Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-03-16
2003-10-14
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S335000, C370S342000
Reexamination Certificate
active
06633556
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mobile station apparatus and a base station apparatus for performing data transmission of a CDMA (Code Division Multiple Access) system and a communication method using these apparatus.
BACKGROUND ART
In a mobile communication system of third generation, a CDMA system is planning to be used as a radio access system. Generally, in the CDMA system, a spreading code peculiar to each radio cell (radio base station) is used to a radio signal (forward link), which each radio base station transmits. Also, a spreading code peculiar to each mobile station is used with respect to a radio signal (reverse link), which each mobile station transmits.
In the CDMA system, an advantage in which the same frequency can be used between the adjacent radio cells (hereinafter referred to as cell as required) is exploited and a soft handover system is adopted as a handover system, which is used when the mobile station moves between cells. The soft handover system combines radio signals from the base station of the mobile source cell and the base stat on of the mobile destination cell.
In order to execute such a handover, the mobile station need to perform a peripheral cell search for searching the base station of the mobile destination cell. Each base station always transmits a radio channel, which is called perch channel. The perch channel is transmitted from each cell (base station) using an inherent spreading code.
Therefore, each station notifies the mobile station of the spreading code, which is used in the peripheral cells, of the self-station as broadcast information. On the other hand, the mobile station periodically detects a link quality (reception SIR (signal interference ratio) of the radio channel (perch channel of the peripheral cell) using the notified spreading code. Or, the mobile station periodically detects reception Eb/IO (a ratio of energy of a received signal per one bit to interference, a heat control power spectrum density ratio) Then, the mobile station notifies the network side of the detection result. By performing the so-called peripheral cell search, the network can determine to which cell the mobile station is moving.
FIG. 1
is a view showing an outline structure of a conventional mobile communication system, particularly the structure relating to the handover. The mobile communication system mainly comprises a mobile station, radio base stations and a control station.
A mobile station M mainly comprises a radio receiving and transmitting section
11
, a message decoder
12
, a spreading code storing section
13
, a reception quality detecting section
14
, a peripheral cell control section
15
, and a message generator
16
. The radio receiving and transmitting section
11
receives and transmits a radio signal between the mobile station M and the radio base station. The message decoder
12
decodes control information contained in the signal received by the radio receiving and transmitting section
11
. The spreading code storing section
13
stores spreading codes of an object to be subjected to the peripheral cell search designated from the network side, that is, the spreading codes used in the peripheral cells. The reception quality detecting section
14
detects the link quality of the signal received by the radio receiving and transmitting section
11
. The peripheral cell search control section
15
sets the spreading codes stored in the spreading code storing section
13
to be used in the peripheral cells with respect to the reception quality detecting section
14
, sequentially. Then, the peripheral cell search control section
15
manages the reception quality detecting cycle, and the number of times of detection, and provides an averaging processing to the detection result. The message generator
16
generates a message, including control information, to the network.
The radio base stations B mainly comprise a plurality of radio receiving and transmitting sections
17
, a wire receiving and transmitting section
18
, and a radio control section
19
. The radio receiving and transmitting sections
17
receive and transmit the radio signals between the mobile station and the radio base station. The wire receiving and transmitting section
18
receives and transmits control signals, that is, a mobile station control signal and a radio base station control signal between the control station and the radio base stations B via radio. The radio control section
19
controls the radio receiving and transmitting sections
17
in accordance with a designation from the control station. A plurality of radio base stations Ba, Bb, and Bc thus structured is provided.
The control section C mainly comprises a station site storing section
20
, a peripheral cell information generator
21
, a wire receiving and transmitting section
22
, a message decoder
23
, a mobile direction determination section
24
, a handover control section
25
, and a message generator
26
. The station site storing section
20
stores the inherent spreading code, which is used by the radio base station under the control of the self-station. The peripheral cell information generator
21
generates peripheral cell information for each radio cell based on station site information stored in the station site storing section
20
. The wire receiving and transmitting section
22
receives and transmits control signals, which are received and transmitted from/to the radio base stations Ba, Bb, and Bc. The message decoder
23
decodes control information from the mobile station. The mobile direction determination section
24
determines a mobile destination cell of the mobile station based on a peripheral cell search result report from the mobile station and information from the station site storing section
20
. The handover control section
25
designates the execution of the handover to the mobile station M and the radio base stations B when it is determined that the handover is needed based on information from the mobile direction determination section
24
. The message generator
26
generates a message including control information on the mobile station M and the radio base stations B.
Next, an operation of the handover of the above-structured conventional mobile communication system will be explained with reference to FIG.
2
.
The spreading code which each radio base station uses as a reverse link is set in advance, and information on the spread code setting is managed by the station site storing section of the control station.
The radio control section
19
of the radio base station Ba uses a predetermined spreading code Ca as a forward link, and the mobile station M uses a spreading code Cm peculiar to the mobile station as a reverse link.
The mobile station M is in a cell area. The mobile station M receives a peripheral cell spreading code notice from the radio base station Ba offering a service of the cell a, so that the spreading codes used in the peripheral cells are stored in the spreading code storing section
13
(ST
1
).
The peripheral cell search control section
15
sets a cell search execution cycle &Dgr;t in a timer T (ST
2
). Then, when the timer counts up (ST
3
), the spreading codes, which are used by the peripheral cells stored in the spreading code storing section
13
, are sequentially set in the reception quality detecting section
14
. The reception quality detecting section
14
detects the reception quality from the peripheral cells of the radio base station Ba (ST
4
).
Next, the peripheral cell search result is reported to the network. The above explained a case in which the peripheral call search result was reported to the network every time when each peripheral cell search was executed. However, the result is not necessarily reported to the network every time.
The mobile direction determination section
24
of the control station C first determines the mobile direction based on the peripheral cell reception quality report from the mobile station M (ST
5
) to determine whether or not the cell movement is needed. If it is d
Greenblum & Bernstein P.L.C.
Hyun Soon-Dong
Matsushita Electric - Industrial Co., Ltd.
Nguyen Chau
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