Abstract-In this paper, we consider joint uplink and downlink rate allocations over a multi-access/broadcast channel pair in a single-cell system. We assume a network of heterogeneous users, where the uplink utility of each user is held as private information and is unknown to the base station. The challenge is to design an optimal rate allocation scheme in the presence of such incomplete information when considering strategic users. Here, we provide an incentive-compatible mechanism that leverages downlink demand to ensure that users truthfully reveal their uplink utilities, enabling the socially optimal uplink rate allocation. In addition, we give numerical results on a kind of efficiency of downlink allocations for two specific uplink multiaccess channels: information theoretic AWGN MAC channel, and CDMA-based uplink.