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Questions & Answers

3G RPFUN

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Chapter 1-WCDMA Fundamentals-

1. Explain the connection between spreading factor & bit rate.The higher the bitrate the lower the spreading factor

2. What is the meaning of processing gain?The ratio between the chip rate and user bit rate

3. Calculate the processing gain for 64 and 144 Kbit/s data service

4. How the radio resources can be described in the UMTS?

Transmission powerLogical codesBandwidth

5. What are the six functional entities of RRM?Power Control, Admission Control, Packet Scheduler, Load Control, Handover Control, Resource Manager

6. What is the main purpose of power control?To maintain radio link level quality by adjusting UL and DL Tx-powers

7. Explain the three different types of power controlOpen Loop: Used for initial UE Tx-power setting when accessing the network on RACHFast closed Loop: Maintaining SIR targets on DCH (UL & DL)Outer Loop: Setting SIR targets for fast closed loop PC

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Chapter 1-WCDMA Fundamentals-

8. What is controllable and non-controllable load?Controllable: NRT trafficNon-controllable: RT traffic, other cell users, noise, NRT traffic at min. bitrate

9. What is the function of admission control?Decides, based on the load situation, if a new RAB request is granted or not

10. What is the packet scheduler used for?Scheduling the radio resources for NRT traffic

11. Why DL scrambling codes need to be planned?To make sure cells are properly separated. How scrambling codes are assigned also affect cell search andsynchronization performance of the UEs

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Chapter 2-Radio Network Dimensioning-

What are the three different planning areas in 3G network planning?

Radio Planning, Transmission Planning, Core Planning

List the main characteristics of the WCDMA air interface which have to be taken carein radio planning

Noise Rise, UE speed, Cell Breathing, Interference, SHO areas,

Why is it important to have a realistic traffic model for doing dimensioning?

Because coverage and capacity are related to each other. E.g. dimensioning with too low traffic assumptionswill lead to coverage holes

List the three different groups of input parameters needed for RAN dimensioning

Capacity related, coverage related and quality related inputs

Describe the principle of cell range calculation in RAN dimensiong

Based on the planned load initial cell range is calculated. Planned load is compared to the actual load

generated in this cell. Iterations with decreased planned load or decreased cell range until actual and plannedload matches

What action should be taken in the iterative dimensioning process in case of coveragelimited scenario?

The system load should be decreased and the link budget calculated once again

What action should be taken in the iterative dimensioning process in case of capacitylimited scenario?

The new carrier can be added or cell radius decreased

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Chapter 2.2-Nokia WCDMA Base Station Family-

What is meant by ROC and CEC configuration?

ROC: All cells in one BS are sharing the same power amplifier. CEC: Each cell has its own PA.

What are the standard output powers per carrier for Nokia BS?

10, 20, 40W

How many carriers one power amplifier can handle, what is the limitation?

Max. 4, but must be within 20MHz band

What is meant by broadband antenna?

Antenna having a broad frequency range, e.g. covering GSM1800 and WCDMA

How many CEs are supported by Flexi Rel1 FSMB?

240

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Chapter 3-Link Budget Calculation-

List at least 3 WCDMA specific input parameters needed in power budget required Eb/N0 (per service)

SHO gain (MDC and plain)Interference marginPC headroom

What is the limiting factor for coverage calculation in UL and DL?

UL: UE transmit powerDL: Interference

Give a positive and a negative impact of soft handover. Because of SHO diversity gain less power per connection is needed, no interference peaks at cell

edge. SHO reserves additional BS resources and additional connections always means additionalinterference

Explain the meaning of interference margin.

The interference corresponding to a certain load value -> the cell range is calculated for a certainplanned load in order not to have sudden coverage holes due to cell breathing

Why is a power control headroom needed? To make sure a UE at the cell edge has enough Tx-Power left to follow fading dips.

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Chapter 4-Coverage & Capacity Planning-

What is the meaning of little i? The ratio between interference coming from neighbouring cells and interference caused in the own cell

Why needs power rise to be taken into account in UL load calculation?

Due to fast power control the average transmit power is higher than in a system without power control, thusadditional interference is caused by power control

How is UL load estimated in Nokia RRM?

UL load = 1 ( background and receiver noise / total received power )

How is UL noise raise calculated from load?

Noise rise = -10 log(1 UL load)

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Chapter 5-Coverage & Capacity Improvement-

How the Eb/N0 can be changed and what is its impact on the network? Eb/No's can be lowered by introducing Smart Radio Concept & Smart Antennas

The lower the required Eb/No's the higher the system capacityThe lower the required Eb/No's the larger the cell radii

How to increase the orthogonality of the network?

By avoiding multipath (antenna/site placing)

By micro cells implementationBy adaptive antennas or Smart Radio Concept

Explain how cell overlap affects capacity

To much cell overlap leads to higher interference and more SHO overhead, both reducing capacity

List three possibilities to improve UL coverage

6-sector site (higher antenna gain)Masthead amplifier

UL SRC (4-way Rx diversity)

What is the principle behind UL & DL SRC?

UL: Using the signal contributions of four Rx antennas instead of just two. More efficient use of multipathpropagation effect helps in coverage improvementDL: Using multiple Tx antennas. Better quality of the signal received by UE helps in capacity improvement

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Chapter 6-Planning Support for 3G Rollout-

Where are more than 90% of the radio parameters defined?

NetAct Plan Editor

What is the file format used between NetAct Planner and Plan Editor?

XML

Which feature of Plan Editor simplifies the generation of parameter sets?

Templates for AXC, WBTS and RNW

What is the name of the process for 3G Parameter Implementation? Why is ituseful?

LACE. Mass implementation, reduces cost and minimize errors.

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Chapter 7-Pre-launch Optimisation-

List 3 reasons for coverage holes Increasing traffic

Bad coverage planningInterferencesBuilding penetration loss

What can be measured with a WCDMA scanner?

CPICH coverage, SHO areas

List at least two SHO parameters which could be optimised

Addition Window, Drop Window, Active Set Size, Replacement Window,

What are the three golden rules for pre-launch optimization?

Avoid unnecessary cell overlapPut cell close to the usersMake sure there is coverage

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Chapter 8-WCDMA/GSMCo-siting-

What are the reasons for possible GSM-WCDMA interference? XMD

GSM1800: spurious emissions, Intermodulation (GSM1800 DL WCDMA UL)GSM900: spurious emissions, Harmonic distortion (GSM 900 DL WCDMA TDD, WCDMA FDD UL)

How much isolation is at least needed between GSM and WCDMA systems?

30 dB (Nokia), 50dB (others)

What is needed if shared antenna lines are used?

Diplexer / Triplexer

What is the most important thing being checked in network assessment and why?

Clear cell dominance areas

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Chapter 10-RAN Sharing-

In what areas RAN sharing is useful?

Areas with low predicted traffic

What does Multioperator RAN mean?

Two or more operators use one common RAN: RNC, transmission and BS are shared. Each operatorhas his/her own frequencies

Besides Multioperator RAN list three other possibilities to share a network

Network Sharing, one operator uses the network of another > MVNOGeographical Sharing, with national roamingSite Sharing, sharing site location, and possibly antenna system and site support systems

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Chapter 11-Multilayer Planning-

Why do microcells have higher capacity than macrocells?

Micro cells are better isolated from other cells -> lower interferenceMicro cells have better DL orthogonality due to less mutlipath propagation

What is happening during compressed mode?

In compressed mode transmission is interrupted in order to measure other frequencies or systems

In what situation an inter-system handover from WCDMA to GSM is performed?

No WCDMA Coverage

In what situation an inter-system handover from GSM to WCDMA is performed?

High Load on GSM

Give three possible layer solutions for a network using max. two WCDMAfrequencies.

One layer with two carriers

Two layers using same carrierTwo layers using different carriers