In a slow-fading channel, where the coherence time is greater than the latency requirement, there is no definite capacity as the maximum rate of reliable communications supported by the channel, log 2 ⁡ ( 1 + | h | 2 S N R ) {\displaystyle \log _{2}(1+|h|^{2}SNR)} , depends on the random channel gain | h | 2 {\displaystyle |h|^{2}} , which is unknown to the transmitter. If the transmitter encodes data at rate R {\displaystyle R} [bits/s/Hz], there is a non-zero probability that the decoding error probability cannot be made arbitrarily small,