WO2009119764A1 - 無線通信装置 - Google Patents
無線通信装置 Download PDFInfo
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- WO2009119764A1 WO2009119764A1 PCT/JP2009/056177 JP2009056177W WO2009119764A1 WO 2009119764 A1 WO2009119764 A1 WO 2009119764A1 JP 2009056177 W JP2009056177 W JP 2009056177W WO 2009119764 A1 WO2009119764 A1 WO 2009119764A1
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- WIPO (PCT)
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- wireless communication
- communication network
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- handover
- jitter buffer
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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
- 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
- H04W36/0005—Control or signalling for completing the hand-off
- H04W36/0055—Transmission or use of information for re-establishing the radio link
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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
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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
- 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
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 the propagation environment such as fading, and the change in the allowable bandwidth is in accordance with the change of the allowable bandwidth.
- the arrival interval of packets received by the communication terminal also changes.
- 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. 12 is a diagram for explaining a jitter buffer control method in this case. 12, (a) is the number of packets that the jitter buffer receives per unit time, (b) is the reproduction speed (reading interval) of packets from the jitter buffer, and (c) is the number of packets in the jitter buffer. Respectively.
- FIG. 13 shows a 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 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
- FIG. 14 is a diagram for explaining a jitter buffer control method disclosed in Patent Document 1. 14, (a) to (c) 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, respectively, as in (a) to (c) of FIG. .
- FIG. 15 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, control is performed so that the reproduction speed is gradually increased to the standard reproduction speed in accordance with the number of packets in the jitter buffer.
- FIG. 14 and FIG. 15 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 degrading 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; A jitter buffer and a jitter buffer monitoring unit that monitors a data amount of the jitter buffer, and 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; Based on the communication quality acquired by the communication quality acquisition unit, a changing unit that changes the accumulation upper limit value of the jitter buffer; A control unit for controlling the playback speed of the application by the execution unit based on the change of the upper limit value of the jitter buffer by the change unit; 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
- the invention according to a second aspect is the wireless communication device according to the first aspect,
- the control unit compares the delay time in the first radio communication network with the delay time in the second radio communication network, and determines the delay time in the second radio communication network. In this case, when the delay time in the first wireless communication network is longer than a predetermined time, the playback speed of the application by the execution unit is reduced.
- the invention according to a third aspect is the wireless communication device according to the second aspect,
- the control unit determines that the amount of data in the jitter buffer corresponds to the standard reproduction speed of the application at the start of data reception from the second wireless communication network.
- the playback speed of the application by the execution unit is slowed down so as to be a predetermined amount.
- the invention according to a fourth aspect is the wireless communication apparatus according to the third aspect, When the control unit completes the handover to the second wireless communication network, the control unit returns the playback speed of the application to a standard playback speed.
- the invention according to a fifth aspect is the wireless communication device according to the first aspect,
- the change unit has a plurality of different change thresholds for changing the accumulation upper limit value of the jitter buffer, and based on the comparison between the communication quality from the communication quality acquisition unit and the plurality of change thresholds, The communication quality from the communication quality acquisition unit is changed to increase the accumulation upper limit value of the jitter buffer as the determination unit approaches the handover schedule determination threshold value of the first wireless communication network. It is.
- An invention according to a sixth aspect is the wireless communication apparatus according to the fifth aspect,
- the control unit based on a comparison between the accumulation upper limit value of the jitter buffer set by the changing unit and the data amount in the jitter buffer by the jitter buffer monitoring unit, the data amount and the accumulation upper limit value If equal, the playback speed of the application is set as a standard playback speed, and if the data amount is smaller than the storage upper limit value, the first playback speed is lower than the standard playback speed, and the data amount is the storage speed.
- the playback speed of the application is controlled so that the second playback speed is higher than the standard playback speed.
- the invention according to a seventh aspect is the wireless communication device according to the sixth aspect,
- the speed increase of the second playback speed with respect to the standard playback speed is made smaller than the speed decrease of the first playback speed with respect to the standard playback speed.
- the invention according to an eighth aspect is the wireless communication device according to the fifth, sixth or seventh aspect,
- the change unit includes an increase change threshold to be applied when the communication quality from the communication quality acquisition unit is lower than the same accumulation upper limit value of the jitter buffer, and the communication quality from the communication quality acquisition unit. And a decrease change threshold value that is lower than the increase change threshold value, which is applied when the value exceeds.
- the preparation time until the handover and the first wireless communication network and the second wireless communication network in advance For example, when the delay time of the second wireless communication network that is the handover destination is longer than the delay time of the first wireless communication network that is the handover source, from the time when the start of the handover preparation is determined It is possible to know how long a packet does not arrive after a certain amount of time has elapsed. As a result, the first wireless communication 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 as the handover source can be reproduced even during the period when the packet does not arrive due to the handover.
- the playback speed can be controlled so as to absorb the delay time difference between the network and the second wireless communication network. Moreover, before determining the start of handover preparation, the communication quality of the radio link in the first wireless communication network is acquired, and the storage upper limit value of the jitter buffer is changed based on the acquired communication quality. Control the playback speed of the application based on the value change. As a result, even when the time from when the start of handover preparation is determined to when the handover is actually executed is short, the difference from the standard playback speed can be reduced and playback can be performed at a speed close to the standard speed. . Therefore, handover from the first radio communication network to the second radio communication network can be performed without degrading the reproduction quality and real-time property.
- FIG. 3 is a diagram for explaining a method for calculating a handover preparation time by the handover control unit shown in FIG. 2.
- FIG. 3 is a diagram for explaining an example of an absolute delay time acquisition method by a handover control unit shown in FIG. 2.
- It is a functional block diagram which shows schematic structure of the telephone function part shown in FIG. It is a sequence diagram which shows operation
- FIG. 6 is a diagram for explaining an example of a reception packet reproduction rate control method by the jitter buffer control unit shown in FIG. 5. It is a figure for demonstrating the control method of the jitter buffer by this Embodiment. For comparison with FIG.
- FIG. 10 it is a diagram for explaining a jitter buffer control method in the case where the accumulation upper limit value of the jitter buffer is not changed before the handover schedule is determined. 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 apparatus 12 Partner communication terminal 12a Handset 15 1st wireless communication network 15a Access point 16 2nd 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 54 Radio Status Monitoring Unit 55 Handover Information Acquisition Unit 56 Playback Speed Calculation Unit 60 Core Network 61 Measurement Server 62 First information server 63 Second information server 65 Provider
- 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 VoIP call that is a real-time communication system application with a counterpart communication terminal 12 that is an opposite 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 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
- 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 is registered at the time of handover. To do. 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 device 11 registers the IP address of the first wireless communication network 15 in the HA 23 as a care-of address (first wireless CoA), and the partner communication terminal 12 via the first wireless communication network 15. It is assumed that the handover to the second wireless communication network 16 is performed from the state where communication is performed with the second wireless communication network 16.
- 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.
- a telephone function unit 33 constituting an execution unit, a communication processing unit 34 for controlling connection to the first wireless communication network 15 and the second wireless communication network 16, and the first wireless communication network 15 and the second wireless communication network 16.
- a wireless information acquisition unit 35 that acquires wireless information
- a handover control unit 36 that controls handover between the first wireless communication network 15 and the second wireless communication network 16 are provided.
- the communication processing unit 34 constitutes a wireless communication unit that performs wireless communication. Between the telephone function unit 33 and the counterpart communication terminal 12, the first wireless communication network 15 or the second wireless communication network 16 is used. While making a call, 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 under the control of the handover control unit 36.
- 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, respectively, and the acquired communication quality Is supplied to the handover control unit 36 and the communication quality of the first wireless communication network 15 currently used for a call is supplied to the telephone function unit 33.
- the communication quality for example, RSSI (Received Signal Signal Strength Indicator) indicating a wireless state is acquired.
- the wireless state of the second wireless communication network 16 that is not used for a call is acquired by receiving broadcast information transmitted from the base station 16a, for example. Therefore, the radio information acquisition unit 35 constitutes a communication quality acquisition unit that acquires the communication quality (radio state) of the radio link.
- the handover control unit 36 measures and acquires the absolute delay time Tddn1 of the downlink of the first wireless communication network 15 when connected to the first wireless communication network 15. In addition, during the connection to the first wireless communication network 15, the handover control unit 36 determines whether or not to schedule a handover, that is, whether or not to start preparation for handover.
- the handover control unit 36 monitors the respective radio states (communication quality) of the first radio communication network 15 and the second radio communication network 16 acquired from the radio information acquisition unit 35. As a result, the wireless state of the first wireless communication network 15 that is making a call by forming a wireless link becomes worse than the preset handover schedule determination threshold in the first wireless communication network 15, and the second wireless communication When the wireless state of the network 16 becomes equal to or higher than the handover schedule determination threshold, the handover schedule to the second wireless communication network 16 is determined, that is, the start of handover preparation is determined. Note that the handover control unit 36 supplies the handover function determination threshold in the first wireless communication network 15 currently in use to the telephone function unit 33 when connected to the first wireless communication network 15.
- the handover control unit 36 calculates the handover preparation time T1 until the handover start schedule, and at the same time, the handover destination downlink in the handover destination radio communication network (here, the second radio communication network 16). Measure absolute delay time Tddn2. These pieces of information are supplied to the telephone function unit 33 as necessary handover information together with information on handover schedule determination and the downlink absolute delay time Tddn1 in the first wireless communication network 15 that is already used and has been acquired. 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. 15 and the measurement part which measures each delay time in the 2nd radio
- 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 rate of change ⁇ Rs (t) of the radio unit time ( ⁇ t) in the currently used radio communication network at a predetermined timing according to the following formula, For example, a plurality of change rates ⁇ Rs (t) up to 2 sec) are held in the memory.
- the change rate average value ⁇ Rsrms up to a predetermined time held at that time is calculated.
- 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). 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. 3B 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 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 be synchronized 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 determines a handover schedule
- the handover control unit 36 controls the telephone function unit 33 and / or the communication processing unit 34 to transmit the wireless communication device 11 from 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.
- IEEE 802.21 Media Independent Handover (MIH)
- WiFi Wireless Fidelity
- WiMAX Worldwide Interoperability for Microwave Access
- mobile phones etc.
- MIH Media Independent Handover
- the handover control unit 36 is defined as an MIH user
- MIHF MIH Function
- MIH user acquires wireless information of a communication device based on a request from the MIH user and provides it to the MIH user.
- MIH user acquires information from an information server in a connected network through MIHF in his / her terminal.
- FIG. 4 is a diagram for explaining the fourth absolute delay time acquisition method.
- a first wireless communication network 15 and a second wireless communication network 16 are connected to a backbone network 60 constituting the Internet 18 together with other wireless communication networks, and measurement for measuring delay time in the backbone network 60 is performed.
- Server 61 is directly connected.
- a first information server 62 is connected to the first wireless communication network 15, and a second information server 63 is connected to the second wireless communication network 16.
- the partner communication terminal 12 is connected to the backbone network 60 via the provider 65.
- the first information server 62 uses the one-way network delay reference time Tn1 from the measurement server 61 to the access point 15a as a reference for delay time measurement, and the wireless communication apparatus connected to the access point 15a from the access point 15a.
- the upper and lower radio delay reference times Trup1 and Trdn1 are held.
- the second information server 63 uses a one-way network delay reference time Tn2 from the measurement server 61 to the base station 16a as a reference for delay time measurement, and a radio connected from the base station 16a to the base station 16a.
- the upper and lower radio delay reference times Trup2 and Trdn2 to the communication device are held.
- the network delay reference times Tn1 and Tn2 are transmitted / received between the access point 15a and the measurement server 61, and between the base station 16a and the measurement server 61, respectively (such as PING and RTCP).
- the round trip time is measured, and the round trip time is halved.
- the upper and lower radio delay reference times Trup1 and Trdn1 in the first radio communication network 15 send packets from the access point 15a to the radio communication apparatus connected to the access point 15a and time-synchronized with the access point 15a.
- the wireless communication device that has received the packet records the received time and sends back the packet, thereby calculating each of the uplink and downlink delay times.
- the upper and lower radio delay reference times Trup2 and Trdn2 in the second radio communication network 16 send packets from the base station 16a to the radio communication apparatus connected to the base station 16a and time-synchronized with the base station 16a.
- the wireless communication apparatus that has received the packet records the time of reception and sends back the packet, thereby calculating each of the upstream and downstream delay times.
- the handover control unit 36 When connecting to the first wireless communication network 15, the handover control unit 36 transmits the network delay reference time Tn1 and the wireless delay reference time from the first information server 62 connected to the first wireless communication network 15 via MIHF. Get Trdn1 and Trup1. In addition, the handover control unit 36 transmits / receives a packet to / from the other party (here, the other communication terminal 12 that is not time-synchronized with the wireless communication apparatus 11) for which the delay time is to be measured. The round trip time (Tn3 + Trdn3 + Tn3 + Trup3) is measured.
- the handover control unit 36 obtains a one-way delay time (Tn3-Tn1) between the counterpart communication terminal 12 and the measurement server 61 from this value as follows, and Tn3 + Trdn3 corresponding to the handover source downlink absolute delay time Tddn1 with the communication terminal 12 is calculated.
- Tn3-Tn1 ⁇ (Tn3 + Trdn3 + Tn3 + Trup3)-(Tn1 + Trdn1 + Tn1 + Trup1) ⁇ / 2
- the handover control unit 36 acquires the network delay reference time Tn2 and the radio delay reference time Trdn2 of the handover destination. Therefore, the location information of the wireless communication device 11 is transmitted to the second information server 63 of the second wireless communication network 16 that is the handover destination via the first information server 62 of the first wireless communication network 15 that is currently connected. To request a reply of the network delay reference time Tn2 and the radio delay reference time Trdn2. As a result, the second information server 63 determines the network delay reference time Tn2 and the radio delay reference time Trdn2 of the base station 16a considered to be connected in consideration of the position information and the number of connected users of each base station. 1 It returns to the wireless communication device 11 via the information server 62.
- the handover controller 36 receives the handover destination network delay reference time Tn2 and the radio delay reference time Trdn2 returned from the second information server 63, and uses the obtained information and the calculated (Tn3-Tn1), In the following manner, Tn4 + Trdn4 corresponding to the handover destination downlink absolute delay time Tddn2 between the wireless communication apparatus 11 and the counterpart communication terminal 12 is calculated.
- the handover control unit 36 also requests the second information server 63 to return the wireless delay reference time Trup2, which corresponds to the handover destination uplink absolute delay time Tdup2 between the wireless communication device 11 and the counterpart communication terminal 12.
- the handover controller 36 obtains the downlink absolute delay times Tddn1 and Tddn2 acquired by any one of the first to fourth absolute delay time acquisition methods together with the downlink absolute delay times acquired in the same manner for other wireless communication networks. For each wireless communication network, it is stored in a memory (not shown) in the handover control unit 36 and supplied to the telephone function unit 33.
- the handover control unit 36 performs the downlink absolute delay time of another radio communication network including the information on the handover schedule determination, the handover preparation time T1, the handover source downlink absolute delay time Tddn1, and the handover destination downlink absolute delay time Tddn2. And the information is supplied to the telephone function unit 33.
- 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. Thereafter, when the handover preparation time T1 has elapsed, the handover control unit 36 transmits a Registration Request (Binding Update in NEMO) to the HA 23 via the second wireless communication network 16 that is the handover destination, and the handover destination to the HA 23. Register the care-of address of.
- a Registration Request Biting Update in NEMO
- the handover control unit 36 sets 8 bits of RegistrationRegRequest Field of the Registration Request message to the communication processing unit 34 (in NEMO, MultipleMulticare of address is used), and the second radio communication network 15 also uses the second radio.
- the communication network 16 can also communicate.
- the handover control unit 36 when receiving Registration Reply (Binding Acknowledge in NEMO), which is the handover completion information returned from the HA 23, cancels the registration of the care-of address of the first wireless communication network 15 that is the handover source, and connects Disconnect. 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. 5 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 radio communication apparatus 11 further includes a radio state monitoring unit 54, a handover information acquisition unit 55, and a playback speed calculation unit 56 in addition to the telephone function unit 33.
- the wireless state monitoring unit 54 acquires the wireless state of the first wireless communication network 15 currently in use from the wireless information acquisition unit 35.
- the radio status monitoring unit 54 receives from the handover control unit 36 a radio status handover schedule determination threshold, handover schedule determination / completion information, and an absolute downlink delay of each radio communication network in the first radio communication network 15 currently in use. The time is acquired, and based on the acquired information, a packet storage upper limit value of the jitter buffer 47 is set as will be described later, and supplied to the reproduction speed calculation unit 56.
- the handover information acquisition unit 55 monitors the handover information from the handover control unit 36 at regular intervals, detects whether there is information on handover schedule determination, and if there is information on handover schedule determination, The required handover information is acquired from the handover control unit 36, and the acquired information is supplied to the playback speed calculation unit 56.
- the playback speed calculation unit 56 and the setting value of the storage upper limit value of the jitter buffer 47 input from the radio state monitoring unit 54 and the jitter buffer monitoring unit 50 Based on the monitoring result of the jitter buffer 47, the packet reproduction speed, that is, the application being executed is set so that the accumulated value of the packet in the jitter buffer 47 becomes the above set value via the jitter buffer control unit 51.
- the playback speed (in this embodiment, the playback speed of the VoIP application) is controlled.
- the playback speed calculation unit 56 controls the playback speed of the application being executed based on the handover information acquired from the handover information acquisition unit 55. Determine whether or not.
- the reproduction speed calculation unit 56 calculates the reproduction speed of the received packet based on the acquired handover information and the monitoring result of the jitter buffer 47 by the jitter buffer monitoring unit 50, and the calculation The 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, the storage upper limit value changing unit and the application playback speed control unit of the jitter buffer 47 include the radio state monitoring unit 54, the playback speed calculation unit 56, the jitter buffer monitoring unit 50, and the jitter buffer control unit 51. Is done.
- the wireless state monitoring unit 54 sets the packet accumulation upper limit value of the jitter buffer 47 according to the wireless state from the wireless information acquisition unit 35 in a state where the handover schedule determination information is not input from the handover control unit 36. And supplied to the reproduction speed calculation unit 56.
- the radio state monitoring unit 54 first sets the maximum value kmax for the increase in packet accumulation in the jitter buffer 47 based on the downlink absolute delay time in each radio communication network (total number N) acquired from the handover control unit 36. calculate.
- the maximum value kmax is calculated by the following formula, for example. That is, the result of subtracting the absolute delay time Tddn1 of the first wireless communication network 15 currently in use from each absolute delay time of the wireless communication network that is not currently used is defined as D1, D2, D3,. Among these differences, those that are negative are set to a value of 0, an average value of the differences is obtained, and, for example, 1 ⁇ 2 of the average value is set as the maximum value kmax.
- a plurality of change thresholds for changing the accumulation upper limit value (increase) of the jitter buffer 47 is set according to the radio state of the first radio communication network 15 in use. Therefore, for example, when the absolute delay time of the wireless communication network other than the in-use wireless communication network is shorter than that of the first wireless communication network 15 in use, the increase in the packet accumulation amount is zero.
- the absolute delay time Tddn1 of the first wireless communication network 15 in use is 70 msec
- the absolute delay time of the second wireless communication network 16 measured and stored in the past is 50 msec
- the maximum value of the packet accumulation amount, that is, the maximum value of the accumulation upper limit value is 1.25 times (200 msec) of the standard. Therefore, in this case, as shown in FIG.
- the accumulation upper limit value of the jitter buffer 47 becomes 1.25 times the standard, and the magnification becomes smaller as the radio condition becomes better than that. Then, a change threshold value for each accumulation upper limit value is set. Note that the accumulation upper limit value is set to the standard (magnification 1.0) when the wireless state is in a good state of a predetermined value or more.
- the absolute delay time Tddn1 of the first wireless communication network 15 in use is 70 msec
- the absolute delay time of the second wireless communication network 16 measured and stored in the past is 310 msec
- the maximum value of the accumulation upper limit value is 1.5 times (240 msec) of the standard. Therefore, in this case, as shown in FIG.
- the accumulation upper limit value of the jitter buffer 47 is 1.5 times the standard in the vicinity of the handover schedule determination threshold, and the magnification becomes smaller as the radio state becomes better than that.
- the threshold value for changing each accumulation upper limit value is set so that the value becomes standard (magnification 1.0).
- each change threshold is an increase change threshold applied when the radio state crosses below this value, and “(decrease)”.
- the accumulation upper limit value of the jitter buffer 47 is increased to 1.2 times the standard value, and from there
- the wireless state recovers and exceeds the reduction change threshold of “ ⁇ 1.1 (decrease)” the accumulation upper limit value of the jitter buffer 47 is increased to 1.1 times the standard value.
- the wireless state monitoring unit 54 acquires the wireless state from the wireless information acquisition unit 35 at a predetermined interval, averages the acquired wireless state over a predetermined time range, and the average value changes each accumulation upper limit value. Whether the threshold value is exceeded or below the threshold value is monitored, and when the value exceeds or falls below the change threshold value, the change threshold value is supplied to the reproduction speed calculation unit 56 as the set value of the storage upper limit value.
- the above processing is performed until the handover schedule determination information is acquired from the handover control unit 36.
- the radio state monitoring unit 54 temporarily stops monitoring the radio state. Thereafter, when the wireless state monitoring unit 54 acquires the handover completion information from the handover control unit 36, the handover of the wireless state in the new wireless communication network (in this case, the second wireless communication network 16) of the handover destination is performed from the handover control unit 36.
- the schedule determination threshold value the downlink absolute delay time of each wireless communication network is acquired, and the packet storage upper limit value of the jitter buffer 47 is set and supplied to the reproduction speed calculation unit 56 as described above.
- the playback speed calculation unit 56 monitors the storage upper limit value from the radio state monitoring unit 54 in a state where the handover schedule determination information is not input from the handover information acquisition unit 55. When the accumulation upper limit value is input, the playback speed calculation unit 56 acquires the current packet accumulation amount in the jitter buffer 47 from the jitter buffer monitoring unit 50, and the acquired accumulation amount and the radio state monitoring unit 54. Compare the storage upper limit value set in.
- the reproduction speed calculation unit 56 sets the first reproduction speed Vs (for example, 80% of V1) slower than the standard reproduction speed V1.
- the jitter buffer control unit 51 is instructed to set the reproduction speed V.
- the reproduction speed calculation unit 56 is faster than the standard reproduction speed V1 but is set to the standard reproduction speed V1 rather than the first reproduction speed Vs.
- the jitter buffer control unit 51 is instructed to set the second reproduction speed Vf (for example, a speed of 110% of V1) close to the reproduction speed V.
- the reproduction speed calculation unit 56 acquires the packet accumulation amount in the jitter buffer 47 from the jitter buffer monitoring unit 50, and continues to compare with the accumulation upper limit value set by the wireless state monitoring unit 54.
- the jitter buffer controller 51 is instructed to return V to the standard reproduction speed V1.
- the playback speed calculation unit 56 sets the playback speed V to the standard playback speed V1, the first playback speed Vs slower than the standard, and the second playback speed Vf faster than the standard in a state where no handover is scheduled. From these three playback speeds, one playback speed is appropriately selected based on a comparison between the current packet storage amount in the jitter buffer 47 and the storage upper limit value according to the radio state. Thus, the number of packets in the jitter buffer 47 is controlled. In addition, the change upper threshold value of the jitter buffer 47 is made different depending on the increase and decrease of the radio state.
- the second playback speed Vf that is faster than the standard for controlling the packet accumulation amount is set to a speed closer to the standard playback speed V1 than the first playback speed Vs that is slower than the standard. That is, the speed increase of the fast second playback speed Vf with respect to the standard playback speed V1 is made smaller than the speed decrease of the slow first playback speed Vs. Therefore, as shown in FIGS. 7 and 8, even when the wireless state deteriorates while moving up and down, the packet accumulation amount of the jitter buffer 47 can be increased following the deterioration.
- the playback speed calculation unit 56 calculates the playback speed V based on the handover information from the handover information acquisition unit 55.
- the playback speed calculation unit 56 determines the handover destination based on the acquired required handover information and the monitoring result of the jitter buffer 47 by the jitter buffer monitoring unit 50. From the following equation, the number of packets received in the jitter buffer 47 is determined so that the number of packets in the jitter buffer 47 becomes the number of packets corresponding to the standard reproduction speed V1 when reception of packets from the second wireless communication network 16 starts. Calculate the playback speed V.
- Ta represents a jitter buffer standard delay time corresponding to the standard number of packets in the jitter buffer 47 corresponding to the standard reproduction speed V1
- Tb is the time when the handover schedule determination information is received.
- a delay time corresponding to the number of packets in the jitter buffer 47 is shown.
- V (Tb-Ta + V1 ⁇ T1) / (T1 + T2)
- the reproduction speed calculation unit 56 supplies the calculated reproduction speed V to the jitter buffer control unit 51, and thereby the received packet is reproduced from the jitter buffer 47 so that the received packet is reproduced at a reproduction speed V lower than the standard reproduction speed V 1. Controls reading of received packets.
- the reproduction speed calculation unit 56 acquires the handover completion information from the handover information acquisition unit 55, the reproduction speed calculation unit 56 acquires the packet reception interval time from the jitter buffer monitoring unit 50 at regular intervals, and obtains a predetermined time of the acquired reception interval time.
- the average value of the packet reception interval is calculated, and it is monitored whether or not the difference between the calculated packet reception interval average value and the standard reception interval in the VoIP application falls within a predetermined threshold.
- 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.
- the jitter buffer controller 51 is instructed to immediately return to the normal reproduction speed control. That is, when the playback speed calculation unit 56 determines that a packet from the handover destination has been received, 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.
- the reproduction speed control by the jitter buffer controller 51 is performed as follows, for example.
- 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.
- FIG. 10 is a diagram for explaining a control method of the jitter buffer 47 according to the present embodiment. 10, (a) is the number of packets that the jitter buffer 47 receives per unit time, (b) is the handover-source radio state and the threshold value for changing each storage upper limit value of the jitter buffer 47, and (c) is the jitter.
- the packet reproduction speed (reading interval) from the buffer 47 and (d) indicate the number of packets in the jitter buffer 47, respectively.
- FIG. 11 shows that the reproduction upper limit value of the jitter buffer 47 is not changed before the handover schedule is determined. It is a figure for demonstrating the control method of the jitter buffer 47 which controls V.
- FIG. 11, (a) to (d) are the same as FIGS. 10 (a) to (d), but in this comparative example, the accumulation upper limit value of the jitter buffer 47 is not changed, so FIG. 11 (b) Does not indicate the threshold value for changing the accumulation upper limit value.
- 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.
- the accumulation upper limit value of the jitter buffer 47 is changed based on the wireless state in the first wireless communication network 15 in use before the handover schedule is determined. Then, the playback speed is controlled based on the change of the accumulation upper limit value. Therefore, when the time from when the handover schedule is determined to when the handover is actually executed is short, the difference from the standard reproduction speed is made smaller than in the case of FIG. Can be played. As a result, the influence of jitter on the playback sound due to handover can be reduced, and even if the jitter becomes larger than expected due to the deterioration of the radio condition, the generation of silence can be prevented, so the playback quality and real-time performance are improved. Handover from the first wireless communication network 15 to the second wireless communication network 16 is possible without reduction.
- the present invention is not limited to the above embodiment, and many variations or modifications are possible.
- the present invention is not limited to the case of executing a VoIP application, but can be effectively applied to a case of executing a real-time communication system application such as streaming reproduction 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 cdma2000x1xEV-DO, but other wireless communication networks such as PDC (Personal Digital Cellular), W-CDMA (Wideband CDMA), PHS (Personal Handy-
- PDC Personal Digital Cellular
- W-CDMA Wideband CDMA
- PHS Personal Handy-
- the present invention can be effectively applied to handover between any different wireless communication networks such as phone (System), Bluetooth, WiMAX, LTE (Long Term Evolution), UMB (Ultra Mobile Broadband), and IMT-Advanced.
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、
ジッタバッファおよび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を有し、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、前記ジッタバッファの蓄積上限値を変更する変更部と、
該変更部による前記ジッタバッファの蓄積上限値の変更に基づいて、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、
前記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におけるそれぞれの遅延時間を計測する計測部と、を有し、
前記制御部は、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におけるそれぞれの遅延時間と、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遅くするように制御することを特徴とするものである。
前記制御部は、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における遅延時間と前記第2無線通信ネットワークにおける遅延時間とを比較し、前記第2無線通信ネットワークにおける遅延時間の方が、前記第1無線通信ネットワークにおける遅延時間よりも所定時間以上長い場合に、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、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、当該アプリケーションの標準の再生速度に対応する所定量となるように、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を完了すると、当該アプリケーションの再生速度を標準の再生速度に戻すことを特徴とするものである。
前記変更部は、前記ジッタバッファの蓄積上限値を変更するための複数の異なる変更閾値を有し、前記通信品質取得部からの前記通信品質と前記複数の変更閾値との比較に基づいて、前記通信品質取得部からの前記通信品質が、前記決定部による前記第1無線通信ネットワークのハンドオーバ予定決定閾値に近づくに従って、前記ジッタバッファの蓄積上限値を多くするように変更することを特徴とするものである。
前記制御部は、前記変更部で設定された前記ジッタバッファの蓄積上限値と、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の比較に基づいて、前記データ量が前記蓄積上限値と等しい場合は、当該アプリケーションの再生速度を標準の再生速度とし、前記データ量が前記蓄積上限値よりも少ない場合は、前記標準の再生速度よりも遅い第1再生速度とし、前記データ量が前記蓄積上限値よりも多い場合は、前記標準の再生速度よりも速い第2再生速度とするように、当該アプリケーションの再生速度を制御することを特徴とするものである。
前記第2再生速度の前記標準の再生速度に対する速度増加分を、前記第1再生速度の前記標準の再生速度に対する速度低下分よりも小さくしたことを特徴とするものである。
前記変更部は、前記ジッタバッファの同一の蓄積上限値に対して、前記通信品質取得部からの前記通信品質が下回る場合に適用する増用変更閾値と、前記通信品質取得部からの前記通信品質が上回る場合に適用する、前記増用変更閾値よりも低い減用変更閾値とを有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 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
54 無線状態監視部
55 ハンドオーバ情報取得部
56 再生速度計算部
60 基幹ネットワーク
61 計測用サーバ
62 第1インフォメーションサーバ
63 第2インフォメーションサーバ
65 プロバイダ
ハンドオーバ準備時間T1は、例えば、図3(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|
ハンドオーバ元下り絶対遅延時間Tddn1およびハンドオーバ先下り絶対遅延時間Tddn2は、例えば、以下に説明する第1~第4の絶対遅延時間取得方法のいずれかによって取得する。
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、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すると、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すると、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下りの絶対遅延時間を取得する。IEEE802.21(Media Independent Handover(MIH))では、異種無線通信ネットワーク(WiFi(Wireless Fidelity)、WiMAX(Worldwide Interoperability for Microwave Access)、携帯電話など)間のハンドオーバ技術として、ハンドオーバを制御する手段(図2では、ハンドオーバ制御部36)をMIHユーザと定義し、MIHF(MIH Function)がMIHユーザからの要求に基づいて、通信デバイスの無線情報を取得して、MIHユーザに提供することを考えている。また、MIHユーザが、自らの端末内のMIHFを通して、接続しているネットワーク内のインフォメーションサーバから情報を取得することも考えられている。
Tn3-Tn1={(Tn3+Trdn3+Tn3+Trup3)-(Tn1+Trdn1+Tn1+Trup1)}/2
Tddn1=Tn3+Trdn3=Tn1+Trdn1+(Tn3-Tn1)
Tddn2=Tn4+Trdn4=(Tn2+Trdn2)+(Tn3-Tn1)
kmax=[(D1+D2+D3+...)/(N-1)]/2
V=(Tb-Ta+V1×T1)/(T1+T2)
この場合は、標準の再生速度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、選択あるいは算出された再生速度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、とすると、TR=TR1/V、とする。例えば、標準の再生速度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アプリケーションの場合において、再生速度Vを、上述したように、V1の110%の第2再生速度Vfとする場合は、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=20/1.1(msec)、とする。
この場合は、例えば、以下に説明する第1の再生速度制御方法または第2の再生速度制御方法のいずれかにより実行する。
上述した再生速度Vを標準よりも速くする場合と同様に、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TRを、TR=TR1/V、とする。例えば、上記の場合と同様に、標準の再生速度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アプリケーションの場合において、再生速度Vを標準の再生速度V1の80%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、下式において、TDは、遅延時間で、初期値は0である。
[数6]
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)
Claims (8)
- 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、
ジッタバッファおよび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を有し、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、前記ジッタバッファの蓄積上限値を変更する変更部と、
該変更部による前記ジッタバッファの蓄積上限値の変更に基づいて、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、
前記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におけるそれぞれの遅延時間を計測する計測部と、を有し、
前記制御部は、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におけるそれぞれの遅延時間と、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遅くするように制御することを特徴とする無線通信装置。 - 前記制御部は、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における遅延時間と前記第2無線通信ネットワークにおける遅延時間とを比較し、前記第2無線通信ネットワークにおける遅延時間の方が、前記第1無線通信ネットワークにおける遅延時間よりも所定時間以上長い場合に、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、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、当該アプリケーションの標準の再生速度に対応する所定量となるように、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へのハンドオーバを完了すると、当該アプリケーションの再生速度を標準の再生速度に戻すことを特徴とする請求項3に記載の無線通信装置。
- 前記変更部は、前記ジッタバッファの蓄積上限値を変更するための複数の異なる変更閾値を有し、前記通信品質取得部からの前記通信品質と前記複数の変更閾値との比較に基づいて、前記通信品質取得部からの前記通信品質が、前記決定部による前記第1無線通信ネットワークのハンドオーバ予定決定閾値に近づくに従って、前記ジッタバッファの蓄積上限値を多くするように変更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、前記変更部で設定された前記ジッタバッファの蓄積上限値と、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の比較に基づいて、前記データ量が前記蓄積上限値と等しい場合は、当該アプリケーションの再生速度を標準の再生速度とし、前記データ量が前記蓄積上限値よりも少ない場合は、前記標準の再生速度よりも遅い第1再生速度とし、前記データ量が前記蓄積上限値よりも多い場合は、前記標準の再生速度よりも速い第2再生速度とするように、当該アプリケーションの再生速度を制御することを特徴とする請求項5に記載の無線通信装置。
- 前記第2再生速度の前記標準の再生速度に対する速度増加分を、前記第1再生速度の前記標準の再生速度に対する速度低下分よりも小さくしたことを特徴とする請求項6に記載の無線通信装置。
- 前記変更部は、前記ジッタバッファの同一の蓄積上限値に対して、前記通信品質取得部からの前記通信品質が下回る場合に適用する増用変更閾値と、前記通信品質取得部からの前記通信品質が上回る場合に適用する、前記増用変更閾値よりも低い減用変更閾値とを有することを特徴とする請求項5,6または7に記載の無線通信装置。
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US10117136B2 (en) * | 2015-02-13 | 2018-10-30 | Telefonaktiebolaget L M Ericsson (Publ) | Methods, apparatuses and computer program products for reducing media gap when connecting independent bearer paths |
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