Mind map

DIGITAL TRANSMISSION

Annis Barakah English

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Digital-to-Digital
- Line Coding
  - - Process of converting digital data (sequence of bits)to digital sgnals
  - Characteristics
    - level representing signal and data element
      - Data element
        The smallest entity that represent a piece of information (bit)
      - Signal element
        The shortest unit (timewise)of a digital signa to carry data element
    - Pulse rate and bit rate
      - Bit/Data rate (bps)
        number of data bits send in 1s
      - Pulse/Signal rate (baud)
        number of signal elements sent in 1s
      - pulse_rate = c x bit_rate x 1/r
    - DC Componenets
      - signal that have zero frequency and the average amplitude is nonzero
        undesirable by
        possibilities of signal distortion
        Omit extra energy residing on the line
    - Self-synchronization
  - Line Coding Scheme
    - Unipolar
      - --> uses only one voltage level --> +ve = bits 1 , -ve = bits 0
    - Polar
      - NRZ(Nonreturn-to-zero)
        NRZ-L
        Bit 1 = -ve , Bit 0 = +ve
        NRZ-I
        Bit 1 = inversion , Bit 0 = No Changes
      - RZ
        Bit 1 = positive to zero , Bit 0 = negative to zero
      - Biphase
        Manchester (RZ+NRZ-L)
        Differential Manchester(RZ+NRZ-l
    - Bipolar
      - Alternate Mark Inversion (AMI)
        Bit 1 = +ve & -ve alternately , Bit 0 = 0V
    - Multilevel
    - Multitransition
- Block Coding
  - Improve line coding performance by including redundant bits to detect errors
  - steps in transformation
    - 1.Division
    - 2.Substitution
    - 3.Line Coding
Analog-to-Digital
- Transmission Modes
  - Parallel Transmission
  - Serial Transmission
  - Asynchronous
  - Synchronous
- Applicable techniques
  - Pulse Code Modulation (PCM)
    - Digitization
      - 2.quantizing
      - 3.encoding
      - 1.sampling
        Based on Nquist theorem
        band-limited
        sampling rate = 2 x highest f
        intervals = 1/sampling_rate
  - Delta Modulation