On the tradeoff between throughput and fairness on the reverse link of a 3G CDMA network

Abstract

Third generation (3G) networks will provide support for high speed applications to its users in both the forward and reverse directions. In the forward direction, this is achieved by time sharing users over one or more high speed packet data channels. Users are scheduled based on their application needs as well as the mobile operator's objectives. On the reverse link, two options are possible for serving users, rate control and scheduling. Scheduling provides fine control of reverse link resources but at the expense of complexity and signaling overhead. Two forms of rate control are possible, common rate control and dedicated rate control. Dedicated rate control is similar in concept to scheduling, but is limited to one rate level change per user. In common rate control, each mobile independently determines its reverse link rate using load information that is broadcast by the base station on a periodic basis. The algorithm used by each mobile to determine its transmission rate should again be determined based on the needs of the application as well as the operator's overall objectives. One option is to be completely fair and provide all mobiles (as much as is physically possible) with identical transmission rates (i.e., the performance objective used for voice users). Another option is to allow mobiles to use rates based on their reverse link channel conditions (the proportionally fair performance objective used in the forward packet data channel). We compare the throughput and fairness of these two approaches.