Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1998-03-02
2001-11-20
Olms, Douglas (Department: 2661)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S230000, C370S324000, C370S529000, 37, 37, 37
Reexamination Certificate
active
06320852
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a site diversity receiving method for use-with a mobile communications system and to a base-station host apparatus used in a mobile communications system employing the site diversity receiving method. More particularly, the present invention relates to a site diversity receiving method for use with a mobile communications system and to a base-station host apparatus used in a mobile communications system employing the site diversity receiving method, both of which are suitable for use with a mobile communications system such as an automobile cellular phone system or a portable telephone system.
(2) Description of the Related Art
In a mobile communications system, such as an automobile cellular phone system or a portable phone system, since a terminal station usually carries out communication while in a moving state, a propagation environment between the base station and the terminal station changes constantly. For example, the propagation environment changes due to fading or the like during a short period of time, deteriorating the quality of communication between the base station and the terminal station.
A representative countermeasure against such a phenomenon is a space diversity method in which the quality of a received signal is improved by composing into one signal (or selection of one of) a plurality of signals received from one base station via several different propagation paths.
However, from the viewpoint of a comparatively long period of time, the space diversity method cannot be expected to yield the effect of improving the quality of a received signal if the terminal station enters the shadow area produced by an obstacle such as a building and it becomes difficult for the terminal station to transmit/receive a signal to or from one base station. For these reasons, the space diversity method cannot be said to be an effective countermeasure. In view of the foregoing, a site diversity method has recently been increasingly adopted in the field of mobile communications system, which method permits the terminal station to simultaneously transmit or receive a signal to or from a plurality of base stations.
More specifically, under the site diversity method, a plurality of base stations receive a signal (or data) from one terminal station, and the data received by the respective base stations are processed and transmitted to an exchange (a higher-level apparatus in comparison with the base station and hereinafter often referred to as a base-station host apparatus). In the exchange, the received plurality sets of received data are selected or composed into one signal.
FIG. 26
is a schematic representation showing the concept of the site diversity method by which communication is established between a terminal station and a plurality of base stations. In
FIG. 26
, reference numerals
101
and
102
designate base stations;
103
a building (or an obstacle) existing in a communications area of the base station
101
; and
104
a terminal station.
For example, if the terminal station
104
enters a shadow area produced by the building
103
while it is in the course of communicating with the base station
101
, the presence of the building
103
makes it difficult for the terminal station
104
to smoothly transmit or receive a signal to or from the base station
101
. However, the site diversity method permits the base station
102
adjacent to the base station
101
to also receive a signal from the terminal station
104
. Consequently, in place of the base station
101
, the base station
102
can communicate with the terminal station
104
. As a result, the terminal station
104
can realize high-quality communication without being affected by the propagation environment (such as the presence of the building
103
).
Further, under the site diversity method, since a plurality of base stations receive a signal from the terminal station
104
, the minimum transmission level (or power) of the terminal station
104
required by the network to maintain the quality of communication is reduced, enabling a reduction in the power consumed by the terminal station
104
. Moreover, if the site diversity method is applied to a mobile communications system employing a CDMA (Code Division Multiple Access) method, there can be expected a reduction in interference power, which in turn allows the capacity of a subscriber's line to increase. In short, the application of the site diversity method to the CDMA method is very effective.
FIG. 27
is a block diagram showing one example of a mobile communications system to which the CDMA method and the site diversity method are applied. The mobile communications system
110
shown in
FIG. 27
comprises a terminal station
111
, base stations
112
-
1
to
112
-n (“n” is a natural number), and an exchange
113
.
In general, a wireless line of low quality (i.e., one which may be susceptible to circuit failures) is used for communication established between the terminal station
111
and the base stations
112
-
1
to
112
-n, whereas a wired line of high quality (i.e., substantially without circuit failures) is used for communication established between the base stations
112
-
1
to
112
-n and the exchange
113
. Because of this fact, such a communications system adopts a technique called error correcting code (ECC) in order to improve the quality of the circuit between the terminal
111
and the base stations
112
-
1
to
112
-n. The following techniques can be conceived as the error correcting code technique.
(1) Technique 1
As shown in
FIG. 28
, the terminal station
111
is provided with an error correcting encoder (ENC)
111
a
, and the base stations
112
-
1
to
112
-n are respectively provided with error correcting decoders (DECs)
112
a
-
1
to
112
a
-n. Further, the exchange
113
is provided with a selection section
123
a
for the purpose of making a selection from the signals decoded by the DECs
112
a
-
1
to
112
a
-n of the base stations
112
-
1
to
112
-n.
In the mobile communications system
110
shown in
FIG. 28
, the signal subjected to error-correction encoding processing performed by the ENC
111
a
of the terminal
111
is received by the respective base stations
112
-
1
to
112
-n via the wireless line. The signals are subjected to error-correction decoding processing performed by the DECs
112
a
-
1
to
112
a
-n of the base stations
112
-
1
to
112
-n. The thus-decoded signals are transmitted to the exchange
113
via the wire circuit. In the exchange
113
, a decoded signal (with minimum deterioration) is selected from the received and decoded signals as a received signal.
Although in the foregoing description any one of the decoded signals sent from the respective DECs
112
a
-
1
to
112
a
-n is selected, there may be a case where the exchange
113
is provided with a composing section in place of the selection section
113
a
, and the decoded signals from the error correcting decoders
112
a
-
1
to
112
a
-n are composed into one signal.
(2) Technique 2
As shown in
FIG. 29
, the terminal station
111
is provided with the ENC
111
a
, and the exchange
113
is provided with a composing section
125
a
and an error correcting decoder (DEC)
125
b.
In the mobile communications system
110
shown in
FIG. 29
, the base stations
112
-
1
to
112
-n receive a signal from the ENC
111
a
of the terminal station
111
via the wireless line, and the thus-received signals are transmitted to the exchange
113
from the base stations
112
-
1
to
112
-n via a wire circuit without being subjected to the error-correction decoding processing. In the exchange
113
, the signals (error-correction coded signals) received from the base stations
112
-
1
to
112
-n are composed into one signal. The thus-composed signal is then subjected to error-correction decoding processing performed by the DEC
125
b
. Although the signals from the respective base stations
112
-
1
to
112
-n are composed into one signal by the composing
Iwamoto Hiroaki
Kawabata Kazuo
Nakamura Takaharu
Obuchi Kazuhisa
Suda Kenji
Fujitsu Limited
Helfgott & Karas P.C.
Hom Shick
Olms Douglas
LandOfFree
Base station host apparatus used in mobile communication... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Base station host apparatus used in mobile communication..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Base station host apparatus used in mobile communication... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2604177