In this paper we discuss rate control for multiuser multi-carrier systems, where the transmitter has a single antenna and is subject to a PSD mask limitation while the receiver has multiple receive antennas. This case is typical in many systems, where each mobile unit has a single transmit stream, and its transmit PSD is limited by regulatory constraints. This scenario is also typical DSL upstream transmission with a vector receiver. In both scenarios we are given a vector of target rates determined by the network operator and we want to set up a transmission strategy for each user at each tone. We show that in this case the problem can be solved using linear programming, rather than general convex optimization. The proposed rate allocation technique has two important applications. First, it provides a computationally simple tool to evaluate the optimal performance of multiple access systems under various operator utility functions. Second, it can serve as a practical tool for rate control of multiple access OFDM systems.