Wireless power transfer has attracted a great deal of attentions recently, due to its ability to extend the lifetime of IoT devices. In this paper, a joint downlink (DL) and uplink (UL) optimization for sum throughput maximization in a two user wireless powered communication network (WPCN) is considered. During DL, a hybrid access point (H-AP) sequentially broadcasts energy and transmits information to each user, and during the UL, each user transmits information to the H-AP, and harvests energy from other users’ UL information transmissions. Each user exploits the total harvested energy during both DL and UL to support its circuit power consumption for the DL information receiving and decoding and WET in the UL as well as information transmit power in the UL. Under this setting, we maximize the weighted sum throughput over both DL and UL by optimizing transmit power and time allocations at H-AP and users, subject to the H-AP’s and each user’s transmit power constraint, time allocation constraint and energy harvesting constraints at each user. However, this problem is found to be a non-convex optimization problem. We transform this problem into a convex optimization problem, and obtain the optimal solutions using an efficient algorithm.