GXEST104 Introduction to Electronics Engineering Notes PDF

# GXEST104 - INTRODUCTION TO ELECTRONICS ENGINEERING ## Syllabus: ### MODULE IV (Modern Electronics and its applications) - General block diagram of a communication system - Block diagram of Fiber optic Communication system - Concept of AM and FM (No derivation required) - Block diagram of AM and...

# GXEST104 - INTRODUCTION TO ELECTRONICS ENGINEERING ## Syllabus: ### MODULE IV (Modern Electronics and its applications) - General block diagram of a communication system - Block diagram of Fiber optic Communication system - Concept of AM and FM (No derivation required) - Block diagram of AM and FM super-heterodyne receiver - Basic concepts of Wired and Wireless communication - Block diagram of GSM - Comparison of 3G, 4G, 5G and 6G communication technologies - Block diagrams of electronic instrumentation system - Block diagrams of Digital Multimeter - Block diagrams of Function generator - Introduction to CRO and Lissajous patterns - Applications of modern electronics – IoT based smart homes, healthcare and agriculture (Case study only) ## Communication: The communication system is a system which describes the information exchange between two points. The process of transmission and reception of information is called communication. The major elements of communication are the Transmitter of information, the Channel or medium of communication and the Receiver of information. ## Types of Communication Systems Depending on signal specification or technology, the communication system is classified as follows: 1. **Analogue** Analogue technology communicates data as electronic signals of varying frequency or amplitude. Broadcast and telephone transmission are common examples of analogue technology. 2. **Digital** In digital technology, the data are generated and processed in two states: High (represented as 1) and low (represented as 0). Digital technology stores and transmits data in the form of 1s and 0s. ## Communication Systems Depending on the communication channel, the communication system is categorized as follows: 1. **Wired (Line communication)** - Parallel wire communication - Twisted wire communication - Coaxial cable communication - Optical fibre communication 2. **Wireless (Space communication)** - Ground wave communication - Skywave communication - Space wave communication - Satellite communication ## Examples of Communication Systems The following are a few examples of communication systems: 1. Internet 2. Public Switched Telephone Network 3. Intranet and Extranet 4. Television ## General block diagram of a communication system The image depicts a communication system, which is composed of a transmitter and receiver that are connected via a channel and noise source. **Transmitter:** The transmitter is responsible for converting information into a suitable form for transmission. It is composed of: - Information source - Input transducer - Amplifier - Modulator - Antenna **Receiver:** The receiver is responsible for converting the transmitted signal back into its original form. It is composed of: - Receiving antenna - Channel - Noise source - Amplifier - Detector - Demodulator - Output transducer - Information source ## Elements of Communication Systems The definitions of the terms used in the communication system are discussed below. - **Information:** Message or information is the entity that is to be transmitted. It can be in the form of audio, video, temperature, picture, pressure, etc. - **Signal:** The single-valued function of time carries the information. The information is converted into an electrical form for transmission. - **Transducer:** It is a device or an arrangement that converts one form of energy to the other. An electrical transducer converts physical variables such as pressure, force, and temperature into corresponding electrical signal variations. For example, a microphone converts audio signals into electrical signals. The photodetector converts light signals into electrical signals. - **Amplifier:** The electronic circuit or device that increases the amplitude or the strength of the transmitted signal is called an amplifier. When the signal strength becomes less than the required value, amplification can be done anywhere between the transmitter and receiver. A DC power source will be provided for the amplification. - **Modulator:** As the original message signal cannot be transmitted over a large distance because of their low frequency and amplitude, they are superimposed with high frequency and amplitude waves called carrier waves. This phenomenon of superimposing of message signals with a carrier wave is called modulation, and the resultant wave is a modulated wave which is to be transmitted. - **Transmitter:** It is the arrangement that processes the message signal into a suitable form for transmission and, subsequently, reception. - **Antenna:** An antenna is a structure or a device that will radiate and receive electromagnetic waves. So, they are used in both transmitters and receivers. An antenna is basically a metallic object, often a collection of wires. The electromagnetic waves are polarized according to the position of the antenna. - **Channel:** A channel refers to a physical medium such as wire, cables, or space through which the signal is passed from the transmitter to the receiver. There are many channel impairments that affect channel performance to a pronounced level. Noise, attenuation and distortion, to mention the major impairments. - **Noise:** Noise is one of the channel imperfections or impairments in the received signal at the destination. There are external and internal sources that cause noise. External sources include interference, i.e. interference from nearby transmitted signals (cross talk), interference generated by a natural source such as lightning, solar or cosmic radiation, automobile-generated radiation, etc. - **Attenuation:** Attenuation is a problem caused by the medium. When the signal is propagating for a longer distance through a medium, depending on the length of the medium, the initial power decreases. The loss in initial power is directly proportional to the length of the medium. Using amplifiers, the signal power is strengthened or amplified so as to reduce attenuation. Also, digital signals are comparatively less prone to attenuation than analogue signals. - **Distortion:** It is also another type of channel problem. When the signal is distorted, the distorted signal may have a frequency and bandwidth different from the transmitted signal. The variation in the signal frequency can be linear or non-linear. - **Receiver:** An arrangement that extracts the message or information from the transmitted signal at the output end of the channel and reproduces it in a suitable form as the original message signal is a receiver. - **Demodulator:** It is the inverse phenomenon of modulation, i.e., the process of separation of the message signal from the carrier wave takes place in the demodulator. The information is retrieved from the modulated wave. ## Repeaters Repeaters are placed at different locations in between the transmitter and receiver. A repeater receives the transmitted signal, amplifies it and sends it to the next repeater without distorting the original signal. ## Fiber Optic Communication System Fiber optic communication systems are used to transmit information from one place to another by sending pulses of light through an optical fiber. This method enables high-speed, long-distance data transmission with minimal loss and is widely used in telecommunications, internet services, and data centers. ### 1. Transmitter Section - **Information Source:** This is the starting point of the system. It generates the original message, which can be data, audio, or video - **Electrical Signal Generator:** Converts the message into an electrical signal that can be processed and modulated - **Modulator:** The electrical signal is modulated to vary the light source's output. Modulation techniques include amplitude, frequency, and phase modulation - **Optical Source (Laser Diode or LED):** The modulated electrical signal drives a light source, usually a laser diode (for long distances) or an LED (for short distances). The light source generates a coherent light signal proportional to the input data. - **Optical Coupler:** Couples the generated light signal into the optical fiber. This part ensures maximum light signal transfer into the fiber while minimizing losses. ### 2. Transmission Medium (Optical Fiber) - **Optical Fiber Cable:** The optical fiber is the core medium that carries the light signal from the transmitter to the receiver. It consists of a core and cladding that guide light via total internal reflection. - **Amplifiers (Optical Amplifiers):** To maintain signal strength over long distances, amplifiers are used at intervals along the fiber. An Erbium-Doped Fiber Amplifier (EDFA) is commonly used, which amplifies the optical signal without converting it to electrical form. - **Repeaters:** If the transmission distance is very long, repeaters can be used. A repeater converts the optical signal to an electrical signal, amplifies it, and then reconverts it back to an optical signal. ### 3. Receiver Section - **Optical Detector (Photodiode):** At the receiver end, a photodetector (such as a PIN or avalanche photodiode) converts the light signal back into an electrical signal. - **Demodulator:** The demodulator extracts the original electrical signal from the received optical signal, effectively decoding the information. - **Amplifier:** This amplifies the demodulated electrical signal to make it suitable for further processing. - **Signal Processor:** Processes the amplified signal for clarity and error reduction if necessary. - **Output Device:** Finally, the processed electrical signal is sent to an output device, which converts it back into its original form (data, audio, or video). ## How It Works 1. **Signal Generation and Modulation:** The information source creates a signal, which is converted to an electrical format. The modulator then encodes this signal onto a light source. 2. **Light Transmission:** The light signal is transmitted through the optical fiber. Along the fiber, optical amplifiers boost the signal without converting it to electrical form. Repeaters may also be used for very long-distance communication. 3. **Signal Reception and Conversion:** At the receiving end, the optical detector converts the light back into an electrical signal. The demodulator extracts the original message, which is then processed and sent to the output device. ## Advantages of Fiber Optic Communication - **High Bandwidth:** Can carry a large amount of data over long distances - **Low Loss:** Minimal signal attenuation, making it ideal for long-distance communication - **Immunity to Electromagnetic Interference (EMI):** Fiber optic cables are resistant to electromagnetic interference, making them more reliable than metal wires in environments with high EMI Fiber optic communication systems are key in modern telecommunication networks, providing efficient, high-speed data transmission across the world. ## Disadvantages of Fiber Optic Cable - Compared to copper, the cost of producing optic fibre cable is higher. Due to the need for specialised test equipment, installation is more expensive. - Fibre optic cables are more brittle than electrical wires like copper cabling since they are composed of glass. They will break if you bend them too much. - In order to prevent network disruptions, the fibres must be appropriately sliced whether establishing a new fibre optic network or growing an existing one. This is a very sensitive operation, and the signal will suffer if the fibres aren't joined correctly. - The fibre optic cable is extremely prone to being cut or damaged during installation or other construction/renovation activity because of how small and compact it is. ## Uses of Fiber Optic Cable - **Telecommunications:** Optical fiber are widely used in telecommunications. They allow the transfer of data from one place to another, even when the distance is far, with minimal signal loss. - **Cable Television (CATV):** They are also used in cable television (CATV), optical fibers are used to deliver high-definition video and audio signals from the system operator's directly to subscribers. - **Data Centers:** Optical fibers play a important role in connecting servers and networking device inside information centers. - **Networking:** Fiber optic cables are used in Local Area Networks (LANs), Metropolitan Area Networks (MANs), and Wide Area Networks (WANs) to interconnect computers, switches, routers, and other community systems. - **Medical Imaging:** Optical fibers are used in medical along side endoscopes and scientific lasers for diagnostic imaging and surgical approaches. ## Modulation Modulation is an activity or process that takes place in TRANSMITTER section of a communication system. **Communication system = Transmitter + Channel+ Receiver** Modulation is the fundamental requirement of any communication system. The image depicts the process of modulation. It shows the baseband signal, the modulator, the carrier, and the modulated signal (amplitude modulated). The two signals involved in modulation process are: **baseband signal** and **carrier**. 1. **Modulating signal = baseband signal = intelligence signal** - information bearing signal = message signal= input signal - Modulating or baseband signal is LF signal. 2. **Carrier signal** - Carrier: as the name suggests, its job is to carry the signal from one place to other. - Carrier is a HF signal. - Sine or cosine wave are used as carrier in analog modulation techniques such as AM, FM. - Real-life examples of carrier signal: Bus, Train, Airplane etc. ## Modulation definition: Modulation is the process by which some characteristic (amplitude, frequency, or phase) of the carrier is changed according to amplitude of the input (baseband signal). In case of voice signal, the value of amplitude depends on the LOUDENESS. The more loudly we speak, more the amplitude value. - **In Amplitude Modulation (AM):** amplitude of the carrier is changed in accordance with amplitude of modulating signal. - **In Frequency Modulation (FM):** frequency of the carrier is changed in accordance with amplitude of modulating signal. - **In Phase Modulation (PM):** phase of the carrier is changed in accordance with amplitude of modulating signal. Transmitter modifies the message signal in order to transport information easily from one place to other. This modification is called modulation. During this process, Low Frequency (LF) signal changes the High Frequency (HF) signal. By modulation, baseband signal is translated from Low Frequency (LF) to High Frequency (HF). ## Why Modulation? - Easy transportation of baseband signals - Long distance communications Put a stone around paper and through it. Observe the distances travelled with and without stone. Here stone is a carrier and paper is modulating signal. Note that carrier (stone) does not contain any information. Paper only contains information. - **Modulation allows smaller size of antenna.** The effect of modulation is to increase the frequency of input signal so that antenna size is reasonably small and practically achievable. - **For successful transmission and reception of baseband signals** - **To allow use of multiplexing** - **To reduce interference and noise** Carrier frequency $f_c$ must be greater than modulating frequency $f_m$. That means modulating signal is at LF and carrier must be HF sinusoidal (sine wave or cosine wave) signal. Signal resulted from modulation process is called **modulated wave**. ## Advantages of Modulation - It reduces the size of the antenna. - It reduces the cost of wires. - It prohibits the mixing of signals. - It increases the range of communication. - It improves the reception quality. - It easily multiplexes the signals. - It also allows the adjustment of the [bandwidth](https://en.wikipedia.org/wiki/Bandwidth_(signal_processing)). ## Disadvantages of Modulation - The cost of the equipment is higher. - The receiver and the transmitter are very complicated. - For better communication, the antennas for the FM system must be kept closed. - It is not efficient for large bandwidth. - Power wastage takes place. ## AMPLITUDE MODULATION (AM) Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. It is often called AM and is commonly used in transmitting a piece of information through a radio carrier wave. Amplitude modulation is mostly used in the form of electronic communication. “The amplitude of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal.” Which means, the amplitude of the carrier signal containing no information varies as per the amplitude of the signal containing information, at each instant. This can be well explained by the following figures. The image depicts the amplitude modulation process. It shows the message signal, the carrier signal, and an amplitude modulated signals. The amplitude modulated signals’ curves are superimposed on the carrier signal curves. ## Advantages of Amplitude Modulation 1. Transmission and reception of Amplitude modulated signal is comparatively easy 2. The components used in building the AM transmitter and AM receiver are very cheap 3. The circuit used in this is very simple ## Disadvantages of Amplitude Modulation 1. In the transmission of Amplitude modulated signal two sidebands and carrier signal have to be sent. So it requires a high range of bandwidth and more power 2. Since the efficiency of Amplitude Modulation is very low, the messages cannot be transmitted over a particular distance. 3. In the absence of the carrier signal, it is difficult to tune. 4. Transmission and reception of Amplitude modulated waves are very noisy. ## FREQUENCY MODULATION Frequency modulation, commonly referred to as FM, is a common term that we hear in our daily lives. Today, Frequency modulation is used widely in radio communication and broadcasting. ## What Is Frequency Modulation? Frequency modulation is a technique or a process of encoding information on a particular signal (analogue or digital) by varying the carrier wave frequency in accordance with the frequency of the modulating signal. ## Applications of Frequency Modulation - Mostly used in radio broadcasting. It offers a great advantage in radio transmission as it has a larger signal-to-noise ratio, which means that it results in low radio frequency interference. - This is the main reason that many radio stations use FM to broadcast music over the radio. Additionally, some of its uses are also found in radar, telemetry, seismic prospecting, and in EEG, different radio systems, music synthesis as well as in video-transmission instruments. - In radio transmission, frequency modulation has a good advantage over other modulation. - It has a larger signal-to-noise ratio, meaning it will reject radio frequency interferences much better than an equal power amplitude modulation (AM) signal. Due to this major reason, most music is broadcasted over FM radio. The image depicts the frequency modulation process. It shows the message signal, the carrier signal, and a frequency modulated signal. ## Advantages and Disadvantages of Frequency Modulation | Advantages | Disadvantages | | :--------------------------- | :----------------------------- | | Less interference and noise. | Equipment cost is higher. Has a large bandwidth. | - Power consumption is less as compared to AM. - Adjacent FM channels are separated by guard bands. - More complicated receiver and transmitter - The antennas for FM systems should be kept close for better communication. ## Amplitude Modulation vs Frequency Modulation | Amplitude Modulation (AM) | Frequency Modulation (FM) | | :---------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------------------------------------------------------------- | | Frequency and phase remain the same | Amplitude and phase remain the same | | It can be transmitted over a long distance but has poor sound quality | Better sound quality with higher bandwidth. | | The frequency range varies between 535 and 1705 kHz | For FM, it is from 88 to 108 MHz, mainly in the higher spectrum | | Signal distortion can occur in AM | Less instances of signal distortion | | It consists of two sidebands | An infinite number of sidebands | | Circuit design is simple and less expensive | Circuit design is intricate and more expensive | | Easily susceptible to noise | Less susceptible to noise | ## Superheterodyne Receiver **Definition:** Superheterodyne receiver works on the principle of heterodyning which simply means mixing. It is a type of receiver which mixes the received signal frequency with the frequency of the signal generated by a local oscillator. The output of mixer provides a lower fixed frequency also known as **intermediate frequency**. ## Working of Superheterodyne Receiver: Superheterodyne receiver mainly comprised of the following components: The image depicts a block diagram of a superheterodyne receiver. It shows the following components: - RF stage - Mixer - Local oscillator - IF amplifier - Demodulator - Audio amplifier - Power amplifier - Loudspeaker - **Receiving antenna:** The receiving antenna receives the signal which was sent by the transmitter. It sends the received signal for further processing. - **RF amplifier:** The received signal is fed to the RF amplifier stage so as to amplify it, as the signal gets attenuated during long-distance transmission. It is tuned in such a way that it can choose the desired carrier frequency and amplify it. - **Local Oscillator:** This circuit basically generates a signal with a fixed frequency and the output is then fed to the mixer. When we talk about AM broadcast system, the intermediate frequency is 455 KHz that simply means that local oscillator should select such a frequency which is 455 KHz above the incoming signal frequency. - **Mixer:** A mixer simply mixes the carrier frequency with the frequency of the local oscillator. signal generated by the local oscillator. - **IF amplifier:** This section basically amplifies the output of the mixer. IF amplifier provides sensitivity(gain) and selectivity (bandwidth requirement) to the receiver. As it consists of several transformers consisting of pairs of the tuned circuit. Here, the sensitivity and selectivity are uniform and does not show variations as in case of TRF receivers because IF amplifier’s characteristics are independent of that of the received signal frequency as it works on the intermediate frequency. Due to this, the system design is quite easy so as to provide constant bandwidth along with high gain. This section has narrow bandwidth and due to its lower bandwidth, it rejects all other frequency so as to reduce the risk generated from interference. The lower bandwidth accepting nature supports Superheterodyne receivers to give much better performance than other types of receivers. - **Demodulator:** Demodulator is placed exactly after the IF amplifier so that the constant frequency signal is demodulated and the message signal can be extracted from it. - **Audio amplifier:** The original signal is fed to the audio amplifier which does not hold distortion or noise so that it can amplify audio signal to a particular level. - **Power amplifier:** Here, the signal is further amplified to a particular power level which can activate the loudspeaker. The amplified signal is finally fed to the loudspeaker circuit which converts the electrical form of the signal into an audio sound signal which can be heard by the listeners. ## The block diagram of FM super heterodyne is given below The image depicts a block diagram of a FM superheterodyne. It shows the following components: - Receiving antenna - RF amplifier - Mixer - Local oscillator - IF amplifier - Limiter - FM Discriminator - De-emphasis - Audio amplifier - Speaker - AGC detector (optional) 1. The signal received by antenna is amplified using RF amplifier. 2. The amplified signal is then applied to Mixer, in which the second signal comes from a local oscillator. The mixer now has two input frequencies, combining both generates an IF signal of 10.7 MHz . This signal is again amplified using an IF amplifier. 3. The output of IF amplifier is allowed to flow in the Limiter circuit. The limiter circuit gives a constant amplitude signal by removing the noise from the signal it received. 4. The output of the Limiter is then applied to the FM discriminator which recovers the modulating signal. 5. This signal is still not the original modulating signal, therefore, before applying it to the Audio amplifier it is de- emphasized. De- emphasis attenuates the higher frequencies to bring them back to their original amplitudes. 6. The output of this De-emphasis is the audio signal which is applied to the audio stages and then to the speaker. ## Superheterodyne Principle: AM BASED PRINCIPLE The block diagram of Figure 6-2 shows a basic superheterodyne receiver. In the Superheterodyne Principle, the incoming signal voltage is combined with a signal generated in the receiver. This local oscillator voltage is normally converted into a signal of a lower fixed frequency. The image depicts a block diagram of a superheterodyne receiver. It shows the following components: - Antenna - RF stage - Mixer - Local oscillator - IF amplifier - Audio and power amplifiers - Detector - Ganged tuning The signal at this intermediate frequency contains the same modulation as the original carrier, and it is now amplified and detected to reproduce the original information. The superhet has the same essential components as the TRF receiver, in addition to the mixer, local oscillator and intermediate-frequency (IF) amplifier. ## Advantages - **Sensitivity:** Superheterodyne receivers have excellent sensitivity. - **Selectivity:** Superheterodyne receivers have improved selectivity because it’s easier to design a filter with a narrower bandwidth at a lower frequency. - **Frequency stability:** Superheterodyne receivers have superior frequency stability because a tuneable oscillator is easier to realize than a tuneable amplifier. - **Suitable for all modulation schemes:** Superheterodyne receivers are suitable for all modulation schemes. ## Disadvantages - **Complexity:** Superheterodyne receivers are more complex than other receiver designs. - **Power consumption:** Superheterodyne receivers have higher power consumption than other receiver designs. - **Image frequency:** Superheterodyne receivers generate image frequencies, which are signals that appear at twice the IF distance from the desired RF signal. ## WIRED & WIRELESS NETWORK ## What is a Wired Network? In the world of networking, “Wired” refers to any physical medium connected via wires and cables. The cables or wires can be fiber optic, copper wire, or twisted pair. Additionally, they offer high security and generous bandwidth allocations for each user. Therefore, it is a suitable option for a specific section of users. Contrary to wireless connectivity, wired connectivity is quite reliable and has very little delay. This is a key difference between wired and wireless connections. ## What is a Wireless Network? The term “wireless” refers to the transmission of electromagnetic or infrared waves across the air. Additionally, there are antennas to communicate. Users' freedom of movement and ease of deployment are two main advantages of wireless networking. Thus, wireless is a better choice in locations where you cannot deploy wires. In the wired vs wireless network selection process, wireless also offers lower installation costs. However, it is less secure and has a larger latency than cable connectivity. However, users still like wireless communication. ## Difference Between Wired and Wireless Network Wired and wireless networks are two common ways to connect devices and enable communication between them. They differ in several key aspects: | Parameter | Wired network | Wireless Network | | :------------------------- | :----------------------------- | :------------------------------------------------------------------------------------------------------------------ | | Mobility and Roaming | Fix | High | | Medium for Communication | Copper, Fiber, and more | Air | | Security | High | Less | | Reliability | High | Reliability is also lower than Wired Network. | | Speed | High Speed and can also reach 1 Gbps | Speed is less than Wired Network. | | Network Accessibility | Requires physical access | Needs Proximity Required | | Flexibility to change | Less open to change | Greater configuration flexibility | | Installation Charge | High | Low | | Maintenance and Upgradation cost | High | Low | | Related Equipment | Hub, Router, Switch | Access Point, Wireless Router | ## Wired vs Wireless Network: Pros and Cons of Both ### Advantages of Wired Networks: - Wired networks have an unmatched level of reliability when configured and used correctly. You may start using a dependable network as soon as the hubs, switches, and cables are put in place. - In wired vs wireless network, wired networks offer significantly quicker speeds. Additionally, a wired network rarely experiences unexpected traffic. Thus, it is easy to maintain fast speeds at all times. This is because only a few users can connect to it at any given time. - A wired network is very well-protected from illegal and unwanted access. This is possible when the firewalls and other security programs are deployed on the network. ### Disadvantages of Wired Networks: - Clearly, wired networks are relatively limited in terms of mobility. - Installation of the switches, routers, and hubs can be a time-consuming and difficult operation. This is because each device must connect directly to the network. - Using a wired network would require managing many cables. It would not only be unattractive but also inconvenient. ### Advantages of Wireless Networks: - When a wireless network is set up, all of your employees have access to it. Thus, they can access it from practically anywhere in the business. - Compared to creating wired networks, setting up wireless networks often involves a lot less infrastructure. This is another key difference between a wired and wireless network. - Overall, wireless networks require very little equipment to set up. Thus, you can set them much more quickly and simply. ### Disadvantages of Wireless Networks: - Other wirelessly capable gadgets nearby have a larger potential for interfering with or blocking signals. This also makes up an important factor when choosing wired vs wireless network. - In general, wireless networks lack the same level of security as wired networks. - Wireless networks cannot match the speed of wired networks. ## Wifi vs Ethernet An Ethernet connection uses cables to transmit data. Therefore, it is an example of a wired network. But a WiFi connection sends information using wireless waves. Choosing between a WiFi connection and an Ethernet connection is a common challenge. Thus, clearing doubts is a must when deciding on the best connectivity alternatives. - When compared to an Ethernet connection, a WiFi connection sends data over wireless waves. - WiFi connections don’t require cords, giving users more freedom to move around a location while connecting to a network or the Internet. Thus, users must connect a device with an Ethernet cable to use an Ethernet connection to access a network. - A WiFi connection is slower than an Ethernet connection, which also offers higher stability and security. This is a crucial point for ethernet cable vs wifi. ## Block diagram of GSM Draw the block diagram and explain GSM architecture in details indicating all the interfaces. The image depicts a block diagram of the GSM architecture. It shows the following components: - Mobile Station (MS) - Base Transceiver Station (BTS) - Base Station Controller (BSC) - Mobile Switching Centre (MSC) - Operational Support Subsystem (OSS) - Home Location Register (HLR) - Visitor Location Register (VLR) - Authentication Centre (AUC) - Equipment Identity Registry (EIR) - Network Switching (NSS) - Public Networks - PSTN - ISDN - Data Networks - Radio air interface - Abis interface - A interface - SS7 interface The GSM architecture consists of three major interconnected subsystems that interact with themselves and with users through certain network interface. The subsystems are Base Station Subsystem (BSS), Network Switching Subsystem (NSS) and Operational Support Subsystem (OSS). Mobile Station (MS) is also a subsystem but it is considered as a part of BSS. ### 1. Mobile Station (MS): Mobile Station is made up of two entities. #### A. Mobile equipment (ME): - It is a portable, vehicle mounted, hand held device. - It is uniquely identified by an IMEI number. - It is used for voice and data transmission. It also monitors power and signal quality of surrounding cells for optimum handover. 160 characters long SMS can also be sent using Mobile Equipment. #### B. Subscriber Identity module (SIM): - It is a smart card that contains the International Mobile Subscriber Identity (IMSI) number. - It allows users to send and receive calls and receive other subscriber services. It is protected by password or PIN. - It contains encoded network identification details. it has key information to activate the phone. - It can be moved from one mobile to another ### 2. Base Station Subsystem (BSS): It is also known as radio subsystem, provides and manages radio transmission paths between the mobile station and the Mobile Switching Centre (MSC). BSS also manages interface between the mobile station and all other subsystems of GSM. It consists of two parts. #### A. Base Transceiver Station (BTS): - It encodes, encrypts, multiplexes, modulates and feeds the RF signal to the antenna. - It consists of transceiver units. - It communicates with mobile stations via radio air interface and also communicates with BSC via Abis interface. #### B. Base Station Controller (BSC): - It manages radio resources for BTS. It assigns frequency and time slots for all mobile stations in its area. - It handles call set up, transcoding and adaptation functionality handover for each MS radio power control. - It communicates with MSC via A interface and also with BTS. ### 3. Network Switching Subsystem (NSS): It manages the switching functions of the system and allows MSCs to communicate with other networks such as PSTN and ISDN. It consist of #### A. Mobile switching Centre: - It is a heart of the network. It manages communication between GSM and other networks. - It manages call set up function, routing and basic switching. - It performs mobility management including registration, location updating and inter BSS and inter MSC call handoff. - It provides billing information. - MSC does gateway function while its customers roam to other network by using HLR/VLR. #### B. Home Location Registers (HLR): - It is a permanent database about mobile subscriber in a large service area. Its database contains IMSI, IMSISDN, prepaid/post-paid, roaming restrictions, supplementary services. #### C. Visitor Location Registers (VLR): - It is a temporary database which updates whenever new MS enters its area by HLR database. It controls mobiles roaming in its area. It reduces number of queries to HLR. Its database contains IMSI, TMSI, IMSISDN, MSRN, location, area authentication key. #### D. Authentication Centre: - It provides protection against intruders in air interface. It maintains authentication keys and algorithms and provides security triplets (RAND, SRES, Ki). #### E. Equipment Identity Registry (EIR): - It is a database that is used to track handset using the IMEI number. - It is made up of three sub classes- the white list, the black list and the gray list. ### 4. Operational Support Subsystem (OSS): It supports the operation and maintenance of GSM and allows system engineers to monitor, diagnose and troubleshoot all aspects of GSM system. It supports one or more Operation Maintenance Centres (OMC) which are used to monitor the performance of each MS, Bs, BSC and MSC within a GSM system. It has three main functions: - To maintain all telecommunication hardware and network operations with a particular market. - To manage all charging and billing procedures - To manage all mobile equipment in the system. ## Interfaces used for GSM network : (ref fig 2) 1. UM Interface: Used to communicate between BTS with MS 2. Abis Interface: Used to communicate BSC TO BTS 3. A Interface: Used to communicate BSC and MSC 4. Singling protocol (SS 7): Used to communicate MSC with other network The image depicts a GSM network interfaces. It shows the following components: - UE - BTS - BSC - MSC - Other network ## Que 5. Explain the features of GSM. The features of GSM are: 1. **Call Waiting** – Notification of an incoming call while on the handset 2. **Call Hold**- Put a caller on hold to take another call 3. **Call Barring** – All calls, outgoing calls, or incoming calls 4. **Call Forwarding**- Calls can be sent to various numbers defined by the user 5. **Multi Party Call Conferencing**– Link multiple calls together 6. **Calling Line ID** – Incoming telephone number displayed 7. **Alternate Line Service** a.) One for personal calls b.) One for business calls 8. **Closed User Group** – call by dialing last for numbers 9. **Advice of Charge** – Tally of actual costs of phone calls 10. **Fax & Data** – Virtual Office / Professional Office 11. **Roaming**- services and features can follow customer from market to market. ## Que 6. State the various services offered by GSM system. The three services offered by GSM systems are: 1. **Telephone services** 2. **Bearer services** 3. **Supplementary ISDN services** ### Telephone Services: Teleservices include Standard mobile telephone Mobile-originated Base-originated traffic. emergency calling Fax Videotext Tele text, SMS MMS. ### Bearer services: The data services include the communication between computers and packet switched traffic. These services are limited to the first three layers of the OSI reference model. Data may be transmitted using either a Transparent Mode or Non-Transparent Mode. - **Transparent Mode:** Where GSM provides standard channel coding for user data - **Non-Transparent Mode:** Where GSM offers special coding efficiencies based on the particular data interface. ### Supplementary ISDN services: This service are digital in nature and include - Call diversion - Caller line ID - Closed user group - Call barring - Call waiting - Call hold - Connected line ID - Multiparty (Teleconferencing) - Call charge advice ## Comparison of 3G, 4G, 5G and 6G communication technologies | Technology | Year | Use Cases | Frequency | Bandwidth | Avg Speeds | Range | | :----------- | :--- | :----------------------------------------------------------------------------------------- | :-------- | :----------- | :--------- | :--------- | | 1G | 1979 | Analog System, Dropped Calls, Giant Cell Phones | 30 KHz | 2 kbps | 2 kbps | N/A | | 2G | 1991 | Texting (SMS), MMS, Conference Calls, Long Distance Call Tracking | 1.8 GHz | 364 kbps | 40 kbps | 50 mi | | 3G | 2001 | Cheap data transmission, GPS, Web Browsing, SD Video Streaming | 1.6-2 GHz | 3 Mbps | 300 kbps