Interview Questions.

Question 1. What Are The Rrc States?

Answer :

Cell DCH
Cell FACH
Cell PCH
URA PCH
Question 2. Describe Different Rrc States?

Answer :

a. Cell DCH:

When UE is switched ON, it assumes the CELL_DCH State by default.
It exists whilst UE certainly calls for UL/DL dedicated resource.
UE is characterised at cell level in line with its modern Active set.
Logical channels DCCH+DTCH are mapped to move channel DCH.
E.G. Voice name(CS), Video telephony(CS+PS)
b. Cell FACH:

This occurs when,
UE doesn’t require continuous circuit connection with n/w, however DL packets will paintings.
UE is pressured to launch the n/w sources to lower the congestion problems (turn-flop among DCH and FACH).
Eventual region updates to guide CELL_PCH and URA_PCH states (turn-flop between FACH and PCH).
E.G. Call on preserve(CS), File downloading(PS)
No dedicated UL/DL is furnished. However, UE will preserve tracking to DL commonplace transport channel FACH ‘continuously’ and gets packet data intended for UE itself.
When UL transmission is needed, it uses RACH for 1-2 frames or CPCH for few more frames, relying on commonplace get admission to strategies; still UL transmission might be ‘discontinuous’.
UE is known on cell degree, however this time it’s primarily based at the final cellular replace it made.
C. Cell PCH:

This takes place when UE doesn’t require an lively connection(commonplace/committed). But still wishes to be connected, as it’s awaiting a n/w initiated or terminated name(CS or PS) in future.
So, no UL transmission is allowed. Selects a PCH(based totally on algo.) and preserve monitoring (receiving) it in ‘discontinuous’ mode(DRX).
Can go back and forth handiest into CELL_FACH kingdom.
E.G. No outgoing call or information get hold of for long term
UE is still recognized on mobile degree, but now in the cell in which UE made its final update, whilst it changed into in CELL_FACH kingdom.
At regular time c programming language, UE could must flow in CELL_FACH state to replace the place location. If UE is visiting, this replace turns into common because of changing cells.
In a few instances UE will have the transition from CELL_DCH to CELL_PCH, however not vice versa; it has to go thru CELL_FACH.
D. URA PCH:

This may be taken into consideration as a trendy case of CELL_PCH kingdom. Because all the characteristics are same except one.
That is, UE is known on URA(UTRAN Registration Area) level in preference to mobile level. It listens to PCH(and updates URA when required).
If UE is visiting continuously from one cellular to some other. It could must transit a couple of time to CELL_FACH country for area update. By assigning URA_PCH kingdom, this circumstance is averted, on the grounds that 1 URA incorporates one or extra cells and vice versa.
GSM Interview Questions
Question 3. In Which Conditions Ue Will Be In Cell Fach State?

Answer :

This takes place while,

UE doesn’t require non-stop circuit connection with n/w, however DL packets will work.
UE is forced to release the n/w sources to decrease the congestion issues (turn-flop among DCH and FACH).
Eventual area updates to support CELL_PCH and URA_PCH states (flip-flop among FACH and PCH).
E.G. Call on preserve(CS), File downloading(PS)
Question four. What Is The Difference Between Cell Pch And Ura Pch State?

Answer :

UE is understood on URA(UTRAN Registration Area) level in preference to cellular degree
If UE is journeying continuously from one cellular to another. It could should transit multiple time to CELL_FACH nation for area update. By assigning URA_PCH country, this circumstance is averted, considering 1 URA incorporates one or greater cells and vice versa
GSM Tutorial
Question 5. What Is U-rnti?

Answer :

URNTI is a 32bit identification.
SRNC identifier + SRNTI makes URNTI

UMTS Interview Questions
Question 6. Describe The Cell Search Procedure?

Answer :

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

Cell Selection: Determine the cellular whose received provider electricity is the most powerful
Slot Synchronisation: the UE reads the P-SCH of the strongest provider and feeds the received signal through a matched filter (this is matched to the Primary Synchronisation Code). The slot timing is detected thru detection of peaks inside the output of the matched filter out.
Frame Synchronisation and Scrambling Code Group Identification: the UE reads the S-SCH of the strongest service, and correlates the obtained sign with all the feasible sixty four Secondary Synchronisation Codes. The output that gives most correlation gives the group of the Primary Scrambling Code used within the cellular. This procedure also offers the frame timing since the Secondary Synchronisation Code is different for every slot and the institution tells the mapping among slots and SSCs.
Scrambling Code Identification: The UE attempts then to read the P-CPICH so one can extract the Primary Scrambling Code used inside the cell. The P-CPICH is constantly scrambled by means of the Primary Scrambling Code of the mobile and is spread a factor 256 and an OVSF whose index is 0. 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 viable Scrambling Code (eight) within the organization and simplest one output will produce accurate results and the Primary Scrambling Code of the cell is determined.
Read Broadcast Information: Since the P-CCPCH is always scrambled by way of the Primary Scrambling Code of the mobile (which has now been decided) and is always unfold the use of SF=256 with OVSF index=1, The UE can study the P-CCPCH without any trouble. The P-CCPCH contains the BCH in which device information blocks are broadcast in the course of the whole mobile. The UE can accumulate at this level numerous statistics (e.G. Spreading Factors, OVSF indexes and Scrambling Codes used in different downlink channels, important
parameters for PRACH transmission, Measurement Parameters, Transport Formats and many others.) and might then decodeother downlink channels, provoke a PRACH manner, performs a few precise measurements etc.

Question 7. Radio Bearer Configuration Mappings?

Answer :

Signalling radio bearer RB0 shall be used for all messages despatched at the CCCH (UL: RLC-TM, DL: RLC-UM).
Signalling radio bearer RB1 will be used for all messages despatched at the DCCH, whilst the use of RLC unacknowledged mode (RLC-UM).
Signalling radio bearer RB2 shall be used for all messages despatched at the DCCH, when the use of 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 will be used for the RRC messages wearing higher layer (NAS) signalling and despatched on the DCCH in RLC stated mode (RLC-AM).
Additionally, RBs whose identities shall be set between five and 32 may be used as signalling radio bearer for the RRC messages on the DCCH sent in RLC transparent mode (RLC-TM).
UMTS Tutorial 3G Interview Questions
Question 8. What Are The Types Of Hand Over?

Answer :

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

Hard Handover: Hard handover approach that all the antique radio hyperlinks in the UE are eliminated before the new radio links are installed. Hard handover may be seamless or non-seamless. Seamless difficult handover means that the handover is not perceptible to the person. In practice a handover that calls for a change of the provider frequency (inter-frequency handover) is constantly done as hard handover.
Soft Handover: Soft handover manner that the radio hyperlinks are added and removed in a way that the UE continually continues at least one radio link to the UTRAN. Soft handover is completed by macro variety, which refers to the circumstance that numerous radio links are active on the equal time. Normally gentle handover can be used when cells operated on the same frequency are changed.
Softer handover: Softer handover is a unique case of gentle handover in which the radio links which might be brought and eliminated belong to the identical Node B (i.E. The web page of co-located base stations from which numerous sector-cells are served. In softer handover, macro variety with maximum ratio combining can be accomplished within the Node B, whereas usually in soft handover on the downlink, macro variety with selection combining is applied.
Generally we are able to distinguish among intra-mobile handover and inter-mobile handover. For UMTS the following forms of handover are certain:
Handover 3G -3G (i.E. Among UMTS and different 3G structures)
FDD tender/softer handover
FDD inter-frequency hard handover
FDD/TDD handover (trade of mobile)
TDD/FDD handover (exchange of cell)
TDD/TDD handover
Handover 3G – 2G (e.G. Handover to GSM)
Handover 2G – 3G (e.G. Handover from GSM)
The most apparent reason for acting a handover is that because of its motion a consumer can be served in another mobile extra efficiently (like less power emission, less interference). It may additionally however also be performed for different motives along with gadget load manage.

Question 9. What Are Types Of Measurements?

Answer :

Intra-frequency measurements: measurements on downlink bodily channels on the same frequency because the active set. A dimension item corresponds to one mobile.
Inter-frequency measurements: measurements on downlink physical channels at frequencies that differ from the frequency of the lively set and on downlink bodily channels within the active set. A measurement object corresponds to at least one cell.
Inter-RAT measurements: measurements on downlink physical channels belonging to another radio get entry to generation than UTRAN, e.G. GSM. A size object corresponds to at least one mobile.
Traffic extent measurements: measurements on uplink traffic volume. A dimension object corresponds to 1 cell.
Quality measurements: Measurements of downlink fine parameters, e.G. Downlink shipping block error rate. A dimension item corresponds to at least one transport channel in case of BLER. A measurement object corresponds to one timeslot in case of SIR (TDD simplest).
UE-inner measurements: Measurements of UE transmission energy and UE acquired sign level.
UE positioning measurements: Measurements of UE function.
General Packet Radio Service (GPRS) Interview Questions
Question 10. What Is Paging? Why Paging Is Required?

Answer :

Paging: This method is used to transmit paging records to chose UEs in idle mode, CELL_PCH or URA_PCH country the use of the paging control channel (PCCH).

Paging can be initiated :

Upper layers in the community may also request paging, to e.G. Establish a signaling connection.
UTRAN may additionally provoke paging for UEs in CELL_PCH or URA_PCH state to trigger a cell update technique.
UTRAN may also provoke paging for UEs in idle mode, CELL_PCH and URA_PCH state to trigger analyzing of up to date device facts.
UTRAN may initiate paging for UEs in CELL_PCH and URA_PCH state to release the RRC connection.
General Packet Radio Service (GPRS) Tutorial
Question eleven. Type Of Paging?

Answer :

Paging Type 1
Paging Type 2(UE committed paging)
Adobe Edge Interview Questions
Question 12. When Dedicated Paging Is Used?

Answer :

This method is used to transmit devoted paging records to 1 UE in connected mode in CELL_DCH , CELL_FACH or CELL_PCH (FDD handiest) country. Upper layers in the community may request initiation of paging.
For a UE in CELL_DCH, CELL_FACH or CELL_PCH (FDD best) state, UTRAN initiates the system by using transmitting a PAGING TYPE 2 message on the DCCH the usage of AM RLC. When not stated in any other case elsewhere, the UTRAN might also initiate the UE dedicated paging system additionally whilst some other RRC manner is ongoing, and if so the state of the latter method shall not be affected.
UTRAN ought to set the IE “Paging motive” to the reason for paging received from upper layers. If no purpose for paging is obtained from top layers, UTRAN should set the fee “Terminating – motive unknown”.
GSM Interview Questions
Question 13. In What Situation Ue Goes To Cell Pch And Ura Pch States?

Answer :

Cell PCH: This occurs whilst UE doesn’t require an energetic Connection(common/committed). But nevertheless desires to be related, as it’s awaiting a n/w initiated or terminated name(CS or PS) in destiny
URA PCH: In Cell PCH UE remains identified on cellular stage, however now inside the mobile wherein UE made its closing replace, while it was in CELL_FACH nation.At everyday time c language, UE might need to circulate in CELL_FACH kingdom to update the region place. If UE is visiting, this replace will become common due to changing cells. If UE is visiting constantly from one cell to some other. It could have to transit more than one time to CELL_FACH state for area replace. By assigning URA_PCH state, this circumstance is averted, on the grounds that 1 URA consists of one or extra cells and vice versa
CDMA Tutorial
Question 14. What Is Cell Update Procedure? What Are Various Cell Update Causes?

Answer :

Uplink facts transmission:

For FDD, if the variable H_RNTI isn't set, and for TDD:

if the UE is in URA_PCH or CELL_PCH nation; and
if the UE has uplink RLC statistics PDU or uplink RLC manage PDU on RB1 or upwards to transmit: carry out cell update the use of the motive “uplink statistics transmission“.
Paging response:

if the criteria for appearing cellular replace with the reason specified above. Aren't met; and
if the UE in URA_PCH or CELL_PCH country, receives a PAGING TYPE 1 .Message pleasant the situations for initiating a cell replace method. Perform mobile replace the usage of the cause “paging reaction“.
Radio hyperlink failure:

if not one of the criteria for acting cell update with the causes particular above within the modern subclause is met:
if the UE is in CELL_DCH kingdom and the criteria for radio link failure are ,or
if the transmission of the UE CAPABILITY INFORMATION message fails. Carry out mobile update the use of the purpose “radio hyperlink failure“.
MBMS ptp RB request:

if not one of the standards for appearing cellular replace with the causes exact above inside the current subclause is met; and
if the UE is in URA_PCH, Cell_PCH or Cell_FACH kingdom; and
if the UE should carry out mobile replace for MBMS ptp radio bearer request, carry out cell update the use of the purpose “MBMS ptp RB request“.
Re-entering service place:

if not one of the standards for acting mobile update with the causes special above inside the modern subclause is met; and
if the UE is in CELL_FACH or CELL_PCH country; and
2> if the UE has been out of provider location and re-enters carrier region earlier than T307 or T317 expires:
3> carry out mobile update using the purpose “re-entering carrier location“.
RLC unrecoverable blunders:

if not one of the standards for performing cell replace with the causes detailed above within the cutting-edge subclause is met; and
if the UE detects RLC unrecoverable errors [16] in an AM RLC entity: perform cellular replace using the motive “RLC unrecoverable mistakes“.
Cell reselection:

if not one of the criteria for performing cellular update with the reasons targeted above inside the current subclause is met:
if the UE is in CELL_FACH or CELL_PCH state and the UE plays cell re-choice; or
if the UE is in CELL_FACH nation and the variable C_RNTI is empty: perform cell update the usage of the reason “cellular reselection“.
Periodical mobile replace:

if not one of the criteria for performing cell replace with the causes distinctive above inside the modern subclause is met; and
if the UE is in CELL_FACH or CELL_PCH country; and
if the timer T305 expires; and
if the criteria for “in carrier region” and
if periodic updating has been configured by way of T305 in the IE “UE Timers and constants in related mode” set to every other price than “infinity”: perform cellular update the usage of the cause “periodical cell update“.
MBMS reception:

if not one of the standards for performing cell update with the causes exact above within the cutting-edge subclause is met; and
if the UE is in URA_PCH, Cell_PCH or Cell_FACH kingdom; and
if the UE should perform mobile replace for MBMS counting , carry out cellular update using the purpose “MBMS reception“.
Question 15. What Is Active Set?

Answer :

Active Set is described because the set of Node-Bs the UE is concurrently connected to (i.E., the UTRA cells presently assigning a downlink DPCH to the UE constitute the active set).

CDMA Interview Questions
Question sixteen. What Is Monitor Set And Detected Set Cells?

Answer :

Cells, which are not covered inside the energetic set, but are covered in the CELL_INFO_LIST belong to the Monitored Set.
Cells detected with the aid of the UE, which might be neither in the CELL_INFO_LIST nor within the active set belong to the Detected Set. Reporting of measurements of the detected set is most effective relevant to intra-frequency measurements made by means of UEs in CELL_DCH kingdom.
Question 17. What Are The Various Types Of Rnc?

Answer :

Serving RNC
Drift RNC
Controlling RNC
Embedded firmware software program Interview Questions
Question 18. What Is The Use And Difference Between Crnc, Drift Rnc And Srnc?

Answer :

RNC from which the UE is currently getting Served or related to is known as SRNC or Serving RNC.

During a smooth handover process the RNC UE is transferring to, is referred to as Drift RNC.

The RNC which controls the motion of UE from Serving RNC to the Drift RNC is known as Controlling RNC.

UMTS Interview Questions
Question 19. What Is Initial Direct Transfer Message? What Is The Use?

Answer :

The preliminary direct switch process is used within the uplink to set up a signaling connection. It is also used to hold an preliminary top layer (NAS) message over the radio interface.

Question 20. What Is Security Mode Command? Why It Is Used?

Answer :

Security mode command is a RRC Message,

The reason of this technique :

To cause the begin of ciphering or to command the restart of the ciphering with a brand 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 adjust the integrity protection configuration for all signalling radio bearers
Firmware Development Interview Questions
Question 21. What Is Cctrch ?

Answer :

A Coded Composite Transport Channel is the result of mixing (multiplexing) numerous Transport Channels of the identical type; i.E.: we will have a CCTrCh made up of 1 or several DCHs, a CCTrCh made of DSCHs. One exception is that we are able to have one or several FACHs multiplexed with a PCH on the equal CCTrCh.

A better notation would be as an example:

CCTrCh4DCH: A CCTrCh which include four DCHs
CCTrCh3FACH: A CCTrCh along with three FACHs
CCTrChPCH,2FACH: A CCTrCh which includes the PCH and a pair of FACHs
Question 22. What Is Compressed Mode?

Answer :

Higher layers can request a UE to screen cells on other frequencies (FDD, TDD), or other systems (GSM). This implies that the UE has to carry out measurements, on the opposite frequencies/structures and consequently 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 records commonly transmitted throughout a 10 ms frame is compressed in time sothat gaps of ok length are created. To acquire this one among 3 mechanisms

Puncturing: This method is NOT applicable to downlink.
Spread Factor Reduction: Actually halving the Spread Factor. So with this technique 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 most effective a subset of allowed TFCs are used in Compressed Mode.
Compressed Mode Parameter:

TGSN (Transmission Gap Starting Slot Number): A transmission hole pattern starts offevolved in a radio body, referred to as firstradio frame of the transmission hole sample, containing at the least one transmission hole slot. TGSN is the slot numberof the first transmission gap slot within the first radio body of the transmission hole sample;

TGL1 (Transmission Gap Length 1): Duration of the primary transmission gap inside the transmission hole pattern, expressed in wide variety of slots;
TGL2 (Transmission Gap Length 2): Duration of the second transmission gap in the transmission gap pattern, expressed in number of slots. If this parameter isn't explicitly set by better layers, then TGL2 =TGL1;
TGD (Transmission Gap Start Distance): Duration among the beginning slots of  consecutive transmission gaps within a transmission gap sample, expressed in variety of slots. The ensuing function of the second transmission hole within its radio body(s) shall observe the limitations of TS 25.One zero one (Ref [2]). If this parameter isn't always set by way of higher layers, then there is simplest one transmission hole inside the transmission hole sample;
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 isn't explicitly set by way of higher layers, then TGPL2 = TGPL1.
The following two parameters (integers) manage the transmission gap sample sequence start and repetition:

TGPRC (Transmission Gap Pattern Repetition Count): Number of transmission gap patterns in the transmission gap sample series; From Figure 10 it appears TGPRC is even, therefore the range of slots in TG Sequence is: zero.5*TGPRC (TGPL1+TGPL2)
TGCFN (Transmission Gap Connection Frame Number): CFN of the primary radio frame of the primary sample 1 within the transmission hole pattern sequence.
Question 23. What Is Fach Measurement Occasion?

Answer :

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

Question 24. Mib/sb/sib Details?

Answer :

MIB: The Scheduling of MIB is Static.

3G Interview Questions
Question 25. Why We Perform Channelisation Or Spreading Before Scrambling?

Answer :

Before sending a information we need to identify the channel to ship the information. A specific Channelisation code is the “identity” for the channel.

Hence we use Channelisation code to pick the channel after which scramble it if you want to send the identification of the UE over the channel

Question 26. When Tmsi , P- Tmsi , Imsi , Imei Used?

Answer :

TMSI (GSM-MAP): The TMSI (GSM-MAP) will be selected if available. The IE “LAI” inside the IE “Initial UE identification” shall also be present while 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 to be had. The IE “RAI” inside the IE “Initial UE identification” shall in this case also be gift when P-TMSI (GSM-MAP) is used, for making it unique.
IMSI (GSM-MAP): The IMSI (GSM-MAP) will be chosen if to be had and no TMSI (GSM-MAP) or P-TMSI is available.
IMEI: The IMEI will be chosen whilst none of the above three situations are fulfilled.
Question 27. Why We Do A Combined Attach?

Answer :

If the community 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, mixed and periodic routing region updating tactics as opposed to the corresponding MM precise techniques IMSI attach and ordinary and periodic Location region updating.

General Packet Radio Service (GPRS) Interview Questions
Question 28. When Ue Triggers Event 3a Measurement Report?

Answer :

Event 3A:The Estimated Quality of presently used UTRAN frequency is underneath a sure threshold and the expected nice of the alternative system is above a sure threshold.

Question 29. How Many Transport Channels Will Be Configured When A Csv And A Psd Call Is Simultaneously Going On?

Answer :

Five transport channels could be configured.

1 for 4 SRBs
three for CSV
1 for PSD

Question 30. When Event 2a, 2b, 2c,2e Occurs?

Answer :

Event 2a: Change of first-rate frequency
Event 2b: The envisioned best of the presently used frequency is beneath a sure threshold and the expected fine of a non-used frequency is above a sure threshold.
Event 2c: The estimated pleasant of a non-used frequency is above a sure threshold
Event 2nd: The anticipated exceptional of the presently used frequency is under a certain threshold
Event 2e: The envisioned satisfactory of a non-used frequency is under a sure threshold
Question 31. When Event 1a – 1f Event Occurs?

Answer :

event 1A: A Primary CPICH enters the reporting range
event 1B: A number one CPICH leaves the reporting variety
occasion 1C: A non-lively primary CPICH turns into better than an lively number one CPICH
occasion 1D: Change of first-class mobile
occasion 1E: A Primary CPICH will become higher than an absolute threshold
event 1F: A Primary CPICH becomes worse than an absolute threshold
Question 32. Where Ck And Ik Gets Generated?

Answer :

In RRC CK and IK receives generated.

Question 33. Where Ck And Ik Gets Stored?

Answer :

In USIM CK and IK will get saved.

Adobe Edge Interview Questions
Question 34. Where The Security Procedure Will Start?

Answer :

Security Procedure will start in RRC but Ciphering will begin for AM and UM facts protection technique will start at RLC layer. And for TM mode safety process begin at MAC layer.

Question 35. What Are The Mandatory Sib’s Which Ue Has To Read Before Campaign?

Answer :

SIB 1, 3,5,7,11

Question 36. What Are The Important Rach Parameters And Which Sib Contains This Information?

Answer :

SIB 7/5

CDMA Interview Questions
Question 37. Which Sib Contains S Criteria Information?

Answer :

SIB three