A deterministic Indoor Propagation Prediction Technique , using Ray tracing and Field Measurements at 60 GHz

Wireless and mobile broadband communication systems are planned to operate at the mm-wave band, due to the spectrum availability and wider bandwidth requirements. Especially the frequency of 60 GHz is a strong candidate. In this paper the propagation characteristics at 60 GHz, in a specific indoor environment are examined. A ray tracing method has been applied and its accuracy has been tested by comparison with actual measurements. Moreover the impact of the model parameters (e.g. wall material characteristics, antenna radiation patterns) on the predicted results has also been investigated. I.INTRODUCTION Mobile and wireless broadband communications is one of the most challenging fields of current research in telecommunication engineering. The goal is to extend to mobile users, access to broadband/multimedia services which exist, or will exist in the near future, for the fixed users. Wireless LAN’s (WLAN’s) and Mobile Broadband System (MBS) seem to be the first applications with this orientation. WLAN’s are directed to communications between computers. High-Performance Radio LAN (HIPERLAN) and IEEE 802.11 are two candidates. In addition to the mobility that becomes possible with WLAN’s, these systems can also been used in environments where cable installation is impractical. The Mobile Broadband System, on the other hand is intended to be a cellular system providing compatibility with the terrestrial BISDN. The services provided by those systems, require increased data rates (2 Mb/s-155 Mb/s) and wide bandwidths which are only available at very high frequency bands, e.g. in the range of millimeter-waves around 60 GHz. [1],[2]. Propagation characteristics at 60 GHz are very different from the ones at lower frequencies. At this band is the peak of oxygen absorption (15 dB/Km), while water vapour absorption is considerable as well. Experimental results also prove that at high frequencies propagation is taking place mostly through direct and reflected paths and diffraction becomes negligible. Millimeterwave radio channel suffers from multipath effects, which are the primary reason of frequency selective fading. To study these effects and to model the propagation characteristics, a series of investigations and measurements are being carried out [3],[4]. Knowledge of channel parameters is a crucial factor for designing efficiently a wireless network. Especially for the mm-wave band, which has recently started being investigated, it is important to extract results for different conditions (indoors, outdoors and several environments). This can be done by conducting measurements and/or by using prediction techniques to determine the interesting parameters. Depending on the channel characteristics under investigation, there is a choice for measuring and predicting procedures. Measurements can be done in time or frequency domain. For predicting one can choose between statistical or deterministic models. In this paper we present a ray tracing (deterministic) method for predicting the received power and the delay spread for indoor scenarios. This method is then applied to a specific environment, where frequency domain measurements have already been conducted. Results for both measured and predicted data are presented in parallel and compared. The way that several factors (material characteristics, antenna patterns, etc) affect the propagation has also been examined by changing the initial values of the problem. II. CHANNEL MODEL In an indoor environment, high frequency electromagnetic waves follow discrete paths, yielding a multipath channel for a radio link. The complex baseband impulse response h(t) of a multipath channel resulting from discrete rays can be modeled as: ( ) h t b e t n j n n n N