Telecommunications Interview Questions & Answers
1. Differentiate between GSM and CDMA – Telecommunications
GSM
– GSM uses multiple frequencies.
– Uses TDMA and FDMA for accessing signals.
– The voice rate is 9.6 KBPS.
– Uses less bandwidth.
CDMA
– CDMA uses single frequency as carrier.
– The voice rate is 14.4 KBPS.
– CDMA power control to access method is better as Phased Locked Loops are used.
– Follows soft handoff, hence call handling is more efficient.
2.What is the need of CPG message in ISUP protocol? – Telecommunications
– CPG message is sent by the switch towards originator.
– When the switch receives the setup, the call is forwarded.
– When the message is sent it is signaled that the call is progress.
– During the setup or active phase of a call, a message is sent.
– This signifies the relayed to the originating has occurred.
3.What is protocol testing? What types of tool used in telecom testing? – Telecommunications
– Testing the functionality of the node to some standard message flow for compliance is known as protocol testing.
– Tester is used to send the standard message to the node that is under test.
– The testing tools used for protocol testing are:
1. Glomosim simulator – To test 100 nodes on single CPU.
2. Abacus5000 – To test SIP.
3. Etherpeek – To test IP.
4. Nethawk – for SS7 testing.
5. Wireshasrk – for SS7/IP testing.
6. K1297- for testing G20(tektronics).
4.What is MTU? – Telecommunications
– Maximum Transmission Unit refers to the largest packet size.
– MTU is for passing a communication protocol for a given layer.
– Communication interfaces such as NIC, serial port are associated with MTU parameters.
– MTU might be a fixed unit as per Ethernet recommended standards.
– Higher band-width efficiency is achieved with a higher MTU.
5.What is bridging? – Telecommunications
– One of the forward techniques to use in packet-switched networks.
– Bridging makes no assumptions about the address location of the network.
– Flooding and examination of the source addresses are the building blocks for received packet headers for locating unknown devices.
– The address of the device and its location is recorded in MAC address table for further broadcasting, after locating the device.
– Bridging refers to Transparent bridging that predominates in Ethernet.
– Source route bridging is used for token ring networks.
6.What is SS7? – Telecommunications
– A global standard for telecommunications for channel signaling.
– The Common Channel Signaling System (SS7 / C7) standard defines various procedures and protocols for Public Switch Switched Telephone Network to exchange information over digital signaling network.
– Providing call control, remote network management is the primary functions of SS7.
– Controlling messages are exchanged between SS7 telephone exchanges through SS7.
– The messages are transformed from Signaling Points and SS7 Signaling Transfer Points.
7.What is broadband? – Telecommunications
– Broadband is an internet access with high speed.
– Unlike dial-up connection, broadband connection is permanently connected.
– It allows internet and telephone calls to take place simultaneously. No new land line is required.
– Modulation is done in broadband on signals to transform data better.
8.What is Impulse Response? – Telecommunications
– Impulse Response of a system is the result that is presented with a brief input signals.
– Linear, Time-Invariant Systems are characterized by the response of their impulses.
– It is easy to analyze the systems that implements transfer functions. This is done by Laplace transform of the impulse response function.
– The output of the system can be determined in time domain by convolution of the input function with the impulse response function.
– The response of impulse and the response of Kronecker delta input are finite, as it settles zero in a finite number of interval samples.
– This process is done by Finite Impulse Response filter.
9.Explain about Infinite Impulse Response. – Telecommunications
– IIR is one of the properties of signal processing systems.
– An impulse response function that is none-zero over an infinite length of time is available in IIR systems.
– An analog filter by name RC filter is made up of a single resistor for feeding into a node.
– This is shared with a single capacitor.
– An exponential impulse response is available in this filter that is characterized by an RC time constant.
10.Explain about Common-Mode Rejection Ration. – Telecommunications
– CMRR is used for measuring the tendency of the device that is to reject the input signals.
– These signals can be from both input leads.
– CMRR at a high level is important, as the signals of interest are represented by a small set of fluctuations of voltage.
– The voltage fluctuations are superimposed on, possibly a large voltage offset.
– Superimposition of the signals might also be done, when the information of relevance is contained in the voltage difference between the two signals.
11.Describe about Asynchronous Transmission. – Telecommunications
– It uses the start and stop bits for signifying the beginning bit of ASCII character that is to be transmitted.
– For instance, ‘0100 0001 would become ‘1 0100 0001 000 1 0’’.
– The additional one bit at the beginning and ending of the transmission refers the receiver that a character is entering and the character is ended.
– When data need to be sent intermittently, this method is used.
– The start and stop bits are supposed to be opposite polarity.
– By this process, the receiver recognizes the second packet of the information that is being sent.
12.Describe Synchronous Transmission. – Telecommunications
– Synchronous transmission does not use start and stop bits, hence data transfer rate is quicker.
– The transmission is synchronized by speeding up at both the sending and receiving ends.
– This uses clock signals that are built at each component.
– Continual stream of data is sent between two nodes.
– Re-synchronization is one of the methods to address the lost bits.
– This method uses check digits instead of parity bits for ensuring the byte is correctly being interpreted and received.
13.Explain about Voice Over Internet Protocol. – Telecommunications
– VOIP is also known as broadband telephony.
– VOIP is to route the voice conversations over the internet.
– VOIP services convert telephonic signals into digital signals.
– Voice traffic is transmitted over Internet Protocol based networks.
– VOIP deploys a protocol known as session control protocol for controlling the set-up and tear-down of calls as well as audio codecs.
14.What equipment is needed for VOIP? – Telecommunications
Following are the equipment that is needed for VOIP.
– A Broadband connection.
– VOIP enabled telephones.
– Nexton Soft Switches
– A Router
– An Audiocodec
– An Astric server
– A dial-up connection can also be used for VOIP
15.What are the advantages of VOIP? – Telecommunications
Following are the advantages of VOIP:
– Call costs are cheaper than traditional telephone land line calls.
– Upgrading is simple.
– Can be integrated with existing telephone connection.
– Calls are free with VOIP PC-to-PC, irrespective of distance.
– Virtual number enables to make calls across the globe.
– Any number of geographical areas can be purchased, that works very cheap.
– Messaging is also possible with VOIP phone.
16.Describe about TTCN-3. – Telecommunications
– Testing and Test Control Notation Version 3 is one of the strongly typed tests scripting language.
– It is used testing of communicating systems conformance.
– TTCN-3 is utilized for specification of test infrastructure interfaces.
– This process is implemented with concrete communication environments.
– TTCN-3 has standardized adapter interfaces.
17.Describe about RX Lev Full. – Telecommunications
– RX Lev Full is Mobile transmit measurement report .
– This report is generated for every 480ms.
– The multi frame contains 104 TDMA frames.
– Among 104 frames 4 TDMA frames are used for decoding the BSIC.
– Remaining frames are used for serving and neighboring cells.
– The measurement of these remaining TDMA frames is RX Lev Full.
18.What is the functionality of TCSM? – Telecommunications
– TCSM is an acronym for Transcoder/Sub-Multiplexer.
– Interface traffic is carried through the radio frequency in the air.
– Data is compressed for efficient transmission of data.
– Original data of 64 KBPS on interface side is compressed to 13 KBPS on the air.
– The compression is done by TCSM
19.What is Simple Network Management Protocol? – Telecommunications
– SNMP is one of the UDP-based network protocols.
– Monitoring network-attached devices for various administrative attentions, is the main purpose of SNMP.
– SNMP is one of the protocol suites that are designed by Internet Engineering Task Force.
– It has application layer database schema, protocol, and a group of data objects.
– The basic messages, SET, GET, GET-NEXT, GET-RESPONSE and TRAP are the common messages that communicates between the SNMP manager and the SNMP agent.
20.What are the reasons for call drop? – Telecommunications
A call drop occurs when
– Slips occur in media.
– There is some antenna tilting.
– Phone goes out of range.
– Electric and mechanic tilts occur.
– Signal interference occurs.
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