Multiple access

  1. Frequency Division Multiple Access (FDMA)
    • Divides the bandwidth of a channel into several smaller frequencies bands.
    • ex: TV
  2. Crosstalk
    Causes interference on the other frequency and may disrupt the transmission
  3. Time Division Multiple Access (TDMA)
    • Divides the transmission time into several slots
    • Each user is assigned the entire frequency for the transmission
  4. Advantages of TDMA
    • Uses the bandwidth more efficiently
    • Allows both data and voice transmissions to be mixed using the same frequency
  5. Code Division Multiple Access (CDMA)
    • Uses direct sequence spread spectrum (DSSS) with a unique digital spreading code (PN code)
    • Before the transmission occurs high-rate PN code is combined with the data to be sent
    • the longer the code the more users.
  6. CDMA Advantages
    • Can carry up to three times the amount of data as TDMA
    • Transmissions are much harder to eavesdrop on
    • A would-be eavesdropper must also know the exact chip in which the transmission starts
Card Set
Multiple access
Describe how different factors affect the design of a radio system