WO2009084687A1 - 無線通信装置 - Google Patents
無線通信装置 Download PDFInfo
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- WO2009084687A1 WO2009084687A1 PCT/JP2008/073857 JP2008073857W WO2009084687A1 WO 2009084687 A1 WO2009084687 A1 WO 2009084687A1 JP 2008073857 W JP2008073857 W JP 2008073857W WO 2009084687 A1 WO2009084687 A1 WO 2009084687A1
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- wireless communication
- handover
- communication network
- packet
- jitter buffer
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- 238000004891 communication Methods 0.000 title claims abstract description 255
- 238000009825 accumulation Methods 0.000 claims abstract description 19
- 230000003044 adaptive effect Effects 0.000 claims description 12
- 230000000593 degrading effect Effects 0.000 abstract 1
- 238000000034 method Methods 0.000 description 21
- 238000010586 diagram Methods 0.000 description 12
- 238000012544 monitoring process Methods 0.000 description 11
- 238000012545 processing Methods 0.000 description 11
- 238000005259 measurement Methods 0.000 description 10
- 230000005540 biological transmission Effects 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 6
- 239000003795 chemical substances by application Substances 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/14—Reselecting a network or an air interface
- H04W36/144—Reselecting a network or an air interface over a different radio air interface technology
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/24—Reselection being triggered by specific parameters
- H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/24—Reselection being triggered by specific parameters
- H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
- H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/14—Reselecting a network or an air interface
Definitions
- the present invention relates to a wireless communication apparatus capable of performing handover between different wireless communication networks.
- IP mobility technology that enables seamless movement by enabling handover between different wireless communication networks, such as mobile phone networks and wireless LANs, in order to realize a ubiquitous environment. Is being considered. Specific protocols in this IP mobility technology include Mobile IPv4 and Mobile IPv6 (hereinafter collectively referred to as Mobile IP) that support movement of individual communication terminals, and support movement in units of networks. There is NEMO (Network Mobility).
- the allowable bandwidth of the wireless communication path changes depending on a propagation environment such as fading. Then, the arrival interval of packets received by the communication terminal also changes according to the change in the allowable bandwidth.
- a jitter buffer is provided in the communication terminal, and received packets are temporarily stored in the jitter buffer, and then the packets are read from the jitter buffer and reproduced at intervals according to the application.
- the fluctuation of the packet that is, the deviation of the reproduction interval of the packet due to the deviation (jitter) of the arrival interval is absorbed, and the reproduction quality such as the reproduction sound quality is prevented from deteriorating.
- the playback speed is increased. Change, discard the received packet, or change the buffer size (delay time) of the jitter buffer.
- the absolute downlink delay time of the packet received by the communication terminal that is, the time required for the packet transmitted from the partner communication terminal to be received via the wireless communication network differs depending on the wireless communication network. For this reason, in the case of a wireless communication device in which a communication terminal moves, when a handover is performed to a different wireless communication network, for example, if the downlink absolute delay time of the handover destination is shorter than the downlink absolute delay time of the handover source, Overtaking will occur in the packet.
- FIG. 8 is a diagram showing the flow of packets in this case.
- the packet transfer timing by the agent (HA: Home Agent) and the reception timing of the packet received by the jitter buffer of the MN are shown.
- the agent HA: Home Agent
- the reception timing of the packet received by the jitter buffer of the MN are shown.
- there is no fluctuation (shift in arrival interval) in the received packet in each of the handover source wireless communication network A and the handover destination wireless communication network B, it is shown that there is no fluctuation (shift in arrival interval) in the received packet.
- the MN transmits a Registration Request (HA Binding in Update in NEMO) to the HA via the handover target wireless communication network B, and the handover destination to the HA. Register the care-of address of. Thereafter, the MN receives RegistrationRegReply (Binding Acknowledge in NEMO), which is handover completion information returned from the HA, disconnects from the handover source wireless communication network A, and thereafter receives the handover destination information. Packets are transmitted and received via the wireless communication network B.
- Registration Request HA Binding in Update in NEMO
- the handover completion information is displayed.
- TAB from (TddnA-TddnB) from the time of reception, overtaking occurs in the received packet. Therefore, during this period TAB, as shown in FIG. 9A, the number of packets received by the jitter buffer per unit time is very large.
- the number of packets in the jitter buffer is as shown in FIG. 9 (c), it rises sharply from the time of handover to the radio communication network B. For this reason, packets that exceed the buffer size due to overtaking are discarded without being reproduced, and the number of packets in the jitter buffer settles to a certain number of packets corresponding to the buffer size.
- the packet when the packet is discarded, the sound quality of the reproduced sound is deteriorated.
- the buffer size of the jitter buffer is sufficiently large, the packet is not discarded, and the packets from the handover source and the handover destination can be reproduced at a scheduled timing.
- the packet from the handover destination received overtaking the packet from the handover source has a longer residence time in the jitter buffer than the packet from the handover source.
- the delay time becomes longer than necessary, and real-time performance matching the delay time of each wireless communication network cannot be realized.
- a jitter buffer control method that monitors the reception status of packets and controls the reading speed of packets from the jitter buffer based on the monitoring results is provided as a means for improving such a trouble at the time of handover. It has been proposed (see, for example, Patent Document 1).
- FIG. 10 is a diagram illustrating an operation state of the jitter buffer according to the jitter buffer control method disclosed in Patent Document 1.
- FIGS. 10A to 10C show the number of received packets per unit time of the jitter buffer, the playback speed, and the number of packets in the jitter buffer, as in FIGS. 9A to 9C.
- the packet reproduction speed is increased during the overtaking period of the packet, and in particular, at the initial stage of overtaking, the reproduction speed is changed rapidly. .
- the handover destination packet is received and played back before the next handover source packet can be received, and arrives after that.
- the handover source packet is discarded. Thereby, there is a concern that the sound quality of the reproduced sound is deteriorated.
- an object of the present invention made in view of the above points is to achieve a different wireless communication network while realizing a real-time property suitable for each wireless communication network without causing deterioration in sound quality of reproduced sound due to packet loss. It is an object of the present invention to provide a wireless communication apparatus capable of performing handover.
- the invention of the wireless communication device is as follows: A wireless communication unit that performs wireless communication by connecting to a first wireless communication network and a second wireless communication network different from the first wireless communication network; An execution unit that executes an application of a real-time communication system via the wireless communication unit; A jitter buffer for temporarily accumulating packets of the application being executed by the execution unit and absorbing jitter received via the wireless communication unit; A communication quality acquisition unit for acquiring communication quality of a wireless link in the first wireless communication network; A handover control unit that starts a handover from the first wireless communication network to the second wireless communication network based on the communication quality acquired by the communication quality acquisition unit; After the handover by the handover control unit is completed, when the reception interval of the packet of the application received via the wireless communication unit becomes equal to or greater than a predetermined value, based on the packet accumulation amount of the jitter buffer, A control unit for controlling the playback speed; It is characterized by providing.
- the invention according to a second aspect is the wireless communication device according to the first aspect,
- the control unit increases the playback speed of the application when the amount of accumulated packets in the jitter buffer is greater than or equal to a threshold value.
- the invention according to a third aspect is the wireless communication device according to the second aspect,
- the control unit is configured to return the reproduction speed of the application to a normal speed when the amount of accumulated packets in the jitter buffer falls below the threshold while the application is being reproduced quickly.
- the invention according to a fourth aspect is the wireless communication apparatus according to the first aspect, An adaptive jitter controller that controls the buffer size of the jitter buffer according to the reception status of the packet of the application, The adaptive jitter control unit stops the control of the buffer size of the jitter buffer when the completion of the handover by the handover control unit is detected.
- the playback speed of the application is controlled based on the packet accumulation amount of the jitter buffer after the packet reception interval becomes a predetermined value or more.
- the delay time of the second radio communication network of the handover destination is shorter than the delay time of the first radio communication network of the handover source, the overtaking of the packet by the handover is finished, and the After only packets from the two wireless communication networks arrive, it is possible to read out the packets accumulated more than usual in the jitter buffer by setting the reproduction speed to be higher than the normal speed. Therefore, handover from the first wireless communication network to the second wireless communication network can be performed without causing deterioration in sound quality of reproduced sound due to packet loss, deterioration in call quality due to deterioration in real-time characteristics, or the like.
- FIG. 6 is an explanatory diagram showing a packet flow at the time of handover by the radio communication apparatus according to the present embodiment and an operation of a jitter buffer correspondingly.
- Wireless communication apparatus 12 Partner communication terminal 12a Handset 15 1st wireless communication network 15a Base station 16 2nd wireless communication network 16a Access point 17 Packet network 18 Internet 21,22 SIP server 23 Home agent (HA) 31 First wireless I / F 32 Second wireless I / F 33 Telephone Function Unit 34 Communication Processing Unit 35 Radio Information Acquisition Unit 36 Handover Control Unit 47 Jitter Buffer 50 Jitter Buffer Monitoring Unit 51 Jitter Buffer Control Unit 55 Handover Information Acquisition Unit 56 Playback Speed Calculation Unit
- FIG. 1 is a diagram showing a schematic configuration of a communication network that can be used by a wireless communication apparatus according to an embodiment of the present invention.
- a wireless communication device 11 that is a mobile node performs a call using VoIP that is a real-time communication application with a counterpart communication terminal 12 that is a counter node.
- the wireless communication device 11 can be handed over between the first wireless communication network 15 and the second wireless communication network 16.
- the first wireless communication network 15 and the second wireless communication network 16 are coupled to the Internet 18 via a packet network 17.
- the first wireless communication network 15 is, for example, a cdma2000 EV-DO mobile phone network
- the second wireless communication network 16 is, for example, a wireless LAN
- the second wireless communication network 16 is the first wireless communication network.
- the downlink absolute delay time is shorter than that of the communication network 15.
- reference numeral 15 a indicates a base station of the first wireless communication network
- reference numeral 16 a indicates an access point of the second wireless communication network 16.
- the partner communication terminal 12 is composed of, for example, a personal computer to which the handset 12a is connected and a softphone is installed, and is connected to the Internet 18 via an Internet service provider (not shown).
- SIP Session Initiation Protocol
- HA home agent
- the home address used in the wireless communication network to which the wireless communication apparatus 11 originally belongs is registered in the HA 23, and the care-of address of the handover destination wireless communication network 16 is set at the time of handover. sign up. Thereby, the wireless communication device 11 can be handed over between different wireless communication networks.
- IP mobility technology is well known in the above-described mobile IP and NEMO, and thus detailed description thereof is omitted here.
- the wireless communication network to which the wireless communication device 11 originally belongs is the first wireless communication network 15, and the handover from the first wireless communication network 15 to the second wireless communication network 16 is performed.
- FIG. 2 is a functional block diagram showing a schematic configuration of the wireless communication apparatus 11 according to the present embodiment shown in FIG.
- the wireless communication device 11 executes a first wireless I / F (interface) 31 corresponding to the first wireless communication network 15, a second wireless I / F 32 corresponding to the second wireless communication network 16, and a VoIP application.
- the wireless information of the telephone function unit 33, the communication processing unit 34 that controls connection to the first wireless communication network 15 and the second wireless communication network 16, and the wireless information of the first wireless communication network 15 and the second wireless communication network 16 is acquired.
- a wireless information acquisition unit 35; and a handover control unit 36 that controls a handover between the first wireless communication network 15 and the second wireless communication network 16.
- the communication processing unit 34 configures a wireless communication unit that performs wireless communication together with the first wireless I / F 31 and the second wireless I / F 32.
- the communication processing unit 34 performs a call between the telephone function unit 33 and the counterpart communication terminal 12 via the first wireless communication network 15 or the second wireless communication network 16 and controls the handover control unit 36.
- the connection of the first wireless I / F 31 or the second wireless I / F 32 is controlled so as to communicate with the HA 23.
- the wireless information acquisition unit 35 acquires the communication quality of the corresponding first wireless communication network 15 and second wireless communication network 16 from the first wireless I / F 31 and the second wireless I / F 32 as wireless information,
- the acquired communication quality is supplied to the handover control unit 36.
- the communication quality for example, RSSI (Received Signal Signal Strength Indicator) indicating a wireless state is acquired. Therefore, the radio information acquisition unit 35 constitutes a communication quality acquisition unit that acquires the communication quality of the radio link.
- the handover control unit 36 Based on the communication quality from the radio information acquisition unit 35, the handover control unit 36 generates handover information including a decision as to whether or not to schedule a handover, and from the first radio communication network 15 based on the handover information. 2 Controls handover to the radio communication network 16.
- FIG. 3 is a functional block diagram showing a schematic configuration of the telephone function unit 33 of the wireless communication apparatus 11 shown in FIG.
- the telephone function unit 33 is composed of, for example, a soft phone, and has a button input unit 41, a screen display unit 42, a microphone 43, an encoder 44, a packet transmission unit 45, a packet reception unit 46, a jitter buffer, as in the configuration of a known soft phone. 47, a decoder 48, a speaker 49, a jitter buffer monitoring unit 50, a jitter buffer control unit 51, a SIP control unit 52, and an overall control unit 53 for controlling the overall operation.
- the overall control unit 53 acquires user operation information via the button input unit 41 and the screen display unit 42, and controls the overall operation based on the acquired information.
- the SIP control unit 52 controls SIP procedures for starting and ending a call.
- the audio data acquired from the microphone 43 is encoded by the encoder 44, and the encoded data is put into a packet from the packet transmission unit 45 and transmitted to the partner communication terminal 12 via the communication processing unit 34.
- the packet from the partner communication terminal 12 received by the packet receiving unit 46 via the communication processing unit 34 is once fetched into the jitter buffer 47 and then read out.
- the read packet is loaded into the payload by the decoder 48.
- the portion is decoded and output as reproduced sound from the speaker 49.
- the reception status of packets in the jitter buffer 47 and the status of the number of packets in the jitter buffer 47 are monitored by the jitter buffer monitoring unit 50, and the jitter buffer control unit 51 determines the state of the jitter buffer 47 based on the monitoring result. Operation is controlled.
- the wireless communication apparatus 11 further includes a handover information acquisition unit 55 and a playback speed calculation unit 56 in the telephone function unit 33.
- the handover information acquisition unit 55 monitors the handover information from the handover control unit 36 at regular intervals, and acquires information on whether or not there is a handover schedule. When there is a handover schedule, the handover information acquisition unit 55 further acquires the required handover information from the handover control unit 36 and supplies the acquired required handover information to the playback speed calculation unit 56.
- the difference from the absolute downlink delay time is calculated.
- the jitter buffer control is performed based on the monitoring result of the jitter buffer 47 by the jitter buffer monitoring unit 50.
- the unit 51 controls the buffer size of the jitter buffer 47 and the playback speed of the received packet from the jitter buffer 47. Therefore, the telephone function unit 33 constitutes an execution unit that executes a real-time communication system application and a control unit that controls the playback speed of the application.
- the handover control unit 36 determines a handover schedule based on the communication qualities acquired from the first wireless I / F 31 and the second wireless I / F 32, respectively. For example, when a call is made by forming a wireless link with the first wireless communication network 15, the communication quality acquired from the first wireless I / F 31 becomes worse than the handover schedule determination threshold, and the second wireless I / F When the communication quality of F32 is equal to or higher than the handover schedule determination threshold, the handover control unit 36 determines the handover schedule to the second wireless communication network 16, that is, determines the start of handover preparation.
- the communication quality of the second wireless communication network 16 that is not used for a call is acquired (measured) by receiving broadcast information transmitted from the access point 16a, for example.
- the handover control unit 36 determines the handover schedule
- the handover source downlink absolute delay time Tddn1 in the currently used wireless communication network here, the first wireless communication network 15
- the handover destination wireless communication network here, The handover destination downlink absolute delay time Tddn2 in the second wireless communication network 16
- These pieces of information are supplied to the telephone function unit 33 as required handover information together with information indicating that there is a handover schedule.
- the handover source downlink absolute delay time Tddn1 and the handover destination downlink absolute delay time Tddn2 are acquired by any one of the first to fourth absolute delay time acquisition methods described below, for example.
- the handover control unit 36 determines a handover schedule
- the handover control unit 36 controls the telephone function unit 33 and / or the communication processing unit 34 to synchronize with the radio communication apparatus 11 in time.
- the HA 23 is requested to transmit a measurement packet having a transmission time stamp.
- the measurement packet is transmitted from the HA 23 to both the first wireless communication network 15 and the second wireless communication network 16.
- the wireless communication device 11 receives the measurement packet transmitted from the HA 23 via the corresponding first wireless I / F 31 and second wireless I / F 32, respectively, and based on the reception time and the time stamp of the measurement packet.
- the downstream absolute delay times Tddn1 and Tddn2 of the corresponding network are measured.
- the absolute downlink delay time of the handover source wireless communication network can be measured from the received packet during a call
- transmission of the measurement packet to the wireless communication network can be omitted.
- the handover control unit 36 determines a handover schedule
- the handover control unit 36 controls the telephone function unit 33 and / or the communication processing unit 34 to synchronize with the wireless communication apparatus 11 in time. This is notified to the HA 23.
- the HA 23 causes the measurement packet to be transmitted to both the first wireless communication network 15 and the second wireless communication network 16, and the downlink absolute delay of the corresponding network. Times Tddn1 and Tddn2 are measured.
- the handover control unit 36 controls the telephone function unit 33 and / or the communication processing unit 34 from the wireless communication device 11 to the wireless communication device 11.
- the HA 23 that is time-synchronized with each other transmits measurement packets such as PING and RTCP from both the first wireless communication network 15 and the second wireless communication network 16, receives the reply, and receives the corresponding network. Measure the downstream absolute delay times Tddn1 and Tddn2.
- the handover control unit 36 acquires the absolute delay time of each wireless communication network by using the handover technique studied in IEEE 802.21. .
- the acquisition method is illustrated below.
- the wireless communication device 11 acquires the next value stored in the first information server of the first wireless communication network 15. From the measurement server that operates to measure the delay time (for example, connected to the backbone network of the Internet 18) to the current base station 15a connected through the first wireless communication network 15 Standard value of one-way delay time (Tn3) Standard value of the upper and lower delay times between the base station 15a and the terminal connected to the base station 15a (downward: Trdn3, upstream: Trup3) Further, the wireless communication device 11 transmits a measurement packet such as PING to the HA 23, receives the reply, and measures the round-trip delay time Trt1 between the wireless communication device 11 and the HA 23.
- Tn3 one-way delay time
- Tddn1 of the first wireless communication network 15 is calculated from these values according to the following equation (1).
- this one-way delay time is approximated by adding Tn3 and ⁇ Trt1- (Tn3 + Trdn3 + Tn3 + Trup3) ⁇ / 2.
- Tddn1 Tn3 + Trdn3 + ⁇ Trt1- (Tn3 + Trdn3 + Tn3 + Trup3) ⁇ / 2 (1)
- the wireless communication device 11 obtains the next value stored in the second information server connected to the second wireless communication network 16 that is the handover destination via the first information server of the first wireless communication network 15. To do.
- the location information of the wireless communication device 11 acquired by the wireless communication device 11 or the base station 15a is transmitted to the second information server.
- Tn4 Standard value (Tn4) of one-way delay time between the access point 16a expected to be connected to the wireless communication device 11 and the measurement server Standard value of the upper and lower delay times between the access point 16a and the terminal connected to the access point 16a (downward: Trdn4, upstream: Trup4)
- Tddn2 the absolute delay time (Tddn2 of the second wireless communication network 16 is calculated from these values according to the following equation (2).
- the one-way delay time between the access point 16a and the HA 23 cannot be acquired, the one-way delay time is approximated by adding Tn4 and ⁇ Trt1- (Tn3 + Trdn3 + Tn3 + Trup3) ⁇ / 2.
- Tddn2 Tn4 + Trdn4 + ⁇ Trt1- (Tn3 + Trdn3 + Tn3 + Trup3) ⁇ / 2 (2)
- the handover control unit 36 acquires the handover source downlink absolute delay time Tddn1 and the handover destination downlink absolute delay time Tddn2, and supplies the acquired information to the telephone function unit 33.
- the handover control unit 36 determines a handover schedule
- the handover control unit 36 controls the radio processing unit 34 to connect the second radio I / F 32 to the second radio communication network 16.
- the handover control unit 36 sends a Registration Request (Binding Update in NEMO) to the HA 23 via the second wireless communication network 16 that is the handover destination, and registers the care-of address (care of address) of the handover destination in the HA 23. To do.
- 8 bits of RegistrationRegRequest Field of Registration Request message are set (in NEMO, MultipleMulticare of address is used), so that communication can be performed in both the first wireless communication network 15 and the second wireless communication network 16.
- the handover control unit 36 of the first wireless communication network 15 that is the handover source Unregister the care-of address and disconnect the connection. Thereafter, the handover control unit 36 controls the communication processing unit 34 to continue the VoIP application via the second wireless communication network 16 that is the handover destination, and supplies the received handover completion information to the telephone function unit 33. .
- FIG. 4 is a sequence diagram showing the operation of the main part of the telephone function unit 33.
- FIG. 5 is a flowchart showing the operation of the main part of the telephone function unit 33. Here, the operation will be described with reference to the flowchart of FIG.
- the handover information acquisition unit 55 monitors the handover information from the handover control unit 36 at regular intervals. As a result, when information indicating that there is a handover schedule is acquired, the handover information acquisition unit 55 further includes the handover source downlink absolute delay time Tddn1 and the handover destination downlink absolute delay, which are required handover information from the handover control unit 36. Time Tddn2 is acquired (step S11), and the acquired required handover information is supplied to the playback speed calculation unit 56.
- the reproduction speed calculation unit 56 obtains the difference T2 between the downlink absolute delay time (Tddn1) of the first radio communication network 15 and the downlink absolute delay time (Tddn2) of the second radio communication network 16 acquired from the handover information acquisition unit 55.
- T2 Tddn2- Tddn1) is calculated, and it is determined whether or not the difference T2 is less than a certain value (for example, ⁇ 0) (step S12).
- the playback speed calculation unit 56 transmits Registration Reply (binding binding in NEMO) which is handover completion information transmitted from the handover control unit 36 via the handover information acquisition unit 55. Wait for Acknowledge (step S13).
- the playback speed calculation unit 56 sets the buffer size of the jitter buffer 47 to an appropriate size. For this reason, first, when the jitter buffer 47 has an adaptive jitter buffer function in which the buffer size is controlled by the jitter buffer control unit 51 in accordance with the reception status of the packet by the jitter buffer monitoring unit 50, the jitter buffer control unit 51 Is instructed to turn off (disable) the adaptive jitter buffer function (step S14). This prevents the discard of the packet from the handover source due to the overtaking of the packet from the handover destination. Therefore, in this case, the jitter buffer control unit 51 functions as an adaptive jitter control unit. If the jitter buffer 47 does not have an adaptive jitter buffer function for dynamically controlling the buffer size, the process of step S14 is omitted.
- the playback speed calculation unit 56 acquires the current packet accumulation amount in the jitter buffer 47 from the jitter buffer monitoring unit 50 (step S15).
- the current packet accumulation amount is shown as the time required for reproducing all the packets currently accumulated in the jitter buffer 47 at the reproduction speed at the time of receiving the handover completion information.
- the reproduction speed calculation unit 56 acquires the current buffer size of the jitter buffer 47 from the jitter buffer control unit 51 (step S16).
- the playback speed calculation unit 56 calculates the sum of the delay time difference between the handover source and the handover destination (the absolute value of the difference T2 calculated in step S12) and the current packet accumulation amount acquired in step S15. It is determined whether or not the buffer size acquired in step S16 is exceeded (step S17).
- the buffer size of the jitter buffer 47 is set to (delay time difference + current packet accumulation amount) via the jitter buffer control unit 51. ) Control is performed so as to enlarge the above (step S18). This prevents occurrence of packet overrun due to handover, that is, prevents an incoming packet from being discarded without entering the jitter buffer 47.
- the playback speed calculation unit 56 periodically acquires the packet reception interval of the jitter buffer 47 by the jitter buffer monitoring unit 50 (step S19), and the average of the packet reception intervals is a predetermined value corresponding to the application being executed. It is determined whether or not the above (for VoIP, for example, 20 msec or more) (step S20). In step S17, if (delay time difference + current packet accumulation amount) ⁇ (buffer size), no overrun occurs, so the buffer size remains the buffer size at the time of handover, and the process proceeds to step S19. To do.
- step S20 If it is determined in step S20 that the packet reception interval is less than the predetermined value, there is a possibility that a packet is overtaken due to handover. Therefore, in this case, after receiving the handover completion information, the playback speed calculation unit 56 adds a slight time ⁇ (for example, reception for several packets) to the delay time difference between the handover source and the handover destination. It is determined whether or not the time obtained by adding (time) has elapsed (step S21). If not, the process returns to step S20.
- ⁇ for example, reception for several packets
- the reproduction speed calculation unit 56 periodically acquires the packet accumulation amount in the jitter buffer 47 by the jitter buffer monitoring unit 50 (step S22), and the packet accumulation amount exceeds the standard amount. It is determined whether or not (step S23).
- the standard amount of the packet accumulation amount is set in advance based on the packet transmission interval by the application being executed and the downlink jitter at the handover destination, and is stored in the reproduction speed calculation unit 56.
- step S23 If the result of determination in step S23 is that the packet accumulation amount is greater than or equal to the standard amount, the playback speed calculation unit 56 degrades the call quality from the normal playback speed according to the application so far. It is set to a high speed (for example, a speed that is 15% faster than the normal speed) not to be generated (step S24). Thereafter, when the packet accumulation amount in the jitter buffer 47 becomes equal to or less than the standard amount (step S25), the control is returned to the normal control, and the reproduction speed of the application is set to the normal speed (step S26). Accordingly, in step S26, when the adaptive jitter buffer function is turned off in step S14, the jitter buffer control unit 51 is instructed to turn on (activate) the adaptive jitter buffer function.
- a high speed for example, a speed that is 15% faster than the normal speed
- step S23 when the packet accumulation amount is less than the standard amount, the playback speed calculation unit 56 changes the playback speed of the application from the normal playback speed according to the previous application.
- the speed is low enough not to deteriorate the call quality (for example, a speed 15% slower than the normal speed) (step S27).
- step S28 Thereafter, when the packet accumulation amount in the jitter buffer 47 becomes equal to or larger than the standard amount (step S28), the process proceeds to step S26.
- T2 Tddn2- Tddn1
- FIG. 6 is an explanatory diagram showing the flow of packets during handover by the radio communication apparatus 11 according to the present embodiment and the operation of the jitter buffer 47 in correspondence with each other.
- CN corresponds to the counterpart communication terminal 12
- HA corresponds to the home agent 23
- MN corresponds to the radio communication apparatus 11 according to the present embodiment.
- FIG. 6 shows that the received packet has no jitter in each of the first wireless communication network 15 that is the handover source and the second wireless communication network 16 that is the handover destination.
- FIG. 7 is a diagram showing an operation state of the jitter buffer 47 in the wireless communication apparatus 11 according to the present embodiment, where FIG. 7A shows the number of received packets per unit time, FIG. 7B shows the playback speed, and FIG. 7 (c) indicates the number of packets (packet accumulation amount) in the jitter buffer 47.
- the wireless communication apparatus 11 receives the handover completion information from the HA 23, and if the jitter buffer 47 has an adaptive jitter buffer function, the function is performed.
- the buffer size By setting the buffer size to OFF and expanding the buffer size as necessary, it is possible to prevent incoming packets from being discarded without entering the jitter buffer 47, and to read the packets in the jitter buffer 47 in the order of time stamps at normal speed. At normal playback speed.
- the reproduction speed of the jitter buffer 47 (application reproduction speed).
- the packet is reproduced at high speed in the order of time stamps at a speed that is + 15% faster than the normal speed.
- the number of packets in the jitter buffer 47 decreases as shown in FIG.
- you turn off the adaptive jitter buffer function turn it on and play the app at normal playback speed. To do.
- the radio communication apparatus 11 when the radio communication apparatus 11 according to the present embodiment performs handover from the first radio communication network 15 to the second radio communication network 16, the downlink absolute delay time of the second radio communication network 16 that is the handover destination.
- the downlink absolute delay time of the first wireless communication network 15 that is the handover source is shorter, even if a packet overtaking occurs, the packet is stored in the jitter buffer 47 without being discarded as necessary.
- the buffer size of the jitter buffer 47 is increased.
- the application is played back at a speed higher than the normal playback speed, and after the number of packets in the jitter buffer 47 becomes less than the standard amount, the application is returned to the normal playback speed. Control playback speed.
- the present invention is not limited to the above embodiment, and many variations or modifications are possible.
- the present invention is not limited to a wireless communication apparatus that executes a VoIP application, but is also effective for a wireless communication apparatus that executes a real-time communication application such as streaming playback of multimedia data such as video and music.
- the application execution unit may be configured by a multimedia function unit having a similar jitter buffer control function instead of the telephone function unit.
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Abstract
Description
第1無線通信ネットワークおよび該第1無線通信ネットワークと異なる第2無線通信ネットワークに接続して無線通信を実行する無線通信部と、
該無線通信部を介してリアルタイム通信系のアプリケーションを実行する実行部と、
前記無線通信部を介して受信される、前記実行部が実行している前記アプリケーションのパケットを一時的に蓄積してジッタを吸収するためのジッタバッファと、
前記第1無線通信ネットワークにおける無線リンクの通信品質を取得する通信品質取得部と、
該通信品質取得部により取得した前記通信品質に基づいて、前記第1無線通信ネットワークから前記第2無線通信ネットワークへのハンドオーバを開始するハンドオーバ制御部と、
該ハンドオーバ制御部によるハンドオーバが完了してから、前記無線通信部を介して受信される前記アプリケーションのパケットの受信間隔が所定値以上になると、前記ジッタバッファのパケット蓄積量に基づいて、当該アプリケーションの再生速度を制御する制御部と、
を備えることを特徴とするものである。
前記制御部は、前記ジッタバッファのパケット蓄積量が閾値以上の場合に、当該アプリケーションの再生速度を速くすることを特徴とするものである。
前記制御部は、当該アプリケーションを速く再生している際に、前記ジッタバッファのパケット蓄積量が前記閾値を下回ると、当該アプリケーションの再生速度を通常の速度に戻すことを特徴とするものである。
前記ジッタバッファのバッファサイズを、当該アプリケーションのパケットの受信状況に応じて制御するアダプティブジッタ制御部、をさらに備え、
該アダプティブジッタ制御部は、前記ハンドオーバ制御部によるハンドオーバの完了を検出すると、前記ジッタバッファのバッファサイズの制御を停止することを特徴とするものである。
12 相手通信端末
12a 送受話器
15 第1無線通信ネットワーク
15a 基地局
16 第2無線通信ネットワーク
16a アクセスポイント
17 パケットネットワーク
18 インターネット
21,22 SIPサーバ
23 ホームエージェント(HA)
31 第1無線I/F
32 第2無線I/F
33 電話機能部
34 通信処理部
35 無線情報取得部
36 ハンドオーバ制御部
47 ジッタバッファ
50 ジッタバッファ監視部
51 ジッタバッファ制御部
55 ハンドオーバ情報取得部
56 再生速度計算部
ハンドオーバ制御部36は、ハンドオーバの予定を決定したら、電話機能部33および/または通信処理部34を制御して、無線通信装置11と時間同期しているHA23に対して送信タイムスタンプを有する計測用パケットの送信を要求する。これにより、HA23から、第1無線通信ネットワーク15および第2無線通信ネットワーク16の双方に計測用パケットを送信させる。無線通信装置11は、HA23から送信された計測用パケットを、対応する第1無線I/F31および第2無線I/F32を介してそれぞれ受信し、その受信時刻と計測用パケットのタイムスタンプとから、対応するネットワークの下り絶対遅延時間Tddn1およびTddn2を計測する。なお、ハンドオーバ元の無線通信ネットワークの下り絶対遅延時間が、通話中の受信パケットから計測できる場合には、当該無線通信ネットワークへの計測用パケットの送出は省略することができる。
ハンドオーバ制御部36は、ハンドオーバの予定を決定したら、電話機能部33および/または通信処理部34を制御して、無線通信装置11と時間同期しているHA23に対してその旨を通知する。これにより、上記第1の絶対遅延時間取得方法と同様に、HA23から、第1無線通信ネットワーク15および第2無線通信ネットワーク16の双方に計測用パケットを送信させて、対応するネットワークの下り絶対遅延時間Tddn1およびTddn2を計測する。
ハンドオーバ制御部36は、ハンドオーバの予定を決定したら、電話機能部33および/または通信処理部34を制御して、無線通信装置11から該無線通信装置11と時間同期しているHA23に対して、第1無線通信ネットワーク15および第2無線通信ネットワーク16の双方から、PINGやRTCP等の計測用パケットを送信させ、その返信を受信して、対応するネットワークの下り絶対遅延時間Tddn1およびTddn2を計測する。
ハンドオーバ制御部36は、ハンドオーバの予定を決定すると、IEEE802.21において検討されているハンドオーバ技術を利用して、各無線通信ネットワークの絶対遅延時間を取得する。その取得方法を以下に例示する。
無線通信装置11は、第1無線通信ネットワーク15の第1インフォメーションサーバに保持されている次の値を取得する。
・遅延時間を計測するために動作する計測用サーバ(例えば、インターネット18の基幹ネットワーク網に接続しているものとする)から第1無線通信ネットワーク15で接続している現在の基地局15aまでの片道遅延時間の標準値(Tn3)
・基地局15aとそこに繋がる端末との間の上下の遅延時間の標準値(下り:Trdn3,上り:Trup3)
さらに、無線通信装置11は、PING等の計測用パケットをHA23に対して送信し、その返信を受信して、無線通信装置11とHA23との間の往復遅延時間Trt1を計測する。
そして、これらの値から第1無線通信ネットワーク15の絶対遅延時間Tddn1を、下記の(1)式に従って計算する。ただし、基地局15aとHA23との間の片道遅延時間が取得できないため、この片道遅延時間をTn3と、{Trt1-(Tn3+Trdn3+Tn3+Trup3)}/2との加算により近似値とする。
[数1]
Tddn1=Tn3+Trdn3+{Trt1-(Tn3+Trdn3+Tn3+Trup3)}/2 ・・・(1)
無線通信装置11は、第1無線通信ネットワーク15の第1インフォメーションサーバを経由して、ハンドオーバ先の第2無線通信ネットワーク16に接続されている第2インフォメーションサーバに保持されている次の値を取得する。なお、第2インフォメーションサーバへは、無線通信装置11または基地局15aで取得した無線通信装置11の位置情報を送信する。
・無線通信装置11が接続されると予想されるアクセスポイント16aと計測用サーバとの間の片道遅延時間の標準値(Tn4)
・アクセスポイント16aとそこに繋がる端末との間の上下の遅延時間の標準値(下り:Trdn4,上り:Trup4)
そして、これらの値から第2無線通信ネットワーク16の絶対遅延時間Tddn2を、下記の(2)式に従って計算する。ただし、アクセスポイント16aとHA23との間の片道遅延時間が取得できないため、この片道遅延時間をTn4と、{Trt1-(Tn3+Trdn3+Tn3+Trup3)}/2との加算により近似値とする。
[数2]
Tddn2=Tn4+Trdn4+{Trt1-(Tn3+Trdn3+Tn3+Trup3)}/2 ・・・(2)
Claims (4)
- 第1無線通信ネットワークおよび該第1無線通信ネットワークと異なる第2無線通信ネットワークに接続して無線通信を実行する無線通信部と、
該無線通信部を介してリアルタイム通信系のアプリケーションを実行する実行部と、
前記無線通信部を介して受信される、前記実行部が実行している前記アプリケーションのパケットを一時的に蓄積してジッタを吸収するためのジッタバッファと、
前記第1無線通信ネットワークにおける無線リンクの通信品質を取得する通信品質取得部と、
該通信品質取得部により取得した前記通信品質に基づいて、前記第1無線通信ネットワークから前記第2無線通信ネットワークへのハンドオーバを開始するハンドオーバ制御部と、
該ハンドオーバ制御部によるハンドオーバが完了してから、前記無線通信部を介して受信される前記アプリケーションのパケットの受信間隔が所定値以上になると、前記ジッタバッファのパケット蓄積量に基づいて、当該アプリケーションの再生速度を制御する制御部と、
を備えることを特徴とする無線通信装置。 - 前記制御部は、前記ジッタバッファのパケット蓄積量が閾値以上の場合に、当該アプリケーションの再生速度を速くすることを特徴とする請求項1に記載の無線通信装置。
- 前記制御部は、当該アプリケーションを速く再生している際に、前記ジッタバッファのパケット蓄積量が前記閾値を下回ると、当該アプリケーションの再生速度を通常の速度に戻すことを特徴とする請求項2に記載の無線通信装置。
- 前記ジッタバッファのバッファサイズを、当該アプリケーションのパケットの受信状況に応じて制御するアダプティブジッタ制御部、をさらに備え、
該アダプティブジッタ制御部は、前記ハンドオーバ制御部によるハンドオーバの完了を検出すると、前記ジッタバッファのバッファサイズの制御を停止することを特徴とする請求項1に記載の無線通信装置。
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US12/810,818 US8879501B2 (en) | 2007-12-27 | 2008-12-26 | Wireless communication apparatus |
EP08867286.0A EP2227054A4 (en) | 2007-12-27 | 2008-12-26 | RADIO COMMUNICATION DEVICE |
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WO2013025146A2 (en) * | 2011-08-17 | 2013-02-21 | Telefonaktiebolaget L M Ericsson (Publ) | Method and controlling network node in a radio access network |
US20130094472A1 (en) * | 2011-10-14 | 2013-04-18 | Qualcomm Incorporated | Methods and apparatuses for reducing voice/data interruption during a mobility procedure |
EP2862389B1 (en) * | 2012-06-13 | 2017-10-04 | Telefonaktiebolaget LM Ericsson (publ) | Handover prediction using historical data |
ES2667823T3 (es) | 2013-06-21 | 2018-05-14 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Escalador de tiempo, decodificador de audio, procedimiento y programa informático mediante el uso de un control de calidad |
PL3011692T3 (pl) | 2013-06-21 | 2017-11-30 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Sterowanie buforem rozsynchronizowania, dekoder sygnału audio, sposób i program komputerowy |
JP6464397B2 (ja) * | 2014-02-19 | 2019-02-06 | 株式会社高砂製作所 | 音声通信装置 |
US9918264B1 (en) * | 2016-09-09 | 2018-03-13 | Qualcomm Incorporated | Reporting of information before a scheduled time |
CN109792447B (zh) * | 2017-04-21 | 2020-11-06 | 华为技术有限公司 | 应用数据迁移方法及网络设备 |
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