1-OWP112010 WCDMA Radio Network Coverage Dimensioning ISSUE1.21

WCDMA Radio Network Coverage Planning

Confidential Information of Huawei. No Spreading Without Permission

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Capacity–coverage (typical case: downlink load balance)

Capacity–quality (typical case: lowering BLER through outer loop power control)

Coverage–quality (typical case: lowering the data rate of the connections with

much path loss through AMRC)



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3G radio network planning can be divided into three phases. They are shown in

above figure, and consist of dimensioning, pre-planning and cell planning.

According to the above figure, the output result of radio network dimensioning

stage serves as the input condition of the pre-planning, and the pre-planning is

based on the network dimensioning and also checks the network dimensioning

result. The site quantity can be adjusted according to the pre-planning result in

order to obtain the reasonable sites. If the existing sites are considered in the

selection of theoretical sites during the pre-planning, the pre-planning result will

be more practical, thus facilitating the cell planning.



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Radio Network Dimensioning is a simplified analysis for radio network

Dimensioning provides the first and most rapid evaluation of the network element

number as well as the associated capacity of those elements. The target of

dimensioning phase is to estimate the required site density and site configurations

for the area of interest. Dimensioning activities include radio link budget and

coverage analysis, capacity evaluation and final estimation of the amount of

NodeB hardware and E1, cell average throughput and cell edge throughput.

Objective:

To obtain the network scale ( approximate NodeB number and

configuration)

Method:

Select a proper propagation model, traffic model and subscriber

distribution, and then estimate the NodeB number, coverage radius, E1

number per site, cell throughput, cell edge throughput and so on.



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The service distribution, traffic density, traffic growth estimates and QoS

requirements are already essential elements in dimensioning phase. Quality is

taken into account here in terms of blocking and coverage probability.



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Wireless network dimensioning intends to obtain the approximate UTRAN scale.

Based on the network dimensioning, geography and traffic distribution, the

network is pre-planned in detail by using planning software and digital map.

Based on the network dimensioning and site information, the initially selected

WCDMA site is imported into the planning software, and coverage is estimated by

parameters setting. Then an analysis is made to check whether the coverage of

the system meet the requirements. If necessary, the height and tilt of the antenna

and the NodeB quantity are adjusted to optimize the coverage. And then the

system capacity is analyzed to check whether it meets the requirement.

Implementation parameters, such as antenna type / azimuth / tilt / altitude /

feeder type / length …

Cell parameters, such as transmission power of traffic channel and common

channel, orthogonal factor, primary scrambling code…



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Based on the network dimensioning and site information, the initially selected

WCDMA BS is imported into the planning software, and coverage is estimated by

setting the cell parameters and engineering parameters. Then an analysis is made

to check whether the coverage of the system meet the requirements. Then the

system capacity is analyzed to check whether it meets the requirement. If

necessary, the height and tilt angle of the antenna and the BS quality are adjusted

to optimize the coverage.



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These graphs are prediction results of Huawei planning tool: U-Net

For the result of coverage prediction, focus on the distribution of best servers and

pilot level. For the small areas with unqualified level, adjust the azimuth and

down tilt to improve the coverage. For the large areas with weak coverage,

analyze whether the site distance is over large:

If yes, add sites to improve coverage.

If no, check whether the configuration of parameters related to coverage

prediction is correct.



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We should consider other factors when we select the backup sites

Commercial factor: rent

Radio propagation factor: situation / height / surrounding /

Implementation factor: space / antenna installation / transmission / power

supply



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Simulation is oriented to simulate the running situation of networks under the

current network configuration so as to facilitate decision-making adjustment.

Now there are two system simulation classes: static simulation and dynamic

simulation.

Static simulation focus on user behavior such as browsing Internet, call. It would

gain the performance of radio network based on “snapshot”.

Dynamic simulation focus on detail of user behavior such as duration and data

rate of browsing. It would gain the performance of radio network based on

analysis of mobile subscribers. But it requires higher precision of e-map.

At present, Static simulation is in common use. Monte Carlo simulation is one

type of static simulation.



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Some UEs or terminals are distributed based on a certain rule (such as random

even distribution) at each “snapshot”

It is required to consider the possibility of multiple connection failure

(uplink/downlink traffic channel maximum transmit power, unavailable channels,

low Ec/Io and uplink/downlink interference



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These graphs are prediction results (based on simulation) of Huawei planning tool:

U-Net

The previous predictions (Coverage by transmitter, Coverage by signal level,

Overlapping zones) are based on coverage, the predictions in this slide are based

on simulation.



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In the coverage dimensioning, the link is estimated according to elements such as

planned area, network capacity, and equipment performance in order to obtain

the allowed maximum path loss. The maximum cell radius is obtained according

to the radio propagation model and allowed maximum path loss. And then the

site coverage area is calculated. Finally, the site quantity is calculated. Of course,

the site quality is only for the ideal cell status, and some additional sites will be

needed in actual terrain environment.



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Link dimensioning intends to estimate the system coverage by analyzing the

factors of the propagation channels of the uplink signal and downlink signal. It is

the link analysis model.

If the parameters such as transmit signal power, gain and loss of the transmitter

and receiver, and quality threshold of received signal are known or estimated, the

allowed maximum path loss used for ensuring the quality of received signal can

be calculated.



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In network planning, the value should be set according to the UE capacity with

lowest power grade in the commercial network of the operator.

Note that it is possible that a UE supporting high-speed uplink data service

(higher than 64kbps) has a higher power grade than a UE supporting only voice

and low-speed data services, for example, power grade 3dBm ～ 24dBm.

With a higher maximum power rating, the maximum path loss is increased accordingly.

This allows the operator to plan cells with a relatively larger coverage.

The UE cable loss, connector loss, and combiner loss are quite negligible, hence a

0 dB loss is assumed here。



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The 0 dBi antenna gain is considered here with respect to the internal antenna of

mobile phones.



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The penetration loss is related to building type, incidence angle of

the radio wave and so on. In the link budget, assume that the

penetration loss obey the Log-Normal distribution. The penetration

loss is related to mean value of penetration loss and standard

deviation

When indoor coverage is required to coverage by outdoor macro NodeBs,

building penetration loss needs to be considered. Building penetration loss is

related to such factors as incidence angle of the radio wave, the building

construction (the construction materials and number and size of windows), the

internal building layout and frequency. Building penetration loss is highly

dependent on specific environment and morphology and varies greatly. For

instance, the wall thickness in Siberian tends to be larger than that of Singapore

in order to resist coldness and hence the former’s building penetration loss is

correspondingly larger.

In addition, sometimes vehicular coverage may be required and consequently

vehicular penetration loss also needs to be included in link budget process. typical

vehicular penetration loss is around 8dB.



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Antenna gain: It refers to the ratio of the square of the actual field of an antenna

at a point in the space to the square of the field of an ideal radiation unit at the

same point in the space, namely power ratio. It is the gain in the main transmit

direction. In general, the gain is related to the antenna pattern. If the central lobe

is narrow and the back lobe and side lobe are small, the gain is high. If the

transmit direction is centralized, the antenna gain is high. For an omnidirectional

antenna, the gain in all the directions is the same.

Front-to-back ratio: It refers to the ratio of the maximum gain in the principal

direction to the gain in the reverse direction. It describes the directing feature. If

it is high, the directed receive performance of the antenna is high.

Beam width: It refers to the separation angle between the main transmit direction

of the power and the point with 3 dB of transmit power reduced, and the area is

called an antenna lobe. Tilt: It refers to the tilt angle of a directional plate

antennal. It is used to control interference and improve coverage.

Polarization: The vector direction of the electrical field in the direction with the

highest radiation. A dual polarized antenna can provide diversity over a single

antenna, thus saving one antenna.

In general, there are two or more lobes in an antenna pattern. The largest lobe is

the central lobe, and others are side lobes. The separation angle between the two

half-power points of the central lobe is the lobe width of the antenna pattern,

namely, half-power (angle) lobe width. If the central lobe is narrow, the directivity

is high, and the anti-interference capability is high.



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Radio propagation in the land mobile channel is characterized by multiple

reflections, diffractions and attenuation of the signal energy. These are caused by

natural obstacles such as buildings, hills, and so on, resulting in so-called multi-

path propagation. Furthermore, with the moving of a mobile station, the signal

amplitude, delay and phase on various transmission paths vary with time and

place. Therefore, the levels of received signals are fluctuating and unstable and

these multi-path signals, if overlaid, will lead to fading i.e. short term fading. The

mid-value field strength of Rayleigh fading has relatively gentle change and is

called “Slow fading” i.e. long term fading. And it conforms to lognormal

distribution.

Long term fading– the variation of signal level is slow and smooth.

Short term fading– the variation of signal level is fast and poignant



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Slow Fading --- Signal levels obey Log-Normal distribution

Propagation models predict only mean values of signal strength , the mean value of

signal strength fluctuates. The deviation of the mean values has a nearly normal

distribution in dB, The variation in mean values is called log-normal fading.

Probability that the real signal strength will exceed the average one on the cell border is

around 50%,for higher than 50% coverage probability an additional margin has to be

introduced. The margin is called slow fading margin.

Slow Fading Margin (SFM) is related with coverage probability in cell edge and standard

deviation of slow fading. The equation is described as following:



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Soft Handover --- handover between different NodeBs

Softer Handover --- handover between cells in a NodeB

SHO gain over slow fading is also known as the Multi-Cell gain because in soft

handover more than 1 branch exists and hence the coverage probability increases

which would result in the decreasing of required slow fading margin.

Suppose that soft handover has 2 branches, and the orthogonality of the two

radio link branches on slow fading is 50%. We can calculate the slow fading

margin required with soft handovers based on the former assumptions, and

compare it with the slow fading margin required without soft handover to get the

SHO gain over slow fading.

SHO gain over slow fading is dependent on the required area coverage probability,

the propagation path loss slope and the STD. The following table gives the

calculated SHO gain over slow fading and the propagation path loss slope equals

to 3.59.



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Fast power control

to enhance weak signal caused by Rayleigh fading

to mitigate interference and enhance the capacity

to promote power utilization efficiency

In WCDMA, user signals should be received at the NodeB with equal power all the

time and for downlink the transmitted TCH power should be as small as possible

while maintaining the required Qos. This implies that fast fading are compensated

by the power control algorithm, which requires additional headroom at both UE

and NodeB in order to let UE and NodeB following the power control commands

at cell edge.



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Because of the macro diversity combination, the soft handover reduces the

required Eb/No by a single radio link, which results in additional macro diversity

gain.



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Interference margin is the required margin in the link budget due to the noise rise

caused by system load (the noise rise due to other subscribers). The higher the

system load is, the larger the interference margin should be.



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If the W=1Hz, Nth=-174dBm/Hz

If the W=200kHz, Nth=-121dBm/200kHz



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Typical noises are: external sky and electric noise, vehicle start-up noise, heat

noise from inside systems, scattered noise of transistor during operation,

intermodulation product of signal and noise.

Noise figure is used for measuring the processing capability of the RF component

for small signals, and is usually defined as: output SNR divided by unit input SNR.

NF

Si

Ni

So

No



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For common services, the bit rate of voice call is 12.2kbps, the bit rate of video

phone is 64kbps, and the highest packet service bit rate is 384kbps(R99). After

the spreading, the chip rate of different service all become 3.84Mcps.



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For instance:

Service BLER Channel Model Uplink Eb/N0 Downlink Eb/N0

AMR12.2k 1.00% TU3 5.4dB 7.8 dB

RA120 4.5 dB 8.3 dB

CS64k 0.10% TU3 2.8 dB 6.3 dB

RA120 2.8 dB 6.8 dB

CS64k 1.00% TU3 2.5 dB 5.4 dB

RA120 2.3 dB 6 dB



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In case of multi-path propagation, certain energy will be detected by the

RAKE receiver, and become interference signals. We define the orthogonal

factor to describe this phenomenon. It is obtained through simulation, and

related to environment type and cell radius.



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Continuous coverage target service requirement with specific coverage probability

should be given for R99

Cell edge throughput requirement with specific coverage requirement should be

given for HSDPA



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The cell total transmit power is the constant resources. The DL power consists of

the following three parts:

Power of the HSPA DL physical channel (HS-PDSCH, and HS-SCCH)

Common channel power

DPCH power



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Fast power control

For R99, power control margin should be considered

For HSDPA, the maximum transmission power for HS-PDSCH is the

remaining power excluding R99 power and power margin, and no power

control margin

SHO gain

For R99, SHO gain should be considered

For HSDPA, only hard handover, no SHO gain

HSDPA related parameters should be configured when simulation

Max number of HS-PDSCH channel

Min number of HS-PDSCH channel

HSDPA power allocation, dynamic or fixed

HS-SCCH power allocation, dynamic or fixed

Max number of HSDPA users

Scheduling Algorithm



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Single carrier for HSDPA and R99

Advantages

Maximum resource utilization efficiency

Save cost

Disadvantages

Handover between HSDPA cell and R99 cell

Two carriers for HSDPA and R99

Advantages

Fewer inter-frequency handover for HSDPA user

Disadvantages

High cost



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If operator wants to upgrade HSDPA from R99, R99 should be met first, and

HSDPA should not affect the R99.

If operator setups R99 and HSDPA directly, R99 and HSDPA requirement should

be met at the same time.



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DL Coupling Loss :

PL_DL: Downlink path loss

Lf_BS: cable loss of NodeB

Ga_antenna: Gain of UE antenna and NodeB antenna

Lb: Body loss

SFMNSHO: Slow fading margin without soft handover

Lp: Penetration loss

Cell edge Ec/No:

PHS-DSCH : total power of HS-DSCH channel

: non-orthogonality factor

: neighbor cell interference factor

: downlink load factor including R99 and HSDPA service

Pmax : max transmission power of downlink

Nt : thermal noise power spectral density , typical value is -108.16dB

NF : receiver noise figure of UE, typical value is 7dB

f

DL



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The theoretical maximum throughput is decided by the number of HSDPA codes.

For HSDPA , soft handover gain and fast fading margin should not be considered

in link budget , since neither power control nor soft handover in HS-PDSCH

channel



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The step is present below:

According to the Cell Radius comes from R99 dimensioning, the Downlink

Path Loss can be calculated

According to the Downlink Path Loss , the Downlink Coupling Loss can be

calculated

According to the Downlink Coupling Loss and HS-DSCH Power, Cell Edge

Ec/No can be calculated

According to the Cell Edge Ec/No and simulation result, Cell Edge

Throughput can be calculated



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According to the Cell Edge Throughput and simulation result, Cell Edge


According to the Cell Edge Ec/No and HS-DSCH Power, the Downlink

Coupling Loss can be calculated

According to the Downlink Coupling Loss, the Downlink Path Loss can be

calculated

According to the Downlink Path Loss and and Propagation Model, HSDPA

Cell radius can be calculated



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According to the Cell Radius comes from R99 dimensioning, the Downlink

Path Loss can be calculated

According to the Downlink Path Loss , the Downlink Coupling Loss can be

calculated

According to the Cell Edge Throughput and simulation result, Cell Edge


According to the Downlink Coupling Loss and Cell Edge Ec/No , HS-DSCH

Power can be calculated



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1-OWP112010 WCDMA Radio Network Coverage Dimensioning ISSUE1.21

Documents

1-OWP112010 WCDMA Radio Network Coverage Dimensioning ISSUE1.21