In a LoRaWAN network, the transmission success rate is a critical metric for assessing communication system performance. This study considers the characteristics of LoRaWAN, including end device positions and packet transmission collision probabilities, to decide the transmission data rate for each end node. An optimization model is derived for the end device transmission rate assignment to maximum the transmission success rate. Thus, the LoRa network provides minimize packet collisions rate which enhances the overall system efficiency and provides lower energy consumption. Experimental results demonstrate the paper can effectively improves system performance and reduces overall energy consumption.