JP2008283332A - Radio communication unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide radio communication equipment for continuously performing speech or data communication by setting a threshold exclusive for hand-over, and selecting an optimal radio base station in hand-over time. <P>SOLUTION: This radio terminal equipment is configured to, when a radio wave state from a radio base station is deteriorated during the communication of speech or data communication, receive a radio wave from a different radio base station by a reception part 23, and to detect the reception electric field level of the radio wave by a reception electric field level detection means 25, and to compare the detected detection value with a first threshold preset in an RAM 31, and to, when the detected detection value is larger than a first threshold, make a hand-over request to the radio base station which transmits a radio wave which is larger than the first threshold, and to, when the detection value is lower than the first threshold, compare the detection value with a second threshold which is lower than the first threshold, and to make a hand-over request to the radio base station which transmits a radio wave whose reception electric field level is higher than the second threshold, and whose reception electric field level is the highest within a prescribed period. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication device used in a communication system such as a PHS (Personal Handyphone System), and more particularly to a wireless communication device that performs handover by selecting an optimal wireless base station.

When a wireless communication device moves between areas during communication, handover is performed by switching communication with a wireless base station in the old area to communication with a connection target wireless base station in the new area. It is to continue communication.
Selection of a connection-destination radio base station for a new area at the time of this handover is performed by detecting the reception electric field level of the radio wave from the radio base station once, and the reception electric field level is determined in advance by the radio communication device (for example, the PHS terminal main body). It is determined whether or not the threshold value is higher than the set threshold value. If the threshold value is higher than the set threshold value, connection processing with the radio base station is performed.

  In such a connection process, a connection is made when a radio base station transmitting a radio wave whose received electric field level is higher than a preset threshold is detected. In an area where the wireless communication device can receive, even if there is a wireless base station having a higher received electric field level than the connected wireless base station, it cannot be connected, and an optimal wireless base station can always be selected. It was not always there.

  In addition, if a radio base station whose reception electric field level is momentarily higher than the threshold is accidentally selected due to fading of radio waves from a new connection destination radio base station, handover may fail as a result. was there.

  Further, when the wireless communication apparatus performs handover, the threshold for selecting the wireless base station is a common threshold used in the location registration process and the handover process. Therefore, in order to increase the success rate of the handover, the threshold is increased. If it is set, the radio area becomes smaller, and there is a possibility that the location registration process cannot be performed because the location registration process cannot find a radio base station whose received electric field level is higher than the threshold value.

Further, in Patent Document 1, in order to improve the communication quality by shortening the connection time or switching time to the radio base station, the RSSI (received electric field strength) of the peripheral radio base station is detected during the non-communication period. The search information is stored in the memory in advance, the RSSI of the radio base station of the communication partner is detected during communication, and when this RSSI detection value falls below the first threshold, it is stored in the memory in advance during the non-communication period. It is described that a radio base station that is equal to or higher than the second threshold value is selected by comparing the search information with the second threshold value, and this radio base station is determined as a handover destination.

JP 2001-95028 A

In the above-described conventional technology, there is a problem when a call or data communication is disconnected by selecting a radio base station that is not optimal at the time of handover.
The present invention has been made in view of the above-described conventional circumstances, and sets a high threshold for handover and selects an optimal radio base station at the time of handover to enable continuous communication and data communication. To provide an apparatus.

In order to achieve the above object, the radio communication apparatus according to the present invention selects a radio base station at the time of handover with the following configuration.
If the radio wave condition from the communicating radio base station deteriorates during a call or data communication, it receives radio waves from multiple radio base stations that are different from the communicating radio base station, The received electric field level of the radio wave is detected and compared with a preset first threshold. When the detected received electric field level is higher than the first threshold, radio waves higher than the first threshold are detected. A handover request is made to the transmitting radio base station.
In addition, when the detected received electric field level is lower than the first threshold, the received electric field level is compared with a second threshold lower than the first threshold, and the received electric field level is set to the second threshold within a predetermined period. A handover request is made to a radio base station that transmits a radio wave that is higher than the threshold and has the highest received electric field level.

The first threshold value is used only during the selection process of the radio base station in order to execute a handover when the received electric field level of the radio wave falls below a predetermined level during data communication or a call. The threshold is set to a value larger than a second threshold described later.
Further, the second threshold value is used, for example, when performing location registration when the power is turned on, and is also used for radio base station selection processing at the time of handover, and a value lower than the first threshold value is set. Is done.

  The state of the radio wave from the above-mentioned radio base station is measured, for example, by measuring the reception field level of the radio wave and detecting it by comparison with a predetermined reception level, or by changing the measurement of the reception field level, The error rate such as the bit error rate and the frame error rate of the data being communicated is measured, and the error rate is detected by comparison with a predetermined level.

The radio communication apparatus of the present invention includes a communication unit that communicates with a radio base station, a reception state detection unit that detects deterioration of a radio wave state, and a reception electric field that detects a reception electric field level of a radio wave from the radio base station. Level detection means, storage means for storing a first threshold used for base station selection processing, and a second threshold lower than the first threshold, and detection results of the received electric field level detection means are stored in advance. And a control means for performing a selection process of the radio base station by comparison with the first threshold value or the second threshold value, and the control means detects deterioration of the radio wave state by the detection means during communication And the detection value detected by the reception electric field level detection means is compared with a first threshold value stored in advance, and if higher than the first threshold value, radio waves higher than the first threshold value are transmitted. Handover to radio base station Carry out the required.
When the detection value detected by the reception electric field level detection means is lower than the first threshold value, the detection value detected by the reception electric field level detection means is compared with the second threshold value, and within a predetermined period, A handover request is made to a radio base station that transmits a radio wave that is higher than the second threshold and has the highest reception level.

  The reception state detection means detects that the received radio wave level has fallen below a preset threshold and that the error rate (bit error rate, frame error rate, etc.) of the received data has exceeded a certain level. It detects the deterioration of the state.

  According to the present invention, a first threshold value for radio base station selection processing at the time of handover is provided, and the radio base station is compared by comparing the first threshold value with the received electric field level of the radio wave transmitted by the radio base station. By selecting, the selection of the radio base station at the time of handover is made more reliable, and when there is no radio base station whose received electric field level is higher than the first threshold, within a predetermined period, Since a handover request is made to a radio base station that is high and has the highest received electric field level, failures in handover processing can be reduced.

A communication system using the PHS will be described with reference to FIG. FIG. 1 is a block diagram showing a schematic configuration of a communication system using PHS.
As shown in FIG. 7, a communication system using PHS is used in factories, offices, etc., and includes a plurality of PHS terminals (wireless communication terminals) 10a to 10d, a data terminal 11, and a plurality of wireless bases. Stations 12a to 12n, a main control device 13, a PHS position display terminal 14, a fixed telephone 15, a private branch exchange (PBX) 16, a LAN (Local Area Network) 17, and a server 18 are provided.

The PHS terminals 10a to 10d are carried by a user to perform a call or data communication.
The data terminal 11 manages various data, and is used to input, store, and display data by user operation, and is connected to the PHS terminal 10d to transmit and receive management data and the like wirelessly. Is to do.
The radio base stations 12a to 12n are relays between the PHS terminals 10a to 10d and the main control device 13, and perform radio communication with the PHS terminals 12a to 12n. The radio base stations 12a to 12n are Each stores a unique radio base station ID.
In addition, cells having a radius of 100 to 500 meters are formed in the communication areas of the radio base stations 12a to 12n, respectively.

The main control device 13 controls calls and data communications in the system. The main control device 13 stores a unique system ID. In a communication system in which a plurality of main control devices 13 exist, this main control device 13 Management for each system can be performed with a unique ID.
The PHS position display terminal 14 displays the current positions of the PHS terminals 10a to 10d based on the position data of the plurality of PHS terminals 10a to 10d managed by the main control device 13.

The fixed telephone 15 is connected to the main control device 13 by wire, and makes a call with the fixed telephones 15, the PHS terminals 10 a to 10 d, the extension terminals, and the like.
The PBX 16 performs line control of a plurality of extension terminals (not shown) connected to the PBX 16 and realizes communication with the PHS terminals 10a to 10d, the fixed telephone 15, and extension terminals via the main control device 13. Is to do.
The server 18 is connected to the main control device 13 via the LAN 17, manages various data, and provides various data to a PHS terminal or the like.

  In the communication system, the PHS terminals 10a to 10d make a handover request to the radio base stations 12a to 12n, and continue talking and data communication while moving through the communication areas of the plurality of radio base stations 12a to 12n. Is.

Next, a radio communication apparatus according to an embodiment of the present invention will be described using a PHS terminal as an example with reference to FIG. FIG. 2 is a block diagram showing a configuration of a wireless communication apparatus (PHS terminal) according to the embodiment of the present invention.
The PHS terminal of the present invention is a radio communication terminal used in the communication system shown in FIG. 1, and communicates with the main control apparatus via any one radio base station of a plurality of radio base stations. In this case, a telephone call or data communication is performed with another wireless communication terminal or a fixed telephone.
As a communication method between the PHS terminals 10a to 10d and the radio base stations 12a to 12n, a time division multiple access method (TDMA) is used, and as a transmission method, time division bidirectional multiplexing is used. A system (TDD: Time Division Duplex) is used.

Each component of the PHS terminals 10a to 10d will be described.
The PHS terminals 10a to 10d include an antenna 21, a SW 22, a receiving unit 23, a transmitting unit 24, a received electric field level detecting unit 25, a receiving unit 26, a transmitting unit 27, an operating unit 28, and a notification unit. 29, a display unit 30, a RAM (Random Access Memory) 31, a ROM (Read Only Memory) 32, a timer 33, a control unit 34, and a received electric field level comparison means 35 of the control unit 34. .

Radio waves from the base stations 12a to 12n are input to the receiving unit 23 via the antenna 21 and the high frequency switch (SW) 22 for switching between transmission and reception.
The receiving unit 23 receives radio waves from the base stations 12 a to 12 n via the antenna and the SW 22, and outputs them to the reception electric field level detection unit 25 and to the control unit 34.
The transmission unit performs predetermined processing on the audio signal and the data signal, and transmits the signal to the radio base station via radio waves via the SW 22 and the antenna 21.

The reception electric field level detection unit 25 detects the reception electric field level of the radio wave received by the reception unit, and outputs the detected detection value to the control unit 34. Using this detection value, a radio base station selection process at the time of handover is performed.
The receiving unit 26 is constituted by a speaker or the like, and converts an input electric signal into a voice signal and outputs the voice signal.
The transmitter 27 is composed of a microphone or the like, and converts an input voice signal into an electric signal and outputs it.

The operation unit 28 includes dial keys including “0” to “9”, “*”, and “#”, a cross key for controlling operations, and the like, and inputs telephone numbers and operation control instructions.
The notification unit 29 notifies an incoming call, a schedule, and the like by hearing with sound such as a melody or vibration of a vibrator.
The display unit 30 is composed of a liquid crystal display or the like, displays received data, displays data according to the operation of the operation unit, displays the reception level based on the detection value detected by the reception electric field level detection unit 25, etc. Is to do.

The RAM 31 stores received data, data input from the operation unit 28, and the like. Further, the RAM 31 stores the received electric field level detection value detected by the received electric field level detection unit 25 and the base station ID of the radio base station that has transmitted the radio wave of the received electric field level detection value in association with each other, and performs a handover request. Used sometimes.
The ROM 32 stores a processing program such as a radio base station selection process and a handover process, which will be described later, a first threshold value, a second threshold value, and the like used for the radio base station selection process. This second threshold is a threshold used for location registration and handover (hereinafter referred to as the second threshold), and the first threshold is a threshold dedicated to handover (hereinafter referred to as the second threshold) (hereinafter referred to as the second threshold). , The first threshold).
The RAM 31 and ROM 32 constitute a storage unit.

The timer 33 measures a predetermined time.
The control unit 34 controls each unit and operates according to a processing program stored in the ROM 32. For example, the control unit 34 performs a radio base station selection process or a handover process at the time of the handover.
The reception electric field level comparison means 35 provided in the control unit 34 compares the detection value output from the reception electric field level detection unit with the first threshold value and the second threshold value preset in the ROM 32. is there.

Next, a handover sequence of the communication system using the PHS terminal will be described with reference to FIG. FIG. 3 is a diagram for explaining a handover sequence of the communication system using the PHS terminal.
In FIG. 3, the PHS terminal deteriorates radio waves from the radio base station 1 during a call with the PHS terminal or a fixed telephone (in FIG. 3, a call is made with the fixed telephone) via the radio base station 1 and the control device. Is detected, the process proceeds to a radio base station selection process.

In this radio base station selection process, first, a radio base station that can communicate with other than the radio base station with which communication is performed to search for a call is searched. For example, in the case of FIG. Radio waves from the radio base stations 2 and 3 other than the base station 1 are received.
Then, radio waves from the radio base stations 2 and 3 are received, the received electric field level is detected, and an optimum radio base station is selected from the detected received electric field level.

When the optimum radio base station selection process is performed, the PHS terminal next shifts to the handover request process for the selected optimum radio base station.
In this handover request process, the PHS terminal makes a handover request to the selected radio base station (radio base station 2 in FIG. 3) (S1).
When receiving the handover request, the radio base station 2 transmits it to the main control device (S2).
When receiving the handover request, the main control apparatus performs an authentication calculation process using a random number or the like, and outputs a call setting acceptance (S3) and an authentication request (S4) to the PHS terminal to the radio base station 2.

Upon receiving the call setting acceptance (S3) and the authentication request (S4), the wireless base station 2 transmits the received call setting acceptance (S5) and the authentication request (S6) to the PHS terminal.
When the PHS terminal receives the call setting acceptance (S5) and the authentication request (S6) from the main control device via the radio base station 2, the PHS terminal performs an authentication calculation process using a random number and the like, and an authentication response including the calculation result Is transmitted (S7).

  When the main control unit receives the authentication response (S8) received via the radio base station 2, the main control unit collates the authentication calculation result. The call is continued through the station 2. In this way, in the PHS terminal, the handover process is performed by the radio base station selection process and the handover request process, and the call and data communication are continued.

The radio base station selection process during handover, which is a feature of the PHS terminal of the present invention, will be described in detail with reference to FIG. FIG. 4 is a follow chart for explaining a radio base station selection process at the time of handover of the PHS terminal of the present invention.
When the PHS terminal detects deterioration of radio waves from the radio base station during communication such as a call or data communication, the control unit 34 activates the timer 33 and starts measuring a predetermined time (step 401).
The detection of radio wave degradation from the radio base station is, for example, that the detection value of the received electric field level detection unit has fallen below a predetermined level, and the error rate (bit error rate, frame error rate, etc.) of the received data is The deterioration of the radio wave condition is detected when a certain level is exceeded.

Then, a radio base station different from the radio base station with which communication is performed is searched, and radio waves from different radio base stations are received (step 402). Here, the radio wave includes data such as the CS-ID of the main controller and the base station ID of the radio base station.
In the PHS terminal, the CS-ID of the main controller of the received data is compared with the CS-ID stored in the PHS terminal to determine whether it is in the system to which it belongs (step 403). . As a result of the determination, if the CS-IDs match, the received electric field level comparing means 35 sets the received level of the received data detected by the received electric field level detecting unit 25 in the ROM 32 in advance. Comparison with the first threshold value (first threshold value) dedicated to handover set to a value higher than the second threshold value (second threshold value) used for location registration and handover (step 404) .

  If the received electric field level detection value is higher than the first threshold value as a result of the comparison in step 404, the operation of the timer 33 is stopped (step 405), and the first base station ID included in the received data is used. A handover request is transmitted with the radio base station transmitting radio waves higher than the threshold value as the optimal radio base station (step 406), the radio base station selection process is terminated, and the process proceeds to the handover process.

If the received electric field level detection value is lower than the first threshold value in step 404, the received electric field level comparison means 35 then receives the received electric field level detection value and the second value used in location registration or handover processing. Is compared with the threshold value (step 408). If the received electric field level detected value is higher than the second threshold as a result of the comparison, the received electric field level detected value is compared with the received electric field level stored in the RAM 31 (step 409). The received electric field level detection value and the base station ID of the base station that transmitted the data of the received electric field level detection value are associated and stored in the RAM 31 (step 410).
In step 409, if there is no stored data, there is no comparison, so the received field level detection value is directly associated with the base station ID of the base station that transmitted the received field level detection value data. The data is stored in the RAM 31.

  After the received data is stored in step 410, it is determined whether or not the measured value of the timer 33 has timed out (step 411). If the result of this determination is that a time-out has occurred, it is confirmed whether or not there is stored data of the received electric field level detected value and the base station ID of the base station that has transmitted the received electric field level detected value data. (Step 412). As a result of this check, if there is stored data, the received electric field level detection value of the stored data is higher than the second threshold value, and the radio wave state from the received radio base station is the highest. The radio base station is determined as the optimum base station, a handover request is transmitted using the base station ID stored in correspondence with the received electric field level detection value (step 406), and the radio base station selection process is completed. To do.

If the received electric field level is lower than the second threshold value as a result of the comparison between the received electric field level detection value and the second threshold value in step 408, the received data is discarded (step 407), and step 411 A determination is made as to whether a timeout has occurred.
In step 409, when the received electric field level detection value higher than the second threshold is lower than the received electric field level of the stored data, the stored data is the optimal data of the radio base station, and thus the received data Is discarded (step 407), and a determination is made as to whether or not a timeout has occurred in step 411.

In step 411, if the time-out has not occurred, radio waves from other radio base stations are received, and the operation in steps 402 to 412 continues until a received electric field level higher than the first threshold is detected. Or it is repeated until it times out.
In step 403, if the CS-ID of the received data does not match the CS-ID stored therein, it is determined that the system is different from the system in which the PHS terminal itself can communicate. The received data is discarded (step 407), and if it has not timed out, it is confirmed whether there is another radio base station. If there is another radio base station, this radio base station The data from the station is received, and the operations from step 403 to step 412 are repeated.

  However, if the received data with the same CS-ID cannot be detected in step 403 before the time-out in step 411, or the received electric field level higher than the first threshold cannot be detected, and is higher than the second threshold. If the received electric field level cannot be detected (when there is no stored data in step 412), there is no radio base station requesting handover, and the radio base station selection process is terminated. At this time, if the user carrying the PHS terminal is notified that there is no radio base station to be handed over, the usability is further improved. As the notification to the user, a notification by sound by the notification unit 29, a notification by vibration of the vibrator, a visual notification by the display unit, or the like can be considered. Note that since the communication such as a call or data communication cannot be continued on the display unit, the reception level is switched to, for example, “out of service area”.

  If a handover request is made and the handover is successful, the data stored in the RAM 31 becomes unnecessary data. Therefore, the stored data is deleted, and the radio base station selection process at the next handover is performed. Prepare.

  As described above, in the PHS terminal of the present invention, the radio base station selection process is performed using the first threshold value and the second threshold value at the time of handover, so that an area where communication with a large number of radio base stations can be performed. Then, since it is possible to select an optimal radio base station from among the many radio base stations, it is possible to reduce handover failures.

  Although the present invention is suitable for a PHS terminal, it relates to selection of an optimal radio base station at the time of handover, and can also be applied to a radio communication device used for other communication methods.

It is a block diagram which shows schematic structure of the communication system using PHS. 1 is a configuration block diagram of a PHS terminal according to an embodiment of the present invention. It is explanatory drawing which shows the connection sequence at the time of the handover of this invention. It is a flowchart figure which shows the selection process of the radio base station at the time of the handover in the PHS terminal of the present invention.

Explanation of symbols

  10a to 10d ... PHS terminal, 11 ... data terminal, 12a-12n ... wireless base station, 13 ... main control device, 14 ... PHS position display device, 15 ... fixed telephone, 16 ... PBX, 17 ... LAN, 18 ... server, 21 ... antenna, 22 ... high frequency switch (SW), 23 ... receiver, 24 ... transmitter, 25. ..Reception electric field level detection unit, 26..Reception unit, 27 ... Transmission unit, 28 ... Operation unit, 29 ... Notification unit, 30, Display unit, 31 ... RAM, 32 ... ROM, 33... Timer, 34... Control unit, 35.

Claims (1)

A wireless communication device that performs communication through one wireless base station among a plurality of wireless base stations,
During communication, if the radio wave condition from the communicating radio base station deteriorates, radio waves from a plurality of radio base stations different from the communicating radio base station are received, and the received electric field level of the radio wave Is detected and compared with a preset first threshold value. If the detected received electric field level is higher than the first threshold value, the radio base station transmitting radio waves higher than the first threshold value. When a handover request is made to the station and the detected received electric field level is lower than the first threshold, the received electric field level is compared with a second threshold lower than the first threshold, and within a predetermined period A wireless communication device, wherein a handover request is made to a wireless base station that transmits a radio wave having a reception electric field level higher than a second threshold and the highest reception electric field level.

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