This paper analyzes the throughput performance of IEEE 802.11b Wireless Local Area Network (WLAN) with one access point. The IEEE 802.11b is a wireless protocol standard. In this paper, a wireless network was established which has one access point. OPNET IT Guru Simulator (Academic edition) was used to simulate the entire network. Thus the effects of varying some network parameters such as the data-rate, buffer-sizes, and fragmentation threshold were observed on the throughput performance metric. Several simulation graphs were obtained and used to analyze the network performance.