Operation Of Future Systems Research Articles

Review of SHF and EHF slant path propagation measurements made near slough (UK)

Studies of the effects of the atmosphere on radiowave propagation relevant to the planning and operation of future satellite communication systems at frequencies above 10 GHz have been carried out at Slough for over ten years. Observational data, which relate mainly to attenuation by rain and cloud, are available within the band 11 to 110 GHz. With reference to systems performance, this paper reviews the results on atmospheric attenuation derived from single-site and space diversity experiments involving fixed-pointing radiometers, sun-tracker radiometers and test transmissions from the ATS-6, OTS and SIRIO satellites. The latter have also enabled information to be obtained on depolarisation by atmospheric constituents with particular reference to frequency reuse applications.

An exercise in the transportation of an operating system

AbstractAn attempt lo transport an operating system and some associated software from one machine to another is described. Some comments are made on the suitability of the system for such a task, and some recommendations are put forward to future operating system writers to assist in making their systems more portable.

Algorithmic generality in memory management design

As computer systems grew in complexity, the area of memory management has become increasingly important. In future operating systems what is needed is a generalized, flexible, modular, and open ended-design of the functional modules (e.g. memory management modules). To achieve these properties, sufficient ingenuity and effort are required during both design and implementation. This paper outlines an approach which should lead to a design having these properties. A memory management system was designed using this generalized approach. The system was subsequently modeled and implemented in SIMSCRIPT I.5 as a test case. The model and the successful results prove the feasibility of the approach and can be used to evaluate different memory management schemes. The functional modules within the model are general so that their mode of operation can be set from outside (this may be called parametric generality). However, the actual algorithm employed for memory management can be tailored at the site generation (or system generation) time using a convenient specification language. This design strategy is best characterized by the term "Algorithmic Generality."

4-D guidance system design with application to STOL air traffic control

A new guidance technique, referred to as 4-D guidance, is being developed to improve the operation of future STOL aircraft transportation systems. 4-D guidance refers to a technique of synthesizing a complex three-dimensional flight path from simple pilot inputs and flying the aircraft along the path according to an ATC specified time schedule. The two major elements of a 4-D guidance system are the trajectory synthesizer and the control law for flying the aircraft along the synthesized trajectory using the aircraft's autopilot and autothrottle. Inputs to the trajectory synthesizer are the three-dimensional coordinates of waypoints, the turning radius, the speed range, the acceleration limits and the arrival time at time control waypoints. First the three-dimensional trajectory is computed using circular arcs and straight lines. Then the airspeed profile, compensated for wind, is calculated to achieve the desired arrival times. The pilot is informed if the arrival times cannot be achieved. The synthesized trajectory is stored as a time sequence of reference states and controls which the aircraft is forced to track using a linear feedback law.

AFSCM 375-5 as a Methodology for System Engineering

The recently published Air Force Systems Command Manual 375-5 (AFSCM 375-5), System Engineering Management Procedures, prescribes the management policies and procedures to be followed in the establishment of requirements for, and in the design, development, test, operation, and maintenance of future Air Force systems. The life cycle of systems requiring AFSCM 375-5 implementation is described and the prescribed system engineering management process and significant documentation tools are discussed in detail. In addition, possible implementation problems and solutions associated with the application of AFSCM 375-5 are discussed.