Showing papers by "Theodore S. Rappaport published in 1988"

Infra-red location system for navigation of autonomous vehicles

Abstract: A beacon method for locating autonomous vehicles in a flexible manufacturing environment is presented, and typical positioning errors of such a method are computed. Data obtained from an experimental beacon navigation system support the analytical results which indicate excellent positioning accuracy is possible over a large workspace, and that unlike dead reckoning systems, navigation errors are dependent solely upon the vehicle's position in the workspace and not the distance traveled. >

Tunable discone antenna

Abstract: A discone antenna has a conducting cone having an apex and a conducting disc with a disc feed conductor extending from its center. The conducting disc is mounted at the apex of the cone in spaced relation therewith such that the disc feed conductor extends down into the cone through the cone's apex. A coaxial connector is mounted within the cone at the apex of the cone and defines a tuning cavity therein. A tuning slug is received in the tuning cavity through the apex of the cone and is vertically adjustable within the tuning cavity to tune the antenna.

Uhf multipati-i and propagation measurements in manufacturing environments

Abstract: Wide band multipath measurements at 1300 MHz have been made in five factories in Indiana. The rms delay spread (a) values were found to range between 30 ns and 300 ns. Median a values were 96 ns for line-of-sight (LOS) paths along aisleways and 105 ns for obstructed paths across aisles. Delay spread values were not correlated with transmitter-receiver (T-R) separation, but were dependent upon factory inventory, building construction materials, and factory topography.

Delay spread and time delay jitter for the UHF factory multipath channel

Abstract: The results of wideband delay spread and time-delay jitter measurements collected from five factory buildings are presented. Carrier frequency was 1282 MHz. The data show that excess mean delay, RMS delay spread, and time-delay jitter values in single-storey factory buildings are similar to values observed in and around multistorey office buildings. Differential time-delay jitter measurements reveal that the excess mean delay can vary by as much as 180 ns for 5.5-cm shifts in receiver location. Results from 950 multipath power delay profiles collected in 50 local areas are summarized. >

Autonomous roving vehicle navigation, control and communication

Abstract: As part of an ongoing project to develop an Intelligent Factory Transport System based on small, inexpensive, fast moving, autonomous vehicles, a number of theoretical and experimental investigations have been carried out to determine the most effective methods for navigating, controlling, and communicating with them in a factory environment. AGVs operating without a physical guidepath require a navigation system capable of maintaining vehicle postion control over extended time and spatial intervals. The navigation and control system that has evolved obtains vehicle position and heading by integrating incremental path changes as determined from shaft encoders on the rear wheels of the vehicle. These quantities are maintained in a global coordinate system containing all possible vehicle paths. An error analysis of the dead reckoning performance indicates . the necessity for supplemenary external inputs and also suggests a straight forward method of calibrating the system in which the error sources are essentially uncoupled. The primary variable used to control position is the crosstrack error of the front wheel relative to the desired path with heading error used during turns. These local coordinates are computed by an appropriate transformation of the global coordinates maintained in the navigation system. Simulations and experiments showed that controlling the crosstrack error of the front wheel relative to the desired path gave a simpler and more stable system than control of the position of the rear wheels .. It was found that, with proper design, excellent performance can be achieved. Because sufficient data was not available to properly characterize the indoor factory radio channel, extensive measurements were made · at five different industrial sites .. It was found that fading characteristics arc strongly dependent on the topography of the work place. Shadowing and large scale loss models have been developed that nrc suitable for use in design of narrowband radio links. Widcband measurements revealed that because of the serious multipath present in· the indoor· factory environment, high data rates arc not possible with conventional modulation systems and new, robust techniques must be developed to meet such needs. -I

UHF multipath and propagation

Abstract: Wideband multipath measurements at 1300 MHz have been made in five factories in Indiana. The RMS delay spread ( sigma ) values were found to range between 30 ns and 300 ns. Median sigma values were 96 ns for line-of-sight (LOS) paths along aisleways and 105 ns for obstructed paths across aisles. Delay spread values were not correlated with transmitter-receiver (T-R) separation, but were dependent on factory inventory, building construction materials, and factory topography. It is noted that such measurements are important for the development of wireless factory communication systems which are envisaged to provide high data rate links between mobile robots, automated machinery, personnel, and remote terminals in the factory of the future. >