RF Planning and Optimization question

Here is few question about RF planning and optimization, All the questions were collected from recruiter. these questions are frequently asked in viva board.

1। What is the basic procedure for RF planning using RF planning tool in GSM?

Answer:

• Analyze the system requirement and plan for data acquisition.

• Select proper Planning Tool

• Loading of digital map data of planning area on the planning tool

• Model tuning for prediction of network on the planning tool

• Nominal cell planning for the coverage area

• Frequency planning and interference calculation.

• Final system planning.
  

2। What are the different types of antennas used in a GSM network?

Answer:

Antennas may be categorize based on antenna beam width and gain, In GSM we have

• Space diversity antenna

• Cross polarized antenna

• Omni directional antennas.

3। How do the power, orientation, beam width, tilt and height of the antenna affect the coverage?

Answer:

Power

Antenna output power, always proportional to the coverage area. So power increases coverage increases.

Proper Orientation

Orientation of an antenna gives us coverage on specific direction of desired planning area, Antenna orientation tuning is a major treatment when we prescribe for a network optimization.

Beam width and tilt

Antenna beam width and tilt improves the coverage of the planned area. Proper tuning of beam width and tilt gives better coverage and performance.

Antenna height

Increase in antenna height improves the coverage.

4। What is EIRP? How is it calculated?

Answer:

Effective isotropic radiated power is the total output power of Base station

EIRP=BTS Output power + Antenna gain – {cable losses - other (combiner) losses}

5। What is frequency planning? Why is frequency reuse pattern used?

Answer:

Frequency planning is to be done for the GSM network for a given operator with A set of GSM frequency band .Frequency reuse pattern is used for capacity planning and for effective resource utilization.

6। What are all the patterns available? How is frequency planning done on planning tool ?

Answer:

7/21 pattern, 4/12 pattern, 3/9 pattern ।Automatic frequency planning can be done with planning tool।

7। What is co-channel interference and adjacent channel interference?

Answer:

The interference caused by using same channels in a network is called co - channel interference and interference caused by adjacent channels of is called adjacent channel interference. To distinguish actual signal from interface minimum power difference should be -9db.

8। How do you minimize co-channel interference?

Answer:

• Proper frequency planning

• Proper reuse pattern.

• Physical parameter tuning (Orientation, Height, Beam width, tilt etc)

• Finally resource addition ( Frequency and New BTS)

9. How do you minimize adjacent channel interference?
Answer:

• Proper frequency planning.

• Physical parameter tuning (Orientation, Height, Beam width, tilt etc)

10. What is model tuning? Why is it used? Okarama Hatta model?

Answer:

Model tuning is done for any network using planning tool to obtain proper prediction about network.

As there will be difference in actual and predicted data for planning tool. One of the Model is Okarama Hatta Model, generally known as Hatta model, is widely used which considers the signal propagation losses.