PAR - 2. Physical layer OSI Model.pdf

2. Physical layer OSI Model Index 1. Introduction to the OSI Model 2. What is the Physical Layer? 3. Functions of the Physical Layer 4. Transmission Media 5. Types of Transmission 6. Physical Layer Devices 7. Standards and Protocols 8. Conclusion Introduction to the OSI Model 1. Introduction...

2. Physical layer OSI Model Index 1. Introduction to the OSI Model 2. What is the Physical Layer? 3. Functions of the Physical Layer 4. Transmission Media 5. Types of Transmission 6. Physical Layer Devices 7. Standards and Protocols 8. Conclusion Introduction to the OSI Model 1. Introduction to the OSI Model The Open Systems Interconnection (OSI) model was developed by ISO. Objective: To establish a network architecture that enables interoperability between different systems. Divides network operations into 7 layers, with each layer responsible for a specific function. OSI Model Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application. The physical layer 2. What is the Physical layer? The first layer of the OSI model. Responsible for transmitting data in the form of electrical, optical, or electromagnetic signals. Works with individual bits (0s and 1s), without interpreting data. Functions: ○ Bit transfer between devices. ○ Defines transmission media and signal encoding methods. 2. What is the Physical Layer? What is a Signal? Definition: A signal is a function that conveys information about a physical phenomenon or system. It is often represented as a variation in a measurable quantity (e.g., voltage, sound, light) over time or space. Types of Signals: 1. Analog Signals: Continuous signals that vary smoothly over time. Examples include sound waves and electrical signals. 2. Digital Signals: Discrete signals that take specific values at certain time intervals, typically represented by binary values (0s and 1s). 2. What is the Physical Layer? Signal Components 1. Frequency (f): The number of cycles a signal completes per second. Measured in Hertz (Hz). 2. Amplitude (A): The maximum value or strength of the signal's variation. Indicates the intensity or power of the signal. 3. Phase (ϕ): Describes the position of the waveform relative to time zero.Measured in degrees (°) or radians. 4. Period (T): The time it takes for one complete cycle of the signal to occur. Inverse of frequency: T=1/f. 2. What is the Physical Layer?  Task 1: Find a signal graph that demonstrates different amplitudes. Act. 2.1 What differences do you notice in the height of the waves? How does the amplitude affect the signal? Task 2: Find a signal graph that demonstrates Signals different frequencies. Compare two signals with different frequencies. Which one oscillates more quickly? What does that tell you about the frequency? Task 3: Find a signal graph that shows a phase shift. How does a phase shift change the starting point of the wave? What do you think this means in real-world applications? 3. Functions of the Physical Layer Signal Encoding: Converts digital data into physical signals (analog or digital). Modulation: Controls signal amplitude, frequency, or phase to adapt it to the transmission medium. Synchronization: Ensures proper timing between the sender and receiver. Basic error detection: Handles control signals like collision detection. Physical topology: Describes the physical arrangement of devices in the network (star, bus, ring, etc.). 3. Functions of the Physical Layer Signal Encoding Signal encoding is the process of converting digital data into physical signals that can be transmitted over a medium, such as wires, fiber optics, or wireless connections. Types: ○ Analog signals: Represented as continuous waveforms. ○ Digital signals: Represented as discrete values. 3. Functions of the Physical Layer Modulation Modulation involves altering a signal’s amplitude, frequency, or phase to adapt it to the transmission medium. This is essential for sending signals efficiently over long distances. Types: ○ Amplitude Modulation (AM): Varies the signal's amplitude. ○ Frequency Modulation (FM): Varies the signal's frequency. ○ Phase Modulation (PM): Varies the signal's phase. 3. Functions of the Physical Layer Synchronization Synchronization ensures that the sender and receiver are aligned in terms of timing. It allows the receiver to correctly interpret the start, duration, and end of each data transmission. Key Components: ○ Clock signals: Synchronize the timing between devices. ○ Asynchronous vs. Synchronous: Asynchronous transmission doesn't require a shared clock signal, while synchronous transmission does. 3. Functions of the Physical Layer Basic Error Detection Basic error detection mechanisms are used to identify errors in data transmission, ensuring that the received data matches the sent data. Techniques: ○ Parity Bits: Adds an extra bit to ensure the data has an even or odd number of 1s. ○ Checksum: Calculates a summary of the data to verify its integrity. ○ Collision Detection: Detects data packet collisions in networks and ensures that the transmission is retried. 3. Functions of the Physical Layer Physical Topology Physical topology refers to the physical arrangement of network devices and cables in a network. It determines how devices communicate with each other. Basic types of Topologies: ○ Star: Devices connect to a central hub or switch. ○ Bus: All devices share a single communication line. ○ Ring: Devices are connected in a circular configuration. Transmission media 4. Transmission Media Guided Media: Twisted Pair Cables (UTP, STP): Common in Ethernet networks. Coaxial Cables: Used in older networks and cable TV connections. Fiber Optic Cables: High speed and large bandwidth; transmits light signals. Unguided Media (Wireless): Radio Waves (Wi-Fi): Wireless networks. Microwaves: Used for long-distance connections. Infrared (IR): Short-range communication, typically within a single room. Laser: Used for high-speed, point-to-point wireless communication. 4. Transmission media Twisted Pair Connectors Ethernet cabling uses standard connectors: ○ RJ45 Connector: Used in Ethernet networks. It has 8 pins and is the most common connector for twisted pair cables. ○ Cabling follows standards like T568A or T568B for the arrangement of the wires inside the connector. 4. Transmission media Coaxial Cable (Ethernet) Although obsolete in many modern networks, coaxial cable was used in older Ethernet networks (10Base2 and 10Base5). Characteristics: ○ Consists of a copper core surrounded by insulation, a metallic mesh shield, and an outer protective layer. ○ Good protection against interference, but limited in speed and flexibility compared to UTP cables. 4. Transmission media Fiber Optic Cabling Transmits data through light pulses (typically lasers or LEDs) instead of electrical signals. Uses a glass or plastic core to carry light, surrounded by a protective layer called cladding. Advantages of Fiber Optics High capacity: Supports greater bandwidths than copper. Low attenuation: Signals can travel long distances with minimal loss. Immunity to electromagnetic interference: Ideal for environments with high electromagnetic noise. Security: Difficult to tap without detection.  Research: Act 2.2 The most commonly used cable, due to being inexpensive and easy to use, is the UTP type. UTP cable Search on the following website: http://www.lanshack.com/cat5e-t utorial.aspx What should we take into account when assembling it, and what should we avoid to achieve the best performance? 4. Transmission media Unguided media: 4. Transmission media Radio Frequency (RF) Frequency: 3 kHz to 300 GHz. Characteristics: Used for long-distance wireless communication. Low frequencies can penetrate obstacles like buildings and trees. Uses: AM/FM radio, television, mobile networks, Wi-Fi, Bluetooth. Advantages: Good range, covers large areas. Disadvantages: Susceptible to interference and spectrum congestion. 4. Transmission media Microwaves Frequency: 1 GHz to 30 GHz. Characteristics: Highly directional signal. Requires aligned antennas, such as point-to-point links. Uses: Telecom backbone networks, satellite communication, LAN networks. Advantages: High data capacity and speed. Disadvantages: Affected by weather conditions (rain, fog) and requires a clear line of sight. 4. Transmission media Infrared Light (IR) Frequency: 300 GHz to 400 THz. Characteristics: Works only in a line of sight. Short range (up to a few meters). Uses: Remote controls, short-distance communication, inter-device connections. Advantages: High security, does not pass through walls. Disadvantages: Very limited range and susceptible to physical obstacles. 4. Transmission media Visible Light Communication Frequency: 430 THz to 770 THz. Characteristics: Uses LED light to transmit data. High speed and security in enclosed areas. Uses: Indoor communication, data transmission in home networks. Advantages: No electromagnetic interference. Disadvantages: Affected by ambient lighting and physical obstacles. 5. Types of transmission Transmission Types: Simplex: One-way communication (e.g., TV). Full-Duplex: Simultaneous two-way communication (e.g., telephones). Half-Duplex: Two-way communication, but not simultaneous (e.g., walkie-talkies). 5. Types of transmission Multiplexing Techniques Frequency Division Multiplexing (FDM): Each signal uses a unique frequency band. Signals are modulated to different frequencies and transmitted simultaneously. Applications: Radio and TV broadcasting, broadband internet (DSL), cable TV. Time Division Multiplexing (TDM): Each signal is assigned a specific time slot in which it can transmit data. Data is interleaved in time, so each user gets a fraction of the total time. Applications: Digital telephony (T1, E1 lines), GSM, optical fiber systems.  Act 2.3 Review Exercise: Explain in your own words what each of the following types of Types of transmission consists of: transmission Synchronous or asynchronous Digital or analog Serial or parallel (multiplexing) Simplex or duplex 6. Physical Layer Devices Repeaters: Amplify and regenerate the signal to extend the transmission distance. Hubs: Basic devices that connect multiple devices in a network, retransmitting signals to all ports. Transmission Media: Cables, antennas, connectors. 7. Physical Layer Standards and Protocols Standards: IEEE 802.3 (Ethernet): Defines standards for wired networks and optic fiber. IEEE 802.11 (Wi-Fi): Defines standards for wireless networks. IEEE 802.15 (Bluetooth): for short-range wireless data transmission Protocols: Modulation techniques. RS-232: Standard for serial data transmission. USB: Universal Serial Bus, for connecting devices and transmitting data. 8. Conclusion In this topic, you have learned: what the OSI model is, specifically the physical layer, the functions of the physical layer, guided and unguided transmission media, the different types of transmission, and the devices used in this layer, along with the protocols and standards defined here. Thanks