JP2002112306A - CDMA wireless communication system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention makes it possible to efficiently perform a spreading code detection process of a mobile device, and enables a handover procedure in consideration of a moving direction of the mobile device, thereby reducing the frequency of handover. A wireless communication system is provided. SOLUTION: The mobile station calculates a moving speed and a moving direction of the mobile station from position information of a neighboring wireless base station broadcast from the wireless base station, and efficiently broadcasts a neighboring cell using a known spreading code. Information can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA radio communication system for switching radio base station cells as a mobile station moves.

[0002]

2. Description of the Related Art In a wireless communication system employing a conventional CDMA system, when a mobile station arrives near the boundary of a coverage area of a wireless base station, the network deteriorates in reception quality of radio waves transmitted from the mobile station. And notifies the mobile device with a message to measure the downlink physical channel transmitted from the peripheral wireless base station.

[0003] Upon receiving this message, the mobile station newly assigns a finger to a plurality of adjacent radio base stations and starts measuring radio waves transmitted from each radio base station. The mobile station, when measuring the one that satisfies the report reference value notified from the network, selects the base station suitable for the mobile station on the network side by transmitting the measurement report to the base station, and performs a handover procedure. To start.

At this time, since the position information of the mobile station is not considered with respect to the radio base station selected by the network, the measurement of the transmission radio wave from the radio base station located far from the direction in which the mobile station moves in the future. If the value is temporarily high, or if the mobile station moves at high speed in an area where the coverage area of each wireless base station is relatively narrow, depending on the method of selecting the wireless base station assigned to the mobile station, The frequency of performing the handover procedure increases, and the handover efficiency is poor, so that loads are imposed on the mobile device and the network.

[0005]

As described above, the conventional CD
In the MA system wireless communication system, the mobile station reaches the vicinity of the boundary of the coverage area of the wireless base station and the reception quality of the radio wave transmitted by the mobile station on the network side deteriorates. In order to perform this, the mobile station is caused to measure the radio wave transmitted from the peripheral base station, and to report the measured value serving as the criterion. Upon receiving the measurement report from the mobile device, the network starts a procedure to perform a handover to a radio base station corresponding to a higher measurement value for the transmission radio wave from each radio base station reported at that time. Since the moving direction of the handset is not taken into consideration as a criterion for selecting a handover destination radio base station, the frequency of handover may increase. Further, when the mobile station acquires the broadcast information from a new wireless base station, it is necessary to first perform a process of detecting a spreading code of the wireless base station.

The present invention makes it possible to efficiently perform a spreading code detection process of a mobile device in the above-described situation, and to enable a handover procedure taking the moving direction of the mobile device into consideration, thereby reducing the frequency of handover. The purpose is to make

[0007]

To achieve the above object, according to the present invention, there is provided a CDMA wireless communication system in which a base station and a mobile station communicate via a wireless line. The notifying means for notifying the mobile station of the latitude and longitude information and the spreading code where the own station and other base stations are located, and information on the base station that performs handover from the past moving position of the mobile station to the mobile station. Notifying means for notifying, the mobile station receives and stores the latitude and longitude information and the spreading code broadcast from the base station, storage means, and measuring means for measuring the position and moving speed of the own station, ,
Selecting means for selecting a handover destination base station based on information on the base station notified by the notifying means, latitude / longitude information and spreading code stored in the storage means, and a position and moving speed measured by the measuring means; It is characterized by having.

According to a second aspect of the present invention, in the CDMA wireless communication system according to the first aspect of the present invention, the measuring unit transmits the signal from a base station of a cell to which the mobile station belongs and another base station. It is characterized in that the electric field strength of the radio wave to be measured is periodically measured, the position of the mobile station is measured from the fluctuation value due to the time and the positional relationship with the base station, and the measured time is stored in the storage means.

According to a third aspect of the present invention, in the CDMA wireless communication system according to the second aspect of the present invention, the measuring means includes a plurality of combinations of the measured position of the mobile station and the measured time. It is characterized by measuring the moving speed of the mobile device.

According to a fourth aspect of the present invention, in the CDMA wireless communication system according to the first aspect of the present invention, the selecting means includes a selector which is in proportion to the measured moving speed of the mobile station. The optimal position for selecting the handover destination base station is determined, and the handover destination base station is selected by the mobile device in order from the base station located closest to the optimal position in the predicted route obtained from the position and the moving direction of the mobile station. And

According to a fifth aspect of the present invention, in the CDMA wireless communication system according to the first aspect of the present invention, the notifying means notifies the latitude and longitude and the spreading code of the own station and the adjacent base station. It is characterized by doing.

In order to achieve the above object, according to a sixth aspect of the present invention, in the CDMA wireless communication system according to the first aspect, the selection means holds information on a route to which the mobile station has moved in the past, When a mobile station needs to perform a handover, a handover procedure is performed for a base station located at an optimum position in the moving direction of the mobile station.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a wireless communication system according to the present invention.
1 shows a first embodiment.

Each BS number indicates the number of a radio base station covering each cell. A mobile station located in a cell covered by BS2 in FIG. 1 passes through route 1 and travels in the direction of route 2.

Next, the configuration of the mobile device is shown in FIG.

In FIG. 2, 1-1 is a moving speed calculator,
1-2 is a position calculation unit, 1-3 is a memory, 1-4 is a clock module, 1-5 is a main control unit, 1-6 is an RF unit, 1-7.
Denotes a wireless control unit, and 1-8 denotes a wireless base station selecting unit. Each wireless base station that configures the wireless communication system reports the latitude, longitude, and spreading code of neighboring wireless base stations as broadcast information to the mobile device.

FIG. 3 shows the latitude E, longitude N, and spreading code Code of the neighboring radio base station broadcast by the BS2.

In the radio communication system shown in FIG. 1, the mobile station receives the broadcast information broadcast from the communicating radio base station and stores the information in the radio base station information table in the memory 1-3 of the mobile station. The base station identification number, latitude E and longitude N, and spreading code are held as shown in FIG.

Then, as shown in FIG. 5, for example, radio waves transmitted from the radio base station to which the mobile station belongs and a plurality of adjacent radio base stations are received at a constant period Ti using a known spreading code. The received electric field strength is measured and stored in the memory 1-3 together with the measurement time as shown in FIG.

Subsequently, from the relationship between the variation ratio with each received electric field strength measured at the previous time and the latitude and longitude of each base station, 1-
The position calculation unit 2 calculates the current position of the mobile device, and stores the combination of the position of the mobile device and the time at which the position was measured in the mobile device position information table as shown in FIG.

The information held in the above-mentioned mobile station position information table needs to be held several times in the past. Mobile device is BS
When reaching the vicinity of the cell boundary covered by 2, the mobile unit
Senses that the radio wave has deteriorated, and
A message is transmitted to the mobile device via S2 to measure the transmission radio waves from the neighboring cells. When the mobile device receives the signal, it measures the received radio waves from the neighboring cells. Prior to that, first, the moving speed calculation unit 1-1 moves from the past several measurement positions and measurement times on the mobile device position information table. Calculate the average speed of the machine.

Next, the radio base station selecting section 1-8 calculates the optimum position of the radio base station performing the handover based on the moving speed based on the current position of the mobile device, and finds the optimum position closest to the moving direction and the optimum distance. When the priorities are determined as the handover destination base stations in order from the wireless base station located at, and the priority is held, the result is as shown in FIG.

When the priorities are determined, the mobile station starts measuring the received radio wave from the peripheral base station designated by the network and holds it as the received radio wave measurement value 1 in FIG.

At this time, if the value satisfies the reference value specified by the network, the value is reported to the network, and if not, further measurement is performed. Here, there are two types of usage of the priority calculated for each wireless base station.

One is to perform only the measurement with the highest priority when measuring, and the other is to perform the measurement.
Measure as much as possible, but report only the top ones when reporting. Since these determinations relate to the security of communication, they may be determined on the network side. FIG. 9 shows a flowchart of the processing up to this point (the description is omitted because it has been described above).

On the network side, based on the neighboring cell information reported from the mobile station, a judgment is made based on the higher order of the measured values, and if the capability of the BS5 is determined and a handover is possible, a handover procedure is performed to perform a handover to the BS5. To start.

In the first embodiment, BS2
By listening to the neighboring cell information broadcast from the neighboring cell, the mobile device connected to the terminal further knows the latitude / longitude information and the spreading code of the neighboring base station.

That is, by listening to the neighboring cell information broadcast from the BS5, it is also possible to obtain the neighboring adjacent base station information of the BS5 broadcast by the BS5, and the spreading codes of the BS6, BS7 and BS8 which cannot be heard at this time. Will also be known.

Therefore, when being connected to BS2,
When detecting broadcast information of BS6, BS7, and BS8, it is not necessary to newly perform a spreading code detection process, and broadcast information can be extracted by immediately applying the code. Therefore, in the first embodiment, this property can be used when the mobile device moves at high speed or when the mobile device moves in an area where the base station interval is small.

FIG. 10 shows an example in which the mobile unit moves at high speed. The operation of the mobile unit is the same as that of the first embodiment. However, when the mobile device moves at a high speed, it is determined to perform a handover to a radio base station located farther from the mobile device than when moving at a low speed. When the mobile station arrives near the boundary of BS2 and the radio base station detects the deterioration of the radio wave received from the mobile station, the network moves to measure the radio waves transmitted from the neighboring cells via BS2 as in the previous example. A message to the device.

Upon receiving this message, the mobile station calculates the mobile station speed in the same manner as in the previous example, and determines the priority of the handover destination base station candidate. At that time, BS6, BS7,
If the radio wave from BS8 can be received, the radio base station selecting unit 1-8 determines the priority order including the BS6, BS7, and BS8 that can currently receive the transmission radio wave from the magnitude of the mobile station speed, and Perform strength measurement. When the mobile device is moving at a high speed, it is possible to suppress the power consumption by stopping the actual measurement for the wireless base station located behind in the moving direction of the mobile device. Subsequent processing is the same as in the previous example. FIG. 11 shows the processing results so far.

As described above, the mobile station uses the latitude and longitude of the neighboring base station notified from the radio base station to determine the position of the mobile station from the fluctuation value of the electric field strength of the radio wave transmitted from the adjacent radio base station. The mobile device speed can be known from the mobile device position information measured and measured in the past. In addition, since the mobile station reports a processing result so that the network side selects the most suitable handover destination radio base station on the side of the mobile station from its own moving direction, the network side reports the resource status of the handover destination radio base station. Only by examining, the handover frequency can be kept low for both parties, and the reported latitude / longitude information is effective. The above is an example until the mobile device selects a handover destination radio base station led by the mobile device.

Next, FIG. 12 shows a second embodiment of the handover destination radio base station selection processing led by the network side.

In FIG. 12, the mobile station has passed route 1 in the past,
This indicates that the vehicle is continuously moving at a high speed in the direction of the current route 2. When the network side takes the initiative and selects a handover destination radio base station of the mobile station, the network side has a table for holding the past movement path of the mobile station.

When the mobile device moves in the order of BS13, BS12 and BS1 according to the route 1, the network holds the mobile device as MS1 as shown in FIG. Each time is the time when the mobile device performed the handover.

When the mobile station moves near the cell boundary covered by the connected BS1, the network reports the measurement result of the transmitted radio wave from the neighboring cell via the BS1 as in the first embodiment. Notify the mobile device of the message.

When the mobile device receives this message, it understands from the information elements added to the message that the current handover procedure is network-driven, and starts measuring the transmitted radio waves from the neighboring cells.

In the case of the network-driven type, the mobile station immediately starts measuring radio waves from the peripheral base station indicated by the message, and if any of the mobile stations satisfies the specified reference value,
Report to network.

At this time, as in the first embodiment, whether the base station to report is selected only in consideration of the moving direction of the mobile station, or whether the mobile station reports all the audible sounds of the mobile station, a message transmitted by the network. As an information element.

If the base station to be reported is only the one considering the moving direction of the mobile station, the mobile station must calculate the moving speed of the mobile station after receiving the message, as in the first embodiment. .

The network that has received the measurement report message from the mobile station selects a handover radio base station from the past movement history of the MS 1 held by the network.
In this case, the mobile station moves almost linearly to BS2, BS3, B
Since the mobile terminal has moved at a high speed in S5, a handover procedure is started to perform a handover to the BS5.

Further, in the second embodiment, the moving speed of the mobile device may be included as information that the mobile device notifies the network. In this case, on the network side receiving this, the past movement history of the MS 1 held by the network, the moving speed of the mobile device, and the measurement report of the mobile device are used, and
It is possible to select the handover destination wireless base station in S1.

As described above, the mobile station calculates the moving speed and moving direction of the mobile station based on the position information of the neighboring radio base stations broadcast from the radio base station, and efficiently uses the known spreading code to efficiently calculate the surroundings. Broadcast information of a cell can be obtained. Further, the network can determine the next handover destination radio base station of the mobile station from the past movement history of the mobile station using the information reported from the mobile station, and has an effect of reducing the handover frequency.

[0045]

As described above, according to the present invention, the mobile station receives the latitude / longitude and the spread code of the peripheral radio base station broadcast by each radio base station, and uses the spread code of the peripheral base station that has not been detected yet. This makes it possible to reduce the load on the mobile device due to performing the spreading code detection processing.
In addition, by using the broadcast information to calculate the position and speed of the mobile device, the mobile device can use the base station to receive the radio signal in the measurement report of the radio wave transmitted from the peripheral wireless base station for the handover. It is possible to select a station,
Further, by selecting the radio base station so that the mobile device performs the handover effectively, it is possible to reduce the frequency of the handover.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of the present embodiment.

FIG. 2 is a configuration diagram of a mobile device according to the present embodiment.

FIG. 3 is a diagram showing information held by a wireless base station according to the present embodiment.

FIG. 4 is a diagram showing base station information held by the mobile device of the present invention in the present embodiment.

FIG. 5 is a reference diagram for measuring the position of the mobile device in the present embodiment.

FIG. 6 is a diagram showing received electric field information held by the mobile device according to the present embodiment.

FIG. 7 is a diagram illustrating position information of the mobile device held by the mobile device according to the present embodiment.

FIG. 8 is a diagram showing base station information held by the mobile station in the first embodiment of the present embodiment.

FIG. 9 is an operation flowchart of the first embodiment in the present embodiment.

FIG. 10 is a system configuration diagram showing a first embodiment of the present embodiment.

FIG. 11 is a diagram showing base station information held by the mobile device according to the first embodiment in the present embodiment.

FIG. 12 is a system configuration diagram showing a second embodiment according to the present embodiment.

FIG. 13 is a diagram showing mobile device information held by the network according to the second embodiment in the present embodiment.

[Explanation of symbols]

1-1: moving speed calculator, 1-2: position calculator, 1-3: memory, 1-4: clock module, 1-5: main controller, 1- 6 ... RF part, 1-
7 ... Wireless control unit, 1-8 ... Wireless base station selecting unit

Claims (6)

[Claims] 1. A CDMA wireless communication system in which a base station and a mobile station communicate via a wireless line, wherein the base station moves latitude / longitude information and a spreading code where its own station and other base stations are located. And a notifying unit for notifying the mobile station of information on a base station that performs a handover from a past movement position of the mobile station, the mobile station being notified from the base station. Storage means for receiving and storing the latitude and longitude information and the spreading code, measuring means for measuring the position and moving speed of the own station, information on the base station notified by the notifying means, and latitude stored by the storing means A CDMA system comprising a selection unit for selecting a handover destination base station based on longitude information and a spreading code, and a position and a moving speed measured by the measurement unit. Line communication system. 2. The measuring means periodically measures the electric field strengths of radio waves transmitted from a base station of a cell to which the mobile station belongs and another base station, and obtains a time-varying value and a positional relationship between the base station and the base station. 2. The CDMA system according to claim 1, wherein the position of the mobile station is measured, and the measured time is stored in a storage unit together with the measured time.
System wireless communication system. 3. The measuring means comprises: a measured position of a mobile station;
3. The CDMA wireless communication system according to claim 2, wherein the moving speed of the mobile device is measured from a plurality of combinations of the measured times. 4. The selection means determines an optimum position for selecting a handover destination base station in proportion to the measured moving speed of the mobile station, and determines an optimum position on an estimated route obtained from the position and the moving direction of the mobile station. 2. The CDMA wireless communication system according to claim 1, wherein the handover destination base station is selected in order from the base station located closest to the position in a mobile device initiative. 5. The notifying means notifies the latitude and longitude and the spreading code of the own station and the adjacent base station.
DMA wireless communication system. 6. The selection means retains information on the route to which the mobile station has moved in the past, and when the mobile station needs to perform a handover, the base station is located at an optimum position in the moving direction of the mobile station. 2. The CDMA wireless communication system according to claim 1, wherein a handover procedure is performed on the CDMA wireless communication system.