Transmission Media Chapter 3
Chapter Objectives • Discuss characteristics of cables • List the various types of copper wired cables • Discuss fiber optic cables • List the various types of wireless transmission media
Recall - I • Topology is a pattern of computer devices and describes the way in which these devices are connected • The disadvantages of bus topology are: • Entire network gets affected if main cable breaks • Terminators are required at both ends of backbone cable • Difficult to detect the faulty device • Limited number of devices can be attached • Heavy traffic degrades performance
Recall - II • The advantages of ring topology are: • Easier to mange as compared to Bus network • Handles large volume of traffic • Very reliable and offers great speed • Provides a good communication over a long distance • No terminators are required • Types of mesh topology are: • Full mesh topology • Partial mesh topology
Characteristics of Cables • Segment Length – Length of single wire • Attenuation – Indicates loss of signal • Bandwidth – Amount of data carried by cable • Number of Segments – Maximum number of segments in network • Cost – Copper cables are cheapest, fiber optic cables are expensive • Interference susceptibility and crosstalk – Defines concept of electronic interference on cables
Types of cables • Copper medium is the cheapest mode of data transfer
Coaxial cable • Consist of a solid copper core surrounded by an insulator mainly made up of Poly Vinyl Chloride (PVC) or Teflon • Coaxial cables are less prone to interference (both internal and external)
Types of Coaxial cable • Coaxial cables are mainly divided into four categories
RG58 • Maximum segment length is 200 meters • Interference protection is better than twisted pair cables • Offers resistance of 50 ohms • BNC-T connector is used to connect this cable • Used in thinnet (10BASE2) network • Mostly used in changing environments
RG8 • Maximum segment length is 500 meters • Interference protection is good compared to any copper cable • Offers resistance of 50 ohms • BNC-T or Vampire Tap connector is used to connect this cable • Used in 10BASE5 network
RG6 • Broadband quad-shielded cable that offers an impedance of 75 ohms • Provides lower attenuation characteristics • Useful in cable TV, CCTV and satellite dish antenna
RG59 • Solid conductor is surrounded by a foam polyethylene dielectric • Offers impedance of 75 ohm • Useful in security camera, cable TV and home theatre
Twisted Pair Cables • A pair of cables twisted around each other forms a twisted pair cable.
UTP Cables • Pair of unshielded wires wound around each other • Easily gets affected by EMI, RFI and crosstalk • Cable offers resistance of 50 ohms • Maximum segment length is 100 meters
STP Cables • Pair of wires wound around each other is placed inside shield • Better protection from EMI, RFI and crosstalk as compared to UTP • Offers resistance of 50 ohms • Maximum segment length of 100 meters
Case Study 1 The Mumbai branch of MoneyMaker bank has multiple departments, which are on different floors in the same building. Each department is interconnected using UTP cables. John, the network administrator has set up a client server environment and has used a star topology. The employees of the bank are unable to transmit data and information from one department to another in an efficient manner
Problem Data and information cannot be transmitted between the departments efficiently
Suggested Solution The problem is caused due to EMI emitted by the electrical transformers. John should use STP cables to interconnect the different departments located on each floor as STP provides better protection from EMI. The computers inside each department can be interconnected using UTP cables.
Fiber Optic Medium • Consists of centre glass core surrounded by cladding • Electrical signals are converted into light signals • A phenomenon called as total internal reflection is used for transmission • LED or laser is used to transmit signal
Fiber Optic Cable Characteristics • Bandwidth – Carries large amount of data ranging from 100 Mbps to 1 Gbps • Segment Length – Transmits data signals over larger distance • Interference – No electric signals pass through these types of cables thus providing security
Fiber Optic Cable Types • Fiber optic cables can carry signals in a single direction.
Single Mode Fiber Optic cable • A type of cable that has only a single strand of glass fiber with a thin diameter. • Fiber optic cables that use lasers are known as single mode cable.
Multi Mode Fiber Optic cable • A type of cable that contains a glass fiber with a larger diameter. • It is a 62.5/125 micrometer fiber cable.
Fiber Optic Cable Connectors • Straight Tip (ST) – Joins individual fibers to optical devices • Subscriber Connector (SC) – Attaches two fibers to send and receive signals • Medium Interface Connector (MIC) – Joins fiber to FDDI controller • Sub Miniature Type A (SMA) – Uses individual connectors for each fiber stand • Fiber Jack – Attaches two fibers in snap lock connector
Case Study 2 The Chennai branch of MoneyMaker bank has a database server. All departments are connected to this server using coaxial cables. These departments are unable to retrieve and update information from the server spontaneously. It takes a lot of time to get updated information.
Problem The employees of the bank are unable to retrieve information from the database quickly.
Suggested Solution The problem is caused due to the lower transmission speeds provided by the coaxial cables. These cables provide a maximum transfer rate of 10 Mbps. Thus, if all departments of the bank try to access the information from the server, the speed slows down. To increase the data transfer rate, the network administrator should use UTP Cat 6 twisted pair cables. This cable provides higher bandwidth and higher data transfer rate as compared to coaxial cables.
Wireless Medium • Unguided form of transmission medium • Transmitters and receivers are used to send and receive signals • Involves use of electromagnetic waves such as microwave, infrared, radio waves etc. • Wireless medium is useful in connecting large geographical areas
Radio Waves • Line of sight between devices is not required • Frequencies used are VLF, LF, MF, HF, VHF, UHF, SHF and EHF
Microwave • High frequency EM wave that is used for point to point communication • Microwave Categories: • Terrestrial – Relay towers are used to transmit radio signals between earth stations • Satellite – Radio signals are transmitted between different base stations using satellites
Infrared Transmission • Uses Infrared lights for transmission and reception of signals • Line of sight must be maintained between the devices • Mainly used in LAN environments • LEDs or Injection Laser Diode (ILD) is used to transmit information and photodiodes are used to receive the signals
Case Study - 3 Money Maker Bank plans to link all its branches located across India to a centralized server located in Mumbai. As all the branches are located at various geographical locations, the bank plans to maintain an account of all the transactions of each and every branch. The overhead cost of the current network is too high. So the network administrator wants to use a cost effective way.
Problem Identify the type of setup required to connect various branches to the central server in a cost effective manner.
Suggested Solution The bank should establish a wireless network from all the branches to the central server. This will reduce the cost of installing cables for interconnecting the branches. This will also reduce the overhead cost of maintenance of cables, as it is costlier to connect all the branches, which are spread in India, using cables.
Summary – I • Networking hardware involves all peripheral devices, interface cards and other components such as cables and wires that are used to establish network connection • All cables have certain characteristics such as segment length, bandwidth, crosstalk, attenuation, interference susceptibility, cost and number of segments • Different types of medium are available for transmitting data over the network such as copper medium, fiber optic medium and wireless medium • Copper medium includes coaxial cables and twisted pair cables
Summary – II • Twisted pair cable consists of a pair of cables that is twisted around each other • Two types twisted pair cable are STP and UTP • Crosstalk is a phenomenon in which signals of one wire interfere with the signals transmitted over the other wire • To avoid crosstalk, a pair of wires wound around each other and each pair is placed inside a protective foil wrap • Types of UTP cables are Cat 1, Cat 2, Cat 3, Cat 4, Cat 5, Cat 5e, Cat 6 and Cat 7 • STP cable types include Cat 5e and 150 ohm shielded cable
Summary – III • Coaxial cables consist of a solid copper core that is surrounded by an insulator which is again covered by a mesh like ground wire and an outer cover known as a sheath • Thinwire or RG-58 cable is approximately 0.64 cm in diameter and is used in constantly changing environments • BNC connector is used to connect devices to the thinnet coaxial cable network • RG-8 cable is approximately 1 cm in diameter and used as a backbone cable
Summary – IV • For RG-6 cable, the center conductor is 1.05 mm in diameter and for RG-59 cable is 0.86 mm • A fiber optic cable consists of a centre glass core that is surrounded by a glass cladding, Kevlar fibers and an outer sheath material • LEDs and lasers are used to transmit light signals through the fiber optic cables • There are two types of fiber optic cables available namely single mode and multi mode
Summary – V • The primary types of connectors used to connect fiber cables are ST, SC, SMA, Fiber Jack and MIC • In wireless medium, signals are transmitted through air and space using radio and satellite networks • High frequency radio waves used for point to point communication of audio, data and video signals are called as microwaves • Infrared wireless transmission networks use Infrared lights to send and receive signals