Measurement of Coherence Bandwidth in UHF Radio Channels for Narrowband Networks

This paper presents results of investigation on the coherence bandwidth of narrowband radio channels in 430 MHz band. The coherence bandwidth values were estimated from a power delay profile obtained by recording CDMA2000 forward channel signals during real-field measurements in various environments: medium city, flat terrain, and hilly terrain in northern Poland. The results of measurements are compared with characteristic parameters of UHF radio channel models defined for exemplary narrowband digital system from the TETRA standard. In all of the tested environments, the coherence bandwidth values during most of an observation time were much higher than 25 kHz. Therefore, the fading in tested UHF narrowband channels should be classified as flat fading

TDOA versus ATDOA for wide area multilateration system

Abstract This paper outlines a new method of a location service (LCS) in the asynchronous wireless networks (AWNs) where the nodes (base stations) operate asynchronously in relation to one another. This method, called asynchronous time difference of arrival (ATDOA), enables the calculation of the position of the mobile object (MO) through the measurements taken by a set of non-synchronized fixed nodes and is based on the measurement of the virtual distance difference between the reference nodes and the several MO positions (more than two), as well as on the solution of a nonlinear system of equations. The novelty of the proposed solution is using the measurements taken by at least five ground sensors without time synchronization between them to estimate the position of the tracked MO transmitting four or more sounding signals in random time. The new method significantly simplifies the localization process in real-life AWNs. It can be used on its own or to complement the traditional synchronous method. The paper focuses on the description of the proposed ATDOA method, two algorithms TS-LS (Taylor series least-squares) and GA (genetic algorithm) for solving the nonlinear system of equations, example application of the new method for a three-dimensional space, and presentation of the simulation models and simulation results. An important part of the paper is the comparison of the efficiency between the asynchronous method and the synchronous one for wide area multilateration (WAM) system. In addition, the Cramér-Rao lower bound (CRLB) is derived for this problem as a benchmark. The preliminary measurement results obtained by applying the proposed ATDOA method against the background of the synchronous one are presented at the end of the paper. As it could be expected, the synchronous solution gives better results. The synchronous method allows to locate the aircraft within 15 m in about 80% of the time, while the ATDOA method in 74% of the time for the base stations clocked from the reference clocks with the stability equal to 10−9, and in 58% of the time for the base stations clocked from the reference clocks with the stability equal to 10−8. The new method therefore should not be treated as the improvement of the existing synchronous positioning systems but as a backup solution which allows to keep the LCS systems running even during ground stations synchronization failure

Introduction Studies of Plasma-Focus discharges within the PF-360 facility equipped with needle D 2 O-ice target

Numerous PF experiments, which were performed in many laboratories all over the world showed a promising scaling of the neutron yield (Y n ) from D-D fusion reactions. Some investigations extended this scaling to a multi-MJ and multi-MA level Experimental set-up Recent studies within the PF-360 facility have been carried out by using larger coaxial electrodes of 120 mm and 170 mm in diameter, respectively. Both electrodes were 300 mm in length, and the main ceramic insulator, embracing the basis of the inner electrode, was 80 mm in length. The main experimental chamber of the PF-360 facility was filled with pure deuterium under the initial pressure, which was varied from 5.1 mbar to 12.0 mbar. PF discharges were powered from a capacitor bank of 288 µF. Abstract The paper describes a new technique which has been investigated in order to overcome the neutron saturation effect and to increase the neutron yield from the plasma-focus (PF) discharge

M (2000) Studies of Plasma-Focus discharges within the PF-360 facility equipped with a planar D2O-ice target. Nukleonika 46;S1:65–68 37Results of large scale Plasma-Focus experiments and prospects for neutron yield optimization

Introduction Many Plasma-Focus (PF) experiments, which were performed in different laboratories, showed an optimistic scaling of the neutron emission. These scaling laws for the fusion neutron yield (Y n ) from the Plasma-Focus facilities are described by the simple formulae: where W 0 is the initial energy input, I max is the maximum value of the main discharge current, α = 2.0-2.2 as well as β = 3.3-4.4 depend on a machine type and input energy value. For the PF-360 facility There were some papers, which suggested that it is possible to extend this scaling to a higher discharge current and initial energy values [1], but there is no experimental verification of this hypothesis so far. On the contrary, it was found that the promising scaling laws are valid only up to some critical levels, at which the neutron yield saturates (or even decreases) The PF-360 machine was built during the turn of the 70s and 80

Position Estimation in Corridors Along the Coupled Mode of Radiating Cables

Radiating cables are mostly used to provide radio communication in tunnels or corridors, but they can also be used to estimate the position of a mobile terminal along the cable. In this paper, a measuring receiver’s position was estimated by measuring the difference in the direct signal’s reception time, which was generated by a transmitter connected to one end of the radiating cable, and the delayed signal retransmitted from another end. During tests, a relatively narrowband (23 MHz) signal was used in the unlicensed band (2.4 GHz) and 50 m long coupled mode radiating cable. The cable was installed along a corridor in the office building. Measurement results used different equipment configurations (i.e., return signal only amplified or amplified and frequency-shifted), which presented possible sources of errors