate resources to provide the actual service while packet switched traffic can utilize the
remaining resources efficiently due to its elastic nature.
• Speech Only Networks
In traditional speech only services traffic dimensioning is based on the Erlang-B calculations.
This method calculates the number of users in a cell (with a predefined offered traffic per user of
e.g. 30 mErlang) based on the actual network resources for a given call blocking probability (e.g.
2%). Generally, Erlang tables are used for this purpose. Figure 4.2 indicates dimensioning of a
cell with only one speech service. The blocking probability increases as the number of user
increases. The input data used in this example corresponds to the existence of 59 channels for
voice. Then the cell can support at most 1623 users if the blocking probability is restricted to 2%.
Figure 4.2. Erlang-B blocking probability [8]
Number of speech users
1623 speech users
3
2
1
0
6
5
4
Parameters: 3 Sector cell 1 RF carrier Max 59 voice Channel available 30 m Erlang
10 0 0 10 50 110 0 1150 12 0 0 12 5013 0 0 13 50 14 0 0 14 50150 0 1550 16 0 0 16 50 170 0 1750 18 0 0
UMTS Radio Access Network Planning
School of Engineering Design & Technology 31
• Multi Service Networks
In multi service networks several services with different parameters share the same resource.
Therefore, the inputs of multi-service cell dimensioning are the offered load, the required
resource (effective bandwidth), the requirements on blocking for each service and the total
resource available in the cell. Figure 4-3 shows an example of multi-rate blocking probability
calculations using five different circuit switched services.
For a given number of subscribers the blocking probabilities are different for different services
because they share the same pool of resources. The more resources a service needs for one user
the higher is the blocking probability, e.g. CS 384 is assumed to need 23 times the resources of
voice in this example. If 2% blocking probability for each service is taken as the criteria of the
dimensioning 133 users can be supported with the given in data. [8]
Figure 4-3 Example of multi-rate blocking probability calculations (%)
The actual channel utilization for the example above is shown in figure 4-4, It illustrates that
handling large bandwidth circuit switched services may result in very low utilization of the
available channel resource.
Number of users 133 users
Parameters: 3 Sector cell 59 voice Channel available 30 m Erlang for voice 1mErlang for all other services
Blocking Probability (%)
50 100 150 200 250 300 350 400 450
Circuit 384 Circuit 144
Circuit 64
Circuit 32
Voice
87
6
5
4
3
2
1
0
UMTS Radio Access Network Planning
School of Engineering Design & Technology 32
Figure 4-4 Channel utilization example
Packet Data Services
Voice and circuit switched services should be handled in the way described above but for
packet switched services this leads to over dimensioning.
In packet switched applications the minimum average throughput can be taken as dimensioning
criteria. The part of the resource which is not used for circuit switched services can be utilized by
packet services. This part of the total resource is clearly visible in Figure 4-3. For example if the
number of users are 133 the channel utilization becomes 16%. That means that on average 84%
of the resources are available for best effort services.
Best effort means that the packet service can utilize the resource that is available, but there are
no guarantees on “blocking probabilities”, delays or throughput. [8]
Number of users 133 users
Channel Utilization (%)
5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 4 5 0
4 03 5
3 0
2 5
2 0
1 5
1 0
5
0
UMTS Radio Access Network Planning
School of Engineering Design & Technology 33
5. COVERAGE AND CAPACITY DIMENSIONING The scope here is to outline how to calculate the capacity and coverage of the radio access
network. The methods described can be used for rough estimates suitable in the dimensioning
process.
5.1 Capacity
Capacity is defined as the total number of simultaneous users the system can support, and
quality is defined as the perceived condition of a radio link assigned to a particular user; this
perceived link quality is directly related to the probability of bit error, or bit error rate (BER).
The actual capacity of a CDMA cell depends on many different factors, such as receiver
demodulation, power-control accuracy, and actual interference power introduced by other users
in the same cell and in neighboring cells. [28]
In digital communication, we are primarily interested in a link metric called Eb /No, or energy
per bit per noise power density.
This quantity can be related to the conventional signal-to-noise ratio (SNR) by recognizing that
energy per bit equates to the average modulating signal power allocated to each bit duration; i.e,
Where S is the average modulating signal power and T is the time duration of each bit. Notice
that (5.1) is consistent with dimensional analysis, which states that energy, is equivalent to power
multiplied by time. We can further manipulate (5.1) by substituting the bit rate R, which is the
inverse of bit duration T:
S R Eb =
Eb S T = …………. (5.1)
UMTS Radio Access Network Planning
School of Engineering Design & Technology 34
Eb / No is thus
We further substitute the noise power density No, which is the total noise power N divided by the
bandwidth W; that is,
Substituting (5.3) into (5.2) yields
Equation (5.4) relates the energy per bit E N b / 0 to two factors: the signal-to noise ratio (S /N)
of the link and the ratio of transmitted bandwidth W to bit rate R. The ratio W /R is also known as
the processing gain of the system. The SNR of one user can be written as
Where M is the total number of users present in the band. This is so because the total
interference power in the band is equal to the sum of powers from individual users. Figure 5.1
illustrates the principle behind (5.5).
Power
Figure 5.1. SNR (Signal to noise) experienced by a user. [28]
Eb S No
= RNo
……….…. (5.2)
N No =
W
……….…. (5.3)
Eb S No
= N
…………... (5.4) W R
S 1 N
= M - 1
………..…. (5.5)
User A7
User A1 User A2
Frequency
S =
N
1
6 A1
UMTS Radio Access Network Planning
School of Engineering Design & Technology 35
In CDMA, the total interference power in the band is equal to the sum of powers from
individual users. Therefore, if there are seven users occupying the band, and each user is power-
controlled to the same power level, then the SNR experienced by any one user is 1/ 6.
We proceed to substitute (5.5) into (5.4), and the result is
Solving for (M − 1) yields
Note that if M is large, then
5.1.1 Effects of Loading
Equation (5.8) is effectively a model that describes the number of users a single CDMA cell
can support. This single cell is omni directional and has no neighboring cells, and the users are
transmitting 100% of the time. In reality, there are many cells in a CDMA cellular or PCS
system. Figure 5.2 shows that a particular cell (cell A) is bordered by other CDMA cells
supporting other users. Although these other users from other cells are power-controlled by their
respective home cells, the signal powers from these other users constitute interference to cell A.
Therefore, cell A is said to be loaded by users from other cells. [28] Equation (5.6) is modified to
account for the effect of loading:
Where η is the loading factor, η is a factor between 0% and 100%. In the example shown in
Figure 5.3, the loading factor is 0.5 resulting in (1 + 0.5), or a 150% increase of interference
W R
Eb 1 No
= M - 1
……….….. (5.6)
(W / R) (Eb / No )
= M - 1 ………… (5.7)
(W / R) (Eb / No )
≈ M ……….….. (5.8)
W R
Eb 1 No
= (M – 1)
……… (5.9) 1
1 + η
UMTS Radio Access Network Planning
School of Engineering Design & Technology 36
above those introduced by home users alone. The inverse of the factor (1+ η) is sometimes
known as the frequency reuse factor F; that is,
The frequency reuse factor is ideally 1 in the single-cell case (η = 0). In the multicell case, as
the loading η increases, the frequency reuse factor correspondingly decreases.
Figure 5.2 Interference introduced by users in the neighboring cell. [28]
Power
Figure 5.3 Loading factor as perceived by cell A. [28]
1 F =
( 1+η ) ……….…. (5.10)
User C2
User A7
Frequency
User C1 User B2 User B1
User A1 User A2
Loading Factor = 0.5
UMTS Radio Access Network Planning
School of Engineering Design & Technology 37
5.1.2 Effects of Sectorization
The interference from other users in other cells can be decreased if the cell in question is
sectorized. Instead of having an omni-directional antenna, which has an antenna pattern over 360
degrees, cell A can be sectorized to three sectors so that each sector is only receiving signals over
120 degrees. In effect, a sectorized antenna rejects interference from users that are not within its
antenna pattern.
This arrangement decreases the effect of loading by a factor of approximately 3. If the cell is
sectorized to six sectors, then the loading effect is decreased by a factor of approximately 6. This
factor is called sectorization gain. [28] [25]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 38
6. LINK BUDGET OVERVIEW
Link budget planning is part of the network planning process, which helps to dimension the
required coverage, capacity and quality of service requirement in the network. UMTS WCDMA
macro cell coverage is uplink limited, because mobiles power level is limited to (voice terminal
125mW). Downlink direction limits the available capacity of the cell, as BTS transmission
power (typically 20-40W) has to be divided to all users. In a network environment both coverage
and capacity are interlinked by interference. So by improving one side of the equation would
decrease the other side. System is loosely balanced by design. [6]
The aim of the link budget design is to calculate maximum cell size under given criteria:
• Type of service (data type and speed)
• Type of environment (terrain, building penetration)
• Behavior and type of mobile (speed, max power level)
• System configuration (Node B antennas, Node B power, cable losses, handover gain)
• Financial and economical factors (use of more expensive and better quality equipment or not)
and to match all of those to the required system coverage, capacity and quality needs with each
area and service. [6]
Figure 6.1 Link Budget Process flow block diagram [29]
�PA Power �Diversity (Tx Rx) �Eb/No �Processing Gain �……
Node B Site �PA Power �Diversity (Tx Rx) �Eb/No �Processing Gain �……
�Cable losses �Antennas �Site Configuration ...(bi, tri sectorial)
� Margins � Propagation
Service
Cell Range Traffic offered per cell
MS
UMTS Radio Access Network Planning
School of Engineering Design & Technology 39
Figure 6.2 Link Budget Flow Chart [29]
Link budget calculations give the loss in the signal strength on the path between the mobile
station antenna and base station antenna. These calculations help in defining the cell ranges
along with the coverage thresholds. Coverage threshold is a downlink power budget that gives
the signal strength at the cell edge (border of the cell) for a given location probability [A].
Link budget calculations are done for both the uplink and downlink . As the power transmitted
by the mobile stating antenna is less than the power transmitted by the base station antenna, the
uplink power budget is more critical than the downlink power budget. Thus the sensitivity of the
base station in the uplink direction becomes one of the critical factors as it is related to receptions
of the power transmitted by the mobile station antenna. In the downlink direction, transmitted
power and the gains if the antennas are important parameters. In terms of losses in the
equipment, the combiner loss and the cable loss are to be considered. Combiner loss comes only
in the downlink calculations while cable losses are incorporated in both directions [A].
Link Budget @ X% load Design assumptions
Cell size Cell Capacity
Sites for Coverage Sites for Traffic
Comparison Decision
Final number of Sites
Adjust Load
UMTS Radio Access Network Planning
School of Engineering Design & Technology 40
6.1 WCDMA Technology Review
Wideband CDMA system occupy a bandwidth of 5 MHZ. Digital information is spread by a
channalization code and then scrambled by a scrambling code. Each of these codes is a digital
sequence at the “chip rate of 3840000 chips per second. Multiplying the message by these high
chip rates has the effect of spreading the signal power over a wider bandwidth. Many channels
can be multiplexed into the same frequency band at the base station by utilizing orthogonal
channalisation codes. The overall effect is the each individual channel contributes only a small
fraction of the total power transmitted by the base station. Because the scrambling code is a
“Pseudo Random Binary Sequence” the transmitted signal will have the appearance of noise.
Each individual message channel will be buried in the noise and will need to be extracted at the
receiver. This is achieved by de-scrambling and de-spreading at the receiver making use of the
processing gain where each channel is de-spread using its own unique channalisation code. On
the uplink each mobile has a unique scrambling code that allows the base station to discriminate
between many users. [29]
On the downlink the base station transmits synchronization and pilot channels along with the
message channel. The pilot channel is simply an un-modulated scrambling code sequence. This
is used to allow the wideband radio channel characteristics to be estimated and the rake receiver
within the mobile station to be automatically programmed. Further it is the pilot signals from
various base stations that the mobile monitors in order to inform handover decisions.
One vital parameter known as Ec/Io (the ratio of the energy perchip in the pilot signal to the
received noise density). In order to use the pilot signal effectively, the value of Ec/Io must be at
least “-15” dB. Setting the transmitted power level of the pilot forms a significant element of
network planning. [29]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 41
Further to the pilot channel being received at an appropriate level, each service requires a certain
signal to noise ratio in order to be effective. This signal to noise ratio is known as the Eb/No ratio.
The relationship between Eb and Ec is defined by the processing gain and can be calculated by
dividing the chip rate by the actual data rate. The necessary value of Eb/No in order to deliver an
acceptable service varies from service to service and depends on the condition prevalent in the
radio channel. Generally, the lower the data rate the greater the overhead imposed by the control
channel and hence the higher the value of Eb/No that should be targeted (because the
transmission of actual user bits occupies a smaller percentage of the total time. Values of Eb/No
have a big impact on the network performance. Typical values vary from 1.5 dB to 10 dB.[29]
Orthogonality between the canalization codes will allow a further processing gain to be
realized in the downlink. In practice, multipath phenomenon reduce the benefits from
orthogonality. This is accounted for by introducing an orthogonality factor that assumes a value
between zero and one. A value of one represents the situation where perfect orthogonality is
maintained and zero represents the situation where there is effectively no orthogonality between
the different codes. In typical practical situation, a value of 0.6 has been found to be
appropriate.Two further key parameters for a UMTS channel are therefore the target Eb/No value
on the uplink and the downlink. Failure to achieve these will result in connection failure. [25]
The fact that each user affects all other users, influences the admission control algorithms within
WCDMA system. Admitting a new user will increase the noise expericenced by all existing user
channels. This phenomenon is referred to as “Noise Rise”. Noise Rise escalates as more users
access the system, It has the effect of reducing the maximum path loss between mobile and user
and hence it reduces the coverage distance. This “cell breathing” phenomenon should be limited
if coverage is to be maintained. This entails setting a limit to Noise Rise as a part of the system
planning procedure. [22]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 42
6.2 Link Budget
The new terms introduced, most notably Noise Rise and Processing Gain, appear in the link
budget for a UMTS radio bearer. Because the mobile (UE) has much less power available to it
than the cell, coverage is normally “uplink limited” and, at least in the initial stages of planning,
it is the uplink budget that is of most interest. These are not dissimilar from the link budget for
GSM. Naturally the transmit power of the UE (typically +21 dBm) and the thermal noise floor of
the cell receiver (typically -104 dBm) play an important part. The noise power quoted is larger
that that for GSM links. This is because the bandwidths is much larger (nominally 3840 kHz or
65.8 dBHz) KTB is equal to -108.1 dBm. A typical noise figure of 4.1 dB results in the value of
-104 dBm quoted above. [30]
The cell must receive sufficient power to deliver the required Eb/No value when the Noise Rise
level is at its limit. The values, combined with the processing gain (which is dependent on bit
rate) allow us to derive a value for the minimum acceptable receiver power at the cell
(effectively the receiver sensitivity).
For example, consider the following parameter values.
Noise Rise limit : 4dB
Cell thermal Noise Floor -104dBm
Target Eb/No 5dB
Processing Gain (full rate Voice) 25dB (Ratio of Chip rate to Bit Rate)
Minimum acceptable receive power = -104 +4+6-25 = -120 dBm
If the UE transmits at 21 dBm then the maximum loss that can be tolerated is 141dB.
This is the overall “link loss”. If we wish to determine the allowable air interface path loss then
we need to consider the antenna gain and “miscellaneous losses” (including feeder loss and body
UMTS Radio Access Network Planning
School of Engineering Design & Technology 43
loss) . Suppose the antenna gain is 17 dBi and the miscellaneous losses amount to 4dB then the
maximum path loss allowed is 154 dB.
It is important to remember that this does not consider any margins (such as “log-normal
fading” (LNF) also known as “shadowing”) or building penetration loss. So, in practice, 130 dB
could be a safer value to consider.
The above link budget has been conducted for voice. It is highly likely that UMTS networks
will provide coverage for higher services such as Video telephony (VT). Video telephony will
utilize 64 kbits/s bearer and, therefore , the processing gain will be reduced to 17.8 dB. If all
other parameters remain the same, the maximum path loss allowed will reduce from 154 dB to
146.8 dB. This difference in allowed path losses immediately shows a problem confronting the
UMTS radio network planning, the coverage will be different for different services. The uplink
coverage range for voice will be typically 60 % larger than for VT. [30]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 44
6. 3. Uplink Dimensioning
6.3.1 Uplink Capacity
The uplink pole capacity, Mpole, is the theoretical limit for the number of UEs that a cell can
support. It is service (RAB) dependent. At this limit the interference level in the system is
infinite and thus the coverage reduced to zero. Mpole is calculated according to: [8]
where γ ,
the C/I target of the RAB in linear units, is calculated as:
where
Rchip is the chip rate (=3.84 Mcps) [cps],
Rinfo is the information bit rate for the RAB [bps],
PG is the processing gain, i.e. the ratio of the system chip rate and the information bit rate [dB],
F is the ratio of the interference from other cells and the interference generated in the own cell
Eb/Io is the target bit energy to interference power ratio [dB].
* γ�=10 (C/I)/10 if C/I is given in [dB]
6.3.1.1 The Eb/I0 value
The Eb/Io values that should be used are those that are needed to reach the quality requirements.
The quality requirements are
- Speech : BER < 10-3
- Circuit switched data : BER < 10-6
- Packed switched data : BLER 10%
1 (1+F) γ
M pole = ……….…. (6.1) 1 +
(Eb / Io) - PG
10 γ = ……….…. (6.2) 10
(Eb / Io) / 10 Rchip/Rinfo
C / I = *………. (6.3)
UMTS Radio Access Network Planning
School of Engineering Design & Technology 45
Eb/Io values depend on the type of environment/channel model assumed. All values in this
chapter (Table 6.1, Table 6.5) are examples taken from the RTT submission to ITU, assuming
the pedestrian A channel model, plus an additional implementation margin of 1 dB.
RAB Pedestrian A
Speech 12.2 kbps 4.2
Circuit 64 kbps 3.9
Packet 128 kbps 1.9
Table 6.1. Uplink values of Eb/I0 [8]
6.3.1.2 The F value
The equation for pole capacity is straightforward except for the F value. F is the ratio between
the interference from other cells and the interference generated in the own cell. This means that F
depends on the characteristics of the cell plan such as numbers of sectors, wave propagation
characteristics, log-normal fading and antenna beam width. A typical F-value for a three-sector
site is 0.93. [8]
6.3.1.3 Table of Mpole
Table 6.2 contains approximate values of Mpole for a three-sector configuration, calculated using
the previous equation
RAB Pedestrian A
Speech 12.2 kbps 95 Circuit 64 kbps 14 Packet 128 kbps 11 Table 6.2. Uplink values of Mpole [8]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 46
6.3.2 Uplink Coverage
6.3.2.1 Loading
In WCDMA analysis, it is customary to define the concept Loading:
where M is the number of simultaneous users in the cell.
For a multi-service system where the services utilize different types of RABs, the expression can
be generalized as:
where
Mn is the number of simultaneous users for the nth RAB
Mpole , n is the uplink pole capacity for the nth RAB.
6.3.2.2 Uplink load limit
A WCDMA system cannot be loaded up to 100%. To secure a well performing network the
uplink load used in the dimensioning process should be of the order of 50-60 % depending on the
implementation of radio network functionalities. [8]
6.3.2.3 Noise Rise
The more loaded the system, the more interference is generated. This has the effect that the
receiver noise floor is higher in a loaded system as compared to an unloaded system. The
increase is often referred to as noise rise and is denoted IUL.
The noise rise can be calculated from the relative uplink system load as follows:
where:
IUL is the noise rise [dB] and the Loading is the uplink system loading [%].
M M pole
Loading = ……….…. (6.4)
M1
M pole,1 Loading = … (6.5) M2
M pole, 2
M3
M pole3 + + +
1 1 - Loading
IUL = ……….…. (6.6) 10 log
UMTS Radio Access Network Planning
School of Engineering Design & Technology 47
6.3.3 Uplink budget
Having determined the noise rise, a conventional link budget for the uplink can be set up (Fig 6-3):
Figure 6-3 Schematics of components included in the link budget. [8]
G=Gain, L=Loss, ant=antenna, f+j=feeder & jumper, UE=User Equipment RBS=Radio Base
Station.
SSRBS = PUE – Lpath +Gant –L f + j � SSdesign …………………………………………………….(6.7)
where the design criterion, SSdesign, is equal to the sensitivity of the radio base station, RBSsens,
plus a number of margins as
SSdesign = RBSsens + BL + CPL + BPL + PCmarg + IUL + LNFmarg………………………….…(6.8)
where:
Lpath is the path loss (on the uplink) [dB].
PUE is the maximum UE output power (= 21 or 24) [dBm].
RBSsens is the RBS sensitivity. It depends on the RAB [dBm].
LNFmarg is the lognormal fading margin (this margin depends on the environment and the
desired degree of coverage) [dB].
IUL is the noise rise [dB].0
PCmarg is the power control margin, dependent on channel model [dB].
BL is the body loss (= 0 or 3)[dB].
CPL is the car penetration loss (= 6) [dB].
BPL is the building penetration loss [dB].
Gant is the sum of the RBS antenna gain and UE antenna gain [dBi].
Lf+j is the loss in feeders and jumpers [dB].
UMTS Radio Access Network Planning
School of Engineering Design & Technology 48
The path loss is the difference (in dB) between the transmitted power and the received power.
The maximum pathloss allowed, Lpathmax, is obtained when SSRBS = SSdesigh so solving for Lpathmax
we obtain
Lpathmax = P UE – RBS sens – I UL - LNF marg – PC marg – BL – CPL – BPL +Gant – L f + j ………(6.9)
The RBS sens depends on the user data rate and the E b/I o target value as
RBS sens = Nt + Nf + 10·log(Ruser) + E b/I o ……………………………………………..……(6.10)
Nt is the thermal noise power density = -174 dBm/Hz
Nf is the noise figure = 3 dB with TMA (Tower mounted Amplifier), 4 dB without it.
Ruser is the user bit rate (information bits per second, excluding retransmission, i.e. the
service rate of the RAB)
UMTS Radio Access Network Planning
School of Engineering Design & Technology 49
6.4 Cell size
Once the maximum path loss is calculated we can calculate the maximum cell rage, based on the
type of the topography and other margins.
When roughly estimating the size of macro cells, without respect to specific terrain features in
the area, a fairly simple Okumura-Hata propagation formula is often used. [31]
L path = A - 13.82logHb +(44.9-6.55logHb)logR - a(Hm) [dB]………………………………..(6.11)
where
A = 155.1 urban areas
A = 147.9 suburban and semi-open areas
A = 135.8 rural areas
A = 125.4 open areas
Hb = base station antenna height [m]
Hm = UE antenna height [m]
R = distance from transmitter [km]
a(Hm) = 3.2(Log(11.75*Hm))2- 4.97
a(1.5) = 0
The cell range at is then given by:
R = 10 α, where α = [Lpath - A + 13.82logHb + a(Hm)]/[44.9 - 6.55logHb]………………..…(6.12)
that is
R pathmax = 10α, where α = [Lpathmax - A + 13.82logHb + a(Hm)]/[44.9 - 6.55logHb]…………(6.13)
The Okumura-Hata formula only can be used for rough estimates. For more precise calculations,
network-planning tools are used.
For small cells in an urban environment the cell range is typically less than 1 km and in that case
the Okumura-Hata formula is not valid. The COST 231-Walfish-Ikegami model, gives a better
approximation for the cell radius in urban environments. The path loss according to Walfish-
Ikegami is: [31]
Lpath = 155.3 + 38logR – 18log(Hb – 17) [dB]
R = 10 α , where α = [Lpath – 155.3 + 18 log(Hb – 17)]/38………………..……...…………..(6.14)
UMTS Radio Access Network Planning
School of Engineering Design & Technology 50
EXAMPLES
Example 1:
Calculation for the capacity and the range of a three-sector site at maximum loading. Assume
urban environment and speech 12.2 kbps
1) For 12.2 kbps speech RAB in urban environment Mpole is 95 simultaneous users (Table 6.2).
2) At 50% loading this is equivalent to 47 simultaneous users, or a site capacity of three-sector
site 3 x 47 = 141 simultaneous users.
3) The noise rise (IUL) is calculated according to 3 dB at 50% loading.
The maximum path loss can be calculated according to the Lpathmax equation. The result depends
on the environment and the desired degree of coverage. In Table 4 the link budget is calculated,
considering a three-sector sites with TMA and 95% probability of coverage. For configurations
with TMA L f+j should be set to zero.
From equation 6.9 we get
Lpathmax = P UE – RBS sens – I UL - LNF marg – PC marg – BL – CPL – BPL +Gant – L f + j ………(6.9)
Table 6.3. Uplink link budget for voice 12.2 kbps and 95% probability of coverage. [8]
Coverage [%] UrbanPUE 21RBSsens -125.9LNFmarg 4PC marg 2I UL 3BL 3Gant 17.5L f+j 0L pathmax (Outdoor) 152.4CPL 6L pathmax (in-car) 146.4BPL 18L pathmax (indoor) 134.4 dB
UMTS Radio Access Network Planning
School of Engineering Design & Technology 51
6.4 Downlink Dimensioning
6.4.1 Downlink Curves
The downlink equations are more complex than the uplink ones. For the downlink it is not as
easy to separate the coverage and capacity in the way that is done for the uplink. The main
difference as compared to the uplink is that the UEs in the downlink share one common power
source. Thus the cell range is not dependent only on how many UEs there are in the cell but also
on the geographical distribution of the UEs.
Despite orthogonal codes, the downlink channels cannot be perfectly separated due to multi-
path propagation. This means that a fraction of the BS power will be experienced as interference.
Also, the downlink interference, caused by neighboring base stations transmitting channels non-
orthogonal with the serving base station, is user equipment position dependent.
Typical parameter values have been used and 20% of the power has been allocated to control
channels. A homogenous user distribution has been assumed. To account for non-homogenous
distributions and log-normal fading a 5 W headroom has been used. Thus the curves are based on
a total power Ptot,s of 15 W instead of 20 W. This roughly corresponds to 95% coverage
probability.
Figure 6.4 Example of capacity versus cell range in an urban environment. Each curve
corresponds to a certain downlink margin (DLmarg) [8].
Loading %
DLmarg
Cell Range in Km
Urban 3 sector site
UMTS Radio Access Network Planning
School of Engineering Design & Technology 52
6.4.2 Downlink Link Budget
A downlink link budget is obtained by determining DLmarg according to the following equation.
All units are in dB:
DLmarg = BL + CPL + BPL + ∆Gant + Lf+j + Lslant +LTMA + ∆Nf + ∆A0 …………………(6.15)
where:
BL is the body loss, 0 or 3 dB.
CPL is the car penetration loss, 6 dB.
BPL is the building penetration loss.
∆Gant is the difference in antenna gain compared to the value used in the curves: ∆ Gant =
17.5 – Gant where Gant [dBi] is the sum of the BS and the UE antenna gain.
L f+j is the loss in feeders and jumpers.
∆Nf is the difference in UE noise figure compared to the value used in the curves: ∆Nf =
Nf –7 (where Nf is the noise figure of the UE (7 dB recommended).
Lslant is the slant loss (1 dB) associated with cross-polarized antennas.
LTMA is the insertion loss of the TMA (if used).
∆A0 is the difference of the distance independent term, in Okumura Hata, compared to
the value used in the curves:
∆A0 = A0 – A0curves, (A0 = A – 13.82 logHb and A0curves is 134.7, Hb = 30 m in this case .)
Once DLmarg is determined it is possible to check what capacity and coverage that can be
obtained by using the graphs. 6.4.2.1 Tables of Mpole
Some approximate values of Mpole for a three-sector configuration. (Eb/Io value based on the RTT
submission to IUL).
Table 6.4. Downlink values of Mpole (three-sector site). [8]
RAB Pedestrian A Speech 12.2 kbps 110 Circuit 64 kbps 14
Packet 128 kbps 11
UMTS Radio Access Network Planning
School of Engineering Design & Technology 53
6.4.2.2 Downlink load limit
The values in Table 6.4 correspond to 100% system load. To secure a well performing network
the downlink load used in the dimensioning process should be of the order of 65-75% depending
on the implementation of radio network functionalities.
6.4.2.3 EXAMPLES
• Single service
The number of simultaneous voice users in an urban environment at a range of 1.5 Km is
calculated:
1. DLmarg is calculated to 25.7, using the DLmarg equation (6.15), with the following: assumptions:
Service: Speech 12.2 kbps
Body loss BL 3 dB
Car penetration loss CPL 0 dB
Building penetration loss BPL 18 dB
Antenna gain Gant 17.5 dBi
Feeder and jumper loss Lf+j 5 dB
Slant loss Lslant 1 dB
TMA insertion loss LTMA 0.4 dB
UE noise figure Nf: 7 dB
Antenna height 40m
A0 = 155.1 – 13.82log40 = 133 (see 6.11) 2. In Figure 6.4, the relative load at which the curve for DLmarg = 25 dB crosses the 1.5 km range
is found: approx. 40%. This is below the maximum load limit.
3. The Mpole value for Speech 12.2 kbps is found in Table 6.4 i.e : 110 users.
4. Finally, the supported relative load is calculated: 110 x 0.4 ≈ 44 simultaneous users.
Thus, one cell would be able to support approximately 44 simultaneous voice users using the
assumptions stated above. [8]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 54
• Mixed Services
In the same way as for the uplink, the total load can be distributed amongst different services
according to equation. If instead of the 44 speech users at 40% loading, as calculated in the
example earlier, the load is shared between data users and speech users, the number of
simultaneous users changes. At 50% Circuit 64 kbps users and 50% speech 12.2 kbps users, the
number of simultaneous users can be calculated using equation 6.5 :
Five voice users and five CS 64 kbps users can use the resources simultaneously.
0.5 x 14
0.4 0.5 x = 110
x = 9.9 M1 = M2 = 4.9 ≈5 +
UMTS Radio Access Network Planning
School of Engineering Design & Technology 55
6.5 Link Budget Margins
This section describes the purpose and the values of the margins that have been used in the
formulas in previous sections. In an ideal situation the maximum possible path loss between a
RBS and an UE would be the difference between the output power of the UE and the RBS
sensitivity. However in a network design, various margins must be added in order to cater for
such things as body loss and fading. These margins are:
6.5.1 Log –Normal Fading
The signal strength value predicted by wave propagation algorithms can be considered as a
mean value of the signal strength in a small area. The value is determined by the resolution and
accuracy of the model. Assuming that fast fading has been removed (averaged out), the local
mean value of the signal strength fluctuates in a way not modeled in the prediction algorithm.
This deviation of the local (measured) mean has nearly a normal distribution in dB, compared to
the predicted mean. Therefore this variation is called lognormal fading.
In the result from a prediction in for example WCDMA planner, 50% of the locations (for
example at the cell borders) can be considered to have a signal strength that exceeds the
predicted value. In order to plan for more than 50% probability of signal strength above the
threshold, a lognormal fading margin, LNFmarg, is added to the threshold during the design
process. [8]
The value of the required margins has been determined through simulations. For a typical
urban environment and 95% probability of coverage a lognormal fading margin of
approximately 4 dB is easily derived from Figure 6.5.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 56
Figure 6.5 Lognormal fading margins. Handover gain is included in these curves. [8]
6.5.2 Handover gain
The log-normal fading margins presented above reflect the case where the UE has the
possibility to make soft handover to other cells when experiencing poor coverage. Allowing
handover means that the log-normal fading margins can be reduced as compared to the single
cell case. This reduction is referred to as handover gain and is included in the values for log-
normal fading margins. [8]
6.5.3 Power Control Margin
In a WCDMA system fast power control (1500 Hz) is employed. For slowly moving UEs the
power control has the ability to compensate for the fast fading, thus reducing the Eb/Io. However,
due to the characteristics of the fast fading, more power will be required in the fading dips than
UMTS Radio Access Network Planning
School of Engineering Design & Technology 57
the corresponding reduction in the fading tops. The result is that each UE (BS), has to increase
its average power in order to combat fast fading. This effect is called TX increase. Sensitivity
degradation for UEs located at cell borders also appears, since the UE power control at cell
borders no longer can fully compensate for fading dips. To cater for the combined effect of TX
increase and the sensitivity degradation at cell borders a power control margin PCmarg of
typically 2 .0 - 5.0dB is used in the link budget. It is sometimes considered as Fast Fading
Margin. [8]
6.5.4 Slant Loss
A drawback of cross-polarized antennas is that the propagation characteristic of the horizontal
component is somewhat worse than for the vertical component. Therefore, if cross-polarized
antennas (two antenna arrays with ±450 polarization) are used, a “slant loss” of 1 dB should be
added to the propagation.
DL slant loss Lslant = 1 dB
6.5.5 Body Loss
The human body has several negative effects on the UE performance. For example the head
will absorb energy, and the antenna efficiency of some UEs can be reduced. To cater for these
effects a margin for body loss has to be included in the link budget. The body loss margin
recommended by ETSI is 3 dB.
Generally, body loss is not applied for data services since the users will most likely not have the
terminal by the ear. [8]
Body loss for data services BLdata = 0 dB
Body loss for speech services BL = 3 dB
UMTS Radio Access Network Planning
School of Engineering Design & Technology 58
6.5.6 Car Penetration Loss
When a UE is placed in a car without external antenna, an extra margin has to be added in order
to cope with the penetration loss to reach inside the car. This extra margin is approximately 6 dB.
Car penetration loss CPL = 6 dB
6.5.7 Indoor Margins
By indoor coverage is understood the percentage of the ground floors of all the buildings in the
area where the signal strength is above a required signal level. Indoor coverage in this concerns
calculation of that required margin to achieve a certain indoor coverage in a fairly large area
compared to the average macro cell size. It is assumed that it is the macro cells in the area that
provides the major part of the indoor coverage. Hotspot micro cells in the area will of course
improve on the indoor coverage but that effect is not considered here. [8]
6.5.7.1 Building penetration loss
Building penetration loss is defined as the difference between the average signal strength
immediately outside the building and the average signal strength over the ground floor of the
building. Typical values of the mean building penetration loss, BPL, are given in Table 6.
Table 6.5 Typical values of building penetration loss, and log-normal fading environment
classification parameter σ LNF for different area types. [8]
The building penetration loss for different buildings is log-normally distributed with a standard
deviation of σBPL. Variations of the loss over the ground floor could be described by a stochastic
Environment BPL [dB] σ σ σ σ LNF(o ), [dB] σσσσ LNF(i ), [dB] σσσσ LNF(o+i ), [dB]
Dense urban 18 10 9 14Urban 18 8 9 12Suburban 12 6 8 10
UMTS Radio Access Network Planning
School of Engineering Design & Technology 59
variable, which is log-normally distributed with a zero mean value and a standard deviation of
σfloor.
Here σBPL and σfloor is lumped together by adding the two as were they standard deviations in two
independent log-normally distributed processes. The resulting standard deviation, indoor or
σ LNF(i), could be calculated as the square root of the sum of the squares. Typical values of σ LNF(i)
are presented in Table 6.5.
The total log-normal fading is composed of both the outdoor log-normal fading, σ LNF(o),and the
indoor log-normal fading outdoor σ LNF(i).The total standard deviation of the log-normal fading
is given by the square sum:
Values of σ LNF(o+i) are presented in Table 6.5. These are the values that should be used in the link
budgets when calculating the LNFmarg, required to achieve a certain area coverage probability
indoor. [8]
6.5.8 Interference Margin
The interference margin is needed in the link budget because the loading of the cell, the load
factor, affects the coverage. The more loading is allowed in the system, the larger is the
interference margin needed in the uplink, and the smaller is the coverage area. For coverage-
limited cases a smaller interference margin is suggested, while in capacity-limited cases a larger
interference margin is used. In the coverage-limited cases the cell size is limited by the
maximum allowed path loss in the link budget, and the maximum air interface capacity of the
base station site is not used. Typical values for the interference margin in the coverage-limited
cases are 1.0 -3.0 dB, corresponding to 20 to 50% loading. [8]
σ LNF(o) 2 + σ LNF(i) 2 σ LNF(o+i) =
UMTS Radio Access Network Planning
School of Engineering Design & Technology 60
7. LINK BUDGET –Examples
7.1 Maximum allowed Path Loss for – 12.2 kbps
As the coverage is normally “uplink limited” we shall use equation 6.9 to calculate the maximum
pathloss. The sample link budget illustrated in the table 7.1 is for 12.2 kbps voice service for in
vehicle users at speeds of 120 Km /hr, which allows for the soft handovers and also includes an
6 dB loss for in car use. [1]
Lpathmax = P UE – RBS sens – I UL - LNF marg – PC marg – BL – CPL – BPL +Gant – L f + j ………(6.9)
12.2 Kbps voice Value Formula UnitUEMaximum UE TX power 0.25 WMaximum UE TX power 21 PUE dBmBase StationThermal Noise Density -174 Nt dBm/Hz
BS receiver noise figure without TMA 4 Nf dB
Service Rate of RAB (excluding retransmission) 12200 Ruser Bits /SecEb/Io (ref: Table 6.1) 4.2 Eb/Io dBRadio Base Station SensitivityRBSsens= Nt + Nf+10.log(Ruser)+Eb/Io -124.9 RBSsens dBmNoise RiseSystem Loading 50 Loading %Noise rise = 10.log (1/1-50%) 3 IUL dBFading MarginCoverage Probability 95 %Log normal fading margin @ 95 % from fig 6.5 4 LNFmarg dB
Fast fading 2 PCmarg dBSoft handover margin (included in LNFmarg)LossesBody Loss 3 BL dBFeeder and jumper loss 2 Lf+j dBGainRBS antenna gain 17.5 GRBS-ant dBi
UE antenna gain 0 GUE- ant dBiCollective gain Gant = GRBS-ant +GUE-ant 17.5 Gant dBiIn car penetration loss 6 CPL dBMaximum pathloss (In car) from equation 6.9 143.4 Lpathmax-Incar dB
Table7.1 Link budget example 12.2 kbps voice
UMTS Radio Access Network Planning
School of Engineering Design & Technology 61
7.2 Maximum allowed Path Loss for – 144 kbps
The sample link budget illustrated in the table 7.2 is for an 144 kbps data service for indoor user,
which allows for the soft handovers and also includes an 18 dB loss for in building usage.
144 Kbps Data (Inbuilding coverage) Value Formula UnitUEMaximum UE TX power 0.25 WMaximum UE TX power 24 PUE dBmBase StationThermal Noise Density -174 Nt dBm/Hz
BS receiver noise figure without TMA 4 Nf dB
Service Rate of RAB (excluding retransmission) 14400 Ruser Bits /SecEb/Io (ref: Table 6.1) 1.5 Eb/Io dBRadio Base Station SensitivityRBSsens= Nt + Nf+10.log(Ruser)+Eb/Io -116.9 RBSsens dBmNoise RiseSystem Loading 50 Loading %Noise rise = 10.log (1/1-50%) 3 IUL dBFading MarginCoverage Probability 95 %Log normal fading margin @ 95 % from fig 6.5 4 LNFmarg dB
Fast fading 2 PCmarg dBSoft handover margin (included in LNFmarg)LossesBody Loss 0 BL dBFeeder and jumper loss 2 Lf+j dBGainRBS antenna gain 17.5 GRBS-ant dBi
UE antenna gain 2 GUE- ant dBiCollective gain Gant = GRBS-ant +GUE-ant 19.5 Gant dBiBuilding Penetration Loss 18 BPL dBMaximum pathloss (In door) from equation 6.9 131.4 Lpathmax-Indoor dB
Table7. 2 Link budget example 144 kbps
UMTS Radio Access Network Planning
School of Engineering Design & Technology 62
7.3 Maximum allowed Path Loss for – 384 kbps
The sample link budget illustrated in the table 7.2 is for an 144 kbps data service for indoor user,
which allows for the soft handovers and also includes an 18 dB loss for in building usage.
384 Kbps Data (Indoor User) Value Formula UnitUEMaximum UE TX power 0.25 WMaximum UE TX power 24 PUE dBmBase StationThermal Noise Density -174 Nt dBm/Hz
BS receiver noise figure without TMA 4 Nf dB
Service Rate of RAB (excluding retransmission) 384000 Ruser Bits /SecEb/Io (ref: Table 6.1) 1 Eb/Io dBRadio Base Station SensitivityRBSsens= Nt + Nf+10.log(Ruser)+Eb/Io -113.2 RBSsens dBmNoise RiseSystem Loading 50 Loading %Noise rise = 10.log (1/1-50%) 3 IUL dBFading MarginCoverage Probability 95 %Log normal fading margin @ 95 % from fig 6.5 4 LNFmarg dB
Fast fading 2 PCmarg dBSoft handover margin (included in LNFmarg)LossesBody Loss 0 BL dBFeeder and jumper loss 2 Lf+j dBGainRBS antenna gain 17.5 GRBS-ant dBi
UE antenna gain 2 GUE- ant dBiCollective gain Gant = GRBS-ant +GUE-ant 19.5 Gant dBiBuilding Penetration loss 18 BPL dBMaximum pathloss (In door) from equation 6.9 127.7 Lpathmax-Indoor dB
Table 7. 3 Link budget example 384 kbps
UMTS Radio Access Network Planning
School of Engineering Design & Technology 63
7.4 Cell Size Calculation Once the maximum path is calculated we can compute the maximum cell range for urban
environment, using equation 6.14.
R = 10 α , where α = [Lpathmax – 155.3 + 18 log(Hb – 17)]/38………………..……..………..(6.14)
• For 144 Kbps sevice
R = 10[Lpathmax – 155.3 + 18 log(Hb – 17)]/38
Hb = Node B antenna height is taken 30 m R = 10[131.4 – 155.3 + 18 log(30 – 17)]/38
R = 0.8 Km
• For 384 Kbps sevice
R = 10[Lpathmax – 155.3 + 18 log(Hb – 17)]/38
Hb = Node B antenna height is taken 30 m R = 10[127.7 – 155.3 + 18 log(30 – 17)]/38
R = 0.6 Km
Figure 7.1 Cell coverage comparision
As we can see from the figure 7.1 the radio coverage of a cell varies for different services. Which
creates a major concern while planning a UTRAN network.
Cell range for 384 Kbps service = 600 Mts.
Cell range for 144 Kbps service = 800 Mts.
Base station
UMTS Radio Access Network Planning
School of Engineering Design & Technology 64
7.5 Calculation of number of sites required in a region
At this point is would be useful to examine through an example the number of sites required in a
region
Example : a network to be designed that should cover an area of 1000 km 2
The base station to be used are 3 sectored. Each sector (cell) covers a range of 1.2 Km
Thus, area covered by each site = k*R 2
Where k= 1.95
Area covered by each site= 1.95 *1.2 2 = 2.8 KM2
Thus : total number of sites = 1000/17.55 = 357.14 � 357 sites.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 65
8. EXPANDING CAPACITY BY CONFIGURATION MODIFICATION
8.1 Adding new frequency carriers
An obvious and straightforward expansion method to improve the system’s performance is to
add new frequency carriers. Going from one to two frequency carriers, the planned capacity is
roughly doubled.
Expanding a three-sector site from one to two frequency carriers can be achieved without
adding a new cabinet at the site, for the indoor cabinet solution. Adding a third or a fourth carrier
if that much spectrum has been assigned in the license will of course further expand the capacity
in the system. [32]
8.2 Increase number of sectors
An alternative to adding new frequency carriers when expanding the network is to increase the
number of sectors. An obvious possibility is to go from three to six sectors. The sectorisation can
of course also be increased even further.
When increasing the number of sectors, the antenna beams will be narrower, which leads to
higher antenna gain. By reducing the beam width to a half, the gain is increased approximately
with 3 dB.
Further, adding more sectors also means that the site can handle more traffic. The
improvements that are achieved, when going to six sectors, can be used to improve coverage,
capacity or both of them. If the planned load in a sector exceeds 50-60%, advanced radio
network functionality is needed. [32]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 66
8.3 Using repeater solutions
Adding power, adding new frequencies and increasing the number of sectors can all be used to
improve the coverage in the system. Another alternative, for increasing the coverage, is to use
repeater solutions, i.e. RF repeaters or optical distribution systems. Both of them can be used for
coverage gap filling as well as augmenting the coverage area of a given sector.
The characteristic of a coverage gap filling is that the area to fill often is surrounded by the
sector communicating with the repeater, e.g. indoor locations or tunnels. While when
augmenting, or moving, the shape of the sector is altered, for instance when extending highway
coverage. [33]
8.4 Adding distributed antennas
Distributed antennas can be used to increase both coverage and capacity. In cases where the
traffic concentration is quite low, each antenna can be allowed to transmit the same signal. While
for areas with high capacity demand, more advanced functionality is required, so that the signal
intended for a certain user is transmitted to the antennas close to that user. By doing that, the
interference level in the system is reduced.
In areas with distributed antennas, the interference level in the system is very low, as the users
always are close to at least one antenna. This means that RBSs with distributed antennas can be
deployed in frequency bands that are already used by another RBS. Further, if the distributed
antenna system is located
8.5 Sites Addition
Adding new sites can be used to improve the coverage, the capacity or both of them.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 67
8.6 Cell split
Assuming that the number of sites in a certain area is doubled, then the area covered by each
cell is half as large as previously. The added sites can be used for increasing coverage (for high
bit rate services at the cell border), capacity or both of them.
If the focus is on coverage, then the system with the added sites can offer full area coverage for
services using higher bit rates. This means that full area coverage for 64 kbps best effort services
can be expanded to full area coverage for 128 kbps best effort services. [33]
8.7 Layered Network
A layered network simply means that there exists different cell layers in the system, i.e. macro
layer, micro layer and perhaps also a pico layer. One simple approach of a layered network is to
have a macro layer and then deploy micro base stations in a separate band in the high traffic
demand areas.
One special example of a layered network is hot spot deployment. A hot spot is defined to be a
very limited area, typically a few blocks, with very high load. One example of handling local hot
spots is to add sites in an already used frequency band. [33]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 68
9. PRODUCT EVOLUTION
Additional features for boosting coverage as well as capacity will be introduced in the future.
Some of the important methods for improving the performance that various companies studying,
are listed below.
9.1 Adaptive Antenna
Adaptive antenna arrays is a technology that will boost both capacity and/or Coverage.
Investigations are ongoing with field trials among many other tests to evaluate this technique.
The adaptive antenna gives better performance in both up- and downlink. [8]
9.2 Interference Cancellation
Interference cancellation (IC or Multi-User Detection) is another promising technology, which
could improve up-link capacity. This will give a capacity benefit mainly in the up-link. [8]
9.3 Transmit Diversity
Transmit diversity has initially been studied in both ARIB and ETSI and the work is now
continued in 3GPP. It has been shown through simulations that transmit diversity provides a
significant gain in some scenarios. [8]
UMTS Radio Access Network Planning
School of Engineering Design & Technology 69
10. CONCLUSION & FUTURE WORK
Network Planning is a major task for operators. It is both time consuming and labor intensive
& it is expensive. Moreover, it is never ending process, which forces a new round of work with
each step in the network’s evolution and growth. Sometimes extra capacity is needed temporarily
in a certain place, and network planning is neded to boost the local capacity.
Tight and fast power control is one of the most important aspects in WCDMA, in particular on
the uplink. Without it, a single overpowered mobile could block a whole cell. A care needs to be
taken while degining a network
The quality of network planning process has a direct influence on the operator’s profits. Poor
planning results in a configuration in which some places are awash in used or underused capacity
and some areas may suffer from blocked calls because of the lack of adequate capacity. The
income flow will be smaller than it could be, some customers will be unhappy, and expensive
equipment may possibly be bought unnecessarily.
The detailed network planning phase includes the exact design of the radio network . Quite
often it is not possible to obtain the optimum cell site. The owner of the site may not want to sell
it, it may be unusable (e.g. in the middle of a pond) , or located in a restricted area.
Environmental and health issues can also have an impact . Base station towers in an open
country landscape may irritate some people. All these issues have to be taken into
considerations. The number of Handovers has to be minimised as it creates signalling traffic in
the network. This can be done for example with large macrocells. Sectorisation has to be
considered and implemented when required.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 70
This report has covered the main issues associated with coverage, breaking down link budget
along with the required specific parameters and providing some examples of expected coverage
ranges. Interference and all important fading margin have been discussed, including soft hand
over gains, Eb/No, and the processing gain. Both coverage and capacity with relation to link
budget have been revived. Further topic such as maximum allowed path loss calculation for
different bit rate have also been given.
In UMTS different services have different SNR requirement, which has made 3G network
planning a complex balancing act between all the variables in order to achieve the optimal
coverage, capacity and Quality of Service simultaneously. The obtained methods of effective 3G
planning may be considered as a basis for software design, in order to automate the planning
process.
FUTURE WORK
There are several investigations that could follow to develop the work carried out in this
project. An important extension could be the actual designing of software based on the methods
described in the report for calculation of RAN parameters and then simulating results on a
simulation software like OPNET.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 71
REFERENCES
[1] Chris Braithwaite & Mike Scott, ‘UMTS Network Planning and Development’, Design
and Implementation of the 3G CDMA Infrastructure, First edition, Newnesress 2004.
[2] Ajay Ranjan Mishra,’ Fundamentals of Cellular Network Planning and Optimisation:
2G. 2.5G. 3G. Evolution to 4G’, First Edition, John Wiley and sons Ltd. 2004.
[3] Qualcomm UMTS University Technology Journal [Online]
Available: http://www.umtsuniversity.com/umts/
[4] Journal on “UMTS Radio Interface System Planning and Optimization” from Bechtel
Telecommunications December 2002 by Esmael Dinan; Kurochkin; Sam Kettani.
[5] UMTS system Architecture [Online]
Available: http://www.ericsson.com/pl/technology/umts_struktura_sieci.shtml
[6] Overview of The Universal Mobile Telecommunication System [Online]
Available: http://www.umtsworld.com/technology/overview.htm
[7] UMTS elements description [Online]
Available:www.mpirical.com/companion/UMTS/Node_B.htm
[8] WCDMA Radio Network Design, Training LZU 108 5173 R4A, from Ericsson inc
Sweden [Online]
Available on payment: http://www.ericsson.com/.../pdf/training/product_information/
MI_material/32_1550-FAP130506_WCDMA_RAN P2_1.pdf
[9] Web ProForum Tutorials (http: //www.iec.org) The international Engineering
Consortium. [Online]
Available: http://alpha.ttt.bme.hu/~szaszi/mobil/9UMTS.PDF
[10] UMTS OTSR White paper from Nortel [Online]
Available:http://www.nortel.com/solutions/wireless/collateral/nn_110660.01-17-
05.pdf?NT_promo_T_ID=utranpdf_wls_docs_new
UMTS Radio Access Network Planning
School of Engineering Design & Technology 72
[11] 3G Technology Breakdown [Online]
Available: http://www.cellular-news.com/3G/3g_technology.shtml
[12] Heikki Kaaranen, Ari Ahtiainen, Lauri Laitinen, Siamak MAghian and Valtteri Niemi,
‘UMTS Networks’, Architecture, Mobility and Services, First Edition, John Wiley and
Sons Ltd., 2001.
[13] Krzysztof Welsolowski, ‘Mobile Communication Systems’, First Edition, John Wiley
and Sons Ltd., 2002.
[14] Wideband Code Division Multiple Access [Online]
Available: http://www.ericsson.com/technology/tech_articles/WCDMA.shtml
[15] Electronics & Communication Engineering Journal June 2000 “UMTS overview” by
K. W. Richardson.
[16] White Paper on “Basic Concepts of WCDMA Radio Access Network”. [Online] Available: http://www.ericsson.com/products/white_papers_pdf/e207_whitepaper_ny_k1.pdf
[17] Workshop proceedings “Cellular Networks - Past, Present and Future”2004-2005 by
Uday Raktale, School of Engineering, Design and Technology, University of Bradford
[18] Online Tutorial on “Cellular Communication Fundamentals” from International
Engineering Consortium [Online]
Available: http://www.iec.org/online/tutorials/cell_comm/
[19] Ph.D Thesis on “Intermodulation interference probabilities in cellular mobile radio
systems : development of prediction methods for - due to intermodulation originating in
both transmitters and receivers” by Hu Yim Fun 1987, University of Bradford.
[20] William C Y Lee, ‘Mobile Cellular Telecommunication’, Macgrawhill, Second Edition,
2002
[21] COST231, final report, 1999.
UMTS Radio Access Network Planning
School of Engineering Design & Technology 73
[22] PhD thesis on Radio Network Planning and Optimization for WCDMA by Jaana Lahio
July 2002, Helsinki University of Technology (Espoo, Finland)
[23] Public Land Mobile Network Network Cell Planning [Online]
Available: http://www.ericsson.com/support/telecom/part-d/d-10-4.shtml#d.10.4.1
[24] Air Interface Design and Optimization Services: Nominal Cell Planning [Online]
Available: http://www.grm33.dial.pipex.com/what_we_do/air-interface/ncp.htm
[25] Juha Korhonen, ‘Introduction to 3G Mobile Communication’, First Edition, Artech
House Publisher, Boston London., 2000
[26] Ph. D Thesis on “Quality of Service and Resource Management in UMTS”, by Frank Y.
Li Department of Telematics, Norwegian University of Science and Technology (NTNU)
[27] Publication Proceedings submitted on “Quality of Service Support in the UMTS
Terrestrial Radio Access Network” by Ana-Belén García, Manuel Alvarez-Campana,
Enrique Vázquez, Julio Berrocal of Departamento de Ingeniería de Sistemas Telemáticos,
Ciudad Universitaria, 28040 Madrid, Spain
[28] Samuel C. Yang, "CDMA RF System Engineering (Artech House Mobile
Communications Library)", Artech House Publishers, 01 May, 1998.
[29] Hari Holma and Toskala,’ WCDMA for UMTS’, Radio Access for third Generation
Mobile Communications, Second Edition, John Wiley and Sons Ltd., 2002.
[30] Aircom International “Applied UMTS Planning for Experienced Radio Engineers” 5
days training.
[31] Technical Journal by Y Jung H Jeon S Shin on “Coverage and capacity analysis in
cdma2000 network for voice and packet data services” of SK Telecom Network R&D
Center, Gyunggi, South Korea, Vehicular Technology Conference, 2001. VTC 2001 Fall.
IEEE VTS 54th
UMTS Radio Access Network Planning
School of Engineering Design & Technology 74
[32] Laiho, Wacker, Novosad “Radio Network Planning and Optimisation for UMTS”, First
edition, John Wiley and Sons Ltd., 2005
[33] Jonathan P Castro, ‘The UMTS Network and Radio Access Technology’, First Edition,
John Wiley and Sons Ltd., 2001
UMTS Radio Access Network Planning
School of Engineering Design & Technology 75
GLOSSARY:
2G the second (Cellular) generation
3G the third (cellular) generation
AuC authentication centre
BS base station
CDMA code division multiple access
Eb energy per bit
GGSN (Gateway GPRS [General Packet Radio System] Support Node)
SGSN Serving GRPS support node
GMSC gateway mobile service switching centre
GPRS general packet radio service
GSM global system for mobile communication
HLR home location register
Lu interface between RAN and node B
Kbps kilobits per second
Mcps mega chips per second
Node B base station in 3G
PSTN public –switched telephone network
PLMN public land mobile network
RAKE type of receiver utilizing multi-path propagation
RNC radio network controller
RNS radio network subsystem
RX receiving functionality/receiver
SIR signal to interference ratio
SNR signal to noise ratio
UE user equipment
UMTS universal mobile telephone system
UTRAN universal terrestrial radio access network
Uu Interface between the UE and Node – B
VLR visitor location register
W-CDMA wideband code division multiple access