An overview of variable rate speech coding for cellular networks

Variable rate speech coding is a critical system component for achieving very high capacity in future generation multiple access systems for cellular networks. A significant capacity gain comes from exploitation of the large fraction of the time during which a speaker is idle in a two-way conversation. Additional capacity gain can also be achieved by exploiting the time-varying entropy of active speech. While CDMA and packet-based multiple access systems, e.g. PRMA, are naturally suited for variable rate coding. TDMA can also be designed to benefit from voice activity patterns.<>