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Flashcards

03 Handout 1

Eljin Aguilar Data and Digital Communications easy Inglês 56 flashcards

Flashcards do conjunto (56)

  1. 1simplex transmission half-duplex transmission (HDX), full-duplex transmission (FDX)3 Dataflow Transmissions
  2. 2simplex transmissiondata can only flow in one direction, which is usually from the source to the sink.
  3. 3half-duplex transmission (HDX),data can flow in both directions, but never simultaneously. It first flows in one
    direction, and then in the other direction.
  4. 4full-duplex transmission (FDX)data can flow in both directions simultaneously. It can be viewed as a pair of simplex lines between the source and sink with one line going from the source to the sink and the other going from the sink to the source.
  5. 5Serial data transmissionwhen data is sent or received, the data bits are organized in a specific order since they can only be sent one after another.
  6. 6Asynchronous transmission Synchronous transmission2 types Serial data transmission
  7. 7Asynchronous transmissionis used when data is transmitted as individual characters. In this method, each character is preceded by one start bit and one or two stop bits that are used by the receiver for synchronization purposes.
  8. 8Synchronous transmissionis used to transmit large blocks of data at a time. In this scheme, data is usually organized in frames and each frame is preceded by a flag that consists of a few bits and terminated by another flag.
  9. 9Parallel data transmissionmultiple data bits are transmitted over multiple channels at the same time.
  10. 10Transmission Mediais a communication channel that carries the information from the sender to the receiver in which data is transmitted through the electromagnetic signals via copper wire, fiber optics, atmosphere, water, and vacuum. The function of these transmission media is to carry the information in the form of bits through the network.
  11. 11Guided mediaenables the transfer of information between two or more points that are connected by an electrical conductor.
  12. 12Twisted Pair Coaxial Cable Optical FiberTypes of guided media
  13. 13Twisted Pairit consists of two insulated copper wires that are typically about 1mm thick and twisted together in a helical form.
  14. 14Coaxial Cableto facilitate two-way communication, the cable bandwidth is split into two sets of channels: upstream channels and downstream channels.
  15. 15Optical Fiberrefers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic wire or fiber the optical cable.
  16. 16Unguided mediado not require physical links between two or more devices. Wireless communication is based on radio waves communications in the frequency spectrum.
  17. 17Radio waves Microwaves InfraredTypes of unguided media
  18. 18Radio wavesThese are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Example: AM and FM radios and cordless phones.
  19. 19MicrowavesIt is a line of sight (LOS) transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. These are majorly used for mobile phone communication and television distribution.
  20. 20InfraredInfrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. It is used in TV remotes, wireless mouse, keyboard, printer, etc.
  21. 21AntennasIt is the metal rod or dish that catches radio waves and turns them into electrical signals feeding into something like a radio or television or a telephone system.
  22. 22Log Periodic Antennas Wire Antennas Traveling Wave Antennas Microwave AntennasTypes of antenna
  23. 23Log Periodic AntennasIt is a directional antenna that is made of a series of dipoles placed along its axis at different space intervals of time followed by a logarithmic function of frequency.
  24. 24Wire AntennasThese antennas use a length of wire for transmitting and receiving wavelengths of signals.
  25. 25Traveling Wave Antennas• It is a directional aperiodic antenna that uses a travelling wave as its guiding structure.
    • It is a temporary wave that creates a disturbance and moves along the transmission line at a constant speed.
  26. 26Microwave Antennas• This type of antenna uses microwave transmission to broadcast signals between two or more locations.
    • It is a form of electromagnetic radiation that is used mostly in point-to- point communications and radar.
  27. 27Frequency SpectrumIt is the range of frequencies contained by a signal.
  28. 28ELF VHF LF UHF MF SHF HF EHFgive the frequencies that are designated by the International Telecommunications Union (ITU).
  29. 29EXTREMELY LOW FREQUENCY (ELF)Frequency: 3 KHz to 30 KHz
    Wavelength: 100 km to 10 km
  30. 30LOW FREQUENCY (LF)Frequency: 30 KHz to 300 KHz
    Wavelength: 10 km to 1 km
  31. 31MEDIUM FREQUENCY (MF)Frequency: 300 KHz to 3000 KHz
    Wavelength: 1 km to 100m
  32. 32HIGH FREQUENCY (HF)Frequency: 3 MHz to 30 MHz
    Wavelength: 100 m to 10 m
  33. 33VERY HIGH FREQUENCY (VHF)Frequency: 30 MHz to 300 MHz
    Wavelength: 10 m to 1 m
  34. 34ULTRA HIGH FREQUENCY (UHF)Frequency: 300 MHz to 3000 MHz
    Wavelength: 1 m to 100 mm
  35. 35SUPER HIGH FREQUENCY (SHF)Frequency: 3 GHz to 30 GHz
    Wavelength: 100 mm to 10 mm
  36. 36EXTREMELY HIGH FREQUENCY (EHF)Frequency: 30 GHz to 300 GHz
    Wavelength: 10 mm to 1 mm
  37. 37Wave PropagationThese waves are basically defined as superimposed oscillations of an electric and a magnetic field in space with their direction of propagation perpendicular to both.
  38. 38Ground Wave Sky Wave Space WaveExamples of Propagation
  39. 39Ground WaveThis is used for a low-frequency range transmission, mostly less than 1 MHz. This type of propagation employs the use of large antennas order of which is equivalent to the wavelength of the waves and uses the ground or
    Troposphere for its propagation.
  40. 40Sky WaveThis is used for the propagation of EM waves with a frequency range of 3-30 Mhz. These waves makes the use of ionosphere in which it is the ionized
    part of the earth’s upper atmosphere.
  41. 41Space WaveThis is used for a line of Sight communication (LoS). Space satellite communication and very high- frequency waves use this propagation
    method.
  42. 42Multiplexingis a way of sending multiple signals or streams of information over a communications link at the same time in the form of a single, complex signal.
  43. 43demultiplexingA process when the receiver recovers the separate signals
  44. 44• To make it possible for any network device to talk to any other network device without having to dedicate a connection for each pair. • To make a scarce or expensive resource stretch further. In layman’s term, multiplexing is having multiple inputs and outputs in a single line medium.Two reasons why networks use multiplexin
  45. 45Media Sharing TechniqueThe utilization of such media can be increased by allowing multiple users to transmit their data simultaneously, or close to simultaneously.
  46. 46Frequency-division multiplexing (FDM) Time-division multiplexing (TDM) Spread spectrum (SS)Types of Media Sharing Technique
  47. 47Frequency-division multiplexing (FDM)where the frequency spectrum of the medium is partitioned into multiple frequency blocks called channels that are assigned to users who can use these channels simultaneously without interference from each other.
  48. 48Time-division multiplexing (TDM)where transmission time is divided into non-overlapping time slots that are assigned to users. Transmissions are staggered using a round-robin method to schedule the transmissions.
  49. 49Spread spectrum (SS)where the output signal, which appears like noise, occupies more bandwidth than the original signal.
  50. 50Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Token passing Demand priorityMedia Access Methods
  51. 51Carrier Sensemeans that each station on the LAN continually listens to (tests) the cable for the presence of a signal before transmitting.
  52. 52Multiple Accessmeans that many computers are attempting to transmit and compete for the opportunity to send data (i.e., they are in contention).
  53. 53Collision Detectionmeans that when a collision is detected, the stations will stop transmitting and wait a random length of time before retransmitting the data.
  54. 54Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)Instead of detecting and reacting to collisions, it tries to avoid them by having each computer signal its intention to transmit before transmitting.
  55. 55Token passingIt is a media access method by which collisions are prevented. Collisions are eliminated under token passing because only a computer that possesses a free token (a small data frame) can transmit. This method also allows different priorities to be assigned to different stations on the ring.
  56. 56Demand priorityn demand priority, an active hub is an essential requirement that can control access to the network. The terminals on a network are required to obtain permission from the hub before they start transmitting the bytes over a network.

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easy Data and Digital Communications FlashCards sobre 03 Handout 1, criado por Eljin Aguilar em 23-09-2024.
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Eljin Aguilar
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