Questionnaire

Index:

Section A: General GSM (20 marks): It has questions 1 to 10

Section B: Installation (30 marks) : It has questions 11 to 25

Section C: Commissioning (36 marks) : It has questions 26 to 40

Section D: Integration & O&M (20 marks) : It has questions 41 to 50

Section A: General GSM (20 marks)

Q1: What is the uplink & downlink frequency band in GSM 900 & GSM 1800 networks respectively? – 02 marksAns1: GSM 900:

Uplink: - 890-915 MHz (from Mobile to base station) Down link: - 935-960 MHz (from base station to Mobile)

GSM 1800: Uplink: - 1710-1785 MHz (from Mobile to base station) Down link: - 1805-1880 MHz (from base station to Mobile)

Q2: How many channels are available in GSM 900 & GSM 1800 bands respectively and what is the bandwidth of each channel? – 01 markAns2: GSM 900: 124 channels of 200 KHz bandwidth each

GSM 1800: 324 channels of 200 KHz bandwidth each

Q3: What are the elements of general GSM network architecture and Draw it & write function of each in brief? - 05 marksAns3: Elements in General GSM architecture:

1) MSC 2) VLR 3) HLR 4) AC 5) EIR 6) Transcoder7) NMS/OMC 8) BSC 9) BTS 10) Mobile station

MSC: The MSC (Main Switching Centre) is responsible for controlling calls in the mobile network. It identifies the origin and destination of a call (either a mobile station or a fixed telephone in both cases), as well as the type of a call. An MSC acting as a bridge between a mobile network and a fixed network is called a Gateway MSC. VLR: An MSC is normally integrated with a VLR (Visitor Location Register), which maintains information related to the subscribers who are currently in the service area of the MSC. The VLR carries out location registrations and updates. The MSC associated with it initiates the paging process. A VLR database is always temporary (in the sense that, the data is held as long as the subscriber is within its service area)HLR: The HLR (Home Location Register) maintains a permanent register of the subscribers. In addition to the fixed data, the HLR also maintains a temporary database which contains the current location of its customers. This data is required for routing calls.AC: AC (Authentication Centre) is the used for authenticating the subscribers. Authentication is a procedure used in checking the validity and integrity of subscriber data. With the help of the authentication procedure the operator prevents the use of false SIM modules in the network.

EIR: An option exists in GSM where the network may check the validity of the mobile station hardware. The mobile station is requested to provide the International Mobile Equipment Identity (IMEI) number. This number consists of type approval code, final assembly code and serial number of the mobile station. The network stores the IMEI numbers in the Equipment Identity Register (EIR).Transcoder (TCSM): A converter has to be provided in the network to change the bit rate from one to another. This is called the Transcoder (TC). If the TC is located as close as possible to the MSC with standard PCM lines connecting the network elements, we can, in theory, multiplex four traffic channels in one PCM channel. This increases the efficiency of the PCM lines. To enable the efficient transmission of the digital speech information over the radio Air Interface the digital speech signal is compressed.But when connecting to the MSC, the multiplexed lines have to be de - multiplexed. In this case the unit is called Transcoder and Submultiplexer (TCSM).NMS/OMC: The purpose of the NMS (Network Management System)/ OMC (Operation and Maintenance Centre) is to monitor various functions and elements of the network. These tasks are carried out by the NMS, which consists of a number of Work Stations, Servers and a Router which connects to a Data Communications Network (DCN). The functions of the NMS can be divided into three categories:

· Fault Management· Configuration Management· Performance Management

BSC: The Base Station Controller (BSC) is the central network element of the BSS and it controls the radio network. This means that the main responsibilities of the BSC are: Connection establishment between MS and NSS, Mobility management, Statistical raw data collection, Air and A interface signalling support.BTS: The Base Transceiver Station (BTS) is a network element maintaining the Air interface. It takes care of Air interface signalling, Air interface ciphering and speech processing. In this context, speech processing refers to all the functions the BTS performs in order to guarantee an error-free connection between the MS and the BTS.MS: Mobile station (MS) is a mobile handset, which normally has a SIM (Subscriber Identity Module). SIM acts like a label of the MS for any reference for contact. It is generally a numerical value with 10 digits, which is referred as mobile number of a subscriber.

Q4: What are various types of interfaces used in 2G GSM network architecture, their usage between which all network elements and define whether it is open or closed interface? - 02 marksAns4: A-interface: MSC-HLR, MSC-Transcoder, MSC-GMSC, MSC-PSTN NW --- It is open interface

A-ter interface: BSC-Transcoder ---- It is closed interfaceA-bis interface: BSC-BTS ---- It is closed interfaceAir interface: BTS-MS --- it is open interfaceX.25 interface: NMS-BSC, NMS-MSC

Q5: GSM is used on which digital technologies? – 01 markAns5: FDMA & TDMA. Frequency Division Multiple Access (FDMA) refers to the fact that each Base transceiver Station is allocated different radio frequency channels. Mobile phones in adjacent cells (or in the same cell) can operate at the same time but are separated according to frequency. Time Division Multiple Access (TDMA), as the name suggests, is a method of sharing a resource (in this case a radio frequency) between multiple users, by allocating a specific time (known as a time slot) for each user. TDMA timeslots are called as physical channels in GSM as they are used to physically move information from one place to another. The radio carrier signal between the Mobile Station and the BTS is divided into a continuous stream of timeslots which in turn are transmitted in a continuous stream of TDMA frames.

Q6: Which type of analogue modulation technique is used in GSM? – 01 markAns6: Phase Modulation as GMSK (Gaussian Minimum Shift Keying).

Q7: Give advantages, disadvantages and applications areas of following type of analogue modulation techniques? – 03 marks

a) Amplitude b) Frequency c) Phase Ans7: Amplitude modulation (AM) is a technique that works by varying the strength of the transmitted signal (source signal frequqency) in relation to the information being sent (carrier frequency). Medium wave radio station is simplest example of it’s application area, where the signal travels to much larger distance.Frequency modulation (FM) conveys information over a carrier wave by varying its frequency (contrast this with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant). FM is commonly used at VHF radio frequencies for high-fidelity broadcasts of music and speech.

Normal (analog) TV sound is also broadcast using FM. In this technique signal travels to comparatively shorter distance but has very good speech quality.

Phase modulation (PM) is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave. Unlike its more popular counterpart, frequency modulation (FM), PM is not very widely used. This is because it tends to require more complex receiving hardware and there can be ambiguity problems with determining whether, for example, the signal has 0° phase or 180° phase. GSM uses this technique as one of its application area.

Q8: How to define Erlangs? – 01 markAns8: Erlang is the measuring unit of network traffic. One Erlang equals the continuous use of a mobile device for one hour. The traffic is calculated using a simple formula:

x Erlangs = (calls per hour) x (average conversation time)3600 seconds

Q9: What do we mean by GPRS & EDGE? – 02 marksAns9: GPRS (Genaral Packet Radio Service)-The Internet has become part of everyday life, GPRS gives a direct link between the worlds of the Internet and mobile communications GPRS is different from existing GSM data services. Firstly it allows users to have the same experience as if they were connected to their office LAN. The mobile user doesn't have to connect to the network each time he wants to transfer data; he can stay connected all day. Secondly GPRS allows users to be charged for the actual amount of data they transfer.EDGE (Enhanced Data rates over GSM Evolution)- EDGE provides a bridge from GSM into the 3rd Generation mobile networks. It uses an advanced GSM modulation technique to provide data speeds of 384Kbits/s but still using the existing 200 KHz GSM channel. EDGE provides the ability to handle wireless multimedia services such as Internet/intranet, video conferencing, and fast electronic mail transfer. One of the attractions of EDGE technology is that it requires minor changes to network hardware and software, and can be introduced into an existing network using the current frequency bands.

Q10: What do we mean by Receiver Diversity? – 02 marksAns10: Antenna Receiver Diversity is a technique to achieve better received signal strength and quality. This is achieved by following:

a) Space diversity: In this mode, antennae are separated by a defined distance in order to ensure that signal dip. If a fading dip occurs at the position of one antenna, the other antenna will still be able to receive the signal. The distance between two antennas is a few metres.

b) Frequency diversity: The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading. Frequency Hopping is the similar phenomenon

c) Polarization diversity: Multiple versions of a signal are transmitted and received via antennas with different polarization. A diversity combining technique is applied on the receiver side.

Section B: Installation (30 marks)

Q11: What is the recommended earthing value for Telecomm Equipment at a BTS site? – 01 markAns11: 1 ohm or less.

Q12: What are major ten pre-checks (indoor and Outdoor) to be ensured before starting the installation of BTS/MW at a site? – 05 marksAns12: RFI checklist needs to be ensured. Major points are:

1) Tower erection, DG installation, Shelter/OD BTS foundations are done2) Antenna mounts w.r.t. GSM and MW antenna are available as per TND/RND3) Lightening arrestor and aviation light installed and working4) Horizontal & vertical cable ladder with safety rings properly installed5) Earth pits completed and connection available upto IGB/EGB6) Shelter earthing, antistatic completed and is properly sealed to ensure temperature/humidity

requirement.7) Aircons installed and in working position with proper sealing done8) Roxtec cutting as per specifications and plan done

9) Power supply available to do electrical work10) All material to install this site in all respects in one shot verified against SDR and reported for any

missing item to customer.11) All tools and data sheet (details of equipment config, MW, azimuth, height etc.) required to install this

site available with team.

Q13: What is the power consumption of 444 Flexi BTS and what MCB rating is used to provide input power supply? – 02 marksAns13: Power consumption of 444 Flexi BTS is approx max. 2000W (depending on GSM 900-1948W & GSM 1800-2098W)

Q14: What is the input power supply observed at power plant MCB being used as input to Flexi BTS? – 01 markAns14: -53.5V to -54.5 V, 60 to 80A MCB.

Q15: What is the maximum bending radius in meter and signal strength loss per meter of a 7/8” coaxial copper Andrew feeder cable? – 02 marksAns15: Max bending radius is 300mm for 7/8’ standard Andrew feeder cable and signal strength loss is 0.04dB per meter.

Q16: What is the basis of calculating no. of earthing kits on feeder cable length? – 01 markAns16: One earthing kit needs to be installed just outside the Shelter Roxtec and then from there next grounding kits have to be installed after gaps of 25 mtr each. Q17: How many types of tilts are possible in GSM antennae and how to check it? – 02 markAns17: Mechanical Tilt: Tilt reading measurements are available on Antenna mounting kit at top side to set the required tilt. Electrical Tilt: A circular knob is normally available to with Tilt measurement to set the required Tilt.

Q18: What parameter decides the length of input DC power supply cable of BTS/MW? – 01 markAns18: Voltage drop is the parameter which decides the length & diameter of power cable to be used for giving power supply to BTS/MW.

Q19: What is power plant and battery bank capacity required for Flexi BTS 444 configuration and two PDH MW hops (consider Flexi Hopper) for 4-6 hrs backup? – 02 marksAns19: 100 A capacity (n+1 mode) of power plant and 300 AH Battery Bank is used at BTS sites to cater to above mentioned requirement.

Q20: What is the ideal VSWR value possible in Zero defect installation condition and what is the acceptable limit? – 02 marksAns20: Ideal value for VSWR is 1 and 1.3 is the acceptable limit for approx 40 mtr feeder cable.

Q21: What is the dimension of Flexi Indoor 444 BTS and Ultra BTS and clearance required around these? – 02 marksAns21: 600x570x1700 (WxDxH) in mm for Ultra Indoor BTS & 600x600x1800 (WxDxH) in mm for Flexi BTS considering cabinet option, as width of modules is 447mm & depth will be 570mm only.

Q22: What is the standard specification of DC power supply and earthing cable w.r.t. to length and diameter being used in Flexi BTS? – 02 marksAns22: 25 mm2 diameter and approx 08 mtr (-ve & +ve each) is the requirement for DC Power supply and 25 mm2 diameter and 20 mtr length Earthing cable

Q23: Name mandatory 10 tools which BTS commissioning engr must carry all the time while going for commissioning? – 05 marksAns23: List of tools is made available to all Engineers. Mandatory are:

1) Laptop with accessories with all commissioning and applications softwares installed and running successfully

2) All types of LMP & Q1 cables to connect to Ultra BTS, Flexi BTS, Flexi Hopper etc.3) Test instruments to ensure the installation, commissioning & integration checks – Site master, power

meter with all accessories

4) Multimeter5) SMA torque wrench suitable for inter cards cabling toghtness6) Required set of spanners7) Wrist band8) Fully charged Mobile handset with respective charger and battery which can last for atleast few hours9) Pliers and screw drivers10) Krone punching tool.

Q24: What is the torque limit of torque wrench used for SMA connector in BTS? – 01 markAns24: Torqe limit for SMA torque wrench is: 1Nm

Q25: What is the SQI (Site Quality Index) maximum acceptable limit for a BTS site? – 01 markAns25: SQI has to be <6.

Section C: Commissioning (30 marks)

Q26: What are the major 5 pre-checks for doing power ON and starting commissioning? – 03 marksAns26: Assuming that BTS, Power plant and Battery banks along with other Infra items installed as per RFI checklist, following points must be ensured before powering ON and start commissioning of BTS:

1) Input power voltage at the MCB of Power plant msut be within range: -46V to -55V DC2) IGB & EGB bus bars are further connected to Earth pits thoroughly3) VSWR of all the feeder cables is well within limits (< 1.3)4) All the interconnect cables of BTS are connected as per site configuration.5) All the required tools & test instruments are available with engineer and are in properly working

condition.

Q27: What is the Transmitter output of Flexi BTS TRX and what is the 2-way combiner loss? – 02 marks Ans27: Tx output of Flexi BTS TRX is 47dBm. 2-way combiner loss is 3 dBm.

Q28: How many external alarms inputs and outputs are possible in Flexi BTS? – 02 marksAns28: 24 no.s of external alarm inputs and 6 external alarms outputs are possible in Flexi BTS.

Q29: What TCP IP address, Subnet mask & Default gateway must be put in Laptop to establish connection with Flexi BTS? – 02 marksAns29:

Q30: What type of Ether net cable should be used to connect Laptop with Flexi BTS? – 01 marka) Straight-through b) Cross over c) Both d) Other – pls specify

Ans30: c) Both

Q31: What are the various types of cards/units in Flexi BTS & Ultra BTS for 444 configurations? Explain in brief each of them? – 03 marksAns31: Ultra BTSBOIA: Base station operation & Interface card:- 1 No.

- User interface- Oscillator frequency controller- Alarms extension towards BSC

BB2x: Base band cards:- 6 Nos.- Base band signal processing- Handles 2 TRXs

TSGx: TRXs:- 12 Nos.- Transreceiver unit- Handles voice and data traffic- Signaling for traffic flow- Has diversity ports to get the best signal

WBC: Wide band combiner:-6 Nos- Combines two TRX outputs- Has 3 dB loss- Increases traffic capacity at the cost of coverage shrinkage

MLxA: Multicoupler:- 6 Nos.- Used on receiving side- Provides coupler function to get main & diversity application

DVGx: Duplexer:- 3 Nos.- Antenna feeder interface- Has 3 port switch to ensure Trasmit path and receive path bi furcation- Has RX and RX D ports

FXC E1/T1/FXC RRI: Transmission cards:- 1 Minimum – depending on Tx plan- FXCE1/T1 has 4 x 2M ports- Traffic manager is being handled- By pass of timeslots/E1 at 8K level to 2M level- FXCRRI has 2xFlex bus ports at IF signal level- Traffic manager is being handled- By pass of timeslots and complete multiple 2M levels and has max capacity of 16 E1s

Flexi BTS:

ESMA (Nokia Flexi EDGE System Module) – 1 No.- Module for BTS common functionalities and internal/external connections- Supports up to 6 DTRX modules (up to 12TRX) 5 main functions of the module:

BTS O&M: SW downloading and storing (2 * BTS SW), configuration management, reference clock and alarmsBTS integrated transport: Abis transmissionBB switching: communication between modules via Ethernet switchBTS power distribution: single point for power intake and power distribution to all modulesBTS internal and external synchronization

EXxA (Nokia Flexi EDGE Dual TRX Module) – 6 Nos.- Dual TRX module (DTRX) is a 2 carrier TRX unit, used as:

- a stand alone TRX module (2 TRX capacity)- or a Sector module with the Dual duplexer module (2 TRX capacity)- or as Double Power TRX, DPTRX (1 TRX capacity)- or for Intelligent Downlink Diversity, IDD (1 TRX capacity)

- DTRX consists of: - BB part that is common to both TRXs- RF part with 2 independent transmit (TX) chains and 4 receive (RX) chains- 0-2 Wideband combiner (WBC) sub-modules

- DTRX connected to system module via single Gigabit Ethernet interface - Power feed from system module via single cable

ERxA (Nokia Flexi EDGE Dual Duplexer Module) – 6 Nos.

- Dual duplexer (DDU) module together with Dual TRX create a logical Sector module- Min 1 DDU per sector is needed - DDU is attached to DTRX module

- DDU provides - duplex functionality to combine TX and RX signals to same antenna feeder multicoupling- 2 antenna connections (for 1 or 2 sectors)- 2 TX inputs and 4+4 RX outputs (4 RX from antenna 1 and 4 RX from antenna 2)

- DDU contains - 2 duplex filter- 2 Low Noise Amplifiers (LNAs) with high/low gain support for RX signal- 2 Bias-Ts with VSWR measurement functionality

- TRX loop is controlled through the DDU - Common TRX loop for all TRXs in same sector- Loop can be performed from either TX to any of 8 RX outputs (only 1 TX and 1 RX can be Simultaneously tested)

Ewx A (Flexi EDGE Wideband Combiner) – 6 Nos.The Flexi EDGE BTS wideband combiner consists of a 2-way power combiner, isolators on each input, unit mechanics, and a combined power output port. There are two input connectors TxA and TxB and one output connector TxOut. Flexi EDGE Sector Module- Sector module is a logical unit consisting of 2 building blocks:

- Dual TRX (DTRX) module - Dual duplexer module

- Minimum one Sector module is needed per sector- There is space for 1-2 optional Wideband combiner (WBC) submodules in DTRX module- For 4-way UL diversity 2 Sector modules are needed per sector - Both units fit into a 3HU casingNokia Flexi EDGE System Extension Module (ESEA) – Optional – 1 No.

- System extension module is required for large BTS configurations (System module for 1-6 DTRX, System extension module for 7-12 DTRX)- System extension module is always required for RTC configurations- All TRXs must be connected to same system module for BB hopping- The functionalities of System extension module:

- Power distribution to additional modules (i.e. DTRX 7-12). Power distribution part has six 48V outputs

- Providing 12 Ethernet and synchronization connections to DTRX (DTRX 1-12) and 1 connection to System module

FIPA (E1/T1 card) & FIFA (RRI unit) depending on the transmission requirement – 1 No.

Q32: What is the Factory default user name and password? – 01 markAns32: Factory default User Name: PAM, Password: PAM

Q33: Which is the deciding factor to lable a MW radio as either High end or Low end – Transmitter frequency or Receiver frequency? – 01 markAns33: Tx frequency is the deciding factor to lable a MW radio as either High end or Low end.

Q34: What is the Tx-Rx spacing for 15 GHz Flexi Hopper MW radios? – 01 markAns34: 420 MHz (Tx frequency – Rx frequency)

Q35: What is the coarse and Fine alignment limits for Flexi Hopper MW PDH hops upto 60 cm diameter antennae? – 02 marksAns35: Coarse vertical settings are possible at +25° or -25° or middle position. At the factory, the vertical adjustment on the integrated alignment unit is set to the middle position.

The fine horizontal adjustment range is ±15°. The fine vertical adjustment ranges are +45° to 0°, ±25°, or 0° to −45°, depending on the coarse vertical adjustment.

Q36: Alignment of a Flexi Hopper MW radio is achieved by which of the following? – 01 mark a) Increasing the AGC voltage to maximum b) Decreasing the AGC voltage to minimumAns36: b) Decreasing the AGC voltage to minimum

Q37: What are the various signal types to be choosen while entering the Traffic manager and explain in brief the function of each? – 04 marksAns37: Abis Channels

OMUSIG (Operation & Maintenance Signaling Channel)• used to transmit alarms BTS_BSC, remote SW upgrades, remote EM connections• sizes 16 / 32 or 64 kbits/sTCH (Traffic Channel)• used to carry circuit switched traffic (voice and data) and packet switched (GPRS) data• max. 8 TCHs (16 kbits/s) for 1 TRXTRXSIG (Transceiver Signaling Channel)• used to control the TRX by the BSC• 1 TRXSIG (16 / 32 / 64 kbits/S) per TRXEDAP (EDGE Dynamic Abis Pool)• used to carry packet switched EDGE traffic• max. size 12 PCM timeslots• allocation to 1…12 TRXs• several EDAPs possible per BTS

Q38: What are the granularities supported in Type PB (Protected conditional switch)? – 01 markAns38: Type PB (Protected Condition Switch): Bidirectional (PB2) conditional connection

Used in configuring channel protectionGranularities supported: 16k, 32k, 64k, and n x 64kRequires a condition, available in two switchover modes (types): priority and equal

Q39: Write top 10 quality checks to be ensured before taking the site through Acceptance Testing (A/T) procedure? – 04 marksAns39: Following Quality checks must be performed before site goes through A/T process:

1) BTS, Power plant, battery bank are installed as per approved layout diagram2) Feeder and other related cabling must be installed and labeled as per standard being given.3) VSWR, Power and input power voltages, battery cell voltages must be well within limits4) Earthing must be very carefully verified to ensure end to end connectivity and shortest path

mechanism5) DDF must be installed, earth connected and labeled as per plan given.6) External alarms must be connected, tested and working as per standard defined in respective circle7) BTS, Power plant should not be having any alarms8) Site folder must be filled and updated with all required and applicable information9) Any leftout material against SDR (material requested) and material consumed should be properly

recorded and signed with customer and guard and informed to customer on the day of completion of the installation.

10) SQI must be checked and photographs must be taken as proof of installation of the site, which should be recorded as part of site folder along with other Hardware & commissioning files.

Q40: What all measurements along with their acceptable limits should be done before A/T? – 02 marksAns40: Earthing value < 0.5 Ohm,

VSWR value for all feeders < 1.3, TRX power for all TRXs: 47dBm +/- 1 dBm, Power plant supply voltage around -53.5 V, Battery Bank cell voltages more than 2.2 V.

Section D: Integration & O&M (20 marks)

Q41: How many 2M interfaces are available in FXC E1/T1 card in Ultra BTS & FIPA card in Flexi BTS? – 2 marksAns41: FXCE1/T1: 4 x 2 M interfaces in Ultra BTS, FIPA: 8 x 2 M interfaces in Flexi BTS.

Q42: What is the difference between “No Incoming signal” and “AIS” alarms practically on a 2Mb? – 02 marks

Ans42: “No Incoming signal” alarm comes when there is cable/connector connection problem at local site. “AIS” alarm comes when there is problem at Far end cable/connector problem or Link problem where signal gets re-generated.

Q43: OMU is not through at BTS site connected through MW link from BSC site, what should be the way forward to troubleshoot? – 02 marksAns43: a) Local cross connections/Traffic manager needs to be re-verified as per plan and to be compared with what has been defined in BSC. b) E1 which has been made through needs to be verified at both ends and all possible links inbetween.c) ET card at BSC has been connected correctly as per plan and is active.d) OMU has been made active at BSC needs to be re-confirmed.

Q44: BTS is ON and radiating signal (Signal bars are available in phone latched on this site), but call is not happening at all. What should be possible reasons? – 02 marksAns44: Assuming that BTS is ON and does not have any alarms and site is radiating fully, but still calls are not happening. Possible problems are BTS not defined in MSC or is locked. Wrong ET patched with same Transmission parameters. Loose or wrong feeder/jumper connections.

Q45: What is meaning of alarm “Blocked from Use”? – 01 markAns45: This alarm comes when a cross-connection is configured to an interface, which is not in use.

Q46: What problems do we face if there is jumper swap issue in feeders and how to ensure that it does not happen during installation? – 02 marksAns46: Normally call drops and handover problems are reported as a result of feeder swap between sectors. Multimeter connectivity test by giving loop at top and measuring beep can avoid this type of problem and ensure that labeling is correct through from BTS top/Duplexer to jumper to feeder to GSM antenna.

Q47: If a Flexi BTS has to go through Undo – commissioning process, what is the way that further connected sites should not get affected during this process? – 02 markAns47: a) If the bypass capacity is not removed, undoing the BTS commissioning will leave the BTS in a non-operational state but other sites that are using this site as a transmission hub will not be affected.

b) Use of FIU (Flexi Hopper Indoor unit), which is an independent unit will have no effect of Undo-commissioning impact/restart.

Q48: What all should be done in case external alarms are not getting reported properly to NMS/OMC? – 02 marksAns48: External alarms needs to be tested thoroughly with end to end operation

– Wiring connection at alarms connector and DDF– Correct polarity and text definition at BSC– Alarm cable may be faulty– NO/NC checks of respective alarm generating element at point of alarm generation and correct

cabling upto DDF from element like DG, Fire & smoke detector box, AC etc.

Q49: What do we mean by handover and what are various types of handovers in GSM? – 02 marksAns49: Handover is a mechanism where a mobile handset moves from one Cell area to another without call getting dropped. Various types of handovers

– Intra cell (between TRXs)– Inter cell Intra BTS– Inter cell Inter BTS Intra BSC– Inter cell Inter BTS Inter BSC Intra MSC– Inter cell Inter BTS Inter BSC Inter MSC

Q50: What are various check items needs to be done before leaving and operational site? – 03 marksAns50: Ensure at site:

- Site is without any internal and external alarms- Site is radiating as per planned configuration- No call drops- No handover problems- Site is neat & clean and site quality is good- DG is working properly

- All the cabinets etc are properly closed- Any changes done during site activity has been thoroughly closed- Information to OMC is done before leaving site.