1. UNIX (Computer operating system) 2. Real-time data processing. I. Furht, Borivoje. II. Series: Kluwer international series in engineering and computer science; SECS 121. III. Series: Kluwer international series in engineering and computer science. Real-time systems. QA76.76.063R43 1991 005.4'3-dc20
An option being considered by current and prospective mobile satellite service (MSS) operators is the use of constellations of non‐geostationary orbit (NGSO) satellites to provide global personal communications. The scarcity of free spectrum, together with the bandwidth typically required, means that any new MSS system must consider sharing spectrum with other systems and services. Spectrum sharing must be based on defined interference criteria being satisfied. When multiple NGSO satellites are considered there is no accepted method for assessing interference. This paper describes a model used as the basis for a computer simulation of interference scenarios involving MSS, fixed service (FS) and fixed satellite service (FSS) systems. The simulation includes NGSO dynamics, constellations of MSS satellites with multi‐spot antennas, multiple geostationary FSS satellites and multiple hop FS links. Interference events are based on C/I calculations, and statistics, such as the percentage of time that the C/I falls below a required protection ratio, are calculated. More generally C/I cumulative distribution functions are produced.
The UNIX® operating system, developed by AT&T Bell Laboratories, has become a standard operating system gaining rapid acceptance because of its superior flexibility, portability, and a number of support tools to increase programmer productivity. However, UNIX was originally designed for multitasking and time-sharing, and therefore conventional UNIX does not have an adequate response time and data throughput needed to support real-time applications.Many attempts have been made to adapt the UNIX kernel to provide a real-time environment. MODCOMP has developed REAL/IX operating system, which is a fully preemptive, low latency UNIX kernel. This paper discusses real-time performance of REAL/IX and compares it to MASSCOMP RTU operating system.
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