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In a cellular telephone system, a repeater is one of a group of transceivers in a geographic area that collectively serve a system user.

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  3. 3. 5 GHz ANT 1
  4. 4. Repeater AJAL. A. J Assistant Professor –Dept of ECE, Federal Institute of Science And Technology (FISAT) TM MAIL:
  5. 5. The Wireless Revolution • A Radio Communications Link Transmitter Receiver Antenna Antenna Transmission Line Transmission Line Radio Waves
  6. 6. Telephone Switching Source: BTales_198302.htm Laura Robbins and Maud Ware at telephone switchboard 1910
  7. 7. The Role of the Internet Telegraph Key and Sounder Image from: Telegraph.html Telegraph Relay Office Image from: Telegraph Key and Sounder Telegraph Relay Office • The Telegraph and Message Switching
  8. 8. 1• 1) In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium. In electromagnetic media, repeaters overcome the attenuation caused by free-space electromagnetic-field divergence or cable loss. A series of repeaters make possible the extension of a signal over a distance. • Repeaters remove the unwanted noise in an incoming signal. Unlike an analog signal, the original digital signal, even if weak or distorted, can be clearly perceived and restored. With analog transmission, signals are restrengthened with amplifiers which unfortunately also amplify noise as well as information.
  9. 9. 2• 2) In a wireless communications system, a repeater consists of a radio receiver, an amplifier, a transmitter, an isolator, and two antennas. The transmitter produces a signal on a frequency that differs from the received signal. This so-called frequency offset is necessary to prevent the strong transmitted signal from disabling the receiver. The isolator provides additional protection in this respect. • A repeater, when strategically located on top of a high building or a mountain, can greatly enhance the performance of a wireless network by allowing communications over distances much greater than would be possible without it.
  10. 10. 3 • 3) In satellite wireless, a repeater (more frequently called a transponder) receives uplink signals and retransmits them, often on different frequencies, to destination locations.
  11. 11. 4• 4) In a cellular telephone system, a repeater is one of a group of transceivers in a geographic area that collectively serve a system user.
  12. 12. 5 • 5) In a fiber optic network, a repeater consists of a photocell, an amplifier, and a light-emitting diode (LED) or infrared-emitting diode (IRED) for each light or IR signal that requires amplification. Fiber optic repeaters operate at power levels much lower than wireless repeaters, and are also much simpler and cheaper. However, their design requires careful attention to ensure that internal circuit noise is minimized.
  13. 13. 6• 6) Repeaters are commonly used by commercial and amateur radio operators to extend signals in the radio frequency range from one receiver to another. These consist of drop repeaters, similar to the cells in cellular radio, and hub repeaters, which receive and retransmit signals from and to a number of directions.
  14. 14. 7• 7) A bus repeater links one computer bus to a bus in another computer chassis, essentially chaining one computer to another.
  15. 15. Wireless PropagationWireless Propagation Ground WaveGround Wave
  16. 16. Wireless PropagationWireless Propagation Sky WaveSky Wave
  17. 17. Wireless PropagationWireless Propagation Line of SightLine of Sight 1.Above 30 MHz, neither ground wave nor sky wave propagation modes operate, and communication must be by line of sight 2. For satellite communication, a signal above 30 MHz is not reflected by the ionosphere and therefore a signal can be transmitted between an earth station and a satellite overhead that is not beyond the horizon. 3. For ground-based communication, the transmitting and receiving antennas must be within an effective line of sight of each other. The term effective is used because microwaves are bent or refracted by the atmosphere. The amount and even the direction of the bend depends on conditions, but generally microwaves are bent with the curvature of the earth and will therefore propagate farther than the optical line of sight. In this book, we are almost exclusively concerned with LOS communications.
  18. 18. Multipath InterferenceMultipath Interference
  19. 19. HISTORY • The term "repeater" originated with telegraphy in the 19th century, and referred to an electromechanical device used to regenerate telegraph signals. • Use of the term has continued in telephony and data communications.
  20. 20. mechanically coupled carbon microphones • Before the invention of electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters.
  21. 21. negative resistance mercury lamps • After the turn of the century it was found that negative resistance mercury lamps could amplify, and they were used.
  22. 22. @ 1916 • The invention of audion tube repeaters around 1916 made transcontinental telephony practical. In 1916, he broadcast the first radio advertising (for his products), was the first to report presidential election results via radio and led the first radio broadcast of music. SERVICE 2 SOCIETY
  23. 23. • De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use of electronics. Born : August 26, 1873 Council Bluffs, Iowa Died: June 30, 1961 (aged 87) Hollywood, California Spouse (s) Lucille Sheardown (m.1906; divorced) Nora Stanton Blatch Barney (m.1907-1911; divorced) Mary Mayo (m.1912-?; divorced) Marie Mosquini (m.1930-1961; his death)
  24. 24. This vacuum tube was a device that allowed a voice to be amplified.
  25. 25. Marie De ForestWIFE
  26. 26. bin/fg.cgi?page=gr&GRid=271 • He is credited with inventing talking movies. His inventions led him to be dragged through several legal battles concerning patent conflicts and investor concerns. • He won in the courts, but the cases took their toll in his professional life as many of his colleagues lost their trust in him. • However, in 1959 he was awarded an Academy Award for “his pioneering inventions which brought sound to the motion picture” and is recognized by many as the "Father of Radio."
  27. 27. @ 1930 • In the 1930s vacuum tube repeaters using hybrid coils became common place, allowing the use of thinner wires.
  28. 28. 1950 • In the 1950s negative impedance gain devices were more popular, and a transistorized version called the E6 repeater was the final major type used in the Bell System before the low cost of digital transmission made all voiceband repeaters obsolete.
  29. 29. late 20th century • Frequency frogging repeaters were commonplace in frequency-division multiplexing systems from the middle to late 20th century. • In telecommunication, the term frequency frogging has the following meanings: 1. The interchanging of the frequencies of carrier channels to accomplish specific purposes, such as to prevent feedback and oscillation, to reduce crosstalk, and to correct for a high frequency response slope in the transmission line. 2. In microwave radio relay systems, the alternate use of two frequencies at repeater sites to prevent feedback and oscillation.
  31. 31. Break Time For queries – 10 minutes
  32. 32. In telecommunications, a repeater is an electronic device that receives  a signal and retransmits it at a higher level or higher power, or onto the other side of an  obstruction, so that the signal can cover longer distances. 
  33. 33. In telecommunication, the term repeater has the  following standardized meanings: 1. An analog device that amplifies an input signal regardless of its nature (analog or digital). 2. A digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.
  34. 34. digital repeaters are used to attain greater distances. The digital repeater receives the digital signal, recovers the patterns of 0’s and 1’s and retransmits a new digital signal. Digital Transmissions
  35. 35. "digipeater" • A "digipeater" is a blend meaning "digital repeater", particularly used in amateur radio. • Store and forward digipeaters generally receive a packet radio transmission and then retransmit it on the same frequency, unlike repeaters that receive on one and transmit on another frequency.
  36. 36. The first layer of the OSI model • In computer networking, because repeaters work with the actual physical signal, and do not attempt to interpret the data being transmitted, they operate on the physical layer, the first layer of the OSI model.
  37. 37. Receiver Communication channel Transmitter Transmission System Input signal Output signal
  38. 38. Attenuated & distorted signal + noise Equalizer Recovered signal + residual noise Amplifier Amp. Analog Transmission
  39. 39. Source Amplifier DestinationAmplifier Analog Transmission Source Repeater DestinationRepeater Digital Transmission
  40. 40. Amplifier Equalizer Timing Recovery Decision Circuit. & Signal Regenerator Digital Transmission Repeater (digital signal)
  42. 42. The Context – communication devices and underlying networks network protocol data link physical Router data link physical application transport network data link physical Host application transport network data link physical Host data flow MAC (data link) physical Bridge/Switch physical WAN LAN e.g. Gigabit Ethernet - fibre optic cable e.g. 100BaseTx -CAT 5, 802.11 e.g. PSTN – modem, satellite, TDM point-to-point leased line ATM, Frame Relay, X.25, CDMA (e.g. CDMA-1X), etc.
  43. 43. Single Repeater
  44. 44. Microwave Link Now the frequency is shifted to µwave range Same frequency
  45. 45. Internet Gateway Relay
  46. 46. Advantages 1. Makes it easy to expand a network over a large distance. 2. Connection between various types of media [e.g. fibre optic, UTF, coaxial cable] is possible. Unicode Transformation Format
  47. 47. Disadvantages 1. Traffic cannot be filtered to ease congestion. 2. A repeater cannot work across multiple network architectures.
  48. 48. Why are repeaters and regenerators used in communication? • A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.
  49. 49. Analog Long-Distance CommunicationsAnalog Long-Distance Communications • Each repeater attempts to restore analog signal to its original form • Restoration is imperfect – Distortion is not completely eliminated – Noise & interference is only partially removed • Signal quality decreases with # of repeaters • Communications is distance-limited • Still used in analog cable TV systems • Analogy: Copy a song using a cassette recorder Source DestinationRepeater Transmission segment Repeater. . .
  50. 50. Digital Long-Distance CommunicationsDigital Long-Distance Communications • Regenerator recovers original data sequence and retransmits on next segment • Can design so error probability is very small • Then each regeneration is like the first time! • Analogy: copy an MP3 file • Communications is possible over very long distances • Digital systems vs. analog systems – Less power, longer distances, lower system cost – Monitoring, multiplexing, coding, encryption, protocols… Source DestinationRegenerator Transmission segment Regenerator. . .
  51. 51. Real Time Deployment
  52. 52. Analog-Analog Repeaters
  53. 53. Analog-Digital Repeaters
  54. 54. Digital-Digital Repeaters
  55. 55. Configuring an Analog Repeater
  56. 56. Go to “Channel -> Analog Channel” and select the channel which the repeater is working on.
  57. 57. How many repeaters can be connected in the back-to-back way? • To ensure an optimal performance, only two repeaters are supported at the present stage.
  58. 58. Can the communication go with the same frequency? • It is recommended to use different frequencies to avoid signal interference.
  59. 59. How to deal with back-to-back function failure? • When the back-to-back function does not work, take the steps below: • 1) Check whether the accessory pin cable is connected properly. If not, • reconnect it; • 2) Restart the repeater; • 3) If the above steps do not help, please contact your dealer.
  61. 61. Alaska
  62. 62. Alaska