JP5224996B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a radio communication apparatus capable of performing handover between different radio communication networks.

  In recent years, the Internet Engineering Task Force (IETF) has developed an IP mobility technology that enables seamless movement by enabling handover between a plurality of different wireless communication networks such as a mobile phone network and a wireless LAN 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).

  By the way, when an application having real-time properties such as VoIP is executed via a wireless communication network, it is desirable that the arrival interval of packets received by the communication terminal is constant. However, 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 Thus, a packet reception idle time is generated, and the reproduction quality of a real-time application such as VoIP deteriorates.

  For this reason, generally, a jitter buffer is provided in a communication terminal, and received packets are temporarily accumulated in the jitter buffer, and then packets are read out from the jitter buffer and played back at intervals according to the application. That is, a packet reproduction interval shift due to arrival interval shift (jitter) is absorbed to prevent a decrease in reproduction quality such as reproduction sound quality. However, if the packet reception free time is large and there is no packet in the jitter buffer and silence occurs, or if a large number of packets are received in a short time and the packet does not fit in the jitter buffer, etc. The communication terminal needs to control such as changing the reproduction speed, discarding the received packet, or changing the size of the jitter buffer.

  For the above control, when a communication terminal is handed over to a different wireless communication network, for example, the difference in one-way delay time of each wireless communication network such as the downlink absolute delay time of the handover destination and the downlink absolute delay time of the handover source is calculated. It is conceivable to measure and switch the control method according to the difference.

  The communication terminal sends the handover source downlink absolute delay time and the handover destination downlink absolute delay time to, for example, a handover source with respect to a partner terminal and a server (for example, a home agent (HA) in mobile IP) that is time-synchronized with the communication terminal. Measurement can be performed by transmitting measurement packets such as PING and RTCP from both the wireless communication network and the handover destination wireless communication network and receiving the reply. (For example, refer nonpatent literature 1).

“RTP: A Transport Protocol for Real-Time Applications”, RFC 3550, IETF, July 2003

  However, in the conventional method using measurement packets such as PING and RTCP, the communication terminal and the partner terminal (and server) need to be synchronized in time. Since measurement packets such as PING and RTCP are originally intended to measure the round trip delay time with the counterpart terminal, if the communication terminal and the counterpart terminal are not synchronized in time, the communication terminal alone can be used as the handover source. One-way delay times such as downlink absolute delay time and handover destination downlink absolute delay time cannot be measured. In addition, in the wireless section, the delay time differs between upstream and downstream.

  Therefore, an object of the present invention made in view of such a point is to provide a wireless communication apparatus capable of measuring a one-way delay time in a wireless communication network even when the own terminal and the partner terminal are not time synchronized. There is.

The invention of a wireless communication device according to claim 1 that achieves the above object 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;
During wireless communication with the first wireless communication network, a delay time in a wireless section from a server in the first wireless communication network to an access point of the first wireless communication network to a wireless communication device, and the first wireless communication An acquisition unit for acquiring a delay time from a network access point to a predetermined server on the backbone network;
A measuring unit for measuring a round trip delay time to a communication partner via the first wireless communication network;
Based on the delay time of the wireless section acquired by the acquisition unit and the delay time from the access point of the first wireless communication network to a predetermined server on the backbone network, and the round-trip delay time measured by the measurement unit, A calculation unit for calculating a one-way delay time to the communication partner via the first wireless communication network;
It is characterized by comprising.

Further, the acquisition unit includes a delay time in a wireless section from a server in the second wireless communication network to an access point of the second wireless communication network to a wireless communication device, and an access point of the second wireless communication network. A delay time to a predetermined server on the backbone network, and the calculation unit obtains the delay time of the radio section of the second radio communication network and the access point of the second radio communication network acquired by the acquisition unit 1- way delay time to the wireless communication partner via the second wireless communication network is calculated based on the delay time from the wireless communication network to a predetermined server on the backbone network and the round-trip delay time measured by the measurement unit It is desirable.

  The wireless communication apparatus of the present invention calculates the one-way delay time in each wireless communication network based on the delay reference time acquired from the server in the network and the round trip delay time measured in each wireless communication network. It is possible to measure one-way delay times such as the handover source downlink absolute delay time and the handover destination downlink absolute delay time even when the partner terminal and the partner terminal are not time synchronized. Thus, for example, when executing an application having real-time characteristics such as VoIP, when a handover is performed between different wireless communication networks, a voice is transmitted according to the difference between the handover source downlink absolute delay time and the handover destination downlink absolute delay time. By controlling the data reproduction speed, it is possible to prevent the reproduction quality from deteriorating, for example, by preventing the generation of silent intervals.

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

  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. In FIG. 1, it is assumed that 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.

  Here, the first wireless communication network 15 is composed of, for example, a wireless LAN, and the second wireless communication network 16 is composed of, for example, a cdma2000 EV-DO mobile phone network, and the delay time (downward absolute delay in the first wireless communication network 15). (Time) is shorter than the delay time (downlink absolute delay time) in the second wireless communication network 16. In FIG. 1, reference numeral 15 a indicates an access point of the first wireless communication network 15, and reference numeral 16 a indicates an access point (base station) of the second wireless communication network 16. It should be noted that the access point is described as a concept of a terminal device in a wired section including a base station in cellular. Hereinafter, both the base station and the access point are synonymous.

  For example, the partner communication terminal 12 includes a personal computer to which a handset 12a is connected and a softphone is installed, and is connected to the Internet 18 through an Internet service provider (not shown).

  Further, SIP (Session Initiation Protocol) servers 21 and 22 for controlling communication are connected to the packet network 17 and the Internet 18, respectively. Further, a home agent (HA) 23 is connected to the Internet 18 for transferring a received packet addressed to the wireless communication device 11 to a wireless communication network to which the wireless communication device 11 is connected.

  In the communication network shown in FIG. 1, the home address used in the wireless communication network to which the wireless communication device 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. Thus, handover between different wireless communication networks is possible. Note that such IP mobility technology is well known in the above-described mobile IP and NEMO, and thus detailed description thereof is omitted here.

  In the present embodiment, 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 radio 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, and 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. Here, as the communication quality, for example, an RSSI (Received Signal Strength Indicator) representing a radio state is acquired. Note that 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.

  During connection to the first wireless communication network 15, the handover control unit 36 determines whether to schedule a handover, that is, whether to start preparation for handover. For this reason, 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, and forms a radio link. The wireless state of the first wireless communication network 15 that is making a call becomes worse than a preset handover schedule determination threshold in the first wireless communication network 15 and the wireless state of the second wireless communication network 16 is determined to be a handover schedule. When the threshold value is exceeded, the handover schedule to the second wireless communication network 16 is determined, that is, the start of handover preparation is determined. The handover schedule determination threshold in the first wireless communication network 15 currently in use is supplied to the telephone function unit 33 when connecting to the first wireless communication network 15.

  In addition, the handover control unit 36 measures the round-trip delay time with the counterpart communication terminal 12 via the first wireless communication network 15, and from the servers in the first wireless communication network 15 and the second wireless communication network 16. The delay reference time for calculating the one-way delay time with the counterpart communication terminal 12 in each of the first wireless communication network 15 and the second wireless communication network 16 is acquired. When connecting to the first wireless communication network 15, the handover control unit 36 calculates and acquires the downlink absolute delay time Tddn1 of the first wireless communication network 15 based on the measured round trip delay time and the acquired delay reference time. To do. Further, when determining the handover schedule, the handover control unit 36 determines whether the handover destination downlink in the handover destination radio communication network (here, the second radio communication network 16) based on the measured round trip delay time and the acquired delay reference time. The absolute delay time Tddn2 is calculated. 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 the present embodiment, the handover control unit 36 includes the acquisition unit that acquires a predetermined delay reference time from the servers in the first wireless communication network 15 and the second wireless communication network 16, and the first wireless communication network 15. A measuring unit that measures a round trip delay time with the partner communication terminal 12 when the route passes, and a partner in each of the first wireless communication network 15 and the second wireless communication network 16 based on the measured round trip delay time and the acquired delay reference time And a calculation unit that calculates a one-way delay time with the communication terminal 12.

  Next, a method for acquiring the handover source downlink absolute delay time Tddn1 and the handover destination downlink absolute delay time Tddn2 by the handover control unit 36 will be described.

(Acquisition method of absolute delay time Tddn1, Tddn2)
The wireless communication device 11 can measure the round-trip delay time with the counterpart communication terminal 12 through the first wireless network that is the handover source and the second wireless network that is the handover destination, according to the conventional method. However, there are cases where the uplink and downlink of radio section delays may differ greatly, and the handover source downlink absolute delay time Tddn1 and the handover destination downlink absolute delay time Tddn2 can be obtained by simply doubling the round trip delay time. I can't.

  The wireless communication apparatus 11 according to an embodiment of the present invention acquires the handover source downlink absolute delay time Tddn1 and the handover destination downlink absolute delay time Tddn2 by using, for example, a handover technique studied in IEEE 802.21. . In IEEE 802.21 (Media Independent Handover (MIH)), as a handover technique between different types of wireless communication networks (WiFi, WiMAX, mobile phones, etc.), a means for controlling handover (in FIG. 2, the handover control unit 36) is an MIH user. It is considered that MIHF (MIH Function) acquires wireless information of a communication device based on a request from the MIH user and provides it to the MIH user. It is also considered that an MIH user acquires information from an information server in a connected network through MIHF in his / her terminal.

  FIG. 3 is a view for explaining an absolute delay time acquisition method according to an embodiment of the present invention. In FIG. 3, 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. Similarly, 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.

  Here, 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. Note that Tn1 and Tn2 are the delay times of the wired section, and the delay time of the wired section has little difference between the uplink and the downlink, so that half of the round trip time can be used as the one-way delay time.

  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.

  Similarly, 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 received time and sends back the packet, thereby calculating each of the upstream and downstream delay times.

  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. From this value, the one-way delay time (Tn3-Tn1) between the partner communication terminal 12 and the measurement server 61 is obtained as follows, and the handover between the wireless communication device 11 and the partner communication terminal 12 is performed. Tn3 + Trdn3 corresponding to the original downlink absolute delay time Tddn1 is calculated.

[Equation 1]
Tn3-Tn1 = {(Tn3 + Trdn3 + Tn3 + Trup3)-(Tn1 + Trdn1 + Tn1 + Trup1)} / 2
Tddn1 = Tn3 + Trdn3 = Tn1 + Trdn1 + (Tn3-Tn1)

  Tn3 + Trup3 corresponding to the handover source upstream absolute delay time Tdup1 between the wireless communication device 11 and the counterpart communication terminal 12 can be obtained by Tdup1 = Tn3 + Trup3 = Tn1 + Trup1 + (Tn3-Tn1). .

  Further, when the handover control unit 36 determines the handover schedule, the handover control unit 36 acquires the network delay reference time Tn2 and the radio delay reference time Trdn2 of the handover destination, and therefore the first information server of the first wireless communication network 15 currently connected to the handover control unit 36. 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 62, and the network delay reference time Tn2 and the wireless delay reference time Trdn2 are returned. Request. 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. In general, since the measurement server 61 is arranged inside the backbone network 60 or close to the backbone network 60, the delay between the measurement server 61 and the backbone network 60 is a very small value. Can be considered. In this case, (Tn3-Tn1) calculated in Equation 1 can be approximated to the delay time between the backbone network 60 and the counterpart communication terminal 12, and similarly, (Tn4-Tn2) is also the backbone network 60. And a delay time between the communication terminal 12 and the partner communication terminal 12 can be approximated. Therefore, for (Tn4-Tn2) necessary for calculating Tddn2, the value of (Tn3-Tn1) can be used as an approximate value.

[Equation 2]
Tddn2 = Tn4 + Trdn4 = (Tn2 + Trdn2) + (Tn4-Tn2) = (Tn2 + Trdn2) + (Tn3-Tn1)

  Note that 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. Tn4 + Trup4 can be obtained by Tdup2 = Tn4 + Trup4 = (Tn2 + Trup2) + (Tn4-Tn2) = (Tn2 + Trup2) + (Tn3-Tn1).

  The downlink absolute delay times Tddn1 and Tddn2 obtained by the above method are stored in a memory (not shown) in the handover control unit 36 for each radio communication network together with the downlink absolute delay times obtained in the same manner for other radio communication networks. It is stored and supplied to the telephone function unit 33.

  As described above, the handover control unit 36 acquires the downlink absolute delay time of another wireless communication network including the handover schedule determination information, the handover source downlink absolute delay time Tddn1, and the handover destination downlink absolute delay time Tddn2, The information is supplied to the telephone function unit 33.

  Further, when determining the handover schedule, 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, the handover control unit 36 sends a Registration Request (Binding Update in NEMO) to the HA 23 via the second wireless communication network 16 that is the handover destination, and registers the care-of address of the handover destination in the HA 23. To do.

  At that time, the handover control unit 36 sets 8 bits of the Registration Request Field of the Registration Request message in the communication processing unit 34 (in NEMO, multiple care of address is used), and the first radio communication network 15 also uses the second radio. The communication network 16 can also communicate.

  After that, when receiving the Registration Reply (Binding Acknowledge in NEMO), which is the handover completion information returned from the HA 23, the handover control unit 36 cancels the registration of the care-of address of the first wireless communication network 15 that is the handover source, and connects After that, the communication processing unit 34 is controlled to continue the VoIP application via the second wireless communication network 16 that is the handover destination, and the received handover completion information is supplied to the telephone function unit 33.

  The telephone function unit 33 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, Necessary handover information is acquired from the handover control unit 36. For example, the telephone function unit 33 calculates the playback speed of the received packet based on the acquired handover information and the state of the jitter buffer in the own terminal, and the application function is set so that a silent period does not occur in the voice due to the handover. Playback speed can be controlled.

  As described above, according to the present embodiment, the wireless communication device 11 transmits the delay time of the wireless section of the first wireless communication network and the first wireless communication from the first information server 62 in the first wireless communication network 15. The delay time from the access point 15a of the network 15 to the measurement server 61 on the backbone network 60 is acquired, and the round-trip delay time to the communication partner 12 via the first wireless communication network 15 is measured, and the acquired wireless Based on the section delay time, the delay time to the measurement server 61, and the measured round-trip delay time, the one-way delay time to the partner communication terminal 12 via the first wireless communication network 15 can be calculated. Further, the wireless communication device 11 transmits the delay time of the wireless section of the second wireless communication network 16 and the access point 16a of the second wireless communication network 16 from the second information server 63 in the second wireless communication network 16. The delay time to the measurement server 61 on the backbone network 60 is acquired, and based on the acquired delay time of the wireless section of the second wireless communication network 16 and the delay time to the measurement server 61 and the measured round-trip delay time. Thus, the one-way delay time to the partner communication terminal 12 via the second wireless communication network 16 can be calculated. Thereby, for example, when executing a real-time application such as VoIP, when the wireless communication device 11 performs handover between different wireless communication networks, the handover source downlink absolute delay time and the handover destination downlink absolute delay time are By controlling the reproduction speed of the audio data according to the difference, it is possible to prevent the reproduction quality from deteriorating, for example, by preventing the generation of a silent section.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, 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. Further, the first information server 62 and the second information server 63 may be installed as a common information server on the backbone network 60 without providing them separately. For example, the measurement server 61 can also have the function of the common information server.

It is a figure which shows schematic structure of the communication network which can use the radio | wireless communication apparatus which concerns on one embodiment of this invention. It is a block diagram which shows schematic structure of the radio | wireless communication apparatus shown in FIG. 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.

Explanation of symbols

11 wireless communication device 12 partner communication terminal 12a handset 15 first wireless communication network 15a access point 16 second wireless communication network 16a access point (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

Claims (2)

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;
During wireless communication with the first wireless communication network, a delay time in a wireless section from a server in the first wireless communication network to an access point of the first wireless communication network to a wireless communication device, and the first wireless communication An acquisition unit for acquiring a delay time from a network access point to a predetermined server on the backbone network;
A measuring unit for measuring a round trip delay time to a communication partner via the first wireless communication network;
Based on the delay time of the wireless section acquired by the acquisition unit and the delay time from the access point of the first wireless communication network to a predetermined server on the backbone network, and the round-trip delay time measured by the measurement unit, A calculation unit for calculating a one-way delay time to the communication partner via the first wireless communication network;
A wireless communication device comprising: The acquisition unit includes a delay time in a wireless section from a server in the second wireless communication network to an access point of the second wireless communication network to a wireless communication device, and the access point of the second wireless communication network to the backbone network. And a delay time to the predetermined server on
The calculation unit includes a delay time of a radio section of the second wireless communication network acquired by the acquisition unit, a delay time from an access point of the second wireless communication network to a predetermined server on a backbone network, and the measurement unit 2. The wireless communication apparatus according to claim 1, wherein a one-way delay time to the wireless communication partner via the second wireless communication network is calculated based on the round-trip delay time measured by.

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