As an inexpensive, flexible, and scalable Internet-access network, we have studied architecture, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET). WIMNET consists of multiple access-points (APs) as wireless routers that are connected through wireless links. To improve the performance by realizing high-speed and simultaneous plural link communications, we have considered use of the smart antenna as a generalized technology of the Multiple-Input-Multiple-Output (MIMO) channel and the Adaptive Array Antenna (AAA). In this paper, we present an extension of the WIMNET simulator for the smart antenna use, which has been developed by our group to estimate the throughput in WIMNET. Through simulations in simple topologies, we investigate impacts of two smart antenna use methods and of interval changes between adjacent nodes including APs and hosts, into the performance of WIMNET.