60650895-Questions

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1. What are the optimization tools you use? Drive test, analysis, others?

2. Are System Information Blocks (SIB) transmitted all the time?

No, system information block is multiplexed with synchronization channel. Synchronization channel

occupies the first time slot (TS) and SIB occupies the other 9 time slots.

3. How does UE camp (synchronize) to a NodeB?

1. UE uses the primary synchronization channel (P-SCH) for slot alignment (TS synchronization).

2. After aligning to NodeB time slot, UE then uses secondary synchronization channel (S-SCH) to

obtain frame synchronization and scrambling code group identification.

3. UE then uses scrambling code ID to obtain CPICH, thus camping to a NodeB.

4. What could be the cause of soft handover failure?

y UE issue.

y Resource unavailable at target NodeB.

y Inadequate SHO threshold defined.o Etc.

5. What are the three sets in handover?

The 3 sets in handover are:

y Active set ± the list of cells which are in soft handover with UE.

y Monitored set ± the list of cells not in active set but RNC has told UE to monitor.o Detected set ± list of cells detected by the UE but not configured in the neighbor list.

6. What are the major differences between GSM and UMTS handover decision?

GSM:

y Time-based mobile measures of RxLev and RxQual ± mobile sends measurement report every SACHperiod (480ms).

o BSC instructs mobile to handover based on these reports.

UMTS:

y Event-triggered reporting ± UE sends a measurement report only on certain event ³triggers´.o UE plays more part in the handover decision.

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7. What are the events 1a, 1b, 1c, etc.?

y e1a ± a Primary CPICH enters the reporting range, i.e. add a cell to active set.

y e1b ± a primary CPICH leaves the reporting range, i.e. removed a cell from active set.

y e1c ± a non-active primary CPICH becomes better than an active primary CPICH, i.e. replace a cell.

y e1d: change of best cell.

y e1e: a Primary CPICH becomes better than an absolute threshold.o e1f: a Primary CPICH becomes worse than an absolute threshold.

8. What are event 2a-2d and 3a-3d?

Events 2a-2d are for inter-frequency handover measurements and events 3a-3d are for IRAT handover

measurements.

y e3a: the UMTS cell quality has moved below a threshold and a GSM cell quality had moved above athreshold.

y e3b: the GSM cell quality has moved below a threshold.

y e3c: the GSM cell quality has moved above a threshold.

y e3d: there was a change in the order of best GSM cell list.

9. What may happen when there¶s a missing neighbor or an incorrect neighbor? y Access failure and handover failure: may attempt to access to a wrong scrambling code.

y Dropped call: UE not aware of a strong scrambling code, strong interference.

y Poor data throughput.

y Poor voice quality.

y Etc.

10. What can we try to improve when access failure is high?

When access failure is high we can try the following to improve RACH performance:

y Increase maximum UE transmit power allowed: Max_allowed_UL_TX_Power.

y Increase power quickly: power_Offset_P0.

y Increase number of preambles sent in a given preamble cycle: preamble_Retrans_Max.y Increase the number of preamble cycles: max_Preamble_Cycle.

y Increase number of RRC Connection Request retries: N300.

11. What are the conditions you typically set to trigger IRAT handover?

RSCP and Ec/Io are used to trigger IRAT handover:

y RSCP -100dBm.

y Ec/Io -16dBm.

12. What are the typical KPIs you use to measure a network and what criteria?

y Access failure rate ( 2%).

y Call setup time (CS: over 95% of the time < 6-second for mobile-to-PSTN, 9-second for mobile-

mobile. PS: over 95% of the time < 5-second).y Dropped call rate ( 2%).

y BLER: over 95% of the blocks 2%.

y Average DL/UL throughput for PSD: 210kbps for loaded, 240kbps for unloaded.

13. What is the typical UE transmit power?

Varies ± most of the time below 0dBm.

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14. Have your used Ericsson TEMS? If so:

y Do you know how to create command sequence?

y What are the call sequences you typically have? CS long call, CS short call, PSD call, etc.

y What are the typical commands you have for CS and PS call?

y Do you regularly stop and restart a new log file? Why and when to stop and start a new file?

y How do you stop a log file? Stop command sequence first, wait and make sure all equipment are in idlemode before stop logging.

15. Did you work on neighbor prioritization?

16. What is the typical event sequence of IRAT Handover from 3G to 2G

y Event 2d ± entering into compressed mode ± measurement of 2G candidates ± Event 3a ± Verification of 2G resources ± Handover from UTRAN Command from 3G RNC to UE

17. What are the possible causes for an IRAT Failure?

y Missing 2G relations

y Non availability of 2G Resources

y Poor 2G Coverage

y Missing 3G Relations

18. What is Paging Success Ratio? What is the typical PSR that you have seen in a UMTS

network?

y PSR ± Paging Responses to the Paging Attempts

y About 90%

19. What are the possible causes for a lower PSR?

y Non-continuous RF Coverage ± UE going in and out of coverage area frequently

y Very High µPeriodic Location Update Timer¶ ± Keeping UEs in VLR long time after it moved out of coverage

y Lower Paging Channel Power

y Access Channel Parameter Issues

y Delayed Location Update when crossing the LA / CN Boundaries

20. What are the possible causes for a Drop Call on a UMTS network?

y Poor Coverage (DL / UL)

y Pilot Pollution / Pilot Spillover

y Missing Neighbor

y SC Collisions

y Delayed Handovers

y No resource availability (Congestion) for Hand in

y Loss of Synchronization

y Fast Fading

y Delayed IRAT Triggers

y Hardware Issues

y External Interference

21. A UE is served by 2 or 3 SC in AS. It is identifying a SC from 3rd

tier, Stronger and meets the

criteria for Event1a or Event1c. But SHO did not happen because of missing neighbor relations?

How do you optimize this issue?

y Study the Pilot spillover from the 3rd

Tier SC and control its coverage

y Even after controlling the coverage, if the spillover is there, Add the neighbor.

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22. A UE is served by 2 SC in AS, a SC is coming in to Monitored Set and Event1a is

triggered. But UE is not receiving Active Set Update from NodeB and the call drops. What could

be possible causes for this drop?

y Delayed Handover

y Loss of Synchronization

y Fast Fading

y Pilot Pollution / Spillover issues

23. What is Hard Handover in UMTS? When will it happen?

y Hard Handover in UMTS is a break before make type Handover

y It can happen in the inter RNC boundaries where there is no Iur link.

24. What is the typical Call Setup Time for a 3G UE to 3G UE Call? What are the possible RF

related causes for a delayed CST in this type of call?

y 6 to 9 seconds

y Multiple RRC Attempts (UE is on poor coverage ± need more than Access Attempt)

y Delayed Page Responsesy High Load on Paging and/or Access Channel

y Paging / Access Parameters

25. What is Soft Handover Overhead? What is the typical value in UMTS network?

y Soft Handover Overhead is calculated in two ways. 1) Average Active Set Size ± Total Traffic / PrimaryTraffic. 2) Secondary / Total Traffic

Typical Values are like 1.7 (Avg Active Set Size) or 35% (Secondary / Total )

26. What will happen to the Soft Handover Overhead when you apply OCNS on the network? And

Why?

y With OCNS, the interference (load) increases. This leads to reduction in Ec/Io of a Pilot, which reducesthe pilot spillovers. Reduction in Pilot Spillover will reduce the Soft Handover Overhead.

27. What are the possible causes for an Access Failure in UMTS?

y Missing Neighbors

y Poor Coverage

y Pilot Pollution / Spillover

y Poor Cell Reselection

y Core Network Issues

y Non ± availability of resources. Admission Control denies

y Hardware Issues

y Improper RACH Parameters

y External Interference

28. (FOR ERICSSON EXPERIENCED) What is RTWP? What is the significance of it? y Received Total Wide-band Power

y It gives the Total Uplink Power (Interference) level received at NodeB

29. (FOR ERICSSON EXPERIENCED) What is the System Reference Point at which all the Power

Levels are measured in Ericsson NodeB?

y System Ref Point for E/// NodeB is at the output of TMA (Between TMA and Antenna)

30. What are the typical values for µreportingrange1a¶ and µreportingrange1b¶?

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y 3 dB and 5 dB respectively.

31. What will be the impact when you change µreportingrange1a¶ from 3 to 4 dB and

µtimetotrigger1a¶ 100 to 320 ms, without changing any other parameters?

y Reduction in number of Event1a

y Delayed Event1a trigger

y Reduction in Average Active Set Sizey Delay in Event1a could increase DL interference, which could lead to a drop call or increase in Average

Power Per User (reduction in cell capacity)

32. What is Admission Control?

y Admission Control is an algorithm which controls the Resource Allocation for a new call and additionalresource allocation for an existing call. In case, if a cell is heavily a loaded and enough resources in termsof power, codes or CEs are not available, admission control denies permission for the additional resourcerequirement.

33. What is Congestion Control?

y Congestion Control monitors the dynamic utilization of specific cell resources and insures that overloadconditions do not occur. If overload conditions do occur, Congestion Control will immediately restrict

Admission Control from granting additional resources. In addition, Congestion Control will attempt to

resolve the congestion by either down switching, or terminating existing users. Once the congestion iscorrected, the congestion resolution actions will cease, and Admission Control will be enabled.

34. What is processing Gain?

Ans:- Processing gain is the ratio of chip rate over data bit rate, usually represented in decibel (dB) scale.

For example, with 3.84MHz chip rate and 12.2k data rate, the processinggain is:

PG12.2k = 10 * log (3,840,000 / 12,200) = 25dB

35. How to Calculate Max Numbers of Users in Cell?

Ans:- W: chip rate (for UMTS 3,840,000 chips per second)

EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)

i: other-cell to in-cell interference ratio (assuming 60%)

R: user data rate (assuming 12,200 kbps for CS-12.2k)

Ș: loading factor (assuming 50%)

Take 12.2kbps as example:

M = W / (EnNo * (1 + i) * R) * Ș = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 = 32.8

The number of users could also be hard-limited by OVSF code space. Take CS12.2k for example:

A CS-12.2k bearer needs 1 SF128 code.

Total available codes for CS-12.2k = 128 ± 2 (1 SF64) ± 2 (4 SF256) = 124.

Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.05 = 34 uers/cell.

36. What is Typical Gain of TMA?

Ans:- TMA typically has a 12 dB gain; however, the effective gain comes from noise figure reduction and

the gain is close or equivalent to the feeder loss

37. Definition RSCP,RSSI and Ec/Io

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RSCP: The ³Received Signal Code Power´ (RSCP) is the collected RF energy after the correlation /

descrambling process, usually given in dBm. Only this code power is of interest for the following receiver stages when judging on the quality of the reception.

Ec/Io: This is the ratio of the received energy per chip (= code bit) and the interference level, usually

given in dB. In case no true interference is present, the interference level is equal to the noise level.

Because of the system gain (see 1), the interference level can be higher than the wanted signal level.Therefore, at the coverage border, the value of Ec/I0 is usually negative

RSSI: The Received Signal Strength Indicator (RSSI) is a value that takes into account both RSCP and

Ec/I0. It is usually given in dBm and can be calculated as follows: RSSI [dBm] = RSCP [dBm] - Ec/I0

[dB]

38. What is SIR?

Ans:- SIR is the Signal-to-Interference Ratio ± the ratio of the energy in dedicated physical

control channel bits to the power density of interference and noise after dispreading.

39. Definition of pole capacity?

Ans:- The uplink noise increases with the loading exponentially. When the uplink noise approaches

infinity then no more users can be added to a cell ± and the cell loading is close to 100% and

has reached its ³pole capacity´.

Mathematically, to calculate the uplink pole capacity we need to know:

W: chip rate (for UMTS 3,840,000 chips per second)

R: user data rate (assuming 12,200 kbps for CS-12.2k)f: other-cell to in-cell interference ratio (assuming 65%)

EbNo: Eb/No requirement (assuming 5dB)

AF: Activity factor (assuming 50%)

Pole Capacity = (W/R) / ((1+f) * AF * 10^(EbNo/10)) = 120.6

To calculate the downlink pole capacity we also need to know:

Į: downlink channels orthogonality factor (assuming 55%)

Pole Capacity = (W/R) / ((1- Į +f) * 10^(EbNo/10)) = 64.06

40. Why open loop power control is needed and how it works?

Ans:- Open Loop power control is used when no feedback mechanism is possible. An estimate of therequired power is made from measurements and system information. This is used for initial networkaccess and finding initial ower settings during dedicated mode.

41. How does soft/softer handover work? Ans:- Soft/softer handover downlink: UE rake receiver performs maximum ratio combining, i.e. UE

combines multi-path signals and form a stronger signal.

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Soft handover uplink: RNC performs selection combining, i.e. RNC selects the better signal coming from

multiple NodeB.

Softer handover uplink: NodeB performs maximum ratio combining, i.e. NodeB rake receiver combines

signals from different paths and forms a stronger signal.

42. Why is there ³soft handover gain´?

Ans:- Soft handover gain comes from the following:

Macro diversity gain over slow fading.

Micro diversity gain over fast fading.

Downlink load sharing over multiple RF links. By maintaining multiple links each link could transmit at

a lower power, resulting in lower interference therefore a gain.

Advantages:

Overcome fading through macro diversity.

Reduced Node B power which in turn decreases interference and increases capacity.

Reduced UE power (up 4dB), decreasing interference and increasing battery life.Disadvantages:

UE using several radio links requires more channelization codes, and more resources on the Iub and Iur

interfaces.

43. What are Fast Fading and Slow fading? Ans:- Fast fading is also called multi-path fading, as a result of multi-path propagation. When multi-path

signals arriving at a UE, the constructive and destructive phases create a variation in signal strength.

Slow fading is also called shadowing. When a UE moves away from a cell the signal strength drops

down slowly.

44. What are fast fading margin and slow fading margin?

Ans:- To factor in the fast fading and slow fading, we need to have a margin in the link budget and they

are called fast fading margin and slow fading margin.

In link budget, the fast fading margin is usually set to 2-3; slow fading margin is set to 7-10.

45. 3G KPI

Ans:--3G KPI Introduction

KPI Category

Accessibility Analysis

The ability of a user to obtain a requested Accessibility service from the system.

Retainability

The ability of user to retain its requested service once connected for the desired duration.

Integrity The ability of a user to receive the requested service at desired quality.

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Mobility

The ability to provide the requested service to the user with mobility.

Availability

The percentage of time that a cell is considered available.

46. WCDMA KPI-ACCESSIBILITY ANALYSIS Ans:- ACCESSIBILITY ANALYSIS:

The ability of a user to obtain a requested Accessibility service from the system. These are the five steps to check Accessibility Analysis. We will see each of them in detail with parameter.

y RAN Capacity utilization Analysis and monitoring

y Transport and RNC Load Capacity utilization analysis and monitoring

y Audit Node B Hardware and License Capacity

y Consistency check RBS and RNC parameter

y Admission parameter adjustment

47. WCDMA KPI-RETAINABILITY ANALYSIS Ans:- RETAINABILITY ANALYSIS

The ability of user to retain its requested service once connected for the desired duration. Steps to Check Retainability Analysis

y Drop speech due to soft handover actions

y Drop speech due to missing neighbor

y Drop speech due to UL Synchronization lost

48. Why Ec/Io is negative?

Ans:- Pilot channel power is always less than the total cell power, the ratio of the Pilot power (Ec) to thetotal cell power (Io) is always less than one. Thus, when measured in decibels, the value of Ec/Io isalways negative.

Here is the calculation.

Ec = Effect energy Io = Total energy and noise.

Ec/Io = 10.log[Effect energy / (total energy+noise)] < 10.log(1) = 0 Ec/Io always negative

49. How many slots are there in a WCDMA Frame? How big is a frame in ms. how many chips are therein a slot?

WCDMA Frame is 15 slots wide. It is 10ms in length. There are 2560 chips in one slot. Chip rate is 3840Kc/sLength of frame = 10 msNumber of chips in a frame = 3840 *10=38400 chips.Number of chips in a slot = 38400/15= 2560 chips

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50. What is a typical CPICH power?CPICH power typically takes about 8~10% of the total NodeB power. For a 20W (43dBm) NodeB, CPICHis around 2W (35.1 ~ 33dBm).In urban areas where in-building coverage is taken care of by in-building installations, the CPICH maysometimes go as low as 5% because:1) The coverage area is small since users are close to the site, and2) More power can be allocated to traffic channels.

51. What is PICH and PCH?

Ans:- PICH-Paging Indicator Channel

PCH-Paging Channel

PICH is used to indicate UE to when it should read to S-CCPCH (Carries PCH) whereas PCH is used tocarry RRC Message ³Paging type 1´ which contains actual Paging information

52. Different Idle mode tasks UE performs Ans:- In Idle mode, the UE has no connection to the radio network Keeping UEs in Idle mode minimizesthe use of resources both for the UEs and in the network. However, the UEs must still be able to accessthe system and be reached by the system with acceptable delays. For this, the following procedures needto be performed:

y PLMN selection and reselection

y Cell selection and reselection

y Location Area (LA) and Routing Area (RA) updating

y Paging

y System information broadcast

53. Explain the functionality of TPC Ans:- During Power Control, Transmit Power control(TPC) commands are used to power up or power down based on SIR target in the step of 0.5 dB ( 1 dB if the connection is made over Iur).

54. How is Initial RACH Power is calculated?

Ans:- The initial power on the PRACH - the power of the first preamble - is determined according toequation.

P_PRACH = L_PCPICH + RTWP + constantValueCprach

Where L_PCPICH is the path loss estimated by UE since it knows transmit & receive CPICHpower RTWP is received Total Wideband Power(uplink interference) measured by RBS .Constant Value Cprach is used by the UE to calculate the initial power on the PRACH . This parameter

is configurable and decides at which level below RTWP preamble ramping will start.

55. How much power usually a Node B is allocated to control channels?

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The power allocated to control channels may depend on equipment vendor recommendation. Typically nomore than 20% of the total NodeB power is allocated to control channels, including CPICH. However, if HSDPA is deployed on the same carrier then the total power allocated to control channel may go up to 25to 30% because of the additional HSDPA control channels required.

56. How many time Inner Loop Power Control happens and what type of fading it compensates?

Ans: 1500 Hz and compensates Fast Fading

57. Power Control in WCDMA?

y Ans:- Open Loop

y Inner Loop

y Outer Loop

Open Loop Power control-The Open loop power control technique requires that the transmitting

entity measures the channel interference and adjusts its transmission power accordingly. This can

be done quickly, but the problem is that the interference estimation is done on the received signal, andthe transmitted signal probably uses a different frequency, which differs from the received frequency bythe system¶s duplex offset. As uplink and downlink fast fading (on different frequency carriers) do notcorrelate, this method gives the right power values only on average.Inner Loop-In this method the received signal-to interference ratio (SIR) is measured over a 667-

microsecond period (i.e., one time slot), and based on that value, a decision is made about whether toincrease or decrease the transmission power in the other end of the connection. Note that the delayinherent in this closed-loop method is compensated for by making the measurements over a very shortperiod of time. The transmit power control (TPC) bits are sent in every time slot within the uplink and thedownlink.There is not a neutral signal; all power control signals contain either an increase or decrease command.Outer Loop-The outer loop power control functions within the base station system, and adjusts the

required SIR value (SIRtarget), which is then used in the inner loop control. Different channel types,

which can be characterized by, for example, different coding and interleaving methods, constitute achannel¶s parameters. Different channel parameters may require different SIRtarget values. The finalresult of the transmission process can only be known after the decoding process, and the resulting qualityparameter is then used to adjust the required SIR value. If the used SIR value still gives a low quality bitstream, then the outer loop power control must increase the SIRtarget value. This change in the outer loop will trigger the inner loop power control to increase the mobile station transmission power accordingly.

Power control is necessary to keep the transmitted signal power level under control so as to minimize the

interference and keep the quality of signal to a desired level. The main functions are:

1. Closed-loop power control

(a) Outer-loop power control

- Uplink outer-loop power control

- Downlink outer-loop power control

(b) Inner-loop power control

- Uplink inner-loop power control

- Downlink inner-loop power control

2. Open-loop power control

(a) Uplink open-loop power control

(b) Downlink open-loop power control

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Closed-loop power control is the power control mechanism used in UMTS to solve near-far problem,

minimize interference and to keep the signal quality to optimum level. Closed-loop power control is used

in uplink (UL) as well as downlink (DL). However, the motive in both the cases are different. In uplink,

signals from different UEs reach NodeB with different power strength, thus causing the stronger signal

blocking the weaker one, resulting in near-far effect. In downlink, there is no near-far effect, but the UEs

near the cell-edge or in high interference region may need extra power to overcome the increased other

cell interference and weak signal due to Rayleigh fading.

Closed-loop power control can be divided into outer-loop and inner-loop power control. In case of uplink,

the RNC manages the outer-loop and Node B manages the inner-loop and for downlink, UE manages the

outer-loop and Node B manages the inner-loop.

Inner-loop power control (also called fast closed-loop power control), operates at 1500 times per sec

(1.5 kHz) [From where did this value of 1.5 kHz come from?

Answer: A UMTS 10 ms frame consists of 15 TPC commands. This results in a power control frequency

of 1500 Hz (15/10ms)] and relies on the feedback information from the opposite end of the link (or

channel) to maintain the signal to interference (noise) ratio to a target level set by the outer-loop power

control. The transmission power is increased or decreased by a certain fixed step size depending on

whether the received SIR is below or above the target SIR. Precise power control can lead to optimum

use of bandwidth resulting in increase cell capacity.

The UL inner-loop power control lets the UE adjust its output power in accordance with one or more TPC

commands received in the downlink direction. Remember the increase and decrease in power is limited

by upper and lower bounds as defined in 3GPP TS 25.101. The upper bound, i.e. UE maximum output

power, is set depending on the Power class of UE. This can also be set below the maximum capability of

the UE through signaling when the link is established. The lower bound, i.e. UE minimum output power

defined as the mean power in one timeslot (TS), and shall be less than -50 dB.

The DL inner-loop power control is used to control the transmission power of downlink channels at Node

B as per the TPC commands received from UE. However, in some situations Node B may ignore theincrease/decrease these TPC commands. For example, in case of congestion (high load scenario), the

Node B can ignore the TPC commands from UE.

Outer-loop power control is used to set the target quality value for inner-loop power control, i.e it adjusts

the target SIR in Node B which is used during inner-loop power control. Now the question is why do we

need to adjust the target SIR? Outer-loop power control tries to keep the quality of a connection to

desired value. Too high quality will waste the resources.

Open-loop power control is used to set the initial power of UE (in random access) and downlink channels.

The TPC commands used in inner-loop power control are relative, so it needs a starting point and this is

defined by open-loop power control. Also, this is useful in setting the power level in case of common

shared channels, where it is difficult to send each UE the necessary TPC commands. In case of uplink,

UE and broadcasted cell/system parameters are used to set initial access power on RACH. And in case

of downlink, the measurement report of UE is used to set the initial power of downlink channels.

The open loop power control tolerance is 9dB under normal conditions and 12dB under extreme

conditions.

57. What is the family of codes used for Chanelization in WCDMA?

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Ans:- Family of codes used for Chanelization in WCDMA used is Orthogonal Variable SpreadingFactor.(OVSF)

58. What is Significance of Eb_No? Ans:- Eb_No is related to QOS of a service which in terms related to bit error rate.

Technically it is the minimum signal to noise needed by infrastructure equipment after despreading it

signal. This is a value used to compare different infrastructure vendors. Eb_No changes with the service

type.

For AMR 12.2 is ~ 4db for Node B

For AMR 12.2 is ~ 8db for MS

59. Explain Timer T3212?

Ans:- Periodic LA and RA updating is used to notify the network of the UEs availability, and to avoidunnecessary paging attempts for a UE that has lost coverage and is not able to inform the CN that it isinactive.

The periodic LA update procedure is controlled by a timer, called t3212, which gives the time intervalbetween two consecutive periodic location updates. The value is sent by the WCDMA RAN to UEs on theBCCH.

60:- What is the processing gain for 384 Kb/s service? Ans:- Processing Gain= 10 log (Chip rate /Bit rate)

=10*Log(3840/384)=10*log (10)=10*1=10

61. What effect is there on signal by spreading and dispreading?

Ans:- Spreading will increase the bandwidth of a as signal. A signal of 10 Kb/s will become 40 Kb/s after spreading and will become 10 Kb/s after despreading. The processing gain term expresses the gainachieved by spreading a narrow band signal over a wideband spectrum.This gain is the ratio between the spreading chip rate and the actual service bit rate measured at the RLClevel.

61. What is typical pole capacity for CS-12.2, PS-64, PS-128 and PS-384?

Ans:- With same assumptions as above:

CS-12.2k: 120.6 (UL), 64.1 (DL).PS-64k: 34.8 (UL), 12.8(DL).PS-128k: 16.2 (UL), 8.4 (DL).PS-384k: 16.2 (UL), 2.8 (DL).PS-384k has only 128k on the uplink, therefore the uplink capacity is the same for both.

62. What do you understand by DRX cycle?

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Ans:- The UE listens to the PICH only at certain predefined times, reducing power consumption. Theperiodicity of these searches is set by the system and the time interval is called DiscontinuousReception (DRX) cycle.Different DRX cycles are used for circuit switched and packet switched services in Idle mode. A separateDRX cycle is also used to page Connected mode UEs in state URA_PCH.

63. What is cell selection criterion?

Ans:- Cell selection is based on:

y Qmean: the average SIR of the target cell.

y Qmin: minimum required SIR.

y P compensation: a correction value for difference UE classes.

S = Qmean - Qmin - Pcompensation

y If S>0 then the cell is a valid candidate.

y A UE will camp on the cell with the highest S.

64. Difference between PICH and PCH?

Ans:- PICH - Paging Indicator ChannelPCH-Paging Channel PICH is used to indicate UE to when it should read to S-CCPCH (Carries PCH)whereas PCH is used to carry RRC Message ³Paging type 1´ which contains actual Paging information.

65. When is System information sent to UE?

Ans:- The system information is regularly broadcast to the UE on the BCCH. When a parameter in thesystem information is changed, all UE in a cell are notified by a paging message or by a system

information change indication message.

66). Explain Soft and Softer handover? Give some advantage and disadvantage for soft handover

Ans:- In Soft Handover, the UE connection consists of at least two radio links established with cellsbelonging to different RBSs. In Softer handover, the UE connection consists of at least two radio linksestablished with cells belonging to the same RBS.It acts as macro diversity since UE is connected to more than one radio link at any given point, addsredundancy and reduces interference. However there is a tradeoff between soft/softer handover & systemcapacity.

A UE involved in Soft/Softer Handover uses several radio links, more DL channelization codes, and moreDL power than a single-link connection.Consequently, if all the UEs connected to a particular RNC are considered, more resources are needed in

the RBSs, more resources over the Iub and Iur interfaces, and more resources in the RNC. For thisreason, the number of radio links involved in the Soft/Softer handover must be limited.

67. How many types of handovers are there in UMTS?

Ans

Soft/Softer Handover

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Inter Frequency Handover

Inter RAT Handover

Core Network Hard Handover

Service based handover to GSM

HSDPA Mobility

68. What is Pilot Pollution?Simply speaking, when the number of strong cells exceeds the active set size, there is ³pilot pollution´ inthe area. Typically the active set size is 3, so if there are more than 3 strong cells then there is pilotpollution.

Definition of ³strong cell´: pilots within the handover window size from the strongest cell. Typical handover window size is between 4 to 6dB. For example, if there are more than 2 cells (besides the strongest cell)within 4dB of the strongest cell then there is pilot pollution.

69. Define Processing Gain for WCDMA?

Processing Gain is ratio between rate of spreaded signal and rate of non spreaded signal.

Processing Gain = 10 log (Chip rate /Bit rate)

70. Define Active Set? Pros and Cons of having a small or longer Active Set

Active Set consists of group of cells that takes part in soft/softer handover & measure by UE.Typical size of Active set is 3 or 4 & generally a standard practice in all WCDMA networks.

A small active set size may provide more resources available due to less soft/softer handover but at theexpense of handover gain thereby reducing the capacity & link redundancy.

71. WCDMA Handover Fundamentals GSM to UMTS Ans:- Learn about the differences between the GSM handover and the WCDMA handover -WCDMA handover decision algorithm

-WCDMA handover procedure -WCDMA handover parameters -WCDMA blind handover and directed retry

72. What is UE maximum transmit power in your link budget?

Ans:- UE Transmit Power limit is 21dBm.

73. What is a typical maximum path loss?-UMTS

Ans:- The maximum path loss is dependent on the service and vendor recommendations; typicallyit is in between 135 to 140dB for urban areas and between 150 to 160dB for rural areas

74. What is the difference between dB and dBm?

Ans:- dBm is a unit of power level, measured in milli-watts in logarithm scale, that is,

dBm = 10 * log(W*1000) where W is the power in Watts

dB is not a unit, it is the difference in dBm

75. What is Packet Loss?

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Ans:- Packet loss is the failure of one or more transmitted packets to arrive at their destination. This eventcan cause noticeable effects in all types of digital communications.

The effects of packet loss:

In data, packet loss produces errors.

In videoconference environments it can create jitter . In pure audio

LEARN MORE

y Network Performance Management

y Networking Resources communications, such as VoIP, it can cause jitter and frequent gaps in received speech. In the worst cases, packet loss can cause severe mutilation of received data, broken-up images,

unintelligible speech or even the complete absence of a received signal.The causes of packet loss include inadequate signal strength at the destination, natural or human-madeinterference, excessive system noise, hardwarefailure, software corruption or overburdened network nodes. Often more than one of these factors is involved.In a case where the cause can not be remedied, packet loss concealment may be used to minimize theeffects of lost packets.

76. What is Difference between ARQ and HARQ?

Ans:- ARQ (Automatic Repeat Request), which is used in UMTS, a package received in error will be

discarded and a retransmission will be requested. If the retransmission is also erroneous, another

retransmission will be requested.

Using HARQ, an erroneous package will be stored at the receiver and a retransmission will be requested.

Even if the retransmission is faulty, the receiver attempts to combine the two erroneous packages to

reproduce the original package.

77. What is a typical UE sensitivity level?

Ans:- The service and load determines the UE sensitivity; in general, in no-load condition, the sensitivity

is between -105dBm and -120dBm. For Ericsson, the UE sensitivity level is calculated at around:

CS12.2: -119 dBm

PS-64: -112 dBm

PS-128: -110 dBm

PS-384: -105 dBm

HSDPA: -95 dBm

78. What is a typical NodeB sensitivity level?

The service and load determines the NodeB sensitivity; in general, in a no-load condition, the sensitivity is

between -115dBm to -125dBm. For Ericsson, the NodeB sensitivitylevel is calculated at around:

CS12.2: -124 dBm

PS-64: -119 dBm

PS-128: -115 dBm

PS-384: -115 dBm

79. W hat is a typical NodeB maximum output power?-UMTS

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Ans:- The maximum NodeB output power is usually 20W or 40W, that is, 43dBm or 46dBm.

Also upto 100W

80. Why We have Different AMR Source rates: 12.2

(GSM-EFR), 10.2, 7.95, 7.40 (IS-641), 6.70 (PDC-EFR), 5.90, 5.15 and 4.75 kbps? Is there any benefit

to keep 7.95 and 7.40?

Ans:- We have different Source rates to compitable with current technology.

For example:7.4 kbps is equal to the US-TDMA speech codec.

6.7 kbps is equal to the Japanese PDC codec.

81.Facts about HSDPA:-

HSDPA represents an evolution of the WCDMA radio interface, which uses very similar methodsto those employed by EDGE (Enhanced Data Rates for GSM Evolution) technology for the GSMradio interface. The fundamental characteristics which enable the increase in the data throughputand capacity with reduced latency are summarised below:

y Time and code multiplexing of the users

y

Multi-Code transmission y Fixed Spreading Factor (SF = 16)

y Shorter TTI = 2ms

y No DTX (Discontinuous transmission)for the data channel

y Adaptive modulation and coding (AMC) supporting higher order modulation

y Node B scheduling and link adaptation

y Node B retransmissions (H-ARQ ± Hybrid Auotmatic Repeat-Request)

y No power control

y No soft handover

82. Explain HSPA(High Speed Packet Acess)?

Ans. High Speed Packet Access is a cobinatio of two mobile telephony High Speed Download Packet Access(HSDPA) & High Speed Upload Packet Access(HSUPA) that extends & imporves the peformance

of the WCDMA protocols

83. What is benefit of shorter TTI in HSDPA?

Ans:- 1) After every TTI the resources can be redistributed among the users. Therefore, the resource

usage is more efficient.

2) each UE reports about the channel quality after every TTI by sending the CQI.

3) CQI is sent after the very short period of time of 2 ms, it is possible to effectively perform link

adaptation even in rapidly changing conditions.

84. What are the main technologies used for HSDPA

Ans:- Main Technology

1) Link adaptation (AMC)

2) Fast Hybrid Automatic Repeat Request (HARQ), and

3) Shorter Transmission Time Interval (TTI)

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85. WHAT IS LATENCY IN HSDPA?

Ans:- Latency is the time a packet needs to travel from sender to receiver. While UMTS

typically features an end-to-end latency of approximately 200ms, HSDPA manages to lower the delay

times in transmission to around 100ms.

86. WHAT IS LINK ADAPTION?

Ans:- HSDPA uses link adaptation, which means the way of transmission is changed according to

the quality of the channel conditions.

If a user is in favourable conditions, for example close to the nearest antenna tower, this user will be

assigned a high data rate.

When the user moves into worse channel conditions, for example far away from the antenna tower, the

transmission parameters will be changed accordingly and thus the data rate will be decreased.

87. Brief describe the advantages and disadvantages of soft Handover ?

Ans:- Advantages:

Overcome fading through macro diversity.

Reduced Node B power which in turn decreases interference and increases capacity.

Reduced UE power (up 4dB), decreasing interference and increasing battery life.

Disadvantages:

UE using several radio links requires more channelization codes, and more resources on the Iub and Iur

interfaces.

88) What are the RRC states?

a. Cell DCH

b. Cell FACH

c. Cell PCH

d. URA PCH

89) Describe different RRC States?

a. Cell DCH:

When UE is switched ON, i t assumes the CELL_DCH State by default.

It exists when UE really requires UL/DL dedicated resource.

UE is characterized at cell level according to its current Active set.

Logical channels DCCH+DTCH are mapped to transport channel DCH.

E.g. Voice call(CS), Video telephony(CS+PS)

b.Cell FACH:

This happens when,

(1) UE doesn¶t require continuous circuit connection with n/w, but DL packets will work.

(2) UE is forced to release the n/w resources to decrease the congestion problems (flip-flop between

DCH and FACH).

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(3) Eventual location updates to support CELL_PCH and URA_PCH states (flip-flop between FACH and

PCH).

E.g. Call on hold(CS), File downloading(PS)

No dedicated UL/DL is provided. However, UE will keep monitoring to DL common transport channel

FACH µcontinuously¶ and receives packet data meant for UE itself.

When UL transmission is required, it uses RACH for 1-2 frames or CPCH for few more frames, depending

on common access procedures; still UL transmission will be µdiscontinuous¶.

UE is known on cell level, but this time it¶s based on the last cell update it made.

c. Cell PCH:

This happens when UE doesn¶t require an active connection(common/dedicated). But still needs to be

connected, as it¶s expecting a n/w initiated or terminated call(CS or PS) in future.

So, no UL transmission is allowed. Selects a PCH(based on algo.) and keep monitoring (receiving) it in

µdiscontinuous¶ mode(DRX).

Can commute only into CELL_FACH state.

E.g. No outgoing call or data receive for long time

UE is still identified on cell level, but now in the cell where UE made its last update, when it was in

CELL_FACH state. At regular time interval, UE would have to move in CELL_FACH state to update the location area. If UE is

traveling, this update will become frequent because of changing cells.

In some cases UE can have the transition from CELL_DCH to CELL_PCH, but not vice versa; it has to go

via CELL_FACH.

d.URA PCH:

This can be considered as a general case of CELL_PCH state. Because all the characteristics are same

except one.

That is, UE is known on URA(UTRAN Registration Area) level rather than cell level. It listens to PCH(and

updates URA when required).

If UE is traveling continuously from one cell to another. It would have to transit multiple time to

CELL_FACH state for location update. By assigning URA_PCH state, this condition is avoided, since 1

URA contains one or more cells and vice versa.

90) In which conditions UE will be in Cell FACH state?

This happens when,

UE doesn¶t require continuous circuit connection with n/w, but DL packets will work.

UE is forced to release the n/w resources to decrease the congestion problems (flip-flop between DCH

and FACH).

Eventual location updates to support CELL_PCH and URA_PCH states (flip-flop between FACH and

PCH).

E.g. Call on hold(CS), File downloading(PS)

91) What is the difference between Cell PCH and URA PCH state?

UE is known on URA(UTRAN Registration Area) level rather than cell level

If UE is traveling continuously from one cell to another. It would have to transit multiple time to

CELL_FACH state for location update. By assigning URA_PCH state, this condition is avoided, since 1

URA contains one or more cells and vice versa

92) What is U-RNTI?

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URNTI is a 32bit identity.

SRNC identifier + SRNTI makes URNTI

93) Describe the CELL search procedure?

The Cell Search procedure can be summarised into the following steps:

a.Cell Selection: Determine the cell whose received carrier power is the strongest

b.Slot Synchronisation: the UE reads the P-SCH of the strongest carrier and feeds the received signal

through a matched filter (that is matched to the Primary Synchronisation Code). The slot timing is

detected via detection of peaks in the output of the matched filter.

c.Frame Synchronisation and Scrambling Code Group Identification: the UE reads the S-SCH of the

strongest carrier, and correlates the received signal with all the possible 64 Secondary Synchronisation

Codes. The output that gives maximum correlation gives the group of the Primary Scrambling Code used

in the cell. This process also gives the frame timing since the Secondary Synchronisation Code is

different for each slot and the group tells the mapping between slots and SSCs.

d.Scrambling Code Identification: The UE attempts then to read the P-CPICH so as to extract the Primary

Scrambling Code used in the cell. The P-CPICH is always scrambled by the Primary Scrambling Code of the cell and is spread a factor 256 and an OVSF whose index is zero. Since the Primary Scrambling

Codes are grouped into 64 groups of 8 Scrambling Codes and the S-SCH has

given the Scrambling Code group only 8 possibilities remain. So the P-CPICH is unscrambled separately

withevery possible Scrambling Code (8) in the group and only one output will produce correct results and

the Primary Scrambling Code of the cell is determined.

e.Read Broadcast Information: Since the P-CCPCH is always scrambled by the Primary Scrambling Code

of the cell (which has now been determined) and is always spread using SF=256 with OVSF index=1,

The UE can read the P-CCPCH without any problem. The P-CCPCH carries the BCH where system

information blocks are broadcast throughout the entire cell. The UE can acquire at this stage various

information (e.g. Spreading Factors, OVSF indexes and Scrambling Codes used in other downlink

channels, important

parameters for PRACH transmission, Measurement Parameters, Transport Formats etc.) and can then

decodeother downlink channels, initiate a PRACH procedure, performs some specific measurements etc.

94 ) Radio bearer configuration mappings?

Signalling radio bearer RB0 shall be used for all messages sent on the CCCH (UL: RLC-TM, DL: RLC-

UM).

Signalling radio bearer RB1 shall be used for all messages sent on the DCCH, when using RLC

unacknowledged mode (RLC-UM).

Signalling radio bearer RB2 shall be used for all messages sent on the DCCH, when using RLC

acknowledged mode (RLC-AM), except for the RRC messages carrying higher layer (NAS) signalling.

Signalling radio bearer RB3 and optionally Signalling radio bearer RB4 shall be used for the RRCmessages carrying higher layer (NAS) signalling and sent on the DCCH in RLC acknowledged mode

(RLC-AM).

Additionally, RBs whose identities shall be set between 5 and 32 may be used as signalling radio bearer

for the RRC messages on the DCCH sent in RLC transparent mode (RLC-TM).

95) What are the types of hand over?

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Here are following categories of handover (also referred to as handoff):

Hard Handover

Hard handover means that all the old radio links in the UE are removed before the new radio links are

established. Hard handover can be seamless or non-seamless. Seamless hard handover means that the

handover is not perceptible to the user. In practice a handover that requires a change of the carrier

frequency (inter-frequency handover) is always performed as hard handover.

Soft Handover

Soft handover means that the radio links are added and removed in a way that the UE always keeps at

least one radio link to the UTRAN. Soft handover is performed by means of macro diversity, which refers

to the condition that several radio links are active at the same time. Normally soft handover can be used

when cells operated on the same frequency are changed.

Softer handover

Softer handover is a special case of soft handover where the radio links that are added and removed

belong to the same Node B (i.e. the site of co-located base stations from which several sector-cells are

served. In softer handover, macro diversity with maximum ratio combining can be performed in the Node

B, whereas generally in soft handover on the downlink, macro diversity with selection combining is

applied.

Generally we can distinguish between intra-cell handover and inter-cell handover. For UMTS the followingtypes of handover are specified:

Handover 3G -3G (i.e. between UMTS and other 3G systems)

FDD soft/softer handover

FDD inter-frequency hard handover

FDD/TDD handover (change of cell)

TDD/FDD handover (change of cell)

TDD/TDD handover

Handover 3G - 2G (e.g. handover to GSM)

Handover 2G - 3G (e.g. handover from GSM)

The most obvious cause for performing a handover is that due to its movement a user can be served in

another cell more efficiently (like less power emission, less interference). It may however also be

performed for other reasons such as system load control.

96) What are types of measurements?

Intra-frequency measurements: measurements on downlink physical channels at the same frequency as

the active set. A measurement object corresponds to one cell. Detailed description is found in subclause

14.1.

Inter-frequency measurements: measurements on downlink physical channels at frequencies that differ

from the frequency of the active set and on downlink physical channels in the active set. A measurementobject corresponds to one cell. Detailed description is found in subclause 14.2.

Inter-RAT measurements: measurements on downlink physical channels belonging to another radio

access technology than UTRAN, e.g. GSM. A measurement object corresponds to one cell. Detailed

description is found in subclause 14.3.

Traffic volume measurements: measurements on uplink traffic volume. A measurement object

corresponds to one cell. Detailed description is found in subclause 14.4.

Quality measurements: Measurements of downlink quality parameters, e.g. downlink transport block error

rate. A measurement object corresponds to one transport channel in case of BLER. A measurement

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object corresponds to one timeslot in case of SIR (TDD only). Detailed description is found in subclause

14.5.

UE-internal measurements: Measurements of UE transmission power and UE received signal level.

Detailed description is found in subclause 14.6.

UE positioning measurements: Measurements of UE position. Detailed description is found in subclause

14.7.

97) What is paging? Why paging is required?

Paging: This procedure is used to transmit paging information to selected UEs in idle mode, CELL_PCH

or URA_PCH state using the paging control channel (PCCH).

Paging can be initiated :

Upper layers in the network may request paging, to e.g. establish a signaling connection.

UTRAN may initiate paging for UEs in CELL_PCH or URA_PCH state to trigger a cell update procedure.

UTRAN may initiate paging for UEs in idle mode, CELL_PCH and URA_PCH state to trigger reading of

updated system information.

UTRAN may also initiate paging for UEs in CELL_PCH and URA_PCH state to release the RRC

connection.

98) Type of Paging?

Paging Type 1

Paging Type 2(UE dedicated paging)

12)When dedicated paging is used?

a.This procedure is used to transmit dedicated paging information to one UE in connected mode in

CELL_DCH , CELL_FACH or CELL_PCH (FDD only) state. Upper layers in the network may request

initiation of paging.

b.For a UE in CELL_DCH, CELL_FACH or CELL_PCH (FDD only) state, UTRAN initiates the procedure

by transmitting a PAGING TYPE 2 message on the DCCH using AM RLC. When not stated otherwise

elsewhere, the UTRAN may initiate the UE dedicated paging procedure also when another RRC

procedure is ongoing, and in that case the state of the latter procedure shall not be affected.

c.UTRAN should set the IE "Paging cause" to the cause for paging received from upper layers. If no

cause for paging is received from upper layers, UTRAN should set the value "Terminating ± cause

unknown".

99) In what situation UE goes to CELL PCH and URA PCH states?

a.Cell PCH:

This happens when UE doesn¶t require an active Connection(common/dedicated). But still needs to beconnected, as it¶s expecting a n/w initiated or terminated call(CS or PS) in future

b.URA PCH:

In Cell PCH UE is still identified on cell level, but now in the cell where UE made its last update, when it

was in CELL_FACH state.At regular time interval, UE would have to move in CELL_FACH state to update

the location area. If UE is traveling, this update will become frequent because of changing cells. If UE is

traveling continuously from one cell to another. It would have to transit multiple time to CELL_FACH state

for location update. By assigning URA_PCH state, this condition is avoided, since 1 URA contains one or

more cells and vice versa

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100) What is Monitor set and detected set Cells?

a.Cells, which are not included in the active set, but are included in the CELL_INFO_LIST belong to the

Monitored Set.

b.Cells detected by the UE, which are neither in the CELL_INFO_LIST nor in the active set belong to the

Detected Set. Reporting of measurements of the detected set is only applicable to intra-frequency

measurements made by UEs in CELL_DCH state.

101) What are the various types of RNC?

a.Serving RNC

b.Drift RNC

c.Controlling RNC

102) What is the use and difference between CRNC, Drift RNC and SRNC?

RNC from which the UE is currently getting Served or connected to is called SRNC or Serving RNC.

During a soft handover procedure the RNC UE is moving to, is called Drift RNC.

The RNC which controls the movement of UE from Serving RNC to the Drift RNC is called Controlling

RNC.

103) What is initial direct transfer message? What is the use?

The initial direct transfer procedure is used in the uplink to establish a signaling connection. It is also used

to carry an initial upper layer (NAS) message over the radio interface.

104) What is security mode command? Why it is used?

Security mode command is a RRC Message,

The purpose of this procedure :

To trigger the start of ciphering or to command the restart of the ciphering with a new ciphering

configuration, for the radio bearers of one CN domain and for all signalling radio bearers.

It is also used to start integrity protection or to modify the integrity protection configuration for all signalling

radio bearers

105) What is CCTrCH? (IMP)

A Coded Composite Transport Channel is the result of combining (multiplexing) several Transport

Channels of the same type; i.e.: we can have a CCTrCh made up of one or several DCHs, a CCTrCh

made up of DSCHs. One exception is that we can have one or several FACHs multiplexed with a PCH on

the same CCTrCh.

A better notation would be for example:

CCTrCh4DCH: A CCTrCh consisting of 4 DCHs

CCTrCh3FACH: A CCTrCh consisting of 3 FACHs

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CCTrChPCH,2FACH: A CCTrCh consisting of the PCH and 2 FACHs

106)What is compressed mode? (IMP)

Higher layers can request a UE to monitor cells on other frequencies (FDD, TDD), or other systems

(GSM). This implies that the UE has to perform measurements, on the other frequencies/systems and

thus higher layers command the UE to enter Compressed Mode. The UTRAN need to send to the UE all

the parameters for the Compressed Mode.

Compression Methods:

When in Compressed Mode the information normally transmitted during a 10 ms frame is compressed in

time so that gaps of adequate length are created. To achieve this one of three mechanisms

Puncturing

This method is NOT applicable to downlink.

Spread Factor Reduction

Actually halving the Spread Factor. So with this method if SF is used in non-compressed frames then

SF/2 is used in the compressed frames.

Higher Layer Scheduling

Higher Layers set restrictions so that only a subset of allowed TFCs are used in Compressed Mode.Compressed Mode Parameter:

TGSN (Transmission Gap Starting Slot Number): A transmission gap pattern begins in a radio frame,

called firstradio frame of the transmission gap pattern, containing at least one transmission gap slot.

TGSN is the slot numberof the first transmission gap slot within the first radio frame of the transmission

gap pattern;

TGL1 (Transmission Gap Length 1): Duration of the first transmission gap within the transmission gap

pattern, expressed in number of slots;

TGL2 (Transmission Gap Length 2): Duration of the second transmission gap within the transmission

gap pattern, expressed in number of slots. If this parameter is not explicitly set by higher layers, then

TGL2 =TGL1;

TGD (Transmission Gap Start Distance): Duration between the starting slots of two consecutive

transmission gaps within a transmission gap pattern, expressed in number of slots. The resulting position

of the second transmission gap within its radio frame(s) shall comply with the limitations of TS 25.101

(Ref [2]). If this parameter is not set by higher layers, then there is only one transmission gap in the

transmission gap pattern;

TGPL1 (Transmission Gap Pattern Length): Duration of transmission gap pattern 1;

TGPL2 (Transmission Gap Pattern Length): Duration of transmission gap pattern 2. If this parameter is

not explicitly set by higher layers, then TGPL2 = TGPL1.

The following two parameters (integers) control the transmission gap pattern sequence start and

repetition:

TGPRC (Transmission Gap Pattern Repetition Count): Number of transmission gap patterns within the

transmission gap pattern sequence; From Figure 10 it seems TGPRC is even, therefore the number of

slots in TG Sequence is: 0.5*TGPRC (TGPL1+TGPL2) TGCFN (Transmission Gap Connection Frame Number): CFN of the first radio frame of the first pattern

1 within the transmission gap pattern sequence.

107) What is FACH measurement occasion?

GAPs in S-CCPCH to perform measurement on Different Frequencies or Interrat resection.

108) Features of Rel99/Rel5/Rel6/7?

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Release '99

Bearer services

64 kbit/s circuit switched

384 kbit/s packet switched

Location services

Call services: compatible with Global System for Mobile Communications (GSM), based on Universal

Subscriber Identity Module (USIM)

Release 4

Edge radio

Multimedia messaging

MeXe levels

Improved location services

IP Multimedia Services (IMS)

Release 5

IP Multimedia Subsystem (IMS)

IPv6, IP transport in UTRAN

Improvements in GERAN, Mexe, etc

HSDPA

Release 6

WLAN integration

Multimedia broadcast and multicast

Improvements in IMS

HSUPA

109) MIB/SB/SIB details?

MIB: The Scheduling of MIB is Static.

110) What is Channelisation / scrambling?

Spreading is applied to the Physical Channels (except SCH). It consists of two distinct operations: a.

Channelisation and b. Scrambling

Channelisation is performed before scrambling.

Channelisation:

The term spreading is also used to refer to channelisation. Channelisation is the basis for Code DivisionMultiple Access (CDMA) encoding. This operation transforms every data symbol of a signal into a number

of chips. The bandwidth of the resulting signal occupies a much larger bandwidth typically 5 MGHz and

therefore the name Wideband-CDMA or W-CDMA. The number of chips per data symbol is called the

Spreading Factor (SF).

Scrambling:

111) When secondary scrambling code used?

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When there is any conflict with the Primary Scrambling code then Secondary Scrambling Code will be

used.

112) Why we perform Channelisation or spreading before scrambling?

Before sending a data we need to identify the channel to send the data. A particular Channelisation code

is the ³identity´ for the channel.

Hence we use Channelisation code to select the channel and then scramble it so as to send the identity

of the UE over the channel

113) When TMSI , P- TMSI , IMSI , IMEI used?

TMSI (GSM-MAP): The TMSI (GSM-MAP) shall be chosen if available. The IE "LAI" in the IE "Initial UE

identity" shall also be present when TMSI (GSM-MAP) is used, for making it unique.

P-TMSI (GSM-MAP): The P-TMSI (GSM-MAP) shall be chosen if available and no TMSI (GSM-MAP) is

available. The IE "RAI" in the IE "Initial UE identity" shall in this case also be present when P-TMSI (GSM-

MAP) is used, for making it unique.IMSI (GSM-MAP): The IMSI (GSM-MAP) shall be chosen if available and no TMSI (GSM-MAP) or P-

TMSI is available.

IMEI: The IMEI shall be chosen when none of the above three conditions are fulfilled.

114)What is Auto attached?

Auto Attach

Enabled

Disabled

When Power On

If

MNO I

It will perform a combined Attach

If NMOII

It will do a LAU and Attach.

If UE is Location updated i.e. SIM LAI is same as Cell LAI

Then it will do nothing.

If UE is not Location updated i.e.

SIM LAI differs from the Cell LAI then UE will perform Location Area Update

PS Call

Same RRC connection can be used for the PS call.

Will do a PS attach then the PS call.

115) Why we do a Combined Attach?

If the network operates in Network Mode Of Operation I i.e. NMO I and GPRS MS that operates in Mode

A or Mode B will do a simultaneous IMSI attach for GPRS and non GPRS services and shall use the

Combined GPRS attach, combined and periodic routing area updating procedures instead of the

corresponding MM specific procedures IMSI attach and normal and periodic Location area updating.

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116) Where CK and IK gets generated?

In RRC CK and IK gets generated.

117) Where CK and IK gets stored?

In USIM CK and IK will get stored.

118) Where the Security procedure will start?

Security Procedure will start in RRC but Ciphering will start for AM and UM data security procedure will

start at RLC layer. And for TM mode security procedure start at MAC layer.

119) What are the mandatory SIB¶s which UE has to read before campign?

SIB 1,3,5,7,11(It contains neighbor cell Information.)

120) What are the important RACH parameters and which SIB contains this information?

SIB 7/5

121) Which SIB contains S criteria information?

SIB 3

122) Which NAS message contains the information about Qos and where Qos is been decide on the

network side?

PDP context req.SGSN.

123) What is SHO and HHO? Which are the layers which are impacted with SHO and HHO?

SHO - RRC,L1

HHO ± L1

124) LAI and RAI structure and where is it broadcasted?

MNC+MCC+LAC=LAILAI+RAC=RAI

SIB 1.Need to check on MNC can be 2 bit also.

125) What is Multiple PDP and what is meant by Multi RAB and multi call?

2 PS - Multiple PDP

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PS+CS ± Multi RAB

2CS ± Multi Call.

126) Training WCDMA Handover Fundamentals GSM to UMTS

Training WCDMA Handover Fundamentals GSM to UMTS

Learn about the differences between the GSM handover and the WCDMA handover -WCDMA handover decision algorithm

-WCDMA handover procedure

-WCDMA handover parameters

-WCDMA blind handover and directed retry

127) What can we try to improve when access failure is high?

Ans:- When access failure is high we can try the following to improve RACH Performance

1.) Inc Maximum UE transmit power allowed: Max_allowed_UL_Tx_Power.

2.) Increase power quickly: power_Offset_P0.

3.) Increase number of preambles

128). What is Eb/No for requirement for HSDPA?

Ans:- It varies with user bit(data) rate , typically 2 for 768 kps & 5 for 2 Mbps.

129). What HS Channels are introduced in HSDPA in L1?

Ans:- HS-PDSCH-High Speed Physical Downlink Shared Channel

HS-SCCH-High Speed Shared Control Channel

130) How power control is implemented in HSDPA?

Ans:- Initial power is set in the same way as open loop power control of DCH & there is no further power

control on HSDPA shared channel HS-DSCH.The channel rate is controlled by adaptive modulation &

coding format.

The principle & functionality of the power control for the HSDPA associated dedicated channels are the

same as for the DPCH power control.

HS-DPCCH power is an offset relative to DPCCH depending upon whether the UE is in soft handoff or

not.

The power of HS-SCCH is fixed.

131). What fixed SF is used for HSDPA?

SF 16, maximum of 5 codes.

132). What do you understand by the CQI Measurements?

Ans:- Channel Quality Estimation for HSDPA sessions only. In order to aid scheduling & TFRC selection

in the RBS, the UE sends a channel quality indicator (CQI) report on the uplink. The CQI report estimates

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the number of bits that can be transmitted to the UE using a certain assumed HS-PDSCH power with a

block error rate of 10 %.

133) What type channel coding is used for the voice & data services?

Ans Voice-Convolution Coding

Data-Turbo Coding

134) What is the relationship of SF & data rate?

Ans) They are inversely proportional, Lower the SF higher the data rate.

135) What is the relationship of SF & power reuired?

Ans:- Lower SF more power required

136):- Idle Mode Behaviour is managed by System information send on which L3 Channel?

Ans:- BCH

137) How many Radio Bearers (RB) are involved in CS voice call?

3

138 ) How many Service Radio Bearers (SRB) are involved in CS voice call?

Ans:- 4

139) SCH channel consists of how many chips?

Ans) 256 Chips

140) Cell Reselection is valid in both Idle and in which Sate in Connected mode?

Ans:- CELL FACH

141) Explain Near far effect?

Ans:- All users use the same bandwidth at the same time and therefore users interfere with one another.

Due to the propagation path loss, the signal received by the base station from a UE close to the base

station will be stronger than the Signal received from another terminal located at the boundary. Hence,

the distant user will be dominated by the close user. This is called the near-far effect. To achieve a

considerable capacity, all signals, irrespective of distance, should arrive at the base station with the same

mean power. A solution to this problem is power control, which attempts to achieve the same mean

received power for each user.

142) How is Initial RACH Power is calculated?

Ans:- The initial power on the PRACH - the power of the first preamble - is determined according to

equation

P_PRACH = L_PCPICH + RTWP + constantValueCprach

Where L_PCPICH is the path loss estimated by UE since it knows transmit & receive CPICH power

RTWP is received Total Wideband Power(uplink interference) measured by RBS .

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constantValueCprach is used by the UE to calculate the initial power on the PRACH . This parameter is

configurable and decides at which level below RTWP preamble ramping will start.

143) What power RACH message Control Part is sent?

Ans:- The power of the control part of the RACH message is determined by the power of the lasttransmitted preamble and by a configurable offset power Offset Ppm.

144) However there is a tradeoff between soft/softer handover & system capacity?

Ans:- A UE involved in Soft/Softer Handover uses several radio links, more DL channelization codes, and

more DL power than a single-link connection. Consequently, if all the UEs connected to a particular RNC

are considered, more resources are needed in the RBSs, more resources over the Iub and Iur interfaces,

and more resources in the RNC. For this reason, the number of radio links involved in the Soft/Softer

handover must be limited.

A typical target for soft handover in WCDMA network is less than or equal to 30%

145) Which link is required to perform Inter RNC SHO?

Ans:- Iur

146). What is ³noise rise´? What does a higher noise rise mean in terms of network loading?

Answer - For every new user added to the service, additional noise is added to the network. That is, each

new user causes a ³noise rise´. In theory, the ³noise rise´ is defined as the ratio of total received

wideband power to the noise power. Higher ³noise rise´ value implies more users are allowed on the

network, and each user has to transmit higher power to overcome the higher noise level. This means

smaller path loss can be tolerated and the cell radius is reduced. To summarize, a higher noise rise

means higher capacity and smaller footprint, a lower noise rise means smaller capacity and bigger

footprint.

147) When in 3-way soft handover, if a UE receives power down request from one cell and power up

request from the other 2 cells, should the UE power up or down and why?

Ans. - UE will power down because if a cell is able to sustain a good connection with one cell on lower

power level it will discard power up messages from other cells. It also helps in maintaining low

interference level for other surrounding UE¶s.

148) Suppose two UE are served by the same cell, the UE with weaker link (poor RF condition) uses

more ³capacity´, why does this mean? Answer -The UE with weaker RF link will require NodeB to transmit higher traffic power in order to reach

the UE, resulting in less power for other UE ± therefore consumes more ³capacity

149) Under what circumstances can a NodeB reach its capacity? What are the capacity limitations?

Ans:- Node B reaches its maximum transmit power, runs out of its channel elements, uplink noise rise

reaches its design target, etc

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150) What is ³cell breathing´ and why?

Answer - The cell coverage shrinks as the loading increases, this is called cell breathing.

In the uplink, as more and more UE are served by a cell, each UE needs to transmit higher power to

compensate for the uplink noise rise. As a consequence, the UE with weaker link (UE at greater distance)

may not have enough power to reach the NodeB ± therefore a coverage shrinkage.

In the downlink, the NodeB also needs to transmit higher power as more UE are being served. As a

consequence UE with weaker link (greater distance) may not be reachable by the Node B.

151) . Is UMTS an uplink-limited or downlink-limited system?

Answer ± Initially, A typical WCDMA network is Uplink Limited. Later a Loaded Network becomes

Downlink Limites.

152) If you have 3 cells in your Active Set and a drop call occurs, which Cell a Drop call would be

pegged?

Answer - Serving Cell in Active Set

153) Briefly describe Capacity Management and its functions?

Answer - Capacity Management is responsible for the control of the load in the cell. It consists of 3 main

functions:

1. Dedicated Monitored Resource Handling: tracks utilization of critical resources of the system.

2. Admission Control: accepts/refuses admission requests based on the current load on the dedicated

monitored resources and the characteristics of the request

3. Congestion Control: detects/resolves overload situations

154) What Resources are monitored for Capacity Management?

Answer ±

*DL Power

*Received Total Wideband power

*OVSF Codes

*RBS Channel Elements

154) What Radio Measurements are used for Congestion Monitoring?

Answer ±

Downlink Received Power

Uplink Received Total Wideband Power

155) How is inter-frequency Handover triggered?

Answer ±

The network decides that inter frequency measurements need to be performed and sends the

MEASUREMENT CONTROL MESSAGE with Measurement type set to Inter-Frequency measurements.

Generally it will set an Event as well along with the measurements. The following are list of Events that

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can trigger Measurement Report.

Event 2a: Change of Best Frequency

Event 2b: The estimated quality of the currently used frequency is below a certain threshold and the

estimated quality of a non-used frequency is above a certain threshold

Event 2c: The estimated quality of a non-used frequency is above a certain threshold

Event 2d: The estimated quality of the currently used frequency is below a certain threshold

Event 2e: The estimated quality of a non-used frequency is below a certain threshold

Event 2f: The estimated quality of the currently used frequency is above a certain threshold

The Inter-Frequency Handover Evaluation bases its decision on P-CPICH quality measures on the

currently used frequency and on one or more non-used frequencies. If the evaluation result is positive,

one cell on a non-used frequency is proposed to Inter-Frequency handover Execution.

Inter-Frequency Handover is a hard handover where the UE is ordered by the network to tune to another

frequency. This means that there will be small interruptions in the data flow to and from the UE.

156) What kind of Handover takes place in Load Sharing?

Answer ±

It¶s a blind handover to the co-located cell. IFHO

157) What do you understand by Directed Retry?

Answer ±

When there is a co-existing GSM RAN, excess traffic in a WCDMA cell may be off-loaded to GSM

If a call is chosen for Directed Retry to GSM, the request for the speech RAB will be rejected with cause"Directed retry" and then a request is made to the core network to relocate the UE to a specific GSM cell,using the Inter-RAT handover procedure. This handover is a blind one since the target cell is chosen notbased on UE measurements. Therefore, the target cell must be co-located with the WCDMA cell. Co-located GSM cells are assumed to have similar coverage and accessibility as their respective WCDMAcells.

158.)What is HSDPA and how is it different from the current 3G/GPRS network available today?

HSDPA stands for High Speed Downlink Packet Access and is an evolution of 3G technology. It is

sometimes called 3.5G. HSDPA is a technology for improving the download performance of the current

3G network. It offers higher data transfer speeds, increased efficiency and greater system capacity for

operators.

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159.)What is HSUPA?

HSUPA stands for High Speed Uplink Packet Access, and improves the uplink performance in networks

which support HSUPA. 3G networks support a maximum of 384kbps on the uplink. HSUPA will support a

maximum of 1.9Mbps. The average uplink speed will be about 1Mbps.

160.)Do 3.5G/HSPA networks support Voice?

HSPA is purely a data network. All Voice traffic is supported on the current 3G network.

161.)What are the benefits of using 3.5G/HSPA for the end-user?

As a result of the enhancement, 3.5G/HSPA promises a better broadband multimedia experience. For the

business user, HSDPA enables high-speed Internet access and rapid download of emails with

attachments. For the consumers, HSDPA allows faster downloading of high-resolution digital images,

high-quality music downloads, Mobile TV, and mobile multi-player games.

162.)What do I need to enjoy the enhanced experience using 3.5G/HSPA?

To enjoy 3.5G/HSPA services, you will require a HSDPA-enabled phone and a 3G USIM.

163.)What is the maximum download speed of StarHub's 3.5G/HSPA network?

StarHub's 3.5G/HSPA network currently supports download speeds of up to 21Mbps, and upload speeds

of up to 5.76Mbps.

(Note: Actual bandwidth and speeds experienced are dependent on a combination of factors including the

mobile equipment, software used, internet traffic and destination server. Presently only the Mobile

Broadband Modem supports up to 21Mbps (download) and up to 5.76Mbps (upload). Most handsets

available today only supports HSDPA, with download speeds of up to 3.6Mbps and upload speeds of

384kbps.)

164.)What affects the download and upload speeds when using the HSPA service?

As with any network, the actual bandwidth experienced will have to take into account network and

protocol overheads and therefore the actual addressable bandwidth might be lower. In addition to this,

performance will also be affected by the following:

1. the mobile equipment that you are using and the bandwidth it supports

2. the websites and servers you are accessing

3. the types of Applications being used

4. the radio conditions

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5. level of congestion on the Internet

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