A new formulation of the effective Schrödinger equation for a nonparabolic band structure is given. The electron phonon interaction is modeled taking into account the full phonon spectrum of the bulk model of Jacoboni [ Rev. mod. Phys. 55, 645 (1983)]. Scattering at ionized impurities and surface roughness is calculated including screening. Utilizing the discrete subband structure and the nonparabolic energy dispersion relation, transport is simulated taking into account Pauli's exclusion principle. It is shown, that the number of subbands used for the calculation of transport has a strong impact on the resulting mobility. The simulated drift velocity is compared with experimental data and good agreement is found for a wide range of temperature, doping concentration and bias conditions. The universal relationship between mobility and effective field found experimentally for ohmic transport[2] also holds in the case of nonequilibrium transport. The obtained saturation drift velocity is the same as in the bulk case and independent of the confining field.