Transmission rate scheduling with fairness constraints in downlink of CDMA data networks

Abstract

In this paper, we focus on the throughput-maximizaiion problem in the downlink of code-division multiple-access (CDMA) data networks. Proper transmission-rate scheduling of data service in downlinks can reduce intracell interference, hence maximizing the throughput of the downlink. A variety of research has been done on the use of transmission-rate scheduling to maximize the total throughput in a CDMA network. Among this research, only the best effort method can be applied as a practical scheduling scheme. In this method, however, some users may have no chance of receiving their data at all during the whole scheduling time horizon, since this method considers only throughput maximization. In this paper, we consider fairness among users while maximizing the total throughput of the system. Since the interference from cells neighboring a certain cell to each user in the cell is stochastic, this problem becomes a stochastic optimization problem. The fairness among users is modeled in two different ways: a hard minimum requirement constraint and a soft minimum requirement constraint for each user. Transmission-rate scheduling methods for the two models have been suggested and tested through numerical simulation. Our simulation test showed that the method for the model with soft constraint has excellent performance in both throughput and fairness.