Radio channel coding is a function in the wide band air interface between the MAC/RLA sublayer and the modulation in the physical layer. Radio channel coding is present in all radios in a system with a wide band air interface.

The radio channel coding functions are used to maximize data throughput and minimize delay through the error-prone Wideband Air Interface (WAI). Figure 2 shows the reference configuration of a WAI transmitter, and Figure 3 shows the reference configuration of a WAI receiver. Wideband Air Interface is defined for Isotropic Orthogonal Transform Algorithm (IOTA) in reference [1]. Diagrams of figure 2 and 3 show the major processing blocks between the radio channel coding and physical layers. These processing blocks exist for all WAI configuration modes (SAM and IOTA) and, except for scrambling, they are described here in the case of IOTA. The scrambler and forward error correction (FEC) coding functions blocks operate at the bit level while the interleaver and modulator operate at the symbol level.

The functions and procedures for radio channel coding include scrambling which is defined and described in the MAC/RLA Layer Specification given in reference [2]. The other functions of forward error correction, interleaving, and mapping to physical layer modulation symbols are defined in the following sections in the case of IOTA.