Multiplex communications – Duplex – Convertible to half duplex
Reexamination Certificate
2000-02-07
2004-05-18
Jung, Min (Department: 2663)
Multiplex communications
Duplex
Convertible to half duplex
Reexamination Certificate
active
06738359
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to communication format control methods and apparatuses, and more particularly to a communication format control method and apparatus for a mobile communication system which is capable of providing simplex and duplex communication services to a mobile station in each zone via a plurality of base stations.
In simplex communication, a person cannot speak while the other person is speaking. However, the communication between the two persons can be made via a single communication channel (traffic channel TCH
1
up or TCH
1
down), thereby making it possible to effectively utilize the communication channel (frequency). For this reason, the simplex communication is popularly used in mobile communication systems including independent systems.
2. Description of the Related Art
FIGS. 1 through 7B
are diagrams for explaining the prior art, and show various communication phases and the like conforming to a mobile communication standard of Japan.
FIG. 1
is a diagram showing a communication phase of a duplex communication conforming to the standard. In
FIG. 1
, MS
1
and MS
2
denote mobile stations, BS denotes a base station, CAC denotes a common access channel, and USC denotes a user specific channel. The common access channel CAC includes a broadcast control channel BCCH, a paging channel PCH, a signaling control channel SCCH, and a user packet channel UPCH.
When the mobile station MS
1
calls the mobile station MS
2
by a “duplex call setup”, the base station BS in response to this “duplex call setup” returns a “call setup accept” to the mobile station MS
1
and pages the mobile station MS
2
by a “duplex communication”.
FIG. 2
is a diagram showing a format of a call setup message conforming to the standard. As shown in
FIG. 2
, the format includes “transfer capacity” in the fourth column.
FIG. 3A
is a diagram showing a format of the “transfer capacity” in conformance with the standard. A “communication format” column is located at an octet
4
a
shown in FIG.
3
A.
FIG. 3B
is a diagram showing a bit coding of the “communication format” in conformance with the standard. In
FIG. 3B
, “000” indicates simplex communication, and “010” indicates duplex communication.
Returning now to the description of
FIG. 2
, when the mobile station MS
2
returns a “communication enable”, the base station BS in response to this “communication enable” sends a synchronizing signal SB
1
to the mobile station MS
1
by the user specific channel USC, and specifies a radio channel by the common access channel CAC. In response to this specifying of the radio channel, the mobile station MS
1
switches the frequency to the specified radio channel, and establishes synchronization with the base station BS by exchanging subsequent synchronizing signals SB
1
through SB
4
. In addition, the base station BS also establishes synchronization with the mobile station MS
2
in a similar manner, and calls the mobile station MS
2
. When a response is received from the mobile station MS
2
, a duplex communication state is reached between the mobile stations MS
1
and MS
2
.
FIG. 4
is a diagram showing a communication phase of a simplex communication conforming to the standard. When the mobile station MS
1
calls the mobile station MS
2
by a “simplex call setup”, the base station BS in response to this “simplex call setup” returns a “call setup accept” to the mobile station MS
1
and pages the mobile station MS
2
by a “simplex communication”. When the mobile station MS
2
returns a “communication enable”, the base station BS in response to this “communication enable” sends a synchronizing signal SB
1
to the mobile stations MS
1
and MS
2
for a predetermined time by the user specific channel USC, and specifies a radio channel with respect to the mobile stations MS
1
and MS
2
by the common access channel CAC. In response to this specifying of the radio channel, the mobile stations MS
1
and MS
2
switch the frequency to the specified radio channel, and when a traffic channel TCH (B/I=I) is received from the base station BS, the mobile stations MS
1
and MS
2
assume an enabled state accessible by the simplex communication. Here, B/I denotes busy/idle bits.
In this state, when a press-to-talk of the mobile station MS
1
is turned ON, the mobile station MS
1
establishes a send synchronization between the mobile station MS
1
and the base station BS, and thus, the traffic channel TCH (speech) from the mobile station MS
1
is received by the mobile station MS
2
. When the press-to-talk of the mobile station MS
1
is turned OFF, the mobile station MS
1
releases the right to send, and the mobile stations MS
1
and MS
2
again assume the enabled state accessible by the simplex communication. The operation of the mobile station MS
2
when the press-to-talk is turned ON is the same as in the case of the mobile station MS
1
.
FIGS. 5 and 6
are diagrams showing a communicating channel switching phase (re-calling type) of the simplex communication conforming to the standard.
FIG. 5
shows a case where the mobile station MS
1
which is communicating with the mobile station MS
2
via a base station BS
1
by a simplex communication moves to another zone during the communication. When the down-level deteriorates, the mobile station MS
1
searches for a perch channel, and makes a re-calling during communication by a “simplex communication re-call setup” with respect to a selected base station BS
2
. Responsive to this “simplex communication re-call setup”, the base station BS
2
returns a “re-call setup accept” to the mobile station MS
1
by the common access channel CAC, sends a synchronizing signal SB
1
to the mobile station MS
1
by the user specific channel USC, and specifies a radio channel by the common access channel CAC. In response to this specifying of the radio channel, the mobile station MS
1
switches the frequency to the specified radio channel, and establishes synchronization with the base station BS
2
by exchanging subsequent synchronizing signals SB
1
through SB
4
. When a traffic channel TCH (B/I=B) is received from the base station BS
2
, the traffic channel TCH (speech) from the mobile station MS
1
is continuously received by the mobile station MS
2
via the base stations BS
2
and BS
1
.
FIG. 6
is a diagram showing a case where the mobile station MS
1
is making a reception. When the down-level deteriorates, the mobile station MS
1
searches for a perch channel, and makes a re-calling during reception by a “simplex communication re-call setup” with respect to the selected base station BS
2
. Responsive to this “simplex communication re-call setup”, the base station BS
2
returns a “re-call setup accept” to the mobile station MS
1
by the common access channel CAC, sends a synchronizing signal SB
1
to the mobile station MS
1
for a predetermined time by the user specific channel USC, and specifies a radio channel by the common access channel CAC. In response to this specifying of the radio channel, the mobile station MS
1
switches the frequency to the specified radio channel, and establishes synchronization with the base station BS
1
. The traffic channel TCH (speech) from the mobile station MS
2
is continuously received by the mobile station MS
1
via the base stations BS
1
and BS
2
.
FIGS. 7A and 7B
are diagrams for explaining a conventional communication format control method.
FIG. 7A
shows a case where a mobile station MS
1
in a zone Z
1
calls a mobile station MS
2
in the same zone Z
1
by a simplex communication. In this case, a base station BS
1
(that is, a radio line control unit MCU
30
) allocates a traffic channel TCH
1
, for example, with respect to the mobile stations MS
1
and MS
2
via the common access channel CAC. In this state, when the press-to-talk of the mobile station MS
1
is turned ON, the mobile station MS
1
establishes a send synchronization with the base station BS
1
by the traffic channel TCH
1
up, and the communication (speech) from the mobile station MS
1
Fujitsu Limited
Jung Min
Katten Muchin Zavis & Rosenman
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