Base station in a mobile communication system

Details Base station in a mobile communication system Base station in a mobile communication system

1999-12-16

2003-07-01

Vo, Nguyen T. (Department: 2682)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C455S561000

Reexamination Certificate

active

06587465

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system in which data exchange between a base station and a mobile terminal is performed in an asynchronous transfer mode (ATM), and particularly to a base station in a mobile communication system.
2. Description of the Related Art
There have been proposed a variety of mobile communication systems. For example, there have been disclosed examples of mobile communication systems such as in Japanese Patent Application Laid-Open Nos. HEI-9-261725(261725/1987), HEI-10-42337(42337/1998) and HEI-10-145835(145835/1998).
The mobile communication system disclosed in the Japanese Patent Application Laid-Open HEI-9-261725 aims at effectively utilizing a link between a base station and an MSC (Mobile Switching Center), by rejecting those data which have not been normally received by the base station at soft hand-over.
FIG. 5
is a block diagram of a base station in a mobile communication system described in the Japanese Patent Application Laid-Open HEI-9-261725.
The base station transmits and receives wireless communication data via antenna
1
and transmission/receipt distribution circuit
3
. Wire circuit receiving circuit
15
receives user data from a wire network, and transmits the received user data to a controlling circuit
23
which performs error check of the user data. User data free of errors are converted into wireless communication data and then transmitted, via encoding circuit
17
, modulating circuit
19
, transmitting circuit
21
, transmission/receipt distribution circuit
3
and the antenna
1
. Contrary, from the wireless communication data received via antenna
1
, transmission/receipt distribution circuit
3
, receiving circuit
5
, demodulator circuit
7
, decoding circuit
9
and error detecting circuit
11
, there is extracted a wireless communication quality information which is then transmitted to the controlling circuit
23
. This controlling circuit
23
checks a wireless communication quality based on the wireless communication quality information.
The received data are rejected when the check result of the wireless communication quality is very bad, while the received data are outputted via wire circuit transmitting circuit
13
when the check result of the wireless communication quality is favorable.
Meanwhile, there is adopted an ATM network for connecting a transmitting end side base station and a receiving end side base station.
However, there is a problem in the prior art shown in
FIG. 5
, as follows.
In the mobile communication system shown in
FIG. 5
, when a transmitting mobile terminal side base station has failed to normally receive data from a transmitting mobile terminal, the transmitting mobile terminal side base station rejects all of the received data. In this case, the transmitting mobile terminal side base station transmits valid data only, to an accompanying or receiving mobile terminal side base station via MSC (Mobile Switching Center), i.e., via ATM (Asynchronous Transfer Mode) network.
In communication via ATM network, data pattern transmitted from a transmitting mobile terminal side base station may differ from that received by a receiving mobile terminal side base station, due to a cause of delay fluctuation. In the mobile communication systems shown in
FIG. 5
, there are not provided any countermeasures, causing such a first problem that an output pattern at the time of data transmission from receiving mobile terminal side base station toward a receiving mobile terminal differs from a data transmission pattern at the time of data transmission from a transmitting mobile terminal toward a transmitting mobile terminal side base station, due to a cause of fluctuation in an ATM network.
FIG. 6
shows a data transmission sequence between a receiving mobile terminal side base station and a receiving mobile terminal. In
FIG. 6
, dotted line arrow Y represents a state in which data are outputted in a normal manner.
However, as represented by a solid line arrow Z in
FIG. 6
, a certain cell data to be received by a receiving mobile terminal side base station has arrived too early due to a delay fluctuation in the ATM network, resulting in that the data output is hastened by one frame, causing occurrence of transmission interval abnormality.
FIG. 7
is a block diagram of a mobile communication system disclosed in the Japanese Patent Application Laid-Open No. HEI-10-42337.
In this mobile communication system, base stations
111
,
112
,
11
n
receive wireless communication data at data receiving means
1111
,
1121
,
11
n
1
, respectively, extract user data, wireless communication quality informations and wireless communication frame numbers from the wireless communication data, respectively, and convert them into short packets, respectively, at short cell generating means
1112
,
1122
,
11
n
2
. Further, the base stations
111
,
112
,
11
n
multiplex a plurality of short cells by short cell multiplexing means
1113
,
1123
,
11
n
3
, respectively, map the multiplexed data into ATM cells by ATM cell transmitting means
1114
,
1124
,
11
n
4
, respectively, and then transmit the data to a mobile communication switching station
10
.
This type of mobile communication system also has a problem as follows.
First problem resides in that the quality of wireless communication data received by the base stations are checked by the mobile communication switching station
10
in this mobile communication system, so that wireless communication data are transmitted up to the mobile communication switching station
10
even when some error has occurred in the wireless communication data, resulting in wasteful usage of bands.
In
FIG. 8
, it is supposed that a base station BS(
0
) has received error data b(
0
). Since this b(
0
) is error data, wasteful data is transmitted between the BS(
0
) and MSC. Unfortunately, the function for rejecting the data is provided in the MSC side, so that the BS(
0
) is obliged to transmit the error data b(
0
) to the MSC, resulting in wasteful usage of bands.
Further, at the time of soft hand-over, there exist a plurality of paths from the mobile terminal to base stations and the mobile communication switching station, causing such a second problem that the aforementioned problem will occur in the plurality of paths.
For example, referring to
FIG. 8
, it can be seen that there is occurring such a situation that bands are wasted between other BS's and the MSC similarly to between BS(
0
) and MSC.
Further, since the short cell multiplexing means
1113
,
1123
,
11
n
3
are adopted, even short cells of error data are multiplexed due to the aforementioned first and second problems, resulting in a third problem that multiplexing waiting times of other users are increased.
The aforementioned Japanese Patent Application Laid-Open HEI-10-145835 provides a mobile communication system having a transmission path made into an ATM type, by which uninterrupted hand-over can be realized.
In this mobile communication system, when a mobile terminal has moved from one cell to another cell during communication, the frames including the same data received at asynchronous timings different from each other from both wireless base stations in respective cell areas received by a mobile switching center and identified thereby, there is then selected that data the header information of which has the lowest error rate, and frame exchange is performed at a designated timing. Further, replication of frame to be transmitted to a plurality of wireless base stations is performed, transmission timings are specified based on the header information thereof, and transmission is performed by those timings, to thereby realize uninterrupted hand-over.
However, this mobile communication system has a problem due to delay fluctuation, similarly to the mobile communication system disclosed in the aforementioned Japanese Patent Application Laid-Open HEI-9-261725.
SUMMARY OF THE INVENTION
The present invention has been carried out in view of the

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