This paper considers optimum uplink power control policy that maximizes system capacity without any interference cancellation techniques for Het Nets or cognitive-radio (CR) networks. In system model, there are two types of user. These are Tier2s, which can be tought as secondary user at CR networks or pico/femto-cell user at Het Net, and Tier1 which can be tought as primary user at CR networks or macro-cell user at Het Net. Tier1 suffers from interference is caused by Tier2s due to spectrum sharing. For optimum power control policy under individual peak power constraint at Tier2s and total interference constraint at Tier1 for uplink case at Tier2, DC (difference of convex function) programming is used. Comparison of DC programming and exhaustive search is made and an application is illustrated for more than 3 users at end of paper.