Multiplex communications – Communication over free space – Portable address responsive receiver
Reexamination Certificate
1998-02-26
2001-10-09
Kizou, Hassan (Department: 2738)
Multiplex communications
Communication over free space
Portable address responsive receiver
C370S335000, C370S342000, C340S007220, C455S458000
Reexamination Certificate
active
06301230
ABSTRACT:
TECHNICAL FIELD
The present invention relates to systems for paging a user carrying a radio pager. It relates in particular to techniques for transmitting a response signal from a radio pager to a base station when that pager has received a paging signal addressed to itself.
BACKGROUND ART
FIG. 1
is a block diagram showing a conventional radio paging system. To page radio paging receiver
106
-
1
or
106
-
2
from telephone terminal
101
, the number of radio paging receiver
106
-
1
or
106
-
2
, and the message if there is one, are input from telephone terminal
101
. This information is then input to central station
103
via public switched telephone network (PSTN)
102
as a paging request signal. At a central station
103
this paging request signal is converted to a paging signal sequence and transmitted to a plurality (herein denoted by n) of base stations
1041
to
104
-n. Base stations
104
-
1
to
104
-n receive this paging signal sequence using line terminators
107
, convert it to a radio signal (a radio wave) in transmitter
108
, and transmit it simultaneously at the same frequency F
f
to radio zones
105
-
1
to
105
-n of each respective base station. Radio paging receivers
106
-
1
and
106
-
2
each receive the radio signal at the predetermined frequency F
f
, and when either of these radio paging receivers detects a paging signal addressed to itself, it notifies the user that he or she has been paged.
FIG. 2
shows an example of the configuration of a paging signal sequence received by a radio paging receiver. This paging signal sequence comprises a frame sequence of period T comprising m frames of signal length &agr; joined together. The i-th frame comprises a synchronization signal and k
i
paging signals. Each paging signal comprises an address signal and a message signal. The receive function of a radio paging receiver is activated only during the receiving period of one or more pre-allocated frames of the m frames, whereupon it receives the frame or frames in question. This is called “intermittent receiving” and is intended to extend battery life in a radio paging receiver. For example, on the assumption, that radio paging receivers
106
-
1
and
106
-
2
have been allocated to the same frame i, the receive function of these radio paging receivers is activated only in frame i whereupon they receive paging signals in this frame i. Further, if both radio paging receivers
106
-
1
and
106
-
2
are paged in the same frame, then for example the paging signal transmitted to radio paging receiver
106
-
1
is paging signal i-l having the address signal of this receiver, and the paging signal transmitted to radio paging receiver
106
-
2
is paging signal i-
2
having the address signal of that receiver. When a radio paging receiver has detected a paging signal addressed to itself within the received frame, it outputs an audible tone or other alert, thereby notifying the user that he or she has been paged.
A problem with the radio paging system described above is that because it is a one-way communication system, the caller cannot know whether or not his paging request has reached the desired radio paging receiver. To overcome this problem, a two-way radio paging system has been proposed, wherein a radio pager with a transmission function is, used instead of a receive-only radio paging receiver, so that when a radio pager has detected a paging signal addressed to itself, it transmits a response signal to the base station to the effect that a paging signal has been received.
FIG. 3
is a block diagram showing a conventional two-way radio paging system. In this system, instead of central station
103
, base stations
104
-
1
to
104
-n and radio paging receivers
106
-
1
and
106
-
2
shown in
FIG. 1
, there are used central station
111
, base stations
112
-
1
to
112
-n and radio pagers
113
-
1
and
113
-
2
, all of which are capable of two-way communication.
To page radio pager
113
-
1
or
113
-
2
from telephone terminal
101
, a paging signal sequence is transmitted simultaneously at the same frequency F
f
to radio zones
105
-
1
to
105
-n of each respective base station, in the same manner as the prior art example illustrated in FIG.
1
. Radio pagers
113
-
1
and
113
-
2
each receive this paging signal sequence, and when either of these radio pagers detects a paging signal addressed to itself, it notifies the user that he or she has been paged. Subsequently, the paged radio pager
113
-
1
or
113
-
2
transmits to a base station a response signal to the effect that a paging signal has been received. It is also possible at this point to add a short message signal. The base station of the radio zone in which the radio pager is located receives this response signal at receiver
114
(the response signal transmitted by radio pager
113
-
1
is received by base station
112
-
1
and the response signal transmitted by radio pager
113
-
2
is received by base station
112
-
2
), and transmits the response signal via line terminator
107
to central station
111
. Central station
111
can then report via telephone network
102
to telephone terminal
101
that paging has been successful.
FIG. 4
shows an example of the configuration of a response signal transmitted by a radio pager. This response signal comprises a synchronization signal, the radio pager ID, and the response information. The response information can include a short message in, addition to a response to the effect that a paging signal has been received.
It is assumed herein that as in the case of a mobile phone, the frequency of the backward signal which a radio pager uses to transmit its response signal is set uniquely in relation to the frequency of the forward signal used to transmit the paging signal. Namely, F
b
is assumed to be set uniquely in relation to F
f
. Now, in a radio paging system a single forward signal frequency is used in all the radio zones. Therefore when a plurality of paging signals are transmitted in the forward signal, in all the radio zones a plurality of radio pagers will respond simultaneously using the same backward signal frequency. To avoid collision of such response signals and to improve the transmission quality of the backward signal, at least those radio pagers which have been paged simultaneously must send back their response signals at different times. For example, the backward signal is divided into a plurality of slots, each slot is allocated to one of the radio pagers which have been paged simultaneously, and the response signal from each radio pager is inserted in its allocated slot.
FIG.
5
and
FIG. 6
are block diagrams showing two examples of the configuration of a central station.
FIG. 5
shows an example of the configuration of central station
103
used in the one-way radio paging system illustrated in
FIG. 1
, while
FIG. 6
shows an example of the configuration of central station
111
used in the two-way radio paging system illustrated in FIG.
3
.
Central station
103
used in the one-way radio paging system comprises paging switch
121
, encoding unit
123
, distributor
124
, and a plurality of line terminators
126
. Paging switch
121
is connected to the telephone network and outputs paging request signals from this telephone network to encoding unit
123
. Encoding unit
123
converts these paging request signals to a paging signal sequence. Distributor
124
distributes this paging; signal sequence to each base station. Line terminators
126
each terminate a line to a base station and transmit the paging signal sequence from distributor
124
to a base station.
As opposed to this, central station
111
used in the two-way radio paging system comprises paging switch
122
, encoding unit
123
, distributor and concentrator
125
, and a plurality of line terminators
127
. Paging switch
122
is capable of two-way operation, while encoding unit
123
is on a par with the encoding unit of central station
103
shown in FIG.
5
. Distributor and concentrator
125
distributes the paging signal sequence output b
Ito Shogo
Mizuki Takayuki
Yamao Yasushi
Kizou Hassan
NTT Mobile Communications Network
Pillsbury & Winthrop LLP
Tsegaye Saba
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