JP2000224636A - Hand-off method and cdma system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an interference wave from other station by transmitting a pilot strength measurement message from a base station received by a mobile station to the base station and other base station before execution of soft hand- off when the mobile station moves to an area of the other base station, allowing the other base station to start reception from the mobile station and allowing the base station to apply transmission power control to the mobile station. SOLUTION: A mobile terminal station(MS) that communicates with a CDMA radio base station device (BTS) 10 and is moving toward a mini BTS 20, receives control data of a transmission output of the MS 30 sent from the BTS 10 to control an amplification factor of transmission power. In this case, before the MS 30 executes soft hand-off in compliance with the IS-95 for the mini BTS 20, the mini BTS 20 starts receiving reception power message information from the MS 30 and executes transmission power control for the MS 30 via the BTS 10 to prevent increase in an undesired incoming area interference wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for soft handoff in a code division multiple access (CDMA) system.
The present invention relates to a handoff method between base stations having different transmission powers.

[0002]

2. Description of the Related Art Generally, in a radio communication system using a code division multiple access (CDMA) system, in particular, in a cellular mobile communication system, a limited number of frequency bands are used in one area (cell). The ability to have a line capacity is important in system design.

In the code division multiple access (CDMA) system, a plurality of users communicate on the same frequency,
There is also a demand for reduction of interference between user communications due to orthogonality between codes assigned to each user. In order to sufficiently extract the orthogonality between the codes, the problem can be solved by making the levels of a plurality of received waves at the receiving point all the same. Therefore, in a cellular mobile communication system,
In particular, with regard to uplink communication (mobile station → base station) that ensures synchronization between mobile stations existing in the same base station area, it is required that all received waves from the mobile stations at the base station can be received at the same level. Generally, strict transmission power control is performed in a mobile station.

Japanese Patent Laid-Open No. Sho 6 discloses a transmission power control method for a traffic channel of this uplink communication (mobile station → base station).
Japanese Unexamined Patent Publication No. 2-92526 discloses that level control of an uplink traffic channel is performed on the receiving side of a base station, and Japanese Unexamined Patent Publication No. 7-95151 discloses initial transmission power of a downlink (base station to mobile station) traffic channel. Is disclosed.

Further, Japanese Patent Application Laid-Open No. 9-74378 (Patent Publication No. 2762965) discloses that a mobile station, which is a special feature in a code division multiple access (CDMA) system, performs communication simultaneously with a plurality of base stations. Discloses the activation of soft handover (soft handoff) for selecting an appropriate base station for communication.

According to this publication, in a cellular mobile communication system comprising a mobile station, a plurality of base stations, and an upper station connected to the base station and utilizing a code division multiple access (CDMA) system, The mobile station, at the time of soft handoff performing communication simultaneously with the plurality of base stations, receives the pilot channel reception power from the soft handoff destination base station in addition to the pilot channel reception power from the communicating base station as report information. The upper station receives the report information and the transmission power control information of the traffic channel of the communicating base station, and communicates the information with the communicating base station. It is described that the data is transferred to a handoff destination base station.

According to this publication, a pilot channel receiving section of a mobile station downconverts, despreads, and extracts a pilot channel whose reception level is detected by an envelope detection section, and the reception level information is transmitted data. Is transmitted to the base station, and the base station transmits this reception level information to the upper station, and the mobile station sets the transmission power of the traffic channel as the optimum transmission power of the downlink traffic channel according to the reception level information that has been returned and transferred. Sent to.

[0008] As described above, the conventional soft handoff method uses a high-power base station radio (BTS) as an upper station.
The mobile station radio equipment (MS), which is a mobile station, measures the pilot signal strength, and when the pilot signal strength exceeds a certain set value, the upper-level station (BT) during the call
A method of requesting a handoff for S) has been adopted.

[0009]

However, this conventional method has the following problems. As shown in FIG.
When the area 21 going up from the mobile station to the base station 20 is sufficiently larger than the area 22 going down from the base station 20 to the mobile station, a low-power base station radio apparatus (mini-BTS ) Could sufficiently receive the transmission power of the mobile station (MS), but the MS could not receive a downlink signal, so the MS could not issue a soft handoff request. As a result, the transmission power of the MS is B
Eb / No received by TS (ratio of energy Eb per signal bit to noise spectrum density No)
, So for mini BTS reception,
Excessive input signal levels not only increase the power consumption of the MS, but also increase the MS connected to the mini-BTS.
There is a disadvantage that it induces an increase in the transmission level. The reason is that, in the CDMA system, since the transmission frequency (uplink signal frequency) of all MSs is the same, it is an interference wave with respect to the area of the mini-BTS that is not performing communication.

[0010] The present invention performs control so that the uplink communication area and the downlink communication area in communication between the mobile station and the base station are substantially the same, reduces interference waves from other stations, and sets the upper station during soft handoff. It is an object to transmit and receive a control signal between a base station and a base station.

Also, when a mobile station performs soft handoff from another base station to a base station whose uplink communication area is larger than the downlink communication area, the mobile station performs an uplink area of this base station until the soft handoff is performed. The mobile station and the base station, making the uplink communication area and downlink communication area almost the same, and transmitting and receiving control signals between the upper station and the base station during soft handoff. The task is to

[0012]

SUMMARY OF THE INVENTION The present invention comprises a plurality of base stations, a mobile station transmitting and receiving to and from one of the base stations, and a base station control station controlling transmission power of the plurality of base stations. In a code division multiple access (CDMA) system where communication channels are multiplexed on the same frequency, a pilot strength measurement message is transmitted before the mobile station performs a soft handoff when moving to another base station area. Transmitting to the base station, and transmitting the pilot strength measurement message to the other base station, the other base station starts a receiving operation corresponding to the transmission from the mobile station, the base station and the other Of the mobile stations simultaneously receives the transmission from the mobile station, and performs transmission power control on the mobile station via the base station.

Further, the present invention comprises a plurality of base stations, a mobile station transmitting and receiving to and from a base station A in the base stations, and a base station control station for controlling transmission power of the plurality of base stations. In a code division multiple access (CDMA) system that multiplexes communication channels on the same frequency, the mobile station comprises:
R_ADD (maximum threshold), R_DROP (lowest threshold), and R_TD in the received power of the mobile station from the base station A
Receiving a pilot strength measurement message when the received power from the base station A is less than or equal to the R_DROP and exceeds the minimum threshold duration. Transmitting to the base station A, the base station control station causes the base station B in the base station to receive the transmission signal of the mobile station, and transmits the pilot strength measurement message from the mobile station to the base station A and the base station A. The base station B receives the signal, and the base station B starts transmission toward the mobile station.

The present invention also provides a radio communication system comprising a plurality of base stations, a mobile station transmitting and receiving to and from one of the base stations, and a base station control station controlling transmission power of the plurality of base stations. In a code division multiple access (CDMA) system in which a communication channel is multiplexed, a pilot strength measurement message is sent to the base station before the mobile station performs a soft handoff when moving to another base station area. Means for transmitting, and means for transmitting the pilot strength measurement message to the other base station, comprising: receiving means for starting the receiving operation corresponding to the transmission from the mobile station, the other base station, The base station control station outputs an instruction that the base station and the other base station simultaneously receive transmission from the mobile station, and performs transmission power control on the mobile station via the base station. Characterized in that row.

Also, the present invention provides a C-based
The present invention relates to a handoff method for a mobile communication system using a DMA method, and particularly to a high power base station radio apparatus (hereinafter, referred to as a BTS).
Mobile station radio apparatus (hereinafter, referred to as mini-BTS) that moves from the area of
In the area around the boundary between the BTS and the mini-BTS, the transmission power of the MS is controlled by the distant BTS until the soft handoff to the mini-BTS occurs in the area around the boundary between the BTS and the mini-BTS. This has the effect of affecting the uplink reception of the BTS and consequently giving excessive interference to other MSs connected to the area of the mini-BTS, thereby improving transmission of unnecessary power.

The present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention in which the MS is a BTS and a mini-B.
It is an image figure showing signs that it moves between TS. FIG.
, A BTS 10 providing CDMA service, a mini BTS 20, and a mini B
In a mobile communication system constituted by the MS 30 moving toward the TS 20, the MS 30 transmits the BTS 10 until the soft handoff to the mini-BTS 20.
, And control data (hereinafter, power control bit) of the transmission output of the MS 30 transmitted from the MS 30 to control the amount of amplification of the transmission power. For example, if the power control bit is "00", the MS 30 increases the transmission output by 1 dB, and if the power control bit is "11", the MS 30
30 is controlled by a closed loop conforming to IS-95, which lowers the transmission output by 1 dB.

The BTS 10 and the mini-BTS 20 are operated at the same frequency. In the case of the example of FIG.
Since the mini BTS 20 is closer to the MS 30 than 0, the MS 3
When transmitting from 0 to the BTS 10, excessive interference was given to the received signal of the mini-BTS 20. Further, the mini BTS 20 has a small down area, but the up area has an imbalance with little difference in ability between the BTS 10 and the mini BTS 20. The reason is that the downlink area is determined by the downlink transmission power of each BTS, whereas the uplink area is determined by the noise figure characteristic of the receiver.
20 and the BTS 10 are almost the same. As a solution to this problem, there is a method of reducing the uplink area, but this leads to an increase in the transmission power of the MS under the mini-BTS 20 and goes against the low power consumption of the MS.

A feature of the present invention is to solve this problem by using the mini-BTS 20 before the MS 30 performs a soft handoff in accordance with the conventional IS-95.
20 starts the operation of receiving the received power message information from the MS 30, and transmits the uplink signal to the BTS 10 and the mini-BTS 20.
And a transmission power control is performed on the MS 30 via the BTS 10 to prevent unnecessary increase of upstream air interference waves.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
This will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention. FIG. 3 shows a radio area 11 covered by a high-power base station radio apparatus (hereinafter, referred to as a BTS) 10 in which the uplink and downlink areas are balanced (solid line: downlink area, dotted line: uplink). area). FIG. 4 shows a low output base station radio apparatus (hereinafter referred to as a mini BTS) in which the up area is wider than the down area (solid line: down area, dotted line: up area).
2) shows a wireless area 21 covered by the wireless communication device 20.

In FIG. 2, a base station controller (hereinafter, referred to as BSC) 40 as an upper station includes a BTS 10,
A mini BTS 20 is connected. The base station controller BSC402 is a communication center station that controls each base station in an integrated manner, and controls each base station when performing a soft handoff of two or more paths that walks across a plurality of base stations. For example, when performing a soft handoff from one path to two paths, a function of absorbing a message from the current BTS and preparing for reception or transmission of a new BTS is required.
This is the base station controller (BSC).

A mobile station radio apparatus (hereinafter, referred to as MS)
The ratio (Ec / Io) of the desired signal to the interference signal of the pilot signal transmitted from each of the BTS 10 and the mini-BTS 20 is constantly monitored. When the Ec / Io value exceeds a certain threshold value, the MS 30 reports it to the BTS 10.

As shown in FIG. 2, the BSC 40 has a decision section 41 and an instruction transmission section 42 built therein. Judgment unit 41
Performs a soft handoff based on the Ec / Io value of a pilot signal transmitted from the MS 30 via the BTS 10 so as to conform to IS-95 by the American National Standards Institute, or initiates a soft handoff starting only reception. Determine whether to execute. When executing the normal soft handoff based on the result of the determination by the determining unit 41, the instruction transmitting unit 42 instructs the mini-BTS 20 adjacent to the area A of the cover area of the BTS 10 to start transmission and reception, and performs soft reception only for reception. Is executed, the mini BTS 20 adjacent to the area A is instructed to start reception only.

In FIG. 3, an up area 11 shown by a dotted line by the BTS 10 is shown, and a down area shown by a solid line is operated as substantially the same area.
10 achieves balanced transmission and reception.

In FIG. 4, the mini BTS 20 is operated as an unbalanced communication area with an up area 21 indicated by a dotted line and a down area 22 indicated by a solid line.

An internal block diagram of a base station (BTS or mini-BTS) controlled by the BSC 40 shown in FIG. 2 and the MS will be described with reference to FIG. FIG. 9A shows a conceptual block diagram of the BTS 10 and the mini-BTS 20.
A transmission data signal transmitted from the TS or the mini-BTS to the MS is input to the signal spreading section 101, where it is spread in frequency by being multiplied by a PN sequence. The transmission data spread-spectrum-modulated to a predetermined bandwidth is converted into a predetermined format together with the MS transmission power control signal output from the MS transmission power control unit 107 by the transmission format generation unit, and supplied to the signal transmission unit 103. And
In the signal transmitting section 103, the signal is converted into a high-frequency signal in a system frequency band and transmitted from the BTS or mini-BTS antenna to the MS as a BTS or mini-BTS transmission signal. The MS signal transmitted from the MS is a BTS or mini-B
After being received by the TS antenna and frequency-converted by the signal receiving unit 108,
The signal is despread by the N sequence to obtain signal data.

Here, in general, in the CDMA system, in order to solve the near-far problem, the signal from each MS is BT.
Transmission power control is performed to control the transmission power of each MS so that the signal is received at a predetermined power in the S or mini-BTS.
The BTS or mini-BTS target power set in S target power setting section 106 is compared with the received signal level obtained from signal demodulation section 109 to obtain an error signal. This error signal is transmitted as an MS transmission power control signal. The signal is supplied to the format generation unit 102 and transmitted to the MS together with the output signal from the signal spreading unit 101. In this case, the transmission area of the BTS and the transmission area of the mini-BTS have different target power settings by the BTS or mini-BTS target power setting section 106, and there is a difference in transmission power to the MS transmission power control section 107. Transmission using a pilot channel for transmission power control of the MS is also transmitted from each BTS or mini-BTS.

On the other hand, referring to FIG. 9B, in MS transmitting / receiving section 200, transmission data to be transmitted from the MS to the BTS or mini-BTS is spread-modulated by PN sequence in signal spreading section 201 to generate a transmission format. The signal is formed into a predetermined transmission format by the
Is converted into a high-frequency signal in the system frequency band by
It is transmitted from the antenna to the BTS or mini-BTS as an S transmission signal. At this time, the MS transmission power control signal is applied to the signal transmission unit 203 from the MS transmission power information processing unit 206, and the signal transmission unit 203 is transmitted with high-frequency power according to the transmission power control signal. The transmission power control signal optimally controls the transmission power of each MS in the BTS or mini-BTS so that the signal from each MS has a predetermined reception power.

On the other hand, the BTS or mini-BTS transmission signal transmitted from the BTS or mini-BTS is
, And are despread by the signal demodulation unit 209 using the PN sequence, and the received data is reproduced. Also, BT
The MS transmission power control signal included in the S or mini-BTS transmission signal is transmitted from the signal demodulation unit 209 to the MS transmission power information processing unit 2.
06, and controls the transmission power of the signal transmission unit 203. The reception level information corresponding to the reception power detected by the MS transmission power information processing unit 206 is
To the base station controller (B) together with the transmission data signal.
SC).

[Operation of this Embodiment] FIGS. 5 and 6 are flowcharts showing the operation of this embodiment. Also,
FIG. 7 shows a timing chart for a conventional soft handoff based on IS-95. In FIG. 7, T # AD
D is a threshold value of the Ec / Io level of the pilot signal received by the MS 30 from the BTS 10 or the mini-BTS 20. When the threshold value is exceeded, the corresponding BTS 10
Alternatively, the mini-BTS 20 starts a normal soft handoff. T_DROP is when MS 30 is BTS 10 or mini BTS 20
Is a threshold value of the Ec / Io level of the Pilot signal received from the controller. When the value falls below this threshold value, a timer is started, and the level of the Pilot signal falls within the time of the threshold value T_TDROP.
If the value does not exceed T_DROP, the corresponding BTS 10 or mini-BTS 20 stops normal soft handoff.

FIG. 8 is a timing chart for soft handoff according to the present embodiment. In FIG. 8, R # ADD is M
Pi received by S30 from BTS 10 or mini-BTS 20
This is a threshold value of the Ec / Io level of the lot signal. If the threshold value is exceeded, the corresponding BTS 10 or mini-B
The TS 20 starts a soft handoff of reception only. R #
DROP is a threshold value of the Ec / Io level of the pilot signal received by the MS 30 from the BTS 10 or the mini-BTS 20. When the threshold value falls below this threshold value, a timer is started and within a time period of the threshold value R_TDROP, Pilot signal level
If the value does not exceed R # DROP, the corresponding BTS 10 or mini-BTS 20 stops soft handoff for reception only. In FIG. 8, T_ADD and T_DROP are the same as those in FIG.

First, the MS 30 operates in the area 11 of the BTS 10.
1 in FIG. 1 moving from the area to the area 21 of the mini-BTS 20
(Description of FIG. 5).

(Step 1) When the MS 30 is in an idle state of waiting in the area of the BTS 10, the broadcast information transmitted from the BTS 10 is T_AD conforming to IS-95.
D, T # DROP, T # TDROP and new threshold values R # ADD, R # DROP, R # DROP required in this system are received. Threshold R # A
The DD is not related to the conventional threshold values T # ADD, T # DROP, and T # TDROP. If the DD exceeds the threshold value, the MS 20 transmits pilot strength measurement message information (PSMM: Pilot Strength Mea).
surement Message) to the BTS 10.

(Step 2) In the area of the BTS 10, M
S30 is called.

(Step 3) When the MS 30 moves from the area of the BTS 10 toward the area of the mini BTS 20,
When the signal passes through the up area indicated by the dotted line in FIG.
To the pilot strength measurement message information (PSM
M).

(Step 4) The PSMM of the MS 30 is stored in B
The TS 10 receives, transfers, and reports to the BSC 40.

(Step 5) Upon receiving the report, the decision unit 41 of the BSC 40 executes a normal soft handoff,
It is determined whether to start a soft handoff that starts reception only.

(Step 6) When starting a soft handoff in which only reception is started, the instruction transmitting unit 42 requests the mini-BTS 20 designated by R # ADD to start receiving the signal of the MS 20. In this state, the down signal is BT
Only from S10, the uplink signal is received by both BTSs, the BTS 10 and the mini BTS 20.

(Step 7) MS 30 is further mini-BT
When moving in the direction of the area 21 in S20, passing through the solid line in FIG. 4 and entering into the hatched area, the threshold value T_ADD is exceeded, so the pilot strength measurement message information (PSMM)
Send

(Step 8) The PSMM of the MS 30 is stored in B
The TS 10 and the mini-BTS 20 receive and report to the BSC 40.

(Step 9) The instruction transmitting unit 42 determines whether the mini B
It requests the TS 20 to start transmitting the signal of the MS 20. Then, a soft handoff state is set.

(Step 10) On the other hand, in step 5, if the message from MS 30 is a message for executing normal soft handoff, instruction transmitting section 42 transmits and receives the signal of MS 30 to and from mini BTS 20. Request. Then, a soft handoff state is set.

Next, using the flowchart shown in FIG.
The direction of 2 in FIG. 1 that moves to the area 11 of 10 will be described.

(Step 11) The MS 30 is connected to the mini-B in FIG.
When passing through the solid line of TS20 and exiting from the shaded area, it falls below the threshold value T_DROP which triggers transmission stop, and
After the elapse of T_TDROP time, the PSMM is transmitted.

(Step 12) Set PSMM of MS 30 to B
The TS 10 and the mini-BTS 20 receive and report to the BSC 40.

(Step 13) The determination unit 41 determines whether to stop the normal soft handoff or the soft handoff that starts reception only.

(Step 14) To stop the soft handoff that starts reception only, the instruction transmitting unit 42
The transmission stop message is transmitted to S20.

(Step 15) When the MS 30 exits the dotted area of the mini-BTS 20 in FIG. 4, it falls below the R_DROP which triggers the reception stop, and after the R_TDROP time elapses, the PS 30
Send MM.

(Step 16) Set the PSMM of the MS 30 to B
The TS 10 and the mini-BTS 20 receive and report to the BSC 40.

(Step 17) The instruction transmitting unit 42 transmits a reception stop message to the mini-BTS 20.
Then, a one-pass state is set.

(Step 18) On the other hand, if the message from the MS 30 in Step 13 is a message for stopping the normal soft handoff, the instruction transmitting unit 42
Requests the mini-BTS 20 to stop transmitting and receiving signals of the MS 30. Then, a one-pass state is set. In addition, the one-path state means a terminal (MS) and a base station (BTS).
Are in a state of one-to-one wireless connection.

In the above embodiment, mainly the area of the high power base station radio (BTS), the area of the adjacent low power base station radio (mini BTS), and the software of the mobile station radio (MS) there. Although the handoff has been described, the soft handoff between the areas where the high power base station radio (BTS) is adjacent and the soft handoff between the areas where the low power base station radio (mini BTS) is adjacent are also applicable. , Applicable. In this case, the base station controller (BSC) instructing the soft handoff causes each BTS or mini-BTS to smoothly execute the soft handoff of the mobile station radio apparatus (MS).

[0053]

According to the soft handoff method of the present invention, the reception of the mini-BTS and the reception of the BTS are used until the MS connected to the BTS performs the soft handoff with the mini-BTS. Because the control amount is determined,
The transmission power of the MS does not interfere with the reception of the neighboring mini-BTS. As a result, not only prevent unnecessary increase in transmission power of other MSs connected to the mini-BTS area, but also reduce interference waves to other stations, thereby maintaining high communication quality with other MSs. it can.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment in which a MS is a BTS and a mini BT.
It is an image figure showing signs that it moves between S.

FIG. 2 is a block diagram of one embodiment of the present invention.

FIG. 3 is an area diagram of a BTS in which uplink and downlink are balanced.

FIG. 4 BT in which the up area is sufficiently larger than the down area
It is an area figure of S.

FIG. 5 is a flowchart (1) showing an operation of a soft handoff in the embodiment.

FIG. 6 is a flowchart (2) showing an operation of soft handoff in the embodiment.

FIG. 7 is a timing chart of soft handoff according to IS-95.

FIG. 8 is a timing diagram of soft handoff according to the present invention.

FIG. 9 is a schematic block diagram of a BTS and an MS according to an embodiment of the present invention.

[Explanation of symbols]

10 CDMA Radio Base Station (BTS) 11 Area of CDMA Radio Base Station (BTS) 20 Mini CDMA Radio Base Station (Mini BTS) 21 Reception Area of Mini CDMA Radio Base Station (Mini BTS) 22 Mini CDMA Radio Base Transmission area of station device (mini-BTS) 30 mobile terminal station (MS) 40 radio base station controller (BSC) 41 determination unit 42 instruction transmission unit

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[Procedure amendment]

[Submission date] November 8, 1999 (1999.11.
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

[0012]

SUMMARY OF THE INVENTION The present invention comprises a plurality of base stations, a mobile station transmitting and receiving to and from one of the base stations, and a base station control station controlling transmission power of the plurality of base stations. In a code division multiple access (CDMA) system where communication channels are multiplexed on the same frequency, the mobile station receives a signal before performing a soft handoff when the mobile station moves to the area of another base station. Pie from inside base station
Transmits a pilot strength measurement message to the base station based on a result of measuring the lot signal strength, and and transmitting the pilot strength measurement message to the other base station, the other base stations said from said mobile station Pilot strength measurement
Starts reception operation corresponding to the transmission of the constant message, the base station and the other base station is the pie from the mobile station
The transmission of the lot strength measurement message is simultaneously received, and transmission power control is performed on the mobile station via the base station.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

The present invention also provides a radio communication system comprising a plurality of base stations, a mobile station transmitting and receiving to and from one of the base stations, and a base station control station controlling transmission power of the plurality of base stations. In a code division multiple access (CDMA) system where communication channels are multiplexed to a mobile station , the mobile station may receive a base station before performing a soft handoff when moving to an area of another base station. Pilot letter from
Means for transmitting a pilot strength measurement message to the base station based on the result of measuring the signal strength, and means for transmitting the pilot strength measurement message to the other base station, wherein the other base station is The base station control station further includes a receiving unit that starts a reception operation corresponding to transmission from a mobile station, and the base station control station outputs an instruction that the base station and the other base station simultaneously receive transmission from the mobile station, Transmission power control is performed on the mobile station via a base station.

Claims (6)

[Claims] 1. A communication channel having the same frequency comprising a plurality of base stations, a mobile station transmitting and receiving to and from one of the base stations, and a base station control station controlling transmission power of the plurality of base stations. A handoff method for a multiplexed code division multiple access (CDMA) system, comprising: transmitting a pilot strength measurement message to the base station before performing a soft handoff when the mobile station moves to an area of another base station. Transmitting the pilot strength measurement message to the other base station, the other base station starts a reception operation corresponding to the transmission from the mobile station, and the base station and the other base station CDM receiving transmissions from mobile stations simultaneously and performing transmission power control on said mobile stations via said base station.
Method A for handing off the system. 2. The handoff method for a CDMA system according to claim 1, wherein after the mobile station transmits the pilot strength measurement message to the base station, the mobile station moves out of the area of the other base station. In this case, the other base station receives a transmission stop message, the mobile station transmits the pilot strength measurement message again, and the other base station receives the reception stop message. Handoff method. 3. The same frequency comprising a plurality of base stations, a mobile station transmitting and receiving to and from a base station A in the base stations, and a base station control station controlling transmission power of the plurality of base stations. Code division multiple access (CDM) multiplexing communication channels
A) In the system, the mobile station receives, from the base station A, a maximum threshold value, a minimum threshold value, and a minimum threshold time duration among the reception powers of the mobile station, and the reception power from the base station A. Sends a pilot strength measurement message to the base station A when is less than or equal to the minimum threshold and exceeds the maximum threshold for the minimum threshold duration, wherein the base station control station Let the base station B receive the transmission signal of the mobile station, make the base station A and the base station B receive the pilot strength measurement message from the mobile station, and send the base station B to the mobile station. CDMA system handoff method. 4. The handoff method for a CDMA system according to claim 3, wherein a transmission / reception area of said base station A is larger than a transmission / reception area of said base station B. 5. The handoff method for a CDMA system according to claim 3, wherein the mobile station receives a maximum threshold value, a minimum threshold value, and a minimum threshold value from among the received power of the mobile station from the base station A. A handoff method for a CDMA system, comprising receiving a duration and a maximum threshold, a minimum threshold, and a minimum threshold duration during transmission power. 6. A communication channel for the same frequency comprising a plurality of base stations, a mobile station transmitting and receiving to and from one of the base stations, and a base station control station controlling transmission power of the plurality of base stations. Means for transmitting a pilot strength measurement message to the base station in a multiplexed code division multiple access (CDMA) system before performing a soft handoff when the mobile station moves to an area of another base station. Means for transmitting the pilot strength measurement message to the another base station, and receiving means for starting the receiving operation corresponding to the transmission from the mobile station, the base station control The station outputs an instruction that the base station and the other base station simultaneously receive transmission from the mobile station, and performs transmission power control on the mobile station via the base station. Characterized CDMA system.