Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1997-04-16
2001-01-09
Urban, Edward F. (Department: 2746)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S426100, C370S252000
Reexamination Certificate
active
06173184
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a network system for mobile radio communication in which a network system for mobile radio terminal is connected to a communication through a public or private radio base station to perform data communication with a server unit, and more particularly, to a network system for mobile radio communication which can prevent data losses even if slot errors or a drop in electric field strength occur between a mobile radio terminal and a public or private radio base station.
2. Description of the Prior Art
As shown in
FIG. 1
, a conventional network system for mobile radio communication is constituted by a radio connection unit
55
for selecting a line to be connected through a communication network
56
, radio base stations
53
and
54
respectively installed in a plurality of unit cells, and a mobile radio terminal (to be referred to as a PS hereinafter)
48
which establishes a radio channel with a radio base station while moving. The PS
48
includes a buffer memory (to be referred to as a BM hereinafter)
50
for temporarily storing data in a line switching operation, a data device
51
, a data processing apparatus
49
, and a communication controller
52
.
As a data transmission scheme in such a system, the scheme disclosed in Japanese Unexamined Patent Publication No. 59-212040 is available.
More specifically, when the radio base station (1)
53
determines the necessity for line switching during communication between the PS
48
and the radio base station (1)
53
, the radio base station (1)
53
sends a line switching notification to the radio connection unit
55
, and also sends a communication interruption notification to the data processing apparatus
49
. Upon reception of the notification, the data processing apparatus
49
transmits an acknowledgement signal to the radio connection unit
55
and starts to store, in the BM
50
, the communication data which has been directly transmitted. When the radio connection unit
55
receives the acknowledgement signal from the data processing apparatus
49
, the communication between the PS
48
and the radio base station (1)
53
is interrupted. While the data processing apparatus
49
is storing the communication data, line switching processing is performed. When the radio base station (2)
54
to serve next is determined, the radio connection unit
55
sends a switching instruction to the radio base station (1)
53
, that has been serving up until now, and the radio base station (2)
54
that is to serve next. Upon reception of the switching instruction, the radio base station (1)
53
as the currently serving station sends a switching instruction to the communication controller
52
. When these operations are complete, the communication is resumed. When the communication is resumed, the data processing apparatus
49
reads out the data stored in the BM
50
and transmits the data to the radio base station (2)
54
through the communication controller
52
. When all the data are read out from the BM
50
, direct communication without the mediacy of the BM
50
is started again.
The following problems are posed in the above conventional data transmission scheme.
First, in data transmission between a server unit, which is assumed to be outside the area covered by a communication network, and a PS, the server unit that transmits/receives data to/from the PS has no BM for storing data. For this reason, if a hit occurs during data transmission from the server unit to the PS, data is lost.
Second, no consideration is given to a case wherein line disconnection cannot be avoided because of continuous slot errors or a continuous reduction in electric field strength. For this reason, data is lost when the line is disconnected.
Third, the radio base station must monitor the reception state of the PS so as to send a line switching instruction thereto. For this reason, line switching processing is complicated, resulting in a decrease in line switching speed.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems in the conventional techniques, and has as its object to provide a network system for mobile radio communication in which a PS is connected to a public radio base station (to be referred to as a public CS hereinafter) or a private radio base station (to be referred to as a private CS hereinafter) to perform data communication with a server unit in a network, and which can prevent data losses even if slot errors or a reduction in electric field strength occur between a PS and the CS, thereby realizing highly reliable data transmission.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a network system for mobile radio communication (which is referred to as a network system for mobile radio communication using a public CS hereinafter) comprising a network constituted by a server unit and a client unit, a radio connection unit connected to a communication network, a public CS installed in a cell, and a PS which establishes a radio channel with the public CS while moving, the network system being adapted to perform data communication between the server unit and the PS, wherein each of the server unit and the PS includes a BM and an auxiliary storage unit which hold data, and the PS includes an electric field strength monitoring section for monitoring slot errors or a reduction in an electric field strength, stores data in the BM during data transmission to the server unit when a level based on slot errors or a reduction in electric field strength is not lower than a threshold for line switching, sends a line switching notification to the server unit, sends a line switching request to the public CS, and starts to transmit the data stored in the BM upon reception of a response indicating completion of line switching from the public CS.
According to the second aspect of the present invention, similar to the first aspect, there is provided a network system for mobile radio communication using a public CS, in which a PS includes a section for instructing a server unit to store data in a BM during data reception from the server unit when an electric field strength monitoring section determines that a level based on slot errors or a reduction in electric field strength is not lower than a threshold for line switching, a section for sending a line switching request to the public CS, and a section for notifying the server unit of completion of line switching upon reception of a response indicating completion of line switching from the public CS, and the server unit includes a section for starting to transmit the data stored in a BM.
According to the third aspect of the present invention, similar to the first aspect, there is provided a network system for mobile radio communication using a public CS, in which a PS includes a section for sending a server unit a notification indicating that preparation for line disconnection is in progress during data reception from the server unit when a level based on slot errors or a reduction in electric field strength is not lower than a threshold for line disconnection, a section for starting a timer, and a section for notifying the server unit of recovery of the electric field strength when the electric field strength is recovered within a disconnection determination time, and the server unit includes a section for storing data in a BM upon reception of the notification indicating that preparation for line disconnection is in progress from the PS, and a section for starting to transmit the data stored in a BM upon reception of a notification indicating that the electric field strength is recovered.
According to the fourth aspect of the present invention, similar to the first aspect, there is provided a network system for mobile radio communication using a public CS, in which a PS includes a section for storing data in a BM during data transmission to a server unit when an electric field strength monitoring section determines
Kikuchi Tsuneyuki
Matsumoto Hidehiro
Gesesse Tilamun
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Urban Edward F.
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