JP2008148196A - Radio communication terminal, and hand-off method in radio communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication terminal and hand-off method in the radio communication terminal in which the effect of momentary interruption in MAHHO can be suppressed as little as possible. <P>SOLUTION: A radio communication terminal 1 comprises a control unit 12 which carries out radio communication while switching a frequency to be used by a communication unit 11 and when a search request requesting search processing of a hand-off candidate frequency is received while the communication unit 11 performs transmission processing on data constituted of a plurality of continuous packets, the control unit 12 specifies a search specification time on the basis of the received search request. When transmission of data under transmission is completed within the relevant search specification time, search processing is performed after the completion of transmission of the data. If the transmission of the data is not completed within the search specification time, the transmission of the data is interrupted and search processing is performed. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a radio communication terminal performing hard handoff and a handoff method in the radio communication terminal.

  In recent years, in order to make effective use of frequency bands used in wireless communication systems and to make the used frequency bands conform to the global standard specifications, reorganization of frequency bands has been studied.

For example, in a radio communication system using CDMA2000 1x (Code Division Multiple Access 2000 1x), the Japanese specification 800 MHz band (hereinafter referred to as the old 800 MHz band) is currently used in Japan. It is scheduled to be reorganized to the new 800 MHz band. The old 800 MHz band and the new 800 MHz band differ in allocation of uplink and downlink in the frequency band to be used.
Against this background, multiband-compatible wireless communication terminals capable of communication in the current frequency band (old 800 MHz band), new frequency (new 800 MHz band), and high frequency band (2 GHz band) have been developed. .

In CDMA2000 1x, one of the base stations has one or more sectors divided by pilot codes, and each sector is assigned one channel for communication.
The wireless communication terminal communicates with the base station using any channel. Hereinafter, a simple description will be given using an example in which one pilot code is associated with one base station (that is, only one channel is assigned to each base station).

In the above-described multi-band compatible wireless communication terminal that can use a plurality of frequency bands and a wireless communication system that uses a plurality of frequency bands, when the wireless communication terminal moves, it differs from the base station that is currently communicating. It becomes necessary to switch to the base station of the frequency band.
The function of switching base stations (communication channels) for communication is called handoff (or handover), and there are two types of handoff, soft handoff and hard handoff (see, for example, Patent Document 1).

  Soft handoff is a handoff performed without switching the frequency, and is a handoff method unique to CDMA. After the base station (handoff source channel) that is currently communicating with the base station (handoff destination channel) to be newly communicated is temporarily set in the simultaneous communication state, the base station is switched.

  Specifically, the currently communicating base station outputs a list of neighboring base stations, the wireless communication terminal receives this and measures the signal strength of the pilot signal with each base station in the list, This result is transmitted to the base station with which the wireless communication terminal is currently communicating. Based on the result, the base station determines the base station of the handoff destination. ) Without handoff.

As described above, since a wireless communication terminal always communicates with one or more base stations in soft handoff, communication is not interrupted during handoff. However, soft handoff is not always possible (soft handoff is not possible when two base stations cannot provide services to the mobile terminal at the same frequency), so hard handoff is performed.
In the hard handoff, when the communication is transferred from the first base station to the second base station, the communication with the first base station is maintained until immediately before the communication is switched to the second base station. Switch. For this reason, the in-use channel is temporarily released, and an instantaneous communication interruption occurs when the frequency band is switched.

  In the CDMA2000 1x system, which is one of the IMT-2000 standards, two systems of DAHHO (Data Assisted Hard Hand Off) and MAHHO (Mobile Assisted Hard Hand Off) can be used when performing hard handoff.

Each will be described below. That is, DAHHO is a system in which hand-off is performed for a second base station directly designated by the first base station, without the mobile terminal searching for other frequencies before hand-off.
In DAHHO, since the first base station unilaterally designates the second base station without referring to the information of the portable terminal, the portable terminal designates the second base station designated by the first base station. There is no guarantee that it can be captured, and there is a relatively high probability of handoff failure.

On the other hand, in MAHHO, the mobile terminal receives a list of neighboring base stations (channels) in different frequency bands designated from the first base station that is currently communicating, and is designated according to a search command from the first base station. The base station (channel) in the list is searched by switching to the list frequency for a moment. In searching for a base station in the list, the mobile terminal measures the energy intensity of pilot signals with all the base stations (channels) in the list. The portable terminal switches the frequency to the original frequency again, and reports the measured energy intensity of all base stations (channels) to the first base station. The first base station uses the reported energy intensity as a basis. The second baseless station is determined from the base stations in the list. And the instruction | indication for switching communication to a 2nd base station is transmitted to a portable terminal, and a portable terminal performs handoff according to this instruction | indication.
JP 2003-244742 A

  In the MAHHO described above, when the wireless communication terminal measures the energy intensity of pilot signals of all base stations in the neighboring base station list of different frequencies received from the first base station, Since the measurement was performed by temporarily switching the frequency from the frequency during communication, the signal with the first base station is temporarily interrupted (instantaneous interruption). For example, if communication with the base station is temporarily interrupted during data communication, the packet to be transmitted is broken, and after returning from a momentary interruption, the broken packet may be retransmitted. There was an inconvenience that transmission throughput deteriorated.

  In order to suppress instantaneous interruption, it is only necessary to reduce the frequency switching frequency and time, and in order to reduce the frequency switching frequency and time, the number of base stations (channels) that measure the energy intensity of the pilot signal is reduced. It is possible. However, in the conventional MAHHO, if the number of base stations (channels) to be measured is reduced, the number of handoff candidates itself is reduced. Therefore, a valid base station (channel) cannot be found as a handoff destination, and handoff fails. There was an inconvenience of doing so.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radio communication terminal and a handoff method in the radio communication terminal that can suppress the occurrence of instantaneous interruption as much as possible in MAHHO.

  A wireless communication terminal according to a first aspect of the present invention is a wireless communication terminal that performs wireless communication with a plurality of base stations, and selects one from a plurality of frequencies that enable packet transmission / reception. A communication unit that performs wireless communication and a control unit that switches the frequency used by the communication unit to execute the wireless communication, and the control unit is configured to transmit handoff candidate frequencies during the data transmission process by the communication unit. When a search request for requesting a search process is received, a specified search time is specified based on the received search request, and it is determined whether transmission of data being transmitted is completed within the specified search time. If the transmission of the data is completed, a search process is performed after the transmission of the data is completed. If the transmission of the data is not completed within the specified search time, the transmission of the data is interrupted. It is obtained by configured to perform switch processing.

  The wireless communication terminal according to the present invention further includes a storage unit, and the control unit stores the storage when the transmission of data when the search request is received is transmission of data stored in the storage unit. The time required for transmission of all transmission data is calculated from the total amount of data stored in the unit and the current transmission rate in the communication unit, and it is determined whether transmission is completed within the specified search time Good.

  Further, in the wireless communication terminal of the present invention, when the transmission of data when receiving the search request is reception of data by the communication unit, the control unit is currently receiving data from data already received. Configured to obtain information on the total amount of data, calculate a remaining reception time from the total amount of data being received and the current reception rate in the communication unit, and determine whether transmission is completed within the specified search time Also good.

  Further, in the wireless communication terminal of the present invention, when the control unit receives the search request, whether the search request is a periodic search request for requesting to report a result of periodically performing a search process. If it is the periodic search request, the periodic information specified by the periodic search request is extracted, and the specified search time is determined based on the periodic information. Also good.

  Further, in the wireless communication terminal of the present invention, when the control unit receives the search request, whether the search request is a periodic search request for requesting to report a result of periodically performing a search process. If it is not the periodic search request, the search processing is interrupted to complete the data transmission when the search request is received, and the search processing is performed without specifying the specified search time. Also good.

  Further, in the wireless communication terminal of the present invention, the data being transmitted is configured by a plurality of continuous packets, and the control unit is performing transmission when interrupting data transmission to perform the search process. You may comprise so that it may control so that transmission of the following packet may be stopped after transmission of a packet is completed.

  A handoff method in a wireless communication terminal according to a second aspect of the present invention is a wireless communication terminal that performs wireless communication with a plurality of base stations, and performs wireless communication by switching a communication channel from a currently communicating frequency to another frequency. A search request receiving step for receiving a search request for requesting a search process for a handoff candidate frequency, and when the search request receiving step occurs during data transmission, based on the received search request A specified time specifying step for specifying a specified search time; a search step after transmission for performing search processing after completion of transmission of the data; a transmission interruption search step for performing search processing by interrupting transmission of the data; and the specified time When transmission of data in progress is completed within the specified search regulation time when a specific step occurs Perform serial transmission completion search step, if not completed those having a completion judgment step for performing said transmission interruption search step.

  ADVANTAGE OF THE INVENTION According to this invention, the handoff method in the radio | wireless communication terminal and radio | wireless communication terminal which can suppress the influence of a momentary interruption in MAHHO as much as possible can be provided.

  Hereinafter, a radio communication terminal and a handoff method in the radio communication system according to the embodiment of the present invention will be described. Before that, the radio communication terminal 1 performs communication using the base station 2 (base station A). A typical sequence of the wireless communication system in the case where the MAHHO operation is performed on the base station 2 (base station B) having a different frequency will be described with reference to FIG.

As described above, MAHHO is a method in which a CDMA base station 2 determines a hard handoff base station 2 based on the energy intensity of the base station measured by the wireless communication terminal 1 serving as a mobile station. This has the effect of increasing the success rate of inter-frequency hard handoff and making it difficult for call disconnection to occur.
The MAHHO monitors a PPSMM (Periodic Pilot Strength Measurement Message), which is a pilot signal strength measurement result reported from the wireless communication terminal 1, and starts a handoff when the energy strength of the local station becomes below a certain level. Therefore, it is called PPSMM based.

Specifically, in FIG. 1, the base station 2 (base station A) sends a PPMRO (Periodic Pilot Measurement Request Order), which is a pilot signal strength measurement request, to the wireless communication terminal 1 (ST101). The terminal 1 is requested to periodically report the energy intensity of its own station. On the other hand, the wireless communication terminal 1 transmits a PPSMM (Periodic Pilot Strength Measurement Message) to the base station 2 and reports the energy strength in the base station 2 (ST102).
Reports are periodically sent at intervals specified by the previous PPMRO (0.8 to 10.08 seconds, usually 2 to 4 seconds), but only if the threshold is specified by PPMRO. The wireless communication terminal 1 is exempted from reporting for the purpose of avoiding traffic congestion while not satisfying.

Next, the base station 2 (base station A) determines its own energy intensity reported by the PPSMM, and considers that the call may be lost if the energy intensity falls below a certain level. At this time, in order to reduce this possibility, the base station 2 (base station A) transmits a handoff candidate search request message (CFSRQM: Candidate Frequency Search Request Message) to the wireless communication terminal 1 (ST103). It conveys parameters such as candidate system frequencies, base station list, search window size, search interval, and threshold.
Here, one of the important parameters is a search type, which indicates one of three stages of “0 = search stop”, “1 = single search start”, and “3 = regular search start”. . “0 = stop search” can be used when only the information of various parameters is passed to the wireless communication terminal 1 and the actual search is stopped without being performed. “1 = Start single search” can be used when the wireless communication terminal 1 performs a search only once and reports the result. “3 = Start periodic search” can be used to cause the mobile station to periodically perform a search and report the results periodically.

  The network can use three types of search according to traffic conditions and geographical conditions.

Subsequently, the wireless communication terminal 1 transmits a handoff candidate search response message (CFSSMSM) to the base station 2 (base station B) to notify that the CFSRQM has been accepted (ST104). On the other hand, base station 2 (base station B) sends CFSCNM (Candidate Frequency Search Control Message) to radio communication terminal 1, and designates the search type as “1 = start single search” (ST105).
Here, unlike CFSRQM, parameters other than the search type are not carried at all, so the influence on traffic is negligible. If parameters such as frequency and pilot list of handoff candidate systems are fixed and do not change infrequently, the network will not adversely affect traffic only if it only wants to change the search type. CFSCNM can be used.

Next, the wireless communication terminal 1 sends a handoff candidate search report message (CFSRPM) to the base station 2 (base station A), and the pilot measurement result of the candidate system specified by the GFRQM is displayed. Report (ST106). At this time, a candidate frequency search (CFS) is performed.
If a base station of a candidate frequency having a strength that can be handed off at this point is reported, the base station 2 (base station A) can request the wireless communication terminal 1 to perform handoff. If the condition is not satisfied, base station 2 (base station A) continues to send CFSRQM and designates the search type as “3 = periodic search start” (ST107). Subsequently, the wireless communication terminal 1 transmits a handoff candidate search response message (CFSSMSM) to the base station 2 (base station A) to notify that the CFSRQM has been accepted (ST108).

Radio communication terminal 1 transmits CFSRPM to base station 2 (base station A), and periodically reports the measurement results of pilots of candidate systems specified by CFSRQM (ST109). At this time, a candidate frequency search (CFS) is performed. The report is periodically transmitted at a search cycle specified by CFSRQM (0.48 to 200 seconds, usually about 2 to 4 seconds), but only when the threshold is specified by CFSRQM while the threshold is not satisfied. The wireless communication terminal 1 is exempted from reporting for the purpose of avoiding traffic congestion.
In response to the report of the base station that satisfies the handoff, the base station 2 (base station A) transmits a handoff request message (UHDM: Universal Hand Off Direction Message) to the wireless communication terminal 1, and the base station of the candidate frequency. 2 (base station B) makes a handoff request (ST110).
The wireless communication terminal 1 performs handoff as specified, sends a handoff completion message (EHOCM: Extended Hand Off Completion Message) to the new base station 2 (base station B), and the MAHHO operation is completed (ST111). ).

  As described above, MAHHO is a pilot in which the radio communication terminal 1 is switched from the currently used frequency to another frequency while communicating with a certain base station 2 (base station A). This is a handoff method in which a search is performed from another base station 2 (base station B) having a strong signal strength and communication is switched to the base station 2 having the strongest signal strength. Therefore, since frequency switching occurs during the handoff candidate frequency search, transmission data and reception data exchanged during data communication are interrupted, and it becomes necessary to perform useless retransmission processing. In particular, during a periodic search with a search type = 3, data is usually interrupted every 2 to 4 seconds. When retransmission is performed, transmission / reception efficiency (throughput) decreases.

Specifically, as shown in the flowchart of FIG. 2, the flow of the search process for the handoff candidate frequency is shown in the flowchart, the wireless communication terminal 1 transmits the CFSRQM of search type = 3 from the base station 2 and searches for the handoff candidate frequency. Is started (ST201 “Yes”), the wireless communication terminal 1 first stops transmission (ST202), switches to a candidate frequency, performs a base station search of the candidate frequency (ST203, ST204), Switching to the frequency restarts transmission (ST205, ST206). Then, the handoff candidate frequency search result is reported to the base station 2 that requested the CFSRPM (ST207).
For this reason, if data is being transmitted when the transmission is stopped as described above, the data is destroyed, and it is necessary to retransmit the data when transmission is resumed. If the frequency is switched at the time of data reception, the data being received at that time is also destroyed, and it is necessary to transmit the retransmission request to acquire the data again. Therefore, the throughput is lowered.

  For this reason, in the wireless communication terminal according to the embodiment of the present invention described below, the start timing of the search process for measuring the signal strength accompanied with the frequency switching is determined by considering the packet as the transfer unit. This is intended to reduce the destruction of data and avoid the deterioration of the data transfer efficiency during the hard handoff. The search processing start timing is a packet boundary or triggered by a decrease in throughput. Details will be described below.

  FIG. 3 is a block diagram showing an internal configuration of the wireless communication terminal according to the embodiment of the present invention. As illustrated in FIG. 3, the wireless communication terminal 1 includes a communication unit 11, a control unit 12, a storage unit 13, an audio processing unit 14, a speaker 15 (SP), a microphone 16 (MIC), a display unit 17, and an operation unit. 18 is comprised.

The communication unit 11 transmits and receives radio signals to and from the base station 2 via a channel assigned by any of the base stations 2.
The communication unit 11 is capable of transmitting and receiving radio signals in a plurality of frequency bands. Specifically, the communication unit 11 has a current frequency band (old 800 MHz band), a new frequency band (new 800 MHz band), and a high frequency frequency. Wireless signals can be transmitted and received using a band (2 GHz band).

  Note that the band classes defined in 3GPP2 (3rd Generation Partnership Project 2) are assigned to the above-described communication systems of different frequency bands as identification numbers for identifying frequency bands between the base station 2 and the wireless communication terminal 1. Has been. For example, in the information notified from one base station 2 to the wireless communication terminal 1, a communication system existing in the vicinity of the wireless communication terminal 1 is notified to the wireless communication terminal 1 in a neighboring base station list (N-list) or the like. This band class is used for doing so.

The current frequency band (old 800 MHz band) is classified as band class 3, the new frequency band (new 800 MHz band) is classified as band class 0, and the high frequency band (2 GHz band) is classified as band class 6. Priorities are set in advance in these frequency bands, and band class 6 has the highest priority, then band class 0, and band class 3 has the lowest priority.
The band classes and priorities described here are merely examples, and greatly depend on the infrastructure deployment status of the communication carrier.

  The communication unit 11 identifies the frequency band at the time of communication with the base station 2 based on the band class described above.

The control unit 12 controls the operation of the wireless communication terminal 1. Specifically, an audio signal (audio data) included in a signal output from the communication unit 11 is output to the audio processing unit 14, and an audio signal output from the audio processing unit 14 is output to the communication unit 11.
In addition, the control unit 12 controls which of the plurality of frequencies is used for transmitting and receiving the radio signal by the communication unit 11, and performs handoff to the communication unit 11 in response to a handoff request from the base station 2. Let it run. Handoff is a process of switching the communication target from the currently communicating base station 2 to another base station, that is, performing a transition between channels.

The control unit 12 also receives a search request for a handoff candidate frequency from the base station 2 with which the communication unit 11 is communicating, and performs a capture operation by switching from the currently used frequency to the handoff candidate frequency. Control is performed to search for a handoff candidate frequency when transmission of a packet in transmission or reception of a packet in reception of a queue or a received packet sequence is completed.
Therefore, the control unit 12 includes a handoff processing unit 120, a message exchange unit 121, a parameter storage unit 122, a search control unit 123, a pilot signal strength measurement unit 124, a frequency setting unit 125, and transmission / reception data amount acquisition. Unit 126, transmission / reception rate prediction calculation unit 127, transmission / reception completion time prediction calculation unit 128, timer 129, and comparison calculation unit 130.

  The message exchange unit 121 performs various messages (PPMRO, PPSMM, CFSRQM, CFSRSM, CFSCNM, CFSRPM, CFSRSM, CFSRPM) shown in FIG. 1 in order for the wireless communication terminal 1 to execute the MAHHO sequence with the base station 2. , UHDM, EHOCM), of which the frequency, base station list, search window size, search interval, search type, threshold value of the handoff candidate communication system attached to the search request message (CFSRQM) transmitted from the base station 2 Etc. are stored in the parameter storage unit 122. The parameter storage unit 122 is actually allocated and held in a predetermined area of the storage unit 13.

  Under the control of the handoff processing unit 120, the search control unit 123 performs a pilot search of a neighboring base station 2 during communication or a base station 2 that is switched during hard handoff based on various parameters held in the parameter storage unit 122. Do. Here, “pilot search” refers to a process of setting a search window and searching for a pilot channel that can be used in the search window, including multipaths.

  The pilot signal strength measuring unit 124 is the signal strength of the pilot signal from the base station 2 (that is, the signal strength of each channel divided into pilot signals, and the strength of the channel signal to be used in the radio wave that can be received by the communication unit 11. ). The signal strength measurement method includes a method of measuring the energy strength of the pilot signal, but the signal strength measurement method is not limited here. Further, the frequency setting unit 125 performs frequency switching control of the communication unit 11 according to the frequency allocation of the new base station indicated in the handoff instruction analyzed by the handoff processing unit 120 described later.

The transmission / reception data amount acquisition unit 126 acquires the transmission / reception data amount described in the header of the transmission / reception packet and supplies it to the transmission / reception completion time prediction calculation unit 128. In addition, the transmission / reception completion time prediction calculation unit 128 is supplied with the transmission / reception rate calculated by the transmission / reception rate prediction calculation unit 127 under the control of the handoff processing unit 120. The calculation is executed and supplied to the comparison calculation unit 130.
It is a well-known technique that the transmission / reception rate is estimated from the signal strength of the handoff candidate frequency measured by the pilot signal strength measuring unit 124.

In addition, the comparison operation unit 130 is supplied with specified time data required for one search process, which is monitored by the timer 129, and is compared with the transmission / reception completion time generated by the transmission / reception completion time acquisition unit 128. The result obtained is supplied to the handoff processing unit 120.
Here, since the comparison operation unit 130 is mainly targeted for search processing with a fixed period of search type = 3, even if the current search is delayed until the next search period, It is determined whether transmission / reception of a packet being transmitted / received can be completed.

When the handoff processing unit 120 receives a handoff request message (UHDM) from the base station 2, each of the message exchange unit 121, the search control unit 123, the pilot signal strength measurement unit 124, and the frequency setting unit 125 described above is used. Control and execute handoff process. Specifically, the handoff request message (UHDM) is analyzed to specify the handoff type (soft handoff and hard handoff), frequency allocation, pilot PN code sequence, search window information, and the like.
The handoff processing unit 120 controls the above-described transmission / reception data amount acquisition unit 126, transmission / reception rate prediction calculation unit 127, transmission / reception completion time prediction calculation unit 128, timer 129, and comparison calculation unit 130, and executes handoff processing. . Specifically, when the communication unit 11 receives a search request for a handoff candidate frequency from the communicating base station 2 and performs a capture operation by switching from the currently used frequency to the handoff candidate frequency, a continuous transmission packet sequence Alternatively, a search for a handoff candidate frequency is executed upon completion of transmission of a packet being transmitted or reception of a packet being received in the received packet sequence.

  The functions of the respective blocks 120 to 130 described above are achieved by executing the respective programs stored in the storage unit 13 by the control unit 12. It does not indicate only what is divided and incorporated as another block, but is simply a representation of each processing unit separately for the sake of simplicity.

On the other hand, the storage unit 13 stores various data used for processing in the control unit 12. For example, a computer program provided in the control unit 12, an address book for managing personal information such as a telephone number and an email address of a communication partner, an audio file for playing a ringtone or an alarm sound, an image file for a standby screen, Various setting data, temporary data used in the program processing, etc. are stored.
The above-described storage unit 13 is configured by, for example, a nonvolatile storage device (nonvolatile semiconductor memory, hard disk device, optical disk device, etc.), a randomly accessible storage device (eg, SRAM, DRAM), or the like.

The audio processing unit 14 processes the audio signal received by the communication unit 11 and output from the speaker 15 or the audio signal input from the MIC 16. That is, the audio processing unit 14 amplifies the audio input from the MIC 16, performs analog-digital conversion, further performs signal processing such as encoding, converts it into digital audio data, and outputs it to the control unit 12.
In addition, the audio processing unit 14 performs signal processing such as decoding, digital-analog conversion, amplification, and the like on the audio data supplied from the control unit 12, converts the audio data into an analog audio signal, and outputs the analog audio signal to the SP 15.

  The display unit 17 is configured using a display device such as a liquid crystal display panel or an organic EL (Electro-Luminescence) panel, for example, and displays an image corresponding to the video signal supplied from the control unit 12. For example, display various information and images such as the phone number of the callee at the time of outgoing call, the phone number of the other party at the time of incoming call, the contents of received mail and outgoing mail, date, time, remaining battery level, success / failure of outgoing call, standby screen To do.

  The operation unit 18 includes keys to which various functions are assigned such as a power key, a call key, a numeric key, a character key, a direction key, a determination key, and a call key. Is operated, the signal corresponding to the operation content is generated and input to the control unit 12 as a user instruction.

FIG. 4 is a flowchart cited for explaining the operation of the radio communication terminal according to the embodiment of the present invention. 5 and 6 are diagrams showing the relationship between packets and search processing scheduling, which are cited to explain the operation of the wireless communication terminal according to the embodiment of the present invention. Each of the case where the process ends (FIG. 5) and the case where the process does not end within the specified time (FIG. 6) are shown.
The operation of the radio communication terminal according to the embodiment of the present invention shown in FIG. 3 will be described in detail below with reference to FIGS. That is, an example of the inter-packet search process in which the process until the acquisition process operation (CFS) shown in FIG. 3 is performed according to the conditions when the search request (CFSRQM) is received will be described with reference to FIG.

Here, the search operation will be described by exemplifying the case of a periodic search request with search type = 3. In the case of a single search request with search type = 1, it is necessary to return a report to the base station 2 only once, and the search for the handoff candidate frequency required for this is limited to once or twice. This is the same as data loss due to deterioration of radio quality at the time, and therefore does not cause much problem. Therefore, it is excluded from the control target of the search operation described below. The search operation described below is performed only during data communication, and the conventional search operation is performed during voice communication.
In the flowchart of FIG. 4, the wireless communication terminal 1 has received a CFSRQM of search type = 3 that needs to periodically execute a handoff candidate frequency search from the base station 2 during data communication (during transmission of a packet sequence). And At this time, the wireless communication terminal 1 executes a search for a handoff candidate frequency, and at that time, performs search scheduling according to the following procedure.

  First, the wireless communication terminal 1 is currently transmitting data (transmitting user data stored in the storage unit 13 instead of “NULL”) at the timing when a search for a handoff candidate frequency is attempted. (ST401). If data transmission is in progress (ST401 “Yes”), the remaining amount of data being transmitted is monitored, and whether or not the specified time is violated even if a search is executed after the transmission of the remaining amount is completed. judge. Here, the handoff processing unit 120 checks the size of the data to be transmitted with reference to the storage unit 13, and specifies the remaining amount of transmission data based on the difference between this and the amount already transmitted as a transmission packet. Then, the remaining transmission time of the continuous packets currently being transmitted is calculated (ST402). Further, it is determined whether or not the transmission time obtained as a result of the calculation is included in the specified time range of the handoff candidate frequency search (ST403).

  Specifically, the calculation of the remaining transmission time is performed by the transmission / reception completion time prediction calculation unit 128 acquiring data related to the remaining transmission data amount from the transmission / reception data amount acquisition unit 126, and the acquired data and the transmission / reception rate prediction calculation unit 127. This can be calculated by dividing the calculated transmission / reception rate. Then, the comparison operation unit 130 compares the calculated time with the specified time monitored by the timer 129, so that the remaining transmission time of the continuous packets currently being transmitted falls within the specified time range of the handoff candidate frequency search. Whether it is included can be determined.

Here, since the comparison operation unit 130 targets a search request with a fixed period of search type = 3, even if the transmission of the currently transmitted packet is terminated until the next incoming search period, It is determined whether or not the search can be terminated. The wireless communication terminal 1 must report the search result based on the search period specified together with the search type 3 when receiving the search request (CFSRQM). When a search result report is requested and it takes y seconds for the search and transmission of the report, the search specified time is within the time “xy” seconds obtained by subtracting y seconds from x seconds after receiving the search request. . That is, when the time required for the search and its report is very short, at least the time interval specified in the search cycle can be interpreted as the search specified time.
Here, when it is determined that it falls within the specified time range (ST403 “Yes”), the handoff processing unit 120 waits for the end of transmission of a continuous packet sequence and completes transmission of all packets. The search control unit 123 is controlled to execute the search process (ST404). On the other hand, when it is determined that the search processing is not performed within the specified time when the search processing is executed after completion of transmission of all packets (ST403 “No”), the handoff processing unit 120 terminates transmission of the packet as a data transfer unit. The search control unit 123 is controlled to perform the search process by interrupting the transmission of data between the packet being transmitted and the next continuous transmission packet (ST405), and at the boundary of the packet. Then, control is performed to stop the temporary transmission of packets after the immediately following packet (ST406).

Next, it is determined whether or not wireless communication terminal 1 is currently receiving a packet (receives user data from the currently communicating base station instead of “NULL”) (ST407). When receiving (ST407 “Yes”), if the remaining amount of data being received is known, the specified time is not violated even if a search is executed after completion of reception of the remaining amount based on that. It is determined whether or not.
Here, handoff processing section 120 calculates the remaining reception time of consecutive packets that are currently being transmitted (ST408), and whether or not the reception time obtained as a result of the calculation is included in the specified time range of the handoff candidate frequency search. Is determined (ST409). Specifically, the remaining reception time is calculated by searching for information serving as a header portion of data to be received from a packet that has been received, extracting the total amount of data to be received, or receiving an instruction to start reception from the operation unit 18 in the first place. At this stage, information on data to be received is acquired from the server in advance and stored in the storage unit 13, and the total amount of data currently being received is acquired by referring to this, and predicted from the current reception status. The reception completion time can be predicted by calculating the remaining reception time from the received reception rate. Then, by comparing the comparison operation unit 130 with the specified time based on the search cycle described above monitored by the timer 129, the remaining reception time of the currently received continuous packet is the specified time range of the handoff candidate frequency search. It can be determined whether it is included in.

Here, when it is determined that it falls within the specified time range (ST409 “Yes”), the handoff processing unit 120 waits for reception of a continuous packet sequence, and completes reception of all packets before data is received. The search control unit 123 is controlled so as to interrupt the reception and execute the search process (ST410). On the other hand, if the search process is executed after all receptions are completed and it is determined that the time does not fall within the specified time (ST409 “No”), the packet is waiting for the end of the packet and continues to the currently received packet. The search control unit 123 is controlled to perform a search process between the next received packets (ST411). If the remaining amount of received data is not known, the search control unit 123 is controlled to perform a search process between received packets.
Next, in step S412, the search for the handoff candidate frequency described above with reference to FIG. 3 is performed, and when the original frequency is restored, the search result is reported (CFSRPM) (ST412), and reception is resumed and suspended. If there is a transmission packet (ST413 “Yes”), the handoff processing unit 120 controls the communication unit 11 to resume transmission / reception (ST414).

The actual processing of the wireless communication terminal 1 according to the above-described embodiment of the present invention is shown as <Example 1><Example2> in FIGS.
<Example 1>
In FIG. 5, as described with reference to FIG. 4, the remaining amount of transmission data at the stage of receiving the search request in which the search type 3 is specified ends within the search specified time, and reception is performed for the search specified time. The relationship between the transmission / reception packet and the search process scheduling in the case of not being completed is shown. First, when it is determined that the transmission is completed within a predetermined time at the stage of receiving the search request, the data transmission completion of the transmission data is awaited (a). When the data transmission is completed, the received data packet is still being received, and the reception completion is not completed within the specified time as shown in (b). Waits for the search process until reception is completed. When reception of the currently received packet is completed, the reception is temporarily stopped and the search process is executed. When reception is completed, reception of the received data that was stopped is resumed. (C).

<Example 2>
On the other hand, FIG. 6 shows the relationship between a packet and search process scheduling when transmission does not end within the search specified time (a) and reception does not end within the search specified time (b).
When it is determined that the transmission is not completed within the specified time at the stage where the search request is received, the transmission of the packet being transmitted is awaited with a margin for the specified search time (c). When the packet transmission is completed, the received data packet is still being received. The search process is further waited until the reception is completed. When the reception of the received packet is completed, the reception is temporarily stopped and the search process is executed. Then, the reception of the reception data that has been stopped when the search process is completed is resumed (d).
In both FIG. 5 and FIG. 6, the block indicated by hatched CFS indicates the search processing execution timing.

  At this time, when waiting for the completion of transmission of a transmission or reception packet so that the search processing can be completed within the specified search time, at least allow time for the search processing to complete packet transmission. Even when waiting, it is possible to complete the search process up to the search result report to the base station. If transmission and reception are completed within the specified search time, it is preferable to wait for the search process until transmission and reception are completed. In this case as well, there is a margin for the time required for the search process. There is a need.

  If transmission is not performed at the timing when the search for the handoff candidate frequency is attempted, the search schedule can be determined only by the reception status. In addition to the conventional packet environment, data can not be received by switching the frequency by monitoring the timing when the transmission / reception rate is low within the specified time range in which the search process must be executed. Data loss can be minimized.

FIG. 7 shows the relationship between the packet and the search process scheduling when transmission is not performed as <Example 3>. Here, both (a) and (b) show received data as an example. Note that the transmission data may be similarly processed according to the rate.
First, when a search request is received, the handoff processing unit 120 monitors the reception (transmission) rate generated by the reception (transmission) rate prediction calculation unit 127 while leaving a margin within the specified search time. Compared with the reception (transmission) rate at the time of reception and a predefined threshold, the capture processing is not performed until the level is lower than these values, and if such a decrease in rate occurs, the reception (transmission) Waiting for the completion of reception (transmission) of a packet. When reception (transmission) is completed, search processing is performed, and then reception (transmission) of subsequent packets is resumed. The reception (transmission) rate may be checked in steps ST403 and ST409 in FIG.

As a result, the search process is executed with the timing of the reception (transmission) rate as low as possible within the specified time range in which the search must be performed, so that a reduction in throughput due to the acquisition process can be prevented. .
In FIG. 7, blocks indicated by hatched CFS indicate search processing execution timing. By the way, if the reception (transmission) rate does not decrease within the time obtained by subtracting the time required for the search process from the specified time, the search process is executed so that the search process is within the specified time regardless of the reception (transmission) rate. To do.

  As described above, according to the wireless communication terminal 1 according to the embodiment of the present invention, when the MAHO operation is performed during data communication, the remaining amount of data to be transmitted is small, and data transmission is performed within the search specified range. If it is completed, the search for the handoff candidate frequency is executed after the data transmission is completed, so that the search result report in the specified cycle is not neglected and the packet of data to be transmitted is not destroyed. No packet retransmission or the like occurs, and MAHHO does not reduce the throughput. In addition, if the remaining amount of data to be transmitted is large and data transmission is not completed within the specified search range, the search for the handoff candidate frequency is performed with the data transmission interrupted, so what size data is Even in the case of transmission, it is always possible to report a search result at a specified cycle. In other words, when the remaining size of the data being transmitted is small, periodic search result reporting is performed without reducing the throughput, and when the remaining size of the data being transmitted is large, at least periodic search result reporting is performed. Therefore, a decrease in throughput due to MAHHO can be prevented without interfering with the MAHHO operation as much as possible.

  In addition, when searching for a handoff candidate frequency is performed by interrupting data transmission, the search is interrupted after transmission of the packet being transmitted is completed, and transmission is resumed after the search is completed. Since the packet is not destroyed for the complementary frequency search, the throughput can be prevented from being deteriorated as much as possible.

  Furthermore, refer to the downlink or uplink data rate from the total amount of data received from the received data when the data transmission is reception, or from the total amount of data transmitted from the transmission target data itself in the case of transmission. By specifying the time required for completion of transmission / reception (transmission), it is easily determined whether transmission completion of data being transmitted is within the search specified time, and whether or not search processing should be waited until transmission completion. Judgment can be made.

  The flowchart shown in FIG. 4 also shows each step of the handoff method in the wireless communication system of the present invention in addition to the operation of the wireless communication terminal 1 or base station 2 according to the embodiment of the present invention. ing.

  That is, in the handoff method according to the embodiment of the present invention, in the wireless communication terminal 1 that performs wireless communication with a plurality of base stations 2, the communication channel is switched from the currently communicating frequency to another frequency to perform wireless communication. A search request receiving step (ST401) for receiving a search request for requesting a search process for a handoff candidate frequency, and a search request receiving step during data transmission, the received search request A specified time specifying step (ST403, ST409) for specifying a search specified time based on this, a search step after transmission completion (ST404, ST410) for performing a search process after completion of the data transmission, and a search process by interrupting the data transmission. Transmission interruption search steps (ST405, ST411) to be performed and a specified time specifying step occur When the transmission of data being transmitted is completed within the specified search specified time, a completion determination step (ST401 to ST405, ST407) that executes a search step after completion of transmission and executes a transmission interruption search step if not completed. To ST411).

  The present invention is not limited to the embodiment described above. That is, when implementing the present invention, various modifications, combinations, sub-combinations, and alternatives may be made to each component of the above-described embodiment within the technical scope of the present invention or an equivalent scope thereof. Further, in the above-described embodiment, the radio communication system 100 that can cope with the three frequency bands of the old 800 MHz, the new 800 MHz, and the 2 GHz band has been described, but the present invention is not limited to this. A wireless communication system that supports frequency bands other than the above three types may be used, and the number of types of corresponding frequency bands is not limited to three, and may be any number.

It is the figure quoted in order to demonstrate the typical sequence of the radio | wireless communications system in the case of performing MAHHO operation | movement. It is the flowchart quoted in order to demonstrate operation | movement of the handoff candidate frequency search at the time of MAHHO use. It is a block diagram which shows the structure of the radio | wireless communication terminal concerning embodiment of this invention. It is the flowchart quoted in order to demonstrate operation | movement of the radio | wireless communication terminal concerning embodiment of this invention. It is the figure quoted in order to demonstrate operation | movement of the radio | wireless communication terminal concerning embodiment of this invention, and is a figure which shows the relationship between a packet and scheduling of search operation | movement. It is the figure quoted in order to demonstrate operation | movement of the radio | wireless communication terminal concerning embodiment of this invention, and is a figure which shows the relationship between a packet and scheduling of search operation | movement. It is the figure quoted in order to demonstrate operation | movement of the radio | wireless communication terminal concerning embodiment of this invention, and is a figure which shows the relationship between a packet and scheduling of search operation | movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication terminal, 11 ... Communication part, 12 ... Control part, 13 ... Memory | storage part, 14 ... Audio | voice processing part, 15 ... Speaker (SP), 16 ... Microphone (MIC), 17 ... Display part, 18 ... Operation part , 120 ... handoff processing unit, 121 ... message exchange unit, 122 ... parameter storage unit, 123 ... search control unit, 124 ... pilot signal strength measurement unit, 125 ... frequency setting unit, 126 ... transmission / reception data amount acquisition unit, 127 ... transmission / reception Rate prediction calculation unit, 128 ... transmission / reception completion time prediction calculation unit, 129 ... timer, 130 ... comparison calculation unit.

Claims (7)

A wireless communication terminal that performs wireless communication with a plurality of base stations,
A communication unit that performs wireless communication by selecting one of a plurality of frequencies that enables packet transmission and reception;
A control unit that executes the wireless communication by switching a frequency used by the communication unit;
With
The controller is
When the communication unit receives a search request for requesting a search process for a handoff candidate frequency during data transmission processing, it specifies a specified search time based on the received search request and transmits the data being transmitted within the specified search time. It is determined whether or not transmission is completed. When transmission is completed within the specified search time, search processing is performed after transmission of the data is completed. When transmission of the data is not completed within the specified search time, A wireless communication terminal characterized by interrupting data transmission and performing search processing. A storage unit,
When the transmission of data when the search request is received is transmission of data stored in the storage unit, the control unit determines the total amount of data stored in the storage unit and the current amount in the communication unit. 2. The wireless communication terminal according to claim 1, wherein a time required for transmission of all transmission data is calculated from a transmission rate, and it is determined whether or not transmission is completed within the specified search time. When the transmission of data when the search request is received is reception of data by the communication unit, the control unit acquires information on the total amount of data currently being received from data that has already been received, and the reception 2. The wireless communication terminal according to claim 1, wherein a remaining reception time is calculated from a total amount of data therein and a current reception rate in the communication unit, and it is determined whether transmission is completed within the specified search time. When the control unit receives the search request, the control unit determines whether the search request is a periodic search request for requesting to report a result of a periodic search process, and the periodic search request 4. If there is, the periodic information specified by the periodic search request is extracted, and the specified search time is determined based on the periodic information. The wireless communication terminal described in 1. When the control unit receives the search request, the control unit determines whether the search request is a periodic search request for requesting to report a result of a periodic search process, and the periodic search request 5. The wireless communication terminal according to claim 4, wherein if there is not, the wireless communication terminal performs search processing by interrupting the completion of data transmission when a search request is received without specifying the specified search time. The data being transmitted is composed of a plurality of consecutive packets,
The control unit, when interrupting data transmission to perform the search process, controls to stop transmission of subsequent packets after transmission of a packet being transmitted is completed. The wireless communication terminal according to any one of 1 to 5. In a wireless communication terminal that performs wireless communication with a plurality of base stations, a handoff method for continuing a wireless communication by switching a communication channel from a currently communicating frequency to another frequency,
A search request receiving step for receiving a search request for requesting a search process for a handoff candidate frequency;
When the search request receiving step occurs during data transmission, a specified time specifying step for specifying a specified search time based on the received search request;
A post-transmission search step for performing a search process after transmission of the data;
A transmission interruption search step for interrupting transmission of the data and performing a search process;
When the specified time specifying step occurs, the search step after the completion of transmission is executed when the transmission of data being transmitted is completed within the specified search specified time, and the transmission interruption search step is executed when the transmission is not completed. A completion determination step;
A handoff method characterized by comprising:

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