Abstract — In this paper we present in-lab measurement results of radar interference into 4G LTE mobile communications system at 1800 MHz frequency band. Influence of various radar and LTE system parameters including radar antenna rotation effect on LTE traffic throughput loss due to interference is investigated. Measurements have been carried out using a fully functional Huawei LTE DBS 3900 1800 MHz base station connected to live mobile operator network. Paper includes estimation of radar interference levels and provides description of conditions which make the most impact on LTE network quality. Keywords — Interference, Long Term Evolution, LTE, Radars. I. INTRODUCTION FTER the shutdown of the analogue television, several frequency spectrum bands have become available for use in mobile networks. One of these ranges is 790-862 MHz called the 800 MHz band, which in European Union is allocated for mobile operators to deploy the 3GPP Long Term Evolution (LTE) mobile wireless technology [1]. However, for Northern European countries frequency interoperability issue arises due to neighboring Russia and Belarus using the same 800 MHz frequency band for aeronautical radionavigation services. These two different radio systems working on the same frequency band may cause inter-system interference and degrade LTE mobile network performance as well as reducing radar service reliability [2]–[4]. The goal of this research has been to investigate experimentally the influence of radar interference to LTE mobile systems. Instead of 800 MHz frequency band, 1800 MHz system has been chosen due to availability of a fully functional LTE base station on this frequency, with assumption that interference conditions would be similar to 800 MHz band. The experiment consists of LTE base station measurements carried out in a controlled laboratory Mantas Juskauskas, Jevgenij Krivochiza, Jurgis Aleksandravicius, Kestutis Svirskas, Bronislovas Dzindzeleta, Rimvydas Aleksiejunas, Mindaugas Zilinskas are with the VU FF Telecommunications Research Centre, Department of Radiophysics, Sauletekio 9, bldg. III, LT-10222 Vilnius, Lithuania (email: kestutis.svirskas@ff.vu.lt). environment. The following sections describe experimental setup, main measured results and offer conclusions about potential interference impact. II. EXPERIMENTAL SETUP The experimental setup includes LTE base station eNodeB (eNB) Huawei DB3900 and B593 router as terminal user equipment (UE). The interfering RLS1 radar signal has been generated using a software-defined radio platform consisting of a USRP N210 hardware block functioning as a signal generator and GNU Radio software for driving the generator. The interference has been measured by connecting eNB, UE and radar signal generator via cables with controllable attenuators (VAS) and power splitters (PS) that provide variable signal loss and interference level (Fig. 1). Figure 1. Experimental setup for radar interference to downlink LTE signal measurements: LTE 1800 MHz base station (eNB), terminal user equipment (UE), radar signal generator (SDR) controlled by computer (PC1), spectrum analyzer (FSU), computer for received signal measurement (PC2). The measurement process has been carried out according to the terms provided by Communications Regulatory Authority of the Republic of Lithuania and was based on European technical regulation specifications [5]. As an output of the experiment, data traffic throughput loss TP loss has been measured in the downlink and uplink directions between eNB and UE:   %, 100 1 2 1    TP TP TP TP loss (1) where TP 1 and TP 2 are, respectively, traffic throughputs in interference-free conditions and with radar interference. Experimental Investigation of Radar Interference into LTE System at 1800 MHz Frequency Band M. Juskauskas, J. Krivochiza, J. Aleksandravicius, K. Svirskas, B. Dzindzeleta, R. Aleksiejunas and M. Zilinskas A 21st Telecommunications forum TELFOR 2013 Serbia, Belgrade, November 26-28, 2013. 978-1-4799-1420-3/13/$31.00 ©2013 IEEE 28