4G LTE on the Road - What Impacts Download Speeds Most?

In the context of continually growing data volumes, which have to be processed and transmitted in modern and future road traffic, the importance of the LTE technology will increase. While the extensively evaluated 802.11p standard shows its strength in regards to road safety applications, data-intensive comfort and infotainment services, which cause high data volume mainly in downlink direction, can best be provided by LTE. Therefore, the investigation of the download performance and availability is essential. In this paper, we present measurement results that evaluate how LTE's download speed is affected by relevant parameters. We perform two measurement campaigns in a major commercial LTE network. In a mobile scenario, we analyze position dependent parameters, such as frequency bands, the corresponding bandwidth, and the channel's signal quality, i.e., SINR and RSSI. Furthermore, a statistical performance evaluation provides insight into the parameters' impact on the download speed and their consistency in urban and rural areas. In addition, we compare the influence of main transport protocols, i.e., TCP and UDP. Finally, we identify diurnal and weekday dependent patterns. Concerning the download speeds in LTE, our results show on the one hand a higher spatial variability in cities and on the other hand that the signal quality and channel bandwidth are the most important influencing factors.