Antenna Co Siting

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COSITING BETWEEN UMTS AND GSM SYSTEMS

Dr. Hatem MOKHTARI


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Dr. Hatem MOKHTARI, September 2004 Page 2/25

T A B L E O F C O N T E N T S

1. INTRODUCTION ......................................................................................................4

1.1. OBJECT .........................................................................................................4

1.2. SCOPE...........................................................................................................4

2. ABBREVIATIONS & DEFINITIONS .........................................................................4

2.1. ABBREVIATIONS...........................................................................................4

2.2. DEFINITIONS.................................................................................................4

4. INTERFERENCE MECHANISMS.................................................................................5

4.1 SYSTEMS AND BRAND TO BE CONSIDERED ................................................5

4.2 TYPES OF INTERFERENCES...........................................................................5

5. THEORETICAL CONSIDERATIONS............................................................................6

5.1 HYPOTHESIS FOR CALCULATION ..................................................................6

5.2 CO LOCATION BETWEEN GSM SITES AND UMTS SITES .............................7

5.2.1 WIDEBAND NOISE.................................................................................7 5.2.2 SPURIOUS EMISSIONS .........................................................................7 5.2.3 INTERMODULATIONS............................................................................8

Intermodulations generated by the transmitter.........................................8 Intermodulations generated by the transmitter.........................................8

5.2.4 BLOCKING..............................................................................................8

5.3 CONCLUSION....................................................................................................9

6. ANTENNA DECOUPLING POSITIONS......................................................................10

6.1 TESTED ANTENNAS...................................................................................10

6.2 TESTED POSITIONS...................................................................................11

6.2.1 HORIZONTAL SEPARATION..........................................................11 6.2.1.1 Basic horizontal separation ...................................................11 6.2.1.2 Horizontal separation with an azimuth divergence ................12

6.2.2 VERTICAL SEPARATION...............................................................13 6.2.2.1 Basic vertical separation .......................................................13 6.2.2.2 Vertical separation with different azimuths ............................14


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6.2.3 DOUBLE SEPARATION..................................................................15 6.2.3.1 Basic horizontal – vertical separation ....................................15 6.2.3.2 Horizontal - vertical separation with different azimuths .........16

7. MEASUREMENT SIGNAL .....................................................................................17

7.1 MEASUREMENT FREQUENCY IN TRANSMISSION BANDWIDTH...........17

7.2 MEASUREMENT FREQUENCY IN RECEPTION BANDWIDTH .................17

8. ANALYSIS OF THE RESULTS ..............................................................................18

8.1 COMMENTS....................................................................................18

8.2 HORIZONTAL SEPARATION WITH AZIMUTH DIVERGENCE...................18

8.2.1 COMMENTS....................................................................................18 8.3 BASIC VERTICAL SEPARATION................................................................19

8.3.1 COMMENTS....................................................................................19

8.4 VERTICAL SEPARATION WITH DIFFERENT AZIMUTHS .........................19

8.4.1 COMMENTS....................................................................................19

8.5 BASIC HORIZONTAL – VERTICAL SEPARATION .....................................20

8.5.2 COMMENTS....................................................................................20

8.6 HORIZONTAL-VERTICAL SEPARATION WITH A DIFFERENCE OF AZIMUTHS

OF 90 DEG...................................................................................................20 8.6.1 COMMENTS....................................................................................20

9 CONCLUSION........................................................................................................22

EXAMPLE...............................................................................................................25

END OF DOCUMENT ...........................................ERROR! BOOKMARK NOT DEFINED.



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1. INTRODUCTION

1.1. OBJECT

Colocation of UMTS sites with existing GSM-900 / GSM-1800 sites requires theevaluation of potential interference.

In the present document, the following points have been treated:

• First of all, the interference mechanisms due to system GSM/ UMTS

• Then a theorical study considers each of these latter phenomena and gives therequired isolation between GSM / UMTS

In order to evaluate this and deduce the necessary engineering rules, two kinds of

antennas characteristics has been studied:

Out of band radiation Decoupling between two antennas

In a first step, these two characteristics have been analyzed through measurements,

which was made with the help of a Research Center.

1.2. SCOPE

This document only considers the decoupling between GSM-900/UMTS, GSM-

1800/UMTS and Dual antenna/UMTS antennas in the UMTS band frequency. This

study is done on directive antennas.

2. ABBREVIATIONS & DEFINITIONS

2.1. ABBREVIATIONS

GSM : Global System for Mobile communications

DL : Downlink

UL : Uplink

UMTS : Universal Mobile Telecommunication System

2.2. DEFINITIONS

Antenna decoupling: Signal attenuation between two antennas.



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4. INTERFERENCE MECHANISMS

4.1 SYSTEMS AND BRAND TO BE CONSIDERED

Obviously, the more systems coexist in a confine zone, the more risky interference is.

Thanks to recommendations, it is possible to evaluate the potential jamming generated by one system on another one. In this document, we only consider the following

systems:

• GSM 900, R-GSM and GSM 1800

• UMTS FDD

The evaluation of interference in a system is related to the bands allocated to each

interfering and interfered system.

• The interfered BTS transmitting in in-band and out-band of its transmitting band(DL)

• The victim BTS receiving in in-band and out-band of its transmitting band.

The following tables gives the transmitting and receiving bands of GSM 900 R-GSM,

GSM 1800 and UMTS

GSM 900 R-GSM GSM 1800 UMTS

Receiving band 890-915 MHz 876-915 MHz 1710-1785 MHz 1920-1980 MHz

Transmitting band 935-960 MHz 921-960 MHz 1805-1880 MHz 2110-2170 MHz

4.2 TYPES OF INTERFERENCES

In the analysis of co-location, different interference mechanisms occur:

• Wideband noise

The wideband noise describes unwanted emissions outside the channel bandwith resulting from

the modulation process and non linearity in the transmitter but excluding the spurious emissions.

So, the jamming transmit part can generate wideband noise in the receive part and can raise the

noise level of this latter. Wideband noise depends on the frequency between the transmit carrier

and the receiving band.

• Spurious emissions

The spurious emissions are emissions, which are caused by unwanted transmitter effects such as

harmonics emissions, parasitic emissions, intermodulation products. So, the spurious emissions

issued from the transmit part can jam the receiver, as parasitic signal.

• Blocking

The receiver can be blocked by the normal transmitted carrier of the transmitter, which simply

means that reception can be disturbed in presence of a strong interfering signal.



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• Intermodulation products

Even if intermodulations products are above all spurious emissions, specifications consider this

type of interference in specific paragraph. Indeed:

-The transmitter can generate intermodulation products, which can fall in the receiver

band and cause jamming. However, since the transceiver is complying the recommendations, the

the intermodulation product will have a level below a certain limit: actually the GSM and UMTSrecommendations specify some tests to verify that the transmitter is able to restrict the

generation of interfering signals in its non linear elements.

- High signals, issued from the transmitter, can also induce intermodulation products

inside the receiver RF parts and cause degradation in reception. Maximum level of interfering

signals have been defined in recommendation, guaranteeing the good reception: actually, the

GSM and UMTS recommendations specify some tests to verify that the receiver is able to

receive a wanted signal despite the presence of two interfering signals, which have a specific

frequency relationship to the wanted signal.

These five mechanisms are the only one taken into account in the GSM and UMTSrecommendations. Actually, other phenomena might exist, but they are not controlled by any

rules. For example, electromagnetic compatibility problems may be encountered in a site

between:

- feeders- antennas- transceivers and receivers.

Any way these problems cannot be forecast and must be treated on site, case by case.

5. THEORETICAL CONSIDERATIONS

In this part we only consider the GSM recommendations and the UMTS recommendation to

calculate the necessary decoupling between:

- one GSM 900 system and one UMTS system- one R-GSM system and one UMTS system- one GSM 1800system and one UMTS system.

5.1 HYPOTHESIS FOR CALCULATION

The following configuration have been assumed for the calculation of the necessary isolation

between systems:

- As the channel bandwidths are differents in GSM and in UMTS, we prefer to use allthe signal power levels (GSM and UMTS) per Herz

- 43dBm output power (per carrier) is assumed to be at the antenna port of GSMBTS.



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- The noise figure of GSM BTS is assumed to be 4 dB, so k.T.F (thermal noisefloor +noise figure) is equal to –170 dBm/Hz

- 48 dBm output power for one carrier is assumed to be at the antenna port of UMTSBTS. It is the maximum output power we can have with the UMTS BTS,

considering a STSR configuration with 2 PA per sector at full power.

- The noise figure of GSM BTS is assumed to be 3.3dB so k.T.F (thermal noise +noise figure) is equal to –170.7dBm/Hz

- Within the receiving channel, there is no specification about the maximum level ofany signal disturbing the reception.

Meanwhile, it seems that the GSM spurious emissions level in the UMTS receiving band (new

GSM requirement) has been specified so that degradation at the UMTS receiver of 0.8dB has

been allowed. So, there is also the UMTS tolerable interference level at the antenna connector ao

that the degradation of the thermal noise floor + noise figure (k.T.F) of 0.8 dB is accepted.

- UMTS receiving channel:

Considering the k.T.F equal to –170.7 dBm/Hz, there will be a degradation of 0.8 dB of this

level if there is an interfering signal of –178dBm/Hz. It means that the maximum tolerable

interference level in the UMTS receiving channel is about –178dBm/Hz

5.2 CO LOCATION BETWEEN GSM SITES AND UMTS SITES

5.2.1 WIDEBAND NOISE

As the frequency separation between the GSM 900/ R-GSM band and the UMTS band and

between the GSM 1800 band and the UMTS band is large, we assume that the transmit part

(GSM 900 / R-GSM / GSM 1800) do not generate wideband noise in the receive part (UMTS).

This assumption is in compliance with the GSM 05.05, which only considers the modulation

spectrum (i.e wideband noise) up to 2 MHz either side of the transmit band.

5.2.2 SPURIOUS EMISSIONS

The GSM recommendation 05.05 specifies a maximum level of spurious emisssions in the

frequency band 1 – 12.5 GHz, including the UMTS receiving band. This maximum power

should not be greater than –30dBm at the base station RF output port, power measured in 3 MHz

bandwidth, what is equivalent to –95dBm/Hz

Note:

According to a new requirement added to the GSM 05.05 in july 2000, which considers the

colocation of GSM BTS with UMTS BTS the measured power of the spurious emissions within

the UMTS receiving band shall be no more than 96dBm over 100kHz, what is equivalent to –

146 dBm/Hz.To calculate the necessary isolation between antennas we keep the worst case which a spurious

emission of –95dBm/Hz.



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The difference between the maximum level of the spurious emissions and the maximum level of

interfering signal within the UMTS receiving channel gives the required isolation to guarantee to

avoid interference.

Jamming system Victim system

Tx UMTS Rx UMTSSpecified spurious emissions

over 3 MHz

-30 dBm

Specified spurious emissions per

HZ

-95dBm

Maximum level of unwanted

signal per Hz

-178 dBm

Necessary isolation between

antenna connectors

83 dB

5.2.3 INTERMODULATIONS

Intermodulations generated by the transmitter

The GSM 05.05 recommendation specifies that the power level of intermodulation products

when an interfering signal is injected into the antenna connector at a level of 30 dB lower than

that of the wanted signal, shall not exceed the spurious emissions requirements, i.e. –30dBm in

the UMTS receiving band at the base station RF outport, power measured in 3MHz bandwidth,

what is equivalent to –95dBm/Hz

It is the same level than the one specified for the spurious emissions, so we need the same

decoupling between antenna connectors.

Intermodulations generated by the transmitter

The UMTS TS 25.104 recommendation specifies a test to verify the receiver performance: the

reference sensitivity performance shall be met when two interfering signals, with a power equal

to –48dBm, are coupled to the UMTS BTS antenna connector.

5.2.4 BLOCKING

The UMTS TS 25.104 recommendation specifies that out-of-band, the maximum level ofinterfering signals (CW carrier) for blocking is equal to –15dBm.

The GSM power is assumed to be 43dBm at antenna connector. This power is over 200kHz,

rather than a CW interfering source as defined in TS 25.104.

Comparing this value to the blocking point, the necessary isolation between the two antennas

can be calculated.



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Jamming system Victim System

Tx GSM Rx UMTS

Transmit output power 43 dBm

Blocking point out of receiving

band

-15 dBm

Necessary isolation between

antenna connectors.

58 dB

5.3 CONCLUSION

The isolation required to protect UMTS from GSM interference is 83 dB. This value is very

high, it is explained by the fact that GSM standard was fixed without thinking about protection

of UMTS. (cositing UMTS /GSM has been taken into account in the UMTS standard and there

should not be problem of interference from UMTS in GSM Rx Band.)

This high value of 83dB concerns the BTS installed before july 2000, the BTS installed after this

date should comply with the new GSM recommendation which fix the level of spurious

emissions lower than –146 dBm/Hz, so the isolation required for this equipment is 32 dB.

Now all these calculations have been done only considering the GSM and UMTS

specification. But often, the products have better performances than these specifications. It

means that the necessary isolation to avoid any disturbance between systems will be

reduced. So it is important to get the real performances of the products.

The next part of the document is a study regarding the possibility to reach the necessary isolation

by antenna decoupling.



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6. ANTENNA DECOUPLING POSITIONS

6.1 TESTED ANTENNAS

The following set of antennas was considered :

In 900 MHz band :• directive crosspolar antenna, 65° horizontal aperture , 17 dBi max. gain:

named antenna900X

In 1800 MHz band :

• directive crosspolar antenna, 65° horizontal aperture , 17 dBi max. gain:named antenna1800X

Dual band 900 / 1800 MHz :

• directive crosspolar antenna, 65° horizontal aperture , 17 dBi max. gain:named dualantennaX

In UMTS band :

• directive crosspolar antenna, 65° horizontal aperture, 17 dBi max. gain:named antenna2000X

For the Dualantenna, two cases must be studied :

- GSM-900 transmission- GSM-1800 transmission

For the GSM-900 transmission case, the CW signal generator is connected to the GSM-

900 port, and for the GSM-1800 transmission case it is connected to the GSM-1800 port.



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6.2 TESTED POSITIONS

6.2.1 HORIZONTAL SEPARATION

6.2.1.1 Basic horizontal separation

The following mutual position was tested (figure 1):

d

Antenna 1 Antenna 2

d

ntenna 1 Antenna 2

front view top view

Figure 1 : Basic horizontal separation

Antenna 1 and 2 are the following ones and d varies in the following range :

Antenna 1 Antenna 2 d (m)Antenna900X Antenna2000X 0.5 1 1.5 2 2.5 3 3.5 4

Antenna1800X Antenna2000X 0.5 1 1.5 2 2.5 3 3.5 4

DualantennaX Antenna2000X 0.5 1 1.5 2 2.5 3 3.5 4

In that default case, both antennas are oriented in the same direction, perpendicular to

the axe of the study.

Measurements for distance lower than 0.5 m was not feasible due to the mechanical

aspects of the system.



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6.2.1.2 Horizontal separation with an azimuth divergence

The mutual position correspond to the previous separation distance, except that both

antennas are not oriented in the same direction (figure 2):

d

α

Antenna 1 Antenna 2

top view

Figure 2 : Horizontal separation with an azimuth divergence

Antenna 1 Antenna 2

(deg)

d (m)

Antenna900X Antenna2000X 30 0.5 1 1.5 2 2.5 3 3.5 4








DualantennaX Antenna2000X 30 0.5 1 1.5 2 2.5 3 3.5 4






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6.2.2 VERTICAL SEPARATION

6.2.2.1 Basic vertical separation

The following mutual position was considered (figure 3):

d

Antenna 2

Antenna 1

Figure 3 : Basic vertical separation

Both antennas are pointing in the same horizontal direction.

The distance d between the two antennas varies in the following range :

Antenna 1 Antenna2 d (m)

Antenna900X Antenna2000X 0.5 1 1.5 2 2.5 3

Antenna1800X Antenna2000X 0.5 1 1.5 2 2.5 3

DualantennaX Antenna2000X 0.5 1 1.5 2 2.5 3

In that case, both antennas are not tilted.

Measurements for distance lower than 0.5 m was not feasible due to the mechanical

aspects of the system.



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6.2.2.2 Vertical separation with dif ferent azimuths

The following mutual position was considered (figure 4):

d

Antenna 2

Antenna 1

Figure 4 : Vertical separation with different azimuths

Both antennas are pointing in their own direction separated by an angle α.

The distance d between the two antennas varies in the following range:

Antenna 1 Antenna 2 (deg) d (m)

Antenna900X Antenna2000X 90 0.5 1 1.5 2 2.5 3

Antenna1800X Antenna2000X 90 0.5 1 1.5 2 2.5 3

DualantennaX Antenna2000X 90 0.5 1 1.5 2 2.5 3

In that case, both antennas are not tilted.



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6.2.3 DOUBLE SEPARATION

6.2.3.1 Basic horizontal – vertical separation

This position is a combination of vertical and horizontal separation (figure 5).

d’

Antenna 2

Antenna 1

Figure 5 : Basic horizontal – vertical separation

Both antennas are pointing in the same direction, the d' axis study.

Antenna 1 Antenna 2 d (m) d' (m)

Antenna900X Antenna2000X 1.5 0.5 1 1.5 2 2.5 3 3.5 4








DualantennaX Antenna2000X 1.5 0.5 1 1.5 2 2.5 3 3.5 4


DualantennaX Antenna2000X 2.5 0.5 1 1.5 2 2.5 3 3.5 4DualantennaX Antenna2000X 3 0.5 1 1.5 2 2.5 3 3.5 4



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6.2.3.2 Horizontal - vertical separation with dif ferent azimuths

The mutual position correspond to the previous separation distance, except that both

antennas are oriented differently (figure 6) :

d

d’

Antenna 2

Antenna 1

d'

α

Antenna 2

Antenna 1

Figure 6 : Horizontal – vertical separation with different azimuths

Antennas are not tilted.

Antenna 1 Antenna 2

(deg)

d (m) d' (m)

Antenna900X Antenna2000X 90 1.5 0.5 1 1.5 2 2.5 3 3.5 4Antenna900X Antenna2000X 90 2 0.5 1 1.5 2 2.5 3 3.5 4

Antenna900X Antenna2000X 90 2.5 0.5 1 1.5 2 2.5 3 3.5 4

Antenna900X Antenna2000X 90 3 0.5 1 1.5 2 2.5 3 3.5 4





DualantennaX Antenna2000X 90 1.5 0.5 1 1.5 2 2.5 3 3.5 4

DualantennaX Antenna2000X 90 2 0.5 1 1.5 2 2.5 3 3.5 4

DualantennaX Antenna2000X 90 2.5 0.5 1 1.5 2 2.5 3 3.5 4

DualantennaX Antenna2000X 90 3 0.5 1 1.5 2 2.5 3 3.5 4



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7. MEASUREMENT SIGNALCW signal S at frequency f was entered at antenna 1 input and received at antenna 2

output (figure 7).

For crosspolar antenna, only one antenna 1 input was tested. Antenna 2 outputs were

both measured. Since antenna2000X is crosspolar, always two measurements were

done in reception.

Antenna 2

Antenna 1

Signal

generatorInput

S

S’

Network analyser

Figure 7

7.1 MEASUREMENT FREQUENCY IN TRANSMISSION BANDWIDTH

Frequency used for transmitting varies from 0.5 to 2.5 GHz.

7.2 MEASUREMENT FREQUENCY IN RECEPTION BANDWIDTH

At antenna 2 output, S’ is measured in UMTS frequency band.

As a consequence, when GSM frequency was used for transmission, measured

decoupling corresponds to :

- antennas separation attenuation

- band attenuation (antenna filtering effects)



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8. ANALYSIS OF THE RESULTS

8.1 COMMENTSThe results show that there is no difference between the S’ measurements when the

signal is taken from the output +45° and the signal measured at the output –45° of the

UMTS antenna.

Consequently, decoupling is independent on polarization aspects.

Only the signal measured at the +45° output port will be taken into account for the

following results.

8.2 HORIZONTAL SEPARATION WITH AZIMUTH DIVERGENCE

8.2.1 COMMENTS

Decoupling increases with the growth of the angle and the horizontal distance between the two antennas. This is due to basic separation distance effects.

The reason of the decoupling increase with the angle is that in every case theantenna 1 is a directive antenna. So, when angle exceeds 30 degrees, the radiation

from the antenna 1 to antenna 2 decreases.

We can notice that the decoupling between the UMTS antenna and GSM-900 antenna is the greatest.

Decoupling values for the dual antenna in case of GSM-1800 transmission and forthe GSM-1800 antenna are very closely.

The minimum decoupling measured for each antenna is in the case of 0.5mhorizontal distance and for the basic horizontal separation (corresponding to the

worst radiation case).

Isolation measured for the dual band antenna in case of GSM-900 transmission isroughly 10-15 dB below than the one of GSM-900 antenna.

The minimum and maximum decoupling for each antenna are noted in thefollowing table:

Antennas Min decoupling function of

the separation distance

Max decoupling function of the

separation distanceGSM 900 - UMTS 65 dB (α = 0°) 80 dB (α=0°) to 90 dB (α=120°)

GSM 1800 - UMTS 50 dB (α = 0°) 65 dB (α=0°) to 80 dB (α=120°)

Dualband - UMTS GSM-1800

50 dB (α=0°)

GSM-900

50 dB (α=0°)

GSM-1800

65 dB (α=0°) to

85 dB (α=120°)

GSM-900

70 dB (α=0°)

to 85 dB

(α=120°)



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8.3 BASIC VERTICAL SEPARATION

8.3.1 COMMENTS

S' decreases with the growth of the vertical distance between the two antennas. Thisis due to basic separation distance effects. Compared to horizontal separation,

higher decoupling is obtained thanks to limited antenna vertical radiation pattern.

The decoupling between the UMTS antenna and GSM-900 antenna is always thegreatest.

The minimum decoupling measured for each antenna is in the case of closedantennas.

There is no much gain to obtain in widely separating antennas: 10 dB from 0.5m to3m.


The minimum and maximum decoupling for each antenna are noted in the

following table:

Antennas Min decoupling (d=0.5m) Max decoupling (d=2.5m)

GSM 900 - UMTS 70 dB 80 dB


Dualband - UMTS GSM-1800

60 dB

GSM-900

65 dB

GSM-1800

65 dB

GSM-900

70 dB

8.4 VERTICAL SEPARATION WITH DIFFERENT AZIMUTHS

8.4.1 COMMENTS

Decoupling increases with the growth of the vertical distance between the twoantennas.


The comparison between the results of the basic vertical separation and of this position shows that the second position gives a better decoupling between the

antennas. This is due to radiation filtering in angles.

The minimum decoupling measured for each antenna is in the case of closed

antennas. Isolation measured for the dual band antenna in case of GSM-900 transmission is

roughly 10-15 dB below than the one of GSM-900 antenna.

There is no much gain to obtain in widely separating antennas: 10 dB from 0.5m to3m.


Antennas Min decouplig (d=0.5m) Max decoupling (d=2.5m)

GSM 900 – UMTS 70 dB 80 dB


Dualband – UMTS GSM-1800

60 dB

GSM-900

65 dB

GSM-1800

75 dB

GSM-900

75 dB



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8.5 BASIC HORIZONTAL – VERTICAL SEPARATION

The following figures (figure 19 to figure 22) shows the variation of S’ in function of

the horizontal and vertical distances between the two antennas. These two antennas are

oriented in the same direction (Figure 5 : ).

8.5.2 COMMENTS

Decoupling increases with the growth of the vertical distance between the twoantennas, but doesn't fluctuate very much with the horizontal distance. 1.5m vertical

distance is enough to reach basic attenuation. Between 0.5m and 1.5m horizontal

separation 10 dB are to gain, not more is expected.


Decoupling values for the dual antenna in case of GSM-1800 transmission and for

the GSM-1800 antenna are very closely. Isolation measured for the dual band antenna in case of GSM-900 transmission is

roughly 10-15 dB below than the one of GSM-900 antenna.


Antennas Min decoupling(d=0.5m) Max decoupling(d=3m)



Dualband – UMTS GSM-1800

60 dB

GSM-900

65 dB

GSM-1800

70 dB

GSM-900

70 dB

8.6 HORIZONTAL-VERTICAL SEPARATION WITH A DIFFERENCEOF AZIMUTHS OF 90 DEG

8.6.1 COMMENTS

Decoupling increases with the growth of the vertical distance between the twoantennas, but doesn't fluctuate very much with the horizontal distance.


Decoupling values for the dual antenna for the two cases of transmission and for theGSM-1800 antenna are very closely.

The comparison between the results of the basic horizontal – vertical separation andof this position shows that first position gives a better decoupling between the

antennas.

The minimum decoupling measured for each antenna is in the case of closedantennas.


1.5m vertical distance is enough to reach basic decoupling. Between 0.5 and 1.5mhorizontal separation 10 dB are to gain.



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Antennas Min decoupling

(vert. sepa. = 1.5m)

Max decoupling

(vert. Sepa.=3m)



Dualband - UMTS GSM-180060 dB

GSM-90060 dB

GSM-180070 dB

GSM-90070 dB



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9 CONCLUSIONThe decoupling between UMTS antenna and the others antennas is always higher than

50 dB, and increases with the distance between the antennas. The best decoupling is the

one between the GSM-900 and UMTS antenna, and the worst one is with the GSM-

1800 antenna.

We can deduce some position recommendations of each antenna for a decoupling

bandwidth from these measurements:

If a lower decoupling of 50-60 dB is needed, the horizontal separation is enough. If a minimum decoupling of 70-80 dB is required, a vertical separation is

recommended with a minimum separation of 1.5 m.

The association of a horizontal separation and a vertical separation doesn’t have agreat influence on the antenna decoupling.

To summarize, the minimum and maximum decoupling for each antenna are noted in

the following table:

α = azimuth difference

Position Antennas Min decoupling Max decoupling

GSM 900

- UMTS65 dB (α = 0°, hor.sep. = 0.5m)

80 dB (α=0°) to 90 dB

(α=120°) ( hor.sep.=4m)

GSM

1800 -UMTS

50 dB (α = 0°, hor.sep. = 0.5m)65 dB (α=0°) to 80 dB

(α=120°) ( hor.sep.=4m)

Horizontal

separation

with

azimuth

divergence Dualband

- UMTS

GSM-1800

50 dB (α=0°,

hor.sep. = 0.5m)

GSM-900

52 dB (α=0°,

hor.sep. = 0.5m)

GSM-1800

65 dB (α=0°)

to 85 dB

(α=120°)

(hor.sep.=4m)

GSM-900

70 dB (α=0°)

to 85 dB

(α=120°)

(hor.sep.=4m)

GSM 900

- UMTS70 dB (vert.sep.=0.5m) 80 dB (vert.sep.=3m)

GSM

1800 -

UMTS

55 dB (vert.sep.=0.5m) 65 dB (vert.sep.=3m)Basic

verticalseparation

Dualband

- UMTS

GSM-1800

60 dB

(vert.sep.=0.5m)

GSM-900

65 dB

(vert.sep.=0.5m)

GSM-1800

65 dB

(vert.sep.=3m)

GSM-900

70 dB

(vert.sep.=3m)

GSM 900

- UMTS70 dB (vert.sep.=0.5m) 80 dB (vert.sep.=3m)

GSM

1800 -

UMTS

60 dB (vert.sep.=0.5m) 75 dB (vert.sep.=3m)

Vertical

separation

with

azimuth

divergence Dualband

- UMTS

GSM-1800

60 dB(vert.sep.=0.5m)

GSM-900

65 dB(vert.sep.=0.5m)

GSM-1800

75 dB(vert.sep.=3m)

GSM-900

75 dB(vert.sep.=3m)



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GSM 900

- UMTS

70 dB (vert.sep.=1.5m,

hor.sep. = 0.5m)

85 dB (vert.sep.=3m,

hor.sep. = 4m)

GSM

1800 -

UMTS


hor.sep. = 0.5m)


hor.sep. = 4m)

Basic

horizontal

– vertical

separationDualband- UMTS

GSM-1800

60 dB(vert.sep.=1.5m,

hor.sep. = 0.5m)

GSM-900

65 dB(vert.sep.=1.5m,

hor.sep. = 0.5m)

GSM-1800

70 dB(vert.sep.=3m,

hor.sep. = 4m)

GSM-900

70 dB(vert.sep.=3m,

hor.sep. = 4m)

GSM 900

- UMTS


hor.sep. = 0.5m)


hor.sep. = 4m)

GSM

1800 -

UMTS


hor.sep. = 0.5m)


hor.sep. = 4m)

Horizontal

– vertical

separaion

with

azimuth

divergenceDualband

- UMTS

GSM-1800

60 dB

(vert.sep.=1.5m,

hor.sep. = 0.5m)

GSM-900

60 dB

(vert.sep.=1.5m,

hor.sep. = 0.5m)

GSM-1800

70 dB

(vert.sep.=3m,

hor.sep. = 4m)

GSM-900

70 dB

(vert.sep.=3m,

hor.sep. = 4m)

Using the above information, we can draw some guidelines to enable the engineer to

determine his antenna locations where other operators are already present.

Firstly, line of sight between antennas should be avoided. This can be achieved by

using available masks on the rooftop (eg. penthouse, chimney). Wall mounting the

antennas should be considered where possible. The design of the site should not

compromise its quality.

Secondly, where line of sight between antennas cannot be avoided, the engineer should

prioritize the vertical decoupling with or without azimuth divergence (there is a betterisolation with azimuth divergence) a minimum distance of 1 m between antennas is

needed.

If vertical decoupling is not possible then a vertical / horizontal decoupling should be

used with priority given to vertical decoupling which is much more effective than the

horizontal one (minimum vertical distance =1m).

The measurements regarding the Vertical + Horizontal decoupling were only done on

the GSM antenna’s axis.

GSM Antenna

GSM antenna

d’

UMTS antennaß

Axis X

Axis Y



24/25

The axis Y represents the axis where the GSM antenna gain is maximum, then the

isolation of a UMTS antenna place on this axe (0,Y) is lower than the isolation of an

antenna place on (X,Y) with X0.

Therefore the measurements on Horizontal + Vertical decoupling show the worse case,

where the attenuation is the lowest, in order to reach an higher isolation the engineer

should look for a relative azimuth (ß) between antenna higher than 0 degrees. However

the results of the measurements (figure 5) should be used as a base to calculate theattenuation.

α = 60

d’=1,5m

Zone C

Zone B

Zone A

GSM Antenna

For a minimum vertical distance d=1m,

we can define three horizontal zones:

with d’< d*1,5

Zone A: no restriction of distance and

azimuth.

Zone B: The antenna placed in this zone

must have an azimuth between 240 and

120 degrees (clockwise), assuming that

the GSM antenna is pointing north.

Zone C: No antenna should be placed in

this zone.

This rule should be applied within a

radius of 20m (no interference measured

beyond this point).

Thirdly horizontal decoupling alone should be chosen as a last option with a

minimum distance of 3m and an azimuth divergence if possible. Assuming that the

other operator is using a 65 degrees horizontal aperture antenna, the engineer has to put

his antenna away from +/- 60 degrees around the azimuth of the GSM antenna (orange

zone in the diagram below).

In the red zone no antenna should be placed within a radius of 3m

In the green zone, the azimuth must be as follows:

On the right hand side whilst looking from behind the antenna, and assuming that the

antenna is pointing at 0 degrees, the range in which you may place your antenna is

from 0 to 180 degrees, relative to the theoretical 0 azimuth. On the left hand side, it

may be placed in the range of 180 to 360 degrees also based on the theoritical azimuth.

-60 +60+90-90

There is no restriction in the white area.



25/25

EXAMPLE

d2

d1

distance d1>3m and an azimuth divergence

The GSM antennas are in white, first the

engineer should look for the verticaldecoupling solution. Then if it is not

possible the Vertical/Horizontal decoupling

should be chosen (blue antenna) with

minimum vertical distance = 1m.There is

no restriction on d2 since the UMTS

antenna is not in the main beam (+/- 60

deg) around the GSM azimuth.

Finally if the vertical decoupling alone is

not possible, the horizontal one should be

chosen oran e antenna with a minimum

(see restrictions above).

In this case the best decoupling can be

achieve by placing the UMTS antenna

( in red) as showed in the sketch.

If vertical decoupling can be used then

there is no restriction on d, otherwise,in case of horizontal decoupling alone,

d must be greater than 3m.

d

d

d

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