Presentation on theme: "Computer Communication & Networks Lecture # 07 Physical Layer: Transmission Media Course Instructor: Engr. Sana Ziafat."— Presentation transcript:
Computer Communication & Networks Lecture # 07 Physical Layer: Transmission Media Course Instructor: Engr. Sana Ziafat
Physical Layer Topics to Cover Signals Digital Transmission Analog Transmission Multiplexing Transmission Media
Anything that carry information from source to destination. Physical path between transmitter and receiver in data communication.
Media Issues Frequency range Some media support higher frequencies than others Impairments Different media deform signals differently Some are more susceptible to noise and distortion Cost Were in the real world… Number of receivers Broadcast vs. point-to-point
Transmission Medium and Physical Layer
Types of transmission media Transmission media is divided in to two: Wired or Wireless Wired Media (Guided Media), Is most common and is further divided in to three different types of cabling: Coaxial, Twisted pairs and fiber optic cables. Wireless Media (Unguided Media), which is, in a sense, no media at all, is gaining popularity. Wireless transmission use radio waves or infrared light to transmit data
Guided Media Waves are guided along solid medium. Guided media is also known as bounded media, since the data signals are bounded system. Cabling technology is not limited to copper wire only. Cables can be any physical or conductive media like wires, coaxial cables or fiber optics.
Twisted Pair Cable (Pros & Cons) pro: easy to understand mass production - low cost most widely used medium Cons: prone to electromagnetic interference in power plants, airport buildings, military facilities, cars… Note: In-building networks at our university are almost all twisted pair
Coaxial Cable It carries high frequency signals than in twisted pair cable. Less susceptible to interference or crosstalk.
Performance Coaxial Cable Coaxial cable has much higher bandwidth, the signals weakens rapidly and requires the frequent use of repeaters.
Applications Cable- TV Long distance telephone transmission.
Optical Fiber Made of glass or plastic and transmits signal in form of light. Signal is sent using internal reflection. Relies on total internal reflection Light waves bounce of edge of fiber Channels waves to destination A glass or plastic core is surrounded by a cladding of less dense glass or plastic.
Bending of light ray
Multimode Multiple signals, multiple rays will pass and reflected with different angles Light waves bounce off at different angles. Two types: 1. Step Index 2. Graded Index
Fiber Types Defined by the ratio of diameter of their core to the diameter of their cladding. Fiber types
Fiber-optic Cable Connectors
Performance Optical Fiber
Optical Fiber (Pros & Cons) Pros: Low attenuation Large bandwidth Cons: Relatively new technology Expensive
Comparing optical fiber to UTP Pros: Immune to electro-magnetic interference no crosstalk Reduced need for error detection and correction Enables longer link distances Attenuation unaffected by transmission rate Easier network upgrade Can combine different services: telephony, TV, internet… Lighter than copper cables Corrosion resistant Cons: Optical components have higher cost Expensive deploying protocols
Unguided Media: Wireless Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication.
Wireless Modern wireless digital communication began in the Hawaiian Islands What is the best frequency to use for communication?
Wireless Transmission Waves
Radio Waves Electromagnetic waves ranging in frequencies between 3 kHz and 1 GHz are normally called radio waves. They are omnidirectional (sends signal in all directions). Radio waves are used for multicast communications, such as radio and television, and paging systems.
Omni directional Antenna
Microwaves Having range from 1 to 300 GHz. They are unidirectional. Microwave propagation is line-of-sight. Very high frequency microwaves can not penetrate walls. Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs.
Infrared waves Range from frequencies 300 GHz to 400 THz. Infrared signals can be used for short-range communication in a closed area using line-of- sight propagation.