Antenna Selection Discussion

Radio Network Planning – Telkomsel

2006

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Objectives of Antenna Selections:

To optimize coverage for each class area by selecting suitable antenna

To improve quality by reducing interference causes by mismatch antenna usage.

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Antenna Parameters:

Important parameters in selecting antenna: Gain Horizontal Beamwidth (HBW) Vertical Beamwidth (VBW) Tilting system Working band Dimension and weight Others: Front to back ratio, VSWR, Isolation

between port, Intermodulation, polarization.

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Antenna Gain

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Antenna Gain:

Antenna gain is one of the most important thing in selecting antenna. Gain are related to desire cell coverage. When we calculate link budget, antenna gain is a variable to achieve cell range at signal level that we want.

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Antenna Gain:

How to calculate antenna gain: Link Budget Calculation

By using Okumura Hata formula with urban, suburban and rural correction factor Define CML required Define antenna height and cell range*Define required antenna gain

Planet Simulation (as comparison)By inputting parameter: EIRP, frequency, antenna height and simulate using model for each class area

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Antenna Gain:

Coverage Minimum Level (CML) Antenna Height Cell Range

Okumura Hata Formula

Path Loss

Required EIRP

Losses from BTS to antenna

Required Antenna Gain

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Antenna Gain:

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Antenna Gain:

Antenna height (m)

Antenna height was retrieve from existing network for each class area in 4 region (jabotabek, bandung, medan, surabaya)

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Antenna Gain: GSM 900GSM 900

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Antenna Gain: GSM 1800GSM 1800

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Antenna Gain: GSM 1800GSM 1800

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Antenna Gain:

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Tilting

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Tilting:

Control coverage border Reducing interference level due to

overshoot cells. Decrease bad null-fills effect of the

antenna

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Tilting:

Null Fill

Null-fill is intended to direct some additional energy toward theground. This fills the nulls in the pattern to cover areas below theantenna that otherwise might be sacrificed as energy is focusedtoward the horizon for maximum distance coverage.

Null fill

Null fill effect

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Tilting: Planet Simulation

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Tilting: Planet Simulation

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Tilting: Planet Simulation

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Tilting:

There are 3 type of tilting: Mechanical Tilt Electrical Tilt Variable electrical tilt

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Tilting:

Electrical tilt gift more interference reduction than mechanical tilt.

Overtilt mechanical tilt could possibly cause inteference between cells in one site

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Tilting:

Down tilting 4 degree is enough to reduce site to site interference without sacrificing coverage.

Bad null fill is reduce by tilting the antenna, therefore signal strength below the antenna is increase

Electrical tilt is better than mechanical tilt. Variable electrical is better than fixed electrical

tilt in term of flexibility of changing tilt

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Horizontal Beamwidth

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Horizontal Beamwidth:

Fulfilling coverage objective in the side lobe of the antenna.

Reducing coverage overlap between cells, in order to get lower BER, and interference level.

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Horizontal Beamwidth:

Horizontal Beamwidth:

Angle in the horizontal plane, where the antenna gain of the main lobe is not less than 3dB compared to the main direction.

Mostly used types:65°90°120°360°

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Horizontal Beamwidth:

These antenna patterns compare the overlap between 105°, 90° and 70°horizontal beamwidth antennas. Three 105° antennas have considerableoverlap. Reducing the beamwidth to 90° or 70° greatly decreases the overlapwithout losing much signal between sectors.

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Horizontal Beamwidth:

How to calculate required Horizontal beamwidth:Planet Simulation

By combining between signal strength predictions and coverage area, we could get signal strength distribution in those area.

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Horizontal Beamwidth:

Site to site distance

Coverage degradation due to beamwidth

Planet Calculation

Coverage below CML due to less beamwidth

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Horizontal Beamwidth: Based on planet calculation

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Horizontal Beamwidth:

With desire CML for dense urban, -68 dBm, site distance less then 1.5km, and antenna beamwidth 65 deg, it is still sufficient to cover the area until 95%.

As shown above, for site distance 2km and above there will be a coverage hole. It means that antenna beamwidth 65 deg is not sufficient for those site distance

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Horizontal Beamwidth: Based on planet calculation

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Horizontal Beamwidth:

With desire CML for dense urban, -69 dBm, site distance less then 1.5km, and antenna beamwidth 65 deg, it is still sufficient to cover the area until 95%.

As shown above, for site distance 2km and above there will be a coverage hole. It means that antenna beamwidth 65 deg is not sufficient for those site distance

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Horizontal Beamwidth: Based on planet calculation

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Horizontal Beamwidth:

With desire CML for dense urban, -76 dBm, site distance less then 5km, and antenna beamwidth 65 deg, it is still sufficient to cover the area until 95%.

As shown above, for site distance above 5km there will be a coverage hole. It means that antenna beamwidth 65 deg is not sufficient for those site distance

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Horizontal Beamwidth:

HBW dense urban = 65 degree HBW urban = 65 degree HBW suburban cell range < 2.5km = 65

degree HBW suburban cell range > 2.5km = 90

degree

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Vertical Beamwidth

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Vertical Beamwidth:

Degrees Above Horizon

0 dB-5 -3-13-18

-20

+20

-10

+10

0

Degrees Below Horizon

Vertical Beamwidth:

Angle in the vertical plane, where the antenna gain of the main lobe is not less than 3dB compared to the main direction.

typically: 6° - 30°

• Manufacturer: Sinclair Radio Laboratories• Vertical Beam Width:• Gain: 10dB

16°

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Vertical Beamwidth:

In Selecting Vertical beamwidth, we should consider the upper side beam which could cause interference to high rise building and interference along horizon. In Dense urban and urban should consider to use narrow beam.

In Hilly area, we should use wider beam to compensate fading.

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Thanks