JP2001268619A - Mobile radio terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption for selecting a radio base station at hand-over time by quickly detecting a radio base station as a hand-over destination. SOLUTION: Communication histories wherein base stations which are already connected before a hand-over and base stations after the hand-over are made to correspond to each other are generated by communication sessions in a history generation table storage area 200b and at the end of a communication session, the communication history generated here is recorded in a hand-over history recording area 200a; when a hand-over needs to be made, base stations as hand-over destinations are listed among the base stations before the hand-over in the order of their frequencies and generated in a candidate base station list storage area 200c; and whether or not a hand-over to the base stations in the list is possible is verified one by one in the order of the frequencies and the hand-over is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code
The present invention relates to a mobile radio terminal used in a mobile radio communication system such as a mobile phone system or a mobile phone system adopting a Division Multiple Access (Division Multiple Access) system.

[0002]

2. Description of the Related Art As is well known, CDMA (Code Divisio
The mobile radio terminal device adopting the “n Multiple Access” system includes a plurality of receivers called fingers, and performs communication through a plurality of paths using the plurality of receivers. Therefore, communication is performed using only one path. It has the advantage that it not only has better communication quality than other communication methods, but can also cope with high-speed movement.

If the reception quality of any of the fingers drops below a predetermined level due to movement of the mobile radio terminal, handover processing for connecting the finger whose reception quality has dropped to a new radio base station is performed. Done.

In this handover process, a list of nearby radio base stations which are candidates for a handover is notified from a connected radio base station, and pilot signals from the radio base stations in the list are sequentially received. A radio base station having a high reception strength is assigned to the finger.

However, in such a conventional mobile radio terminal device, every time a handover process is required,
Since all the radio base stations in the notified list are verified, unnecessary processing such as verification for radio base stations that are not connected as a result is inevitable, and a handover destination radio base station is selected. Not only takes time, but also consumes power unnecessarily.

[0006] Since the mobile radio terminal of the CDMA system has a plurality of receivers as described above, power consumption is basically large, and reduction of power consumption is a major problem. However, since the handover process is frequently performed, the above-mentioned problem becomes more remarkable. For this reason, for a CDMA system that is good at high-speed movement, improving power consumption during high-speed movement has been a major problem.

[0007]

In a conventional mobile radio terminal of the CDMA system, there is a problem that the selection process of the radio base station at the time of handover is wasteful, takes time, and consumes power unnecessarily. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and efficiently and quickly detects a wireless base station of a handover destination, and reduces power consumption for selecting a wireless base station at the time of handover. Possible CDM
An object of the present invention is to provide a mobile radio terminal of the A type.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a mobile radio terminal wirelessly connected by a CDMA method to a plurality of radio base stations connectable to a communication network. A communication history storage means for storing identification information of the communicating base station and a communication order of the communicated base station, and when a handover is required, in an order based on the information stored in the communication history storage means, Wireless base station searching means for searching for a wireless base station capable of handover, and a wireless base station for wirelessly connecting to the detected wireless base station when the wireless base station capable of handover is detected by the wireless base station searching means. And connecting means.

In the mobile radio terminal having the above configuration, for each communication session, the identification information of the communicating base station and the communication order of the communicating base station are recorded in the communication history storage means.
When handover is required, a search is made for a handover-capable radio base station in an order based on the information stored in the communication history storage means. Wireless connection to the established wireless base station.

[0011] Therefore, according to the mobile radio terminal having the above configuration, the handover from the radio base station before the handover is performed many times, and the handover is verified from the radio base station having a high possibility as a destination. It is possible to omit the verification process for the wireless base station that does not move, efficiently detect the wireless base station of the handover destination quickly and suitably, and also suitable for high-speed movement, and reduce the power consumption for the wireless base station selection process at the time of handover. be able to.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a CDMA mobile radio terminal apparatus according to an embodiment of the present invention. In particular, here, a description will be given mainly of a receiving system according to the present invention.

The transmitting device 12 modulates transmission data such as digitized voice and data by a digital modulation method such as PSK modulation, spreads the modulated data using a spreading code, and generates a wideband base signal. Convert to band signal.

The transmitting apparatus 12 up-converts the spread baseband signal into a radio frequency signal and inputs the signal to the antenna 10 through the duplexer 11. The input radio frequency signal is transmitted to the antenna 10
It is radiated further into space and transmitted to a base station (not shown).

On the other hand, the radio signal transmitted from the base station is received by the antenna 10 and input to the receiving device 13 through the duplexer 11. The receiving device 13 is a wireless circuit 1
4, an intermediate frequency circuit 15, and a rake (rake) receiver 16.

In the radio circuit 14, the radio signal received from the duplexer 11 is input to the attenuator 14a, where it is attenuated by a predetermined amount. The signal that has passed through the attenuator 14a is amplified to a predetermined level by an amplifier 14b, then mixed with a local oscillation signal generated by a frequency synthesizer 14d by a mixer 14c, and down-converted to an intermediate frequency.

The signal down-converted to the intermediate frequency is input to an intermediate frequency circuit 15 and amplified to a predetermined level by an amplifier 15a. The result of the amplification is input to a band-pass filter (BPF) 15b, from which only a desired band passes and input to a mixer 15c.

In the mixer 15c, the bandpass filter 1
The signal that has passed through 5b is mixed with the signal generated by frequency synthesizer 15d, and is converted into a baseband signal. This baseband signal is converted into a digital signal by an A / D converter (A / D) 15e, and Ra
Input to the ke receiver 16.

The rake receiver 16 includes a searcher 16a
, Fingers 16b, 16c, 16d, and a symbol combiner 16e. The digital signal is input to the searcher 16a and the fingers 16b, 16c, 16d, respectively.

The searcher 16a detects signals arriving on the plurality of paths from the base station to the own terminal, that is, so-called multipaths, and despreads each path using the same spreading code as that used for spreading on the transmitting side. I do.

Then, the searcher 16a calculates Ec / Io for each despread result, and also calculates the delay time difference (delay profile). Then, the reception timing (despread timing) of each path is obtained based on the delay profile, and the obtained timing is assigned to the fingers 16b, 16c, and 16d in descending order of Ec / Io.

The fingers 16b, 16c and 16d despread the digital signal at the despread timing assigned by the searcher 16a using the same spreading code used for spreading on the transmitting side.

The symbol synthesizer 16e includes a finger 16
The multipath components despread by b, 16c, and 16d are symbol-synthesized in consideration of the despread timing assigned to each of the fingers 16b, 16c, and 16d.

The signal that has been symbol-synthesized by the symbol synthesizer 16e is subjected to demodulation processing corresponding to digital modulation on the transmission side in a subsequent signal processing unit 17, and the received data is reproduced.

The control unit 100 includes a CPU, a ROM and an R
AM, etc., wherein the CPU is the RO
In accordance with a control program and control data stored in M, each unit of the mobile wireless terminal device is controlled in an integrated manner, and for example, control relating to handover is performed.

In the control related to the handover, the control unit 100 monitors Ec / Io of each path received by the fingers 16b, 16c, and 16d to determine whether the handover condition is satisfied, and to determine whether the handover condition is satisfied. When the need arises, the searcher 16a controls so as to search for a new path in the order based on the information stored in the handover history storage area 200a of the storage unit 200.

The storage unit 200 is a recording medium such as a ROM and a RAM, and has an area for storing various information such as telephone directory data which can be arbitrarily recorded by a user, and also has an area for storing the handover history. 200a,
It has a history creation table storage area 200b.

The handover history storage area 200a includes:
Information is read and written under the control of the control unit 100, and the information recorded here is, as shown in FIG. 2, communication history data recorded by a base station connected by handover in accordance with the order of handover for each communication session. And valid flag data indicating whether each of these data is valid (refer to at the time of handover).
The user can arbitrarily set validity / invalidity of the validity flag data through a key input unit (not shown).

The history creation table storage area 200b stores
Under the control of the control unit 100, in the storage area used for creating the communication history data, as shown in FIG. 3, the base stations that have communicated in the current communication are temporarily recorded in the communication order, and the communication is terminated. Sometimes, the recorded information is stored in the handover history storage area 20 as communication history data.
0a is recorded.

The candidate base station list storage area 200c includes:
This is an area for storing a candidate base station list indicating candidates for a handover destination base station as shown in FIG. 4, which is created when the control unit 100 performs a process of selecting a handover destination base station.

Although not shown in FIG. 1, as a component of the present apparatus, there is a power supply section which supplies power for operating the above-described sections and has a battery which can be repeatedly charged and discharged.

Next, the operation of the mobile radio terminal having the above configuration at the time of handover will be described. FIG. 5 is a flowchart showing a connection base station selection process performed by the control unit 100 when the handover condition is satisfied.

Certain fingers (16b, 16c, 16d)
When the need for handover arises, for example, when the Ec / Io of the path received at the node falls below a predetermined level, the processing shown in FIG. 5 is started.

First, in step 5a, referring to the handover history storage area 200a, communication history data describing a base station (hereinafter, referred to as a pre-movement base station) from which a signal received by the finger is transmitted is described. Is read, and the routine goes to Step 5b. Note that the communication history data referred to at this time is only the communication history data for which the validity is set by the validity flag data.

In step 5b, based on the communication history data read in step 5a, as shown in FIG. 4, the base station connected by handover from the base station before movement (hereinafter referred to as the base station after movement) Base station)
A candidate base station list is tabulated in descending order of the number, and the process proceeds to step 5c. This candidate base station list is created in the candidate base station list storage area 200c.

In step 5c, the base station with the largest number of times is selected from among the base stations that have not been excluded (set to OFF) in the candidate base station list.
Move to d.

In step 5d, reception of a pilot signal from the base station is attempted using the spreading code corresponding to the base station selected in step 5c, and it is determined whether or not the base station is suitable as a handover destination base station. Here, when it is appropriate as the handover destination base station, the process proceeds to step 5e, and when it is not appropriate, the process proceeds to step 5f.

In step 5e, in order to perform handover to the selected base station, various settings are made so that the finger receives a message signal from the selected base station, and the process proceeds to step 5i.

In step 5f, the exclusion setting is performed for the selected base station in the candidate base station list in the candidate base station list storage area 200c (ON setting), and the process proceeds to step 5g.

In step 5g, it is determined whether the candidate base station list in the candidate base station list storage area 200c includes any base station that has not been excluded (set to OFF). The process proceeds to verify the remaining base stations. If all the base stations are excluded, the process proceeds to step 5h.

In step 5h, handover is possible from the base stations which are notified from the pre-movement base station as candidates for the handover destination, except for the base stations in the initial candidate base station list created in step 5b. The base station is detected, handover is performed to the detected base station, and the process proceeds to step 5i.

In step 5i, the identification data of the base station that has become the handover destination, that is, the base station that has become the post-movement base station, is recorded in the history creation table storage area 200b as the base station connected in this communication. The process ends.

Next, the operation when the mobile radio terminal device moves as shown in FIGS. 6 and 7 will be described. In the figure, BSn indicates a base station, and a circle surrounding the base station indicates a wireless zone in which each base station can communicate.

In the figure, a route indicated by a solid line is a route that the user moves in the current communication, and a route indicated by a broken line is a route based on the communication history of the user's movement in the past communication, and the handover history Storage area 2
00a.

First, in FIG. 6, when the mobile radio terminal device moves and moves from the radio zone of BS1 to the radio zone of BS2, a finger that cannot communicate with BS1 is generated. Are performed.

According to the candidate base station list created by the above processing, the handover to BS2 is more frequently performed than the communication history, so that the reception of the pilot signal from BS2 is performed with priority over other base stations.

As a result, since a pilot signal can be received from BS2, a handover to BS2 is performed, and a history creation table storage area 200b is stored after BS1 in BS2.
The identification data of BS2 is recorded.

Next, as shown in FIG.
When the mobile terminal 5 is moved, a finger that cannot communicate with the base station BS2 is generated, and the processing shown in FIG. 5 is performed, and a new candidate base station list is created.

According to the candidate base station list created by the above processing, the handover to BS 4 is more frequently performed than the communication history, so that the reception of the pilot signal from BS 4 is performed with priority over other base stations.

However, this time, since the user moves to BS5 and cannot receive a pilot signal from BS4, the same processing is performed for BS5 in the next order. As a result, a pilot signal from BS5 can be received, handover to BS5 is performed, and BS2 is stored in history creation table storage area 200b following BS2.
The identification data of S5 is recorded.

As described above, in the mobile radio terminal having the above configuration, the connected base station and the base station after the handover are stored in association with each other before the handover, and when the handover becomes necessary, Then, it is verified that the handover is possible in the order from the base station before the handover to the base station with the largest number of handovers, and the handover is performed.

Therefore, according to the mobile radio terminal having the above configuration, the number of times of handover from the base station before the handover is large depending on the use state of the user, and the verification of the handover from the base station having a high possibility as the destination is performed. Therefore, the verification process for the base station that does not move can be omitted, the wireless base station of the handover destination can be efficiently and quickly detected and suitable for high-speed movement, and the selection process of the wireless base station at the time of handover can be performed. Power consumption can be reduced.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the candidate base station list created in step 5b is not limited to the number of handover destinations, and if it becomes a handover destination at least once, it is listed in the above list. Instead of, for example, a limit may be imposed on the number of handover destinations, or up to a predetermined order with a large number of times may be set as an object to be listed as a candidate base station list. It goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0054]

As described above, according to the present invention, in each communication session, the identification information of the communicating base station and the communication order of the communicating base station are recorded in the communication history storage means, and the handover of the handover is performed. When the need arises, in a sequence based on the information stored in the communication history storage means, a search is made for a handover-capable radio base station, and when a handover-capable radio base station is detected, the detected radio base station is detected. It connects to the base station wirelessly.

In other words, according to the present invention, handover is performed from a radio base station which has a large number of handovers from the radio base station before the handover and has a high possibility as a destination.

Therefore, according to the present invention, it is possible to omit the verification process for the radio base station that does not move, detect the radio base station of the handover destination quickly and efficiently, and is suitable for high-speed movement. Mobile radio terminal capable of reducing the power consumption for the selection processing of the mobile radio terminal.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of an embodiment of a mobile wireless terminal device according to the present invention.

FIG. 2 is a view for explaining communication history data stored in a history creation table storage area of the mobile wireless terminal device shown in FIG.

FIG. 3 is a view for explaining data stored in a handover history storage area of the mobile wireless terminal device shown in FIG. 1;

FIG. 4 is an exemplary view for explaining data stored in a candidate base station list storage area of the mobile wireless terminal device shown in FIG. 1;

FIG. 5 is a flowchart for explaining an operation at the time of handover of the mobile radio terminal apparatus shown in FIG. 1;

FIG. 6 is a diagram showing an arrangement and a history route of a wireless zone of a base station for explaining an operation at the time of handover of the mobile wireless terminal device shown in FIG.

FIG. 7 is a diagram showing an arrangement of radio zones and a history route of a base station for explaining an operation at the time of handover of the mobile radio terminal device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Antenna 11 ... Duplexer 12 ... Transmitting device 13 ... Receiving device 14 ... Wireless circuit 14a ... Attenuator 14b ... Amplifier 14c ... Mixer 14d ... Frequency synthesizer 15 ... Intermediate frequency circuit 15a ... Amplifier 15b ... Bandpass filter (BPF) 15c ... Mixer 15d ... Frequency synthesizer 15e ... A / D converter (A / D) 16 ... Receiver 16a ... Searcher 16b-16d ... Finger 16e ... Symbol combiner 17 ... Signal processing unit 100 ... Control unit 200 ... Storage 200a ... Handover History storage area 200b: History creation table storage area 200c: Candidate base station list storage area

Claims (4)

[Claims] A mobile wireless terminal wirelessly connected by a CDMA (Code Division Multiple Access) method to a plurality of wireless base stations connectable to a communication network, wherein identification information of a communicating base station and communication of the communicating base station are provided. Communication history storage means for storing an order and, when a handover is required, a radio base station search means for searching for a radio base station capable of handover in an order based on information stored in the communication history storage means. A mobile radio terminal, comprising: a radio connection unit that, when a radio base station capable of handover is detected by the radio base station search unit, wirelessly connects to the detected radio base station. 2. The radio base station searching means, when a handover is required, based on information stored in the communication history storage means, from a radio base station connected before the handover is required. 2. The mobile radio terminal according to claim 1, wherein radio base stations connected in the past by handover are obtained, and among them, a radio base station capable of handover is searched for in descending order of handover times. 3. The wireless base station searching means, based on information stored in the communication history storage means, is configured to connect to a wireless base station connected by handover in the past from a wireless base station connected before handover became necessary. 2. The mobile radio terminal according to claim 1, wherein stations are obtained, and among the radio base stations having the predetermined number of handovers or more, a radio base station capable of handover is searched in descending order. 4. The wireless base station searching means, based on information stored in the communication history storage means, is configured to connect a wireless base station connected before handover was required to a wireless base station previously connected by handover. 2. The mobile radio terminal according to claim 1, wherein stations are determined, and a radio base station capable of handover is searched in order from a predetermined number of radio base stations having a large number of handovers.