WO2009084103A1

WO2009084103A1 - Transmission control method, radio base station, mobile station, and, control method

Info

Publication number: WO2009084103A1
Application number: PCT/JP2007/075283
Authority: WO
Inventors: Yoshiaki Ohta; Yoshihiro Kawasaki; Yoshiharu Tajima; Kazuhisa Obuchi; Yoshinori Tanaka; Katsumasa Sugiyama
Original assignee: Fujitsu Limited
Priority date: 2007-12-28
Filing date: 2007-12-28
Publication date: 2009-07-09
Also published as: JP5041007B2; JPWO2009084103A1

Abstract

In voice packet communication in a radio communication system, reduction in voice reproduction quality at handover is prevented. A buffer memory (11) buffers voice packet data (step S1). When a predetermined amount of voice packet data is buffered, a transmitting unit (12) starts to transmit by radio the voice packet data to a mobile station (20) (step S2). Thereafter, when handover to a radio base station (10a) is determined, all or two or more of the buffered voice packet data are transmitted by radio to the mobile station (20) (step S3). The mobile station (20) continues voice reproduction at predetermined voice reproduction timing according to the received voice packet data also during handover processing.

Description

Transmission control method, radio base station, mobile station, and control method

The present invention relates to a transmission control method, a radio base station, a mobile station, and a control method, and more particularly to a transmission control method, a radio base station, a mobile station, and a control method for wirelessly transmitting voice packet data.

Currently, in the field of mobile communication systems, communication systems employing CDMA (Code Division Multiple Access) as a multiple access method are in operation. On the other hand, next-generation mobile communication systems are being actively studied in order to realize higher-speed and stable wireless communication. For example, in 3GPP (3rd Generation Partnership Project), which has developed the specifications of a third generation mobile communication system, a new mobile communication system specification called LTE (Long Term Evolution) is discussed.

Incidentally, one of the communication services realized on the mobile communication system is voice packet communication that transmits voice as packet data. Voice packet communication is characterized in that packet data is generated intermittently. Therefore, in voice packet communication, it is conceivable to use Persistent Scheduling as a transmission control method. In Persistent Scheduling, a transmission cycle is first agreed between the radio base station and the mobile station. Then, the radio base station transmits voice packet data to the mobile station at the agreed cycle, and the mobile station decodes and reproduces the voice packet data at the agreed cycle.

In such voice packet communication, if transmission delay or packet loss occurs on the transmission path, there is a problem that the mobile station cannot decode and reproduce voice packet data at a desired cycle, and the voice reproduction quality deteriorates. On the other hand, techniques for suppressing the occurrence of transmission delay and packet loss include the following.

First, a buffer memory for absorbing jitter is provided in the mobile station so that voice packet data can be reproduced at a desired cycle even when there is a transmission interval fluctuation (jitter) caused by a change in the congestion state or the like. There exists a method (for example, refer patent document 1). Second, there is a method of predicting the occurrence of handover and performing possible setting changes in advance in order to suppress transmission delays caused by transmission path setting changes during handover (for example, Patent Documents). 2 and 3). Thirdly, in order to suppress the occurrence of packet loss at the time of handover, there is a method of transferring a packet arriving at the handover source radio base station to the handover destination radio base station (see, for example, Patent Document 4).
JP 2004-297591 A JP 2002-325275 A JP 2002-335553 A JP 2001-339552 A

However, the methods described in Patent Documents 1 to 4 still have a problem in that voice reproduction quality may be deteriorated due to delay in arrival of voice packet data to the mobile station at the time of handover. For example, in the method described in Patent Document 4, since packets are transferred between radio base stations, packet loss is suppressed, but arrival at a mobile station may not be in time for a desired reproduction timing.

The present invention has been made in view of these points, and an object thereof is to provide a transmission control method, a radio base station, a mobile station, and a control method that can suppress a decrease in voice reproduction quality during handover.

In order to solve the above-described problem, a transmission control method for a radio base station that wirelessly transmits voice packet data to a mobile station is provided. In this transmission control method, the acquired voice packet data addressed to the mobile station is stored in a buffer memory, and the voice packet data in the buffer memory is stored in a predetermined cycle after waiting for the voice packet data in the buffer memory to reach a predetermined amount. To sequentially wirelessly transmit to the mobile station. When it is determined that the mobile station performs handover to another radio base station, all or a plurality of voice packet data in the buffer memory are wirelessly transmitted to the mobile station. In the mobile station, the received voice packet data is stored until playback is performed at a predetermined voice playback timing.

According to such a transmission control method, after the voice packet data in the buffer memory reaches a predetermined amount, a process of wirelessly transmitting the voice packet data to the mobile station at a predetermined cycle is started. Then, when it is determined that the mobile station performs handover to another radio base station, all or a plurality of voice packet data in the buffer memory are wirelessly transmitted to the mobile station.

Also, in order to solve the above problems, a radio base station that wirelessly transmits voice packet data to a mobile station is provided. This radio base station has a buffer memory and a transmission unit. The buffer memory stores the acquired voice packet data addressed to the mobile station. The transmission unit waits for the voice packet data in the buffer memory to reach a predetermined amount, starts a process of sequentially wirelessly transmitting the voice packet data in the buffer memory to the mobile station at a predetermined cycle, and then the mobile station When it is decided to perform handover to another radio base station, all or a plurality of voice packet data in the buffer memory are transmitted by radio to the mobile station.

According to such a radio base station, after the voice packet data in the buffer memory reaches a predetermined amount, the transmitter starts processing to wirelessly transmit the voice packet data to the mobile station at a predetermined cycle. Then, when it is determined that the mobile station performs handover to another radio base station, all or a plurality of voice packet data in the buffer memory are wirelessly transmitted to the mobile station.

Also, in order to solve the above problems, a mobile station that receives voice packet data from a radio base station and plays back voice is provided. This mobile station has a receiving unit and a reproducing unit. When it is determined that the receiving unit performs handover to another radio base station while receiving voice packet data from the radio base station at a predetermined cycle, all or a plurality of radio base stations hold in the buffer memory. Voice packet data is received from the radio base station. Based on the voice packet data held in the buffer memory by the radio base station received by the receiving unit until the playback unit starts receiving voice packet data from another radio base station after the handover is determined. Audio playback is performed at a predetermined audio playback timing.

According to such a mobile station, when it is decided to perform handover to another radio base station, the receiving unit receives all or a plurality of voice packet data held in the buffer memory of the radio base station. The Then, after the handover is determined by the playback unit, until reception of voice packet data from another radio base station is started, a predetermined amount is determined based on the voice packet data held in the buffer memory of the radio base station. Audio playback is performed at the audio playback timing.

According to the above method or apparatus, it is possible to suppress a decrease in audio reproduction quality at the time of handover.
These and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments by way of example of the present invention.

It is a figure which shows this Embodiment. It is a figure which shows the system configuration | structure of a mobile communication system. It is a block diagram which shows the function of a radio base station. It is a block diagram which shows the function of a mobile station. It is a figure which shows the example of transmission of a buffering message. It is a figure which shows the other example of transmission of a buffering message. It is a flowchart which shows the procedure of packet transmission control. It is a flowchart which shows the procedure of the handover control of a movement origin radio base station. It is a flowchart which shows the procedure of the handover control of a movement destination radio base station. 5 is a flowchart illustrating a procedure for handover control of a mobile station. It is a sequence diagram which shows the flow of a handover control process. It is a figure which shows the 1st example of the flow of a packet. It is a figure which shows the 2nd example of the flow of a packet. It is a figure which shows the 3rd example of the flow of a packet. It is a flowchart which shows the other procedure of packet transmission control. It is a figure which shows the 4th example of the flow of a packet. It is a figure which shows the 5th example of the flow of a packet.

Hereinafter, the present embodiment will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing the present embodiment. The mobile communication system shown in FIG. 1 can transmit voice packet data wirelessly. This mobile communication system includes

radio base stations

10 and 10 a and a mobile station 20. Here, it is assumed that the current connection destination of the mobile station 20 is the radio base station 10.

The radio base station 10 includes a buffer memory 11 and a transmission unit 12. The buffer memory 11 buffers the acquired voice packet data addressed to the mobile station 20 (step S1). The transmission unit 12 waits for the voice packet data buffered in the buffer memory 11 to reach a predetermined amount (for example, a data amount equal to or greater than the data amount corresponding to N (N is a natural number greater than or equal to 2) voice packet data). After waiting, wireless transmission of voice packet data to the mobile station 20 is started (step S2). The voice packet data is transmitted by, for example, extracting voice packet data in order from the top of the buffer memory 11 (in the order of arrival) and transmitting the voice packet data at a predetermined cycle. When acquiring the voice packet data in an order different from the order of the voice packet data to be transmitted (reproduced), the buffer memory is used in order using the order information (sequence number, etc.) included in the voice packet data. The voice packet data may be extracted from 11 and transmitted.

Thereafter, when it is determined that the mobile station 20 performs a handover to the radio base station 10a, the transmission unit 12 receives voice packet data addressed to all the mobile stations 20 buffered in the buffer memory 11 or is buffered. The voice packet data addressed to a plurality of N (for example, more than the amount of data of two voice packet data) is wirelessly transmitted to the mobile station 20 (step S3). Here, the wireless transmission of the voice packet data after the handover decision may be performed at a timing according to the transmission schedule before the handover, or may be performed at an arbitrary timing that does not depend on the transmission schedule before the handover. Further, the buffered voice packet data may be transmitted all at once, or may be divided and transmitted multiple times. Furthermore, if it is difficult to transmit all voice packet data due to radio propagation conditions, only the voice packet data that can be transmitted may be transmitted.

The mobile station 20 has a receiving unit 21 and a reproducing unit 22. The receiving unit 21 wirelessly receives voice packet data transmitted by the radio base station 10 at a predetermined cycle. In addition, after the handover is determined, the receiving unit 21 wirelessly receives all the voice packet data buffered in the buffer memory 11. The reproduction unit 22 reproduces the voice packet data received by the reception unit 21 based on a predetermined timing. Here, the playback unit 22 does not receive the voice packet data received from the radio base station 10 after the handover decision by the receiving unit 21 until the reception of the voice packet data via the radio base station 10a is started after the handover decision. Playback is performed based on a predetermined timing.

According to such a mobile communication system, after the voice packet data buffered in the buffer memory 11 of the radio base station 10 reaches a predetermined amount, the transmission unit 12 starts radio transmission of the voice packet data. Then, the voice packet data is received wirelessly by the receiving unit 21 of the mobile station 20, and voice playback is performed by the playback unit 22. After that, when it is determined that the mobile station 20 performs handover to the radio base station 10a, all (or a plurality of N or two or more data quantities buffered in the buffer memory 11 by the transmission unit 12). Or the maximum possible voice packet data is transmitted wirelessly. Then, the voice packet data is received wirelessly by the receiving unit 21, and the voice reproduction is continuously performed by the reproducing unit 22 based on the voice packet data even before the handover is completed.

Thereby, it is possible to suppress delay of voice packet data arriving at the mobile station 20 at the time of handover. Therefore, the mobile station 20 can continuously reproduce the voice packet data at a desired cycle even during the handover, and the deterioration of the voice reproduction quality is suppressed.

The radio base station 10 may notify the radio base station 10a of the transmission schedule before the handover after the handover is determined. As a result, the radio base station 10a can smoothly take over the transmission processing of the voice packet data to the mobile station 20. Also, the radio base station 10, when the section where the voice packet data continuously arrives (sound section) and the section where the background noise packet data arrives continuously (silence section) appear alternately, Audio packet data may be buffered at each start. Further, the radio base station 10 may transmit a signal to that effect to the mobile station 20 when the background noise packet data first arrives after the sound period. Thereby, the mobile station 20 can switch the reception mode earlier.

[First Embodiment]
Hereinafter, a first embodiment will be described in detail with reference to the drawings.
FIG. 2 is a diagram showing a system configuration of the mobile communication system. The mobile communication system according to the first embodiment is a communication system that wirelessly transmits packet data. This mobile communication system includes

radio base stations

100, 100 a, 100 b,

mobile stations

200, 200 a, and an upper station 300.

The

wireless base stations

100, 100a, and 100b are wireless communication devices that can perform wireless communication with mobile stations that are within respective radio wave reachable ranges (cells). The

radio base stations

100, 100a, 100b are connected to the upper station 300 via a wired or wireless network. The radio base station 100 and the radio base station 100a are connected by a wired or wireless network. The

radio base stations

100, 100a, and 100b can transfer packet data acquired from the mobile stations in the cell to the upper station 300 and wirelessly transmit packet data acquired from the upper station 300. Further, the

radio base stations

100 and 100a can transfer packet data to an appropriate radio base station without passing through the upper station 300 at the time of handover.

The

mobile stations

200 and 200a are wireless terminal devices that can perform wireless communication with the

wireless base stations

100, 100a, and 100b. The

mobile stations

200 and 200a are, for example, mobile phones. The

mobile stations

200 and 200a can transmit and receive packet data to and from other mobile stations via the radio base station. Examples of packet data transmitted and received by the

mobile stations

200 and 200a include VoIP (VoiceVover Internet Protocol) packet data.

The upper station 300 is a relay device that manages the cell to which the

mobile stations

200 and 200a currently belong, and transfers the acquired packet data to an appropriate radio base station according to the destination of the packet. The upper station 300 corresponds to, for example, a packet switch arranged in the core network.

Note that another relay device may be installed between the

radio base stations

100, 100 a, 100 b and the upper station 300. Further, the radio base station 100 and the radio base station 100a may communicate with each other via the host station 300 instead of directly communicating with each other. Here, it is assumed that the mobile station 200 is currently receiving radio waves from the

radio base stations

100 and 100a and has the radio base station 100 as a connection destination, and the mobile station 200a has the radio base station 100b as a connection destination.

Next, module configurations of the radio base station 100 and the mobile station 200 will be described. The

radio base stations

100a and 100b can be realized by the same module configuration as the radio base station 100. Also, the mobile station 200a can be realized by the same module configuration as the mobile station 200.

FIG. 3 is a block diagram showing functions of the radio base station. The radio base station 100 includes a buffer memory 110, a switch 120, a scheduler 130, a transmission / reception unit 140, a transmission / reception antenna 150, and a control unit 160.

The buffer memory 110 is a memory for temporarily storing arrived VoIP packet data. The buffer memory 110 is provided with two storage areas. In one storage area, VoIP packet data received from the upper station 300 is stored. The other storage area stores VoIP packet data received from the radio base station 100a, which is an adjacent radio base station. The two storage areas may be realized by physically providing two memory devices, or may be realized by dividing the storage area of one memory device into two by software. The buffer memory 110 outputs the stored VoIP packet data to the switch 120 under the control of the control unit 160.

The switch 120 distributes the VoIP packet data output from the buffer memory 110 according to the transmission destination. If the VoIP packet data is wirelessly transmitted to the mobile station 200, the switch 120 outputs it to the scheduler 130. In the case of VoIP packet data transferred to the radio base station 100a or the upper station 300, the switch 120 outputs it to the corresponding wired or wireless network.

The scheduler 130 manages radio resources (transmission timing and transmission frequency band) used for radio communication with the mobile station 200. When the scheduler 130 acquires the VoIP packet data and other packet data output from the switch 120, the scheduler 130 specifies a radio resource used for transmission and outputs the packet data to the transmission / reception unit 140.

The transmission / reception unit 140 acquires packet data from the scheduler 130, and acquires various control information related to wireless communication from the control unit 160. Then, the transmission / reception unit 140 performs encoding / modulation of the packet data and the control information, and outputs them to the transmission / reception antenna 150. In addition, the transmission / reception unit 140 acquires a reception signal from the transmission / reception antenna 150 and performs demodulation / decoding. The packet data obtained here is taken in for transfer according to the destination, and the obtained control information is output to the control unit 160.

The transmission / reception antenna 150 is a transmission / reception antenna. The transmission / reception antenna 150 wirelessly transmits a transmission signal acquired from the transmission / reception unit 140. Further, the transmission / reception antenna 150 outputs a reception signal received from the mobile station 200 to the transmission / reception unit 140.

The control unit 160 controls the entire radio base station 100 based on various control information acquired from the mobile station 200, the radio base station 100a, and the upper station 300 and the transmission / reception status of packet data. Further, the control unit 160 outputs various control information to the mobile station 200, the radio base station 100a, and the upper station 300 as necessary. The control unit 160 includes a scheduler management unit 161, a measurement unit 162, a HO processing unit 163, and a buffer management unit 164.

The scheduler management unit 161 controls the scheduler 130 to manage the transmission schedule of packet data. In particular, the scheduler manager 161 instructs the scheduler 130 to perform Persistent Scheduling when starting VoIP packet communication with the mobile station 200. In Persistent Scheduling, only voice packet data for voice playback is transmitted continuously (sound zone, Talkspurt zone) and only background noise packet data for playback of background noise is transmitted continuously. For each section (silent section, silent section), radio resources having a predetermined period are reserved in a lump. The transmission period may be different between the voiced section and the silent section. In addition, the scheduler management unit 161 may perform rescheduling as necessary while VoIP packet communication is continued.

The measurement unit 162 collects measurement information (Measurement Report) indicating the radio quality of the communication link (downlink) from the

radio base stations

100 and 100a to the mobile station 200. The measurement information is received as control information from the mobile station 200. The measurement information includes, for example, CQI (Channel Quality Information).

The HO processing unit 163 continuously monitors the measurement information collected by the measurement unit 162 and determines whether or not the mobile station 200 needs a handover (HO: HandOver). For example, the HO processing unit 163 determines that the handover is necessary when the radio quality between the radio base station 100a and the mobile station 200 becomes better than the radio quality between the radio base station 100 and the mobile station 200. To do. The HO processing unit 163 transmits / receives various control information to / from the destination radio base station (for example, the radio base station 100a), the mobile station 200, and the upper station 300, and executes a handover process. On the other hand, if the radio base station 100 functions as a destination radio base station, the HO processing unit 163 executes various processes necessary for taking over radio communication from the source radio base station.

The buffer management unit 164 manages the VoIP packet data stored in the buffer memory 110. Specifically, the buffer management unit 164 causes the buffer memory 110 to buffer a predetermined amount of voice packet data at the start of the sound period. After that, the voice packet data addressed to the mobile station 200 is sequentially output to the switch 120 at a period (for example, a period of 20 ms) corresponding to the voiced section. Further, in the silent period, the background noise packet data addressed to the mobile station 200 is sequentially output to the switch 120 at a period corresponding to the silent period (for example, a period of 160 ms).

In addition, when the handover of the mobile station 200 is determined by the HO processing unit 163 during the sound period, the buffer management unit 164 stores all (or a plurality of N or two data amounts) stored in the buffer memory 110. The voice packet data addressed to the mobile station 200 (the above amount or the maximum possible transmission) is output to the switch 120. Note that the buffering amount at the start of the voiced section can be changed by setting. It is also possible to prevent the buffering at the beginning of a voiced section from being performed by setting.

FIG. 4 is a block diagram showing functions of the mobile station. The mobile station 200 includes a transmission / reception antenna 210, a transmission / reception unit 220, a buffer memory 230, a switch 240, a reproduction unit 250, and a control unit 260.

The transmission / reception antenna 210 is a transmission / reception antenna. The transmission / reception antenna 210 outputs a reception signal received from the

radio base stations

100 and 100 a to the transmission / reception unit 220. In addition, the transmission / reception antenna 210 wirelessly transmits a transmission signal acquired from the transmission / reception unit 220.

The transmission / reception unit 220 acquires a reception signal from the transmission / reception antenna 210, performs demodulation / decoding, and extracts packet data and control information addressed to the own station. Of the packet data obtained here, VoIP packet data is output to the buffer memory 230, and the obtained control information is output to the control unit 260. In addition, the transmission / reception unit 220 acquires packet data to be transmitted and also acquires control information to be transmitted from the control unit 260. Then, the transmission / reception unit 220 encodes / modulates the packet data and control information and outputs the encoded data to the transmission / reception antenna 210. In addition, when the transmission / reception unit 220 acquires VoIP packet data including a bit error from the switch 240, the transmission / reception unit 220 makes a retransmission request according to the acquired VoIP packet data.

Retransmission can also be performed before the next VoIP packet data transmission timing (for a voiced section, for example, transmission timing after 20 ms, for a silent section, for example, transmission timing after 160 ms).

The buffer memory 230 is a memory that temporarily stores the VoIP packet data output from the transmission / reception unit 220. The VoIP packet data stored in the buffer memory 230 is inspected by the controller 260 for bit errors. Then, under the control of the control unit 260, the VoIP packet data is sequentially output to the switch 240.

The switch 240 distributes the VoIP packet data output from the buffer memory 230 according to the presence or absence of a bit error. The VoIP packet data having no bit error is output to the reproducing unit 250. The VoIP packet data having a bit error is output to the transmission / reception unit 220 and subjected to retransmission control. In order to perform retransmission processing efficiently, VoIP packet data having a bit error may be left in the buffer memory 230, and may be combined with retransmission packet data (HARQ (Hybrid Automatic Repeat Request) combining).

The playback unit 250 has a buffer memory 251. The buffer memory 251 is a memory that temporarily stores VoIP packet data. The reproducing unit 250 stores the VoIP packet data acquired from the switch 240 in the buffer memory 251. In addition, the playback unit 250 sequentially extracts VoIP packets from the buffer memory 251 at a cycle corresponding to a voiced section or a silent section, decodes them, and performs voice playback (playout).

The control unit 260 controls the entire mobile station 200 based on various control information acquired from the

radio base stations

100 and 100a and the transmission / reception status of packet data. Further, the control unit 260 outputs various control information to the

radio base stations

100 and 100a as necessary. The control unit 260 includes a measurement unit 261, a retransmission request unit 262, a reproduction management unit 263, and an HO processing unit 264.

The measuring unit 261 continuously measures the radio quality of each downlink from the

radio base station

100, 100a to the mobile station 200. The radio quality can be measured, for example, by capturing a pilot signal that the

radio base stations

100 and 100a transmit regularly or irregularly. Then, the measurement unit 261 outputs the measurement information as control information to the currently connected radio base station (for example, the radio base station 100). This measurement information includes, for example, CQI.

The retransmission request unit 262 controls the retransmission request by the transmission / reception unit 220. Specifically, the retransmission request unit 262 checks whether there is a bit error in the VoIP packet data stored in the buffer memory 230, and controls to return the VoIP packet data to the transmission / reception unit 220 if there is a bit error. . Then, retransmission request section 262 outputs a retransmission request signal to transmission / reception section 220, and controls transmission / reception section 220 to make a retransmission request to the currently connected radio base station. Here, in the retransmission control, it is also possible to specify a bit range including an error and make a retransmission request, and have the packet data retransmitted limited to the bit range.

The playback management unit 263 controls audio playback by the playback unit 250. For example, the reproduction management unit 263 designates the timing for starting decoding / reproduction of VoIP packet data, and the decoding / reproduction period of VoIP packet data in each of the voiced and silent periods. It is also possible to perform control so that buffering is performed until the voice packet data reaches a predetermined amount at the start of the voiced section, and then decoding / playback of the voice packet data is started.

Upon receiving a handover instruction notification as control information from the currently connected radio base station, the HO processing unit 264 disconnects the link with the source radio base station and the link with the destination radio base station. Set up. Then, the HO processing unit 264 controls the transmission / reception unit 220 so as to resume packet communication via the destination wireless base station.

Here, when a handover decision is made during a voiced period, the transmitting / receiving unit 220 determines that all (or multiple N or two or more data quantities buffered in the source radio base station) Receive the maximum amount of voice packet data that can be transmitted wirelessly. The voice packet data is stored in the buffer memory 251. Therefore, even if reception of the voice packet data is interrupted from the determination of the handover to the restart of communication via the destination radio base station, the playback unit 250 can continue the voice playback at the originally scheduled period.

Next, details of processing executed in the mobile communication system having the above configuration will be described. In the following, a scenario is considered in which the mobile station 200 receives VoIP packet data from the mobile station 200a via the radio base station 100 and then performs handover to the radio base station 100a. Specifically, (1) message transmission / reception between the radio base station 100 and the mobile station 200 before the start of VoIP packet communication, (2) transmission control of VoIP packet data in the radio base station 100, (3) A description will be given of the order of handover control of each of the

radio base stations

100 and 100a and the mobile station 200.

FIG. 5 is a diagram illustrating a transmission example of a buffering message. The radio base station 100 wirelessly transmits a buffering message 141 as control information to the mobile station 200 before starting VoIP packet communication.

The buffering message 141 includes buffering instruction information (Buffering Indicator) and buffering amount information (Buffering Amount). The buffering instruction information is information indicating the presence / absence of buffering at the start of a voiced section by the radio base station 100 or the mobile station 200, and is represented by 1 bit, for example. The buffering amount information is information indicating how many packets of audio packet data are to be buffered, and is expressed by 2 to 3 bits, for example. For the presence / absence of buffering and the buffering amount, a fixed value may be used, or a value dynamically determined according to the communication status may be used.

Here, the meaning of the buffering instruction information can be interpreted in multiple ways. The radio base station 100 and the mobile station 200 agree in advance what the meanings of 0 and 1 in the buffering instruction information are. Three interpretation examples are given below. The first interpretation is that when 0, buffering at the mobile station 200 is indispensable, buffering at the radio base station 100 is optional, and when 1, buffering at the radio base station 100 is indispensable. The interpretation is that buffering is optional. The second interpretation is an interpretation that buffering at the radio base station 100 is essential, and buffering at the mobile station 200 is not performed when 0 and is performed when 1. FIG. The third interpretation is that buffering at the mobile station 200 is essential, and buffering at the radio base station 100 is not performed when 0, but is performed when 1.

In this way, the buffering situation of the radio base station 100 and the mobile station 200 is clarified, and each device follows it, so that excessive buffering is performed and the transmission delay between the mobile station 200 and the mobile station 200a is reduced. It is possible to prevent the sound reproduction quality from deteriorating due to an increase in size or insufficient buffering, and to perform optimization. Note that the presence / absence of buffering and the default value of the buffering amount may be set, and the buffering message may be transmitted / received only when different from the default value. Further, a buffering message including only one of the presence or absence of buffering and the buffering amount may be transmitted and received.

In this case, the buffering message 141 does not include the buffering instruction information but can include only the buffering amount information. The buffering amount information is information indicating how many packets of voice packet data are to be buffered, and is expressed by 2 to 3 bits, for example. For the presence / absence of buffering and the buffering amount, a fixed value may be used, or a value dynamically determined according to the communication status may be used.

Here, the buffering amount information can be interpreted in multiple ways. For example, what the meanings of 2 to 3 bits in the buffering instruction information have in advance is agreed between the radio base station 100 and the mobile station 200. Three interpretation examples are given below. The first interpretation is that when the buffering amount is a specified amount, only the amount of buffering at the mobile station 200 is essential and the buffering at the radio base station 100 is arbitrary, or the buffering at the radio base station 100 is It is interpreted that only the specified amount of the ring is essential and buffering at the mobile station 200 is arbitrary. The second interpretation is an interpretation that the buffering at the radio base station 100 is essential, and the buffering amount at the mobile station 200 is not performed when the buffering amount is 0, and only the specified amount is performed when it is not 0. The third interpretation is that buffering at the mobile station 200 is essential, and buffering at the radio base station 100 is not performed when 0 and only the specified amount is performed when it is not 0.

FIG. 6 is a diagram illustrating another transmission example of the buffering message. In the transmission example of the buffering message shown in FIG. 5, the radio base station 100 designates the presence / absence of buffering and the buffering amount for the mobile station 200, but conversely, the mobile station 200 The presence / absence of buffering and the buffering amount may be designated for 100. Here, before the start of VoIP packet communication, the mobile station 200 wirelessly transmits a buffering message 221 to the radio base station 100 as control information.

The meaning of the buffering message 221 is the same as the meaning of the buffering message 141 described above. However, the meanings of 0 and 1 in the buffering instruction information may be reversed. For example, 0 may mean buffering at the

radio base station

100, and 1 may mean buffering at the mobile station 200.

Next, transmission control of VoIP packet data in the radio base station 100 will be described. In the following description, it is assumed that the radio base station 100 performs buffering.
FIG. 7 is a flowchart showing a procedure of packet transmission control. In the following, the process illustrated in FIG. 7 will be described in order of step number.

[Step S11] The control unit 160 performs signaling related to persistent scheduling with the mobile station 200. For example, the control unit 160 performs radio resource setting processing in an RRC (Radio Resource Control) layer, and sets a modulation scheme in L1 (layer 1: physical layer) / L2 (layer 2: MAC (Medium Access Control) layer). Process. Then, the control unit 160 controls the scheduler 130 and the transmission / reception unit 140 so that the VoIP packet data can be transmitted.

[Step S12] The control unit 160 determines whether or not it is the start of a voiced segment, that is, whether or not the head of the voice packet data addressed to the mobile station 200 has arrived at the buffer memory 110. If it is the start of a sound section, the process proceeds to step S13. If it is not the start of the sound section, the process proceeds to step S15.

[Step S13] The control unit 160 waits for buffering of voice packet data addressed to the mobile station 200 in the buffer memory 110 in an amount (for example, 2 to 3 packets) specified by the buffering message.

[Step S14] When the buffering in step S13 is completed, the control unit 160 controls the buffer memory 110 to sequentially buffer the voice packet data in a cycle corresponding to a voiced period (for example, a cycle of 20 ms). Output. Thereby, intermittent and periodic wireless transmission of the voice packet data to the mobile station 200 is started. Thereafter, the process proceeds to step S12. The control unit 160 may rearrange the order as necessary instead of outputting the voice packet data in the order of arrival.

[Step S15] The control unit 160 determines whether or not it is the start of the silent period, that is, whether or not the head of the background noise packet data addressed to the mobile station 200 has arrived at the buffer memory 110. If it is the start of a silent section, the process proceeds to step S16. If it is not the start of the silent section, the process proceeds to step S17.

[Step S16] When the next order of transmitting background noise packet data is reached, the control unit 160 controls the buffer memory 110 so that the buffered background noise packet data has a period (for example, 160 ms) corresponding to the silent period. Cycle). As a result, intermittent and periodic wireless transmission of background noise packet data to the mobile station 200 is started. Thereafter, the process proceeds to step S12.

[Step S17] The control unit 160 determines whether or not the VoIP packet communication between the mobile station 200 and the mobile station 200a is completed. When the communication is finished, the transmission control of the VoIP packet data addressed to the mobile station 200 is finished. If the communication has not ended, the process proceeds to step S12.

In this way, the radio base station 100 performs Persistent Scheduling for disclosure of VoIP packet communication, and voice packet data is wirelessly transmitted at a period corresponding to a voiced period (for example, a period of 20 ms), and background noise packet data is Wireless transmission is performed at a period (for example, a period of 160 ms) corresponding to the silent period. The radio base station 100 starts radio transmission after buffering a predetermined amount (for example, 2 to 3 packets) of voice packet data at the start of a voiced section.

Next, handover control for each of the

radio base stations

100 and 100a and the mobile station 200 will be described.
FIG. 8 is a flowchart showing a handover control procedure of the source radio base station. In the following, the process illustrated in FIG. 8 will be described in order of step number.

[Step S21] The control unit 160 acquires measurement information indicating the radio quality between the

radio base stations

100 and 100a and the mobile station 200 from the mobile station 200 as control information.
[Step S22] The control unit 160 determines whether the mobile station 200 needs to perform handover to another radio base station (for example, the radio base station 100a) based on the measurement information acquired in step S21. If handover is necessary, the process proceeds to step S23. If there is no need for handover, the process proceeds to step S21 and waits for the next acquisition of measurement information. In the following description, it is assumed that the handover from the radio base station 100 to the radio base station 100a is determined.

[Step S23] The control unit 160 transmits a handover request to the radio base station 100a. The handover request includes, for example, information related to the mobile station 200 such as identification information of the mobile station 200 and QoS (Quality） of Service) requested by the mobile station 200. In the following description, it is assumed that handover to the radio base station 100a is permitted.

[Step S24] Upon receiving the permission response to the handover request transmitted in Step S23 from the radio base station 100a, the control unit 160 transmits schedule information about the voice packet data to the radio base station 100a. The schedule information includes, for example, the buffering amount of voice packet data, the time when the previous scheduling was performed, the time when the next rescheduling was scheduled, and the like.

The following four methods can be considered as the time notification method, for example. (1) Absolute time designation method: The time at which the previous scheduling was performed and the time at which the next scheduling was scheduled are designated by the absolute time provided by the source base station. (2) Relative time designation method: The time at which the previous scheduling was performed is designated by the absolute time of the source base station, and the time at which the next rescheduling is scheduled to occur will occur in seconds after the last scheduling. Is specified. (3) Subframe absolute number designation method: The subframe number of the source base station is designated as the time when the previous scheduling was performed, and the time when the rescheduling is scheduled to be performed next is also designated by the subframe number. . (4) Subframe relative number designation method: The subframe number of the source base station is designated as the previous scheduling time, and the previous scheduling was performed at the time when the next rescheduling was scheduled. Specify the number of subframes after the subframe. In the above case, the movement source base station and the movement destination base station may share the time and subframe deviation.

[Step S25] The control unit 160 outputs a handover instruction to the mobile station 200. The transmission / reception unit 140 wirelessly transmits the handover instruction output from the control unit 160 to the mobile station 200 as control information.

[Step S <b> 26] The control unit 160 stores all the buffered voice packet data addressed to the mobile station 200 (or more than a plurality of N or two data amounts or the maximum amount that can be transmitted). To output. At this time, it is expected that the buffer memory 110 stores voice packet data of about the buffering amount at the start of the voiced section (for example, within the range of the number of packets initially buffered plus or minus one). The transmission / reception unit 140 wirelessly transmits the voice packet data output from the buffer memory 110 to the mobile station 200.

Further, the transmitter / receiver 140 wirelessly transmits a signal indicating that voice packet data has been transmitted and the amount of transmitted voice packet data as an L1 / L2 control signal, as necessary. However, this control signal is not necessarily required when the mobile station 200 performs Blind 必ずしも Detection.

The control unit 160 transfers the buffered background noise packet data and the VoIP packet data addressed to the mobile station 200 that has arrived after the output processing to the radio base station 100a.

[Step S27] Upon receiving a resource release instruction from the radio base station 100a, the control unit 160 releases resources reserved for VoIP packet communication among the upper station 300, the radio base station 100, and the mobile station 200. .

In this way, the radio base station 100, which is the source radio base station, determines whether the handover is necessary and the destination radio base station based on the measurement information continuously acquired from the mobile station 200. . When the handover is determined, the radio base station 100 transmits schedule information used for taking over the VoIP packet communication to the destination radio base station, and all the buffering for the mobile station 200 is performed. (Or a plurality of N or two or more data amounts or the maximum amount of data that can be transmitted) is wirelessly transmitted. Thereafter, resources for transmitting VoIP packet data via the radio base station 100 are released.

Note that the transmission of the schedule information in step S24 can be performed simultaneously with the transmission of the handover request in step S23, and the radio base station 100a starts radio transmission of VoIP packet data after the handover request is transmitted. It can also be performed at any timing up to. The wireless transmission of the voice packet data in step S26 may be performed at an arbitrary timing after the handover response is received from the radio base station 100a until the mobile station 200 establishes synchronization with the radio base station 100a. it can. In the above description, whether to perform handover is determined based on the downlink radio quality, but the uplink radio quality may also be referred to.

FIG. 9 is a flowchart showing a handover control procedure of the movement-destination radio base station. In the following, the process illustrated in FIG. 9 will be described in order of step number. In the following, it is assumed that the radio base station 100a includes the control unit 160a as a module corresponding to the control unit 160 of the radio base station 100.

[Step S31] Upon receiving the handover request from the radio base station 100, the control unit 160a determines whether or not to permit the handover of the mobile station 200 based on information included in the handover request. Then, the control unit 160a responds to the radio base station 100 with the determination result. Hereinafter, a case where the handover is permitted will be described.

[Step S32] The control unit 160a receives schedule information from the radio base station 100. Then, the control unit 160a determines the buffering amount of voice packet data and the transmission start timing based on the scheduling information. For example, the control unit 160a can set the buffering amount notified by the schedule information to a maximum value that can be set, and can determine the actual buffering amount within a range below that.

[Step S33] In response to a request from the mobile station 200, the control unit 160a establishes synchronization with the mobile station 200 so that the VoIP packet communication is possible.
[Step S34] The control unit 160a reports to the upper station 300 that the mobile station 200 has completed handover from the radio base station 100 to the radio base station 100a. Thereby, in the upper station 300, the setting of the transmission path of the packet addressed to the mobile station 200 is changed.

[Step S35] Upon receiving a response to the handover completion report transmitted in Step S34 from the upper station 300, the control unit 160a performs control so that radio resources used for VoIP packet communication with the mobile station 200 are secured by Persistent Scheduling. To do.

[Step S36] The control unit 160a instructs the radio base station 100 to release resources for VoIP packet communication of the mobile station 200.
In this way, the radio base station 100a, which is the destination radio base station, sets the buffering amount of voice packet data and the transmission start timing based on the schedule information received from the source radio base station after the handover request. adjust. Then, the radio base station 100a transmits a handover completion report to the upper station 300, and changes the transmission path of VoIP packet data addressed to the mobile station 200. Thereby, the radio base station 100a can smoothly take over VoIP packet communication from the source radio base station.

The schedule information may be received at the same time as the handover request, or may be received at any timing after the handover request is received until wireless transmission of VoIP packet data is started.

FIG. 10 is a flowchart showing a procedure of mobile station handover control. In the following, the process illustrated in FIG. 10 will be described in order of step number.
[Step S41] The control unit 260 measures the radio quality of each downlink based on the received signals from the

radio base stations

100 and 100a. The measurement of radio quality is performed, for example, by capturing a pilot signal included in the received signal. And the control part 260 outputs the measurement information which shows a measurement result. The transmission / reception unit 220 wirelessly transmits this measurement information to the radio base station 100 as control information. Note that the transmission of measurement information is continuously performed, for example, at a cycle specified by the radio base station 100.

[Step S42] The control unit 260 determines whether or not a handover instruction is received as control information from the radio base station 100. If a handover instruction is received, the process proceeds to step S43. If a handover instruction has not been received, the process proceeds to step S41, and the next timing for transmitting measurement information is awaited.

[Step S43] The control unit 260 determines whether or not an L1 / L2 control signal indicating that voice packet data has been transmitted has been received. If the L1 / L2 control signal is received, the process proceeds to step S45. If the L1 / L2 control signal has not been received, the process proceeds to step S44.

[Step S44] The control unit 260 detects a signal corresponding to the voice packet data included in the received signal from the radio base station 100 by Blind Detection.
In Blind Detection, for example, for a received signal from the radio base station 100, voice packet data is extracted in order for a plurality of extraction method candidates from which voice packet data may be extracted, and voice packet data is extracted. If so, it is determined that the extraction method was an appropriate extraction method. Whether or not the voice packet data is extracted can be determined by checking whether or not the voice packet data matches the format of the predetermined voice packet data.

[Step S45] Based on the L1 / L2 control signal detected in step S43 or the detection result (determined extraction method) in step S44, the control unit 260 determines the voice packet data included in the received signal from the radio base station 100. The transmission / reception unit 220 is instructed to extract all. As a result, the voice packet data buffered in the radio base station 100 is stored in the buffer memory 251 of the reproduction unit 250.

[Step S46] The control unit 260 establishes synchronization with the radio base station 100a, which is the destination radio base station specified by the handover instruction received from the radio base station 100, so that the VoIP packet communication is possible. To do.

In this way, the mobile station 200 continuously transmits downlink radio quality measurement information to the radio base station 100. When handover is determined by the radio base station 100, all (or more than a plurality of N or two data amounts or maximum transmittable) voice packets buffered in the radio base station 100 Receive data wirelessly. Thereby, the mobile station 200 can continue the voice reproduction based on the voice packet data buffered in the radio base station 100 even if a handover occurs in a voiced section. Note that the buffered voice packet data may be received before a handover instruction.

FIG. 11 is a sequence diagram illustrating the flow of the handover control process. In the following, the process illustrated in FIG. 11 will be described in order of step number.
[Step S51] The mobile station 200 measures the radio quality between the

radio base stations

100 and 100a and transmits the measurement information to the radio base station 100.

[Step S52] The radio base station 100 determines a handover based on the measurement information received in step S51, and selects the radio base station 100a as a destination radio base station. Then, the radio base station 100 transmits a handover request to the radio base station 100a.

[Step S53] The radio base station 100a performs call admission control based on the handover request received in Step S52, and decides to permit the mobile station 200 to be accepted. Then, the radio base station 100a transmits a handover response to the radio base station 100.

[Step S54] The radio base station 100 transmits schedule information indicating a transmission schedule of the VoIP packet data of the mobile station 200 to the radio base station 100a.
[Step S55] The radio base station 100 instructs the mobile station 200 to perform a handover to the radio base station 100a.

[Step S56] The radio base station 100 transmits all the buffered voice packet data to the mobile station 200. At this time, the radio base station 100 also transmits a control signal indicating that the voice packet data has been transmitted and the amount of packets. Note that VoIP packet data arriving at the radio base station 100 thereafter is forwarded to the radio base station 100a according to the judgment of the base station 100, or discarded without being forwarded by the base station 100.

[Step S57] The mobile station 200 and the radio base station 100a establish a connection for VoIP packet communication.
[Step S58] The radio base station 100a transmits a handover completion report to the upper station 300.

[Step S59] The upper station 300 changes the transfer destination of the packet addressed to the mobile station 200 to the radio base station 100a based on the handover completion report received in Step S58. Then, the upper station 300 transmits a handover completion response to the radio base station 100a.

[Step S60] The radio base station 100a transmits a resource release instruction to the radio base station 100. The radio base station 100 releases resources reserved for transmission paths of the upper station 300, the radio base station 100, and the mobile station 200.

The transmission of voice packet data in step S56 may be performed between step S53 and step S57. Further, the transmission of the schedule information in step S54 may be performed from step S52 to when the radio base station 100a starts transmitting VoIP packet data (may be included in step S52 and transmitted).

Next, details of the timing for wirelessly transmitting buffered voice packet data will be described. There are a plurality of wireless transmission timings. Three specific examples are given below.

FIG. 12 is a diagram showing a first example of a packet flow. In the example of FIG. 12, the mobile station 200a transmits a voice packet including voice data (indicated by numerals 1 to 7 in the figure) at intervals of 20 ms, and then a background noise packet including background noise data (indicated as N in the figure). (Notation) is transmitted at intervals of 160 ms. Here, it is assumed that AMR (Adaptive Multi-Rate) is used as the speech encoding method and the encoding rate is 12.2 kbps.

Voice packets (voice packets # 1 to # 4) transmitted by the mobile station 200a are transferred to the radio base station 100. Here, since the transmission time is not constant due to the influence of congestion or the like, the arrival interval of voice packets to the radio base station 100 is not strictly 20 ms. The radio base station 100 waits for three voice packets (voice packets # 1 to # 3) to be buffered, and then wirelessly transmits the voice packets to the mobile station 200 at intervals of 20 ms. The arrival interval of voice packets to the mobile station 200 is not exactly 20 ms. The mobile station 200 absorbs fluctuations in the reception interval using the buffer memory, and sequentially decodes and reproduces the data included in the received voice packet at intervals of 20 ms.

Here, it is assumed that handover from the radio base station 100 to the radio base station 100a is determined in a state where the voice packets # 3 and # 4 are buffered in the radio base station 100. Then, the radio base station 100 wirelessly transmits the voice packets # 3 and # 4 to the mobile station 200 at the timing that comes first after the handover is determined among the transmission timings of the 20 ms period specified in the schedule before the handover. The mobile station 200 buffers the received voice packet.

Thereafter, voice packets (voice packets # 5 to # 7) transmitted from the mobile station 200a are transferred to the radio base station 100a. The radio base station 100a determines that the buffering amount is 3 packets based on the schedule information received from the radio base station 100, and waits for three voice packets (voice packets # 5 to # 7) to be buffered. Thereafter, voice packets are wirelessly transmitted to the mobile station 200 at intervals of 20 ms. The mobile station 200 can continue the audio reproduction based on the audio packets collectively received from the radio base station 100 until the radio base station 100a starts transmitting the audio packet.

Further, the background noise packet transmitted after the voice packet # 7 by the mobile station 200a is transferred to the radio base station 100a. The radio base station 100a wirelessly transmits a background noise packet to the mobile station 200 160 ms after transmitting the voice packet # 7. The mobile station 200 reproduces the background noise by decoding the data included in the background noise packet 160 ms after reproducing the data of the voice packet # 7.

As described above, it is easy to secure radio resources for transmission by wirelessly transmitting the voice packets buffered in the radio base station 100 at the originally scheduled timing.

FIG. 13 is a diagram showing a second example of packet flow. The overall flow of transmission of voice packets and background noise packets is the same as that shown in FIG. However, the radio base station 100 wirelessly transmits the buffered voice packet data to the mobile station 200 at the earliest possible timing after the handover decision regardless of the original schedule. Here, the earliest possible timing is, for example, the earliest timing among timings at which radio resources for transmission can be secured.

As described above, the voice packet buffered in the radio base station 100 is wirelessly transmitted at the earliest possible timing regardless of the originally scheduled timing, thereby reproducing the arrival of the voice packet at the mobile station 200. It is possible to further reduce the risk of not meeting the timing.

FIG. 14 is a diagram showing a third example of the packet flow. The overall flow of transmission of voice packets and background noise packets is the same as that shown in FIG. However, the radio base station 100 transmits the buffered voice packet data in a plurality of times without transmitting the buffered voice packet data at a time.

As described above, it is easier to secure radio resources for transmission by performing transmission in multiple times. Note that the transmission timing of each time may be a timing that is originally scheduled as in the example shown in FIG. 12, or an arbitrary timing that does not depend on the timing that is originally scheduled as in the example shown in FIG. Also good.

By using such a mobile communication system, it is possible to reduce the risk that the arrival of the voice packet data is not in time for the playback timing even when a handover occurs while the mobile station is playing back the voice packet data in a predetermined cycle. In addition, since schedule information is transmitted from the source radio base station to the destination radio base station, transmission of voice packet data is smoothly performed. Therefore, a decrease in voice reproduction quality at the time of handover is suppressed.

[Second Embodiment]
Next, a second embodiment will be described in detail with reference to the drawings. Differences from the first embodiment will be mainly described, and description of similar matters will be omitted.

The mobile communication system according to the second embodiment can be realized by the same system configuration as the mobile communication system according to the first embodiment shown in FIG. The radio base station and mobile station according to the second embodiment can be realized by the same module configuration as the radio base station 100 shown in FIG. 3 and the mobile station 200 shown in FIG. However, the control at the time of switching from a voiced section to a silent section is different from that in the first embodiment. Hereinafter, the second embodiment will be described using the same reference numerals as those used in the first embodiment.

FIG. 15 is a flowchart showing another procedure of packet transmission control. In the following, the process illustrated in FIG. 15 will be described in order of step number.
[Step S <b> 61] The control unit 160 performs signaling (transmission of control signals) related to persistent scheduling with the mobile station 200. Then, the control unit 160 makes it possible to transmit VoIP packet data.

[Step S62] The control unit 160 determines whether or not it is the start of a sound section. If it is the start of a sound section, the process proceeds to step S63. If it is not the start of the sound section, the process proceeds to step S65.

[Step S63] The control unit 160 waits for buffering of voice packet data addressed to the mobile station 200 in an amount (for example, 2 to 3 packets) specified in the buffering message in the buffer memory 110.

[Step S64] When the buffering in Step S63 is completed, the control unit 160 performs control so that the buffered voice packet data is sequentially transmitted in a cycle (for example, a cycle of 20 ms) corresponding to the voiced section. Thereafter, the process proceeds to step S62.

[Step S65] The control unit 160 determines whether or not it is the start of a silent section. If it is the start of a silent section, the process proceeds to step S66. If it is not the start of the silent section, the process proceeds to step S68.

[Step S <b> 66] The transmission / reception unit 140 transmits, to the mobile station 200, a control signal indicating a transition from a voiced section to a silent section based on an instruction from the control section 160.
[Step S67] The control unit 160 performs control so that the buffered background noise packet data is sequentially transmitted in a cycle (for example, 160 ms cycle) corresponding to the silent period. Thereafter, the process proceeds to step S62.

[Step S68] The control unit 160 determines whether or not the VoIP packet communication between the mobile station 200 and the mobile station 200a is completed. When the communication is finished, the transmission control of the VoIP packet data addressed to the mobile station 200 is finished. If the communication has not ended, the process proceeds to step S62.

In this way, when the radio base station 100 acquires the background noise packet data after acquiring the voice packet data, the radio base station 100 transmits a control signal indicating the transition from the voiced section to the silent section to the mobile station 200. Thereby, the mobile station 200 can recognize the transition to the silent section earlier.

Then, the mobile station 200 can turn off the power of the receiving circuit in a time zone other than the timing specified by Persistent Scheduling. At this time, if the transition to the silent period with a long transmission / reception cycle can be recognized quickly, the number of times the receiving circuit is turned on immediately after the end of the voiced period can be reduced, and the power consumption of the mobile station 200 is further suppressed. can do.

FIG. 16 is a diagram showing a fourth example of packet flow. The overall flow of transmission of voice packets and background noise packets is the same as that shown in FIG. However, the radio base station 100a transmits a control signal to the mobile station 200 before transmitting the first background noise packet. For example, it is conceivable that the radio base station 100a notifies the control signal of when the transmission order of the background noise packets arrives immediately after the arrival of the first background noise packet. It is also conceivable to notify the control signal that the background noise packet will be transmitted next, at the same time as or immediately after the transmission of the last voice packet (voice packet # 7).

In this way, by transmitting the control signal before the originally scheduled transmission timing of the background noise packet (160 ms after the transmission of the last voice packet), the mobile station 200 shifts to the silent period earlier. Can know. Thereby, the mobile station 200 can shift to the intermittent reception mode of 160 ms cycle even if 160 ms has not elapsed since the last voice packet reception.

Note that whether the arrived VoIP packet is a voice packet or a background noise packet can be determined based on the packet size, for example. This is because the background noise packet is often shorter in packet length than the voice packet.

FIG. 17 is a diagram showing a fifth example of packet flow. The overall flow of transmission of voice packets and background noise packets is the same as that shown in FIG. In FIG. 17, after transmitting the last voice packet, the radio base station 100a transmits a background noise packet to the mobile station 200 instead of the control signal or together with the control signal. That is, the radio base station 100a transmits the first background noise packet regardless of the originally scheduled background noise packet transmission timing. The mobile station 200 buffers the received background noise packet, decodes it at the originally scheduled timing, and reproduces the background noise.

As described above, even if the background noise packet is transmitted instead of the control signal or together with the control signal, the mobile station 200 can know the transition to the silent period earlier and shift to the intermittent reception mode with a period of 160 ms earlier. be able to.

By using such a mobile communication system, the same effect as that of the first embodiment can be obtained. Furthermore, the power consumption of the mobile station 200 is reduced by using the mobile communication system according to the second embodiment.

It should be noted that the specific device configurations shown in the first embodiment and the second embodiment can be changed to other device configurations. For example, a radio base station and a mobile station may be provided with a plurality of antennas to perform MIMO (Multiple-Input-Multiple-Output) communication. Further, instead of the radio base station making the handover decision, the mobile station or a server device in the core network may make the handover decision.

For the wireless part, various multiplexing schemes such as CDMA and OFDMA (Orthogonal Frequency Division Multiple Access) can be adopted, and various modulation schemes such as QAM (Quadrature Amplitude Modulation) and QPSK (Quadrature Phase Shift Shift Keying) are adopted. In addition, various encoding methods such as a convolutional code and a turbo code can be employed.

Expressing the above-described embodiment from another aspect, in a mobile communication system that wirelessly transmits a data block (voice packet data used for reproduction) used in a predetermined cycle in a mobile station from a radio base station to the mobile station. In the control method, the data addressed to the mobile station is stored in a storage unit (base station buffer memory), and the data addressed to the mobile station in the storage unit (buffer memory) contains a predetermined amount (for example, a plurality of N voices). Packet data) is started, and then a process of sequentially transmitting data in the storage unit to the mobile station in a predetermined cycle (for example, 20 ms) is started, and when handover for the mobile station is determined, Before switching the connection to the radio base station, at least N (two or more own data blocks) of the data block among the data stored in the storage unit (buffer memory). Number) the number fraction more data to the mobile station at a time can be said to be wirelessly transmitted. Here, it is assumed that the predetermined amount is equal to or greater than N (natural number of 2 or more) of data blocks (see FIG. 12). Alternatively, the amount of data is greater than or equal to the amount of data corresponding to two data blocks depending on the radio propagation status.

According to this, since transmission of voice packet data is started from the radio base station after waiting for the data addressed to the mobile station to reach a predetermined amount (for example, a plurality of N voice packet data), the radio base station When there is a need for switching, there is a high possibility that data for a plurality of data blocks is stored in the storage unit, and the plurality of data blocks are wirelessly transmitted to the mobile station at one time. A plurality of data blocks can be used for a data block to be used in a predetermined period without receiving a data block from the radio base station for a certain period of time after the reception.

In addition, when the above-described embodiment is expressed from another aspect, a wireless device (for example, a base station) that wirelessly transmits voice packet data at a predetermined period to a partner device (for example, a mobile station) and a partner device are provided. In a control method in a mobile communication system, when a connection destination of a counterpart device (for example, a mobile station) is switched from the wireless device to another wireless device, a predetermined cycle (for example, Persistent Scheduling in a voice section) before switching is performed. Voice packet data is transmitted from a wireless device (for example, a base station) at a timing that does not comply, and the counterpart device (for example, a mobile station) receives voice packet data that is transmitted at a timing that does not conform to a predetermined cycle (see FIG. 13). ).

According to this, since the voice packet data is transmitted from the wireless device at a timing that does not follow the predetermined cycle, the voice packet data is transmitted before the predetermined cycle arrives, and the switching operation is started early and completed. It is also possible.

In addition, when the above-described embodiment is expressed from another aspect, in a control method in a mobile communication system that transmits voice packet data from a radio base station to a mobile station, at least one of the radio base station and the mobile station is: On the other hand, predetermined buffering in which the radio base station starts transmitting the voice packet data stored in the buffer memory of the radio base station after a predetermined amount of voice packet data is stored in the buffer memory of the radio base station. The mobile station reproduces the voice packet data stored in the buffer memory of the mobile station after a predetermined amount of voice packet data is stored in the buffer signal of the mobile station or a control signal indicating whether to execute the process The radio base station or mobile station that has transmitted the control signal indicating whether or not to start buffering processing and received the control signal, It can be said to perform the transmission control or playback control based on the signal.

The above-described buffering message is an example of this control signal. By transmitting such a control signal and the receiving side following it, it is possible to smoothly control which device performs the buffering process. be able to.

In addition, when the above-described embodiment is expressed from another aspect, a mode longer than the first cycle is longer than the mode in which voice packet data is wirelessly transmitted to the partner device in the first cycle (for example, the mode in a voiced section). In a control method in a mobile communication system including a radio apparatus and a counterpart apparatus that perform transmission by switching to a mode in which background noise packet data is wirelessly transmitted with a period of 2 (for example, a mode in a silent period), It can be said that the signal for switching the mode is transmitted from the wireless communication apparatus to the partner apparatus at a timing earlier than the transmission timing of the transmitted background noise packet data, and the partner apparatus receives the signal and uses it for reception control. .

According to this, the counterpart device can detect the mode change at an early stage and can use it for reception control. For example, the partner apparatus can recognize the switching of the wireless transmission mode due to the second period longer than the first period at an early stage, and can perform switching so as to perform an operation that does not perform the reception process according to the first period. . For example, it is possible to turn off the power of the reception unit or receive other signals until the first transmission in the second period. In the example of FIG. 17, the power of the receiving unit can be turned off during the period from the reception of the control signal to the first reception of N.

The above merely shows the principle of the present invention. In addition, many modifications and changes can be made by those skilled in the art, and the present invention is not limited to the precise configuration and application shown and described above, and all corresponding modifications and equivalents may be And the equivalents thereof are considered to be within the scope of the invention.

Explanation of symbols

10, 10a Radio base station 11 Buffer memory 12 Transmitter 20 Mobile station 21 Receiver 22 Regenerator

Claims

In a transmission control method of a wireless base station that wirelessly transmits voice packet data to a mobile station,
The acquired voice packet data addressed to the mobile station is stored in a buffer memory, and the voice packet data in the buffer memory is moved at a predetermined cycle after the voice packet data in the buffer memory reaches a predetermined amount. Start the process of wireless transmission sequentially to the station,
When it is determined that the mobile station performs handover to another radio base station, all or a plurality of voice packet data in the buffer memory are transmitted to the mobile station by radio.
The transmission control method characterized by the above-mentioned.
The transmission control method according to claim 1, wherein after the handover is determined, the transmission schedule of voice packet data to the mobile station is notified to the other radio base station.
The transmission control according to claim 1, wherein the wireless transmission of all the voice packet data in the buffer memory is performed at the earliest timing after the handover determination among the timings specified in the predetermined cycle. Method.
2. The transmission control method according to claim 1, wherein the wireless transmission of all voice packet data in the buffer memory is performed at the earliest timing after the handover determination that can secure the wireless resources for transmission. .
The transmission control method according to claim 1, wherein the wireless transmission of all voice packet data in the buffer memory is performed at a plurality of timings after the handover decision.
The acquisition of background noise packet data addressed to the mobile station after starting transmission of voice packet data, a signal indicating a change in transmission cycle is transmitted to the mobile station before transmission of the background noise packet data. The transmission control method according to claim 1 in the range.
2. The transmission control method according to claim 1, wherein a signal indicating that buffering is performed in the radio base station is transmitted to the mobile station before transmission of voice packet data is started.
Only when a signal indicating that buffering is to be performed at the radio base station is received from the mobile station before starting transmission of voice packet data, it waits for the voice packet data in the buffer memory to reach the predetermined amount. The transmission control method according to claim 1, wherein:
In a wireless base station that wirelessly transmits voice packet data to a mobile station,
A buffer memory for storing the acquired voice packet data addressed to the mobile station;
Waiting for the voice packet data in the buffer memory to reach a predetermined amount, a process of sequentially wirelessly transmitting the voice packet data in the buffer memory to the mobile station at a predetermined cycle is started. A transmitter that wirelessly transmits all or a plurality of voice packet data in the buffer memory to the mobile station,
A radio base station characterized by comprising:
In a mobile station that receives voice packet data from a radio base station and plays back voice,
When it is decided to perform handover to another radio base station while receiving voice packet data from the radio base station at a predetermined cycle, all or a plurality of voices held in the buffer memory by the radio base station A receiver for receiving packet data from the radio base station;
Based on the voice packet data held in the buffer memory by the radio base station received by the receiving unit until the reception of voice packet data from the other radio base station is started after the handover is determined. A playback unit for playing back audio at a predetermined audio playback timing;
A mobile station characterized by comprising:
In a control method in a mobile communication system for wirelessly transmitting a data block used at a predetermined cycle in a mobile station from a radio base station to the mobile station,
Store the acquired data addressed to the mobile station in a storage unit, wait for the data addressed to the mobile station in the storage unit to reach a predetermined amount, and then move the data in the storage unit in a predetermined cycle Start the process of wireless transmission sequentially to the station,
When handover for the mobile station is determined, before the connection to another radio base station is switched, at least the data amount corresponding to the data block 2 block among the data stored in the storage unit Wirelessly transmit a quantity of data to the mobile station at once,
The predetermined amount is data of an amount equal to or greater than the data amount corresponding to two blocks of the data block.
A control method in a mobile communication system.
In a control method in a mobile communication system comprising a wireless device for wirelessly transmitting voice packet data to a counterpart device at a predetermined cycle and the counterpart device,
When the connection destination of the counterpart device is switched from the wireless device to another wireless device, before the switching, the voice packet data is transmitted from the wireless device at a timing not following the predetermined period,
The counterpart device receives voice packet data transmitted at a timing not following the predetermined period;
A control method in a mobile communication system.
In a control method in a mobile communication system for transmitting voice packet data from a radio base station to a mobile station,
At least one of the radio base station and the mobile station is stored in the buffer memory of the radio base station after a predetermined amount of voice packet data is stored in the buffer memory of the radio base station. A control signal indicating whether or not to execute a predetermined buffering process in which the radio base station starts transmitting the voice packet data, or after a predetermined amount of voice packet data is stored in the buffer memory of the mobile station Transmitting a control signal indicating whether or not to perform buffering processing in which the mobile station starts reproduction of voice packet data stored in the buffer memory of the mobile station;
The radio base station or the mobile station that has received the control signal performs transmission control or reproduction control based on the control signal.
A control method in a mobile communication system.
A radio apparatus that performs transmission by switching from a mode in which voice packet data is wirelessly transmitted in a first cycle to a counterpart apparatus to a mode in which background noise packet data is wirelessly transmitted in a second period longer than the first period. And in a control method in a mobile communication system comprising the counterpart device,
At a timing earlier than the transmission timing of the background noise packet data transmitted first by the mode switching, a signal for notifying the mode switching is transmitted from the wireless communication device to the counterpart device,
The counterpart device receives the signal and uses it for reception control.
A control method in a mobile communication system.
In a mobile communication system that transmits all or a plurality of voice packet data from a base station to a mobile station at the time of handover, and performs voice reproduction at a predetermined voice reproduction timing in the mobile station,
The mobile communication system includes a base station that communicates before handover, and a mobile station,
The base station waits for a predetermined amount of voice packet data in the buffer memory to store the acquired voice packet data addressed to the mobile station and the voice packet data in the buffer memory at a predetermined cycle. When a process of sequentially transmitting packet data to the mobile station is started, and then it is determined that the mobile station performs handover to another radio base station, all or a plurality of voice packet data in the buffer memory A transmitter for wirelessly transmitting to the mobile station,
The mobile station includes: a receiving unit that receives all or a plurality of voice packet data held in the buffer memory of the radio base station from the radio base station; and a voice packet from the other radio base station after determining the handover. A reproduction unit that performs audio reproduction at a predetermined audio reproduction timing based on audio packet data held in the buffer memory by the radio base station received by the reception unit until data reception is started ,
A mobile communication system.