Novel rate allocation scheme to minimize average transmission delay in CDMA uplink

Abstract

An optimum rate allocation scheme for code division multiple access (CDMA) uplink, which minimizes the average transmission delay of data users under the system resource constraint, is derived and evaluated in this paper. The average transmission delay minimization issue is formulated as a constrained optimization problem and solved using the Lagrange multiplier method. It is found that the proposed allocation rule achieves the minimum average transmission delay of data users compared to the other two conventional rate allocation schemes. Moreover, the proposed approach obtains much less transmission delay against the other two schemes especially when the traffic load is higher, which indicates that our scheme is more efficient in the high load systems. Numerical examples also show that the system parameters such as outage probability constraint and power control errors have great impact on the delay performance. Since our work is based on the imperfect power control model, it is more appropriate to the practical CDMA systems, especially for the delay-sensitive services.