Rate control is an important issue for video streaming in cellular networks. This paper describes an equation based rate control for video streaming over cellular networks. In our method, the sending rate is calculated as a function of round trip time (RTT), loss event rate (p), packet size (s) and new control parameters alpha and beta that are able to provide flexible and smooth transmission rate and slowly responsible congestion control and also adaptability to unpredictable wireless channel conditions. We have simulated this method in UMTS and according to analytic and simulation results, this method in addition to network stability increase throughput with low fluctuation.