6. M.C. Jeruchim, P. Balaban, and K.S. Shanmugan, Simulation of communication systems, Plenum, New York, 1992. 7. K. Kalliola, H. Laitinen, K. Sulonen, L. Vuokko, and P. Vainikainen, Directional radio channel measurements at mobile station in different radio environments at 2.15 GHz, Proc 4th European Personal Mobile Commun Conf, Vienna, Austria, Feb. Ž . 2001, CD-ROM ISBN 3-85133-023-4 , paper pap16.pdf.  2002 John Wiley & Sons, Inc. INSIDE – OUTSIDE LIFT POWER-LEVEL STATISTICS AT UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM ( ) UMTS FREQUENCY Ana Vazquez Alejos, 1 Inigo Cuinas, 1 and ´ ˜ ˜ Manuel Garcıa Sanchez 1 ´ ´ 1 Departamento de Teorıa do Sinal e Comunicacions ´ ´ E.T.S.E. Telecomunicacion ´ Universidade de Vigo 36200 Vigo, Spain Recei  ed 23 July 2001 ABSTRACT: The use of mobile phones is being extended e erywhere. Typical studies of indoor and outdoor propagation ha e to be impro  ed with information related to specific places, like tunnels, basements, or lifts. In this paper, the  ariations in the power le el within lift cabins, due to  ertical mo ement and opening doors, are analyzed. Measurements ha e been made, and a statistic e aluation of these effects are presented. Results show that  ariations in power le el are  ery strong during the mo ement of the cabin. Moreo  er, the effect of the mechanisms that open and close the doors is clearly highlighted in the measurements, where fast  ariations can be obser  ed in the power le el, e en in static locations of the cabin. The presented results can be applied in network planning in places where mobile communications are often used in lifts, such as business buildings.  2002 John Wiley & Sons, Inc. Mi- crowave Opt Technol Lett 32: 122124, 2002. Key words: radio-channel measurement; indoor propagation; UMTS; lifts DOI 10.1002  mop.10108 INTRODUCTION Personal communication systems, such as cellular mobile phones, have been popularized all around the world. Facts that, so far, were not unusual, and even impolite, like main- taining a phone call on the street or in a coffee shop, are now accepted as habitual situations. Currently, the dependence on the mobile phone has been extended to most of the popula- tion. Thus, places where the use of cellular terminals was unexpected are becoming more and more important in the study of propagation mechanisms and effects: tunnels in highways and underground, large shopping centers, and lifts. The establishment and maintenance of communication via a mobile phone from a lift involves an interesting propaga- tion problem: the cabin is like a metal box, which provides a  high degree of isolation 1 . This strong attenuation is re- flected in deep fading bursts. Further, the electronic and mechanical devices conforming the lift introduce noise of different kinds: thermal, impulsive, etc. In order to investigate the effects caused by the movement of a lift on the radio-channel power level of a radio link established from inside the cabin to the outside, a measure- Contract grant sponsor: Spanish CICYT Contract grant number: Project TIC 1999-1067-C02-02 Figure 1 Transmission system ment campaign has been carried out. The selected frequency for this research was 2 GHz, which is the band assigned to   UMTS systems 2  3 . The results obtained and their interpre- tation are the contents of this paper. MEASUREMENT HARDWARE The measurement system was a radio-channel sounder, con- sisting of a continuous-wave transmitter and an independent receiver based on a spectrum analyzer. The 2 GHz transmitter consists of a 14 dBm phase-locked oscillator, the output of which was fed to an omnidirectional vertically polarized antenna via a 15 dB gain amplifier. The configuration of this transmitting section is depicted in Fig- ure 1. The receiver uses a similar antenna, and is made of an HP-8594-E spectrum analyzer, the collected data of which are sent to a computer by means of the series port. The data acquisition is controlled by custom software written in Lab- View, which was programmed to obtain a sample per second. MEASUREMENT GEOMETRY The lift used for the campaign is a metallic one installed in the School of Telecommunications at the University of Vigo. A scheme of this four-floor elevator is depicted in Figure 2. The height of each floor is about 3 m, and metallic stairs are located near the lift conduct. The transmitter was placed inside the cabin, where a battery provided energy to the system. The receiver was located on the top floor, near the automatic lift doors. During the measurement campaign, the lift was forced to move from the top to the bottom and vice versa, while the receiver was collecting data. Samples were obtained each second during an hour of continuous movement of the cabin up and down. The obtained series can be divided into four . groups: 1 when the lift is at the same floor of the receiver Ž . . fourth floor , and the doors are open; 2 the lift goes down; . Ž . 3 the cabin stops at the bottom first floor , and the doors . open; and 4 the lift goes up. Figure 2 Scheme of the four-floor lift MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 32, No. 2, January 20 2002 122