Data processing: measuring – calibrating – or testing – Testing system – Signal generation or waveform shaping
Reexamination Certificate
2002-02-07
2004-05-11
Bui, Bryan (Department: 2863)
Data processing: measuring, calibrating, or testing
Testing system
Signal generation or waveform shaping
C455S166200
Reexamination Certificate
active
06735544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system and method for predicting radio wave propagation characteristics, and in particular to a system for predicting the radio wave propagation characteristics by a technique of geometrical optics employing a so-called ray launching processing.
2. Description of the Related Art
A radio wave propagation simulator is employed to assist an arrangement of a base station or a host system in a radio communications system. The received power or delay spreading at any receiving point is assessed by using the radio wave propagation simulator to determine an suitable installation site of a transmitting station, so that the overall efficiency can be enhanced by reducing the number of base stations to be arranged.
The radio wave propagation simulation is largely classified into a statistical technique and a deterministic technique. The statistical technique gives an expression for estimating the propagation loss with the arguments of distance and frequency to determine the parameters on the basis of a large amount of data resulted from actual measurements of the propagation loss in accordance with the multivariate analysis at the time of determining parameters of the expression. On the other hand, the latter deterministic technique is one in which, considering that the radio wave radiated from an antenna is a collection of a number of radio wave rays, each ray is reflected and transmitted repeatedly on the geometrical optics, and propagated, and the rays incoming to an observation point is synthesized to obtain the propagation loss and the amount of delay.
This technique of geometrical optics is further classified into an imaging technique and a ray launching technique. The imaging technique determines a reflection and transmission path of the ray connecting between the transmitting and receiving points by obtaining an imaging point against the reflection surface. Since the reflection and transmission path is uniquely determined if the transmitting and receiving points and the reflecting and transmitting objects are defined, the imaging technique is one of searching for a strict propagation route of the ray. On the other hand, the ray launching technique is one in which the rays from an antenna are radiated to predetermined directions, irrespective of the receiving point, and the ray passing near the receiving point through the repeated reflection and transmission is regarded as the ray incoming to the receiving point. This was described in Japanese Patent Laid-Open No. 9-33584 specification, for example.
The ray launching technique solves approximately, but not strictly like the imaging technique, the propagation route of the ray connecting between the transmitting and receiving points, and has a feature of shortening the time needed to search for the propagation route.
FIG. 13
is a view for explaining the operation of the ray launching technique in the case where an observation area
020
, a transmitting point
009
, a receiving point
010
, and two contents
001
and
002
within the observation area are provided. In
FIG. 13
, for the simplicity, the operation is explained only in the two dimensional plane, but practically, the operation may be performed in the three dimensional space.
First of all, a ray is radiated from the transmitting point
009
in a direction toward the propagation route
003
. With regard to all the contents within the observation area, it is determined whether or not the ray radiated in that direction strikes the contents existing within the observation area. The ray strikes a content
001
at a reflection point
012
to generate a transmitted ray
011
and a reflected ray
004
. The ray
004
produced by reflection further strikes a content
002
to generate a transmitted ray
013
and a reflected ray
008
in similar manner. The reflected ray
008
, which passes in the vicinity of the receiving point
010
, is regarded as the incoming wave in the observation point.
Specifically, the propagation routes
003
,
004
and
008
, the receiving strength as defined from a total of propagation distances and the incoming delay time are recorded in FIG.
14
. In
FIG. 14
, the transverse axis
101
represents the delay time required for the ray to arrive from the transmitting point
009
via the routes
003
,
004
and
008
to the observation point
010
, and the longitudinal axis
102
represents the received electric-field strength of the ray passing through the route.
The ray from the transmitting point
009
in the direction toward the propagation route
003
has the transmitted rays
011
and
013
, for which the transmission and reflection are repeatedly searched, as in the propagation routes
003
,
004
and
008
, wherein the ray passing in the vicinity of the receiving point
010
is treated as the incoming wave, as in the propagation route
008
, and the above processing is continued till the search end condition is met. The search end condition is that the received field strength at the reflection and transmission point falls below a predetermined value. In this invention, the above process is called the ray launching processing.
After the ray radiated from the transmitting point
009
in the direction toward the propagation route
003
is searched for the reflection and transmission, the same ray launching processing is made by changing the radiation angle of the ray radiated from the transmitting point
009
, as in a route
006
, for example, and investigating all the radiation directions from the transmitting point
009
, or partial radiation directions as defined beforehand. Lastly,
FIG. 15
which shows a delay profile for the receiving point
010
is obtained. In
FIG. 15
, the transverse axis
201
represents the delay time when the ray comes in from the transmitting point
009
, and the longitudinal axis
202
represents the received electric-field strength of the ray passing through the route. The received power at the receiving point
010
is given by a total of received strength for all the paths as indicated in
FIG. 15
, and the delay spreading for indicating degrees of the distortion is given by the standard deviation of the delay time.
The ray launching technique that gives a solution of the propagation route of the ray connecting the transmitting and receiving points approximately, but not strictly as by the imaging technique, takes a shorter time for searching the propagation route than the imaging method. However, it still takes a lot of time in the case where there is a large building or there are a very great number of fixtures (e.g., contents
001
and
002
in
FIG. 13
) installed within the building.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system and method for predicting the radio wave propagation characteristics in which the ray launching technique is performed at higher speed, employing a parallel computer, and a recording medium for recording a program for use with the method.
According to the present invention, there is provided a system for predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the system comprising a plurality of CPUs (Central Processing Units) that are interconnected via a network, wherein the plural rays radiated from the transmitting point are divided into a plurality of groups, each group being allocated to a different CPU, an
Furukawa Hiroshi
Watanabe Yoshinori
Bui Bryan
NEC Corporation
Young & Thompson
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