WO2009107587A1 - 無線通信装置 - Google Patents
無線通信装置 Download PDFInfo
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- WO2009107587A1 WO2009107587A1 PCT/JP2009/053223 JP2009053223W WO2009107587A1 WO 2009107587 A1 WO2009107587 A1 WO 2009107587A1 JP 2009053223 W JP2009053223 W JP 2009053223W WO 2009107587 A1 WO2009107587 A1 WO 2009107587A1
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- wireless communication
- communication network
- handover
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- jitter buffer
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- 238000004891 communication Methods 0.000 title claims abstract description 259
- 238000012544 monitoring process Methods 0.000 claims description 16
- 238000005259 measurement Methods 0.000 claims description 5
- 230000000593 degrading effect Effects 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 22
- 230000006870 function Effects 0.000 description 20
- 238000010586 diagram Methods 0.000 description 13
- 230000008859 change Effects 0.000 description 11
- 238000012545 processing Methods 0.000 description 11
- 230000005540 biological transmission Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000002542 deteriorative effect Effects 0.000 description 2
- 230000001413 cellular effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000000977 initiatory effect 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
- H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
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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
- H04W36/26—Reselection being triggered by specific parameters by agreed or negotiated communication parameters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
- H04W24/04—Arrangements for maintaining operational condition
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/0005—Control or signalling for completing the hand-off
- H04W36/0011—Control or signalling for completing the hand-off for data sessions of end-to-end connection
- H04W36/0016—Hand-off preparation specially adapted for end-to-end data sessions
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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
- H04W36/304—Reselection being triggered by specific parameters by measured or perceived connection quality data due to measured or perceived resources with higher communication quality
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/02—Terminal devices
- H04W88/06—Terminal devices adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
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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. It changes, discards received packets, and changes the size of the jitter buffer.
- the downlink absolute delay time of the packet received by the communication terminal that is, the time (delay time) required until the packet transmitted from the partner communication terminal is received via the wireless communication network depends on the wireless communication network. Different. For this reason, in the case of a wireless communication apparatus in which a communication terminal moves, when handover is performed to a different wireless communication network, for example, if the downlink absolute delay time of the handover destination is longer than the downlink absolute delay time of the handover source, the difference As a result, a packet reception idle time is generated.
- the packet reading interval from the jitter buffer is set to a constant interval according to the application and the packet is reproduced at a constant reproduction speed
- the last packet received from the handover source wireless communication network is
- the reception idle time is longer than the time required for reading from the jitter buffer (that is, the jitter buffer standard delay time)
- the packet in the jitter buffer is emptied for the longer time.
- FIG. 10 is a diagram for explaining a jitter buffer control method in this case.
- 10A shows the number of packets received by the jitter buffer per unit time
- FIG. 10B shows the playback speed (reading interval) of packets from the jitter buffer
- FIG. Indicates the number of packets.
- FIG. 11 shows the packet flow in this case.
- “transmission” is the packet transmission timing by the counterpart communication terminal
- “reception” is the reception timing of the packet received by the jitter buffer of the wireless communication device
- “reproduction” is the packet reproduction timing by the wireless communication device. (Packet read timing from the jitter buffer) is shown.
- 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 downlink absolute delay time TddnB in the handover destination radio communication network B is longer than the downlink absolute delay time TddnA in the handover source radio communication network A, and (TddnB ⁇ TddnA).
- TddnB ⁇ TddnA
- TddnB ⁇ TddnA
- an absolute delay time for each wireless communication network that can be handed over is set in advance in a wireless communication device, a home agent, etc. It is considered that the reproduction speed is controlled so that a silent period does not occur on the basis of the set absolute delay time.
- the packet is read from the jitter buffer, that is, the jitter for controlling the packet reproduction rate is controlled. It is conceivable to adopt a buffer control method (see, for example, Patent Document 1).
- FIG. 12 is a diagram for explaining a playback speed control method when the jitter buffer control method disclosed in Patent Document 1 is adopted.
- 12 (a) to 12 (c) show the number of received packets per unit time of the jitter buffer, the reproduction speed, and the number of packets in the jitter buffer, respectively, as in FIGS. 10 (a) to 10 (c).
- FIG. 13 shows a packet flow in this case.
- the packet is received at the reception interval until then, as in the case of handover from the wireless communication network A having the downlink absolute delay time TddnA to the wireless communication network B having the downlink absolute delay time TddnB longer than TddnA. If the packet cannot be received, the reproduction speed of the packet in the jitter buffer is gradually reduced as the reception interval increases. Thereafter, when the reception interval returns to normal, the playback speed is controlled to gradually increase to the normal playback speed according to the number of packets in the jitter buffer.
- the playback speed will be reduced more than necessary.
- the playback speed greatly changes from the original voice speed, so that the quality of the playback sound is greatly reduced, resulting in a reduction in playback quality, making it difficult for the user to hear.
- the calculated delay time difference is shorter than the actual delay time difference, the amount of packets stored in the jitter buffer will be insufficient and silence will occur, making it impossible to achieve the initial purpose. .
- FIG. 12 and FIG. 13 show control examples in the case where the packet in the jitter buffer is empty and no silence is generated, but how much the packet reception interval is actually free. Is unknown. Therefore, depending on the jitter buffer standard delay time Ta and the handover destination downlink absolute delay time TddnB, there is a concern that the packet in the jitter buffer is emptied and silence is generated. Note that it is conceivable to increase the jitter buffer standard delay time Ta in order to prevent the occurrence of silence or the like. However, in this case, for example, in VoIP, there is a delay in packet reproduction from the counterpart terminal, so that real-time performance is lacking.
- an object of the present invention made in view of such a point is to provide a wireless communication apparatus capable of performing handover to a different wireless communication network without deteriorating reproduction quality and real-time property.
- 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 communication quality acquisition unit for acquiring communication quality of a radio link in the first wireless communication network while executing the application by connecting to the first wireless communication network; A determination unit that determines whether to start preparation for 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; When the determination unit determines the start of handover preparation during the execution of the application, an estimation unit that estimates a handover preparation time until the handover is started based on the communication quality acquired by the communication quality acquisition unit; When the determination unit determines the start of handover preparation, the first wireless communication network receives data via the first wireless communication network and the second wireless communication network, and based on the reception time of the received same data, A measurement unit for measuring a
- the invention according to a second aspect is the wireless communication device according to the first aspect,
- the control unit slows down the playback speed of the application by the execution unit when the reception time by the second wireless communication network is later than the reception time by the first wireless communication network by a predetermined time or more. It is a feature.
- the invention according to a third aspect is the wireless communication device according to the second aspect,
- the control unit slows down the playback speed of the application by the execution unit after starting preparation for handover.
- the invention according to a fourth aspect is the wireless communication apparatus according to the third aspect,
- the control unit slows the reproduction speed of the application by the execution unit so that the amount of data in the jitter buffer becomes zero at the start of data reception from the second wireless communication network. To do.
- the invention according to a fifth aspect is the wireless communication device according to the second aspect,
- the execution unit includes a jitter buffer that absorbs jitter of received data, and a jitter buffer monitoring unit that monitors the data amount of the jitter buffer, When the data amount of the jitter buffer monitored by the jitter buffer monitoring unit exceeds a predetermined amount after the handover to the second wireless communication network is completed, the control unit sets the playback speed of the application to a normal speed. It is characterized by returning.
- the preparation time until the handover is acquired in advance, and the first wireless communication network and the second wireless communication are also acquired.
- Each data is received via the network, and a delay time difference between the first wireless communication network and the second wireless communication network is acquired based on the reception time of the received same data.
- the playback speed of the application is controlled based on the acquired information and the amount of data in the jitter buffer when the start of handover preparation is determined.
- the reproduction speed of the application can be optimally controlled according to the actual radio state at the time of handover, so that the first wireless communication network to the second wireless communication network can be achieved without degrading the reproduction quality and real-time performance. Handover to is possible.
- FIG. 3 is a diagram for explaining a method for calculating a handover preparation time by the handover control unit shown in FIG. 2. It is a figure which shows the sequence at the time of the hand-over between the radio
- FIG. 4 is a diagram for explaining an example of a reception packet reproduction rate control method by a jitter buffer control unit shown in FIG. 3. It is a figure for demonstrating the example of control of the jitter buffer in the telephone function part shown in FIG. It is a figure for demonstrating an example of the control method of the conventional jitter buffer. It is a figure which shows the flow of the packet by the control method shown in FIG. It is a figure for demonstrating the other example of the control method of the conventional jitter buffer. It is a figure which shows the flow of the packet by the control method shown in FIG.
- Wireless communication equipment MN
- partner communication terminal 12a handset 15 first wireless communication network 15a access point 16 second wireless communication network 16a base station 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.
- the first wireless communication network 15 is assumed to be, for example, a wireless LAN (Local Area Network), and the second wireless communication network 16 is, for example, a mobile phone of cdma2000 1xEV-DO (Code Division Multiple Access Access 2000 2000 1x Evolution Data Data Only). Assume a network. It is assumed that the delay time (downlink absolute delay time) in the first radio communication network 15 is shorter than the delay time (downlink absolute delay time) in the second radio communication network 16.
- reference numeral 15 a indicates an access point of the first wireless communication network 15, and reference numeral 16 a indicates a base station 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) servers 21 and 22 for controlling communication are connected to the first wireless communication network 15 and the second wireless communication network 16, respectively. Further, on the Internet 18, a home agent (HA) 23 that transfers a received packet addressed to the wireless communication device 11 to a wireless communication network to which the wireless communication device 11 is connected, and an SIP server 24 that controls communication. And are connected.
- 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 partner communication terminal 12 via the first wireless communication network 15 and / or the second wireless communication network 16 and is controlled by the handover control unit 36.
- the connection of the first wireless I / F 31 and 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 whether to schedule a handover, that is, whether to start preparation for handover, and the handover information Based on the above, handover is controlled.
- 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. During the 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. Is done.
- 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 number of packets (data amount) in the jitter buffer 47 are monitored by the jitter buffer monitoring unit 50. Based on the monitoring result, the jitter buffer control unit 51 Processing such as a packet reading speed from the jitter buffer 47 and discarding of the received packet is controlled.
- the wireless communication apparatus 11 further includes a handover function acquisition unit 55 and a playback speed calculation unit 56 in addition to 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 playback speed calculation unit 56 reads the packet reading speed of the jitter buffer 47, that is, the playback speed of the received packet (in this embodiment, the playback speed of the VoIP application) ) Is determined.
- the reproduction speed calculation unit 56 calculates the reproduction speed of the received packet based on the acquired required handover information and the monitoring result of the jitter buffer 47 by the jitter buffer monitoring unit 50.
- the calculation result is supplied to the jitter buffer control unit 51.
- the jitter buffer control unit 51 controls reading of the received packet from the jitter buffer 47 so that the reproduction speed of the received packet becomes the reproduction speed calculated by the reproduction speed calculation unit 56. Therefore, in radio communication apparatus 11 according to the present embodiment, 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 base station 16a, for example.
- handover control unit 36 determines the handover schedule
- the handover control unit 36 acquires the handover preparation time T1 until the handover starts. Further, the handover control unit 36 receives data via the first wireless communication network 15 and the second wireless communication network 16, respectively, and based on the reception time of the received same data, the first wireless communication network 15 And a delay time difference T2 between the second wireless communication network 16 and the second wireless communication network 16.
- the handover control unit 36 supplies the acquired information as required handover information to the telephone function unit 33 together with information indicating that there is a handover schedule. Therefore, in radio communication apparatus 11 according to the present embodiment, handover control unit 36 includes a determination unit that determines whether to start preparation for handover, an estimation unit that estimates handover preparation time, and the first radio communication network.
- wireless communication network 16 is comprised.
- the handover preparation time T1 is calculated based on a unit time change rate ⁇ Rs (slope) of the radio state (Rs) for determining communication quality.
- the rate of change ⁇ Rs can be measured and acquired when the radio state falls below the handover schedule determination threshold and the handover schedule is determined, but in this embodiment, the handover schedule determination is performed during the call.
- the change rate average value ⁇ Rsrms from the time point to a predetermined time before is acquired.
- the handover control unit 36 calculates the change rate ⁇ Rs (t) of the radio unit time ( ⁇ t) in the currently used radio communication network at a predetermined timing according to the following equation (1).
- a plurality of change rates ⁇ Rs (t) up to a time before (for example, 2 seconds before) are held in the memory.
- the change rate average value ⁇ Rsrms up to a predetermined time held at that time is calculated.
- ⁇ Rs (t)
- the handover control unit 36 determines whether or not the calculated change rate average value ⁇ Rsrms is smaller than a preset change rate threshold value Rsref.
- the handover preparation time T1 is set to a preset standard time Tref (for example, 5 sec) as shown in FIG. To do.
- T1 Tref (Rsref / ⁇ Rsrms) is calculated, and as the change rate ⁇ Rsrms increases, the handover preparation time T1 Is set shorter than the standard time Tref.
- FIG. 4B shows a case where ⁇ Rsrms> Rsref and the handover preparation time T1 is set to approximately half the standard time Tref (2.5 sec).
- the delay time difference T2 is measured from the reception time of the received same packet when the packet from the counterpart communication terminal 12 is received via the first wireless communication network 15 and the second wireless communication network 16, respectively.
- FIG. 5 is a diagram illustrating a sequence at the time of handover between the wireless communication device (MN) 11 and the HA 23.
- the handover control unit 36 controls the communication processing unit 34 to connect the second wireless I / F 32 to the second wireless communication network 16.
- the handover control unit 36 transmits Registration Request (Binding Update in NEMO) to the HA 23 via the second wireless communication network 16 that is the handover destination, and the care-of address of the handover destination (second wireless CoA) to the HA 23.
- Registration Request Biting Update in NEMO
- the handover control unit 36 receives RegistrationRegReply (Binding Acknowledge in NEMO), which is registered information returned from the HA 23, and the first wireless communication network 15 and the second wireless communication with the counterpart communication terminal 12. Control is performed so that communication is performed using both communication networks 16. Thereby, the handover control unit 36 measures the delay time difference (reception time difference) T2 from the reception time of the same packet received via the first wireless communication network 15 and the second wireless communication network 16, respectively.
- RegistrationRegReply Biting Acknowledge in NEMO
- the reception time difference of the same packet is a value obtained by subtracting the reception time by the first wireless communication network 15 from the reception time by the second wireless communication network 16. Then, as shown in FIG. 6, the average value of the reception time differences in a predetermined number of the same packets respectively received via the first wireless communication network 15 and the second wireless communication network 16 is acquired as the delay time difference T2.
- the communication processing unit 34 monitors packets received via the first wireless communication network 15 and the second wireless communication network 16, and supplies the packets received earlier to the telephone function unit 33 for the same packet.
- the handover control unit 36 acquires the handover preparation time T1, the delay time difference T2 between the first wireless communication network 15 and the second wireless communication network 16, and uses the acquired information as the telephone function unit. 33.
- the handover control unit 36 performs handover to the HA 23 via the first wireless communication network 15 that is the handover source as shown in FIG. 5 when the handover preparation time T1 has elapsed.
- Unregistration indicating the start of the request that is, Registration Request with Lifetime 0 (Binding Update with Lifetime 0 in NEMO) is transmitted to request HA 23 to deregister the handover source care-of address (first wireless CoA).
- the handover control unit 36 receives Registration Reply (Binding Acknowledge in NEMO), which is handover completion information returned from the HA 23, via the first wireless communication network 15, and then the first wireless communication network 15 that is the handover source. 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. .
- Registration Reply Biting Acknowledge in NEMO
- FIG. 7 is a sequence diagram showing the operation of the main part of the telephone function unit 33.
- the handover information acquisition unit 55 monitors the handover information from the handover control unit 36 at regular intervals. As a result, when the information that there is a handover schedule is acquired, the handover information acquisition unit 55 further acquires a handover preparation time T1 and a delay time difference T2 that are required handover information from the handover control unit 36, The acquired required handover information is supplied to the reproduction speed calculation unit 56.
- the playback speed calculation unit 56 first determines whether or not the delay time difference T2 exceeds a predetermined value (> 0), that is, the second wireless communication at the handover destination. It is determined whether or not the downlink absolute delay time in the network 16 exceeds the downlink absolute delay time in the first wireless communication network 15 that is the handover source by exceeding a predetermined value.
- the playback speed calculation unit 56 for example, based on the acquired required handover information and the monitoring result of the jitter buffer 47 by the jitter buffer monitoring unit 50, for example, the handover destination
- the reproduction speed V of the received packet in the jitter buffer 47 is calculated from the following equation (2) so that the number of packets in the jitter buffer 47 becomes zero at the start of reception of the packet from the second wireless communication network 16.
- V1 represents a standard reproduction speed.
- Tb indicates a time corresponding to the number of packets (data amount) in the jitter buffer 47 at the time when information indicating that there is a handover schedule is received.
- the playback speed V calculated by the playback speed calculator 56 is supplied to the jitter buffer controller 51.
- the jitter buffer control unit 51 controls reading of the received packet from the jitter buffer 47 so as to reproduce the received packet at a reproduction speed V lower than the standard reproduction speed.
- the playback speed control of the received packet by the jitter buffer controller 51 is executed by, for example, one of the first playback speed control method and the second playback speed control method described below.
- First playback speed control method TR1 is the packet reading interval from the jitter buffer 47 with respect to the standard playback speed V1, and (Tb + T1 ⁇ V1) / (T1 + T2) in the above equation (2) is calculated as k.
- TR TR1 / k.
- the [ ⁇ V1 / (V1-V) ⁇ -1] -th read packet is copied and stored in the memory in the decoder 48, and the copy source packet is stored. After reproduction, the copied packet is read and reproduced at the next reproduction timing.
- the reproduction speed V is set to 80% of the standard reproduction speed V1
- the sequential four packets P1 to P4 in the jitter buffer 47 are sequentially read and reproduced, The fourth packet P4 is copied, and the copied packet P4 ′ is reproduced at the next reproduction timing after reproducing the copy source packet P4.
- the TD of the above equation (3) is increased by the reproduction interval time by copying. If the [ ⁇ V1 / (V1-v) ⁇ -1] packet to be read has not arrived or is discarded and is not in the jitter buffer 47, the packet for the next reproduction timing is The same processing is performed.
- the jitter buffer control unit 51 executes the reproduction speed control of the received packet. Thereafter, when the handover information acquisition unit 55 acquires the handover completion information from the handover control unit 36, the playback speed calculation unit 56 acquires the packet reception interval time from the jitter buffer monitoring unit 50 at regular intervals, and acquires the received reception. An average value of the interval time in a predetermined time is calculated, and it is monitored whether or not a difference between the calculated packet reception interval average value and a standard reception interval in the VoIP application is within a threshold value.
- the playback speed calculation unit 56 determines that the packet from the handover destination has been received, and determines the number of packets (data amount) in the jitter buffer 47 at that time as the jitter buffer. It is acquired from the monitoring unit 50, and it is determined whether or not the acquired number of packets exceeds a predetermined amount.
- Ta is a jitter buffer standard delay time corresponding to the standard number of packets in the jitter buffer 47.
- the playback speed calculation unit 56 instructs the jitter buffer control unit 51 to immediately return to the normal playback speed control.
- the jitter buffer control unit 51 returns the standard playback speed V1 when the number of packets in the jitter buffer 47 exceeds a predetermined amount. The reading of the jitter buffer 47 is controlled.
- FIG. 9 is a diagram for explaining a control method of the jitter buffer 47 according to the present embodiment.
- (a) is the number of packets that the jitter buffer 47 receives per unit time
- (b) is the reproduction speed (reading interval) of packets from the jitter buffer 47
- (c) is in the jitter buffer 47. Indicates the number of packets.
- radio communication apparatus 11 when handover is performed from first radio communication network 15 having a short absolute delay time to second radio communication network 16 having a long absolute delay time, Since the preparation time T1 until the handover and the delay time difference T2 are acquired, know how long the packet does not arrive after the time when the start of the handover preparation is decided Can do.
- the first wireless communication network takes a long time from the time when the start of the handover preparation is determined so that the packet received from the first wireless communication network 15 that is the handover source can be reproduced even during the period when the packet does not arrive. Since the playback speed V can be controlled so as to absorb the delay time difference T2 between the 15 and the second wireless communication network 16, the difference from the standard playback speed V1 can be reduced.
- the delay time difference T2 between the first wireless communication network 15 and the second wireless communication network 16 is acquired from the reception time of the received same packet. Therefore, compared with the case of acquiring a delay time difference using an absolute delay time set in advance for each wireless communication system, it is possible to acquire an accurate delay time difference T2 corresponding to an actual wireless state.
- the playback speed can be optimally controlled.
- the playback speed of the application after the handover schedule is determined is controlled so that the number of packets in the jitter buffer 47 becomes zero at the start of reception of packets from the handover destination.
- the time that can be taken to absorb the delay time difference between the first wireless communication network 15 that is the handover source and the second wireless communication network 16 that is the handover destination can be further increased. Therefore, the application can be played back at a constant playback speed that is closer to the standard playback speed, so that the handover from the first wireless communication network 15 to the second wireless communication network 16 can be performed without reducing the playback quality and real-time performance. Is possible.
- the present invention is not limited to the above embodiment, and many variations or modifications are possible.
- the playback speed calculation unit 56 calculates the playback speed V
- the number of packets in the jitter buffer 47 becomes 0 at the start of reception of packets from the handover destination. It is also possible to calculate the reproduction speed V so that the number of packets in the jitter buffer 47 becomes a predetermined number at the start of receiving the previous packet.
- the present invention is not limited to the case of executing a VoIP application, but can also be effectively applied to the case of executing 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.
- the present invention is not limited to handover between a wireless LAN and cdma2000 1xEV-DO, but other wireless communication networks such as PDC (Personal Digital Cellular), W-CDMA (Wideband CDMA), PHS (Personal Handy- Effective for handover between any different wireless communication networks such as phone (System), Bluetooth, WiMAX (Worldwide Interoperability for Microwave Access), LTE (Long Term Evolution), UMB (Ultra Mobile Broadband), IMT-Advanced etc. Can be applied.
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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、
前記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、
前記第1無線通信ネットワークに接続して前記アプリケーションを実行中に、当該第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の準備を開始するか否かを決定する決定部と、
前記アプリケーションの実行中に、前記決定部がハンドオーバ準備の開始を決定すると、前記通信品質取得部が取得した通信品質に基づいてハンドオーバを開始するまでのハンドオーバ準備時間を推定する推定部と、
前記決定部がハンドオーバ準備の開始を決定すると、前記第1無線通信ネットワークおよび前記第2無線通信ネットワークを介してそれぞれデータを受信して、受信した同一データの受信時間に基づいて、前記第1無線通信ネットワークと前記第2無線通信ネットワークとの間の遅延時間差を計測する計測部と、
前記推定部により推定したハンドオーバ準備時間と、前記計測部により計測した遅延時間差と、前記決定部がハンドオーバ準備の開始を決定した時点での前記ジッタバッファ監視部による前記ジッタバッファ内のデータ量とに基づいて、前記実行部による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、前記第2無線通信ネットワークによる受信時間の方が、前記第1無線通信ネットワークによる受信時間よりも所定時間以上遅い場合に、前記実行部による当該アプリケーションの再生速度を遅くすることを特徴とするものである。
前記制御部は、ハンドオーバの準備を開始してから、前記実行部による当該アプリケーションの再生速度を遅くすることを特徴とするものである。
前記制御部は、前記第2無線通信ネットワークからのデータの受信開始時点で、前記ジッタバッファ内のデータ量が0となるように、前記実行部による当該アプリケーションの再生速度を遅くすることを特徴とするものである。
前記実行部は、受信したデータのジッタを吸収するジッタバッファと、該ジッタバッファのデータ量を監視するジッタバッファ監視部と、を備え、
前記制御部は、前記第2無線通信ネットワークへのハンドオーバが完了した後、前記ジッタバッファ監視部が監視する前記ジッタバッファのデータ量が所定量を超えると、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。
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 アクセスポイント
16 第2無線通信ネットワーク
16a 基地局
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
ハンドオーバ準備時間T1は、例えば、図4(a)および(b)に示すように、通信品質を決定する無線状態(Rs)の単位時間の変化率ΔRs(傾き)に基づいて算出する。ここで、変化率ΔRsは、無線状態がハンドオーバ予定決定閾値を下回ってハンドオーバ予定を決定した時点で計測して取得することもできるが、本実施の形態では、当該通話中において、ハンドオーバの予定決定時点から所定時間前までの変化率平均値ΔRsrmsを取得する。
[数1]
ΔRs(t)=|{Rs(t)-Rs(t-Δt)}/Δt| ・・・(1)
遅延時間差T2は、相手通信端末12からのパケットを、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を介してそれぞれ受信し、その受信した同一パケットの受信時間から計測する。
[数2]
V=(Tb+T1×V1)/(T1+T2) ・・・(2)
標準再生速度V1に対するジッタバッファ47からのパケットの読み出し間隔をTR1、上記(2)式における(Tb+T1×V1)/(T1+T2)をk、算出した再生速度Vに対応するジッタバッファ47からのパケットの読み出し間隔をTR、するとき、TR=TR1/k、とする。例えば、標準再生速度V1では、ジッタバッファ47内のパケットを20msecの間隔で読み出して再生するVoIPアプリの場合において、再生速度Vを標準再生速度V1の80%(k=0.8)とする場合には、ジッタバッファ47からのパケットの読み出し間隔TRを、TR=20/0.8(msec)、とする。
ハンドオーバのための再生速度のコントロールを開始したら、その直後に再生したパケット(最初のパケット)のタイムスタンプと、その再生時間とを組み合わせて記録する。その後のパケットについては、下記(3)式で示す時間Tvに、ジッタバッファ47から読み出して再生する。なお、(3)式において、TDは、遅延時間で、初期値は0である。
[数3]
Tv=(パケットのタイムスタンプ-最初のパケットのタイムスタンプ)+(最初のパケットの再生時間+TD) ・・・(3)
Claims (5)
- 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、
前記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、
前記第1無線通信ネットワークに接続して前記アプリケーションを実行中に、当該第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の準備を開始するか否かを決定する決定部と、
前記アプリケーションの実行中に、前記決定部がハンドオーバ準備の開始を決定すると、前記通信品質取得部が取得した通信品質に基づいてハンドオーバを開始するまでのハンドオーバ準備時間を推定する推定部と、
前記決定部がハンドオーバ準備の開始を決定すると、前記第1無線通信ネットワークおよび前記第2無線通信ネットワークを介してそれぞれデータを受信して、受信した同一データの受信時間に基づいて、前記第1無線通信ネットワークと前記第2無線通信ネットワークとの間の遅延時間差を計測する計測部と、
前記推定部により推定したハンドオーバ準備時間と、前記計測部により計測した遅延時間差と、前記決定部がハンドオーバ準備の開始を決定した時点での前記ジッタバッファ監視部による前記ジッタバッファ内のデータ量とに基づいて、前記実行部による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、前記第2無線通信ネットワークによる受信時間の方が、前記第1無線通信ネットワークによる受信時間よりも所定時間以上遅い場合に、前記実行部による当該アプリケーションの再生速度を遅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、ハンドオーバの準備を開始してから、前記実行部による当該アプリケーションの再生速度を遅くすることを特徴とする請求項2に記載の無線通信装置。
- 前記制御部は、前記第2無線通信ネットワークからのデータの受信開始時点で、前記ジッタバッファ内のデータ量が0となるように、前記実行部による当該アプリケーションの再生速度を遅くすることを特徴とする請求項3に記載の無線通信装置。
- 前記実行部は、受信したデータのジッタを吸収するジッタバッファと、該ジッタバッファのデータ量を監視するジッタバッファ監視部と、を備え、
前記制御部は、前記第2無線通信ネットワークへのハンドオーバが完了した後、前記ジッタバッファ監視部が監視する前記ジッタバッファのデータ量が所定量を超えると、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。
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EP2323438A3 (en) * | 2009-11-12 | 2014-07-30 | Samsung Electronics Co., Ltd. | Method and apparatus for reducing loss of media data while handover is performed |
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JP6501589B2 (ja) * | 2015-03-31 | 2019-04-17 | キヤノン株式会社 | 通信装置、通信装置の制御方法、及びプログラム |
US10290303B2 (en) * | 2016-08-25 | 2019-05-14 | Google Llc | Audio compensation techniques for network outages |
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JP2007214985A (ja) * | 2006-02-10 | 2007-08-23 | Kddi Corp | シームレスハンドオーバにおけるメディアストリーム切替方法、システム及びプログラム |
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