<p> AMCP WG-C/2 WP/16</p><p>AERONAUTICAL MOBILE COMMUNICATIONS PANEL (AMCP) WORKING GROUP C Second Meeting Noordwijk,The Netherlands 7-11 May 2001</p><p>Agenda Item , </p><p>Availability for AMS(R)S</p><p>Prepared by Shigeki Masuda, JCAB</p><p>SUMMARY This paper propose the necessity of a discussion regarding the availability of AMSS 1 used for AMS(R)S .</p><p>S</p><p>INTRODUCTION 1.1 On the process of the development of the current AMSS SARPs, AMSS WG-A discussed the reliability and availability of the each segment of AMSS such as satellite, AES and GES. However, the current AMSS SARPs does not appear to specify the availability of AMSS. On the other hand, RCP, RNP and RSP are under discussion in the ICAO Panels to define the requirements of the performance respectively.</p><p>1.2 CPDLC and ADS operations by AMSS have been introduced into several routes in the oceanic air space. JCAB has been conducting ADS trial in the North Pacific Route between Japan and the United States of America since 1997.</p><p>2. DISCUSSION 2.1 JCAB considers the required availability of AMSS by studying the case of satellite failure on the assumption that most of the airplanes rely on AMSS, which will make it possible to reduce the separation minima in the foreseeable future.</p><p>2.2 HF communication could be used as a back up for AMSS, however it will be impossible for HF communication to manage a lot of aircraft in the case of malfunction of the satellite. In addition to this limitation, Air Traffic Controller shall change the longitudinal separation minima from ADS/ CPDLC-based separation to time based separation, since ADS/CPDLC- based longitudinal separation requires the high level of communications performance accomplished only by AMSS. </p><p>2.3 If malfunction of the satellite occurs, it is considered that all the airplanes using the satellite will be forced to log-off and rush to send log-on messages at the same time to the other satellites available. For instances, it would occur from AOR-W to AOR-E or from POR to MTSAT.</p><p>2.4 ENRI (Electronic Navigation Research Institute) has conducted a study for simulating the failure of a satellite and estimated the time required for log-on to another satellite. The study will be provided to this meeting by a separate paper.</p><p>3. PROPOSAL 3.1 The meeting is invited to a) note the information in this paper. b) consider the necessity for establishing measures that will ensure a high level of availability of the AMSS. c) consider the necessity of discussions for the availability issue to provide appropriate information to define the RCP discussed in OPLINKP. </p>