Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1997-06-23
2002-12-10
Trost, William (Department: 2683)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S422100, C455S436000, C370S331000
Reexamination Certificate
active
06493561
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to mobile communication systems and mobile station apparatuses, and, more particularly, to a mobile communication system in which a radio zone where a mobile station is to enter a wait state is determined by the electric field intensity of a received radio wave that arrives from a radio base station, and to a mobile station apparatus that receives communication service by accessing such a mobile communication system.
The present invention also relates to a mobile communication system wherein a mobile station selects a base station to which a request for a message channel is to be issued, based on announcement information from the base station.
2. Description of the Related Art
Recently, a variety of mobile stations including an automobile mobile station and a portable mobile station access a mobile communication system. With a competition between a plurality of carriers as a background, the number of mobile stations is increasing.
A mobile communication system may have a large-zone construction in which a base station covers a relatively wide service area or a small-zone construction in which a plurality of base stations cover a service area.
In a mobile communication system, radio base stations operated on a small transmission power and forming microcells or picocells are provided at the center of a big city characterized by a particularly large volume of traffic so that a multilayer cell is formed.
Radio base stations operated on a small transmission power are also provided in an underground passage and a tunnel in order to enlarge a radio zone sufficiently to eliminate a dead zone.
FIG. 1
shows a construction of a conventional mobile communication system.
Referring to
FIG. 1
, radio base stations
61
1
and
61
2
form adjacent radio zones
62
1
and
62
2
, respectively. In the radio zone
62
1
, a radio base station
61
3
forming a microcell
63
and a radio base station
61
4
forming a picocell
64
are provided so as to form a multilayer. Mobile stations
65
1
-
65
N
are located movable in the radio zones
62
1
and
62
2
, the microcell
63
and the picocell
64
.
In the radio base station
61
1
, an antenna
66
1
is connected to an antenna terminal of a transmission and reception unit
68
1
via a common antenna equipment unit
67
1
. A control terminal of the transmission and reception unit
68
1
is connected to an input and output terminal of a base station control device
69
1
. A line terminal provided in the transmission and reception unit
68
1
and a communication port of the base station control device
69
1
are connected to a control station (not shown) via a transmission device
70
1
and a communication link
71
1
.
Since the radio base stations
61
2
-
61
4
have the same construction as the radio base station
61
1
, the corresponding elements are designated by using suffixes 2-4 in the description below, and the illustration and description thereof are omitted.
An antenna
72
1
of the mobile station
65
1
, is connected to an antenna terminal of a transmission and reception unit
74
1
via a common antenna equipment unit
73
1
. A modulated input and a demodulated output of the transmission and reception unit
74
1
are connected to a microphone
75
1
and a speaker
76
1
, respectively. A control terminal of the transmission and reception unit
74
1
is connected to a control terminal of a control unit
77
1
. An input and output terminal of the control unit
77
1
is connected to a display and operation unit
78
1
.
Since the construction of the mobile stations
65
2
-
65
1
is the same as the mobile station
65
1
, the corresponding elements are designated by using suffixes 2−N in the description below, and the illustration and description thereof are omitted.
The base station control device
69
1
of the radio base station
61
1
in the above-described mobile communication system is directed by a center (not shown) via the communication link
71
1
and the transmission device
70
1
to generate announcement information including a wait enabled level and a wait disabled level as shown in FIG.
2
and transmits the announcement information to a predetermined control radio channel (hereinafter, simply referred to as a control channel) via the transmission and reception unit
68
1
, the antenna common equipment unit
67
1
and the antenna
66
1
.
In addition to the wait enabled level and the wait disabled level, the announcement information also includes a message type identifying transmitted information as the announcement information, a mobile station transmission power specification specifying a transmission power of the mobile station, a location code indicating a location of the radio zone (service area), and the like. However, the information items other than the wait enabled level and the wait disabled level does not have to do with the present invention, and the description thereof is omitted.
The control unit
77
1
of the mobile station
65
1
maintains a control channel table listing all the radio channels over which the announcement information described above is transmitted from the radio base stations forming the respective radio zones to which the mobile station
65
1
may be located. Further, upon power-on, the control unit
77
1
measures sequentially the electric field intensity L
1
of the control channel registered in the control table channel by controlling the transmission and reception unit
74
1
((
1
) of FIG.
3
). A determination is then made as to whether or not the measured electric field intensity is greater than a predetermined threshold level L
th
((
2
) of FIG.
3
).
The control unit
77
1
registers the control channels for which a determination that the measured electric field intensity is greater than the threshold level L
th
is obtained, in a prescribed area (hereinafter, referred to as a candidate zone register) in a main memory. The electric field intensity of the registered control channel is also registered in the candidate zone register so that the correspondence between the control channel and the associated electric field intensity is specified ((
3
) of FIG.
3
).
When the control unit
77
1
has completed a series of the above-described processes (hereinafter, referred to as a measurement process) for all the control channels registered in the control channel table, the control unit
77
1
determines whether or not the candidate zone register stores any control channel ((
4
) of FIG.
3
). If an affirmative answer is given, the control unit
77
1
sorts the entries in the candidate zone register according to the ascending order of the electric field intensity ((
5
) of FIG.
3
).
The control unit
77
1
refers to the candidate zone register when the sorting process has been completed and receives the announcement information via the individual control channels registered in the candidate zone register ((
6
) of FIG.
3
). The control unit
77
1
measures the electric field intensity again ((
7
) of FIG.
3
). Further, the control unit
77
1
compares the electric field intensity L
2
and the wait enabled level L
th
included in the announcement information ((
8
) of FIG.
3
). When the former is lower in level than the latter, a similar comparison is conducted for the other control channels registered in the candidate zone register ((
9
) of FIG.
3
). Hereinafter, a series of processes performed subsequent to the measurement process is referred to as a zone determination process. The control unit
77
1
restarts the measurement process when the electric field intensity is found to be below the wait enabled level L
th
for all the control channels subjected to the comparison ((
10
) of FIG.
3
).
If the electric intensity field of any of the control channels is found to be equal to or exceeds the wait enabled level, the control unit
77
1
establishes that control channel as a control channel for the radio zone in which the mobile station is to register its location, issues a call and receives an in
Fujitsu Limited
Katten Muchin Zavis Roseman
Nguyen Simon
LandOfFree
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