Field Experiment of Localization Based on Machine Learning in LTE Network

In mobile communications networks, if we can estimate the location of each user equipment (UE) with high accuracy, efficient cell planning and network optimization become possible. However, it is difficult for operators to estimate the location of most commercial UEs because they cannot feedback their location information directly to their serving base stations with the exception of UEs with Minimization of Drive Test (MDT) functions specified in LTE Release 10. Radio Frequency (RF) fingerprint method is known as an effective localization method, with which we can estimate the location of UEs with only RF signature and location information beforehand. In LTE, RF fingerprint database can be collected by conducting drive tests or using measurement data from UEs compatible with MDT. Although the estimation accuracy can be better with more RF signatures, the increase in the amount of RF signatures causes the increase in the feedback, which consumes the uplink capacity and UE battery. Furthermore, keeping all RF signatures in database is inefficient because some RF signatures do not have effect on improving estimation accuracy. Hence, it is important to clarify the effect of each RF signature and use only effective ones in the localization. In this paper, we conducted a field experiment to create an RF fingerprint database in dense urban area, and evaluated the effectiveness of each RF signature by making several localization models based on machine learning. Eventually, we clarified minimum RF signatures required to operate RF fingerprint localization in LTE network.