Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-02-18
2001-09-04
Hunter, Daniel (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S067150
Reexamination Certificate
active
06285885
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a radio communication apparatus having a unit for measuring the distance between two stations. This invention particularly relates to a mobile radio communication apparatus having a unit for measuring the distance between a mobile station and a base station. This invention also relates to a mobile radio communication apparatus having a unit for detecting the timing of the reception of a reference signal transmitted from a base station.
2. Description of the Related Art
Japanese published unexamined patent application 7-38951 discloses a method of detecting the position of a portable station (a mobile station) relative to the positions of base stations. According to the method in Japanese application 7-38951, a position detection inquiry signal is transmitted from one of the base stations to a portable station at a predetermined time period. The portable station sends a position detection answer signal when receiving the position detection inquiry signal. The position detection answer signal contains identification information related to the portable station. The position detection answer signal is received by at least three base stations close to the portable station. In each of the three base stations, the electric field strength of the received position detection answer signal is measured, and the distance between the portable station and the base station is calculated on the basis of the measured electric field strength. The position of the portable station relative to the positions of the base stations is estimated from the calculated distances between the portable station and the three base stations.
In Japanese application 7-38951, the distance between the portable station and the base station is calculated on the basis of the electric field strength of the portable-station signal received at the base station. Since the electric field strength of the portable-station signal received at the base station depends on not only the distance between the portable station and the base station but also other factors. Generally, some of the other factors significantly affect the electric field strength of the received signal. Accordingly, in Japanese application 7-38951, the calculated distance between the portable station and the base station tends to be inaccurate in certain conditions.
Japanese published unexamined patent application 8-179028 relates to detection of the present position of a mobile station in a cellular telephone network. In Japanese application 8-179028, a mobile station has a function of measuring the levels of received radio signals transmitted from at least three adjacent base stations including a traffic base station. When the mobile station requests information of its present position, the traffic base station instructs the mobile station to report the measured signal levels. The traffic base station calculates the losses of propagation of radio wave between the mobile station and the base stations on the basis of the measured signal levels reported by the mobile station. Then, the traffic base station calculates the distances between the mobile station and the base stations on the basis of the calculated propagation losses. The present position of the mobile station is estimated from the calculated distances between the mobile station and the base stations.
In Japanese application 8-179028, the distance between the mobile station and the base station is calculated on the basis of the level of the base-station signal received at the mobile station. The level of the base-station signal received at the mobile station depends on not only the distance between the mobile station and the base station but also other factors. Generally, some of the other factors significantly affect the level of the received signal. Accordingly, in Japanese application 8-179028, the calculated distance between the mobile station and the base station tends to be inaccurate in certain conditions.
SUMMARY OF THE INVENTION
It is a first object of this invention to provide a radio communication apparatus having an improved unit for measuring the distance between two stations.
It is a second object of this invention to provide a mobile radio communication apparatus having an improved unit for measuring the distance between a mobile station and a base station.
It is a third object of this invention to provide an improved mobile radio communication apparatus having a unit for detecting the timing of the reception of a reference signal transmitted from a base station.
A first aspect of this invention provides a radio communication apparatus comprising first means for receiving a radio-frequency signal; second means for converting the radio-frequency signal received by the first means into a corresponding baseband signal; a memory storing a predetermined pseudo-noise code signal; third means for calculating a correlation between the baseband signal generated by the second means and the predetermined pseudo-noise code signal stored in the memory; and fourth means for detecting a timing at which the correlation calculated by the third means peaks substantially.
A second aspect of this invention is based on the first aspect thereof, and provides a radio communication apparatus wherein the fourth means comprises first sub-means for differentiating the calculated correlation into a differentiation result; second sub-means for deciding whether or not the differentiation result generated by the first sub-means becomes smaller than a predetermined reference value; and third sub-means for using a timing at which the second sub-means decides that the differentiation result becomes smaller than the predetermined reference value as the timing at which the calculated correlation peaks substantially.
A third aspect of this invention provides a radio communication apparatus in a first station which can communicate with a second station by radio, the second station having a function of repeating a received radio signal, the apparatus comprising first means for transmitting a first radio-frequency signal containing a predetermined pseudo-noise code signal toward the second station; second means for detecting a first timing at which the first means transmits the first radio-frequency signal; third means for receiving a second radio-frequency signal after the first means transmits the first radio-frequency signal; fourth means for converting the second radio-frequency signal received by the third means into a baseband signal; a memory storing the predetermined pseudo-noise code signal; fifth means for calculating a correlation between the baseband signal generated by the fourth means and the predetermined pseudo-noise code signal stored in the memory; sixth means for detecting a second timing at which the correlation calculated by the fifth means peaks substantially; seventh means for calculating a time interval between the first timing detected by the second means and the second timing detected by the sixth means; and eighth means for calculating a distance between the first station and the second station on the basis of the time interval calculated by the seventh means.
A fourth aspect of this invention is based on the third aspect thereof, and provides a radio communication apparatus wherein the sixth means comprises first sub-means for differentiating the calculated correlation into a differentiation result; second sub-means for deciding whether or not the differentiation result generated by the first sub-means becomes smaller than a predetermined reference value; and third sub-means for using a timing at which the second sub-means decides that the differentiation result becomes smaller than the predetermined reference value as the second timing at which the calculated correlation peaks substantially.
REFERENCES:
patent: 4169245 (1979-09-01), Crom
patent: 5293642 (1994-03-01), Lo
patent: 5327144 (1994-07-01), Stilp
patent: 5381445 (1995-01-01), Hershey
patent: 5548583 (1996-08-01), Bustamante
patent: 5600706 (1997
Connolly Bove Lodge & Hutz
Corsaro Nick
Hunter Daniel
Matsushita Electric - Industrial Co., Ltd.
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