Static versus Dynamic Channel Allocation

• given a single channel with exponential arrivals at a mean arrival rate of 1/ __frames/sec

• assume frame sizes are exponential so that the mean time to send a frame is 1/µ seconds

• then the mean frame send time is T = 1/ (µ - _)

• divide this channel into N static subchannels using either FDM or TDM then

  • the arrival rate is 1/ _N and
  • the mean frame send time is 1/ µN

• then the mean frame send time is NT = N/ (µ - _)

=> want dynamic allocation as in CSMA/ CD , FDDI, DQDB, spread spectrum, ...

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