What are GSM Interfaces ?

Um

• Radio interface between MS and BTS
• each physical channel supports a number of logical channels

Abis

• between BTS and BSC (vender specific)
• primary functions : traffic channel transmission, terrestrial channel management, and radio channel management

What is the functionality of TCSM ?

• 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.

Describe about RX Lev Full

• 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.

Describe about TTCN-3

• 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.

What are the reasons for call drop ?

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

What are the advantages of VoIP ?

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.

What equipment is needed for VoIP ?

• A Broadband connection.
• VOIP enabled telephones.
• Nexton Soft Switches
• A Router
• An Audiocodec
• An Astric server

What is VoIP (Voice Over Internet Protocol) ?

• 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.

Describe Synchronous Transmission

• 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.

Describe about Asynchronous Transmission

• 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.

Explain about Common-Mode Rejection Ration ?

• 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.

What is broadband ?

• 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.

GSM vs. CDMA

GSM	CDMA
uses multiple frequencies	uses single frequency as carrier
Uses TDMA and FDMA for accessing signals
voice rate is 9.6 KBPS	voice rate is 14.4 KBPS
Uses less bandwidth
	CDMA power control to access method is better as Phased Locked Loops are used
	Follows soft handoff, hence call handling is more efficient

What is SS7 ?

• 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.

Explain about Infinite Impulse Response

• 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.

What is Impulse Response ?

• 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.

What is Bridging ?

• 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.

What is MTU (Maximum Transmission Unit) ?

What is MTU?

• 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.
  

What are the functions of SMPP ?

Functions of SMPP

• Transmit messages from an ESME to single or multiple destinations via the SMSC
• An ESME may receive messages via the SMSC from other SME’s (e.g. mobile stations).
• Query the status of a short message stored on the SMSC
• Cancel or replace a short message stored on the SMSC
• Send a registered short message (for which a ‘delivery receipt’ will be returned by the SMSC to the message originator)
• Schedule the message delivery date and time
• Select the message mode, i.e. datagram or store and forward
• Set the delivery priority of the short message
• Define the data coding type of the short message
• Set the short message validity period
• Associate a service type with each message e.g. voice mail notification

How SMPP communication works ?