WO2008072710A1

WO2008072710A1 - Radio communication terminal, handoff method in radio communication terminal, and radio communication system

Info

Publication number: WO2008072710A1
Application number: PCT/JP2007/074060
Authority: WO
Inventors: Takeshi Makabe
Original assignee: Kyocera Corporation
Priority date: 2006-12-13
Filing date: 2007-12-13
Publication date: 2008-06-19
Also published as: JP5143409B2; JP2008148196A

Abstract

It is possible to provide a radio communication terminal, a handoff method in the radio communication terminal, and a radio communication system which can suppress the affect of instantaneous disconnection in the handoff. The radio communication terminal (10) includes a control unit (12) which executes a radio communication by switching the frequency used by a communication unit (11). When the control unit (12) receives a search request which requests for a handoff candidate frequency search process while the communication unit (11) is transmitting data formed by a plurality of continuous packets, the control unit (12) identifies a search-specified time according to the received search request. If the currently executed data transmission is complete within the search-specified time, the search process is executed after completion of the data transmission. If the data transmission is not complete within the search-specified time, the data transmission is interrupted and the search process is executed.

Description

Specification

Wireless communication terminal, handoff method in wireless communication terminal, and wireless communication system

Technical field

The present invention relates to a radio communication terminal that performs hard handoff, a handoff method in the radio communication terminal, and a radio communication system.

Background art

[0002] In recent years, multiband-compatible wireless communication terminals that can use a plurality of frequency bands have been developed. In the wireless communication system that uses a plurality of frequency bands and a wireless communication terminal that supports multiple bands, when the wireless communication terminal moves, the base station that is currently communicating is switched to a base station that is in a different frequency band. Need arises.

The function of switching the base station (communication channel) for communication is called handoff (or handono), and there are two types of handoff: soft handoff and hard handoff.

(For example, see Patent Document 1).

[0003] Soft handoff is a handoff performed without switching the frequency. Newly communicates with the base station (node-off source channel) that is currently communicating! / The base station (node-off destination channel) is temporarily switched to the simultaneous communication state, and then the base station is switched.

[0004] As described above, in a soft handoff, a wireless communication terminal always communicates with one or more base stations! /, So communication is interrupted during handoff! /.

However, soft handoff is not always possible. When two base stations cannot provide services to the wireless communication terminal (mobile terminal) at the same frequency, hard handoff is performed because soft handoff is not possible.

[0005] In the case of hard handoff, when communication is transferred from the first base station to the second base station, communication with the first base station is maintained until immediately before the communication is switched to the second base station. Switch the frequency band. For this reason, the in-use channel is temporarily released, and the communication is interrupted when the frequency band is switched.

Patent Document 1: Japanese Patent Laid-Open No. 2003-244742 Disclosure of the invention

Problems to be solved by the invention

[0006] In the hard handoff described above, the wireless communication terminal first measures the energy strength of pilot signals of all base stations in the neighboring base station list of different frequencies received from the first base station. The frequency power during communication with the base station was measured by temporarily switching the frequency, so the signal with the first base station was temporarily interrupted (instantaneous interruption).

If communication with the base station is temporarily interrupted during data communication, for example, a packet to be transmitted is broken, and after returning from an instantaneous interruption, the broken packet is retransmitted. As a result, there is a disadvantage that the transmission throughput is deteriorated.

[0007] In order to suppress instantaneous interruption, the frequency switching frequency and time may be suppressed. In order to reduce the frequency switching frequency and time, it is conceivable to reduce the number of base stations (channels) that measure the energy intensity of pilot signals.

However, if the number of base stations (channels) to be measured is reduced, the number of handoff candidates itself decreases, so that a valid base station (channel) cannot be found as a handoff destination, and handoff fails. There was a profit.

[0008] An object of the present invention is to provide a radio communication terminal, a handoff method in the radio communication terminal, and a radio communication system that can suppress occurrence of instantaneous interruption as much as possible in hard handoff.

Means for solving the problem

[0009] A wireless communication terminal according to a first aspect of the present invention includes a communication unit that performs wireless communication with a plurality of base stations by selecting one of a plurality of frequencies that enables packet transmission / reception. And a control unit that switches the frequency used by the communication unit to execute the wireless communication. The control unit requests a handoff candidate frequency search process during the data transmission process by the communication unit. When a signal indicating a search request to be received is received, a specified search time is specified based on the search request, it is determined whether transmission of data being transmitted is completed within the specified search time, and transmission is performed within the specified search time. When the data transmission is completed, search processing is performed after the data transmission is completed, and when the data transmission is not completed within the specified search time, the data transmission is interrupted and the search processing is performed. [0010] Preferably, the information processing apparatus includes a storage unit, and the control unit transmits the data stored in the storage unit when the signal indicating the search request is received. A time required for transmission of the transmission data is calculated from the data amount of the transmission data and the current transmission rate in the communication unit, and it is determined whether the transmission is completed within the specified search time.

[0011] Preferably, when the transmission of data when the signal indicating the search request is received is reception of data by the communication unit, the control unit preferably receives the data force that has already been received. Obtains information on the amount of data being received, calculates the remaining reception time from the data amount of the data being received and the current reception rate in the communication unit, and whether transmission is completed within the specified search time judge.

[0012] Preferably, when a signal indicating the search request is received, the control unit is a periodic search request that requests the search request to report a result of performing a periodic search process. If it is the periodic search request, the periodic information specified in the periodic search request is extracted, and the search specified time is determined based on the periodic information. .

[0013] Preferably, when a signal indicating the search request is received, the control unit is a periodic search request that requests the search request to report a result of periodically performing a search process. If it is not the periodic search request, the search processing is performed by interrupting the completion of data transmission when the search request is received without specifying the search specified time.

[0014] Preferably, the data being transmitted includes a plurality of consecutive packets, and when the control unit interrupts data transmission to perform the search process, transmission of the packet being transmitted is not performed. After completion, control is performed to stop transmission of subsequent packets.

[0015] A second aspect of the present invention is a wireless communication terminal that performs wireless communication with a plurality of base stations, a frequency power that is currently being communicated, and a communication channel that is switched to another frequency to continue the wireless communication. A search request receiving step for receiving a signal indicating a search request, and a search request receiving step during transmission of data. Search specified time A specified time specifying step for specifying the data, a search process after the completion of the data transmission, a search step after the transmission is completed, a transmission interrupted search step for interrupting the data transmission and performing the search process, and the specified time specifying step. A completion determination step for executing a search step after the completion of transmission when transmission of data being transmitted is completed within the specified search time, and executing the transmission interruption search step when not completed.

[0016] A wireless communication system according to a third aspect of the present invention includes a plurality of base stations and a wireless communication terminal that performs wireless communication with the plurality of base stations. A communication unit that performs wireless communication by selecting one of a plurality of frequencies that enables transmission and reception, and a control unit that performs the wireless communication by switching a frequency used by the communication unit, When the communication unit receives a signal indicating a search request for requesting search processing of a handoff candidate frequency while the communication unit is transmitting data, the control unit specifies a specified search time based on the search request, It is determined whether transmission of data being transmitted within the specified search time is completed. If transmission is completed within the specified search time, a search process is performed after the transmission of the data is completed. The day If the transmission is not completed performing the search processing by interrupting transmission of the data.

The invention's effect

[0017] According to the present invention, it is possible to suppress the influence of instantaneous interruption as much as possible in hard handoff.

Brief Description of Drawings

FIG. 1 is a system configuration diagram showing a wireless communication system to which a wireless communication terminal according to an embodiment of the present invention is applied.

[FIG. 2] FIG. 2 is a diagram for explaining a typical sequence of a radio communication system when performing a MAHHO operation.

FIG. 3 is a flowchart for explaining an operation of handoff candidate frequency search when MAHHO is used.

FIG. 4 is a block diagram showing a configuration example of a signal processing system of the wireless communication terminal according to the embodiment of the present invention.

FIG. 5 is an external view of a mobile phone as a mobile terminal device according to an embodiment of the present invention. It is a perspective view which shows an example.

FIG. 6 is a flowchart for explaining the operation of the radio communication terminal according to the embodiment of the present invention.

FIG. 7A to FIG. 7C are diagrams for explaining the operation of the radio communication terminal according to the embodiment of the present invention, showing the relationship between the packet and the scheduling of the search operation.

FIG. 8A to FIG. 8D are diagrams for explaining the operation of the radio communication terminal according to the embodiment of the present invention, showing the relationship between the packet and the scheduling of the search operation.

FIG. 9A and FIG. 9B are diagrams for explaining the operation of the radio communication terminal according to the embodiment of the present invention, and showing the relationship between the packet and the scheduling of the search operation.

Yes

Explanation of symbols

[0019] 1 ... Wireless communication system, 10 ... Wireless communication terminal, 11 ... Communication part, 12 ... Control part, 13 ...

Storage unit, 14 Audio processing unit, 15 Speaker (SP), 16 Microphone (MIC), 17 Display unit, 18 Operation unit, 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, 20 ..., base station.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0021] First, a communication system to which the radio communication terminal according to the embodiment of the present invention is applicable will be described.

[0022] In CDMA2000 lx (Code Division Multiple Access 2000 lx), one base station has one or more sectors divided by a pilot code, each sector performs communication, and a wireless communication terminal It will communicate with the base station using that channel. Below, it is easy to use an example where one pilot code is associated with one base station (that is, only one channel is assigned to each base station). I will explain.

[0023] Specifically, the currently communicating base station outputs a list of neighboring base stations, and the radio communication terminal receives this and receives the signal strength of the pilot signal with each base station in the list. Measure. The result is transmitted to the base station with which the wireless communication terminal is currently communicating, and the base station determines the handoff destination base station based on this result. As a result, the base station takes the initiative in changing frequency bands (communication system transition)!

[0024] In the CDMA2000 lx system, which is one of the IMT—2000 standards, DAHHO (Data Assisted Hard Hand Off) and MAHHO (Mobile Assisted Hard Hand Off) are available for hard handoff. It is.

[0025] Each will be described below.

DAHHO is a method in which a wireless communication terminal (for example, a mobile terminal) performs a handoff to a second base station directly designated by the first base station without performing a search for other frequencies before the handoff. .

In DAHHO, since the first base station unilaterally designates the second base station without referring to the information of the radio communication terminal (mobile terminal), the radio communication terminal designates the first base station. The guarantee that the second base station can be acquired is relatively unlikely to fail a handoff.

On the other hand, in MAHHO, a wireless communication terminal receives a list of neighboring base stations (channels) in different frequency bands designated from a first base station that is currently communicating, and receives a service from the first base station. Switch to the specified list frequency for a moment and search for a base station (channel) in the list.

In searching for a base station in the list, the wireless communication terminal measures the energy intensity of the pilot signal with all the base stations (channels) in the list.

The wireless communication 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 reports the reported energy intensity. Based on the base stations in the list, the second base station is determined.

Then, an instruction for switching communication to the second base station is transmitted to the wireless communication terminal, and the wireless communication terminal executes handoff according to this instruction.

FIG. 1 shows a wireless communication system to which a wireless communication terminal according to an embodiment of the present invention is applied. FIG.

As shown in FIG. 1, the wireless communication system 1 includes a wireless communication terminal 10, a base station 20, a communication network (communication network) 30, and a server device 40.

As shown in FIG. 1, the wireless communication terminal 10 according to the present embodiment requests desired data from the server device 40 via the communication network 30 via the base station 20 by the wireless communication unit. In addition, it has a function of displaying information such as Web data acquired via the base station 20 in response to the request on the display unit.

In the present embodiment, a mobile phone will be described as an example of a wireless communication terminal. In this embodiment, a mobile phone is illustrated as an example of the wireless communication terminal. However, the present invention can also be applied to other wireless communication terminals.

[0030] In recent years, in the wireless communication system 1, the frequency band to be used is effectively utilized, and the reorganization of the frequency band has been studied in order to match the used frequency to the global standard specification. For example, the wireless communication system using CDMA2000 lx Currently, in Japan, the 800 MHz band with Japanese specifications (hereinafter, the current 800 MHz band) is used. This frequency band will be reorganized into the new 800MHz band, which is a global standard specification.

In the current 800 MHz band and the new 800 MHz band, the frequency band to be used is uplink (communication from the wireless communication terminal 10 to the base station 20 side) and downlink (communication from the base station 20 side to the wireless communication terminal 10). The frequency allocation is different!

Against this background, multi-band wireless communication terminals capable of communication in the current frequency band (current 800 MHz) and new frequency band (new 800 MHz) have been developed! In addition to these frequency bands, wireless communication terminals that can communicate in higher frequency bands (2 GHz) have also been developed.

The multiband wireless communication terminal 10 performs wireless communication with the base station 20 via a channel assigned by the base station 20. At this time, the radio communication terminal 10 can transmit and receive radio signals in a plurality of frequency bands. Specifically, the wireless communication terminal 10 can transmit and receive wireless signals using the current frequency band (current 800 MHz), the new frequency band (new 800 MHz), and the high frequency band (2 GHz). Show. [0032] In the communication systems of different frequency bands described above, 3GPP2 (3rd Generation Partnership Project 2) is specified as an identification number for identifying the frequency band between the base station 20 and the radio communication terminal 10. Band classes are granted.

For example, in the neighboring base station list in the information broadcast from the base station 20 to the wireless communication terminal 10, this band class is used for notifying the communication system existing around the wireless communication terminal 10. .

The current frequency band (current 800 MHz) is classified as band class 3, the new frequency band (new 800 MHz) is classified as band class 0, and the high frequency band (2 GHz) is classified as band class 6.

[0033] Hereinafter, a handoff method in a radio communication terminal and a radio communication system according to an embodiment of the present invention will be described.

FIG. 2 is a diagram for explaining a typical sequence of the wireless communication system in the case where the above-described MAHHO operation is performed as an example of hard handoff.

FIG. 3 is a flowchart for explaining the handoff candidate frequency search operation when MAHHO is used.

First, referring to FIG. 2, when the wireless communication terminal 10 performs communication using the base station 20 (base station A), the MAHHO operation is performed on the base station 20 (base station with a different frequency). A typical sequence of the wireless communication system in the case of performing will be described.

[0036] As described above, MAHHO is a CDMA base station 20 power S, a radio communication terminal that becomes a mobile station.

This is a method of determining the base station 20 of the hard handoff destination based on the energy intensity of the base station measured by 10 and has the effect of increasing the success rate of the hard handoff between frequencies and making it difficult to cause call disconnection. .

MAHHO is the pilot signal strength measurement result reported from the radio communication terminal 10

Since PPS MM (Periodic Pilot Strength Measurement Message) is monitored and handoff starts when the station's energy strength falls below a certain level, it is called PPSMM based.

Specifically, in FIG. 2, the base station 20 (base station A) makes a PPMRO (Periodic Pilot Measurement Request Ord) which is a pilot signal strength measurement request to the radio communication terminal 10. er) (ST101), and requests to report the energy intensity of the local station received by the wireless communication terminal 10 periodically.

In response to this, the non-spring communication terminal 10 sends a PPSMM (Periodic Pilot Strength Measurement Message) to the base station 20 and reports the energy intensity in the base station 20 (ST102).

Reports are sent periodically at intervals specified by the previous PPMRO (0.8-10.08 seconds, eg 2-4 seconds). However, only when the threshold is specified by PPMRO, the wireless communication terminal 10 is exempted from reporting for the purpose of avoiding traffic congestion while the threshold is not met.

Yes

[0038] Next, the base station 20 (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, base station 20 (base station A) sends a handoff candidate search request message (CFSRQM: Candidate Frequency Search Request Message) to radio communication terminal 10 (ST103). Communicate parameters such as handoff candidate system frequency, base station list, search window size, search interval, and threshold.

Here, one of important parameters is a search type. The search type indicates one of three levels: “0 = stop search”, “1 = start single search”, and “3 = start regular search”.

“0 = stop search” can be used when only the information of various parameters is passed to the wireless communication terminal 10 and the actual search is stopped without being performed. “1 = Start single search” can be used when the wireless communication terminal 10 performs a search only once and reports the result. “3 = Start periodic search” can be used to cause the mobile station to periodically search and report the results periodically.

[0040] The network uses the power S to properly use three search types according to traffic conditions and geographical conditions.

[0041] Subsequently, the wireless communication terminal 10 sends a handoff candidate search J heart answer message (CFs ^ iVL Candidate Frequency Searcn Response Message) to the base station 20 (base station B) and accepts CFSRQM. Tell (ST104). In response to this, base station 20 (base station B) sends a CFSCNM (Candidate Frequency Search Control Message) to radio communication terminal 10 and designates the search type as “1 = single search start” (ST105 ).

Here, unlike CFSRQM, no parameters other than the search type are carried, so the effect on traffic is negligible. If parameters such as frequency and pilot list of handoff candidate systems are fixed and do not change much, the network will only have a negative impact on traffic if only the search type needs to be changed. CFSCNM can be used as given.

[0042] Next, the wireless communication terminal 10 issues a handoff candidate search report message (CFsRPM: Candidate Frequency Searcn Report Message) to the base station 20 (base station A), and the candidate system specified by GFSRQM Report pilot measurement results (ST10

6). 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 is reported at this time, the base station 20 (base station A) can request the radio communication terminal 10 to perform handoff. If the handoff condition is not satisfied, base station 20 (base station A) continues to send CFSRQM and designates the search type as “3 = Start periodic search” (S 1

07).

Subsequently, the wireless communication terminal 10 sends a handoff candidate search and an answer message to the base station 20 (base station A), and notifies that the CFSRQM has been accepted by issuing an answer message (FcsRcsM: andidate Frequency Search Response Message) ( ST108).

[0043] Radio communication terminal 10 sends CFSRPM to base station 20 (base station A), and periodically reports the measurement results of pilots of candidate systems specified by CFSRQ M (ST109). At this time, a candidate frequency search (CFS) is performed.

Reports are sent periodically at the search cycle specified by CFSRQM (0.48 to 200 seconds, for example, 2 to 4 seconds as an example). However, only when the threshold value is specified by CFSRQM, the wireless communication terminal 10 is exempted from reporting in order to avoid traffic congestion while the threshold value is not satisfied.

Base station 20 (base station is wireless A handoff request message (UHDM: Universal Hand Off Direction Message) is transmitted to communication terminal 10, and a handoff request is made to base station 20 (base station B) of the candidate frequency (ST110).

The wireless communication terminal 10 performs the handoff as specified, sends a handoff completion message (EHOCM: Extended Hand Off Completion Message) to the new base station 20 (base station B), and the MAHHO operation is completed ( ST111).

[0044] As described above, MAHHO refers to the frequency from the currently used frequency to another frequency while the radio communication terminal 10 is communicating with a single base station 20 (base station A). This is a handoff method in which the signal strength of the pilot signal is switched and the search is performed from another base station 20 (base station B) and the communication is switched to the base station 20 having the strongest signal strength.

Therefore, since frequency switching occurs during 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, for example, data is interrupted every 2 to 4 seconds. Transmission / reception efficiency (throughput) decreases due to retransmission.

Specifically, as shown in FIG. 3, radio communication terminal 10 transmits a CFSRQM of search type = 3 from base station 20 and starts searching for a handoff candidate frequency (ST 201 First, transmission is stopped (ST202).

Next, radio communication terminal 10 switches to the candidate frequency and executes a base station search of the candidate frequency (ST203, ST204), and switches to the original frequency and resumes transmission (ST205, ST206). Then, the radio communication terminal 10 reports the handoff candidate frequency search result to the requested base station 20 as a CFS RPM (ST207).

For this reason, if data is being transmitted when transmission is stopped as described above, the data will be destroyed, and it will be necessary to retransmit the data when transmission is resumed. Also, if the frequency is switched during data reception, the data being received at that time will be destroyed, and it will be necessary to acquire the data again by sending a re-transmission request, resulting in a decrease in throughput. [0046] For this reason, the radio communication terminal according to the embodiment of the present invention to be described below is accompanied by frequency switching! / The start timing of search processing for measuring signal strength is a packet that is a transfer unit. By consciously making decisions, it is possible to reduce data destruction and avoid deterioration of data transfer efficiency during hard handoff execution.

The search processing start timing is a packet boundary or triggered by a drop in throughput. Details will be described below.

Here, a functional block of a signal processing system in a mobile phone is illustrated as the wireless communication terminal 10.

As shown in FIG. 4, the wireless communication terminal 10 includes a communication unit 11, a control unit 12, a storage unit 13, a voice processing unit 14, a speaker (SP) 15, a microphone (MIC) 16, a display unit 17, and an operation unit. Part 18.

[0049] The communication unit 11 transmits and receives radio signals to and from the base station 20 via a channel assigned by any of the base stations 20.

The communication unit 11 can transmit and receive wireless signals in a plurality of frequency bands. For example, the communication unit 11 can transmit and receive radio signals using the current frequency band (current 800 MHz band), the new frequency band (new 800 MHz band), and the high frequency band (2 GHz band). Is possible.

[0050] Note that, as described above, 3GPP 2 (3rd Generation Partnership) is used as an identification number for identifying a frequency band between the base station 20 and the radio communication terminal 10, as described above. For example, in the information broadcast from one base station 20 to the wireless communication terminal 10 in the neighboring base station list (N-list), the wireless communication terminal 10 This band class is used to notify the wireless communication terminal 10 of communication systems existing in the vicinity.

[0051] The current frequency band (current 800 MHz band) is band class 3, and 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.

In addition, the band classes and priorities described here are merely examples, and greatly depend on the infrastructure deployment status of the telecommunications carrier.

[0052] The communication unit 11 identifies a frequency band at the time of communication with the base station 20 based on the band class described above.

The control unit 12 controls the operation of the wireless communication terminal 10.

Specifically, the control unit 12 outputs an audio signal (audio data) included in the signal output from the communication unit 11 to the audio processing unit 14 and communicates the audio signal output from the audio processing unit 14. Output to part 11.

In addition, the control unit 12 controls which of the above-described plurality of frequencies is used for transmission / reception of 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 20. Is executed.

Handoff is a process of switching the communication target from the currently communicating base station 20 to another base station, that is, performing a transition between channels.

[0054] When the communication unit 11 receives a search request for a handoff candidate frequency from the base station 20 with which the communication unit 11 is communicating, the control unit 12 switches from the currently used frequency to the handoff candidate frequency and performs an acquisition operation. Control is performed so that a handoff candidate frequency search is executed when transmission of a packet in transmission or reception of a packet in reception of a continuous transmission packet sequence or reception packet sequence is completed.

Therefore, as shown in FIG. 4, 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, and a pilot signal strength measurement unit. 124, a frequency setting unit 125, a transmission / reception data amount acquisition unit 126, a transmission / reception rate prediction calculation unit 127, a transmission / reception completion time prediction calculation unit 128, a timer 129, and a comparison calculation unit 130.

[0056] The message exchange unit 121 transmits a MAHHO message between the wireless communication terminal 10 and the base station 20. Various messages (PPMRO, PPSMM, CFSR) shown in Figure 2

QM, CFSRSM, CFSCNM, CFSRPM, CFSRSM, CFSRPM, UHDM, EH

Replace OCM).

The message exchange unit 121 includes, among various messages, the frequency of the handoff candidate communication system attached to the search request message (CFSRQM) transmitted from the base station 20, the base station list, the search window size, the search interval, the search type, the threshold, etc. These parameters are stored in the parameter storage unit 122.

[0057] The parameter storage unit 122 is actually allocated to a predetermined area of the storage unit 13, and the parameters are held here.

[0058] The search control unit 123 controls the parameter storage unit under the control of the handoff processing unit 120.

Based on the various parameters held in 122, a pilot search is performed for neighboring base stations 20 during communication and base stations 20 that are switched during hard handoff.

Here, “pilot search” refers to processing for setting a search window and searching for pilot channels 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 20, more specifically, the signal strength for each channel divided into pilot signals, and can be received by the communication unit 11. Measure the strength of the channel signal to be used.

There is a method of measuring the energy intensity of the pilot signal as a method of signal strength measurement.

, Here's how to measure the signal strength!

[0060] 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.

Yes

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. The transmission / reception rate is a handoff measured by the pilot signal strength measurement unit 124. It is estimated from the signal strength of the candidate frequency.

[0062] In addition to the prediction calculation result of the remaining transmission / reception data amount, the comparison calculation unit 130 is supplied with specified time data required for one search process, which is monitored by the timer 129. In the comparison calculation unit 130, the result compared with the transmission / reception completion time generated by the transmission / reception completion time prediction calculation unit 128 is supplied to the handoff processing unit 120.

Here, the comparison operation unit 130 mainly targets acquisition processing at a fixed period of search type = 3, so even if the current search is delayed until the next incoming search period, it is currently being transmitted / received. It is determined whether or not transmission / reception of the packet can be completed.

[0063] When the handoff processing unit 120 receives a handoff request message (UHDM) from the base station 20 as well, 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. Specifically, the handoff processing unit 120 analyzes the handoff request message (UHDM), and performs handoff processing (separate soft handoff and hard handoff) and frequency allocation. The pilot PN code sequence, search window information, etc. are specified.

[0064] In addition, the handoff processing unit 120 controls each of 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 to perform handoff. Execute the process.

Specifically, the handoff processing unit 120 receives a search request for a handoff candidate frequency from the base station 20 with which the communication unit 11 is communicating. When the handoff processing unit 120 switches to the currently used frequency power handoff candidate frequency and performs an acquisition operation, the handoff processing unit 120 is transmitting or receiving a transmission packet in a continuous transmission packet sequence or reception packet sequence. When the reception of the packet is completed, a handoff candidate frequency search is performed.

It should be noted that the functions of each of the blocks 120 130 described above are achieved by executing the respective programs stored in the storage unit 13 by the control unit 12, However, it does not indicate only what is built in separately from other blocks, but is simply a representation of each processing unit for the sake of simplicity. The storage unit 13 stores various data used for processing in the control unit 12. The storage unit 13 includes, 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 e-mail address of a communication partner, an audio file for playing a ringtone or an alarm sound, a standby It holds screen image files, various setting data, and temporary data used in the program processing.

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 an audio signal received by the communication unit 11 and output from the speaker 15 or an audio signal input from the microphone mouthphone 16.

That is, the audio processing unit 14 amplifies the audio input from the microphone 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. To do.

In addition, the audio processing unit 14 performs signal processing such as decoding, digital-analog conversion, and amplification 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 speaker 15.

[0068] The display unit 17 is configured using a display device such as a liquid crystal display panel or an organic EL (Electro-Luminescence) panel, and displays an image corresponding to the video signal supplied from the control unit 12. .

The display unit 17 displays various information such as the phone number of the callee at the time of outgoing call, the phone number of the incoming callee at the time of incoming call, the contents of received mail or outgoing mail, date, time, remaining battery level, success / failure of outgoing call, standby screen, etc. Display information and images.

[0069] 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. When these keys are operated by the user, the operation unit 18 generates a signal corresponding to the operation content, and inputs the signal to the control unit 12 as a user instruction.

FIG. 5 is a perspective view showing an external configuration example of a mobile phone as the mobile terminal device according to the embodiment of the present invention. In FIG. 5, the key layout is mainly shown. [0071] As shown in FIG. 5, mobile terminal device 10A is configured as a so-called foldable mobile phone, and is a transmitter that is rotatably connected between an open state and a closed state. A case 50 and a receiving case 60 are provided.

The transmitting case 50 and the receiving case 60 are connected to each other by a connecting portion 70 that is the center of relative opening / closing operation of each other, thereby forming a case of the entire portable terminal device.

[0072] The transmission case 50 is provided with an operation input unit 12 in which various keys exposed on the front surface are arranged. In addition, the receiving case 60 is provided with a display unit 17.

In the operation input unit 12 of the transmitting case 50, for example, a numeric keypad 12a, a cursor key 12b, a function key 12c, and the like are arranged as various keys.

Each of the numeric keypads 12a is assigned a plurality of characters related to kanji, alphanumerics, kana, and symbols.

The effective characters intended by the numeric keypad 12a are switched by a toggle operation using the “input mode change key (specific key)” assigned to one of the function keys 12c. Assigned as an operation key for giving instructions.

This operation key may be assigned to a side key (not shown) installed on the side surface of the transmission case.

Next, an operation example of the wireless communication terminal 10 in FIG. 4 will be described.

[0074] FIG. 6 is a flowchart cited for explaining the operation of the radio communication terminal according to the embodiment of the present invention. FIGS. 7A to 7C and FIGS. 8A to 8D are diagrams illustrating the relationship between the packet and the search process scheduling, which are cited for explaining the operation of the wireless communication terminal according to the embodiment of the present invention. . 7A to 7C show the case where the transmission ends within the specified time, and FIGS. 8A to 8D show the case where the transmission does not end within the specified time. Hereinafter, the operation of the radio communication terminal according to the embodiment of the present invention shown in FIG. 4 will be described in detail in association with FIG. 6, FIG. 7A to FIG. 7C, and FIG. 8A to FIG.

Here, depending on the conditions when the search request (CFSRQM) is received, the capture processing operation ( An example of inter-packet search processing that changes the processing up to CFS) will be explained 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, the report needs to be returned to the base station 20 only once, and the search for the handoff candidate frequency required for this is limited to about once or twice. For this reason, the loss in the case of a single search request is the same as the data loss due to radio quality degradation during communication and does not cause much problem, so it is excluded from the search operation control 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. 6, the wireless communication terminal 10 receives CFSRQM of search type = 3 that needs to periodically execute a handoff candidate frequency search from the base station 20 during data communication (during transmission of a packet sequence). And At this time, the radio communication terminal 10 performs a search scheduling for the handoff candidate frequency S, and at that time, performs search scheduling according to the following procedure.

[0076] First, at the timing when a search for a handoff candidate frequency is attempted, the wireless communication terminal 10 is currently transmitting data (transmits user data stored in the storage unit 13 that is not "NULL"). ) Is determined (ST301).

If data transmission is in progress (ST301 “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 remaining amount of data has been transmitted. judge.

Here, the handoff processing unit 120 confirms the size of the data to be transmitted with reference to the storage unit 13, and the transmission data remaining amount is determined by the difference between this and the amount already transmitted as a transmission packet. And the remaining transmission time of the continuous packets currently being transmitted is calculated (ST302). Furthermore, handoff processing section 120 determines whether or not the transmission time obtained as a result of this calculation is included in the specified time range of the handoff candidate frequency search (ST303).

[0077] Specifically, the remaining transmission time is calculated by the transmission / reception completion time prediction calculation unit 128. The data is obtained by acquiring data related to the remaining transmission data amount from the data amount acquisition unit 126 and dividing the acquired data by the predicted transmission / reception rate calculated by the transmission / reception rate prediction calculation unit 127.

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 is the specified time for the handoff candidate frequency search. Whether or not it is included in the range can be determined.

Here, comparison operation unit 130 is intended for a search request with a fixed period of search type = 3, and therefore ends transmission of the packet currently being transmitted until the next incoming search period. Even if this is done, it is determined whether or not the current search can be terminated. When receiving the search request (CFSRQM), the radio communication terminal 10 must report the search result based on the search period specified together with the search type 3. Therefore, when a search result report is requested every X seconds when a search request is received and it takes y seconds to transmit the search and the report, X seconds after receiving the search request. The search specified time is within the time “χ−y” seconds minus the second. In other words, if the time required for searching and reporting is very short, at least the time interval specified by the search cycle can be interpreted as the search specified time.

Here, when it is determined that it falls within the specified time range (ST303 “Yes”), the handoff processing unit 120 waits for the end of transmission of a continuous packet sequence, and completes transmission of all packets. After that, the search control unit 123 is controlled to execute the search process (ST304).

On the other hand, when the search process is executed after the transmission of all the packets is completed and it is determined that the time does not fall within the specified time (ST303 “No”), the handoff processing unit 120 transmits the packet as a data transfer unit. The search control unit 123 3 is controlled to perform the search process by interrupting data transmission between the packet being transmitted and the next consecutive transmission packet (ST305). At the boundary of, control is performed to stop temporary transmission of packets after the immediately following packet (ST306).

Next, it is determined whether radio communication terminal 10 is currently receiving a packet (receives user data from a currently communicating base station that is not “NULL”) (ST307). When receiving (ST307 “Yes”), if the remaining amount of received data is known, whether or not the specified time is violated even if a search is executed after the remaining amount of data has been received. , Is judged.

Here, handoff processing section 120 calculates the remaining reception time of continuous packets that are currently being transmitted (ST308), 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 (ST309).

Specifically, the handoff processing unit 120 calculates the remaining reception time by searching for information serving as a header portion of data received from a packet that has been received and extracting the total amount of data received. Alternatively, in the first place, when the operation unit 18 is instructed to start reception, information on data to be received is acquired from the server in advance and stored in the storage unit 13 and is currently being received by referring to this. The handoff processing unit 120 can predict the reception completion time by obtaining the total amount of data and calculating the remaining reception time from the reception rate predicted from the current reception status.

Then, by comparing the comparison operation unit 130 with the specified time based on the above-described search cycle monitored by the timer 129, the remaining reception time of the continuous packets currently being received is the specified time for the handoff candidate frequency search. The handoff processing unit 120 can determine whether or not it is included in the range by half IJ.

Here, when it is determined that it falls within the specified time range (ST309 “Yes”), the handoff processing unit 120 waits to receive a continuous packet sequence, and completes reception of all packets. The search control unit 123 is controlled to interrupt the data reception and execute the search process (ST310).

On the other hand, if the search process is executed after all reception is completed and it is determined that the time does not fall within the specified time (ST309 “No”), the current packet being received and The search control unit 123 is controlled so as to perform a search process between successive consecutive received packets (ST311).

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 ST312, the above handoff candidate frequency is searched and the original When the frequency is restored, the search result is reported (CFSRPM) (ST312). When reception is resumed and there is a suspended transmission packet (ST313 “Yes”), the handoff processing unit 120 performs communication. Transmission / reception is resumed by controlling the unit 11 (ST314).

[0081] Actual processing of radio communication terminal 10 according to the above-described embodiment of the present invention is shown as <Example 1> and <Example 2> in FIGS. 7A to 7C and FIGS. 8A to 8D.

In FIG. 7A to FIG. 7C, as described in relation to FIG. 6, the remaining amount of transmission data at the stage of receiving the search request in which the search type 3 is specified is completed within the specified search time. Shows the relationship between transmission / reception packets and search processing scheduling when the search is not completed within the specified search time.

First, as shown in FIG. 7A, when it is determined that the transmission is completed within the specified time at the stage where the search request is received, the transmission of the transmission data is awaited.

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 Fig. 7B. For this reason, the capture process is further waited until the reception of the receiving packet at the stage where the transmission is completed, and as shown in FIG. 7C, the reception is temporarily stopped and the search process is stopped when the reception of the packet being received is completed. And the reception of the reception data that has been stopped when the search process is completed is resumed.

[0082] <Example 2>

On the other hand, Fig. 8A to Fig. 8D show the relationship between packets and search processing scheduling when transmission does not end within the specified search time (Fig. 8A) and reception does not end within the specified search time (Fig. 8B). Indicates.

If it is determined that the transmission will not be completed within the specified time at the stage when the search request is received, as shown in Fig. 8C, there is a margin for the specified search time and wait for the transmission completion of the packet being transmitted. When the packet transmission is completed, the received data packet is still being received, and the search process is further waited until this reception is completed, and reception is completed when reception of the receiving packet is completed, as shown in FIG. 8D. Stop and execute the search process, and resume receiving data that was stopped when the search process was completed.

Note that in both FIG. 7C and FIG. 8D, the blocks indicated by hatched CFS are supported. Indicates the execution timing of the hitch process.

[0083] At this time, when waiting for completion of transmission of a transmission or reception packet so that the search process can be completed within the specified search time, at least allow time for the search process, Even when transmission is complete, the search process up to reporting the search results to the base station can be completed. 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, however, at least the time required for the search process is sufficient. It is necessary to have it.

[0084] If transmission is not performed at the timing at which a search for a handoff candidate frequency is attempted, the search schedule can be determined only by the reception status. In addition, the search process must be executed only in the packet environment up to now. Data could not be received by switching the frequency by monitoring the timing when the transmission / reception rate is low within the specified time range and executing the search process. Data loss can be minimized.

FIG. 9A and FIG. 9B show the relationship between the packet and the search process scheduling when no transmission is performed as <Example 3>. Here, both FIG. 9A and FIG. 9B show received data as an example. 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.

For example, the handoff processing unit 120 compares the reception (transmission) rate at the time of receiving a search request and a predetermined threshold value, and does not perform the search process until the level falls below these values. When it occurs, it waits for the completion of reception (transmission) of the packet that is being received (transmitting), performs search processing when reception (transmission) is completed, and then resumes reception (transmission) of the subsequent packet.

The reception (transmission) rate may be checked in steps ST303 and ST309 in FIG.

[0086] Thus, the reception (transmission) level is within a specified time range in which the search must be performed. Since the search process is executed in anticipation of the lowest timing of the route, it is possible to prevent a decrease in throughput due to the capture process.

In FIG. 9B, the blocks indicated by hatched CFS indicate the 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 search processing from the specified time, the search processing is performed so that the search processing is within the specified time regardless of the reception (transmission) rate Is to execute.

[0087] As described above, according to the wireless communication terminal 10 according to the embodiment of the present invention, the MAHHO operation during the data communication is executed, and the remaining amount of data to be transmitted is small within the search regulation range. If the data transmission 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 neglected and the data packet to be transmitted is transmitted. The packet is not retransmitted and the throughput is not reduced by MAHHO. In addition, if the data transmission is not completed within the specified search range where the remaining amount of data to be transmitted is large, the search for the handoff candidate frequency is performed by interrupting the data transmission. Even when data is transmitted, the search result report can always be performed in the specified cycle.

In other words, when the remaining size of the data being transmitted is small, periodic search result reports are performed without reducing the throughput! /, And the transmitted data size is large! /, In some cases, at least periodic search results can be reported reliably, so that it is possible to prevent a decrease in throughput due to MAHHO without interfering with MAHHO operation as much as possible.

[0088] 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. Therefore, the packet is not destroyed for the compensation frequency search, so that the throughput can be prevented from decreasing as much as possible.

[0089] Further, when the data transmission is reception, from the total amount of data received from the received data, and in the case of transmission, from the total amount of data transmitted from the transmission target data itself in the own device, the downlink or uplink Required to complete transmission / reception with reference to the data rate By specifying the time, it is possible to easily determine whether or not the transmission completion of the data being transmitted is within the search specified time, and whether or not to wait for the search processing to be completed.

Note that the flowchart shown in FIG. 6 shows the steps of the handoff method in the wireless communication system of the present invention in addition to the operations of the wireless communication terminal 10 or the base station 20 according to the embodiment of the present invention. Also show me!

That is, the handoff method according to the embodiment of the present invention switches the communication channel from the currently communicating frequency to another frequency in the wireless communication terminal 10 that performs wireless communication with a plurality of base stations 20. If the search request reception step (ST301) for receiving a search request for requesting search processing for a handoff candidate frequency and the search request reception step occur during data transmission, , A specified time specification step (ST303, ST309) for specifying the specified search time based on the received search request, a post-transmission search step (ST304, ST310) for performing search processing after data transmission is completed, and data If transmission interruption search steps (ST305, ST311) that perform search processing by interrupting transmission and a specified time specification step occur, transmission is in progress within the specified search time. Run the transmission completion search step in the case where transmission over data is completed, having a completion determination step (ST301 ~ST305, ST307~ST311) to perform the transmission interruption search step if it does not complete.

Note that the present invention is not limited to the above-described embodiment. That is, when implementing the present invention, various modifications, combinations, sub-combinations, and substitutions may be made for each component of the above-described embodiment within the technical scope of the present invention or an equivalent scope thereof. You may go. Further, in the above-described embodiment, the radio communication system capable of supporting three types of frequency bands of the current 800 MHz, new 800 MHz, and 2 GHz bands has been described, but the present invention is not limited to this. A wireless communication system that supports frequency bands other than the three types described above may be used, and the number of types of corresponding frequency bands is not limited to three, and any number may be used. Further, the force S described in the present invention using the embodiment based on MAHHO, the present invention is not limited to this, and can be applied to general hard handoff.

Claims

The scope of the claims

[1] A communication unit that performs wireless communication with a plurality of base stations 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, and

The controller is

When the communication unit receives a signal indicating a search request for requesting a handoff candidate frequency search process during data transmission processing, the search specified time is specified based on the search request and transmitted within the search specified time. It is determined whether transmission of medium data is completed. If transmission is completed within the specified search time, a search process is performed after transmission of the data is completed, and transmission of the data is completed within the specified search time. If not, the data transmission is interrupted and the search process is performed.

Wireless communication terminal.

[2] having a storage unit;

The controller is

When transmission of data when a signal indicating the search request is received is transmission of data stored in the storage unit, the data amount of the transmission data and a current transmission rate in the communication unit Calculate the time required to transmit the transmission data and determine whether transmission is completed within the specified search time.

The wireless communication terminal according to claim 1.

[3] The control unit includes:

When transmission of data when a signal indicating the search request is received is reception of data by the communication unit, information on a data amount of currently received data is acquired from data that has already been received, The remaining reception time is calculated from the data amount of the data being received and the current reception rate in the communication unit, and it is determined whether transmission is completed within the specified search time.

The wireless communication terminal according to claim 1.

[4] The control unit includes: When a signal indicating the search request is received, it is determined whether the search request is a periodic search request for requesting to report a result of periodically performing a search process, and the periodic search is performed. If it is a request, the periodic information specified in the periodic search request is extracted, and the specified search time is determined based on the periodic information.

The wireless communication terminal according to claim 1.

[5] The control unit includes:

When a signal indicating the search request is received, it is determined whether the search request is a periodic search request for requesting to report a result of periodically performing a search process, and the periodic search is performed. If it is not a request, the search processing is interrupted and the data transmission completion when the search request is received without specifying the specified search time is performed.

The wireless communication terminal according to claim 4.

[6] The data being transmitted includes a plurality of consecutive packets;

The controller is

When transmission of data is interrupted to perform the search process, control is performed to stop transmission of subsequent packets after transmission of the packet being transmitted is completed.

The wireless communication terminal according to claim 1.

[7] In a wireless communication terminal that performs wireless communication with a plurality of base stations, a handoff method for continuing wireless communication by switching a communication channel from the currently communicating frequency to another frequency,

A search request receiving step for receiving a signal indicating a search request for requesting a search process for a handoff candidate frequency;

A specified time specifying step for specifying a specified search time based on the search request when the search request receiving step occurs during data transmission;

A search step after completion of transmission for performing search processing after transmission of the data is completed, a transmission interruption search step for performing search processing by interrupting transmission of the data, and transmission within a specified search time specified in the specified time specifying step Medium data transmission A completion determination step of executing a search step after completion of transmission when transmission is completed, and executing the search step of transmission interruption when not completed;

A handoff method in a wireless communication terminal having

Multiple base stations,

A wireless communication terminal that performs wireless communication with the plurality of base stations, and

The wireless communication terminal is

A communication unit that performs wireless communication by selecting one of a plurality of frequencies enabling packet transmission and reception;

A control unit that switches the frequency used by the communication unit and executes the wireless communication,

The controller is

When the communication unit receives a signal indicating a search request for searching for a handoff candidate frequency during data transmission processing, the search specified time is specified based on the search request and transmitted within the search specified time. It is determined whether transmission of medium data is completed. If transmission is completed within the specified search time, a search process is performed after the transmission of the data is completed, and transmission of the data is completed within the specified search time. If not, the data transmission is interrupted and search processing is performed.

Wireless communication system.