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UTRAN DESIGN PROCESS

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CONTENTS

1.INTRODUCTION........................................................................................................................................................6

2.RADIO DESIGN PROCESS.......................................................................................................................................7

3.UTRAN DESIGN PROCESS....................................................................................................................................33

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Figures

FIGURE 1: UTRAN ARCHITECTURE......................................................................................................................7

FIGURE 2: FREQUENCY REUSE SCHEME...........................................................................................................8

FIGURE 3: CAPACITY AND COVERAGE TRADE-OFF......................................................................................9

FIGURE 4: SERVICES DIFFERENT FOOTPRINTS.............................................................................................12

FIGURE 5: CIRCUIT SWITCHED TRAFFIC MODELLING.......................................................................... ....12

FIGURE 6: POISSON LAW PDF AND CDF............................................................................................................14

FIGURE 7: CAPACITY ANALYSIS PROCESS......................................................................................................15

FIGURE 8: CAPACITY ANALYSIS RESULTS......................................................................................................15

FIGURE 9: TRAFFIC LOAD VS. INTERFERENCE LEVEL CURVE...............................................................17

FIGURE 10: DOWNLINK POLE CAPACITY EVALUATION ON TWO RINGS........................................20

FIGURE 11: DOWNLINK POLE CAPACITY EVALUATION ON UNIFORM USERSDISTRIBUTION

.........................................................................................................................................................................................20

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FIGURE 12: LINK BUDGET FLOW CHART........................................................................................................23

FIGURE 13: RADIO DESIGN PROCESS FLOWCHART.....................................................................................29

FIGURE 14: LAND USAGE DISTRIBUTION BY SUBSCRIBER TYPE...........................................................31

FIGURE 15: CELL NLOAD VS. CELL RADIUS....................................................................................................33

FIGURE 16 : UTRAN INTERFACES........................................................................................................................34

FIGURE 17 : IUB DIMENSIONING PROCESS......................................................................................................37

FIGURE 18 : RNC TRAFFIC REQUIREMENTS: MBPS VS ERLANG CURVE..............................................40

FIGURE 19 : RNC DIMENSIONING PROCESS....................................................................................................42

FIGURE 20 : CALCULATION OF #RNC2..............................................................................................................43

FIGURE 21 : VALIDATION OF RNC THROUGHPUT CONSTRAINT.............................................................44

FIGURE 22 : IU-CS AND IU-PS DIMENSIONING PROCESS......................................................................... ....45

Tables

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TABLE 1: LINK BUDGET PARAMETERS............................................................................................................26

TABLE 2: TYPICAL LINK BUDGET......................................................................................................................27

TABLE 3 : 3G TRAFFIC FORECASTS....................................................................................................................35

TABLE 4 : RNC PRODUCT SPECIFICATIONS................................................................................................ ....40

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1. INTRODUCTION

Cell planning for Code Division Multiple Access (CDMA) systems is quite complex as compared

with Time Division Multiple Access (TDMA) wireless networks. This is due to the fact that in CDMA,

the cell radius depends on the offered traffic. Taking the uplink as an example, as the number of

users or offered traffic load increases, the total noise at the Base Station increases. Interference

from other users in CDMA can be thought of as noise to a reference user. If the reference user is

already using the maximum allowed power on the uplink, too many users at the cell will cause the

reference users signal to be received with an insufficient margin above the noise level at the BaseStation. This phenomenon leads to the reference user no longer being covered by the Base

Station, or in essence, a reduction in the coverage area of a cell. This dependence of the cell

coverage radius on the loading can lead to an iterative procedure to balance the coverage radius

with the offered traffic.

For 3rd Generation (3G) systems, another complexity arises from the fact that a considerable

portion of the traffic is expected to be data traffic with varying bit rates. As the demanded data rate

increases, for a given transmission power, the coverage radius shrinks. If ubiquitous coverage for

the highest offered data rate is desired, power limitations must be imposed on lower data rate

services to match the lower coverage of high data rate services if all services are offered from the

same cell. An alternate strategy can be offering higher data rate services from micro and pico cells

and lower data rate services from macro cells.

For circuit-switched networks, a measure that is designed for is the blocking rate, which typically is

dealt with by using the Erlangs B formula. For packet-switched networks, measures of performance

are throughput and delay. Capacity planning for packet-switched traffic is another complexity

thrown in for 3rd Generation networks.

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In performing a design for a UMTS networks, all the problems mentioned are dealt with. All

assumptions that need to be made for performing a typical design are stated in this report. But the

real outcome of this document is to perform an equipment count of the UTRAN Network. An

overview of the network is shown below.

RNC

CoreNetwork

Iub

Iub

Iu-cs

Iu-cs

Iu-ps

Iu-ps

Iur

UE

Radio design UTRAN design

Node B

Node B RNC

UE

Figure 1: UTRAN architecture

2. RADIO DESIGN PROCESS

The purpose of this section is to describe in details the various steps that lead to dimension the air

interface pipe. The idea is to figure out the total number of sites (Node B) for the differentenvironment morphologies, which are required to handle the traffic .

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1.1 Problematic

1.1.1 W-CDMA specific parameters

1.1.1.1 Frequency planing :

In a CDMA mobile radio system, all users are active at the same time in the same frequency

band. Separation between the different users' information signals is assured by assigning to each

user a unique orthogonal code sequence. In a traditional cellular system (TDMA/FDMA),neighbouring cells do not use the frequencies used by the given cell (i.e., there is a spatial

separation between cells using the same frequencies). This is called the frequency reuse concept.

Because of the processing gain (spread spectrum), such spatial isolation is not needed in CDMA,

and a frequency reuse factor of one can be used. At a first glance, a frequency planing is not

mandatory in a W-CDMA system.

With CDMAWith CDMA

Figure 2: Frequency reuse scheme

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1.1.1.2 Trade-off between coverage and capacity :

The interference increases with the number of active users, so that the capacity is limited. This

limitation is a soft one; i.e. the system quality decreases continuously until it is no longer tolerable.

This leads to the phenomenon of the breathing cells: When the number of users gets too high,

the quality for the users at the edge of the cell gets so bad that their calls are dropped. This can be

interpreted as a shrinking of the cell. The call drops lead to a lower interference for the rest of the

users, so that the cell area grows again. This example illustrates the trade-off between capacity

and coverage, which exists in a CDMA network. Coverage and capacity are directly linked.

Figure 3: Capacity and coverage trade-off

The schematic above illustrates the cell shrinking when more and more users arrive in the cell.

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Coverage and capacity of a cell are a function of the received bit-energy-to-total-noise-plus-

interference-ratio Eb/(N0+I0) on each pixel of the cell for the downlink and in the base station for

the uplink. That means, that any parameter, which affects the signal level and/or the interference 1,

or reduces the Eb/(N0+I0) requirements2, influences coverage and capacity of the cell and of the

overall system. In the following chapters, these parameters and their impact on capacity and

coverage are described from the link budget point of view.

1.1.1.3 Soft handover zone :

Usually, a mobile station performs a handover when the signal strength of a neighbouring cell

exceeds the signal strength of the current cell with a given threshold. This is called hard handover.

Since in W-CDMA system, the neighbouring cell frequencies are the same as in the given cell,

this type of approach is called soft handover.

In soft handover position, a mobile station is connected to more than one base station

simultaneously. Soft handover is used in W-CDMA to reduce the interference into other cellsand to improve performance through macro diversity (all the path are combined together to get a

better quality of the signal). Softer handover is a soft handover between two sectors of a site.

1.1.1.4 Orthogonal codes :

Separation between the different users' information signals is assured by assigning to each user a

different broadband and time limited, user specific carrier signal, which is either derived from

orthogonal code sequences (e.g. Walsh sequences) or from quasi-orthogonal pseudo-noise (PN)

sequences. In the case of completely orthogonal3, synchronously transmitted and received signals,

the user signals can be separated perfectly. This is not possible in the Uplink, because users aretransmitting independently from different distances and with different time delays. But even in the

Downlink, where all signals originate from a single point and the parallel code channels can be

synchronised, orthogonality cannot be maintained completely due to multipath propagation.

1 interference=intracell interference and intercell interference2 interference = intracell interference and intercell interference3 Orthogonality of two functions g(t) and s(t) is given in the case, that their crosscorrelation function is equal tozero

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1.1.2 Multiservice Specific parameters

Contrary to second generation mobile radio systems, where one single type of quality criteria

designed for speech determines the radio design process, for UMTS a multitude of different

bearer services with different quality requirements have to be taken into account. The services are

characterised by parameters such as the bit-rate, the maximal delay, the tolerable maximal bit

error rate and the symmetry of the connection. Different settings have to be planned in order to

offer the required coverage and capacity for the different services. A traffic modelling process is

absolutely requested to provide a good accuracy in the network dimensioning.

The number of base stations has to be planned in order to handle the level of traffic that is

expected including the service mix. As for CDMA with conventional single user detection, the cell

range is traffic dependent, reliable traffic models will play an important role in the UTRA/FDD

radio 3design. It has to be noted once again, that the basic property of W-CDMA is the trade-off

between capacity and coverage. The less capacity is needed the larger the cell can be. The

symmetry of the connection has to be taken into account, too.

In a third generation mobile radio system, a multitude of services will be supported. As they are

handled differently, they all have different influences on capacity and coverage. In fact,coverage can explicitly only be given for ONE service, as it depends among others on the user bit

rate. However, it is possible to adjust all services to the same cell range by individually adjusting

the emitted power of each one, as described in the next chapters. In this way, one common cell

boundary is provided for all the services. The different footprints are represented on the schematic

below.

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Voice and LowData RateMediumData Rate

High Data Rate

Figure 4: Services different footprints

1.2 Multiservice traffic modelling :

In the third generation, the traffic modelling is the key issue in the dimensioning process because

the outcome of the whole modelling process has a direct impact on the site count. Indeed, the

number of simultaneous channels that is derived from the analysis is the main inputs of the link

budget analysis. When the traffic to handle is quite sufficient (cell loading of 30%), the slightest

variation of this parameter directly induces a modification of the cell radius. The main target is to

find out the peak of traffic during the busy hour. An accurate analysis of the traffic behaviour

proves to be indispensable. This analysis will be treated differently depending on the type ofservice, Real Time (RT) or Non Real Time (NRT).

1.2.1 Circuit switched services

Dimensioning capacity for Circuit-Switched services is straightforward given the offered load in

Erlangs and the blocking rate. The main idea is to derive from the traffic assumptions the offered

traffic at the busy hour per cell expressed in Erlang. This is obtained by making an assumption of

the cell radius (this parameter will be re-tuned by several iteration with the link budget). Then, for

these services an Erlang B table is used to determine the number of simultaneous channels

required during the busy hour for a given blocking rate.

Erlang B

Offered traffic

(Erl/cell) @ BH

Pblock

# Simultaneous activechannels

Figure 5: Circuit switched traffic modelling

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1.2.2 Packet switched services

Dimensioning for Packet-Switched (PS) services is somewhat elaborated as compared to

dimensioning of circuit-switched services because it requires knowledge of the nature of the traffic

that uses the services and the traffic modelling of that type of service. A packet traffic approach

is used to determine the number of simultaneous channels required to handle the PS traffic. This

number of channels represents in fact the peak of traffic during the busy hour. Similarly to the CS

services, the first idea is to derive from the traffic assumptions the offered traffic during the busy

hour per cell expressed in kbits. Each service is treated independently because they may havedifferent grade of service or asymmetry.

The number of channels for packet switched services is calculated by considering an observation

window of duration the service acceptable delay, which will be called D in the following and which

is expressed in seconds. Dis typically equal to 0.5s.

A step-by-step procedure is as follows:

i. An assumption is made on the nature of the traffic (Web usage, Smart shopping,

Shopping on line, file transfer, etc). Based on the typical models given in UMTS 30.03, atypical packet length in terms of bits is obtained. For instance L=3840 bits or 10ms.

ii. From the total busy hour traffic for a given reference area, the mean offered data

rate M for the reference area in kbps is then calculated. This is translated into a mean packet

arrival P rate (dividing by the typical packet length). The formula used is: P=(MxD)/L

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iii. Assuming a Poisson packet arrival process f rom all users, with a mean P

calculated in the previous step, the probability density function as well as the cumulative

density function can be obtained. The peak packet arrival rate H at 95% time probability is

obtained (cf. the curve below).

DL / Poisson Distribution, T=0.5, Lambda=17.25

0

0.008

0.016

0.024

0.032

0.04

0.048

0.056

0.064

0.072

0.08

0.088

0.096

0.104

2 3 4 5 6 7 8 9 10 1 1 12 1 3 14 1 5 16 1 7 18 1 9 20 21 2 2 23 2 4 25 2 6 27 2 8 29 30 3 1 32

k Arrivals in T sec

P(kArrivalsinTsec)[PDF]

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

P(k) (PDF)

CDF

Figure 6: Poisson law pdf and cdf

iv. Using the higher, 95% time probability packet arrival rate, which is translated

back into kbps (by applying the typical packet length : H(kbps)=H(kbits in D sec)/D), the

number of channels C necessary is calculated by dividing by the service bearer rate R. Forinstance, C=H(kbps)/R. The number of channels is not rounded off to the nearest integer;

instead, the activity factor is kept at 1.

To sum up the previous process, the following formula can be derived:

= %95,

LengthPacket*DelayService*

delayService

1*

ratebitService

1channelsrequiredofNumber

mcdfP

Where cdfP(x,y) represents the point of probability y on the cdf associated to the Poisson law of

mean x, and where m represents the mean offered data rate in kbps.

1.2.3 Capacity analysis applied for the dimensioning

The very first step of estimating the capacity in a cell consists of assuming a typical coverage

radius Ro and deriving a reference cell area. The second step consists in calculating per service

at the busy hour the offered traffic in the reference area per carrier. Afterwards, the number of

required channels for CS and PS services are determined for each link - by using the

dimensioning rules described in the section above - and therefore the total number of

simultaneous channels is found (NT_UL and NT_DL). The flowchart below explains this capacity

analysis process.

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GENERIC INPUT

Cell range

Number of carrier/cell

OFFERED CAPACITY

Total Offered Capacity in the cell (CS

in Erl/cell, PS in pkts/sec/cell)

CHANNELS REQUIRED

Max number of simultaneous Channels @ BH

SERVICES

Service Bit Rate

Activity FactorBlocking Probability/GoS

Maximum Allowable DelayEffective Typical Call Length

(CS in sec, PS Data in kbits)

TRAFFIC

Traffic/cell/carrier @ BH (Mbits)

CS:

Erlang

Blocking Prob.

PS:

Poisson

CS: Bit Rate

PS: Packet Length

CAPACITY ANALYSIS

MARKETING !

Figure 7: Capacity analysis process

1.2.4 Typical capacity analysis

A typical result of the capacity analysis is shown below. The last column shows the number of

simultaneous channels requested to handle the traffic. There are three circuits switched services

and two packets switched services. The rules described above have been applied (Erlang B and

Poisson approach).

Nb %

Voice 532.8 120 0.6 12.1319 19 64%

Video conferencing 201.9 300 1 0.8764 4 14%

video game 193.2 300 1 0.3727 3 10%

Info push 13.1 3840 1 0.9467 2.016 7%

Smart shoping / Online advertising 1708.7 3840 1 123.6010923 1.480 5%

29.496 100.00%

22

Traffic per cell

per carrier @

BH (Mbits)

0.47 0.144 3 67

Number of

cell per

morpho

Number of

sites per

morpho

Total number of required channels

Activity

Factor

DOWNLINK

Services

Cell

radius

(km)

Cell Area

(sqkm)

Number of

carrier per cell

Effective Typical

Call Length (CS

in sec, PS Data in

kbits)

Max number of

simultaneous Channels

@ BH

Total Offered

Capacity in the cell

(CS in Erl/cell, PS in

pkts/sec/cell)

Figure 8: Capacity analysis results

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1.3 Multiservice link budget

The link budget is a key element in the dimensioning process. It is used to derive the path loss

and the cell radius. It has to be admitted that in W-CDMA, the link budget is much more

elaborated than in GSM since it has to integrate all the complexity of a Multiservice environment

and to face a new technology with its own specific parameters. This section introduces the

concept implemented in the tool ILBT and which allows to analyse and to bring a solution for the

Uplink and Downlink.

For the dimensioning, a completely homogenous network with a hexagonal cell structure, a

homogenous morphostructure, topographical environment and user distribution are assumed.

Therefore, one cell is representative for the whole network, meaning that all parameters are valid

for all cells.

1.3.1 Uplink analysis

A link budget is conventionally performed for one mobile located at the edge of the cell and

therefore transmitting at maximal power. Since in a multiservice environment, there are different

types of mobiles with different service characteristics, the link budget has to be elaborated for one

mobile of each service type.

The main target of the uplink is to figure out the increase of the interference level due to the traffic

available in the cell. The curve below shows the relation between the traffic load and the

interference level. The level of interference diverges when the number of mobile is close to the

pole capacity.

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Interference curve

0.00

5.00

10.00

15.00

20.00

25.00

0.00 20.00 40.00 60.00 80.00 100.00

Capacity

Noiserise(d

Figure 9: Traffic load vs. interference level curve

The interference in a cell depends on the thermal noise, on narrow band and wide band

interference from another system, other users in the same cell and users from all the others cells.The intra-cell interference perceived by a mobile in the uplink is independent of the location of the

other mobiles thanks to an effective power control, so that for the uplink link budget elaboration

the mobile distribution is not relevant.

Once the level of interference has been calculated, the next step is to calculate the maximum

allowable path loss (MAPL) in order to derive the cell radius.

For a given cell load, the uplink maximal allowable pathloss for a service i depends on its Eb/N0

requirements, its user bit rate and the maximal mobile transmitting power for this service. This

means that in general, one will obtain different uplink coverage ranges for the different servicetypes.

By adjusting the mobile transmitting power, different coverage scenarios can be achieved. Service

specific gains, losses and margins have to be integrated if not all mobiles are suffering from the

same losses and taking advantage of the same gains, and/or if different margins are applied to

different services. This can be the case e.g. for soft handover gains as well as body losses and

even penetration margins.

The strategy adopted in the dimensioning of the uplink is to provide one common cell

boundary. Hence depending on the type of service proposed and the volume of traffic

associated, the idea is to find the limiting service (i.e. the service which reach its maximum power

capabilities) and then match all the other UE power to this service limiting cell range.

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1.3.2 Downlink analysis

One of the main target of the downlink analysis consists in finding the maximum number of mobile

that can be connected to the base station with a good quality of service. However, contrary to the

uplink analysis, for the downlink the position of the users has to be known, since the distance

from the base station impacts the power share allocated to the mobile and hence both intracell

and extracell interference.

The results of the downlink analysis depend on the location of the users, hence there is no uniquesolution. Intuitively, one would assume a uniform distribution of the users within the cells.

However, this approach can not be treated in a simple link budget analysis , since the

pathloss differences between all mobiles would create a huge equation system, which is only

solvable using an adequate tool. Therefore the nearest approximation of the real capacity of a cell

can be done through several scenarios:

All users are located at the cell edge of its service area

The analysis is performed for tow or three cell radii with the users distributed on each

circle

The analysis is done for fifty rings and with a uniform users distribution in each ring.

Those different scenarios can lead to different set of results going from the most optimistic to the

most pessimistic. The idea is obviously to figure out the most realistic case in terms of

interference level assessment.

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1.3.2.1 All users located at the cell edge :

The scenario that can be computed in a simple link budget is the one where all mobiles are

located at the same distance from the base station, i.e. the cell edge. The main point that leads to

a such a worst case analysis is due to the interference calculation. In order to determine the

interference perceived by a given mobile i, the contribution of each active connection within the

cell to the total received level at the location of mobile i as well as the extracell interference has to

be known. Lets call the mobile for which the link budget is performed mobile 1. If all users are

located at the same distance from the base station as mobile 1, and only then, the mobile 1receives from all other connections i (for i 1) the same level Si as the corresponding mobile i

itself. This means, the input Eb/N0 values for all services can be directly applied to calculate the

interference perceived by mobile 1, without introducing pathloss differences. Another advantage is

that the interference factor f which is actually location dependent can be treated as a constant,

since only one location distance from the base station occurs.

This scenario corresponds to the worst case since the Node B will transmit for each link a very

high level of power. As the maximum power of one base station is limited at a given level (i.e.

43dBm), the maximum number of mobile will be affected by the power allocated to each link. In

this scenario the maximum capacity reached will be quite pessimistic.

1.3.2.2 Two and three cell radii :

This scenario is more realistic than the previous one because it gives a better idea of the level of

interference in the cell. The analysis relies on several cell radii (two to three) with all users

dispatched on this different cell edge. The idea is to calculate the interference level due to the

users distributed on the two cell radii. The schematic below shows the analysis for two cell radii:

one inner cell edge and one outer cell edge.

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30% of the mobile are at the cell edge

Inner cell radius =50% of the cell edge

Cell edge

Inner cell radius

Figure 10: Downlink pole capacity evaluation on two rings

For the analysis, the percentage of mobile dispatched on each radius can be modified. As a

reference 30% of mobile can be put on the cell edge and 70% on the inner cell. The ratio of

between the two radii can also be changed.

To provide the interference degradation, one needs to get a set of values for the parameter f

(outer cell/Inner cell), but this is fully dependent on the users distribution. Hence several Monte-

Carlo simulations performed with several users distribution are required to have a set of value

available.

This approach is more realistic and can be optimised by using several ratios (Outer/Inner cell

radius and distribution of mobile).

1.3.2.3 Uniform users distribution :

This is the better study but it requires several analysis of the capacity with different users

distribution. The main idea is to compute within a given cell range, fifty scenarios of capacity

analysis. This is done by taking fifty rings that cover the total cell area. Within each ring, the

capacity analysis is done (in terms of maximum number of mobile) with a uniform users

distribution. The schematic below shows the principle of the analysis.

All users distributed

uniformly inside the ring

50 rings from the

BTS to the cell edge

Node B

Cell edge

R

Figure 11: Downlink pole capacity evaluation on uniform usersdistribution

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Within each ring the assessment of the capacity is performed by calculating the level of

interference and the power allocated to each mobile in order to derive (knowing the maximum

transmitted power of the Node B) the maximum number of mobile in this given rings. This number

will be high when the rings are close to the Node B and conversely will be low at the cell edge.

Then an average number of mobile in the cell is deduced. This approach is the most realistic but

require accurate Monte-Carlo simulations for the factor f.

Whatever the scenario selected, there is another important step which consists in calculating the

downlink pole capacity in the multi-service environment. The pole capacity in the downlink

corresponds to the theoretical maximum number of mobile for an infinite transmitted power of the

BTS. In reality the limitation will be made by the maximum transmitted power of the Node B

before being limited by the interference level. This limitation gives in fact the downlink loading

factor since the loading represents the ratio between the maximum capacity in the cell and the

pole capacity.

1.3.3 Link budget flowchart

The following flowchart shows the various steps that lead to derive the cell radius. The number of

simultaneous active channels per service has to be known (NTULand NTDL). It is provided by the

capacity analysis section.

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UL+DL / Pole capacity calculation

UL+DL / loading calculation

UL+DL / RX sensitivity

calculation

UL / Noise rise calculation

UL / MAPL calculation

UL / Cell radius calculation

UL / UE transmitted power

calculation

Equalize the UL and DL MAPL

DL MAPL: =UL MAPL + margin

DL / transmit power calculation

(TX _DL) + P synch + P pilot

TX_DL+Psynch+

Ppilot


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Figure 12: Link budget flow chart

The next step consists in calculating the pole capacities for both links. Since the loading factor of

one link constitutes a percentage of its pole capacity, the uplink and downlink loading (DL, UL )

can be worked out by using NTULand NTDL from previous step.

From now on, the calculation of the receiver sensitivity for both link can be done. Then the noise

rise and the maximal allowable pathloss (MAPL) calculation for the uplink and for the different

service k can be accomplished. In the full coverage scenario, the MAPL should be the same for all

the services, because the mobile transmitting powers have been fixed to fulfil the condition of

same service radii for all services, which are directly related to the MAPL by the propagation

model. Hence, the calculation of the mobiles transmitted power per service is needed.

In order to balance uplink and downlink, the uplink MAPL results are taken as input for the

downlink budget, adding for the PCCPCH and the synchronisation channel a certain margin M (in

dB) in order to assure that the pilot coverage exceeds a little bit the traffic channel coverage for

assuring the possibility of soft handover. Fixing the MAPL derives the downlink transmission

power share Ti,k for each connection i of service k. The power share per service can be calculated

by multiplying by the number of channels of the service k: T k=Ti,k Nk , the total transmission power

Ttot can be derived by summing up all service power shares. It has to be assured that this sum of

all output powers doesnt exceed the maximal downlink transmission power (which is represented

in the link budget template). If the latter occurs, the system is downlink limited. Two possible

solutions are considered : the first one is to add a carrierto decrease the capacity handle by one

cell, and the second one is to reduce the uplink mobile powers in order to decrease the MAPL.

A selection box is insert in the process to choose according to the deployment strategy and the

availability of the spectrum the best solution for the design. One may observe on the flowchart

that the adding of carrier will directly impact the capacity analysis and not directly the link budget.

1.3.4 Main parameters used in the link budget

The main parameters used in the link budget are defined hereafter:

Service related

inputs

Number of active

channels per carrierk

number of active channels needed for service k within

one cell

Bit rates RkUL / Rk

DL Uplink / downlink user bit rate of service type k (to be

given for all services k)

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Required (Eb/N0)kUL /

(Eb/N0)kDL

Min Eb/N0 required at user level for good reception of

service type k in uplink/downlink

Activity factors kUL /

kDLFraction of session time in which user of service type

k is transmitting in uplink / downlink (to be derived for

all services k by an according traffic model)

W-CDMA related

inputs

Bandwidth W Bandwidth of the W-CDMA channel (the occupied

bandwidth for one carrier is theoretically equal to the

chiprate Rc)

Loading factor xUL / xDL uplink and downlink load of the cell. The values

express percentages of the uplink and downlink pole

capacity, which represents the theoretical maximum

number of users.

fUL=(Ioc/It)UL

fDL=(Ioc/It)DL

Ratio between interference generated in other cells

and the total interference (=total received power)

generated in the same cell. It has to be noted, that

these values constitute in fact output values of theplanning process, measured in an implemented

network. For the uplink, it is in general different for the

different base stations. For the downlink, it is location

dependent. In order to perform the dimensioning,

typical values has to be taken, derived from

simulations and experience.

Orthogonality factor Describes the downlink non-orthogonality due to

multipath propagation. An orthogonality factor of zero

corresponds to a perfectly orthogonal downlink, whilea factor of one represents a completely non-

orthogonal downlink

Required SCH Ec/It Min Ec/It required for the synchronisation channel

(downlink)

Required PCCPCH

Eb/N0

Min Eb/N0 required for the pilot (downlink)

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Chip rate Rc The system chip rate is the same for uplink and

downlink. However, the effective chip rate for the

downlink is twice the system chip rate, since both I

and Q branch are available for data transfer

DL cell inner radius /

cell edge ratio

Ratio between the inner cell radius and the cell edge

(for the downlink analysis)

DL ratio of mobiles at

cell edge

Percentage of mobile on the cell edge (for the

downlink analysis)

Synchronisation

channels activityfactor

The Eb/No values are defined for a frame duration of

10ms but the synchronisation channel is active onlyduring a portion of this time. The typical activity factor

is 10%.

Gains, Losses and

Margins

Shadowing&Rayleigh

margin

Margin taken to compensate these two effects.

Penetration margin indicates outdoor, incar, indoor or deep indoor coverage

Body loss It is considered that there is no body loss with a

mobile being held away from the body. Therefore a

margin of 3dB is taken only for speech application

and 0dB for all the other services.

Soft Handover gain When a mobile is in connection with several cells, there is a

gain mainly due to the MRC scheme implemented in the

downlink. Hence a value of 2.5dB is taken for the DL. For

the uplink there is no gain since selection diversity is

implemented in the RNC.

Hardware related

inputs

Cable, connector &

combiner losses

3dB is taken

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Tx Node B Antenna

Gain

17dBi for a tri-sectored site and 22dBi for an Hexa-

sectored site

TX UE Antenna Gain 0dBi

Receiver noise figure

NFUL / NFDL

5dB for the Node B and 9 dB for the UE

Max Tx power

TkUL /Ttot

DL

Uplink: Maximal mobile power (for service k) to be fixed

according to dimensioning (depend on service class 21dBm

or 24dBm)

Downlink: Maximal total transmission power (43dBm)

Table 1: Link budget parameters

1.3.5 Typical link budget

A typical link budget for a dense urban environment with five different service types is shown

below. One may observe that the limiting service in terms of coverage is the LCD384K since it

reach its maximum TX power capabilities before all the others services (+24dBm).

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LBA Parameters Units

5 different service types Voice LCD 64 LCD 384 UDD 64 UDD 144 Voice LCD 64 LCD 384 UDD 64 UDD 144

Ratio channels / total channels 56% 11% 11% 11% 11% 56% 11% 11% 11% 11%

Activity Factor 60% 100% 100% 100% 100% 60% 100% 100% 100% 100%

f (Ioc/Io) at cell edge

f (Ioc/Io) at cell inner edge

Downlink orthogonality factor

Effective Chip Rate Kchps

PCCPCH bit Rate Kbps

Service bit Rate Kbps 8 64 384 64 144 8 64 384 64 144

Processing Gain 480 60 10 60 26.666667 480 60 10 60 26.666667

Target Eb/No dB 4.1999998 2 0.2 0.8 0.1 4 3 2.5 1.3 0.5999999

Required SCH Ec/It dB

Required PCCPCH Eb/No dB

Cable, conn. & combiner losses dB

TX Antenna Gain dB

Downlink Tx power per service dBm 29.0 27.0 34.0 25.3 28.1

SCH Tx power dBm

PCCPCH Tx power dBm

Total TX power dBm 14.6 18.3 24.0 17.2 19.9

Total TX EIRP dBm 14.6 18.3 24.0 17.2 19.9

RX Antenna Gain dB

Cable and Connector Losses dB

Receiver Noise Figure dB

Thermal Noise dBm/Hz

Interference Degradation UL & DL Cell edge dB 1.7 1.6 1.3 1.6 1.6

Interference Degradation DL inner edge dB

Service Rx sensitivity dBm -125.8 -118.9 -113.0 -120.1 -117.3 -122.0 -114.0 -107.0 -115.7 -112.9

Synchro Rx sensitivity dBm

Pilot Rx sensitivity dBm

Log Normal Fade Margin dB

Penetration margin dB 15 15 15 15 15 15 15 15 15 15

Body loss dB 3 0 0 0 0 3 0 0 0 0

Soft Handoff Gain dB 0 0 0 0 0 2.5 2.5 2.5 2.5 2.5

Maximum Allowable Path Loss Services dB

MAPL Pilot & Synch channels DL dB

MAPL inner edge dB

Cell inner radius km

Cell range km

Site area km2

Loading Factor

Pole Capacity

Number of active channels per service 4.997065 0.999413 0.999413 0.999413 0.999 413 4.997065 0.999413 0.999413 0.99 9413 0.999413

Total number of active channels in the cell

0.11

0.4

3840 3840

32

38.7

52.7

Tx data

0 3

0 17

30.7

-15

7

129.6

-113.0

7.1 2

Gains & margins

Path loss & cell radius

127.6 127.6

21.4

-114.2

-174 -174

27.36 10.51

9 9

117.0

32.9% 85.6%

0.21

0.42

0.35

W-CDMA specific parameters

9.3

31.9

17 0

3 0

Rx data

5 9

Uplink Downlink

0.7 1.2

W-CDMA specific inputs

Table 2: Typical link budget

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1.4 Radio design process

1.4.1 Process description

Before starting the dimensioning process, the choice of the coverage scenario is indispensable. In

the following, a full coverage scenario has been considered, meaning that the dimensioning aim

consists of providing all services within the whole area to be covered. Therefore, by adjusting the

ratio of mobile transmitting powers for all pairs of services accordingly, a homogenous coverage

can be achieved. The absolute power values can be fixed by choosing the highest possible powerfulfilling the ratio constraint and being below the maximum possible mobile power of this service.

This can be seen in the example link budget in previous section, which has been performed for a

full coverage scenario.

The radio design process is based on a link budget approach and consists of two major stages,

capacity analysis and link budget analysis. The two stages are inter-dependent; meaning that

each stage requires input from the other. The capacity planning process requires an estimate of

the coverage radius of the cell, and the link budget requires the amount of loading produced by

the traffic within a cells coverage area. This inter-dependence leads to an iterative process that

converges to a solution in the link budget .

1.4.2 Radio design process flowchart

The following chart shows the overall process.

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LINK BUDGET ANALYSIS

(gives the cell radius Rnew)

Check capacity

UL / Reduce max mobile transmit

power

Calculate the cell area

Default values : Ro and Co

CELL

COUNT

Ro = typical cell radius for a given environment

Co = number of carrier (one to start the process)

Add an other carrier

Add a

carrier or

decrease

power?

CAPACITY ANALYSIS

(done for a cell radius Rc)

Check Cell radius

Rc=Rnew ?

Take the new cell radius and redo

the capacity analysis process

Rc:=Rnew

Capacity non OK

Capacity OK

NO

YES

Selection box (depends on

the deployment strategy)

Figure 13: Radio design process flowchart

The very first step consists of assuming a typical coverage radius Ro and deriving a reference cell

area. Then the capacity analysis and the link budget analysis give a first set of results: If the

capacity does not respect the criteria (i.e. the loading factor is higher than the maximum loading

factor acceptable) then the solution is to either add a carrier or reduce the UE transmitted power.

If the capacity fulfil the requirements then the final step consists in deriving the cell radius. As it

was stated before, the process should converge to a solution when the cell radius taken to process

the capacity analysis is the same than the one provided by the link budget analysis. If it is not the

case, the action to complete is to set Rc to Rnew - which will give a new reference area - and to

redo the whole process.

1.5 Inputs required for the design

1.5.1 Service related inputs

In 3G network there is several kind of services available on the air interface. They can be divided

in two families: the non real time services (NRT) and the real time services (RT. To perform an

accurate dimensioning one need to know the nature and the behaviour of the traffic. In this way

some parameters are mandatory (i.e. traffic forecast) and some others can be assumed. The

following tables show the typical inputs needed to do a preliminary network design.

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The first set of inputs needed is related to the traffic forecast for each service at the busy

hour for the roll out plan. This can be expressed through various forms. For instance the total

number of subscriber with the associated traffic forecast per subscriber. Or it can also be

directly the total traffic forecast at the busy hour.

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Speech Mbits

Switched Data Mbits

I nterac ti ve Mul ti me di a Mbi ts

Simple Messaging Mbits

Medium Multimedia Mbits

High Multimedia Mbits

Service Demand - 3G Terminals UnitTRAFFIC PROJECTION @ BH

Notice : The volume for the circuit switched services can be expressed in Erlang.

The asymmetry of the traffic is required to start the dimensioning process, it will allow to

calculate the cell loading for each link. This asymmetry depends on the type of service (50%

for video conferencing, 10% for web browsing application, etc).

The service bit rate and the activity factorare also requested.

Grade of service: one reason for an unsuccess call is the situation that a subscriber finds all

radio channels occupied. The probability for that case is called the blocking probability. For

the circuit switched services, a typical value is between 1% and 5% blocking probabilities.

For packet switched service measure of performance are throughput and delay.

Service class: Two class of power were defined in the standard (release 99): Class 3

(24dBm) and class 4 (21dBm). This information will be helpful in the link budget analysis.

1.5.2 Coverage related inputs

The Quality of service: the received field strength is subject to statistical variations (Raleigh

fading, lognormal fading) and interference. It is not possible, in that condition, to achieve a

100% surface coverage probability for sufficient service quality in the service area. Therefore

a reasonable value should specified for that probability of sufficient service. The following

probability is defined

Pcov :Coverage probability = Probability (field strength > threshold)

The threshold value is the minimum field level that allows a call to be performed while in

operational conditions. Usually, a surface coverage probability in the range of 90 % to 99 % is

required. In a first approach, Pcov is considered constant. As for instance, the surface

coverage probability could vary depending on the planning area (land usage) or the coverage

probability may also be time dependent.

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Maps & subscribers distribution: The subscribers area distribution is the mapping of the

subscribers within define areas of a city. The mains define areas are as follows :

business area,

industrial area,

VIP area,

high level residence area,

medium level residence area,

low level residence area,

tourist area,

commercial area.

For the cities or areas to cover, one needs to provide topographical maps with indication of

subscribers distribution drawn by hands. The map below depicts the required information.

Medium level residence area

High level residence area

Business area

VIP residence area

Commercial area

Tourist area

Figure 14: Land usage distribution by subscriber type

The coverage service margin is the average loss for the radio signal due to the indoor or the

in car penetration. As an example, a value of 20dB can be used for the dense urban

environment and 15dB for an urban area.

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1.5.3 Bandwidth related inputs

The bandwidth allocation as well as the number of carrier available has a direct impact on the

dimensioning. Hence for the capacity analysis section the maximum number of carrier is required

1.6 Deployment strategy

Further deployment strategy can be applied depending on many factors such as the operators

business plan, the number of carrier available, or if there is an existing GSM network, etc. Thetarget of this chapter is therefore to give only one of the dominant trend in the deployment of a

typical network.

The main problem that exists in deploying a 3G network is related to the cell breathing effect i.e.

the relation between coverage and capacity. This phenomenon induces to keep in mind that when

the traffic increase holes in the coverage will unfortunately appear. It might be obvious that the

strategy adopted for the deployment should be mainly focused on in this constraint. The graph

below represents the relation between the loading factor and the cell radius.

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0

0.2

0.4

0.6

0.8

1

LOADING

CELL RADIUS

WORKING ZONE

Add a T/RX

Unloaded cell

Figure 15: Cell nload vs. cell radius

One solution would be to build the network in a dense way by anticipating the traffic growth (one to

two years in the traffic roll out forecast). During the first one or two years no cell breathing effect

will appear due to the power control (all the cells will match together in such a way that the cell

radius of each cell will equal the initial cell radius). When holes in the coverage will appear it is

recommended to add another T/RX. This will immediately increase the cell radius. If the loading

keep going to increase, traffic will not be supported and the strategy adopted will be to add other

sites.

3. UTRAN DESIGN PROCESS

1.7 INTRODUCTION

This document describes the RNC and UTRAN interfaces dimensioning process applied in

performing pre-sale designs of UMTS networks.

The methodology is applied for a given service traffic mix and involves the following calculations:

dimensioning of Iub interface between Node B and RNC;

calculation of number of RNCs;

dimensioning of Iu-cs and Iu-ps interfaces between RNC and core network;

dimensioning of Iur interface between RNCs.

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Chapters 3 to 9 explain the dimensioning process in details, so as to allow the reader to understand

the procedure and apply it in answering UMTS RFI/RFQ. Moreover, several annexes are provided

at the end of the document. In Annex A some dimensioning models are reported; in Annex B the

calculation of overheads margins is explained; Annex C reports the Alcatel's traffic forecasts, as

used in building the UMTS business case; finally, in Annex D and Annex E an example of

dimensioning the Iub interface, number of RNC, Iu and Iur interfaces is provided.

Node BIub

u

to CN

Uu

source traffic

softer HO

soft HO

Iur

RNC

RNC

UE

Node B

Node B

Figure 16 : UTRAN interfaces

1.8 Required input

The following minimum information is needed for the UTRAN design process:

Number of Nodes B

The number of Nodes B is normally provided by the Radio Design Process, for a given clutter

area and year.

3G services and traffic forecasts

Traffic forecasts for reference area at the BH.

The information provided should be as detailed as possible, with a list of services andparameters such as the ones reported in the following table.

For each clutter area:Dense Urban, Urban, Suburban, Rural, Roads

For each year:Year1, Year2, Year3, etc.

Uplink Downlink

For each type of service:speech,CS data,WWW,etc.

Number of subscribers per sqkm # #

Average/Peak User Bit Rates kbps Kbps

Number of Sessions per user @ BH # #

Volume of data per session per sub kbits Kbits

Average Session Length sec Sec

Activity Factor (optional) # #

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Table 3 : 3G traffic forecasts

However, if the parameters are not directly usable, a pre-elaboration is needed to derive the

required inputs.

Number of 3G users

The number of 3G users is normally provided by the Operator.

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1.9 Iub dimensioning

1.9.1 Introduction

The Iub interface shall be dimensioned by taking into account the site configuration, the service

traffic mix and the transmission topology. As previously mentioned, the multiservice environment

plays an important role in the dimensioning process. From the average traffic per Node B, a total

traffic must be derived, by considering the service mix statistics, the soft handover traffic, and

overheads, signalling and O&M contributions.

The average traffic per Node B is known from the Operator's requirements and the Radio Design

Process. Usually, the average traffic per Node B is provided at the BH as:

Total Erlang value for the aggregate voice and CS data;

Total kbps value for the aggregate PS data.

The Iub is dimensioned by calculating the total traffic per Node B, which takes into account the

service parameters, the soft handover traffic, the peak traffic calculation, the overheads, signalling

and O&M margins.

Therefore, in order to determine the total traffic, the following steps are performed:

i. the peak aggregate traffic mix is calculated by means of an analytical approach, taking into

account the service parameters, grouped into the Traffic Table: Ni, Rbi, Ti, i,AFi.

ii. then, overheads, signalling and O&M margins are added.

Note that the ratio Peak traffic/Average traffic represents the Burstiness Factor.

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Traffic TablePeak

Traffic

(RUBIS)

Signalling

factor

Total

Throughput

O&M

Margin

Average

Traffic

ATM

Overheads

factor

Figure 17 : Iub dimensioning process

1.9.2 Peak traffic per Node B (RUBIS tool)

The methodology consists in calculating the overall pdf(R) and cdf(R), where Ris the aggregate bit

rate, and determining the outage probability for each value of user bit rate. Thus a set of outage

probabilities is obtained, one for each user bit rate Rb : the channel capacity is dimensioned by

fixing a common outage value Pb0 for each service i.

This analytical approach has been implemented into the tool RUBIS [1]. The tool determines theprobability density function of an aggregate bit rate, where each service icomposing the traffic mix

is described by the following parameters:

User Bit Rate (Rbi)

Number of subscribers per Node B (Ni), taking into account of both direct and soft

handover traffic

Session Length (Ti)

Session Interarrival Time (1/i)

Activity Factor (AFi)

Then by assuming that the traffic sources follow a binomial law, the pdf and cdf of the aggregate bit

rate can be derived.

1.9.3 Total traffic on Iub

Having calculated the peak traffic per Node B, in order to dimension the Iub interface it is necessary

to take into account overheads and signalling factors. This is done by means of margins. The Total

Traffic at the Iub interface is then derived, which takes into account the user (direct) traffic, soft

handover traffic, burstiness factor (peak traffic), overheads and signalling margins.

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The total traffic per Node B is calculated from the peak traffic by adding the following parameters:

Overhead margin: 1.4 (40% of Iub peak user traffic)

Signalling margin: 1.2 (20% of Iub peak user traffic)

O&M margin: 1.1 (10% of Iub peak user traffic)

Thus, the total traffic on the Iub interface is determined as follow:

Total Traffic = Peak Traffic + Overhead + Signalling + O&M

= Average Traffic * Burstiness * (1 + 40% + 20% + 10%)

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1.10 RNC dimensioning

1.10.1 Introduction

The RNC dimensioning process is based on Alcatel's RNC product specifications.

As reported in the section 1.10.2, four parameters characterized Alcatel's RNC:

Iub connectivity;

Iu and Iur connectivity;

Throughput (both CS and PS);

The number of node-B managed by a RNC

Therefore, in order to determined the number of RNCs necessary in the target area, the following

input is necessary:

Total number of node-B

Average traffic forecasts, expressed in Erlang (CS) and Mbps (PS).

1.10.2 RNC product specifications

The following table details the capacity and connectivity constraints of Alcatel's RNC, for different

releases.

2001 (R1) 2003 2005

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User Throughput

CS data (Erlang) 3000 9000 15000

PS data (Mbps) 60 180 300

Iu and Iur Connectivity

#STM-1 for Iu and Iur 2 4 6

Iub Connectivity

#STM-1 for Iub 3 7 14

#Node B 256 1000 2000

Table 4 : RNC product specifications

The RNC capabilities given here take into account only the user traffic. CS data incorporate both

voice and circuit switched data services which bit rate is less or equal to 64kbps. PS dataincorporates packet switched services and circuit switced services which bit rate is more than 64

kbps.

The capacity figures are nominal values taken from PS traffic vs. CS traffic curves such as the

following. These curves, together with the #Node B constraint, are used in the RNC dimensioning

process.

0

20

40

60

80100

120

0 1000 2000 3000 4000 5000Erlang

Mbps

Figure 18 : RNC traffic requirements: Mbps vs Erlang curve

1.10.3 General process

The four RNC product constraints influencing the RNC dimensioning are:

1. the maximum number of node-B that a RNC can manage,

2. the maximum throughput supported by one RNC,

3. the maximum number of connection supported by one RNC on Iub interfaces,

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4. the maximum number of connection supported by one RNC on Iu and Iur interfaces.

The two first constraints give two different numbers of required RNC: #RNC1, #RNC2. The final one

is the maximum of the two. Then as the Iub and Iu/Iur connectivity constraint are not very limitating,

a simple verification is done in order to be sure that the connectivity is not over-passed.

The radio design process provides the number of Nodes B required in the target area. Therefore the

number of required RNC for the first constraint is easily determined (#RNC1).

For the second constraints, the process is as follow: a preliminary number of RNC (#RNC 2') is

determined by the average traffic on the target area. This first estimation is further refined by

calculating the peak traffic per RNC (for a given GoS) and verifying again the RNC throughput. If

this constraint is not respected, the number of RNC is incremented and the peak traffic re-

calculated. This process is performed until the constraint is respected. By this way, the second

number of required RNC is obtained (#RNC2'').

Then, with the number of required RNC, the traffic on Iub and Iu/Iur (i.e. per RNC) can be derived.

The peak traffic on those interfaces is calculated by means of a Gaussian law. By adding margins

(see Iub dimensioning and Iu/Iur dimensioning), the connectivity constraints can be verified.

The drawing reported hereafter describes the RNC dimensioning process.

YES

NO

RNC Product Specs

Input:

#Nodes B

Calculation

#RNC1

Input:Average

Traffic

Calculation

#RNC2'

TrafficTable per

RNC

Peak

Traffic

Calculation

Increment

#RNC2

#RNC

IU-CS & IU-PS

MAX

#RNC1, #RNC2

OK ?

Capacity

Node-B

limitation

Throughput

limitation

Iu and Iur

Connectivity

limitation

RNC2

RNC

Product

Specs

i ii

iii

iv

v

Iubconnectivity

limitation

vi

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Figure 19 : RNC dimensioning process

1.10.4 Step by step process

1.10.4.1 Node-B limitation

i. The node-B constraint determines a first number of required RNC - #RNC1.

#RNC1 is calculated as follow:

#RNC1.=RNConebysupportedB-nodesofNumber

B-nodesofnumberTotal.

1.10.4.2 Throughput and connectivity limitations

ii. The throughput and connectivity constraints determine a second number of RNC - #RNC2. An

initial calculation (#RNC2') is performed by considering the global average CS and PS traffic

(without any additional margins) in the target area. This traffic is supposed uniformely

distributed.

#RNC2' is calculated as follow. The RNC Mbps vs Erlang curve of Figure 18 is modified into a

PS vs CS curve, by translating the CS traffic from Erlang to Mbps (Erlang multiplied by 12 kbpsvoice codec).

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0

10

20

30

40

50

6070

80

90

100

0 10 20 30 40 50 60 70

CS thru [Mbps]

PSthru[Mbp

s]

(CSave , PSave)

(XI' , YI')

(CSpeak , PSpeak)

(XI'' , YI'')

Figure 20 : Calculation of #RNC2

This curve allows to calculate #RNC2': having defined CSave, PSave the global average CS and

PS traffic respectively, and X I', YI' the intersection point as depicted in Figure 20, #RNC2' is

given by:

#RNC2' =

'

,'

maxI

ave

I

ave

Y

PS

X

CS

Note that this is a preliminary calculation, which takes into consideration only the average traffic

(and not the peak, that is including the burstiness).

iii. In order to refine the above calculation, it is necessary to determine the peak CS traffic and PS

traffic per RNC (RNC

peakCS andRNC

peakPS ). The peak values are calculated by means of

a gaussian law approach.

iv. It must be verified that the calculated peak throughput per RNC can be supported in terms of

throughput and connectivity (see point v). If these constraints are not respected, the number of

RNC is incremented (#RNC2'') and the peak traffic re-calculated (i.e., step iii rerun). This

process is performed until the RNC throughput and connectivity constraints are respected.

To verify the throughput constraint, the peak CS and PS traffic must be compared to RNC

capacity, which means that the point (RNCpeak

CS ,RNCpeak

PS ) must be below the RNC

throughput curve (see Figure 21).

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0

10

20

30

40

50

6070

80

90

100

0 10 20 30 40 50 60 70

CS thru [Mbps]

PSthru[Mbp

s]

(CSpeak| RNC , PSpeak|RNC)

Figure 21 : Validation of RNC throughput constraint

v. Moreover, to verify that the connectivity constraints are satisfied, the total throughput (including

ATM/AAL overheads, O&M margins, signalling factor as described in Iub and Iu/Iur

dimensioning sections) carried by Iub and Iu/Iur must be calculated. It must then be compared

with the available number of STM-1 per RNC, to be sure that the RNC can support it. If it is not

the case, a RNC must be added and the connectivity constraints re-verified.

By this way, the second number of RNC is obtained #RNC 2.

1.10.4.3 Final number of RNC

vi. The final number of RNC is the maximum between #RNC1 and #RNC2.

1.11 Iu-cs and Iu-ps dimensioning

1.11.1 General process

One step of the RNC dimensioning process consists on the calculation of the peak throughput per

RNC. The Iu dimensioning derives from this calculation: the total throughput is obtained by adding

to the peak throughput the overhead, signalling and O&M margins, as depicted in the following

figure.

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RNC

Dimensioning

CS & PS

Traffic

per RNC

ATM

Overheads

factor

Signalling

factor

O&M

Margin

Total

Iu-cs and Iu-psThroughput

Figure 22 : Iu-cs and Iu-ps dimensioning process

1.11.2 Default parameters

A 40% margin is considered to take into account ATM and AAL overheads.

A margin of 10% is sufficient to take into account additional traffic due to signalling.

In the same way, a 10% margin is considered to take into account additionnal traffic due to O&M.

1.12 Iur dimensioning

The traffic transmitted on Iur interface is mainly due to the soft handover process between two

RNCs. Iur will be logically mapped into the same physical links carrrying the Iu interface. Thus, the

additional traffic on Iur can be considered as an additional margin on the Iu-cs and Iu-ps interface

dimensioning.

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1.13 Conclusions

The previous sections give an idea of how Alcatels UTRAN dimensioning approach may be used

to perform a pre-sales UMTS design, meeting the Operator's needs. Alcatel would welcome the

opportunity to work closely with the Operator in performing the network design activity.

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