Load-based downlink scheduling schemes for CDMA networks

The problem of allocating radio resources in the downlink of a CDMA network is studied. In Kwan et al. (2004) the modulation and coding schemes, numbers of multicodes and transmit powers for all mobile stations (MS) are jointly chosen so as to maximize the total allocated bit rate taking into account MS traffic loads. This approach leads to a mixed integer non-linear programming (MINLP) problem which can he computationally time-consuming. In this paper, analytical expressions are derived for optimal resource allocation for a single MS. Based on the single-MS solution, a sub-optimal sequential optimization procedure for multiple MS is presented as an alternative to the joint optimal solution. Numerical results show that when the MS are optimally ordered based on their channel conditions and traffic loads, the sequential optimization procedure yields a total allocated bit rate which is close to that obtained with joint optimization.