Mobile communication and its principles bsnl

mobile communication

1. Name : Priyansh Jaiswal Roll No : 0201EC2201073 Branch :Electronics & Telecommunication Engineering Vocational Training

2. Overview of Mobile Communication

3. Objective of the presentation

4. What is Telecom ? Telecommunication is the assisted transmission of signals over a distance for the purpose of communication. It is the technology of transferring information over a distance.

5. Information Information can be of several type: Audio – Telephone Text - Telegraph , email, SMS Pictures – Picture attachments Video – Clipping over internet Data – ATM to bank. The same telecom technology/service cannot communicate all types of information.

6. Telecom scenario Growing subscriber base. New services and technologies. More focus on wireless & internet. Government wants more development in rural areas. Decreasing Prices. Increasing demand for bandwidth.

7. OVERVIEW OF TELECOM NETWORK Traditionally, telephone networks have been provided to carry voice traffic. Early analogue networks have been replaced by digital networks. More recently, the availability of the Internet and the Voice over Internet Protocol has provided an entirely new paradigm for data and multimedia services. Mobile networks themselves are developing into ubiquitous networks, able to offer a wide range of data and video, as well as voice services. The Internet, which began as a data network, is now able to support voice and other real-time services.

8. OVERVIEW OF TELECOM NETWORK There are three networking approaches Circuit-switched , Internet / Data Network and Cellular mobile All these architectures are migrating towards a common IP network infrastructure called Next Generation Network (NGN).

9. Concepts Telecommunications is the transfer of information from a transmitter to a receiver over a distance. A telecommunication network is required to transmit messages between any of its users (who are usually called customers or subscribers), and the messages may be conveyed by signals that are either digital or analogue. Telecommunication system - enable the transmission of information over public or private networks (voice, data, graphics, video…)

10. Concepts & Definitions Definitions: Transmitter: originates information transfer Receiver: receives the transferred information Circuit : a communications path between transmitter and receiver over an established medium Link: a two-point segment of an end-to-end circuit

11. Concepts Switch: a device that establishes, maintains, and changes connections over circuits Subscriber Line: a single physical connection between a user and a switch Trunks: the physical connection between switches Channel: a channel is a division in a transmission medium so that it can be used to send multiple streams of information, a circuit can contain multiple channels

12. Concepts Bit : The binary digit or bit is a unit of information transfer. Byte : a collection of 8 bits Signal : It is electrical, electronic or optical representation of data, which can be sent over a communication medium. Stated in mathematical terms, a signal is merely a function of the data. Signals can be either analogue or digital . Symbols : In communications, the analog signal shape, by pre-agreed convention, stands for a certain number of bits and is called a symbol.

13. Concepts Baud : Symbols transmitted per second is known as baud. Modulation : The shaping of a signal to convey information is known as modulation. Network : A network is a collection of transmitters, receivers and transceivers that communicate with each other. Multiplexing : combining a defined integral number of input signals (called tributaries).

14. Concepts Modems (modulation/demodulation) : Changes signals from analog to digital and back to analog. - Spectrum -range of frequencies - Bandwidth -width of the spectrum Bandwidth Alternatives : Bandwidth is the frequency range of a telecommunications network. Determines the channel’s maximum transmission rate. Measured in bits per second (bps) or baud. Narrow-band : Low-speed transmission. Broadband : High-speed transmission.

15. 15 Electromagnetic Signals Function of time Analog (varies smoothly over time) Digital (constant level over time, followed by a change to another level) Function of frequency (more important) Spectrum (range of frequencies) Bandwidth ( width of the spectrum)

16. ANALOG SIGNAL Continuous Waveform Analog signals are continuous-valued; Voice Communications and video

17. DIGITAL SIGNAL DISCRETE WAVEFORM i.e. depicted as discontinuous TWO DISCRETE STATES: 1-BIT & 0-BIT ON / OFF PULSE (Each pulse (on/off) is known as a bit) USES MODEM TO TRANSLATE ANALOG TO DIGITAL, DIGITAL TO ANALOG

18. Advantages of Digital Transmission The signal is exact Signals can be checked for errors Noise/interference are easily filtered out A variety of services can be offered over one line Higher bandwidth is possible with data compression

19. Network Elements of PSTN A telecommunication network may therefore be considered as a system consisting of four basic network elements: Station apparatus Transmission Switching Signaling

20. Network Elements

21. Station apparatus Station Apparatus are the transmitters and receivers: Telephones Answering Machines Facsimile Machines Most are combined transmitters and receivers

22. Station apparatus Telephone handset works by converting sound waves into electrical impulses and back into sound waves.

23. TRANSMISSION Transmission is the conveyance of signals from one place to another. Signals may be audio, video, or data Transmission systems include: Open Wire Copper wire cable (Twisted Wires) Co-axial Cable Microwave radio (terrestrial and satellite) Fiber optic cable Other wireless

24. TRANSMISSION Modern networks use “multiplexing”, the sharing of a transmission medium by multiple signals Circuit Digital Line DLC Ports Carrier Units Toll Trunk Splice point Access Lines DLC IXC Switch DLC

25. TRANSMISSION Open wire

26. Transmission Modes Performance can be measured by the mode of the connection. Simplex transmission , messages can be carried in only one direction. Half-duplex, messages can be carried in both directions just not simultaneously. Full-duplex, messages can be carried in both directions simultaneously.

27. SWITCHING Telephones introduced in late-1800. Initially each telephone was directly connected to another site. This led to an explosion of direct connections (n*(n-1)/2) This lead to the need to “switch” the connections. Switch

28. Evolution of Electronic Exchanges Switches establish, maintain, and change connectivity between circuits The earliest telephone exchanges used switchboards worked by operators. The manual exchange was unique among switching systems, since a single switch (i.e., the operator) could make a connection to any of several thousand lines by inserting a plug in a jack within arm’s reach. To overcome the limitations of manual switching; automatic exchanges, having Electro-mechanical components were developed. Electromechanical exchanges still had lot of disadvantages viz. a large number of mechanical parts, limited availability, inflexibility, bulky in size etc. With further research and development , electronic exchanges came into existence.

29. Electronic exchanges had a lot of advantages over electromechanical exchanges. These exchanges are almost noiseless, easy installation,switch room space required was much less, changes could be carried out by simple commands. Testing carried out periodically automatically and analysis printed out Remedial maintenance is very easy due to plug-in type circuit boards. A modern electronic exchange performs basic actions very rapidly, so it can be controlled by a single central digital processor. Present day digital exchanges are called SPC exchanges- Stored Program Controlled exchanges. Evolution of Electronic Exchanges

30. In an SPC exchange, a processor similar to a general purpose computer, is used to control the functions of the exchange. All the control functions. represented by a series of various instructions, are stored in the memory. Therefore the processor and memories hold all exchange-dependent data. such as subscriber date, translation tables, routing and charging information and call records. For each call processing step. according to class of service, the stored data is referred to. The memories are modifiable and the control program can always be rewritten if the behavior or the use of system is to be modified. This imparts enormous flexibility in overall working of the exchange. Evolution of Electronic Exchanges

31. Electronic Exchanges Digital switches are simply computers that make logical routing decisions to connect circuits to complete calls When a call is dialed, the end-office switch decides whether it can handle the call or if it needs to pass it up the hierarchy Each switch in succession makes the decision to pass it up or down the hierarchy until it reaches the end-office that can complete the call

32. SIGNALING In order for the network to function properly, the various components and elements must have the ability to signal each other to indicate status and condition. Signaling can be either: In-band: takes place over the same physical path as the conversation and occupy the same channel Out-of-band: takes place over a separate channel or physical path as the conversation

33. SIGNALING Signaling performs several functions: Supervising: monitoring the status of a line or circuit to see if it is busy, idle or requesting service; and performing diagnostics Alerting: indicates a specific condition such as the arrival of an incoming call (ringing), off-hook status (alert tone), busy signal, etc. Addressing: transmitting routing, billing and destination information

34. SIGNALING Basic Phases of a Call

35. Basic Phases of a Call Phase 1- When a customer trying to make call he will lift the receiver. This in turn will activate the telephone exchange and immediately dial tone will be fed from the exchange to indicate that exchange is waiting for the dialing digits. Phase 2- Customer starts dialing. Normally this dialing period is variable and usually around 10 seconds. Phase 3- When customer dials the complete B number (call number) the originating exchange will decide the route that has to be activated and send the B number details in an agreed protocol to the terminating exchange. Phase 4- When the terminating exchange finds the B customer is free it will send ringing current to the B customer and send Ring Back Tone to the A customer (A is the originating customer). If B customer does not answer within one minute (can be programmed) A customer will be disconnected.

36. Basic Phases of a Call Phase 5- When the B customer answers the terminating exchange will remove Ring Back Tone and ringing current and inform the answer condition to the originating exchange. Normally this will take around 100-200ms and generally is variable within millisecond periods. Phase 6- A and B customers speaking.

37. Public Switched Telephone Network

38. PULSE CODE MODULATION Pulse - code modulation  ( PCM ) is used to digitally represent sampled analog signals. PCM is widely used in digital communications. PCM systems use TDM technique to provide a number of circuits on the same transmission medium. PCM signals can be easily regenerated by repeaters in long-distance digital telephony. BASIC REQUIREMENTS FOR PCM SYSTEM To develop a PCM signal from several analogue signals, the following processing steps are required Filtering Sampling Quantization Encoding Line Coding

39. BASIC REQUIREMENTS FOR PCM SYSTEM Filtering: Filters are used to limit the speech signal to the frequency band 300-3400 Hz Sampling: If a band limited signal is sampled at regular intervals of time and at a rate equal to or more than twice the highest signal frequency in the band, then the sample contains all the information of the original signal. Quantization : The process of measuring the numerical values of the samples and giving them a table value in a suitable scale is called Quantizing. Encoding : Conversion of quantized analogue levels to binary signal is called encoding Line Coding :For distortion free transmission, the PCM output should be converted into a suitable code which will match the characteristics of the medium. This code is called the "line code”

40. MULTIPLEXING The technique used to provide a number of circuits using a single transmission link is called Multiplexing. There are basically two types of multiplexing techniques Frequency Division Multiplexing (FDM) The FDM techniques is the process of translating individual speech circuits (300-3400 Hz) into pre-assigned frequency slots within the bandwidth of the transmission medium. Time Division Multiplexing (TDM) Time division multiplexing involves nothing more than sharing a transmission medium by a number of circuits in time domain by establishing a sequence of time slots durg which individual channels (circuits) can be transmitted.

41. PCM PRINCIPLES Frequency Division Multiplexing Techniques The FDM techniques are the process of translating individual speech circuits (300-3400 Hz) into pre-assigned frequency slots within the bandwidth of the transmission medium. The frequency translation is done by amplitude modulation of the audio frequency with an appropriate carrier frequency FDM techniques usually find their application in analogue transmission systems

42. Time Division Multiplexing Time division multiplexing involves sharing a transmission medium by a number of circuits in time domain by establishing a sequence of time slots during which individual channels (circuits) can be transmitted This staggering of channels in time sequence for transmission over a common medium is called Time Division Multiplexing (TDM).

43. One network for everything Today Tomorrow Telephone network Mobile radio network IP-Network Internet Transition to NGN: Third wave

44. Wireless Gateways Internet POTS Integrated Services Over IP Evolving towards All IP Communications Next Generation Networks (NGN) Present Day Networks Next Generation Networks

45. NEXT GENERATION NETWORKS It is a packet-based network that can use multiple transport network technologies. The transport network has QoS capabilities. Service-related functions are separated from the transport technologies. The access and core networks are clearly separated so that users can have a choice about who delivers the services. Multiple services from a unified network.