EFM

8/16 Modulation

The lowest layer of the communications channel is the 8/16 channel code, which helps reduce DC energy (illegal run-lengths of '1' or '0' bits), effectively lowering the SNR threshold for the pickup signal. Although half the channel rate is doubled thanks to the 8/16 code, the overall user throughput for the desired uncorrected rate of 1x10^-3 is greater because of it. The advantage of the 8/16 code is:

  • Small DC component
  • No merge bits (Red Book)
  • Applicable RAM
  • Simple decoding circuits

    From 16 channel bits, 8 user data bits are produced.