Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-04-16
2004-08-03
Gary, Erika (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S458000, C455S011100
Reexamination Certificate
active
06771958
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to wireless communications systems and, in particular, to paging a mobile-telephone in a wireless communications system.
BACKGROUND OF THE RELATED ART
The capacity of wireless communications systems is limited by a variety of factors including total transmission power at base stations.
FIG. 1
depicts a wireless communication system
10
comprising at least one base station (BS)
12
in communication with a plurality of mobile-telephones (MT)
14
-
j
, where j=1, . . . ,n. BS
12
transmits signals
16
-
j
to MT
14
-
j
over one or more downlink channels. Each signal
16
-
j
has an associated power level P
j
at which it is transmitted, wherein the value of power level P
j
depends on a variety of factors including distance and interference caused by buildings. The transmission power P
BS
of BS
12
is equal to the sum of P
j
, i.e.,
P
BS
=
∑
j
=
1
j
=
n
P
j
.
However, P
BS
cannot exceed a maximum transmission power level P
max
associated with BS
12
, i.e., P
BS
≦P
max
. Thus, the number of mobile-telephones
14
-
j
BS
12
can be in communication simultaneously (i.e., capacity) is limited by P
max
.
Suppose some mobile-telephones in communication with BS
12
are in building
27
, see FIG.
2
. BS
12
transmits signals
20
-
k
to MT
14
-
k
, wherein each signal
20
-
k
has an associated power level P
k
at which it is transmitted, where k=n+1, . . . ,m. In this situation, the transmission power P
BS
of BS
12
is equal to the sum of P
j
and P
k
, i.e.,
P
BS
=
∑
j
=
1
j
=
n
P
j
+
∑
k
=
n
+
1
k
=
m
P
k
.
However, since mobile-telephones
14
-
k
are indoors, the interference level (due to the presence of building
27
) is greater between MT
14
-
k
and BS
12
than between MT
14
-
j
and BS
12
. Thus, the power level P
k
required for mobile-telephones
14
-
k
to receive signal
20
-
k
at an acceptable signal level will likely be higher than the power level P
j
required for mobile-telephones
12
-
j
to receive signal
16
-
j
at an acceptable signal level, i.e., P
k
is likely greater than P
j
. Because MT
14
-
k
utilize more of BS
12
's transmission power resources, the number of mobile-telephones that BS
12
can be in communication simultaneously is reduced.
One way to increase the capacity in the situation depicted in
FIG. 2
is to use a device referred herein as a concentrator.
FIG. 2
a
illustrates a wireless communication system in which a concentrator
25
is incorporated. Concentrator
25
is a device having the functionality of a base station. Specifically, concentrator
25
is configured to communicate with mobile-telephones in building
27
, such as MT
14
-
k
, using frequency f
2
and with base station
12
using frequency f
1
. Any transmission from BS
12
to MT
14
-
k
, or vice-versa, goes through concentrator
25
. For example, BS
12
transmits a signal having a message intended for MT
14
-
k
to concentrator
25
over a communication channel on frequency f
1
. Upon receipt of the signal, concentrator
25
demodulates the message and re-modulates the message for re-transmission to MT
14
-
k
over a communication channel on frequency f
2
, wherein the signal transmitted from BS
12
to concentrator
25
is transmitted at power level P
c
. Advantageously, the transmission power P
c
associated with a frequency f
1
signal being transmitted from concentrator
25
to BS
12
would be less than the transmission power P
k
associated with a frequency f
1
signal being transmitted from MT
14
-
k
directly to BS
12
(since signal be would not suffer interference due to building
27
before arriving at the concentrator). Thus, the total transmission power P
BS
of BS
12
would be equal to sum of P
j
plus mP
c
, where m-n-1 corresponds to the number of mobile-telephones inside building
27
in communication with BS
12
via concentrator
25
, i.e.,
P
BS
=
∑
j
=
1
j
=
n
P
j
+
(
m
-
n
-
1
)
P
c
.
When BS
12
desires to page a mobile-telephone, BS
12
transmits a paging signal using a paging channel on frequency f
1
associated with that mobile-telephone. Each mobile-telephones is associated with only one paging channel from a set of paging channels on frequency f
1
. Thus, different mobile-telephones may be associated with different paging channels on frequency f
1
. In order for concentrator
25
to detect paging signals on different frequency f
1
paging channels intended for MT
14
-
k
in building
27
(and subsequently re-transmit on a paging channel on frequency f
2
), concentrator
25
needs to be capable of at least monitoring all the paging channels associated with the mobile-telephones
14
-
k
. However, concentrators are typically capable of only monitoring a single paging channel on frequency f
1
. Thus, unless the paging channel associated with the mobile-telephone to which the paging signal is intended is identical to the paging channel being monitored by (or associated with) concentrator
25
, the paging signal will not be detected by concentrator
25
(and will not be re-transmitted to the intended mobile-telephone). According, there exist a need for a concentrator to detect a paging signal intended for a mobile-telephone having an associated paging channel on frequency f
1
different than a paging channel on frequency f
1
associated with the concentrator.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus for detecting a paging signal intended for a mobile-telephone having an associated frequency f
1
paging channel different from a frequency f
1
paging channel associated with a concentrator. The present invention uses the paging channel on frequency f
1
associated with the concentrator to send a paging signal to a mobile-telephone having an associated paging channel on frequency f
2
different than the concentrator's paging channel on frequency f
1
. In one embodiment, a base station transmits a base station-to-mobile-telephone (BS-MT) paging message by including such BS-MT paging message in a base station-to-concentrator (BS-C) paging message. The BS-MT paging message includes a message portion and a mobile-telephone identifier portion, wherein the mobile-telephone identifier portion indicates the mobile-telephone to which the BS-MT paging message is intended. The BS-C paging message includes the MT paging message and a concentrator identifier portion for indicating the concentrator to which the BS-C is intended. The BS-C paging message is transmitted over a paging channel on frequency f
1
associated with the intended concentrator (i.e., concentrator through which the mobile-telephone is linked to the base station). The intended concentrator detects the BS-C paging message by monitoring its associated paging channel on frequency f
1
for a BS-C paging message with a concentrator identifier portion indicating the concentrator. Upon detecting its BS-C paging message, the concentrator parses the BS-MT paging message from the BS-C message and transmits the BS-MT paging message to the intended mobile-telephone using a paging channel on frequency f
2
being monitored by the mobile-telephone.
In one embodiment, the base station uses a location registry to determine the paging channel on frequency f
1
over which to send a BS-MT paging message to the mobile-telephone, wherein the location registry includes information indicating whether a mobile-telephone linked to the base station via a concentrator and, if applicable, a concentrator identifier and an indication of the paging channel associated with the concentrator. If the intended mobile-telephone is linked to the base station via a concentrator, the base station uses the location registry to determine the paging channel on frequency f
1
associated with the concentrator before sending a BS-C paging message having the BS-MT paging message on that paging channel.
REFERENCES:
patent: 5519761 (1996-05-01), Gilhousen
patent: 5544223 (1996-08-01), Robbins
patent: 5
Koo Yuen-Yin L.
Mizikovsky Semyon B.
Pittampalli Eshwar
Gary Erika
Lucent Technologies - Inc.
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