Measurement-Based Investigation of 60 GHz Broadband Transmission for Wireless In-Car Communication Michael Peter, Robert Felbecker and Wilhelm Keusgen Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut Einsteinufer 37, 10587 Berlin, Germany E-mail: michael.peter@hhi.fraunhofer.de Joachim Hillebrand BMW Group Research and Technology Hanauer Straße 46, 80788 Munich, Germany E-mail: Joachim.Hillebrand@bmw.de Abstract—In this paper we investigate the 60 GHz in-car wide- band radio channel to assess the feasibility of 60 GHz high bit rate radio communication inside a car. The investigations are based on a measurement campaign comprising different application- oriented transmission scenarios and propagation conditions. We analyze the channel gain, time dispersion and frequency selec- tivity. Finally, we derive the achievable signal-to-noise ratio and cover interference aspects. I. I NTRODUCTION Today, premium class cars are equipped with a multitude of electronic entertainment and infotainment devices like DVD players, in-car-TV, navigation systems, cameras etc. Those devices are typically connected to each other via the automo- tive cable harness consisting of wires for various bus systems and point-to-point links. The cable harness in current vehicles has a significant weight that may exceed 30 kg. In particular, when utilizing higher bit rates for the data communication, this figure would even grow further due to necessary cable shielding and bulkier connectors. It becomes evident that a reduction of CO 2 emissions in cars can also be achieved by utilizing alternative ways of data communication within the vehicle. Future broadband 60 GHz systems are supposed to operate in the unlicensed band from 57 to 64 GHz and are a can- didate for wireless indoor [1] and in-cabin [2] high speed internet access as well as real-time video streaming. It is well known that the channel characteristics strongly depend on the propagation environment [3]. Results in the literature mostly refer to 60 GHz indoor channels [4]. Very few results are available for more specific scenarios like aircraft cabins [2]. To the authors’ knowledge the millimeter wave in-car channel has not been considered yet. In this paper we thoroughly investigate the 60 GHz in-car wideband radio channel on the basis of measurement results for a Sport Utility Vehicle (SUV) to assess the feasibility of 60 GHz high bit rate radio communication inside a car. II. CHANNEL MEASUREMENT CAMPAIGN The Head Unit (HU) is the central communication platform in a car comprising functions like radio tuner, MP3 player, navigation system, DVD drive, telephone etc. and would be the most promising component to integrate the 60 GHz wireless system as well. It is typically located behind the front panel. Therefore, the transmit antenna was mounted perpendicularly to the front panel for the measurements (see Figs. 1–3). Since various application scenarios are of interest for in-car communication, several arrangements of the receive antenna have been considered according to Figs. 1–3. The arrows and the silhouettes indicate the orientation and the pattern of the antennas, respectively. Open-ended waveguides served as antennas at both sides. Their gain of approx. 8 dBi and their pattern are quite representative for a planar antenna which would be well suited for the in-car usage case. Scenario A/B, C, D and E refer to Rear Seat Entertainment (RSE), ceiling- mounted display, front-seat passenger display and consumer electronic devices communication, respectively. It should be noted that the antennas were not supposed to be perfectly aligned. The orientation of the Tx antenna was not changed for different Rx antenna positions, and realistic losses due to misalignment and polarization mismatch arise. In the presented cases, the polarization was (more or less) vertical. There is a direct Line-of-Sight (LOS) between the Tx and the Rx antenna for Scenario A, C and D if the car is empty (no passengers are present). If the LOS is blocked by a person or an object, this is denoted as Obstructed-Line-of-Sight (OLOS) in the following. An alternative antenna configuration to Scenario A for RSE is considered by Scenario B. In this case, the Rx Fig. 1. Antenna arrangement for Scenario A, B and E – top view. 978-1-4244-2515-0/09/$25.00 ©2009 IEEE