One of the wireless network technologies that can be used for ITS (Intelligent Transport Systems) needs, in particular for providing vehicle passengers with access to the data transmission network, is IEEE 802.11 WLAN. To evaluate the performance of such automotive wireless access networks it is necessary to perform experimental measurements. By conducting the throughput measurements in WLAN-based automotive communications testbed, it was observed, that the throughput of the communication channel decreases and the received signal becomes weaker as the vehicle moves away from the wireless access point (AP). The aim of the research is to verify theoretically whether there is a correlation between the received signal power level and the throughput of the communication channel depending on the distance to the transmitter. To calculate the received signal power depending on the distance to the transmitter, a log-normal signal propagation model can be used, which takes into account random signal fluctuations, which are described by the Nakagami distribution. Further, using the obtained result, Shannon's theorem can be used to calculate the maximum theoretical throughput of the communication channel. The analysis of the obtained results shows, that a correlation exists between the received signal power level and the throughput of the communication channel depending on the distance to the transmitter. The performed theoretical calculations justify the experimentally obtained results.