The wireless communication channel is the critical parameter that affects the throughput in the LTE-A network. The user equipment measures the quality of the wireless channel as the channel quality indicator (CQI) value and transmits it to eNodeB. The eNodeB uses the CQI value to select the adaptive modulation and coding method to achieve the highest throughput. This study analyzes the LTE-A network based on actual field measurements. Measurements were taken at 80 different locations in Samsun (Turkey) city center using TEMS Investigation software. RSRP, RSRQ, SINR, CQI, and throughput values were recorded for each measurement in a stationary position while downloading 500 MB of data. Then, the averages of these recorded data were calculated, and detailed analyses were performed. At the end of the study, the effects of RSRP, RSRQ, SINR, and CQI on the throughput value in the LTE-A network were examined, and a novel mathematical model was proposed that gives the relationship between them with 88.85% accuracy. It has also been observed that the accuracy of the proposed model can be increased by 4% with GRNN. In the last stage of the study, a new CQI mapping method based on real-field measurements for the LTE-A system was developed.