Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-04-06
2004-04-13
Chin, Vivian (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S437000, C455S442000, C455S439000, C455S513000, C455S450000, C370S330000, C370S331000, C370S333000
Reexamination Certificate
active
06721564
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-100231, filed Apr. 7, 1999; and No. 2000-069689, filed Mar. 14, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a mobile communication terminal apparatus, a hand-over control device, a hand-over controlling method and a storage medium storing the hand-over controlling method, which are used in a cellular mobile communication system, and more particularly to a mobile communication terminal apparatus having a function of detecting the quality degradation of a radio channel and requesting a base station to operate the hand-over, a hand-over control device, a hand-over controlling method and a storage medium storing the hand-over controlling method.
Recently, a cellular mobile communication system whose typical is a portable telephone system, has been rapidly spread. The cellular mobile communication system distributes a plurality of base stations in a service area and forms a radio zone called a cell by these base stations. Then, the system connects a mobile communication terminal apparatus to the base stations of the radio zone where the terminal apparatus exists via a radio channel and further connects this base station to a terminal apparatus of a communication partner via a public network or the like, and thereby implements the communication between the terminals.
Incidentally, when the mobile terminal apparatus moves from a radio zone where it currently exists to another radio zone during the standby time or communication time, changing the base station in the established synchronization to the base station of the moving destination or what is called hand-over occurs in this type of the system. The hand-over operations will be explained below by exemplifying a system adopting the CDMA (Code Division Multiple Access) system.
That is, the CDMA mobile communication terminal apparatus measures the receipt level of a pilot signal transmitted by the base station in the established synchronization and also measures each of receipt levels of pilot signals transmitted by respective neighboring base stations, during the standby time or communication time. As for the strength of the receipt level, a ratio (Ec/Io) of the energy (Ec) of the despread pilot signal from the base station which is to be measured to the total receipt energies (Io) of the despread pilot signals may be used. When the receipt level from a neighboring base station is equal to or higher than a predetermined level in terms of the strength, or when the ratio of the receipt level from the base station which is in the established synchronization to the receipt level from the neighboring base station exceeds a predetermined value, the apparatus generates a message for requesting the hand-over and transmits it to the base station in the established synchronization. At this time, the measurement value of the receipt level from the base station in the established synchronization and the measurement values of the receipt levels from the neighboring base stations, are inserted into the message for requesting the hand-over.
When the base station receives the message for requesting the hand-over from the mobile communication terminal apparatus, a base station at the hand-over destination is determined on the basis of the measurement values of the receipt levels from the base stations that are inserted into the message, and this determined hand-over destination is noticed to the mobile communication terminal apparatus that has requested the hand-over. When the mobile communication terminal apparatus receives this notice, the apparatus makes a response to the base station and then changes the base station in the established synchronization on the basis of the notice. Thus, the hand-over of the mobile communication terminal apparatus is executed.
However, this kind of the conventional system has the following problem that should be solved. When the mobile communication terminal apparatus transmits the message for requesting the hand-over, the apparatus waits for a response message representing the acknowledgement that is to be sent back from the base station. If the response message representing the acknowledgement has not been sent back within a certain time, the apparatus assumes that the quality of the radio channel is temporarily degraded, and then repeats the transmission of the message for requesting the hand-over in a predetermined access sequence at the times designated by the base station.
However, if the measurement value of the receipt level is not noticed to the base station by the repeated transmissions, the noticed measurement value of the receipt level is often different from an actual measurement value at the current time. Particularly, if the mobile communication terminal apparatus moves at a high speed, the difference between the noticed measurement value and the actual value becomes larger since a point where he receipt levels from the respective base stations are measured largely changes to the position of the mobile communication terminal apparatus at the time when the hand-over requesting message actually reaches the base station. In such a case, the base station determines the hand-over destination on the basis of the previous measurement value that is different from the actual one and, therefore, the hand-over may not be properly executed.
BRIEF SUMMARY OF THE INVENTION
The present invention is accomplished in consideration of the above circumstances, and its object is to provide a mobile communication terminal apparatus capable of allowing the hand-over to be executed to an optimum base station at any time even when the request for the hand-over is noticed by the repeated transmissions of the message, and thereby keeping the stable communication.
In according to one aspect of the present invention, there is provided a mobile communication terminal apparatus having a function of detecting degradation of receiving quality thereof and transmitting a request for hand-over to a base station in a state of being in the established synchronization with any one of a plurality of base stations. The mobile communication terminal apparatus is characterized by comprising: hand-over determination means for measuring receiving qualities of radio signals transmitted by the base station in the established synchronization and neighboring base stations and determining necessity of the hand-over on the basis of a result of the measurement; message transmission means for generating a request message including the measured qualities and transmitting the generated request message to the synchronized base station when it is determined by the hand-over determination means that the hand-over is necessary; message retransmission means for monitoring an acknowledgement response from the synchronized base station in response to the transmitted request message and repeating the transmission of the request message when there is no response from the synchronized base station within a predetermined time; and receiving quality update means for renewing the measured qualities included in the message to latest values before the message retransmission means retransmits the request message.
Therefore, according to this invention, when the request message is retransmitted, the receiving quality measurement values inserted into the message are always updated to the latest values. For this reason, the destination of the hand-over can be always determined on the basis of the latest measurement values and thereby the optimum hand-over can be always executed, at the base station.
In according to the other aspect of the present invention, there is provided a mobile communication terminal apparatus having a function of detecting degradation of receiving quality thereof and transmitting a request for hand-over to a base station in a state of being in the established synchronization with any one of a plurality of
Chin Vivian
Kabushiki Kaisha Toshiba
Sharma Sujatha
LandOfFree
Mobile communication terminal apparatus having hand-over... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mobile communication terminal apparatus having hand-over..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mobile communication terminal apparatus having hand-over... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3251486