Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-11-17
2002-11-19
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S209000, C701S210000, C701S202000, C340S990000, C340S995190
Reexamination Certificate
active
06484093
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a communication route guidance system for guiding a mobile unit to a destination and, more particularly, to a communication route guidance system which enables communication between a remote information center and at least one mobile unit, both storing road data. The mobile unit is equipped with a communication terminal.
BACKGROUND OF THE INVENTION
Japanese patent laid-open publication No.10-19588 discloses an example of the prior art communication route guidance system wherein map image data, recommended route data (or optimum route data) and other data necessary in route guidance is transmitted from a remote information center to a mobile unit. In this system, the information center operates, in response to a request from the mobile unit, to read out necessary data from a database and to prepare the map image data. The remote information center also conducts a route search operation to prepare the optimum route data. The information center then transmits the map image data and the optimum route data thus prepared to the mobile unit. The mobile unit guides the user of the mobile unit to the destination in accordance with such data transmitted from the information center.
In some cases, however, the mobile unit is not capable of receiving data from the information center when the mobile unit is in an area where little or no such communication is available. Such an area is hereinafter referred to as a “non-communication” area. There will also be occasions when such communication will not be available because of problems or breakdown at the remote information center.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a novel communication route guidance system which is capable of guiding a mobile unit to a destination even when the mobile unit is unable to communicate with the information center, e.g. when the mobile unit is in a non-communication area or the system in the information center has broken down.
To achieve the above object, in accordance with a first aspect of the present invention, there is provided a communication route guidance system wherein an information center transmits route information to a mobile unit for guiding the mobile unit from its current position to a destination, in response to a request from the mobile unit, wherein the information center includes: first communication means for transmitting and receiving data to and from said mobile unit; first memory means for storing first road data; and first route search means for searching the first road date to obtain first route guidance data for guiding the mobile unit from its current position to the destination in accordance with information transmitted from the mobile unit through the first communication means and identifying the current position and a destination, responsive to a request from the mobile unit for a route search. The information center is further provided with data dividing means for dividing said first route guidance data into a plurality of data segments, each data segment being usable in said mobile unit as an independent item of route information providing guidance from a near end of a route segment (corresponding to the data segment) to the opposite, remote end of the route segment. The mobile unit, in turn, includes: second communication means for transmitting and receiving data to and from the information center; second memory means for storing second road data; second route search means for conducting a route search of the second road data to obtain second route guidance data for guiding the mobile unit from the current position to the destination; third memory means for storing at least one of the data segments transmitted from the information center through said first and second communication means; sensor means for detecting whether data is communicable with said information center through said first and second communication means; and route guidance means for guiding the mobile unit to the destination in accordance with at least one of said second route guidance data and said at least one data segment stored in the third memory means, the route guidance means guiding the mobile unit to the destination in accordance with the second route guidance data when the sensor means detects inability to communicate between the mobile unit and the information center.
As used herein, “segmental data” has reference to a series of the data segments described above.
In a preferred embodiment of the first aspect of the present invention described above, the information center further includes information collection means for obtaining the latest traffic and road information, the first road data stored in the first memory means being updated in response to the latest traffic and road information obtained by the information collection means.
In another preferred embodiment of the first aspect of the present invention, when the mobile unit has been guided by the second route guidance data obtained by the second route search means and the sensor means has detected that data communication is available with said information center, the first route search means searches for a new optimum route to obtain new route guidance data for guiding the mobile unit from its current position to the destination in response to a request from the mobile unit, the new route guidance data being divided by said data dividing means into a plurality of said data segments which are transmitted to the mobile unit for storage in the third memory means. In this embodiment, the sensor means may comprise measurement means for measuring field intensity of a radio wave in data transmission from the information center and means for judging that data can not be communicated between the mobile unit and the information center when the measured field intensity is below a predetermined threshold level. Alternatively, the sensor means may comprise means for judging that data can not be communicated when the mobile unit receives no data segment from the information center within a predetermined time period after transmitting a request to the information center. The sensor means may also comprise communication area data memory means for storing data specifying communication areas in which the mobile unit can be in communication with the information center; and means for judging, in accordance with that data stored in the communication area data memory means, that no data communication is available between the mobile unit and the information center when the mobile unit is not within any of the specified communication areas.
In accordance with a second aspect of the present invention, there is provided a communication route guidance system wherein an information center transmits route information to a mobile unit for guiding the mobile unit from its current position to a destination, in response to a request from said mobile unit, wherein the information center includes: first communication means for receiving current position and destination from the mobile unit and transmitting data segments to the mobile unit; first memory means for storing road data; route search means for searching the stored road data to obtain route guidance data for guiding the mobile unit from its current position to the destination; data dividing means for dividing the thus obtained route guidance data into a plurality of data segments, each data segment being usable in said mobile unit as an item of route information providing guidance from a near end of a route segment (corresponding to the data segment) to the opposite, remote end of the route segment; communication area data memory means for storing data specifying communication areas wherin the mobile unit can communicate with the information center through the first communication means; and transmission route length determining means for determining number of data segments in a continuous series of data segments to be transmitted to the mobile unit while travelling within one of the specified communication are
Gorai Naoki
Ito Yasuo
Kitano Satoshi
Sugawara Takashi
Yamakawa Hiroyuki
Chin Gary
Kabushikikaisha Equos Research
Lorusso & Loud
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