JP7148199B2 - Communication device, communication method and program - Google Patents

Description

The present invention relates to a communication device, communication method and program.

In the future, POI (Point Of Interface) will be IP (Internet Protocol). In an IP network, it is ideal to be able to correct end-to-end jitter, and it is expected that the amount of jitter in packets transmitted and received at network boundaries is kept within an allowable range in connection between the networks of operators.

Patent Document 1 discloses a technique of counting the number of packets accumulated in a jitter buffer and deleting the packets accumulated in the jitter buffer if the count value is greater than a predetermined reference value.

In Patent Document 2, a router constituting a group of routers is provided with a jitter buffer for accumulating voice packets transmitted over a communication network, and the router converts the voice packets accumulated in the jitter buffer of the router into a reference clock signal. Discloses a technique for outputting in synchronization with .

Patent Document 3 discloses that in the case of communication using a mobile network, transmission by Delay Packing may be performed depending on the specifications of the base station (eNodeB) (for example, see FIG. 7 of Patent Document 3). ).

Patent Document 3 describes an operation in which a plurality of packets are transmitted in bursts. Normally, when a plurality of packets are not transmitted in a burst, packets are transmitted and received as shown in FIG. On the other hand, when a plurality of packets are transmitted in a burst, packets are transmitted and received as shown in FIGS. 22 and 23. FIG. FIG. 22 shows an example of transmission/reception of a 2-packet burst, and FIG. 23 shows an example of transmission/reception of a 3-packet burst.

JP 2011-101342 A Japanese Patent Application Laid-Open No. 2001-345840 JP 2013-046256 A

In addition, each disclosure of the above prior art documents is incorporated into this document by reference. The following analysis was made by the inventors.

In recent years, research and development of NFV (Network Function Virtualization), which is a technique for virtualizing network functions (communication devices), has been actively promoted. With the NFV, network nodes of communication carriers used to be provided by dedicated devices, but there are increasing needs to implement them on virtualized general-purpose servers.

Suppression of jitter is also required in a network to which NFV is applied. However, with existing measures using jitter buffers, if the reception speed is slower than the dequeue speed due to clock skew, the delay will gradually increase until the packet is deleted, and the problem that packet deletion leads to voice degradation. be.

In the jitter measure (measure using a jitter buffer) disclosed in Patent Document 1, when the reception speed is slower than the dequeue speed due to clock skew (clock deviation), the delay gradually increases until the packet is deleted, and the packet is deleted. However, there is a problem that leads to voice deterioration.

It should be noted that the clock skew is, for example, a difference in precision of a clock signal unique to a device (oscillator) in the apparatus expressed in units of parts per million (ppm). For example, the above problem when the clock accuracy is assumed to be ±100 ppm will be described.

If the clock accuracy of the transmitter is +100 ppm and the clock accuracy of the receiver is −100 ppm, then the clock of the receiver advances 200 ppm faster than the clock of the transmitter. Therefore, when the receiver transmits packets at intervals according to the RTP (Real time Transport Protocol) time stamp value added to the received packet, the data stored in the jitter buffer in the receiver is gradually exhausted.

On the other hand, if the clock accuracy of the transmitter is −100 ppm and the clock accuracy of the receiver is +100 ppm, the clock of the receiver will be 200 ppm slower than the clock of the transmitter. When the receiving device transmits packets at time intervals according to the RTP time stamp value added to the received packets, data stays in the jitter buffer within the receiving device.

It is conceivable to use the technology disclosed in Patent Document 2 in a network to which NFV is applied. However, in order to realize jitter correction at the network boundary with NFV, external synchronization using dedicated hardware performed in the POI network as disclosed in Patent Document 2 cannot be used. In other words, the method disclosed in Patent Document 2 is a configuration that requires an external clock, and requires dedicated hardware. Therefore, the technique disclosed in Patent Document 2 cannot be used in a network to which NFV is applied.

In this way, in order to realize the jitter countermeasure according to Patent Document 2 in NFV, it is not possible to use the external synchronization using dedicated hardware, which was performed in the existing POI network. Jitter countermeasures that can be realized by

A main object of the present invention is to provide a communication device, a communication method, and a program that contribute to preventing data delay inside a jitter buffer due to clock skew between devices.

According to a first aspect of the present invention or disclosure, a receiving unit that receives packets from a counterpart device, a buffer control unit that controls writing and reading of received packets to and from a buffer, and a transmission unit that transmits a received packet to a transfer destination device; and a clock deviation reflection value that reflects the clock deviation between the remote device and the own device based on the reception time of the received packet and the time stamp included in the received packet. an estimating unit for estimating, wherein the buffer control unit determines a time to retrieve the received packet from the buffer using the clock shift reflection value.

According to a second aspect of the present invention or disclosure, a receiving unit that receives a packet from a counterpart device, a buffer in which the received packet is written, and a received packet read from the buffer is transmitted to a transfer destination device. estimating a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device, based on the reception time of the received packet and the time stamp included in the received packet, in the communication device comprising a transmission unit; and determining when to retrieve the received packet from the buffer using the clock skew reflective value.

According to a third aspect of the present invention or disclosure, a receiving unit that receives a packet from a counterpart device, a buffer in which the received packet is written, and a received packet read from the buffer are transmitted to a transfer destination device. A clock deviation reflection value reflecting the clock deviation between the opposing device and the own device based on the reception time of the received packet and the time stamp included in the received packet, in a computer installed in a communication device comprising a transmission unit. and determining the time to retrieve the received packet from the buffer using the clock deviation reflection value.
This program can be recorded in a computer-readable storage medium. The storage medium can be non-transient such as semiconductor memory, hard disk, magnetic recording medium, optical recording medium, and the like. The invention can also be embodied as a computer program product.

According to each aspect of the present invention and disclosure, there are provided a communication device, a communication method, and a program that contribute to preventing data delay inside jitter buffers due to clock skew between devices.

1 is a diagram for explaining an overview of an embodiment; FIG. 1 is a diagram illustrating an example of a schematic configuration of a communication system according to a first embodiment; FIG. FIG. 4 is a diagram for explaining the operation of the TrGW according to the first embodiment; FIG. FIG. 4 is a diagram for explaining the operation of the TrGW according to the first embodiment; FIG. FIG. 4 is a diagram showing an example of the operation of TrGW according to the first embodiment; FIG. 4 is a diagram for explaining advance or delay of packets; FIG. 10 is a diagram for explaining the operation of determining the last packet of burst packets by the TrGW; FIG. 4 is a diagram showing an example of connection information managed by a connection management unit; 4 is a flow chart showing an example of the operation of a receiver; 6 is a flowchart showing an example of reception processing of a reception unit; 4 is a flow chart showing an example of the operation of an enqueue unit; 8 is a flowchart illustrating an example of enqueue processing by an enqueue unit; 4 is a flow chart showing an example of the operation of a dequeue unit; 4 is a flow chart showing an example of the operation of a transmission unit; 6 is a flow chart showing an example of the operation of an estimating unit; 7 is a flowchart showing an example of DP (Delay Packing) determination operation by an estimating unit; 9 is a flow chart showing an example of an operation of calculating an inclination a1 and an adjustment amount by an estimating unit; 3 is a diagram illustrating an example of a hardware configuration of a TrGW according to the first embodiment; FIG. FIG. 4 is a diagram for explaining control of TrGW according to the first embodiment; FIG. 10 is a flowchart showing an example of TS calculation processing for telephone-event correspondence; FIG. FIG. 4 is a diagram for explaining transmission and reception of normal packets; FIG. 4 is a diagram showing an example of transmission and reception of a two-packet burst; FIG. 4 is a diagram showing an example of transmission and reception of a 3-packet burst;

First, an overview of one embodiment will be described. It should be noted that the drawing reference numerals added to this outline are added to each element for convenience as an example to aid understanding, and the description of this outline does not intend any limitation. Also, connecting lines between blocks in each figure include both bi-directional and uni-directional. The unidirectional arrows schematically show the flow of main signals (data) and do not exclude bidirectionality. Furthermore, in the circuit diagrams, block diagrams, internal configuration diagrams, connection diagrams, etc. disclosed in the present application, an input port and an output port exist at the input end and the output end of each connection line, respectively, although not explicitly shown. Input/output interfaces are similar.

A communication device 100 according to an embodiment includes a receiver 101, a buffer controller 102, a transmitter 103, and an estimator 104 (see FIG. 1). A receiving unit 101 receives a packet from a counterpart device. The buffer control unit 102 controls writing and reading of received packets to and from the buffer. The transmission unit 103 transmits the received packet read from the buffer to the transfer destination device. The estimating unit 104 estimates a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device based on the reception time of the received packet and the time stamp included in the received packet. The buffer control unit 102 determines the time to extract the received packet from the buffer using the clock shift reflection value.

The communication device 100 estimates a clock deviation reflected value reflecting the clock deviation between the opposing device and the own device based on the packet reception time and the time stamp included in the packet. The TrGW 10 realizes jitter correction at an interval close to the transmission interval of the opposite device by using the value reflecting this clock shift for buffer control.

Specific embodiments will be described in more detail below with reference to the drawings. In addition, the same code|symbol is attached|subjected to the same component in each embodiment, and the description is abbreviate|omitted.

[First embodiment]
The first embodiment will be described in more detail with reference to the drawings.

FIG. 2 is a diagram illustrating an example of a schematic configuration of a communication system according to the first embodiment; Referring to FIG. 2, the communication system includes TrGW (Translation Gateway) 10 and IBCF (Interconnect Border Control Function) 20 .

The communication system shown in FIG. 2 provides services related to IP telephony. In FIG. 2, services related to IP telephony are provided to terminals 30-1 and 30-2 belonging to different networks.

TrGW 10 and IBCF 20 provide connections between different networks. The IBCF 20 provides a signaling function, and the TrGW 10 performs NAPT (Network Address Port Translation) conversion and the like to provide an inter-network connection function.

When the terminals 30 - 1 and 30 - 2 communicate with each other, a call session control function (CSCF) sends a SIP (Session Initiation Protocol) message to the IBCF 20 . TrGW 10 and IBCF 20 communicate with each other through an interface defined by MEGACO (Media Gateway Control Protocol) to establish a session between terminal 30-1 and terminal 30-2.

In the first embodiment, the TrGW 10, which is an inter-network gateway, receives an RTP packet from the terminal 30-1 and transfers the received packet to the terminal 30-2.

In IP telephony, voice signals are sampled at a predetermined cycle (eg, 8 kHz), and a plurality of sampling results are collected into one packet and transmitted at predetermined intervals (eg, 20 ms). The TrGW 10 receives RTP packets transmitted from the terminal 30-1 at predetermined intervals, and transfers the RTP packets received at the predetermined intervals to the terminal 30-2, which is the transfer destination device of the terminal 30-1. At this time, the TrGW 10 absorbs jitter in the RTP packets transmitted from the terminal 30-1, which is the opposite device, and controls so that the RTP packets are transmitted to the terminal 30-2 at predetermined intervals (FIG. 3). reference).

At this time, the TrGW 10 controls packet transfer so that the internal jitter buffer does not delay due to the clock skew between the terminal 30-1, which is the opposite device, and its own device. More specifically, the TrGW 10 brings the dequeue speed of the jitter buffer close to the RTP packets transmitted from the terminal 30-1, which is the opposite device, and the RTP packets stay in the jitter buffer at the timing after the lapse of a predetermined period of time. adjust the time. That is, the TrGW 10 makes the time (dequeue rate) from storing a packet in the jitter buffer to reading it out closer to the RTP packet transmission interval of the terminal 30-1, which is the opposite device, so that the RTP packets stay in the jitter buffer. control the time.

The TrGW 10 uses a high-resolution clock such as a Time Stamp Counter (hereinafter referred to as TSC), which is a counter that is accumulated for each operation clock of a general-purpose CPU (Central Processing Unit) when receiving an RTP packet, to calculate the packet reception time. (hereinafter referred to as RT value) is measured. That is, the TrGW 10 measures the reception time (RT value) of the RTP packet with the precision of a high-resolution clock (for example, 4 GHz) incorporated in the own device.

Based on the packet reception time RT and the time stamp included in the packet, the TrGW 10 estimates a clock deviation reflected value that reflects the clock deviation between the opposite device and the own device. Specifically, the TrGW 10 calculates the slope of the regression line between the measured packet reception time RT and the RTP time stamp value (hereinafter referred to as TS value) as the clock shift reflection value. The TrGW 10 controls the dequeue time using the calculated slope (clock shift reflection value). Specifically, the TrGW 10 sets the interval at which data packets are enqueued to and dequeued from the jitter buffer to “the difference in the number of cycles from the previous packet x the slope”, so that the interval is close to the transmission interval of the terminal 30-1. jitter correction.

For example, if the RTP time stamp value (TS value) and packet reception time (RT value) are set on the X axis and the Y axis respectively, a straight line as shown in FIG. 4 is obtained. The slope of the straight line is obtained by calculating RT2-RT1)/(TS2-TS1). The TrGW 10 obtains the slope and calculates "difference in number of cycles from previous packet x slope". If the timing for calculation is TS2 in FIG. 4, the difference in the number of cycles from the previous packet is the number of clocks corresponding to (TS2-TS1). -RT1) A corresponding number of clocks can be obtained. The TrGW 10 uses this number of clocks (RT2-RT1) as the jitter buffer dequeue time.

In this way, the TrGW 10 generates the first received packet based on the time obtained by multiplying the difference between the corresponding time stamps of the first received packet and the second received packet received immediately before by the slope of the regression line. is read from the jitter buffer.

Also, the TrGW 10 determines reception of Delay Packing in a situation where Delay Packing can be received. The TrGW 10 accurately estimates the packet transmission interval of the terminal 30-1 by not using the packets delayed due to the delay packing for estimating the slope based on the determination result. That is, when a plurality of packets are burst-received, the TrGW 10 does not use packets other than the last received packet among the plurality of burst-received packets for calculating the slope of the regression line. The TrGW 10 does not include delayed data in the sample data for estimating the slope of the regression line in an environment where burst reception such as Delay Packing is performed. Jitter correction at an interval close to .

First, a theoretical explanation for realizing the control of the TrGW 10 will be given.

<Adjustment of dequeue speed and delay time in TrGW10>
A mechanism will be described in which the dequeue speed of the TrGW 10 is adjusted to match the transmission speed (transmission interval) of the terminal 30-1, which is the opposite device, and the delay inside the TrGW 10 is adjusted to operate with the jitter buffer depth set value. The buffer depth set value is a TSC counter value corresponding to the internal delay time for absorbing fluctuations. Assuming that the packetization period is 20 ms, the TSC counter value corresponding to 20 ms is set as the buffer depth setting value. Furthermore, assuming an environment in which burst transmission of 3 packets is performed, a TSC counter value corresponding to 60 ms (20×3 ms) is set as the buffer depth setting value.

As described above, since the packet transmission interval by the TrGW 10 is proportional to the TS value difference, the slope (coefficient) of the straight line obtained from the TS value and the RT value is derived, and the coefficient (clock If it is multiplied by the difference reflection value), packets can be transferred at the same transmission interval as the terminal 30-1.

The relationship between the reception time RT of the RTP packet and the TS value assigned to the received RTP packet is expressed by the following formula (1) for each RTP session. Here, assuming that the fluctuations are not greatly biased, the slope of the regression line can be estimated by least-squares estimation. Alternatively, it can be estimated by the slope between two samples as shown in Equation (2) below.

[Formula 1]
RT(k)=a1×TS(k)+a0+fluctuation

In equation (1), RT(k) is the k-th packet reception time, TS(k) is the TS value assigned to the k-th packet, and a1 is the TS value 1 transmitted by terminal 30-1, which is the opposite terminal. This is the time in the own device after the clock has elapsed (for one clock of the TS value). Also, a0 is a fixed component derived from an initial value such as an average delay time or a randomly assigned TS value.

[Formula 2]
a1={RT(ne)−RT(nb)}/{TS(ne)−TS(nb)}

In equation (2), ne is the sample number after a certain period of time has elapsed, and nb is the reference sample number. Here, the sample number is a serial number of packets in which "1" is set to the first received packet, which is unique within the session and is equivalent to the RTP sequence number.

Note that the time stamp described (included) in the RTP packet is a value given by the terminal 30-1, which is the opposite device. On the other hand, the reception time of the received RTP packet is a value given by TrGW10. The slope (slope) a1 of the above equation (1) or (2), which is calculated from the times given by the two different devices in this way, is a value that reflects the clock shift of the two devices.

Hereinafter, the estimation result is obtained for each fixed period, and the estimation result for each period is denoted by a1(g). Note that g included in the estimation result indicates the number of generations, and g=0 indicates a value before estimation. a1(0) is an initial value and indicates a rate converted to the number of clocks of TrGW10 (high-resolution clock, TSC).

Note that the TrGW 10 overwrites the estimation result a1(g) with the initial value a1(0) when the estimation result a1(g) is significantly different from the initial value a1(0). Specifically, the TrGW 10 adopts the estimation result a1(g) when the estimation condition represented by the following formula (3) is satisfied.

[Formula 3]
|a1(g)-a1(0)|/a1(0)<α

In equation (3), α is the clock error range (for example, 0.1%) that is considered normal.

The TrGW 10 sets the scheduled dequeue time for each packet data when enqueuing in the internal jitter buffer. Regarding the packet data enqueued in the jitter buffer, the TrGW 10 dequeues the packet from the jitter buffer and transmits it to the outside when the scheduled dequeue time is reached.

The TrGW 10 reproduces the transmission interval between packets by dequeuing after a time corresponding to the codec-specific sampling frequency represented by the TS value difference obtained using the immediately preceding dequeued packet. Since there are individual differences in the device clocks installed in the TrGW 10 and the terminal 30-1, there is an error at first, and the TrGW 10 cannot accurately reproduce the packet transmission interval of the terminal 30-1.

However, the TrGW 10 uses the received information of the RTP packets to derive the least-squares estimation of Equation (1) or the slope of the straight line using Equation (2), and the packet transmission rate of the terminal 30-1 obtained from the slope ( transmission interval) is reflected in the dequeue interval of the jitter buffer. As a result, jitter correction is realized at intervals close to the transmission intervals of the terminal 30-1.

Next, the scheduled dequeue time and the transmission interval by the TrGW 10 will be described.

Immediately after the two devices start communication (g=0), the TrGW 10 cannot derive the transmission rate (transmission interval) of the terminal 30-1, which is the opposite device. Therefore, the TrGW 10 determines the dequeue interval of the jitter buffer by counting the time corresponding to the TS value difference with its own clock.

The TrGW 10 sets the scheduled dequeue time DQT according to the following equation (4).

[Formula 4]
First received packet: DQT(1)=RT(1)+jitter buffer depth set value Second packet and after:
Update cycle packet: DQT (nu (g)) = {TS (k) - TS (k-1)} x a1 (g) + DQT (k-1) + adjustment amount (g)
After non-update cycle packet: DQT(k)={TS(k)-TS(k-1)}×a1(g)+DQT(k-1)

In equation (4), nu(g) is the initial sample number for which the estimation result a1(g) is used for calculating the scheduled dequeue time. The initial value of nu(g) is 1 (nu(0)=1).

According to formula (4), when receiving the first packet, the TrGW 10 delays the jitter buffer depth setting value (for example, 20 ms) from the time (RT(1)) at which the first packet was received, and sends the received packet to the transfer destination device. Forward.

Except when receiving the first packet, the TrGW 10 delays the packet by the delay time determined by the slope a1 calculated from the equations (1) and (2) and the adjustment amount (g), and transfers the packet to the transfer destination device.

Note that the adjustment amount (g) is a value for canceling the time difference (advance of time, delay of time) between the two devices accumulated due to clock skew of the device. Adjusting the advance for each RTP packet reception causes fluctuations, so the TrGW 10 determines the adjustment amount (g) only when updating the number of generations.

In addition, in equation (4), a packet to be dequeued immediately after generation update during enqueue processing is referred to as "update cycle packet", and other packets are referred to as "non-update cycle packet".

According to equation (4), at the beginning of communication, the first RTP packet is transmitted to the transfer destination after the jitter buffer depth setting value (eg, 20 ms) has elapsed from the time RT (1) when the TrGW 10 first received the RTP packet. . After that, the TrGW 10 calculates the slope a1 calculated from the packet reception times of the two RTP packets and the time stamp values TS described in the two packets. The TrGW 10 multiplies the calculated a1 by the difference between the time stamp values described in the two packets, thereby grasping the packet transfer interval of the terminal 30-1, which is the opposite device. The TrGW 10 reflects the obtained packet transfer interval in the previous dequeue scheduled time DQT(k-1), and realizes the same packet transfer interval as that of the opposite device.

Next, updating of the estimation result of the slope a1 to the dequeue scheduled time calculation will be described.

The TrGW 10 calculates, at the timing of calculating the gradient a1 by the equation (1) or (2), the average value of the delay from the immediately preceding calculation of the gradient a1 to the above timing according to the following equation (5). That is, the TrGW 10 calculates the average value of the period during which packets are stored in the jitter buffer 202 in a predetermined period for each generation.

[Formula 5]

In Equation (5), nb(g) is the initial sample number of data used to estimate the estimation result a1(g). Also, nb(0)=1. In Equation (5), ne(g) is the final sample number of data used to estimate a1(g), and Na is the number of samples to be calculated. Note that, in Expression (5), some packets of Delay Packing are excluded from the calculation of the average value.

Further, when |jitter buffer depth−average delay| ) is initialized (set to 0). That is, the TrGW 10 updates the adjustment amount according to the following formula (6).

[Formula 6]
|jitter buffer depth−average delay|>β; adjustment amount (g+1)=−average delay (g)
|jitter buffer depth−average delay|≦β; adjustment amount (g+1)=0

Note that in equation (6), β is a threshold. For example, if the packetization cycle is 20 ms, β should be about 5 ms. Thus, the TrGW 10 calculates the adjustment value based on the average value (average delay) calculated by Equation (5).

An outline of the operation of the TrGW 10 is shown in FIG. As shown in FIG. 5, the TrGW 10 absorbs fluctuations (jitters) of RTP packets transmitted from the opposite device for each session using a jitter buffer. At this time, the TrGW 10 estimates the transmission rate (transmission interval) of the opposite device and reflects the estimated value in controlling the jitter buffer. As a result, the TrGW 10 can transfer packets to the transfer destination device at the same transmission interval as the counterpart device.

<Outlier determination in a specific packet reception case>
As described above, a plurality of packets may be transmitted in bursts depending on the specifications of the base station (see FIGS. 22 and 23).

When the TrGW 10 receives packets at packet intervals as shown in FIG. 22 and FIG. 23, the fluctuation is large and may affect the slope estimation by linear regression shown in Equation (1). Therefore, the TrGW 10 uses the last packet in the unit of burst reception in which the delay at the base station is not large to estimate the slope a1.

The TrGW 10 checks the reception interval between the packet received immediately before and the received packet. The TrGW 10 checks the reception interval using the following formula (7).

[Formula 7]
DEL(k)={RT(k)−RT(k−1)}−{TS(k)−TS(k−1)}×a1(g)

In equation (7), if the value of the reception interval DEL(k) is a negative value, the reception interval is shorter than expected; if it is 0, the reception interval matches the assumption; Indicates longer than expected. The TrGW 10 performs threshold processing on the reception interval and determines by how many packetization cycles the packet is advanced or delayed (see FIG. 6).

The TrGW 10 calculates E1(k) by how many cycles the received packet is advanced or delayed in terms of the packetization cycle. Note that E1(k) and E2(k) and E3(k), which will be described later, are integer values. For example, when the packetization period is 20 ms and the reception interval is 40 ms, E1(k) is 2 because it is advanced by two packetization periods.

The TrGW 10 also uses the calculated E1(k) to calculate E2(k) and E3(k) according to the following equation (8).

[Formula 8]
E1(k)=E1(k)
E2(k)=E1(k)+E1(k-1)
E3(k)=E2(k)+E1(k-2)

When calculating E1(k) to E3(k), TrGW 10 ends the calculation if any value is "0".

In normal packet transmission/reception as shown in FIG. 21, E1 becomes "0" because no significant delay or advance occurs. When burst reception is performed every two packets as shown in FIG. 22, E2 becomes "0" because reception returns to normal timing every two packets. When burst reception is performed every three packets as shown in FIG. 23, E3 becomes "0" because reception returns to normal timing every three packets.

TrGW 10 uses the values of E1-E3 to determine the last packet of burst packets. Specifically, the TrGW 10 determines the last packet of the burst packets using the relationship shown in FIG. For example, referring to FIG. 7, if the calculation results of E1 to E3 are "-1", "-2", and "0", respectively, the TrGW 10 indicates burst reception every 3 packets; th packet is the final packet. That is, the TrGW 10 can use the combination of the above three variables to determine whether periodic burst reception of three packets such as Delay Packing occurs and the last packet of the burst packets.

Equation (8) can be expanded as Ei(k)=E(i-1)(k)+E1(k-i+1). In equation (8), three variables i = 1 to 3 are used to determine whether or not periodic burst reception of packets occurs. However, by increasing the number of variables, it is possible to determine burst transmission/reception with more packets. .

[Device configuration]
Referring to FIG. 2, the TrGW 10 according to the first embodiment includes a receiver 201, a jitter buffer 202, a buffer controller 203, a transmitter 204, an estimator 205, a TSC 206, and a connection manager. 207. Further, the buffer control unit 203 includes an enqueue unit 211 , a dequeue unit 212 , and storage means for storing a dequeue schedule time list 213 .

The receiving unit 201 is means for receiving a packet from the terminal 30-1, which is the opposite device. The receiving unit 201 records the TSC counter value when the RTP packet is received, and stores the packet matching the session information in the reception buffer.

The jitter buffer 202 is a buffer for temporarily storing received packets (packet data) in order to absorb fluctuations.

The buffer control unit 203 is means for controlling writing and reading of received packets to and from the jitter buffer 202 . The buffer control unit 203 reads the data stored in the reception buffer and stores it in the jitter buffer 202 (enqueue processing by the enqueue unit 211). The buffer control unit 203 writes data that has reached the dequeue scheduled time out of the data in the jitter buffer 202 into the transmission buffer (dequeue processing by the dequeue unit 212). At this time, the buffer control unit 203 determines the time (scheduled dequeue time) for extracting the received packet from the jitter buffer 202 using the clock shift reflection value. In addition, the buffer control unit 203 transfers data to the estimation unit 205 (copies the data) at the time of enqueue.

The scheduled dequeue time list 213 is a list in which scheduled dequeue times and jitter buffer storage destinations of packet data are recorded for each session ID.

The transmission unit 204 is means for transmitting the received packet read from the jitter buffer 202 to the terminal 30-2, which is the transfer destination device. The transmission unit 204 has an internal transmission buffer, and packetizes and transmits the data stored in the transmission buffer.

Based on the dequeued packet information, the estimation unit 205 calculates the slope a1 that determines the transmission interval (transmission rate) of the opposite terminal and the delay adjustment amount, and notifies the buffer control unit 203 of the calculation result.

The buffer control unit 203 calculates the scheduled dequeue time based on the obtained calculation result (slope a1, delay adjustment amount), and stores it in the scheduled dequeue time list.

The TSC unit 206 is a high-resolution TSC (Time Stamp Counter) counter that is incremented by 1 every CPU cycle after the CPU mounted on the TrGW 10 is activated. The counter value obtained by the TSC unit 206 is used to measure the packet reception time in the reception unit 201 and to confirm the transmission time by the dequeue processing of the buffer control unit 203 . Note that the clock that implements the TSC unit 206 has a higher frequency (resolution) and accuracy than at least the clocks used for the operations of the receiver 201 and transmitter 204 and the clocks used for packet transmission/reception by the opposite device.

The connection management unit 207 manages connection information in which transmission source session information and transfer destination session information are recorded. FIG. 8 is a diagram showing an example of connection information managed by the connection management unit 207. As shown in FIG. The connection management unit 207 generates and manages connection information as shown in FIG. 8 using information acquired from the IBCF 20 or the like.

[Explanation of operation]
Next, the operation of the TrGW 10 according to the first embodiment will be described with reference to the drawings.

FIG. 9 is a flow chart showing an example of the operation of the receiving unit 201. As shown in FIG.

Upon receiving a packet (step S01), the receiving unit 201 executes a reception process (step S02).

FIG. 10 is a flow chart showing an example of reception processing (step S02 in FIG. 9) of the reception unit 201. As shown in FIG.

The receiving unit 201 refers to the TSC counter value (step S101).

The receiving unit 201 checks whether the connection management information includes connection information that matches the received packet (step S102).

If matching information is included in the connection management information (step S102, Yes branch), the reception unit 201 stores the connection ID, TSC counter value, and packet data in the reception buffer (step S103).

If matching information is not included in the connection management information (step S102, No branch), the receiving unit 201 discards the received packet (packet data) (step S104).

FIG. 11 is a flow chart showing an example of the operation of the enqueue unit 211 included in the buffer control unit 203. As shown in FIG.

The enqueuing unit 211 refers to the reception buffer (step S11) and checks whether or not unprocessed data exists (step S12).

If unprocessed data exists (step S12, Yes branch), the enqueue unit 211 executes enqueue processing (step S13).

If there is no unprocessed data (step S12, No branch), the enqueue unit 211 returns to step S11.

FIG. 12 is a flow chart showing an example of enqueue processing (step S13 in FIG. 11) of the enqueue unit 211. As shown in FIG.

The enqueue unit 211 increments (updates) cnt_eq, which is a sample number for enqueue (enqueue sample number) (step S201).

The enqueue unit 211 determines the internal TS based on the updated enqueue sample number (step S202).

The enqueue unit 211 determines whether or not the number of generations has been updated based on the determined internal time stamp TS (step S203). Specifically, the enqueuing unit 211 determines whether or not a generation is updated based on whether or not a predetermined number of RTP packets have been received since the first RTP packet was received in each generation. For example, if the reception of 100 packets is defined as one generation, the enqueue unit 211 has already received 100 packets in one generation, and determines that there is generation update when a new packet (the 101st packet) is received. do.

If the number of generations is updated (step S203, Yes branch), the enqueue unit 211 refers to the session ID, the number of generations, the slope a1, and the adjustment amount acquired from the estimation unit 205 (step S204).

The enqueue unit 211 updates the slope a1 (step S205).

The enqueue unit 211 determines the scheduled dequeue time DQT(cnt_eq(id)) using the updated slope a1 (step S206). Specifically, the enqueue unit 211 determines the scheduled dequeue time DQT using equation (4).

If the number of generations is not updated (step S203, No branch), the enqueue unit 211 determines the scheduled dequeue time DQT using equation (4) (step S207).

The enqueue unit 211 stores the enqueue sample number (cnt_eq(id)), packet data, connection information, packet reception time RT (cnt_eq(id)), and internal time stamp TS (cnt_eq(id)) in the jitter buffer 202 ( step S208).

The enqueue unit 211 registers the connection ID, the scheduled dequeue time DQT (cnt_eq(id)), and the storage location of the packet data in the dequeue schedule list (step S209).

The enqueuing unit 211 writes the data to be enqueued into the jitter buffer 202 (step S210). The enqueuing unit 211 also hands over the data to be enqueued to the estimating unit 205 .

In this way, the TrGW 10 acquires the slope a1 and the adjustment amount when the number of generations is updated, and determines the scheduled dequeue time using the acquired slope a1 and the adjustment amount. That is, the TrGW 10 reflects the adjustment value to the time (scheduled dequeue time) at which packets are extracted from the jitter buffer 202 when the generation changes. In other words, the TrGW 10 reflects the adjustment value on the scheduled dequeue time again after receiving a predetermined number of packets (after the generation is updated) after reflecting the adjustment value on the scheduled dequeue time.

FIG. 13 is a flow chart showing an example of the operation of the dequeue unit 212 included in the buffer control unit 203. As shown in FIG.

The dequeue unit 212 refers to the TSC counter value (step S301).

The dequeue unit 212 refers to the scheduled dequeue time list 213 and determines the target to be dequeued next (step S302).

The dequeue unit 212 checks whether the current TSC counter value is after the dequeue time (scheduled dequeue time) (step S303).

If the current TSC counter value is after the dequeue time (step S303, Yes branch), the dequeue unit 212 reads the packet data from the jitter buffer 202 and writes the data to the transmission buffer (step S304).

If the current TSC counter value is not after the dequeue time (step S303, No branch), the dequeue unit 212 returns to step S301.

The dequeue unit 212 increments (updates) cnt_dq(id), which is the dequeue sample number (dequeue sample number) (step S305).

FIG. 14 is a flow chart showing an example of the operation of the transmission unit 204. As shown in FIG.

The transmission unit 204 refers to the transmission buffer (step S21) and checks whether unprocessed data exists (step S22).

If unprocessed data is included (step S22, Yes branch), the transmission unit 204 packetizes the data (step S23).

If unprocessed data is not included (step S22, No branch), the transmission unit 204 returns to the process of step S21.

The transmitting unit 204 transmits the packetized data (step S24).

FIG. 15 is a flow chart showing an example of the operation of estimation section 205 .

The estimation unit 205 receives the data packet for estimating the slope a1 from the buffer control unit 203 (step S31).

The estimation unit 205 determines whether the data packet is the first received packet in generation g (step S32).

If the packet is the first received packet (step S32, Yes branch), the estimation unit 205 calculates the difference (TS(k)-TS(nb(id))) from the initial time stamp value TS (step S33).

If the packet is not the first received packet (step S32, No branch), the estimation unit 205 stores the initial time stamp value TS(nb(id)) (step S34).

The estimation unit 205 confirms the update period (step S35). Specifically, the estimation unit 205 confirms whether or not the difference calculated in step S33 is equal to or greater than a threshold.

When the difference is equal to or greater than the threshold (step S35, Yes branch), the estimation unit 205 determines delay packing (DP determination; step S36).

If the difference is not equal to or greater than the threshold (step S35, No branch), the estimation unit 205 temporarily stores the packet reception time RT, timestamp value TS, and scheduled dequeue time DQT of generation g (step S37). .

After the DP determination, the estimation unit 205 calculates the slope a1 and the adjustment amount g (step S38).

After that, the estimation unit 205 updates the number of generations (step S39).

FIG. 16 is a flow chart showing an example of the operation of the DP determination (step S36 in FIG. 15) by the estimation unit 205. As shown in FIG.

The estimation unit 205 calculates E1 to E3 based on the above equation (8) (step S401).

The estimation unit 205 confirms the calculated value of E1 (step S402).

If the value of E1 is "0", the estimation unit 205 determines that the packet is to be estimated (step S405). If the value of E1 is "-1", the estimation unit 205 executes step S403. If the value of E1 is other than "0" and "-1", the estimation unit 205 determines that the packet is not subject to estimation (step S406).

The estimation unit 205 confirms the calculated value of E2 (step S403). If the value of E2 is "0", the estimation unit 205 determines that the packet is to be estimated (step S405). If the value of E2 is "-2", the estimation unit 205 executes step S404. If the value of E2 is other than "0" and "-2", the estimation unit 205 determines that the packet is not subject to estimation (step S406).

The estimation unit 205 confirms the calculated value of E3 (step S404). If the value of E3 is "0", the estimation unit 205 determines that the packet is to be estimated (step S405). If the value of E3 is other than "0", the estimation unit 205 determines that the packet is not subject to estimation (step S406).

FIG. 17 is a flow chart showing an example of the slope a1 and adjustment amount calculation (step S38 in FIG. 15) performed by the estimation unit 205. As shown in FIG.

The estimating unit 205 calculates the slope a1 using the formula (1) or (2) (step S501).

The estimation unit 205 determines whether or not the calculated slope a1 satisfies the condition of Expression (3) (confirms whether a1 satisfies a predetermined condition; step S502).

If the condition is satisfied (step S502, Yes branch), the estimation unit 205 calculates the adjustment amount according to formulas (5) and (6) (step S503).

If the condition is not satisfied (step S502, No branch), the estimation unit 205 initializes the slope a1 and the adjustment amount g (step S504). Specifically, a1(g)=a1(0) and the adjustment amount g=0 are set.

The estimation unit 205 notifies the buffer control unit 203 of the slope a1(g) and the adjustment amount (g) (step S505).

[Hardware configuration]
FIG. 18 is a diagram showing an example of the hardware configuration of the TrGW 10. As shown in FIG. The TrGW 10 has the configuration illustrated in FIG. For example, the TrGW 10 includes a CPU (Central Processing Unit) 11, a memory 12, a communication means such as a NIC (Network Interface Card) 13, etc., which are interconnected by an internal bus.

However, the configuration shown in FIG. 18 is not meant to limit the hardware configuration of the TrGW 10 . The TrGW 10 may include hardware not shown. The number of CPUs and the like included in the TrGW 10 is not limited to the example shown in FIG.

The memory 12 is a RAM (Random Access Memory), a ROM (Read Only Memory), an auxiliary storage device (such as a hard disk), or the like.

The functions of TrGW 10 are implemented by the processing modules described above. The processing module is implemented by the CPU 11 executing a program stored in the memory 12, for example. Also, the program can be downloaded via a network or updated using a storage medium storing the program. Furthermore, the processing module may be realized by a semiconductor chip. In other words, the functions performed by the processing modules may be realized by some kind of hardware or software executed using hardware.

As described above, the TrGW 10 according to the first embodiment uses the RTP time stamp attached to the RTP packet and the TSC (Time Stamp Counter) value at the time of receiving the RTP packet to determine the clock of the terminal 30-1, which is the opposite device. The deviation is estimated for each session. Using the estimated value, the TrGW 10 synchronizes the packet transfer interval when transferring the received RTP packets to the transfer destination device with the sending terminal, thereby reducing the delay inside the jitter buffer 202 due to clock skew. To prevent. As a result, the existing problem of jitter buffer control is solved, in which when the reception rate is slower than the dequeue rate due to clock skew, the delay increases gradually until the packet is dropped, which leads to voice degradation. That is, the TrGW 10 can transfer the RTP packets to the transfer destination device at a transmission interval close to the transmission interval of the RTP packets of the opposite device and with a certain delay time even in an environment where network synchronization cannot be used.

For example, referring to FIG. 19, even if the reception speed is faster or slower than the dequeue speed due to clock drift, the delay (packet transfer interval) is affected by the jitter buffer depth due to the amount of adjustment made as appropriate. converge.

For example, consider a case where the clock accuracy of the opposite device (terminal 30-1) is −100 ppm and the clock accuracy of TrGW 10 is +100 ppm. In this case, the clock of the TrGW 10 is delayed by 200 ppm from the counterpart device. According to the RTP time stamp value (TS value) attached to the RTP packet received by the TrGW 10, when the TrGW 10 transmits packets at a predetermined time interval (for example, 20 ms of the packetization cycle), the data in the jitter buffer 202 in the TrGW 10 stays. However, the TrGW 10 according to the first embodiment controls the jitter buffer 202 so as to cancel the clock shift even when the delay occurs due to the clock shift as in the above example.

In the above example, the TrGW 10 regards the time of 20 ms×(1-200 ppm) as 20 ms and performs packet transfer. As a result, if the above control is not performed, one packet will stay in 100 seconds (=20ms/200ppm), but the TrGW 10 can eliminate the staying of the packet by the above control.

In addition, in estimating the clock deviation under the condition of transmission with Delay Packing, it is determined whether or not it is Delay Packing from the periodicity of burst reception. data that are not used for estimation.

[Modification]
Note that the configuration and operation of the communication system described in the above embodiment are examples, and various modifications are possible. For example, the communication system may have the following configurations or operations.

The TrGW 10 may adjust the transmission interval according to the RTP time stamp difference after performing jitter absorption for packets other than voice packets.

Alternatively, the TrGW 10 may estimate the clock deviation from the duration of RFC (Request for Comments) 4733.

In order to transmit DTMF (Dual-Tone Multi-Frequency) signals, an IP phone may use a telephone-event signal described in RFC4733. AMR-NB and G.I. The RTP time stamp value added to a voice packet such as 711 means the time of the head data of the packet, but the telephone-event signal means the time of start of the same DTMF event. Also, the duration of DTMF is expressed in the duration field.

Normally, the packetization cycle is the same as voice packets, and the duration of DTMF events is often 40 ms or longer. Therefore, packets with the same RTP timestamp and different duration values may be transmitted continuously in 20 ms cycles. be. In addition, RFC4733 defines that the last packet of the Event should be transmitted with Ebit=1, and that the same packet should be transmitted three times.

For the above reason, it is not enough to refer to the RTP timestamp to reproduce the transmission interval of telephone-event packets, and it is necessary to use the value converted into the RTP timestamp at the time of dequeue.

FIG. 20 is a flow chart showing an example of TS calculation processing for telephone-event correspondence.

The estimation unit 205 determines whether the received packet is a telephone-event packet or a voice packet (step S601).

If it is a voice packet, the estimation unit 205 sets the RTP timestamp value to the internal timestamp used for setting the dequeue time (step S602). Specifically, the estimation unit 205 sets the internal TS value (cnt_eq)=TS value (Lcnt_eq).

In the case of a telephone-event, estimation section 205 converts the Ebit, Duration, and RTP sequence number into an RTP timestamp value equivalent to that of a voice packet. Specifically, the estimation unit 205 checks the value of Ebit (step S603).

If not Ebit=1 (last packet), the estimating unit 205 determines the internal TS value by the following equation (9) (step S604).

[Formula 9]
Internal TS value (cnt_eq) = TS value (cnt_eq) + Duration (cnt_eq) - Sampling frequency x ptime

If Ebit=1 (last packet), the estimation unit 205 determines the internal TS value by the following equation (10) (step S605).

[Formula 10]
Internal TS value (cnt_eq) = {SN(cnt_eq)-SN(cnt_eq-1)} x sampling frequency x ptime + internal TS (cnt_eq-1)

In addition, AMR-NB, G.I. 711 has a sampling frequency of 8 KHz, and ptime is a packetization period (eg, 20 ms).

In this way, even when the TrGW 10 receives a packet related to a telephone-event, it can estimate the clock shift between devices and transfer the packet at the transmission rate (transmission interval) of the opposite device.

From the above description, the industrial applicability of the present invention is clear, and the present invention can be suitably applied to voice RTP packet transfer equipment that requires low-delay packet transmission and fluctuation absorption. . For example, use in a TrGW located at the boundary between an IP-POI network that connects different mobile carriers and the own carrier's network is assumed.

Some or all of the above embodiments may also be described in the following additional remarks, but are not limited to the following.
[Appendix 1]
This is the same as the communication device according to the first aspect described above.
[Appendix 2]
The estimation unit
Preferably, the communication device according to appendix 1, wherein a slope of a regression line between the time stamp and the reception time of the received packet is calculated as the clock deviation reflection value.
[Appendix 3]
Preferably, when a plurality of packets are burst-received, the estimating unit does not use packets other than the last received packet among the plurality of burst-received packets for calculating the slope of the regression line. is the communication device according to appendix 2;
[Appendix 4]
The buffer control unit
The first reception is performed based on the time obtained by multiplying the difference between the corresponding time stamps of the first reception packet and the second reception packet received immediately before the first reception packet by the slope of the regression line. 4. A communication device, preferably according to clause 3, for determining when to read a packet from said buffer.
[Appendix 5]
The estimation unit
5. Preferably, the communication device according to any one of Appendices 1 to 4, wherein an adjustment value for canceling a time difference between the counterpart device and the self device accumulated due to a clock shift between the counterpart device and the self device is calculated.
[Appendix 6]
The estimation unit
Preferably, the communication device according to appendix 5, wherein, in a predetermined period, an average value of a period during which received packets are stored in the buffer is calculated, and the adjustment value is calculated based on the calculated average value.
[Appendix 7]
The buffer control unit
7. The communication device, preferably according to appendix 5 or 6, wherein said adjustment value is reflected in the time of retrieving said received packet from said buffer.
[Appendix 8]
The buffer control unit
After a predetermined number of packets have been received after the adjustment value is reflected in the time at which the received packet is extracted from the buffer, the adjustment value is again reflected in the time at which the received packet is extracted from the buffer. Communication device as described.
[Appendix 9]
Preferably, according to any one of Appendices 1 to 8, the clock used for measuring the reception time of the received packet has a higher frequency and higher accuracy than the clocks used for the operation of the receiver and the transmitter. Communication device.
[Appendix 10]
The estimation unit
Preferably, the communication device according to appendix 1, wherein the clock deviation reflection value is calculated from the two time stamps and the reception time of the received packet.
[Appendix 11]
This is the same as the communication method according to the second aspect described above.
[Appendix 12]
It is as the program related to the above-mentioned 3rd viewpoint.
Note that the form of Appendix 11 and the form of Appendix 12 can be developed into the form of Appendix 2 to the form of Appendix 10 in the same manner as the form of Appendix 1.

The disclosures of the cited patent documents and the like are incorporated herein by reference. Within the framework of the full disclosure of the present invention (including the scope of claims), modifications and adjustments of the embodiments and examples are possible based on the basic technical concept thereof. Also, various combinations or selections of various disclosure elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) within the framework of the full disclosure of the present invention (including partial deletion) is possible. That is, the present invention naturally includes various variations and modifications that can be made by those skilled in the art according to the entire disclosure including claims and technical ideas. In particular, any numerical range recited herein should be construed as specifically recited for any numerical value or subrange within that range, even if not otherwise stated.

10 TrGW
11 CPUs
12 memory 13 NIC
20 IBCF
30-1, 30-2 terminal 100 communication device 101, 201 receiver 102, 203 buffer controller 103, 204 transmitter 104, 205 estimator 202 jitter buffer 206 TSC 207 connection manager 211 enqueue 212 dequeue 213 dequeue Appointment time list

Claims (10)

a receiver that receives a packet from a counterpart device;
a buffer controller that controls writing and reading of received packets to and from the buffer;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
an estimating unit for estimating a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
The estimating unit calculates a slope of a regression line between the time stamp and the reception time of the received packet as the clock deviation reflection value, and when a plurality of packets are received in burst, Packets other than the last received packet are not used for calculating the slope of the regression line ,
The communication device, wherein the buffer control unit determines a time to extract the received packet from the buffer using the clock deviation reflection value . The buffer control unit
The first reception is performed based on the time obtained by multiplying the difference between the corresponding time stamps of the first reception packet and the second reception packet received immediately before the first reception packet by the slope of the regression line. 2. The communication device of claim 1 , determining when to read packets from the buffer. The estimation unit
3. The communication device according to claim 1 , wherein an adjustment value for canceling a time difference between said counterpart device and its own device accumulated due to a clock shift between said counterpart device and its own device is calculated. a receiver that receives a packet from a counterpart device;
a buffer controller that controls writing and reading of received packets to and from the buffer;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
an estimating unit for estimating a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
The buffer control unit determines a time to extract the received packet from the buffer using the clock deviation reflection value,
The estimating unit calculates an average value of a period during which the received packets are stored in the buffer in a predetermined period, and accumulates the average value based on the calculated average value due to the clock shift between the counterpart device and the own device. A communication device that calculates an adjustment value for canceling a time difference between a device and its own device . The buffer control unit
5. The communication device according to claim 3 , wherein said adjustment value is reflected in the time at which said received packet is extracted from said buffer. a receiver that receives a packet from a counterpart device;
a buffer controller that controls writing and reading of received packets to and from the buffer;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
an estimating unit for estimating a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
The buffer control unit determines a time to extract the received packet from the buffer using the clock deviation reflection value,
The estimating unit calculates an adjustment value for canceling the time difference between the counterpart device and the self device, which is accumulated due to the clock deviation between the counterpart device and the self device,
The buffer control unit
The adjustment value is reflected in the time at which the received packet is extracted from the buffer, and after a predetermined number of packets are received after the adjustment value is reflected in the time at which the received packet is extracted from the buffer, the adjustment value is again adjusted. in the time of removing the received packet from the buffer. a receiver that receives a packet from a counterpart device;
a buffer into which received packets are written;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
In a communication device comprising
an estimating step of estimating a clock deviation reflection value reflecting the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
and a buffer control step of determining a time to retrieve the received packet from the buffer using the clock deviation reflection value ;
In the estimating step, the slope of a regression line between the time stamp and the reception time of the received packet is calculated as the clock deviation reflection value, and when a plurality of packets are burst-received, the plurality of burst-received packets are calculated. packet other than the last received packet is not used for calculating the slope of the regression line . a receiver that receives a packet from a counterpart device;
a buffer into which received packets are written;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
In a communication device comprising
an estimating step of estimating a clock deviation reflection value reflecting the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
and a buffer control step of determining a time to retrieve the received packet from the buffer using the clock deviation reflection value ;
In the estimating step, the average value of the period during which the received packets are stored in the buffer is calculated for a predetermined period, and based on the calculated average value, the counterpart device accumulates due to the clock shift between the counterpart device and the own device. A communication method for calculating an adjustment value for eliminating the time difference between a device and its own device . a receiver that receives a packet from a counterpart device;
a buffer into which received packets are written;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
A computer mounted on a communication device comprising
an estimation process of estimating a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
buffer control processing for determining a time to extract the received packet from the buffer using the clock deviation reflection value;
and
In the estimation process, the inclination of a regression line between the time stamp and the reception time of the received packet is calculated as the clock deviation reflection value, and when a plurality of packets are burst-received, the plurality of burst-received packets are calculated. A program that does not use packets other than the last received packet among them for calculating the slope of the regression line . a receiver that receives a packet from a counterpart device;
a buffer into which received packets are written;
a transmission unit that transmits the received packet read from the buffer to a transfer destination device;
A computer mounted on a communication device comprising
an estimation process of estimating a clock deviation reflection value that reflects the clock deviation between the opposing device and the own device based on the reception time of the received packet and the timestamp included in the received packet;
a process of determining a time to extract the received packet from the buffer using the clock deviation reflection value;
and
In the estimation process, the average value of the period during which the received packets are stored in the buffer is calculated for a predetermined period, and based on the calculated average value, the counterpart apparatus accumulates due to the clock shift between the counterpart apparatus and the own apparatus. A program that calculates an adjustment value to eliminate the time difference between the device and its own device .

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