Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-10-08
2003-11-04
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C370S338000, C370S328000
Reexamination Certificate
active
06643524
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a communication system between a base station and a base station controller in a mobile communication system and, in particular, to a communication system between a base station controller and a plurality of base stations serially connected to the base station controller by the use of a single shared communication line.
A mobile communication system is well known which comprises a base station controller connected to a mobile communication exchange through a wire link, and a plurality of base stations connected to the base station controller through wire links, respectively. Each base station is connected through a radio link to a plurality of mobile stations within a service area of the base station.
FIG. 1
is a block diagram showing an example of a structure of a typical conventional mobile communication system.
The mobile communication system exemplified in
FIG. 1
includes a mobile communication exchange
600
connected through a communication line
630
to a public exchange network, a base station controller
610
, and a plurality of base stations (#
0
, #
1
, #
2
)
620
,
621
, and
622
. The mobile communication exchange
600
is connected through a communication line
640
to the base station controller
610
. The base station controller
610
is connected to the base stations (#
0
, #
1
, #
2
) through independent communication lines
650
,
651
, and
652
, respectively.
Mobile terminals have no direct concern with this invention and, therefore, are not illustrated in this figure and subsequent figures.
In the system illustrated in
FIG. 1
, the communication line
650
serves as a private communication line between the base station controller
610
and the base station (#
0
)
620
. Likewise, the communication lines
651
and
652
serve as private communication lines independent from each other.
However, in case where a service area of a particular base station, for example, the base station (#
0
)
620
always has a small traffic (i.e., a load), the transmission efficiency of the communication line
650
is degraded.
In view of the above, development is made of a system in which a plurality of base stations having a small traffic are serially connected to a single communication line connected to a base station controller in order to share the single communication line among the base stations.
FIG. 2
is a block diagram showing an example of a structure of a conventional mobile communication system adopting a base station serial connection system of the type. A similar technique is disclosed in Japanese Unexamined Patent Publication (JP-A) No. 56-156034.
The mobile communication system exemplified in
FIG. 2
includes a mobile communication exchange
700
connected through a communication line
730
to a public exchange network, a base station controller
710
, and a plurality of base stations (#
0
through #
2
)
720
,
721
, and
722
. The mobile communication exchange
700
is connected through a communication line
740
to the base station controller
710
. The base station controller
710
is connected to the base station (#
0
)
720
through a communication line
750
. To the base station (#
0
)
720
, the base station (#
1
)
721
is serially connected through a communication line
751
. The base station controller
710
and the base station (#
2
)
722
are connected through a private communication line
752
, in the manner similar to the conventional system illustrated in FIG.
1
.
In the above-mentioned base station serial connection system, the communication line
750
is used as a shared communication line through which communication data between the base station controller
710
and the base station (#
0
)
720
and another communication data between the base station controller
710
and the base station (#
1
)
721
are multiplexed and transmitted, for example, according to a time-division multiplex communication system.
FIG. 3
is a view of a frame structure showing one example of the multiplex communication system for the shared communication line
750
in FIG.
2
. In the illustrated example, a communication line of 2 Mbps is used. The communication line of 2 Mbps has a frame rate of 8000 frame/second. Each single frame is composed of 32 time slots each of which is eight bits long. Each time slot has a transmission capacity of 64 Kbps. In the frame structure illustrated in
FIG. 3
, the 32 time slots (TSO through TS
31
) contains a synchronization TS
800
for establishing frame synchronization and a control TS
810
for controlling the shared communication line. The remaining 30 time slots other than the synchronization TS
800
and the control TS
810
are used as TS groups
820
and
821
assigned to communication with the base station (#
0
)
720
and to communication with the base station (#
1
)
721
, respectively. In this conventional example, the two base stations (#
0
)
720
and (#
1
)
721
are serially connected. In case where a greater number of base stations are serially connected, the 30 communication time slots are assigned to communication with the respective base stations, taking their traffics into consideration.
As described above, in the conventional mobile communication system, the transmission capacity of the shared communication line is preliminarily distributed fixedly to the respective base stations, taking their traffics into consideration, to realize serial connection of the base stations by the shared communication line.
However, the above-mentioned conventional base station serial connection system in the mobile communication system is disadvantageous in the following respects.
First, the maximum transmission rate to each base station is determined by the transmission capacity of the shared communication line, which is preliminarily physically assigned upon installation of the base station. In this connection, the transmission capacity must be assigned assuming the greatest traffic of each base station at the busiest state. Therefore, at the base station exhibiting wide variation in load, the transmission capacity assigned thereto can not effectively be utilized in a normal state so that the line efficiency is decreased. On the other hand, in case where an excessive load exceeding the maximum transmission rate assumed as mentioned above is temporarily applied, restriction is imposed upon transmission.
In case where a particular base station has a high load exceeding the maximum transmission rate, another base station may possibly have a small load leaving a spare transmission capacity. Even in this event, the spare transmission capacity can not be utilized by the particular base station of the high load because the transmission capacity assigned to each base station is fixed. Thus, restriction is imposed upon transmission so that the line efficiency of the shared communication line is decreased as a whole.
The transmission capacity of the shared communication line is preliminarily physically assigned to each base station upon installation of the base station. Therefore, in order to additionally install a new base station to be serially connected to the shared communication line, it is necessary to change the transmission capacity assigned to each of the existing base stations connected to the shared communication line. This requires modification in facility of the existing base stations.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, it is an object of this invention to provide a base station serial connection communication system in a mobile communication system, which can be flexibly adapted to load variation of each base station and additional installation of a new base station and which has a high line efficiency.
According to this invention, there is provided a base station serial connection communication system in a mobile communication system including a base station controller for controlling a plurality of base stations serially connected through a
Horikawa Kiyotaka
Ishii Nobuaki
Corsaro Nick
Foley & Lardner
Maung Nay
NEC Corporation
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