Example 2: A V.92 modem for the telephone network can transfer 56,000 bit/s downstream and 48,000 bit/s upstream over an analog telephone network. The modulation efficiency in bit/s is the gross bit rate (including any error-correcting code) divided by the bandwidth.Įxample 1: A transmission technique using one kilohertz of bandwidth to transmit 1,000 bits per second has a modulation efficiency of 1 (bit/s)/Hz. In the latter case, a "bit" refers to a user data bit FEC overhead is always excluded. Link spectral efficiency is typically used to analyse the efficiency of a digital modulation method or line code, sometimes in combination with a forward error correction (FEC) code and other physical layer overhead. Alternatively, the spectral efficiency may be measured in bit/symbol, which is equivalent to bits per channel use ( bpcu), implying that the net bit rate is divided by the symbol rate (modulation rate) or line code pulse rate. It is the net bit rate (useful information rate excluding error-correcting codes) or maximum throughput divided by the bandwidth in hertz of a communication channel or a data link. The link spectral efficiency of a digital communication system is measured in bit/ s/ Hz, or, less frequently but unambiguously, in (bit/s)/Hz. 2 System spectral efficiency or area spectral efficiency.
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