JP6157064B2 - Communication apparatus and clock synchronization method - Google Patents

Description

  The present disclosure relates to a communication device and a clock synchronization method. In particular, the present invention relates to a communication device and a clock synchronization method for synchronizing a system clock between a transmission side and a reception side of a communication device in audio / video transmission between a plurality of communication devices.

  When communicating between a plurality of wireless communication devices, it is necessary to establish synchronization. As a conventional clock synchronization method, a method disclosed in Patent Document 1 has been proposed. The clock synchronization method described in Patent Document 1 will be briefly described.

  A transmitting-side wireless communication device (hereinafter referred to as “transmitting device”) adds a program clock reference (PCR) in a packet generation process. PCR is a system time clock (STC: System Time Clock) representing time information counted by the system clock of the transmitting apparatus, and indicates a counter value given in the packet generation process. The transmission device transmits the generated packet to a wireless communication device on the reception side (hereinafter referred to as “reception device”).

  The packet to which the PCR transmitted from the transmission device is added reaches the reception device after the transmission delay time. Since the transmission delay time fluctuates in the transmission path (for example, IP network), the transmission delay time until the packet reaches the receiving apparatus varies.

  The receiving device receives the packet with the PCR added after the transmission delay time from the transmitting device, and the difference value (STC-PCR) between the STC given in the packet receiving process and the PCR given to the received packet Is calculated. In addition, the receiving device selects a PCR having a small difference value (STC-PCR) from a certain number of PCRs. The receiving device synchronizes the system clocks of the transmitting device and the receiving device based on the selected PCR and the STC provided in the packet receiving process of the receiving device.

Japanese Patent No. 4100144

The present inventors examined a communication device and a clock synchronization method for synchronizing system clocks between a transmission device and a reception device. However, the conventional communication apparatus and clock synchronization method for synchronizing the system clocks of the transmission apparatus and the reception apparatus have a problem that the time required for establishing synchronization becomes long.
Accordingly, the present disclosure provides a communication device and a clock synchronization method that can reduce the time required for establishing synchronization in order to solve the above-described problem.

The communication device of the present disclosure is a communication device that receives a packet from another communication device, and the other communication device includes a data storage unit that stores data and a data transmission period assigned to the other communication device. A data read control unit that controls reading of data from the data storage unit based on a transmission data allowable amount in the data storage unit, and reads data stored in the data storage unit in a data transmission period, A header adding unit that adds time information to generate a packet, and a transmission unit that transmits the packet in the same data transmission period as the data transmission period in which the packet is generated. A retransmission detection unit for detecting that retransmission of a packet has occurred by the other communication device, a detection result by the retransmission detection unit, and the packet Based on first time information that is time information included in the second time information and second time information that is time information of the communication device, a first time used for clock synchronization among the first time information. A synchronization time information selection unit for selecting information, and a clock synchronization unit for synchronizing clocks of the communication device and the other communication device using the first time information selected by the synchronization time information selection unit; And when the retransmission detection unit detects that a retransmission of a packet has occurred, the synchronization time information selection unit determines whether the first time information after the occurrence of retransmission and the second time information are The difference is selected from the first time information after convergence within a predetermined range.

  According to the present disclosure, the time required for establishing synchronization can be shortened.

1 is a block diagram illustrating a configuration example of a wireless communication system according to an embodiment of the present disclosure. 1 is a block diagram illustrating a configuration example of a transmission device in a wireless communication system according to a first embodiment. The figure which shows the band allocation example of the radio | wireless resource in embodiment The flowchart which shows the operation example at the time of the packet generation of the transmitter in 1st Embodiment The block diagram which shows the structural example of the transmitter and receiver which considered the WDE specification in 1st Embodiment The figure which shows an example of the timing which PCR is transmitted / received in 1st Embodiment The block diagram which shows the structural example of the receiver in the radio | wireless communications system in 2nd Embodiment. The flowchart which shows the operation example at the time of packet reception of the receiver in 2nd Embodiment The block diagram which shows the structural example of the transmitter and receiver which considered the WDE specification in 2nd Embodiment The figure which shows an example of the timing which PCR is transmitted / received in 2nd Embodiment The block diagram which shows the structural example of the receiver in the radio | wireless communications system in 3rd Embodiment. The flowchart which shows the operation example at the time of packet reception of the receiver in 3rd Embodiment The figure which shows an example of the timing at which the joint packet in 3rd Embodiment is transmitted / received

<Background to this disclosure>
In the clock synchronization method disclosed in Patent Document 1, the receiving apparatus selects a PCR having a small difference value (STC-PCR) from a certain number of PCRs. Therefore, the number of PCRs to be extracted is small, and is necessary for system clock synchronization. It took time to obtain a certain number of PCRs. In addition, it is necessary to transmit a large number of PCRs, which consumes a lot of radio resources.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a communication device and a clock synchronization method that can shorten the synchronization time and can efficiently use radio resources.
<Outline of this disclosure>

  The communication device of the present disclosure is a communication device that transmits a packet to another communication device, and based on a data storage unit that stores data and a transmission data allowable amount in a data transmission period assigned to the communication device, A data read control unit that controls reading of data from the data storage unit, and reads data stored in the data storage unit in a data transmission period, adds time information to the read data, and packet Data from the data storage unit based on the header adding unit that generates the data, the data amount of the packet generated by the header adding unit, and the transmission data allowable amount in the data transmission period assigned to the communication device A data read control unit for controlling reading of the data.

  According to this configuration, it is possible to shorten the time from when the time information for clock synchronization is added to the packet until the packet is transmitted. For this reason, the time information added to the packet is highly reliable, so that the clock can be accurately synchronized even if part of the time information added to the packet is omitted. Therefore, the synchronization time can be shortened and radio resources can be used efficiently.

  Further, the communication device according to the present disclosure is a communication device that receives a packet from another communication device, the retransmission detection unit detecting that retransmission of the packet has occurred by the other communication device, and the retransmission detection unit As a result of the detection, the first time information that is the time information included in the packet and the second time information that is the time information of the communication device are used to synchronize the clocks of the first time information. A synchronization time information selection unit that selects first time information to be used, and a clock of the communication device and the other communication device are synchronized using the first time information selected by the synchronization time information selection unit. And a clock synchronization unit.

  According to this configuration, when retransmission of a packet occurs, time information with low reliability is not used for clock synchronization. Therefore, with respect to highly reliable time information, the clock can be synchronized with high accuracy even if some addition to the packet is omitted on the transmission side. Therefore, the synchronization time can be shortened and radio resources can be used efficiently.

  Further, the communication device according to the present disclosure is a communication device that receives a packet from another communication device, and when receiving a combined packet in which a plurality of packets are combined, the number of packets included in the combined packet, and the combined packet A synchronization time information correction unit that corrects time information included in the packet based on the order of the packets in the packet, and the communication device and the other using the time information corrected by the synchronization time information correction unit. A clock synchronization unit that synchronizes the clock with the communication device.

  According to this configuration, even when a combined packet is received, the time information in a state where there is no packet combination can be adjusted. Therefore, since the reliability of time information can be improved, the clock can be synchronized with high accuracy even if the transmission side partially omits the addition of time information to the packet. Therefore, the synchronization time can be shortened and radio resources can be used efficiently.

  The clock synchronization method of the present disclosure is a clock synchronization method in a communication device that transmits a packet to another communication device, and the data is based on a transmission data allowable amount in a data transmission period assigned to the communication device. A step of controlling reading of data from the storage unit, reading of data stored in the data storage unit, and time information for clock synchronization between the communication device and the other communication device in the read data; In addition, based on the step of generating a packet, the data amount of the generated packet, and the transmission data allowable amount in the data transmission period assigned to the communication device, the data from the data storage unit A data read control unit that controls reading.

  According to this method, the time from when the time information for clock synchronization is added to the packet until the packet is transmitted can be shortened. For this reason, the time information added to the packet is highly reliable, so that the clock can be accurately synchronized even if part of the time information added to the packet is omitted. Therefore, the synchronization time can be shortened and radio resources can be used efficiently.

Further, the clock synchronization method of the present disclosure is a clock synchronization method in a communication device that receives a packet from another communication device, and detects that a retransmission of the packet has occurred by the other communication device; Based on presence / absence of retransmission of the packet, first time information that is time information included in the packet, and second time information that is time information of the communication device, the clock of the first time information Selecting first time information to be used for synchronization, and using the selected first time information to synchronize clocks of the communication device and the other communication device.

  According to this method, when retransmission of a packet occurs, time information with low reliability is not used for clock synchronization. Therefore, with respect to highly reliable time information, the clock can be synchronized with high accuracy even if some addition to the packet is omitted on the transmission side. Therefore, the synchronization time can be shortened and radio resources can be used efficiently.

  The clock synchronization method according to the present disclosure is a clock synchronization method in a communication device that receives packets from another communication device, and when a combined packet in which a plurality of packets are combined is received, the number of packets included in the combined packet Correcting the time information included in the packet based on the order of the packets in the combined packet, and using the corrected time information to clock the communication device and the other communication device Synchronizing.

  According to this method, even when a combined packet is received, the time information in a state where there is no packet combination can be adjusted. Therefore, since the reliability of time information can be improved, the clock can be synchronized with high accuracy even if the transmission side partially omits the addition of time information to the packet. Therefore, the synchronization time can be shortened and radio resources can be used efficiently.

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

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 1000 according to an embodiment of the present disclosure. The wireless communication system 1000 includes an audio / video transmission device 30, a transmission device 31, a reception device 32, and an audio / video reception device 33. The transmission device 31 and the reception device 32 are connected by a wireless communication line.

  The transmission device 31 and the reception device 32 are examples of communication devices, and the wireless communication system 1000 may include a plurality of transmission devices 31 or reception devices 32.

  The audio / video transmission device 30 outputs, for example, audio data / video data (at least one of audio data and video data) to the transmission device 31.

  The transmission device 31 receives the audio data / video data from the audio / video transmission device 30 and transmits the packet to the reception device 32 at a predetermined timing.

  The receiving device 32 receives the packet from the transmitting device 31 and outputs the audio data / video data included in the packet to the audio / video receiving device 33.

  The audio / video receiving device 33 receives audio data / video data from the receiving device 32. The input audio data / video data corresponds to the data output by the audio / video transmission device 30. The audio / video receiving device 33 is a monitor, for example.

Next, a configuration example of the transmission device 31 will be described.
FIG. 2 is a block diagram illustrating a configuration example of the transmission device 31 in the wireless communication system 1000.

  The transmission device 31 includes an audio / video I / F unit 311, a clock generation unit 312, a data storage unit 313, a header addition unit 314, a transmission data allowable amount calculation unit 315, a transmission data amount count unit 316, a data read control unit 317, And a transmission / reception unit 318.

  The audio / video I / F (interface) unit 311 processes the audio / video data input from the audio / video transmission device 30 and transfers the converted audio / video data to the data storage unit 313. The processing by the audio / video I / F unit 311 includes, for example, format conversion processing.

  The clock generation unit 312 generates the STC of the transmission device 31 synchronized with the timing of the input audio / video data, and notifies the header addition unit 314 of the STC.

The data storage unit 313 stores the audio / video data transferred from the audio / video I / F unit 311. In addition, the data storage unit 313 responds to a voice / video data read stop instruction from the data read control unit 317 or a notification that the packet capacity that can be held in an internal memory (not shown) of the transmission / reception unit 318 has exceeded a predetermined amount. The audio / video data output to the header adding unit 314 is stopped. The transmission / reception unit 318 transmits the packet after temporarily holding it in an internal memory (not shown).
The audio / video data reading stop instruction is instruction information for stopping the audio / video data reading from the data storage unit 313.
By storing data in the data storage unit 313, an instantaneous difference between the data input speed from the audio / video I / F unit 311 and the data output speed to the header adding unit 314 is absorbed.

  In addition, the data storage unit 313 outputs the audio / video packet to the header adding unit 314 in accordance with the transmission rate in transmission of the audio / video packet (at least one of the audio packet and the video packet) by the transmission / reception unit 318. Therefore, the transmission / reception unit 318 can transmit a packet at a predetermined timing. That is, the amount of packets is adjusted by the data storage unit 313 so that packets are not excessively transferred to the transmission / reception unit 318.

  The header adding unit 314 reads the audio / video data stored in the data storage unit 313, divides the audio / video data into packets having a predetermined size or less, and generates a packet. The header adding unit 314 adds header information to the generated packet and transfers the audio / video packet to the transmission / reception unit 318. The header information includes a PCR indicating a counter value in the STC packet generation process notified from the clock generation unit 312. The PCR is one piece of time information for clock synchronization between the transmission device 31 and the reception device 32. The header adding unit 314 notifies the transmission data amount counting unit 316 of the data amount (packet amount) of the generated audio / video packet.

  The header adding unit 314 may not add PCR to all audio / video packets, and may omit adding PCR to some audio / video packets.

  The transmission data allowable amount calculation unit 315, before transmitting the audio / video packet, for example, a data transmission period for which radio resources are allocated in advance based on a transmission rate in transmission of the audio / video packet, and an allocation period of the data transmission period And decide.

  In addition, the transmission data allowable amount calculation unit 315 generates a control packet for securing a data transmission period, and transmits data to and from a wireless communication apparatus (hereinafter also referred to as “communication management apparatus”) that manages the data transmission period. Adjust the transmission period. In the data transmission period, for example, in consideration of the occurrence of retransmission in the wireless section, a certain amount of margin is given to the actually required data transmission period.

  The function as the communication management device may be handled by the transmission device 31 or the reception device 32, or may be handled by another wireless communication device. The control packet is transmitted / received by the transmission / reception unit 318 in the same manner as the audio / video packet.

  Further, the transmission data allowable amount calculation unit 315 calculates the transmission data allowable amount based on the data transmission period and the transmission rate of the packet on the communication line. Note that the transmission data allowable amount can have a certain margin.

  The transmission data amount counting unit 316 counts the data amount (packet amount) of the packet generated by the header adding unit 314. The data amount of the packet corresponds to the data amount transmitted by the transmission / reception unit 318.

  Based on the transmission data allowable amount calculated by the transmission data allowable amount calculation unit 315 and the transmission data amount counted by the transmission data amount counting unit 316, the data read control unit 317 sends data from the data storage unit 313 to the header addition unit 314. Controls data reading.

Further, the data read control unit 317 controls data read so that the transmission data amount in the predetermined period does not exceed the transmission data allowable amount.
As a result, it is possible to prevent the transmission apparatus 31 from generating a transmission waiting time, which is the time from when the PCR is added to the packet until the packet is transmitted.

  The transmission device 31 includes, for example, a CPU and a RAM. When the CPU executes a program stored in the RAM, the header addition unit 314, the transmission data allowable amount calculation unit 315, the transmission data amount counting unit 316, and the data Each function of the read control unit 317 is realized.

  The configuration of the reception device 32 may be a general configuration of the reception device, or may be the configuration of the reception devices 32B and 32C in the second embodiment and the third embodiment described later.

  FIG. 3 is a diagram illustrating an example of bandwidth allocation of radio resources. The bandwidth allocation information notification period 1201 (1201-1, 1201-2) is a period for the communication management device to notify the bandwidth allocation information. The band allocation information includes a contention transmission period 1202 (1202-1, 1202-2) and a transmission apparatus transmission period 1203 (1203-1, 1203-2). The contention transmission period 1202 is a period during which data can be transmitted by all wireless communication apparatuses in the wireless communication system 1000. The transmission device transmission period 1203 is a data transmission period individually assigned to the transmission device 31, and is assigned for each adjusted assignment cycle.

  After receiving the allocation of the data transmission period from the communication management device, the transmission data allowable amount calculation unit 315 calculates the transmission data allowable amount that can be transmitted in the allocated data transmission period at the start of each data transmission period.

  Also, the transmission data allowable amount calculation unit 315 notifies the transmission data amount counting unit 316 and the data read control unit 317 of the start of the data transmission period, and notifies the data read control unit 317 of the calculated transmission data amount.

  The transmission data allowable amount calculated by the transmission data allowable amount calculation unit 315 is not the maximum data amount that can be transmitted in the data transmission period, but excludes the margin from the data amount calculated from the transmission speed in the transmission of the audio / video packet. The amount of data that was used.

  The transmission data amount count unit 316 receives a data transmission period start notification from the transmission data allowable amount calculation unit 315 and resets a transmission data amount count value for counting the transmission data amount.

  Also, the transmission data amount counting unit 316 starts counting the data amount of the audio / video packet notified from the header adding unit 314 and notifies the data read control unit 317 of the transmission data amount count value.

  The data read control unit 317 receives the start notification of the data transmission period from the transmission data allowable amount calculation unit 315 and cancels the audio / video data read stop instruction notified to the data storage unit 313.

  Further, when the transmission data amount count value reaches the transmission data allowable amount, the data read control unit 317 notifies the data storage unit 313 of an audio / video data read stop instruction.

  The transmission / reception unit 318 holds the audio / video packet transferred from the header addition unit 314 and transmits it to the reception device 32 in accordance with the data transmission period managed by the transmission data allowable amount calculation unit 315.

  Also, when the transmission / reception unit 318 does not receive a response packet for the audio / video packet transmitted from the receiving device 32, the transmission / reception unit 318 transmits the audio / video packet again for a certain number of times or for a certain period. In addition, the transmission / reception unit 318 discards the audio / video packet that has not been transmitted during the data transmission period.

  Next, an operation example when the transmission apparatus 31 generates an audio / video packet will be described with reference to FIG.

  In step ST401, the transmission data allowable amount calculation unit 315 determines the start of the data transmission period allocated from the radio management apparatus. As a result of the determination, at the start of the data transmission period, the transmission data allowable amount calculation unit 315 notifies the transmission data amount count unit 316 and the data read control unit 317 of the start of the data transmission period. Then, the process proceeds to step ST402. Until the data transmission period is started, the determination of the start of the data transmission period (step ST401) is continued.

  In step ST402, the transmission data allowable amount calculation unit 315 calculates the transmission data allowable amount transmitted in the data transmission period, and notifies the data read control unit 317 of the transmission data allowable amount. Then, the process proceeds to step ST403.

  In step ST403, the transmission data amount count unit 316 receives the start notification of the data transmission period notified from the transmission data allowable amount calculation unit 315, and resets the transmission data amount count value. Also, the transmission data amount counting unit 316 starts counting the transmission data amount of the audio / video packet notified from the header adding unit 314 and notifies the data read control unit 317 of the transmission data amount count value. Then, the process proceeds to step ST404.

  In step ST404, the data read control unit 317 receives the start notification of the data transmission period notified from the transmission data allowable amount calculation unit 315, and cancels the audio / video data read stop instruction notified to the data storage unit 313. Then, the process proceeds to step ST405.

  In step ST405, the data read control unit 317 compares the transmission data allowable amount notified from the transmission data allowable amount calculation unit 315 with the transmission data amount count value notified from the transmission data amount counting unit 316. If the transmission data amount count value is less than the transmission data allowable amount, the process proceeds to step ST406, and if the transmission data amount count value is equal to or larger than the transmission data allowable amount, the process proceeds to step ST412.

  In step ST406, the transmission / reception unit 318 determines whether the packet capacity of the internal memory of the transmission / reception unit 318 is a predetermined amount. If the packet capacity has reached a predetermined amount, data reading is awaited, and if it is less than the predetermined amount, the process proceeds to step ST407.

  In step ST407, when the packet capacity of the internal memory of the transmission / reception unit 318 is not a predetermined amount, the data storage unit 313 has not been notified of the audio / video data read stop instruction from the data read control unit 317. The data is output to the header adding unit 314. Then, the process proceeds to step ST408.

  In step ST408, the header addition unit 314 generates audio / video packets by dividing the audio / video data output from the data storage unit 313 into packets having a predetermined size or less, and adds header information to the audio / video packets. To do. Then, the process proceeds to step ST409.

  In step ST409, the header addition unit 314 determines whether or not the audio / video packet is added with PCR. If it is an audio / video packet to which PCR is added, the process proceeds to step ST410, and if it is an audio / video packet to which PCR is not added, the process proceeds to step ST411.

  In step ST410, in the case of an audio / video packet to which PCR is added, the header addition unit 314 adds the counter value in the packet generation process as PCR to the header information as the STC notified from the clock generation unit 312. Then, the process proceeds to step ST411.

  In step ST411, the transmission data amount counting unit 316 adds the data amount of the audio / video packet notified from the header adding unit 314 to the transmission data amount count value, and updates the transmission data amount counter value. Then, the process proceeds to step ST405.

  In step ST412, the data read control unit 317 generates an audio / video data read stop instruction, and stops outputting audio / video data from the data storage unit 313. Then, the process proceeds to step ST401.

Next, a specific communication method of the wireless communication system 1000 will be described.
In the embodiment of the present disclosure, a clock (for example, a system clock) is synchronized between the transmission device 31 and the reception device 32 in AV streaming in PBSS communication of the WiGig (Wireless Gigabit) standard. PBSS (Personal basic service set) communication is ad hoc communication managed by a single communication device. Note that the processing delay in the transmission device 31 can be improved even in cases other than PBSS communication. Further, it is assumed that the transmission device 31 and the reception device 32 perform one-to-one communication.

  FIG. 5 is a block diagram illustrating a configuration example of the transmission device 31 (TX) and the reception device 32 (RX) in consideration of the WiGig Display Extension (WDE) specification.

The transmission device 31 includes a WDE-PAL (Protocol Adaptation Layer) block 110, a MAC (Media Access Control) block 120, and a PHY block 130. The WDE-PAL block 110 executes processing in the PAL layer of the WDE. The MAC block 120 executes processing in the MAC layer of the WDE. The PHY block 130 executes processing in the PHY layer of the WDE.

The WDE-PAL block 110 is an HDMI (High-Definition Mu).
lMedia interface) / I / F unit 111, RAM 112, WDE processing unit 113, and PCR providing unit 114. The MAC block 120 includes a RAM (Random Access Memory) 121, a MAC processing unit 122, and an SP transmission stop determination unit 123.
The I / F unit is not limited to HDMI, but may be a display port.

  The HDMI / I / F unit 111 has a function as the audio / video I / F unit 311 in FIG. The RAM 112 has a function as the data storage unit 313. The WDE processing unit 113 and the PCR adding unit 114 have functions as a clock generation unit 312 and a header addition unit 314.

  The RAM 121 corresponds to an internal memory provided in the transmission / reception unit 318. The SP transmission stop determination unit 123 has functions as a transmission data allowable amount calculation unit 315, a transmission data amount count unit 316, and a data read control unit 317. The MAC processing unit 122 and the PHY block 130 have a function as the transmission / reception unit 318.

  Next, an operation example of the transmission device 31 will be described with reference to FIG.

  The MAC block 320 determines a transmission data allowable amount (transmission packet allowable number) according to the length of the data transmission period. The MAC block 320 counts the amount of data (input data amount) input from the WDE-PAL block 310. When the determined allowable number of transmission packets is reached, the MAC block 320 notifies the WDE-PAL block 310 of the WAIT of the packet. The packet WAIT notification includes, for example, a voice / video data read stop instruction.

  When receiving a packet WAIT notification from the MAC, the WDE-PAL block 310 causes the RAM 112 to wait for the packet.

  Further, the MAC block 320 cancels the WAIT notification of the WDE-PAL block 310 before the data transmission period starts. The WDE-PAL block 310 resumes the processing of the RAM 112 by releasing the WAIT notification from the MAC block 320. When the WDE-PAL block 310 resumes the processing of the RAM 112, the PCR adding unit 114 adds PCR to the packet.

  As described above, the transmission device 31 prescribes the number of packets to be transmitted in the data transmission period, and assigns the PCR with the delay suppressed by temporarily waiting the packet in the RAM 112 of the WDE-PAL block 310 before the PCR is granted. it can. That is, the transmission apparatus 31 provides PCR in accordance with a predetermined data transmission period.

  According to the transmission device 31, since a PCR with a suppressed delay is given, it is not necessary for the reception device 32 to select an effective PCR from a plurality of PCRs, and the amount of PCR transmission can be reduced.

  Next, the timing at which PCR is transmitted and received between the transmission device 31 and the reception device 32 will be described with reference to FIG.

When the transmission device 31 generates a packet for synchronizing the system clock with the reception device 32 in the data transmission period assigned by the wireless management device, the transmission device 31 adds the PCR 51 (51-1 to 51-6). The packet is transmitted to the receiving device 32. The PCR 51 indicates a counter value in the packet generation process of the STC 50 that represents time information counted by the system clock of the transmission device 31.

The packet added with the PCR 51 transmitted from the transmission device 31 reaches the reception device 32 after a transmission delay time. That is, PCR 53-1 from timing t 0 of PCR 51-1.
The transmission delay is until the timing t1.
Here, in the transmission of the audio / video packet in the wireless communication system 1000, the fluctuation of the transmission delay time after being transmitted from the transmission device 31 is a level that can be ignored in WiGig based on short-range wireless communication. The fluctuation of the transmission delay time after the PCR addition is mainly determined by the time from the PCR addition to the packet transmission in the transmission device 31.

  The transmission device 31 controls the output of audio / video data by the data storage unit 313 and the addition of PCR by the header addition unit 314 according to the allocated data transmission period. That is, after confirming that it is a period during which transmission is possible, PCR is added and transmission is performed. Therefore, fluctuations in the transmission delay time in the transmission device 31 can be suppressed.

  The reception device 32 receives from the transmission device 31 a packet to which the PCR 53 (53-1 to 53-6) to which the fluctuation of the transmission delay time is suppressed is added. In addition, the reception device 32 compares the PCR 53 with the STC 52 of the reception device 32 at the time of packet reception.

  As a result of the comparison, when the PCR 53 is larger than the STC 52, the receiving device 32 determines that the system clock of the receiving device 32 is delayed from the system clock of the transmitting device 31. The receiving device 32 increases the system clock frequency of the receiving device 32 and controls the difference value (STC52-PCR53) to approach 0, thereby generating the STC of the receiving device 32.

  On the other hand, as a result of the comparison, when the PCR 53 is smaller than the STC 52, the reception device 32 determines that the system clock of the reception device 32 is ahead of the system clock of the transmission device 31. The receiving device 32 delays the frequency of the system clock of the receiving device 32, controls the difference value (STC52-PCR53) to approach 0, and generates the STC of the receiving device 32.

  Therefore, according to the wireless communication system 1000, the PCR 51 can be transmitted from the transmission device 31 to the reception device 32 with the fluctuation of the transmission delay time suppressed, so that it is not necessary to extract the PCR 53 by the reception device 32. Therefore, efficient system clock synchronization is possible in which the synchronization time between the transmission device 31 and the reception device 32 can be shortened and the amount of radio resources used can be reduced.

(Second Embodiment)
FIG. 7 is a block diagram illustrating a configuration example of the reception device 32B in the wireless communication system 1000B according to the second embodiment of the present disclosure. The receiving device 32B performs processing in consideration of packet retransmission.

  The reception device 32B includes a transmission / reception unit 321, a retransmission detection unit 322, a header analysis unit 323, a synchronization time information selection unit 324, a clock synchronization unit 325, a data storage unit 326, and an audio / video I / F unit 327.

  The transmission / reception unit 321 receives the audio / video packet transmitted from the transmission device 31B, and checks the CRC of the audio / video packet added by the transmission device 31B. If the check result is correct, the transmission / reception unit 321 transmits a response packet to the audio / video packet to the transmission device 31B, and transfers the audio / video packet to the retransmission detection unit 322.

  The retransmission detection unit 322 detects the occurrence of retransmission using at least one of the retransmission flag (retry bit) and the sequence number of the audio / video packet transferred from the transmission / reception unit 321.

  The retransmission flag is validated by the transmission device 31B when the transmission device 31B does not receive a response packet from the reception device 32B and a retransmission occurs.

  The sequence number is added by the transmission apparatus 31B in accordance with the order of the audio / video packets transmitted by the transmission apparatus 31B. The sequence number of the packet in the retransmission is the same as the sequence number of the packet for which no response packet has been received.

  The retransmission detection unit 322 transfers the audio / video packet to the header analysis unit 323 in the order of the sequence numbers. In addition to the audio / video packet for which the retransmission flag is valid, the retransmission detection unit 322 also indicates that retransmission has occurred for an audio / video packet that has waited for reception of a previously transmitted audio / video packet. Is sent to the synchronization time information selection unit 324 (retransmission occurrence notification). The retransmission detection unit 322 can determine that a previously transmitted audio / video packet could not be received, for example, because the packet was not input from the transmission / reception unit 321 in order of sequence number.

  The header analysis unit 323 analyzes the header of the audio / video packet transferred from the retransmission detection unit 322, extracts the PCR added to the header, and notifies the synchronization time information selection unit 324 of the PCR. In addition, the header analysis unit 323 transfers the audio / video data from which the header has been removed to the data storage unit 326.

  The synchronization time information selection unit 324 uses the retransmission notification from the retransmission detection unit 322, the PCR from the header analysis unit 323, and the STC from the clock synchronization unit 325 to synchronize the PCR to the system clock by the clock synchronization unit 325. Determine whether to use. The PCR from the header analysis unit 323 is an example of first time information, and the STC from the clock synchronization unit 325 is an example of second time information.

  For example, the synchronization time information selection unit 324 includes a difference value (STC-PCR) obtained from the STC from the clock synchronization unit 325 and the PCR from the header analysis unit 323, and the difference previously held by the synchronization time information selection unit 324. Compare the value. The difference value held in advance is, for example, a difference value (STC-PCR) obtained using a PCR included in a packet acquired in the past and for which retransmission has not been detected by the retransmission detection unit 322.

  As a result of the comparison, if the difference between the two difference values falls within a predetermined range, the synchronization time information selection unit 324 determines that there is no influence of retransmission, and the difference value (STC-PCR) for which the retained difference value is obtained. And the clock synchronization unit 325 is notified of the PCR.

  On the other hand, if the difference between the two difference values does not fall within the predetermined range as a result of the comparison, the synchronization time information selecting unit 324 determines that there is an effect of retransmission, and determines the difference value (STC) obtained as the held difference value. -PCR) is not updated.

  As described above, when the synchronization time information selection unit 324 receives the retransmission occurrence notification, the difference between the PCR from the header analysis unit 323 and the STC from the clock synchronization unit 325 is the difference value (STC-PCR) obtained. As a result of comparison with the held difference value, the PCR is selected after convergence within a predetermined range.

  The clock synchronization unit 325 compares the PCR from the synchronization time information selection unit 324 with the STC managed by the clock synchronization unit 325. Note that the STC managed by the clock synchronization unit 325 is the STC of the receiving device 32B.

  As a result of the comparison, when the PCR is larger than the STC, the clock synchronization unit 325 determines that the system clock of the receiving device 32B is behind the system clock of the transmitting device 31B. The clock synchronizer 325 increases the frequency of the system clock of the receiving device 32, controls the difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32B.

  As a result of the comparison, if the PCR is smaller than the STC, the clock synchronization unit 325 determines that the system clock of the receiving device 32B is ahead of the system clock of the transmitting device 31B. The clock synchronizer 325 delays the frequency of the system clock of the receiving device 32B, controls the obtained difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32B.

  The clock synchronization unit 325 notifies the generated STC to the synchronization time information selection unit 324 and notifies the audio / video I / F unit 327 of the system clock to be controlled.

  The data storage unit 326 stores audio / video data transferred from the header analysis unit 323. Further, the data storage unit 326 transfers the audio / video data to the audio / video I / F unit 327 in accordance with the read request from the audio / video I / F unit 327. Here, the data storage unit 326 is used to absorb an instantaneous difference between the data input speed from the header analysis unit 323 and the data output speed to the audio / video I / F unit 327.

  The audio / video I / F unit 327 outputs audio / video data from the data storage unit 326 in synchronization with the system clock of the reception device 32B synchronized with the system clock of the transmission device 31B notified from the clock synchronization unit 325.

  The audio / video I / F unit 327 processes audio / video data (for example, format conversion processing). The audio / video I / F unit 327 transfers the converted audio / video data to the audio / video receiving device 33 at a constant transmission speed.

  The receiving device 32B includes, for example, a CPU and a RAM. When the CPU executes a program stored in the RAM, the retransmission detection unit 322, the header analysis unit 323, the synchronization time information selection unit 324, and the clock synchronization unit 325 Implement each function.

  The configuration of the transmission device 31B may be a general configuration of the transmission device, or may be the configuration of the transmission device 31 in the first embodiment described above. Further, the transmission apparatus 31B may omit adding PCR to all the audio / video packets, and omit adding PCR to some of the audio / video packets.

  Further, the transmission apparatus 31B may receive the allocation of the transmission apparatus transmission period 1203 shown in FIG. Further, the transmission device 31B may transmit the audio / video packet in the contention transmission period 1202 without receiving the assignment of the transmission device transmission period 1203.

  Next, an operation example when the receiving device 32B receives an audio / video packet will be described with reference to FIG.

In step ST701, retransmission detection section 322 determines whether or not the packet from transmission / reception section 321 is a retransmission packet. When the predetermined retransmission determination condition is satisfied, the retransmission detection unit 322 determines that the audio / video packet has undergone retransmission. The predetermined retransmission determination condition is that when the retransmission flag of the audio / video packet input to the retransmission detection unit 322 is valid, or the packet is input later than the audio / video packet to which the subsequent sequence number is assigned. If included. If it is a retransmission packet, the process proceeds to step ST703, and if it is not a retransmission packet, the process proceeds to step ST702.

  In step ST702, retransmission detection section 322 determines whether or not it is waiting to receive an audio / video packet to which a sequence number prior to the input packet has been assigned. When waiting for reception, retransmission detection section 322 determines that retransmission has occurred in the previous audio / video packet, and moves to step ST703. On the other hand, when not waiting for reception, retransmission detection section 322 determines that retransmission has not occurred in the previous audio / video packet, and moves to step ST704.

  In step ST703, retransmission detection section 322 generates information (retransmission occurrence information) indicating that retransmission has occurred, and notifies synchronization time information selection section 324 (retransmission occurrence notification). And it transfers to step ST704.

  In Step ST704, the header analysis unit 323 analyzes the header of the audio / video packet transferred from the retransmission detection unit 322, extracts the PCR when the header information is added, and extracts the PCR for the synchronization time. The information selection unit 324 is notified. Then, the process proceeds to step ST705.

  In Step ST705, the synchronization time information selection unit 324 determines whether or not a retransmission occurrence notification has been received from the retransmission detection unit 322. If no retransmission notification is received, the mobile terminal makes a transition to step ST706.

  On the other hand, when the notification of occurrence of retransmission is received, the processing of FIG. 8 ends without adjusting the system clock of the receiving device 32B. This is because it is determined that the reliability of the PCR is low when a notification of occurrence of retransmission is received.

  In step ST706, the synchronization time information selection unit 324 determines whether a PCR notification is received from the header analysis unit 323. When the notification of PCR is received, it transfers to step ST707. If the notification of PCR is not received, the system clock of the receiving device 32B is not adjusted, and the process of FIG. 8 ends.

  In step ST707, the synchronization time information selection unit 324 determines the difference value (STC-PCR) obtained from the STC notified from the clock synchronization unit 325 and the PCR notified from the header analysis unit 323, and the synchronization time information selection unit 324. Is compared with the difference value held in advance.

  As a result of the comparison, if the difference between the two difference values is within the predetermined range, the synchronization time information selecting section 324 determines that there is no influence of retransmission, and moves to step ST708.

  On the other hand, if both the difference values do not fall within the predetermined range as a result of the comparison, it is determined that there is an influence of retransmission, the system clock of the receiving device 32B is not adjusted, and the processing of FIG.

  In step ST708, the synchronization time information selection unit 324 updates the held difference value to the obtained difference value (STC-PCR), and proceeds to step ST709.

In step ST709, since the synchronization time information selection section 324 determines that the PCR is not affected by retransmission, the synchronization time information selection section 324 notifies the clock synchronization section 325 of the PCR and moves to step ST710.

  In step ST710, the clock synchronization unit 325 compares the PCR notified from the synchronization time information selection unit 324 with the STC (STC of the receiving device 32B) managed by the clock synchronization unit 325.

  As a result of the comparison, when the PCR is larger than the STC, the clock synchronization unit 325 determines that the system clock of the receiving device 32B is behind the system clock of the transmitting device 31B. The clock synchronizer 325 increases the frequency of the system clock of the reception device 32B, controls the obtained difference value (STC-PCR) to approach 0, and generates the STC of the reception device 32B.

  As a result of the comparison, if the PCR is smaller than the STC, the clock synchronization unit 325 determines that the system clock of the receiving device 32B is ahead of the system clock of the transmitting device 31B. The clock synchronizer 325 delays the frequency of the system clock of the receiving device 32B, controls the obtained difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32B.

  Next, a configuration example of the transmission device 31B (TX) and the reception device 32B (RX) in consideration of the WiGig display extension (WDE) specification will be described with reference to FIG.

  The receiving device 32 includes a PHY block 210, a MAC block 220, and a WDE-PAL block 230. The PHY block 210 executes processing in the PHY layer of the WDE. The MAC block 220 executes processing in the MAC layer of the WDE. The WDE-PAL block 230 executes processing in the PAL layer of the WDE.

  The MAC block 220 includes a RAM 221, a MAC processing unit 222, and a retransmission wait detection unit 223. The WDE-PAL block 230 includes a WDE processing unit 231, a PCR selection unit 232, a clock reproduction unit 233, a RAM 234, and an HDMI / I / F unit 235.

  The RAM 221 corresponds to the internal memory of the transmission / reception unit 321 in FIG. The PHY block 210 and the MAC processing unit 222 have a function as the transmission / reception unit 321. The retransmission wait detection unit 223 has a function as the retransmission detection unit 322.

  The WDE processing unit 231 has a function as the header analysis unit 323. The PCR selection unit 232 has a function as the synchronization time information selection unit 324. The clock recovery unit 233 has a function as the clock synchronization unit 325. The RAM 234 has a function as the data storage unit 326. The HDMI / I / F unit 235 has a function as the audio / video I / F unit 327.

  Next, an operation example of the receiving device 32B will be described with reference to FIG.

  The MAC block 220 detects a packet in which retransmission has occurred, and notifies the WDE-PAL block 230 of the occurrence of retransmission (retransmission occurrence notification). When detecting that retransmission has occurred, a packet that arrived later than the packet identified by the subsequent sequence number after reaching the MAC block 220 may be detected as a retransmission packet. Also, a packet indicating that the retransmission flag is valid (indicating that it is a retransmission) may be detected as a retransmission packet.

When the WDE-PAL block 230 receives the retransmission notification from the MAC block 220, the WDE-PAL block 230 compares the difference value (STC-PCR) obtained from the STC of the receiving device 32 and the PCR from the transmitting device 31. The WDE-PAL block 230 clocks the PCR included in the packet by the clock recovery unit 233 until the obtained difference value (STC-PCR) converges to the vicinity of the difference value (STC-PCR) before notification of occurrence of retransmission. Not used for synchronization.

  Thus, the receiving device 32B can recognize the occurrence of a retransmission packet, and thus can prevent the PCR included in the packet affected by the retransmission from being used for clock synchronization. That is, the receiving device 32B detects the waiting for retransmission, and clocks the PCR included in the packet excluding the retransmission waiting packet in which the retransmission waiting has occurred and the delayed packet that arrives after the retransmission waiting packet after a predetermined delay. Can be used for synchronization.

  According to the receiving device 32B, since the validity of the PCR can be determined in each packet, it is possible to prevent unnecessary PCR from being extracted from a plurality of PCRs. In addition, since a highly reliable PCR is used, the reliability of clock synchronization is improved and the time required for clock synchronization can be shortened.

  Next, the timing at which PCR is transmitted and received between the transmission device 31B and the reception device 32B will be described with reference to FIG.

  In FIG. 10, the transmission device 31B adds PCR 81 (81-1 to 81-7) to the packet in the packet generation process, and transmits transmission timings 84 (84-1 to 84-7) and 85 (85-85) on the communication line. In 3), the packet is transmitted to the receiving device 32B. The PCR 81 indicates a counter value in the packet generation process of the STC 80 that represents time information counted by the system clock of the transmission device 31B.

  The packet added with the PCR 81 transmitted from the transmission device 31B arrives at the reception device 32B after the transmission delay time. Here, in the audio / video transmission in the wireless communication system 1000B, the fluctuation of the transmission delay time after being transmitted from the transmission device 31B is at a level that can be ignored in WiGig based on short-range wireless communication. The fluctuation of the transmission delay time after the PCR is added is mainly determined by the time from the time when the transmitter 31B adds the PCR to the transmission timing 84 (retransmission timing 85 in the case of retransmission) on the communication line transmitted by the transmitter 31B. .

  When retransmission occurs in the previous packet in time, the transmission timing 84-4 of the next packet is later in time than the retransmission timing 85-3 on the communication line. Accordingly, the transmission timings 84-4 and 84-5 of the subsequent packets on the communication line are also delayed compared to the ideal transmission timing.

  The receiving device 32B receives the packet to which the PCR 83 (83-1 to 83-7) is added after the transmission delay time from the transmitting device 31B, and is not affected by the retransmission PCR 83-1, 83-2, 83- Select 6,83-7.

  Subsequently, the reception device 32B compares the selected PCRs 83-1, 83-2, 83-6, 83-7 with the STC 82 of the reception device 32B in the packet reception process. As a result of the comparison, when the PCR is larger than the STC, the receiving device 32B determines that the system clock of the receiving device 32B is behind the system clock of the transmitting device 31B. The receiving device 32B increases the system clock frequency of the receiving device 32B, controls the difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32B.

As a result of the comparison, when the PCR is smaller than the STC, the receiving device 32B determines that the system clock of the receiving device 32B is ahead of the system clock of the transmitting device 31B. The receiving device 32B delays the frequency of the system clock of the receiving device 32B, controls the difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32B.

  That is, when the response packet is not returned from the reception device 32B to the transmitted packet, the transmission device 31B recognizes that the packet has not arrived and retransmits the packet. Compared to the case where there is no packet retransmission after the occurrence of retransmission, the packet transmission interval by the transmission device 31B becomes smaller. This is because when retransmission occurs, data tends to remain in the RAM (see FIG. 9) of the MAC block of the transmission device 31B, and the remaining data is transmitted at a transmittable timing.

  The packet transmission interval is reduced because the intervals between the retransmission timing 85-3 and the transmission timings 84-4 and 84-5 are smaller than the intervals between the transmission timings 84-1 and 84-2 in FIG. Understandable. Thereby, the delay time of packet reception in the receiving device 32B gradually converges.

On the other hand, on the receiving device 32B side, when retransmission occurs, the difference value (PCR-STC) between the PCR included in the packet and the STC of the receiving device 32B increases rapidly. This is because the difference value (PCR-STC) of the packet before the occurrence of retransmission is from timing 81-2 to timing 83-2, whereas the difference value (PCR-STC) of the packet at which retransmission has occurred is This is because the timing is from timing 81-3 to timing 83-3.
Note that after the occurrence of retransmission, the difference value decreases stepwise and converges to the same extent as the difference value before retransmission occurs. When the difference value converges, the receiving device 32B determines that the effect of retransmission has been lost, and resumes clock synchronization using the PCR included in the packet.

  Therefore, according to the receiving device 32B, even if retransmission occurs, the PCR included in the packet is used for clock synchronization after convergence to a state where it can be considered that there is no influence of retransmission. That is, since the clock synchronization is performed by removing the PCR of the packet affected by the re-transmission, it is possible to improve the clock synchronization reliability and to reduce the synchronization time efficiently.

(Third embodiment)
FIG. 11 is a block diagram illustrating a configuration example of the reception device 32C in the wireless communication system 1000C according to the third embodiment of the present disclosure.

  The receiving device 32C performs processing in consideration of a combined packet in which a plurality of packets are combined. In the combined packet, the transmission packets of the second and subsequent packets in the combined packet are transmitted with a reduced interval. Accordingly, if the PCR value included in the packet is maintained, it is difficult to accurately compare the system clock of the receiving device 32C and the system clock of the transmitting device 31C, so the receiving device 32C corrects (adjusts) the PCR value. To do. Note that the transmitter 31C determines in advance whether or not to send the packet as a combined packet.

  The receiving device 32C includes a transmission / reception unit 321, a packet order calculation unit 328, a header analysis unit 323, a synchronization time information correction unit 329, a clock synchronization unit 325, a data storage unit 326, and an audio / video I / F unit 327. In the receiving device 32C of FIG. 11, the same components as those of the receiving device 32B of FIG. 7 are denoted by the same reference numerals, and description thereof is omitted or simplified. In the present embodiment, differences from the second embodiment will be mainly described.

  If the received audio / video packet is a combined packet obtained by combining a plurality of packets, the transmission / reception unit 321 transmits a response packet to the combined packet to the transmission device 31C, and transmits the audio / video packet to the packet order calculation unit 328. Forward.

  When the audio / video packet transferred from the transmission / reception unit 321 is a combined packet, the packet order calculation unit 328 determines the number of audio / video packets (number of packets) in the combined packet and the order of the audio / video packets in the combined packet. Get the number (packet number) to represent.

  The information on the number of packets may be included in the combined packet, or the packet order calculation unit 328 may count the total number of packets in the combined packet. The packet number information may be included in each packet in the combined packet, or the packet order calculation unit 328 may obtain the packet number by counting the order of each packet in the combined packet.

  The packet order calculation unit 328 notifies the synchronization time information correction unit 329 of the number of packets and the packet number. Also, the packet order calculation unit 328 transfers each audio / video packet to the header analysis unit 323 in the order of input. The packet number is an example of information indicating the packet order, and the packet order may be indicated by other methods.

  The header analysis unit 323 analyzes the header of the audio / video packet transferred from the packet order calculation unit 328, extracts the PCR added to the header, and notifies the synchronization time information correction unit 329 of the PCR.

  The synchronization time information correction unit 329 uses the number of audio / video packets (N) in the combined packet from the packet order calculation unit 328, the packet number (n) in the combined packet, and the PCR from the header analysis unit 323, Correct the PCR value.

For example, the synchronization time information correction unit 329 calculates the corrected PCR by the following (Equation 1) using the transmission interval (Y) of the combined packet shown in FIG.
PCR after correction = PCR + (n / N) × Y (Formula 1)
The synchronization time information correction unit 329 notifies the clock synchronization unit 325 of the corrected PCR.

  The information on the transmission interval (Y) of the combined packet is notified from the transmission device 31C to the reception device 32C, for example, in the bandwidth allocation information notification period 1201 (see FIG. 3). The receiving device 32C holds information on the transmission interval (Y) of the notified combined packet. Note that the information on the transmission interval (Y) of the combined packet is not notified, and a fixed value may be used, and the transmission interval (Y) of the combined packet may be a value equal to or less than the actual transmission interval of the combined packet. .

  The receiving device 32C includes, for example, a CPU and a RAM, and realizes the function of the packet order calculation unit 328 when the CPU executes a program stored in the RAM.

  The configuration of the transmission device 31C may be a general configuration of the transmission device, or may be the configuration of the transmission device 31 in the first embodiment described above. Note that the transmitting device 31C may not add PCR to all audio / video packets, and may omit adding PCR to some audio / video packets.

  Next, an operation example when the receiving device 32C receives an audio / video packet will be described with reference to FIG.

  In step ST1001, the packet order calculation unit 328 calculates the number of audio / video packets (N) in the combined packet transferred from the transmission / reception unit 321 and sends the number of audio / video packets (N) to the synchronization time information correction unit 329. Notice. Then, the process proceeds to step ST1002.

In step ST1002, the packet order calculation unit 328 sets the packet number (n) of the audio / video packet in the combined packet transferred from the transmission / reception unit 321 to 0, which is the number indicating the first packet, and the synchronization time information correction unit 329. To notify. Then, the process proceeds to step ST1003.

  In step ST1003, the header analysis unit 323 analyzes the header of the audio / video packet transferred from the packet order calculation unit 328, and extracts the PCR and adds the synchronization time information correction unit when the PCR is added to the header information. 329 is notified. Then, the process proceeds to step ST1004.

  In Step ST1004, the synchronization time information correction unit 329 determines whether or not the PCR corresponding to the packet number (n) in the combined packet notified from the packet order calculation unit 328 is notified from the header analysis unit 323. When the PCR corresponding to the packet number is notified, the process proceeds to step ST1005, and when not notified, the process proceeds to step ST1007.

  In step ST1005, the synchronization time information correction unit 329 sets the number of audio / video packets (N) in the combined packet, the packet number (n), the PCR from the header analysis unit 323, and the transmission interval (Y) between the combined packets. Use to correct PCR values. For example, the synchronization time information correction unit 329 calculates the corrected PCR using (Equation 1), and notifies the clock synchronization unit 325 of the corrected PCR. Then, the process proceeds to step ST1006.

  In Step ST1006, the clock synchronization unit 325 compares the PCR notified from the synchronization time information correction unit 329 with the STC managed by the clock synchronization unit 325. As a result of the comparison, if the PCR is larger than the STC, it is determined that the system clock of the receiving device 32C is behind the system clock of the transmitting device 31C. The clock synchronizer 325 increases the frequency of the system clock of the receiving device 32C, controls the difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32C.

  On the other hand, if the PCR is smaller than the STC as a result of the comparison, it is determined that the system clock of the receiving device 32C is ahead of the system clock of the transmitting device 31C. The clock synchronization unit 325 delays the frequency of the system clock of the receiving device 32C, controls the difference value (STC-PCR) to approach 0, and generates the STC of the receiving device 32C. When clock synchronization ends, the process proceeds to step S1007.

  In Step ST1007, the packet order calculation unit 328 increments (increases) the packet number (n) of the audio / video packet in the combined packet transferred from the transmission / reception unit 321. Then, the process proceeds to step ST1008.

  In Step ST1008, the packet order calculation unit 328 compares the packet number (n) of the audio / video packet in the combined packet with the number of packets (N) in the combined packet. When the packet number (n) matches the number of packets (N), the processing in FIG. 12 is completed.

  On the other hand, if the packet number (n) and the number of packets (N) do not match, an unprocessed audio / video packet remains, so the packet order calculation unit 328 performs the packet of the audio / video packet in the combined packet. The number (n) is notified to the synchronization time information correction unit 329. And it transfers to step ST1003 again.

  Therefore, according to the receiving device 32C, since the PCR from the transmitting device 31C can be corrected and used for clock synchronization, it is possible to perform efficient system clock synchronization in which the synchronization time can be shortened and the radio resources can be reduced. Become.

  The present disclosure is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Applicable.

  In the above embodiment, the wireless communication between the transmission device and the reception device has been described. However, the present invention is also applicable to wired communication. Even in the case of wired communication, processing delay in the transmission device can be prevented, and transmission standby in the transmission device after PCR is added to the packet can be prevented.

  In the above embodiment, one-to-one communication is assumed, but one-to-many communication may be assumed. Even in one-to-many communication, processing delay in the transmission device can be prevented, and transmission standby in the transmission device after the PCR is attached to the packet can be prevented.

  In the above embodiment, the case where the present disclosure is configured by hardware has been described as an example. However, the present disclosure can also be realized by software in cooperation with hardware.

  Each functional block used in the description of the above embodiment is typically realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Here, it may be an LSI, or may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. For example, a Field Programmable Gate Array (FPGA) that can be programmed after manufacturing the LSI, connection of circuit cells in the LSI, or a reconfigurable processor whose settings can be reconfigured may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The present disclosure is useful for a communication apparatus, a clock synchronization method, and the like that can shorten the synchronization time and can efficiently use radio resources.

1000, 1000B, 1000C Wireless communication system 30 Audio / video transmission device 31, 31B, 31C Transmission device 32, 32B, 32C Reception device 33 Audio / video reception device 110 WDE-PAL block 111 HDMI / I / F unit 112 RAM
113 WDE processing unit 114 PCR adding unit 120 MAC block 121 RAM
122 MAC processing unit 123 SP transmission stop determination unit 130 PHY block 210 PHY block 220 MAC block 221 RAM
222 MAC processing unit 223 Retransmission waiting detection unit 230 WDE-PAL block 231 WDE processing unit 232 PCR selection unit 233 Clock recovery unit 234 RAM
235 HDMI / I / F unit 311 Audio / video I / F unit 312 Clock generation unit 313 Data storage unit 314 Header addition unit 315 Transmission data allowable amount calculation unit 316 Transmission data amount count unit 317 Data read control unit 318 Transmission / reception unit 321 Transmission / reception Unit 322 retransmission detection unit 323 header analysis unit 324 synchronization time information selection unit 325 clock synchronization unit 326 data storage unit 327 audio / video I / F unit 328 packet order calculation unit 329 synchronization time information correction unit

Claims (5)

A communication device that receives a packet from another communication device,
The other communication device is
A data storage unit for storing data;
A data reading control unit that controls reading of data from the data storage unit based on a transmission data allowable amount in a data transmission period allocated to the other communication device;
In a data transmission period, a header adding unit that reads data stored in the data storage unit, adds time information to the read data, and generates a packet;
A transmission unit that transmits the packet in the same data transmission period as the data transmission period in which the packet was generated, and
The communication device
A retransmission detection unit for detecting that retransmission of a packet has occurred by the other communication device;
Based on the detection result by the retransmission detection unit, the first time information that is time information included in the packet, and the second time information that is time information of the communication device, among the first time information, A synchronization time information selection unit for selecting first time information used for clock synchronization;
Using the first time information selected by the synchronization time information selection unit, a clock synchronization unit for synchronizing the clock of the communication device and the other communication device,
When the retransmission time detection unit detects that a retransmission of a packet has occurred, the synchronization time information selection unit determines that a difference between the first time information and the second time information after the occurrence of retransmission is a predetermined value. A communication apparatus that selects from first time information after convergence within a range. A communication device that receives a packet from another communication device,
The other communication device is
A data storage unit for storing data;
A data reading control unit that controls reading of data from the data storage unit based on a transmission data allowable amount in a data transmission period allocated to the other communication device;
In a data transmission period, a header adding unit that reads data stored in the data storage unit, adds time information to the read data, and generates a packet;
A transmission unit that transmits the packet in the same data transmission period as the data transmission period in which the packet was generated, and
The communication device
Synchronous time information that corrects time information included in the packet based on the number of packets included in the combined packet and the order of the packets in the combined packet when a combined packet in which a plurality of packets are combined is received A correction unit;
Using the time information corrected by the synchronization time information correction unit, a clock synchronization unit that synchronizes the clocks of the communication device and the other communication device,
A communication device comprising: The communication device according to claim 2,
The synchronization time information correction unit corrects the time information included in the packet based on the number of packets included in the combined packet, the order of the packets in the combined packet, and the transmission interval of the combined packet. Communication device. A clock synchronization method in a communication device that receives a packet from another communication device,
The clock synchronization method of the other communication device is as follows:
Controlling the reading of data from the data storage unit based on the transmission data allowable amount in the data transmission period allocated to the other communication device;
Reading data stored in the data storage unit, adding time information to the read data, and generating a packet;
Transmitting the packet in the same data transmission period as the data transmission period in which the packet was generated;
Transmitting the packet in the same data transmission period as the data transmission period in which the packet was generated,
The clock synchronization method in the communication device is:
Detecting the occurrence of packet retransmission by the other communication device;
Based on the presence / absence of retransmission of the packet, first time information that is time information included in the packet, and second time information that is time information of the communication device, out of the first time information, Selecting first time information for use in clock synchronization;
Using the selected first time information to synchronize clocks of the communication device and the other communication device,
In the selecting step, when it is detected that the retransmission of the packet has occurred in the detecting step, the difference between the first time information and the second time information after the occurrence of the retransmission is within a predetermined range. Select from the first time information after convergence to
Clock synchronization method. A clock synchronization method in a communication device that receives a packet from another communication device,
The clock synchronization method of the other communication device is as follows:
Controlling the reading of data from the data storage unit based on the transmission data allowable amount in the data transmission period allocated to the other communication device;
Reading data stored in the data storage unit, adding time information to the read data, and generating a packet;
Transmitting the packet in the same data transmission period as the data transmission period in which the packet was generated;
Transmitting the packet in the same data transmission period as the data transmission period in which the packet was generated,
The clock synchronization method in the communication device is:
When receiving a combined packet in which a plurality of packets are combined, correcting the time information included in the packet based on the number of packets included in the combined packet and the order of the packets in the combined packet;
Using the corrected time information to synchronize the clocks of the communication device and the other communication device;
A clock synchronization method.

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