Abstract—This paper presents the description, measurements, and analysis of an investigation into the path loss channel characteristics of a complex building environment using the College of Engineering building of Afe Babalola University, Ado-Ekiti, Nigeria as a case study. The study is conducted on the first floor of the building, which is compartmentalized into five scenarios. The measurements are performed in the distinctive line-of-sight and non-line-of-sight paths. Over 90% of the measurements taken are in the non-line-of-sight environment of the complex building. The wideband sliding correlator channel sounder measurement technique of 1.2 GHz centre frequency was performed using the National Instrument Universal Software Radio Peripheral (NI USRP) 2920/GNU (GNU’s Not Unix) radio testbed. Key statistical considerations associated with path loss are calculated and the path loss equation model for the non-line-of-sight and line-of-sight of the entire first floor of the complex building is obtained. The results of the investigation show that an increase in path loss is a function of distance. The calculated path loss exponents were used to rate the performance of the wireless communication channel. The values obtained were found to be in tandem with the existing path loss metrics.  Also, the radio propagation along the enclosed passages and indoor environments experienced low path loss, while the radio propagation along the ornamental trees encountered large path loss. Consequently, the results of the linear regression model and the log-normal model equation of Nonline of Sight ( NLOS) and Line of Sight (LOS) results are somehow correlated. These results are useful in predicting the path loss of the radio signal at any specific distance from the transmitter to the receiver in any environment similar to the one under investigation. Also, as a planning and coverage optimization tool for wireless communication designers.