Owj101107 Wcdma Rnp Antenna Type Selection Issue1.1

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Course OWJ101107

WCDMA RNP Antenna Type Selection

ISSUE 1.1


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OWJ101107 WCDMA RNP Antenna Type Selection ISSUE1.1 Table of Contents

Table of Contents

Course Description....................................................................................................................... 1Course Introduction.................................................................................................................. 1Targets of the course...............................................................................................................1References............................................................................................................................... 1

Chapter 1 Overview...................................................................................................................... 21.1 Antenna Classification....................................................................................................... 21.2 Major Technical Performances of the Antenna................................................................. 2

1.2.1 Frequncy Bands...................................................................................................... 21.2.2 Gain........................................................................................................................ 21.2.3 Pattern.................................................................................................................... 31.2.4 Relationship between Beam Width and Gain.........................................................51.2.5 Polarization Type....................................................................................................61.2.6 Downtilt................................................................................................................... 71.2.7 Voltage Standing Wave Ratio (VSWR)................................................................... 71.2.8 Port Isolation........................................................................................................... 81.2.9 Max Power ............................................................................................................. 81.2.10 Connector Type.................................................................................................... 81.2.11 Passive Inter-modulation (PIM).............................................................................81.2.12 Antenna Size and Weight..................................................................................... 81.2.13 Wind Load............................................................................................................ 91.2.14 Working Temperature and Humidity.....................................................................91.2.15 Lightning Protection..............................................................................................91.2.16 Three-Proof Capability.......................................................................................... 9

Chapter 2 Antenna Type Selection............................................................................................ 10

2.1 Guidelines for Frequency Bands Selection..................................................................... 102.1.1 Outdoor Antennas................................................................................................. 102.1.2 Indoor Antennas .................................................................................................. 10

2.2 Guidelines for Gain Selection..........................................................................................102.3 Guidelines for Beam Width Selection..............................................................................112.4 Guidelines for Polarization Type Selection...................................................................... 112.5 Guidelines for Downtilt Type Selection............................................................................ 11

2.5.1 Comparison between Mechanical Downtilt and Electrical Downtilt.......................112.5.2 Comparison between Fixed Electrical Downtilting and Null Filling........................132.5.3 Planning and Optimization of Downtilt Angle........................................................13

2.6 Guidelins for Front-to-back Ratio Selection..................................................................... 142.7 Guidelins for Antenna Size Selection.............................................................................. 142.8 Guidelins for Antenna Impedance Selection................................................................... 14

2.9 Guidelines for Antenna Selection at Special Occasions..................................................15

Chapter 3 WCDMA Antenna Type Selection at Different Scenarios.......................................173.1 WCDMA Antenna Type Selection for Urban Coverage................................................... 173.2 NodeB Antenna Type Selection for Suburb Coverage....................................................183.3 NodeB Antenna Type Selection for Rural Areas.............................................................183.4 Antenna Type Selection for Highway Coverage.............................................................. 193.5 Antenna Type Selection for Rural Coverage...................................................................203.6 Antenna Type Selection for Offshore Coverage..............................................................213.7 Antenna Type Selection for Tunnel Coverage.................................................................213.8 Antenna Type Selection for Indoor Coverage ................................................................ 22

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OWJ101107 WCDMA RNP Antenna Type Selection ISSUE1.1 Course Description

Course Description

Course Introduction

Targets of the course

References

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OWJ101107 WCDMA RNP Antenna Type Selection ISSUE1.1Chapter 3 WCDMA Antenna Type Selection

at Different Scenarios

1 OverviewAntenna is the interface between a radio transceiver and free space. Antenna canboth emit and receive radio waves at the same time. When emitting radio waves, itconverts the high-frequency currents into electromagnetic waves; when receivingradio waves, it converts electromagnetic waves into high-frequency currents.

Network coverage is finally realized through antennas. Therefore, the networkcoverage quality and interference control depend largely on the correctness ofantenna type selection.

1.1 Antenna Classification

Similar with antennas of GSM base stations, WCDMA antennas can also be classifiedinto omni antennas and directional antennas according to the feature of pattern.

Based on the polarization mode, antennas can be classified into vertical polarizationantennas (also called mono-polarization antennas) and cross polarization antennas(also called dual polarization antennas).

According to the outlines, antennas can be classified into whip antennas, plateantennas and cap antennas.

1.2 Major Technical Performances of the Antenna

The technical performances of an antenna include: frequency bands, gain,polarization type, beam width, electrical downtilt angle, the downtilt adjustmentrange, front-to-back ratio, side lobe suppression , null filling, return loss, max power ,impedance and third order intermodulation. The mechanical performances include:size, weight, connector type and wind load.

1.2.1 Frequncy Bands

Frequency bands of WCDMA system:

1. For Europe and China

Uplink: 1920 ~ 1980 MHz

Downlink: 2110 ~ 2170 MHz

2. For North America

Uplink: 1850 ~ 1910 MHz

Downlink: 1930 ~ 1990 MHz

1.2.2 Gain

As a passive device, antenna itself cannot increase the energy of emitted signals. It

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only can centralize the energy to a certain direction by combining the antenna dipolesand changing their feeding mode. Gain is one of the most important parameters of anantenna. It indicates the antennas capability of centralizing energy to a certaindirection. Two units are often used to antenna gain: dBi and dBd. The relationshipbetween them is shown as follows:

0 2.15dBd dBi=

dBi is defined as the energy centralizing capability of the actual directional antenna(including omni antenna) in relation to isotropic antennas. i stands for isotropic.

dBdis defined as the energy centralizing capability of the actual directional antenna(including omni antenna) in relation to dipole antennas, and d stands for dipole.

The relationship between the two units for antenna gain is illustrated as follows:

Figure 1.1 Relationship between dBi and dBd

The antenna gain is not only related to the quantity of dipole units, but also related tothe horizontal beam width and vertical beam width.

1.2.3 Pattern

The graph describes the distribution of electromagnetic field of the antenna emissionalong the fixed distance on the angular coordinates is called pattern. A pattern

presented by emission field intensity is called field intensity pattern, a patternpresented by power density is called power density pattern, and a pattern presentedby phase is called phase pattern.

The antenna pattern is a three-dimension graph, but it usually appears as twopatterns in two planes perpendicular to each other, called plane patterns. In general,they are called vertical pattern and horizontal pattern. There are some specialdirectional antennas such as heart-shape antenna and 8-shape antenna.

The directionality of an antenna is obtained by means of arrangement of dipoles andchange of the feeding phase of each dipole. This is very similar to the interferenceeffect of light. Therefore energy will be enhanced in certain directions, whileweakened in other directions, forming lobes (or beams) and nulls. The lobe with thestrongest energy is called main lobe, the upper and lower lobes with the secondstrongest energy are called first side lobes, and so on. In case of directional



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antennas, back lobes exist. The horizontal and vertical patterns of a directionalantenna are as follows:

Figure 1.1 The horizontal and vertical patterns of a directional antenna

The beam width (also called semi-power angle) includes the horizontal beam widthand vertical beam width. They are defined as the beam width between two points inhorizontal direction and vertical direction respectively which the power are half of themax emission power. Common horizontal beam widths of NodeB antenna include

360, 90, 65, 60 and 33, and common vertical beam widths include 6.5, 7, 10,13 and 16.

Front-to-back ratio: It refers to the signal emission strength ratio between the mainlobe direction and back lobe direction, namely the difference between the side lobelevel beam within 180 30 of the antenna backward direction and the maximumbeam, presented by a positive value. In general, the front-to-back ratio is within 18 ~45dB. For dense urban areas, antennas with large front-to-back suppress ratiosshould be used in priority.

Null filling: In case of shaped beam design in the vertical plane of a NodeB antenna,in order to make the emission level in service area more uniform, the first null of lowerside lobe should be filled. As the vertical beam width of high-gain antenna is narrow,the coverage quality of such antennas in the nearby zone should in particular beimproved by using null-filling antennas. If null depth is greater than -26dB in relation

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Side lobes

Nulls

Main lobe

Main lobemax value

Null filling

5dB/scale

Vertical pattern

Front-to- rearratio

Horizontal semi-power angle

5dB/scaleHorizontal pattern-3dB

4


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to the main beam, it means that null filling is used. Some suppliers use percentage torepresent null filling. For example, if the value of null filling is 10%, the relationshipbetween these two methods is shown as follows:

( ) ( )20 lg % 100%Y dB x

= For example: If null filling is 10%, X=10, then

( )20 lg 10% 100% 20 dBY = =

Upper side lobe suppression: In order to improve the efficiency of frequency reuseand reduce co-channel interference to adjacent cells in micro cell system, the upperside lobe of antennas should be kept as low as possible when designing the antennaswith beam shaping technology as high side lobe can affect adjacent cells andenhance the D/U value (strength ratio between useful and useless signals). The firstupper side lobe level should be less than -18dB in relation to the main beam. As for amacro cell system, there is no such a requirement.

1.2.4 Relationship between Beam Width and Gain

An antenna is an energy-centralizing device. The enhancement of emission in onedirection means the reduction of emission in other directions. In general, we canenhance the emission strength in a certain direction by reducing the horizontal lobewidth so as to increase the antenna gain. Under a given antenna gain, the horizontalbeam width is in reverse proportion with the vertical beam width, as shown below:

( )10 lg 32400aG

Where, Ga refers to antenna gain, unit: dBi;

refers to the vertical beam width, unit: degree .

refers to the horizontal beam width, unit: degree.

Based on the formula above, when we already know the gain and horizontal beamwidth of an antenna, we can estimate its vertical beam width.

For example: If the gain of an omni antenna is 11dBi, and the horizontal beam widthis 360, the vertical beam width is:

1.1

324007.15

360 10

o = =

Because of differences in design and manufacturing, the actual vertical beam width ofomni antenna is usually smaller than that of calculation result. The less the differenceis, the better the design is .

Take a dipole antenna as example, the relationship among antenna gain, verticalbeam width and horizontal beam width is shown as follows:



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Figure 1.1 The relationship between antenna gain and beam widths

Therefore, when the antenna gain is low, the vertical beam width and the horizontalbeam width are usually big; when the antenna gain is high, the vertical beam widthand the horizontal beam width are usually small.

In addition, the antenna gain depends on the number of dipoles. The more dipoles,the higher gain and bigger aperture of the antenna ( the effective receiving area). For

omni antennas, when the gain increases by 3dB, the antenna length increases by onetime. Therefore the gain of omni antenna will not exceed 11dBi generally.

1.2.5 Polarization Type

Polarization is a concept describing the vector direction of electric field ofelectromagnetic wave. Unless otherwise specified, the direction of electric field vectoris the polarization direction of electromagnetic wave. Here, the polarization of antennarefers to the vector direction of electric field along the direction of maximum emissionof the antenna.

If the direction of the electric field vector does not change at any time, the

electromagnetic wave is called linear polarization wave. With the ground as a


Vertical

Horizontal semi-power lobe width

Gain (dB)

6


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reference plane, if the electric field vector is parallel to the ground, theelectromagnetic wave is called horizontal polarization wave. Sometimes, the electricfield vector is not fixed, and the pathway that the vector endpoint works out is a circle.In this case, the electromagnetic wave is called circular polarization wave. If thepathway is an ellipse, the wave is called elliptical polarization wave. Both elliptical

polarization wave and circular polarization wave have the rotating feature.

The electromagnetic waves of different bands propagate in different polarizationmodes. Mobile communications systems usually use vertical polarization, while thebroadcast systems usually use horizontal polarization. Elliptical polarization isgenerally used in satellite communication systems.

Two polarization types of WCDMA antennas include single polarization and dualpolarization. They both are linear polarization antennas. Single polarization antennasin WCDMA system adopt vertical polarization, while dual polarization antennas usepolarization diversity to minimize the negative effect of multi-path fading in the mobilecommunication system so as to improve the quality of receiving signals. Dualpolarization antennas in the WCDMA system usually are designed with the 45

cross polarization type.

1.2.6 Downtilt

Antenna downtilt is an important method to strengthen the signal level of the mainservice area and reduce interference to other cells. The downtilt modes includemechanical downtilt, fixed electrical downtilt and adjustable electrical downtilt(electrically controlled antenna). Mechanical downtilt refers to setting the downtiltangle by adjusting the antenna bracket . Electrical downtilt refers to controlling thedowntilt angle by changing the phase of the dipole. The electrical downtilt angle of afixed electrical downtilt antenna cannot be changed after the antenna leaves thefactory, while the downtilt angle of an electrically controlled antenna can be changed.

Mechanical downtilt and electrical downtilt can be applied together.

1.2.7 Voltage Standing Wave Ratio (VSWR)

For a base station antenna, the maximum VSWR should be below 1.5:1. Assume thatZA is the input impedance of antenna and Z0 is the nominal characteristic impedance(Z0 of WCDMA antenna is 50), then the reflection coefficient at the input port ofantenna is:

0

0

A

A

Z Z

Z Z

=

+

1

1VSWR

+ =

Return loss (R.L.) can also indicates the matching characteristic of the port. Returnloss is calculated as follows:

. .( ) 20 lgR L dB =

When VSWR is 1.5:1, R.L. is 13.98dB.

When the input impedance is not consistent with the characteristic impedance, thereflected wave and the incident wave overlap on the feeder and form standing wave.



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The ratio between the maximum value and the minimal value of the total voltage isVSWR. If the VSWR is too big, the communications range will be shortened.

1.2.8 Port Isolation

For multi-port antennas, such as dual polarization antennas, and dual band and dualpolarization antennas, the isolation between ports should be greater than 30dB. Forthe case of inter-system sharing, the isolation between inter-system ports shouldmore than 30dB. Normally, more than 40dB is recommended.

1.2.9 Max Power

It refers to the average power and not peak power . An antenna includes couplingdevices such as matching device, balancing device and phase shift device. Theirbearing power is limited. In view of the actual maximum output power of NodeB(single-carrier power is 20W), if one port of the antenna supports the input of 4carriers, then the maximum input power of the antenna will be 80W. Therefore, thesingle-port power handling of the antenna should be greater than 150W (When theambient temperature is 65C).

1.2.10 Connector Type

In order to guarantee passive inter-modulation performance and reliability of RFconnection, the connector type should be 7/16 DIN-Female type. Before an antennais installed, there should be a closure cap on the connector to prevent oxidation andingression of impurities.

1.2.11 Passive Inter-modulation (PIM)

The passive inter-modulation refers to the inter-modulation effect caused by thepassive components such as connector, feeder, antenna and filter due to the non-linearity of the components themselves when they work under the condition of high-power signals of multiple carriers. In general, the passive components are consideredto be linear, but under high-power conditions, all passive components are somewhatnon-linear. The causes are as follows: metals made of different materials contact onewith another, the contact surface of the same material is not smooth, the connectionis not firm; and magnetic materials exist.

The existence of inter-modulation products will cause interference to thecommunications system. Especially the inter-modulation product falling in the

receiving band will degrade the receiving performance of the system. So there arestrict requirements for the inter-modulation characteristic of passive components suchas connectors, cables, and antennas. The requirements are as follows: The passiveinter-modulation of connector is -150dBc, the passive inter-modulation of cables is -170dBc, and the passive inter-modulation of antennas is -150dBc.

1.2.12 Antenna Size and Weight

In order to facilitate storage, transportation and installation and ensure the safety, anantenna should be smaller in size and more light in weight while its electricalperformance is good enough.

At present, operators are more and more picky about the size, weight and



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appearance of antennas. So when selecting antennas, we should pay specialattention not only to the technical parameters, but also to those non-technical factors.WCDMA antennas in urban areas should be small in size and light in weight and eyeattracting, while there are no such a requirements for antennas in the suburbs andrural areas.

1.2.13 Wind Load

Antennas are usually installed on top of high buildings or iron towers, where the windis very strong all the year, especially in coastal areas. Therefore antennas should beable to work normally at the wind speed of 36m/s and should not be damaged at thewind speed of 55m/s.

Antennas themselves can normally endure strong wind. In areas with strong wind,antennas are usually damaged because of iron towers or mono-poles. Therefore insuch areas, antennas with small surface area should be used.

1.2.14 Working Temperature and Humidity

Antennas should be able to work normally at the environment temperature range of-40C to 65C and within the relative humidity range of 0 to 100%.

1.2.15 Lightning Protection

All the RF input ports of antennas must be grounded directly with DC.

1.2.16 Three-Proof Capability

Antennas should have the three-proof capability, namely: damp proof, salt mist proofand dust proof.



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2 Antenna Type Selection2.1 Guidelines for Frequency Bands Selection

2.1.1 Outdoor Antennas

Outdoor antennas should be wideband antennas with frequency band 1710 ~2170MHz . It is helpful to reduce the number of antenna types (reduce theprocurement cost) while such antennas can serve both WCDMA and DCS systemssimultaneously.

Although wideband antennas are selected exclusively, for urban coverage, thestrategies and principles for WCDMA network optimization are largely different fromthose for DCS1800. If the WCDMA and DCS systems share antennas, there will bemutual influences in the optimization of the two systems. Therefore, for urbancoverage, antenna sharing for WCDMA and DCS systems is not recommended.

2.1.2 Indoor Antennas

In general, indoor distribution systems all involve antenna sharing requirement, so thecompatibility between forward (GSM/DCS) and backward (WLAN) should beconsidered in antenna selection. Therefore the antennas for indoor distributionsystems should be wideband antennas (800 ~ 2500 MHz).

For Green Field operators like China Telecom, wideband antennas are alsorecommended. An important reason is that DCS bands after clearing may beadopted in new mobile communications modes in the future.

2.2 Guidelines for Gain Selection

The gain of outdoor omni antennas is usually within the range of 2~11dBi, the gain ofindoor omni antennas is usually within the range of 0~8dBi, and the gain of outdoordirectional antennas is within the range of 3~22dBi.

Low-gain antennas are usually used for micro cellular networks for indoor coverage

and coverage of outdoor hot spots. This kind of antenna is small in size and easy toinstall.

Mid-high-gain antennas are suitable for urban areas (the system simulation resultsfrom HUAWEI network planning department shows that antennas with higher gaincan better control interference). The horizontal beam width of this kind of antennas isgenerally 65.

High-gain antennas are suitable for wide coverage. They are applied for coverage ofhighways, railways, tunnels and long and narrow landforms. The horizontal beamwidth of this type of antennas is normally 33 or lower, resulting in many nulls.Therefore, if the antenna installation height is very high, antennas with null filling orfixed electrical downtilt should be selected to avoid null depth effect on the near-endcoverage (tower-bottom shadow effect). In addition, this type of antenna has many

dipoles and the volume is very large, so we should pay attention to the installation



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feasibility and wind load.

2.3 Guidelines for Beam Width Selection

Selection of beam width includes selection of width of horizontal beam and verticalbeam, which are closely related.

In urban areas, for 3-sector configuration , antennas with 65 horizontal beam widthare recommended. For 6-sector configuration, antennas with 33 horizontal beamwidth are recommended. In suburbs, antennas with 90 horizontal beam width arerecommended for 3-sector configurtion.

After determining the horizontal beam width, select the vertical beam width based onthe requirements for gain and interference control. The narrower the vertical lobe is,the higher the antenna gain will be, and the better the directionality will be (it is easierto control interference). However, the null depth will be more obvious. The fixedelectrical downtilt technology and null filling technology should be used.If the

narrower the vertical lobe is, the longer, heavier and more expensive the antenna willbe. In this case, we should consider the installation feasibility of the antennas.

2.4 Guidelines for Polarization Type Selection

From the signal emission point of view, mobile stations match the vertical polarizationsignals more easily because perpendicular to the ground; vertical oolarizationantennas give better coverage effect than any other non-vertical polarizationantennas, especially in open mountainous areas and rural areas. Tests show that thevertical polarization antennas give better coverage effect than dual polarization (45)antennas in open mountainous areas and rural areas. However, in urban areas, dueto large number of dense buildings, the electromagnetic waves are reflected from thesurfaces of the buildings many times. Metal objects and metal oxide film plated glassall cause polarization rotation, so there is no obvious difference between verticalpolarization antennas and 45 polarization antennas in the coverage ability.

From the receiving point of view, because two vertical polarization antennas must befor diversity receiving, while only one dual polarization antenna can do this, so singlepolarization antennas need more installation space and more maintenance work thandual polarization antenna do. In addition, there is no difference between spacediversity gain and polarization diversity gain in urban areas. As the antenna size isconcerned, a dual polarization antenna is not bigger than a single polarization in size.

Suggestion: For urban coverage, 45 dual polarization antennas are preferred; forsuburbs, rural areas and highways, vertical polarization antennas are preferred.

2.5 Guidelines for Downtilt Type Selection

2.5.1 Comparison between Mechanical Downtilt and Electrical Downtilt

Three ways and their combinations are usually used for antenna beam downtilt:Mechanical downtilt, fixed electrical downtilt and electrically controlled downtilt (forelectrically controlled antennas). During adjustment of the electrically controlledantenna downtilt angle, the antenna itself will not move, but the phase of the antennadipole is adjusted. The emitted signal power from the antenna is increased ordecreased equally in every direction so that there will be little change in the antennapattern after the downtilt angle is changed. The horizontal semi-power width is



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unrelated with the downtilt angle. However, during mechanical adjustment of thedowntilt angle, the antenna itself will be moved. It is necessary to change the downtiltangle by adjusting the bracket of the antenna. When the downtilt angle is very large,although the coverage distance in the main lobe direction changes obviously, yetsignals in the direction perpendicular to the main lobe almost keep not change, theantenna pattern deforms seriously, and the horizontal beam width becomes greateras the downtilt angle is increased. A fixed electrical downtilt antenna is similar to anelectrically controlled antenna in working principle, but its downtilt angle can not beadjusted electrically.

The advantages of an electrically controlled antenna are as follows: When thedowntilt angle is very large, the coverage distance in the main lobe direction will beshortened obviously and the antenna pattern will not remarkably change, so theinterference can be reduced. On the other hand, mechanical downtilting may deformthe pattern. The larger the angle is, the more serious the deformation is. Hence it isdifficult to control the interference. The change of horizontal patterns under the twoadjustment ways is shown in Figure 2-1. Certainly, it is related to the vertical beamwidth.

Figure 1.1 Changes of the horizontal pattern in case of different downtilt angles

In addition, electrically controlled downtilting and the mechanical downtilting havedifferent influence on the back lobe. Electrically controlled downtilting allows furthercontrol of the influence on the back lobe, while mechanical downtilting enlarges theinfluence on the back lobe, as shown in Figure 2-2:

Figure 1.2 Different influences of different downtilt modes on back lobe

If the mechanical downtilt angle is very large, the emission signals of the antenna will

propagate to high buildings in backward direction through the back lobe, thus


Electr. downtiltMechanical downtil

Back lobe peak

value l

Mechanicaldowntilt

Horizontalpattern

Main lobe peak

value

Rotation axis

Back lobe peakvalue

Electr. downtilt

Main lobe peak

value

Horizontalpattern

12


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resulting in additional interference.

In addition, during network optimization, management and maintenance, when weneed to adjust the downtilt angle of an electrically controlled antenna, it isunnecessary to shut down the entire system. So we can monitor the adjustment of the

antenna downtilt angle using special test equipment for mobile communication, so asto ensure the optimum value of the downtilt angle value of the antenna. The stepdegree of downtilt adjustment of an electrically controlled antenna is 0.1, while that ofa mechanical antenna is 1 or bigger. After installing an electrically controlledantenna, the maintenance personnel can adjust the downtilt angle on the ground,without climbing to the antenna installation position. The maintenance personnel canalso monitor and adjust remotely NodeB antennas on high mountains and in remoteareas. During mechanical adjustment of the downtilt angle, the power amplifier of thecell should be shut down. Monitoring cannot be carried out during adjustment of thedowntilt angle. The downtilt angle of a mechanical antenna is a theoretical valuecalculated by means of computer simulation and analysis software, with a certaindeviation from the actual value. In addition, it is troublesome to adjust the downtiltangle of a mechanical antenna. The maintenance personnel usually have to climb to

the antenna installation position to adjust the downtilt angle in the night. Whats more,in some cases, after antennas are installed, it is very difficult to adjust the downtiltangle, for example, when the antennas are installed on mountain top, on specialbuildings, and so on.

WCDMA system is a interference limited system. If three or more sector signals withsimilar level exist in a certain area, pilot pollution will occur and the cell capacity willdecrease. Therefore, in urban areas, during antenna selection, electricity downtiltantennas are preferred. An electrically controlled antenna is expensive (twice theprice of a non-electrically controlled antenna). Therefore, if the project is investmentsensitive, we should select fixed electrical downtilt antennas in priority.

2.5.2 Comparison between Fixed Electrical Downtilting and Null Filling

We can solve the problem of tower-bottom shadow effect caused by nulls by usingfixed electrical downtilt or null filling antennas. But the two methods are different fromeach other. The use of fixed electrical downtilting can shorten the coverage range ofthe main lobe, but in occasions where downtilt angles are generally large, it canexpand the downtilt angle adjustment range. Through null filling, a kind of patternshaping technology, we can obtain a good pattern. In this case, the upper side lobecan be suppressed, so this kind of antennas will influence other aspects. Certainly itcannot expand the downtilt angle adjustment range. At present, manufacturers allprovide WCDMA antennas with null filling and upper side lobe suppression asnecessary features.

In wide-coverage occasion, the null depth effect of antennas is a sensitive point, sowe recommend antennas with null filling, without any special requirement on theupper side lobe suppression.

For urban coverage, a large downtilt angle adjustment range is required, so werecommend antennas with characteristics of fixed electrical downtilt and upper sidelobe suppression, and preferably with the null filling characteristics.

2.5.3 Planning and Optimization of Downtilt Angle

For an omni antenna, we cannot adjust the mechanical downtilt angle, but we canselect fixed electrical downtilt antennas.

For a directional antenna, in different occasions, requirements for the downtilt angle



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adjustment range are different. The downtilt angle planning can be analyzed based ontwo occasions: coverage limited and capacity limited.

In case of coverage limited, the downtilt angle should be adjusted, so that the mainlobe can point to the cell border:

arctanh

R

=

In case of capacity limited, the downtilt angle should be adjusted so that the uppersemi-power point on the vertical side of the main lobe is directed to the cell border:

arctan2

h V HPBW

R

= +

For a fixed electrical downtilt antenna, we should deduct the electrical downtilt anglewhen setting the mechanical downtilt angle. If the required downtilt angle is smallerthan the fixed eletrical downtilt angle, we can obtain the required downtilt angle bymeans of mechanical uptilting.

2.6 Guidelins for Front-to-back Ratio Selection

In occasions where sites are densely distributed, if the back lobe is too high, it will belikely to cause pilot pollution and the network quality will be influenced. In urbanareas, the antenna front-to-back ratio should be 25dB. In suburbs or rural areas, theantenna front-to-back ratio can be appropriately lower.

The front-to-back ratio is in reverse proportion to the beam width. The narrower the

beam is, the higher the front-to-back ratio is.

2.7 Guidelins for Antenna Size Selection

Antenna size selection is mainly related to the installation feasiblity. In areas withrestricted installation conditions, for example, for railway and tunnel coverageplanning, this is a very important factor, or the critical factory that determines whetherthe antennas can be installed.

Firstly, the antenna size is related to the technical level of manufacturers, so differentmanufacturers can produce antennas of different sizes while all other parameters arethe same.

Secondly, the antenna size is related to the antenna gain. The higher the gain is, themore the dipoles are required, and as a result, the longer the antenna will be.

2.8 Guidelins for Antenna Impedance Selection

The input impedance of a base stayion is 50 normally. In order to keep the standingwave ratio low, the characteristic impedance of an antenna should match with theinput impedance, namely, it should be 50. In general, the characteristic impedancecan meet this requirement, but attention should be paid to this parameter duringselection or certification of new antennas.



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2.9 Guidelines for Antenna Selection at Special Occasions

In some cases, the area to be covered around the NodeB can be clearly distinguishedfrom the areas not to be covered. In this case, we can select antennas with beams

matching the landform of such places for coverage. The selection of the shape ofmain beam of the horizontal pattern is determined based on the coveragerequirement around NodeB. We can select the pattern according to the location of theNodeB and the landform of the coverage areas. Namely, the shape of the antennabeam should match with the landform of the area to be covered. Common landform-matching beams include 8-shape beam, heart-shape beam and so on. Theseantennas all are designed based on omni antennas.

An 8-shape omni reshaped antenna is composed of an ordinary omni antenna andtwo auxiliary reflecting metal tubes that are symmetric to each other. The reflectingmetal tubes are used for changing the horizontal pattern of the omni antenna bymeans of coupling so that horizontal pattern is in the shape of . For the purehighway coverage (it refers to the coverage of important highways in non-residential

areas), because the traffic is small, O1 configuration of site is commonly used toreduce the quantity of NodeBs and thus save the construction cost. It can be seenthat 8-shape antennas are suitable for pure highway coverage. When this kind ofantennas is used, the site location selection is very important. The stretching directionof the highway should match as much as possible with the antenna pattern.

Figure 1.1 The 8-figure-shape omni antenna pattern (horizontal)

In rural areas, there are many villages by the highway, so village coverage can be

included in highway coverage. We can select heart-shape omni antennas for thispurpose. In the direction of the highway and villages, the antenna gain can beincreased to about 13dBi so that the coverage of the highway and villages is moreefficient.


Railroad/Highway

15


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Figure 1.2 Heart-shape omni antenna pattern (horizontal)


Highway/Railroad

Highway/Railroad

Village

16


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3 WCDMA Antenna Type Selectionat Different Scenarios

In a mobile communications network, antenna selection is of great importance.Antennas should be selected based on the actual situations such as the NodeBdesign and network coverage requirements and interference conditions. Properlyselected antennas can improve the coverage effect, reduce interference, and improvethe service quality. Based on the landform and distribution of subscribers, theapplication environments of antennas can be classified into eight types: Urban (agreat number of buildings, heavy traffic), suburbs (low buildings, open area), rural(little traffic), highway (banding coverage), mountainous areas (hills, sparsesubscribers), offshore (extremely far-reaching coverage, small number ofsubscribers), tunnels and indoor.

If not otherwise specified, on-site engineers should select antennas within the rangeof antennas types already certified in the antenna database i.

3.1 WCDMA Antenna Type Selection for Urban Coverage

Application environment characteristics: NodeBs are densely-distributed, and thecoverage area of each NodeB is small. Cross-cell coverage should be avoided toreduce pilot pollution so as to improve the network quality and expanse the networkcapacity.

Principle for Antenna Type Selection:

Working frequency

In order to reduce the number of antenna codes, select wideband antennas that workin the 1710 ~ 2170 MHz band.

Polarization type

As it is difficult to select the sites of NodeBs and the installation space of the antennais limited in urban areas, so we recommend dual polarization antennas.

Horizontal beam width

In order to better control the coverage range of cells to suppress interference, forurban 3-sector sites, we recommend directional antennas with 60 ~ 65 horizontalbeam width. When the antenna gain and the horizontal beam width are determined,the vertical beam width is also determined.

Antenna gain

As large-distance coverage is not required in urban areas, we recommend antennaswith mid-high gain. Based on the currently available antenna types, we recommendantennas with 13 ~ 18dBi gain depending on the density of NodeBs and buildingstructures. Micro cell antennas in urban areas can be of 10 ~ 12dBi or lower gain.

Antenna downtilt

Select antennas with 6 fixed electrical downtilt angle (when the actual downtilt angleis < 6, it can be adjusted through mechanical uptilting). Meanwhile, the antennasupport should be mechanically adjustable within the range of 0 ~ 15. In such acase, there is a big possibility of capacity expansion. If the cell splitting is adopted forcapacity expansion at late stages, adjustable electrical downtilt antennas can be

used. The antenna downtilt should be adjustable within the range of 0 ~ 10.



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Null filling and upper side lobe suppress

In urban areas, in order to reduce inter-cell interference, large downtilt angle isrequired sometimes. When the downtilt angle exceeds half of the width of the verticalbeam, we should consider the influence of the upper side lobe. We recommend

antennas with upper side lobe suppression and null filling characteristics. Front-to-back ratio

In urban areas, interference control is a key issue, so there is a strict requirement onthe front-to-back ratio of antennas. We recommend antennas with a front-to-backratio of 25dB or higher.

Recommendation: Working frequency at 1710 ~ 2170 MHz / 45 dual polarization /65 horizontal beam width / 15 dBi gain / fixed 6 electrical downtilt or 0 ~ 10electrically controlled downtilt and 0 ~ 15 adjustable mechanical downtilt / upper sidelobe suppression and null filling / 25dB or higher front-to-back ratio.

3.2 NodeB Antenna Type Selection for Suburb Coverage

Application environment characteristics: The application environment of the suburbsis between urban environment and rural environment. In some places, theenvironment is more close to the urban, where many NodeBs exist. In this case, weshould consider both coverage and interference control when selecting the antennatype. In some other areas, the environment is more close to rural areas, wherecoverage is an important factor. Therefore, the antenna type selection should becarried out depending on the actual situations for urban areas and rural areas.

Guidelines for Antenna Type Selection:


Based on the NodeB type design, select antennas with 65 or 90 horizontal beam

width. If NodeBs are densely distributed, the antennas should be selected inreference to antenna selection guidelines for urban areas; if NodeBs are sparselydistributed, and there is no big capacity expansion potential, the antenna selectionguidelines for rural areas can be used as reference.

Antenna downtilt

In general, fixed electrical downtilt antennas are not used. Even if downtilt is used, thedowntilt angle is generally very small.

Recommendation: Select the specific antennas by referring to antenna typeselection for urban areas and that for rural areas depending on the distance betweenNodeBs.

3.3 NodeB Antenna Type Selection for Rural Areas

Application environment characteristics: NodeBs are sparsely distributed, the traffic islow, and large coverage is required. In some places, single NodeB coverage isadopted. Coverage is the most important factor. Antennas should be selecteddepending on the coverage areas around the NodeBs.

Guidelins for Antenna Type Selection:

Working frequency

In order to reduce the number of antenna codes, select exclusively widebandantennas that work at the 1710 ~ 2170 MHz band.

Polarization type



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Buildings in rural areas are relatively low and sparsely distributed. The polarizationeffect of electric waves is not obvious, so we recommend vertical polarizationantennas.


If a NodeB is required to cover the surrounding area without obvious directionality,and the traffic is dispersedly distributed around the NodeB, we recommend an omniantenna For an omni site, because the antenna gain is small, the coverage radius isnot as far as that of a directional one. If the operator requires a longer coveragedistance, directional antennas should be selected. In rural areas, we recommenddirectional antennas with 90 horizontal beam width; for special landforms, werecommend landform matching antennas.

Antenna gain

Antenna gain should be selected depending on the coverage requirement. In ruralareas, we recommend omni antennas with 11dBi gain or directional antennas with18dBi gain.

Antenna downtilt

In rural areas, there is little requirement for downtilt adjustment, both in theadjustment range and characteristics, so we recommend mechanical downtilt.

Null filling

If the antenna height is over 50 meters and near-end coverage is required, theantenna with null filling is recommended.

Recommendation (for directional antennas): Working frequency 1710 ~ 2170 MHz/ vertical polarization / 90 horizontal beam width / 18 dBi antenna gain / 0 electricaldowntilt / null filling

Recommendation (for omni antennas): Working frequency 1710 ~ 2170 MHz /vertical polarization / 11 dBi antenna gain / 0 electrical downtilt / null filling

3.4 Antenna Type Selection for Highway Coverage

Application environment characteristics: Low traffic, high-speed moving subscribers;the key point is coverage. High way coverage is mainly belt-shape coverage, so dual-sector or 8-shape omni antennas can be used; in places where the highway runsthrough towns or scenic spots, 3-sector or heart-shape omni antennas can be used.


Polarization type

For highway coverage, we recommend vertical polarization antennas.

Horizontal beam widthFor coverage of railroads and highways, in case of S0.5/0.5 NodeB typeconfiguration, use directional antennas with high gain and 30~33 horizontal beamwidth; in case of O1 NodeB type configuration, use 8-shape antennas with dual 70horizontal beam width.For NodeBs used to cover highways and the towns along highways, select heart-shape antennas or omni antennas with horizontal beam width of 210 ~ 220.

Antenna gain

In case of directional antennas, select 21 ~ 22dBi high-gain antennas; in case of omniantennas, select 11dBi gain antennas; in case of 8-shape antennas, select 14dBi gainantennas; in case of heart-shape antennas, select 12dBi gain antennas.

Antenna downtilt

For places where highway coverage is considered mainly, we recommend antennas



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with 0 electrical downtilt angle.

Null filling

If the height of antenna is over 50 meters and near-end coverage is required, theantenna with null filling is recommended.

Recommendation (for directional antennas): Working frequency 1710 ~ 2170 MHz/ vertical polarization / 30 horizontal beam width / 21 dBi antenna gain / 0 electricaldowntilt angle / null filling

Recommendation (for 8-shape antennas): Working frequency 1710 ~ 2170 MHz /vertical polarization / dual 70 horizontal beam width / 14 dBi antenna gain / 0electrical downtilt angle / null filling

Recommendation (for heart-shape antennas): Working frequency 1710 ~ 2170MHz / vertical polarization / 210 horizontal beam width / 12 dBi antenna gain / 0electrical downtilt angle / null filling

For highway and railway coverage, we recommend S0.5/0.5 NodeB configuration with

high-gain directional antennas or O1 NodeB with 8-shape antennas to avoidhandover of high-speed moving subscribers under towers.

3.5 Antenna Type Selection for Rural Coverage

Application environment characteristics: In remote hilly and mountainous areas, dueto serious obstruction of mountains, the propagation attenuation of theelectromagnetic wave is very large, so it is difficult to cover such as areas. Commonsituations are as follows: NodeB sites in basin areas, NodeB sites on high mountains,NodeB sites at mountainside and NodeB sties in common mountainous areas. ForNodeB sites at the center of a basin area, if the basin area is not large, werecommend omni antennas; if the basin area is very large or coverage of a trunk road

that runs through the basin is to be considered, we recommend directional antennas.Restricted by microwave transmission sometimes, a NodeB site must be located on arather high hill. In this case, the antenna will be over 150 meters above subscriberdistribution. If the target area of coverage is near the foot of the hill, an omni antennawith fixed electrical downtilt angle is required to avoid the tower-bottom shadoweffect. In case of a NodeB site at the mountain side, the antenna elevation is lowerthan the mountain top, and it is impossible to cover the other side of the mountain.Therefore, a directional sector antenna with wide beam width should be used to coverthe valley.


Polarization mode

For mountainous area coverage, we recommend vertical polarization antennas. Horizontal beam width

In case of directional antennas, 90 horizontal beam width is recommended.

Antenna gain

In case of omni antennas, 11dBi gain is recommended; in case of directionalantennas, gain of 15 ~ 18dBi is recommended.

Antenna downtilting and null filling

For NodeB sites on the mountains while the place to be covered is at the foot of themountains, antennas with the null filling and fixed electrical downtilt characteristicsare recommended. The fixed electrical downtilt angle depends on the relative heightof the antenna compared with the altitude of the coverage area. The bigger the

antenna relatively height is, the bigger the downtilt angle should be.



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Recommendation (for directional antennas): Working frequency 1710 ~ 2170 MHz/ vertical polarization / 90 horizontal beam width / 15 dBi antenna gain / fixedelectrical downtilt / null filling

Recommendation (for omni antennas): Working frequency 1710 ~ 2170 MHz /

vertical polarization / 11 dBi antenna gain / fixed electrical downtilt / null filling

3.6 Antenna Type Selection for Offshore Coverage

Application environment characteristics: Low traffic, wide coverage, good radiopropagation environment; for offshore coverage, the coverage distance is mainlyrestricted by the sphere curvature of the earth and the radio propagation attenuation.In view of the influences of the sphere curvature of the earth, antennas are usuallyinstalled at a high elevation (over 100 meters) for sea surface coverage.


Polarization type

For offshore coverage, we recommend vertical polarization antennas.


We do not recommend omni antennas. The horizontal beam width of directionalantennas should be selected depending on the coverage requirements.

Antenna gain

Because the required coverage radius is big, we recommend high-gain (over 18dBi)antennas.

Fixed electrical downtilting and null filling

For sea surface coverage, the antenna elevation is usually very high (over 100meters). Therefore coverage dead-zones are like to appear at the near end. We

recommend antennas with null filling. Meanwhile, for long-distance and widecoverage, we recommend antennas with 0 electrical downtilt angle.

Recommendation: Working frequency 1710 ~ 2170 MHz / vertical polarization / 30horizontal beam width / 21 dBi / with 0 electrical downtilt angle / null filling

3.7 Antenna Type Selection for Tunnel Coverage

Application environment characteristics: The traffic is not heavy, and interferencecontrol is almost not required. As it is rather difficult to install and maintain antennasinside tunnels, the large-sized antennas are not adopted in most cases. Leakingcables will be adopted for railroad tunnel coverage, which will not be discussed in this

section.

Guidelines of Antenna Type Selection:

Polarization type

Because the inner wall of tunnels and vehicles can repeatedly reflect signals, causingobvious polarization effect on electromagnetic waves, the coverage capability of avertical polarization antenna is similar to that of a 45 polarization antenna in atunnel. For installation inside tunnels, the antenna size and installation feasibilityshould be considered. We recommend vertical polarization log-periodical antennas(wideband) or Yagi antennas (narrowband). For installation outside the tunnelentrance, we recommend dual polarization plate antennas.


Due to obvious coverage directivity, narrow-beam directional antennas are usually



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used. The log-periodical antennas or Yagi antennas with 55 horizontal beam width orplate antennas with 30 horizontal beam width are recommended.

Antenna gain

We can select high-gain panel antennas (21dBi or higher), Yagi antennas (13~14dBi)

and log-periodical antennas (11 ~ 12dBi). The specific antenna gain can be selectedbased on the tunnel length.

Antenna size

For tunnel coverage, the antenna size is a critical factor. A specific coverage schemeshould be designed for each tunnel, and antenna installation feasibility should begiven due consideration. Select small-sized and easy-to-install antennas which meetthe gain requirement.

Recommendation: Working frequency 800 ~ 2200 MHz / vertical polarization / 55horizontal beam width / log-periodical antenna with 11.5 dBi (consider sharing withGSM/DCS).

3.8 Antenna Type Selection for Indoor Coverage

Application environment characteristics: At low stories of high buildings, signals areusually weak and there are even coverage-hole zones; at high stories of highbuildings, signals are in disorder, interference is serious and the call quality is bad.Most of underground facilities, like underground parking lots and underground stores,are coverage-hole zones.

Generally, indoor distribution systems are built to solve indoor coverage problems.With an indoor distribution system, NodeB signals are directly led in for various indoorareas through a wired network, and then the signal receiving and transmission areimplemented through various indoor antennas, so as to remove indoor coverage-hole

zones, suppress interference and provide good coverage for indoor subscribers.There is no receiving diversity or transmission diversity in an indoor distributionsystem. The antenna type selection depends on the design of the distributed system.Check the installability of the antennas and the coverage requirement, and selectaccordingly the antenna type and parameters.


Working frequency

In general, indoor distribution systems all involve antenna sharing requirement, so thecompatibility with forward (GSM/DCS) and backward (WLAN) should be considered inantenna selection. Therefore the antennas for indoor distribution systems should bewideband antennas (800 ~ 2500 MHz).For Green Field operators like China Telecom,wideband antennas are also recommended. An important reason is that DCS bandsafter clearing may be adopted in new mobile communications modes in the future.

Polarization type

Vertical polarization mode is adopted for indoor coverage.

Antenna type selection

Indoor antennas come in three types: ceiling-mounted omni antennas, platedirectional antennas, and high-gain directional antenna.

An omni antenna is installed in ceiling mounted way at the center of the room; a platedirectional antenna, applied in a rectangle environment, is installed on a single-sidedwall by the short edge of the rectangle; a high-gain directional antenna is applied in

the elevator well, and in general it is a log-periodical antenna.



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Antenna gain

Omni antenna: 2dBi; plate directional antenna: 7dBi; log-periodical directionalantenna: 11dBi.

Beam width

Omni antenna: 360 horizontal beam width and 90 vertical beam width; platedirectional antenna: 90 horizontal beam width and 60 vertical beam width; log-periodical antenna: 55 horizontal beam width and 50 vertical beam width.

Plate antenna unit: Different sizes are available, used in elevator pass ways,tunnels, subways and corridors respectively.

Recommendation (for omni antennas): Working frequency 800 ~ 2500 MHz /vertical polarization / 360 horizontal beam width, 90 vertical beam width / 2dBi gain.

Recommendation (for plate directional antennas): Working frequency 800 ~ 2500MHz / vertical polarization / 90horizontal beam width, 60 vertical beam width / 7dBigain.

Recommendation (for log-periodical antennas): Working frequency 800 ~ 2500MHz / vertical polarization / 55horizontal beam width, 50 vertical beam width /11.5dBi gain.



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Owj101107 Wcdma Rnp Antenna Type Selection Issue1.1

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