This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-261423 filed on Aug. 30, 2001.
1. Field of the Invention
The present invention relates to a wireless communications terminal, which receives a position measurement result that indicates a position of the wireless communications terminal from an external location information server and outputs the received position measurement result. The present invention also relates to a computer program executable by the wireless communications terminal and also to a method for outputting the position measurement result from the wireless communications terminal as positional information of the wireless communications terminal.
2. Description of Related Art
For example, some of location systems use global positioning system (GPS) satellites and/or code division multiple access (CDMA) base stations to determine a position of a wireless communications terminal, such as a cellular phone. When the cellular phone receives a command from a user to initiate a position measurement operation for determining a position of the cellular phone, the cellular phone searches the corresponding CDMA base stations and obtains CDMA base station information about the searched CDMA base stations. Then, the cellular phone transmits the CDMA base station information and a request for transmitting assist information, which is useful to the cellular phone in searching of the GPS satellites, to the location information server.
When the location information server receives the CDMA base station information and the request for transmitting the assist information from the cellular phone, the location information server determines an approximate position of the cellular phone based on the CDMA base station information received from the cellular phone. Then, the location information server computes the assist information, which is useful to the cellular phone in searching of the GPS satellites, based on the approximate position of the cellular phone. Thereafter, the location information server transmits the assist information to the cellular phone. When the cellular phone receives the assist information from the location information server, the cellular phone searches for the corresponding GPS satellites based on the assist information. Next, the cellular phone obtains GPS satellite information about the searched GPS satellites. Thereafter, the cellular phone transmits the GPS satellite information and a request for transmitting a position measurement result to the location information server.
Then, when the location information server receives the GPS satellite information and the request for transmitting the position measurement result from the cellular phone, the location information server determines the position of the cellular phone based on the GPS satellite information and/or the CDMA base station information. Thereafter, the location information server transmits a corresponding position measurement result, which indicates the determined position of the cellular phone, to the cellular phone.
In this way, the cellular phone searches the GPS satellites based on the assist information received from the location information server, so that the time required for determining the position of the cellular phone can be advantageously reduced. Furthermore, the position of the cellular phone is not determined by the cellular phone itself but is determined by the location information server, so that the work load of the cellular phone can be advantageously reduced, and the power consumption of the cellular phone can be also advantageously reduced.
However, when the cellular phone is located in an area near a window in a room, it is difficult to search GPS satellites, which are located at relatively high altitudes with respect to the cellular phone and thus have relatively large angles of elevation with respect to the cellular phone. As a result, the cellular phone can only search GPS satellites, which are located at relatively low altitudes with respect to the cellular phone and thus have relatively small angles of elevation with respect to the cellular phone. Therefore, the cellular phone only searches the GPS satellites, which are located at relatively low altitudes, and only obtains the GPS satellite information of these GPS satellites. Then, the obtained GPS satellite information is transmitted to the location information server. Consequently, the accuracy of the position measurement result is substantially, disadvantageously reduced.
Furthermore, when the cellular phone is located, for example, in a valley between tall buildings, the cellular phone receives not only direct waves (i.e., primary waves), which are directly transmitted from the CDMA base stations, but also reflected waves, which are transmitted from the CDMA base stations and are reflected, for example, by buildings. Thus, in such a case, when the cellular phone receives the reflected waves, the cellular phone obtains erroneous information about the CDMA base stations and transmits the erroneous information to the location information server. As a result, in this case too, the accuracy of the position measurement result is substantially, disadvantageously reduced. That is, the cellular phone can only provide the position measurement result having the relatively low accuracy, and the convenience of the cellular phone is impaired accordingly.
The present invention addresses the above disadvantage. Thus, it is an objective of the present invention to provide a wireless communications terminal, which is capable of providing a more appropriate position measurement result. It is another objective of the present invention to provide a computer program executable by such a wireless communications terminal to provide a more appropriate position measurement result. It is a further objective of the present invention to provide a method for outputting a more appropriate position measurement result from such a wireless communications terminal.
To achieve the objectives of the present invention, there is provided a wireless communications terminal including a plurality of searching means, each for searching at least one corresponding external signal source, which outputs a signal usable in determining a position of the wireless communications terminal, and for outputting search information about the at least one corresponding external signal source, which is obtained through the searching of the at least one corresponding external signal source. The plurality of searching means includes a first searching means for searching at least one GPS satellite as the at least one corresponding external signal source and a second searching means for searching at least one base station as the at least one corresponding external signal source. The wireless communications terminal further includes a wireless telephone transceiver means for performing wireless telephone communication with a corresponding one of the at least one base station, an outputting means for outputting positional information of the wireless communications system, and a control means for controlling the plurality of searching means, the wireless telephone transceiver means and the outputting means. The control means receives each search information from each searching means and transmits each search information to an external location information server through the wireless telephone transceiver means. The external location information server is capable of generating a plurality of position measurement results, each of which indicates the position of the wireless communications terminal, based on the search information of at least one of the plurality of searching means and is also capable of transmitting each of the position measurement results. The control means receives a first one of the position measurement results, which is transmitted from the external location information server, through the wireless telephone transceiver means and determines whether a predetermined condition is satisfied. When the control means determines that the predetermined condition is satisfied, the control means receives a second one of the position measurement results, which is transmitted from the external location information server, through the wireless telephone transceiver means and outputs the second one of the position measurement results to the outputting means, so that the outputting means outputs the second one of the position measurement results as the positional information of the wireless communications terminal.
To achieve the objectives of the present invention, there is also provided a computer program executable by the wireless communications terminal and a method for outputting positional information from the wireless communications terminal. First, in the wireless communications terminal, search information is received from each of a plurality of searching means, each for searching at least one corresponding external signal source, which outputs a signal usable in determining a position of the wireless communications terminal, and for outputting the search information about the at least one corresponding external signal source, which is obtained through the searching of the at least one corresponding external signal source. The plurality of searching means includes a first searching means for searching at least one GPS satellite as the at least one corresponding external signal source and a second searching means for searching at least one base station as the at least one corresponding external signal source. Then, the search information of each of the plurality of searching means is transmitted to an external location information server through a wireless telephone transceiver means for performing wireless telephone communication with a corresponding one of the at least one base station. Thereafter, a first one of a plurality of position measurement results, each of which indicates the position of the wireless communications terminal, is received from the external location information server through the wireless telephone transceiver means. The position measurement results are generated by the external location information server based on the search information of at least one of the plurality of searching means. Then, it is determined whether a predetermined condition is satisfied. Next, a second one of the position measurement results is received from the external location information server through the wireless telephone transceiver means when it is determined that the predetermined condition is satisfied. Then, the second one of the position measurement results is inputted to an outputting means for outputting positional information of the wireless communications system, so that the outputting means outputs the second one of the position measurement results as the positional information of the wireless communications terminal.