公开(公告)号：US11438857B2

公开(公告)日：2022-09-06

申请号：US17296447

申请日：2019-11-22

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Kaoru Arai ,  Hiroki Sakuma ,  Masahiro Nakagawa ,  Shunichi Tsuboi

IPC: H04W56/00

Abstract: A SW used in the time transmission system in which a master node and a slave node perform transmission and reception of a precision time protocol (PTP) packet via the SW and the time of the master node is synchronized based on time information of the transmission and reception includes a delay calculator that measures an intra-device delay between input and output of the PTP packet to and from the SW, and a delay information writing unit that appends the intra-device delay measured by the delay calculator to a packet subsequent to the PTP packet, and outputs the appended packet to an output destination of the PTP packet.

公开(公告)号：US20210314134A1

公开(公告)日：2021-10-07

申请号：US17264626

申请日：2019-07-17

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroki Sakuma ,  Kaoru Arai ,  Takaaki Hisashima ,  Ryuta Sugiyama ,  Shunichi Tsuboi ,  Osamu Kurokawa ,  Kazuyuki Matsumura

IPC: H04L7/00 ,  H04B10/25 ,  H04B10/548 ,  H04B10/67

Abstract: [Problem] To reduce a total equipment cost.
[Solution] A local device (20A) of a time synchronization system (10A) includes a path switching unit (33) that connects respective remote devices (40A1 to 40An) using individual optical fibers (60a to 60n) and switches the respective optical fibers (60a to 60n) sequentially in a cyclic order, a counter unit (31), a phase difference memory unit (30), and a table unit (32). The counter unit (31) counts a pulse signal P1d demodulated by a PPS demodulation unit (23) to obtain a count value (T1). The phase difference memory unit (30) stores the count value (T1) as path information in association with a phase difference (φ1) detected by a phase detection unit (22), and outputs, when the count value (T1) is input, the phase difference (φ1) associated with this path information indicated by the count value (T1) to the variable delay unit (24). When the count value (T1) is input, the table unit (32) outputs a path switching signal (K) for switching to the next optical fiber (60n) in the cyclic order to the path switching unit (33) and the path switching unit (33) performs switching to the next optical fiber (60n).

公开(公告)号：US11750358B2

公开(公告)日：2023-09-05

申请号：US17431576

申请日：2020-02-13

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Masahiro Nakagawa ,  Kaoru Arai ,  Hiroki Sakuma ,  Shunichi Tsuboi

IPC: H04B10/07 ,  H04L7/00 ,  H04B10/077

CPC classification number: H04L7/0075 ,  H04B10/0775

Abstract: An optical transmission device of each node simultaneously sends a plurality of signals having different wavelengths as delay measurement signals to a transmission path. The optical transmission device determines a delay value that reflects a propagation delay calculated based on an arrival time difference between a plurality of wavelengths in a signal received from another node, and determines a waiting time amount based on the delay value and the propagation delay. The optical transmission device notifies the other node of the delay value. Each optical transmission device outputs the received signal from the other node with a delay of the waiting time amount. The optical transmission device generates an optical intermittent signal obtained by selecting and multiplexing any of time information, the delay measurement signal, and communication information. A reception side extracts a desired multiplexed signal from the received optical intermittent signals.

公开(公告)号：US11196533B2

公开(公告)日：2021-12-07

申请号：US16968062

申请日：2019-02-15

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroki Sakuma ,  Kaoru Arai ,  Ryuta Sugiyama ,  Takaaki Hisashima ,  Shunichi Tsuboi ,  Osamu Kurokawa ,  Kazuyuki Matsumura

IPC: H04L7/00 ,  G04G7/00 ,  G06F1/14

Abstract: [Problem] To synchronize timings of transmitting and receiving a pulse signal (1 PPS signal) at a constant interval between communication apparatuses even in a case where an optical fiber connecting the communication apparatuses fluctuates in an optical characteristic and an optical fiber length.
[Solution] The time synchronization system 20 transmits and receives a pulse signal at a constant interval between a local apparatus L (apparatus L) and a remote apparatus R (apparatus R) connected through the two-core bidirectional optical fibers F1 and F2 to synchronize time. A propagation delay amount τ1 in the fiber F1 is calculated, from a proportional relationship between T1 and T2 and a proportional relationship of τud and τ1, where T1 represents a propagation delay time difference between a pulse signals P1 and P4 of an identical wavelength λ1 returned after transmitting a pulse signal P1 of wavelength λ1 and a pulse signal P2 of wavelength λ2 different from λ1 to the remote apparatus R, T2 represents a propagation delay time difference between the pulse signal P1 of wavelength λ1 and a pulse signal P3 of wavelength λ2, and τud represents the round-trip delay time between the apparatuses L and R. The pulse signals P1 and P2 are transmitted with a time difference td corresponding to a difference between the current and last calculated propagation delay amounts τ1 being set so that the difference is zero.

公开(公告)号：US10063321B2

公开(公告)日：2018-08-28

申请号：US15528629

申请日：2015-11-27

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Kei Kitamura ,  Takashi Kotanigawa ,  Takafumi Hamano ,  Kaoru Arai ,  Masahiro Yokota ,  Hideki Maeda ,  Yoshiaki Yamada ,  Takuya Ohara ,  Kengo Shintaku

IPC: H04B10/50 ,  H04J14/08 ,  H04B10/40 ,  H04B10/516

CPC classification number: H04B10/50 ,  H04B10/03 ,  H04J3/00 ,  H04J3/16 ,  H04J14/08

Abstract: There is provided a tray which is connected to a plurality of transmitters that multicarrier-transmit a plurality of parallel signals by optical subcarriers. The framer selects time slots to be allocated to a path to be accommodated such that the number of optical subcarriers corresponding to the time slots satisfies a predetermined condition on the basis of empty time slots which are specified by path accommodation information indicating a correspondence between paths allocated to a client signal and time slots in a signal frame and the optical subcarriers corresponding to the empty time slots indicated by time slot information indicating a correspondence between the time slots and the optical subcarriers, and sets the selected time slot in the path accommodation information. The framer sets a client signal to the time slots on the basis of the path accommodation information.

公开(公告)号：US11927923B2

公开(公告)日：2024-03-12

申请号：US16977988

申请日：2019-03-05

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Takaaki Hisashima ,  Hiroki Sakuma ,  Kaoru Arai ,  Ryuta Sugiyama ,  Shunichi Tsuboi ,  Osamu Kurokawa ,  Kazuyuki Matsumura

IPC: G04R20/02 ,  G01S19/21 ,  G01S19/25 ,  G04G5/00 ,  G04G7/00

CPC classification number: G04R20/02 ,  G01S19/21 ,  G01S19/256 ,  G04G5/002 ,  G04G7/023

Abstract: A management apparatus in a time synchronization system includes a time variation information receiving unit configured to acquire time variation information and position information of a time synchronization apparatus, a position information classifying unit configured to classify time synchronization apparatuses into predetermined categories based on the acquired position information, a time variation analysis configured to determine majority based on whether patterns of time variation of the time synchronization apparatuses belonging to an identical category are identical to each other, and to analyze the time variation based on the determined results, and a filtering and delivery unit configured to output an instruction to block the time information received from the positioning satellite, to the time synchronization apparatus having abnormal time variation. A GPS-FW includes a filtering determination unit configured to blocks the time information received from a GPS satellite in a case where a block instruction is received from the management apparatus.

公开(公告)号：US11791922B2

公开(公告)日：2023-10-17

申请号：US17429172

申请日：2020-02-06

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Masahiro Nakagawa ,  Kaoru Arai ,  Hiroki Sakuma ,  Shunichi Tsuboi

IPC: H04J3/06

CPC classification number: H04J3/0682 ,  H04J3/0667 ,  H04J3/0673

Abstract: A time synchronization mechanism is provided. A second transmission device includes: a transmission section configured to transmit packets for delay calculation for a plurality of wavelengths to the corresponding time transmission device simultaneously; and a reception section configured to calculate a propagation delay Dms on a path from the corresponding time transmission device to the second transmission device based on a difference between the arrival times of the packets for delay calculation for the plurality of wavelengths received, receive a propagation delay Dsm on a path from the second transmission device to the corresponding time transmission device calculated, and calculate a propagation delay Dmax that is larger than any of the propagation delay Dms and the propagation delay Dsm. The reception section transmits a received PTP packet to a slave node after a waiting delay Wms calculated by subtracting the propagation delay Dms from the propagation delay Dmax.

公开(公告)号：US20220078736A1

公开(公告)日：2022-03-10

申请号：US17299118

申请日：2019-11-28

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Kaoru Arai ,  Hiroki Sakuma ,  Masahiro NAKAGAWA ,  Shunichi Tsuboi

IPC: H04W56/00

Abstract: [Problem] An object is to obtain a time quality of another GM with high accuracy on the basis of a GM a time quality of which is known already.
[Solution] A first TC 20 includes a time comparison unit 23 that calculates time difference information by comparing first time information of a first PTP processing unit 12 and second time information of a second PTP processing unit 22 with each other. In addition, a quality calculation device 5 measures time difference information until time difference information obtained by a time comparison unit 23 of the first TC 20 and time difference information obtained by a time comparison unit 43 of a second TC 40 match each other, and obtains a GM time quality of a second GM 30 on the basis of a transmission time error of the time transmission network 2 at a timing when both of pieces of the time difference information match each other.

公开(公告)号：US11240141B2

公开(公告)日：2022-02-01

申请号：US16971507

申请日：2019-02-15

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Ryuta Sugiyama ,  Kaoru Arai ,  Hiroki Sakuma ,  Takaaki Hisashima ,  Shunichi Tsuboi ,  Osamu Kurokawa ,  Kazuyuki Matsumura

IPC: H04L12/721 ,  H04B7/185 ,  H04J3/06 ,  H04J3/14

Abstract: [Problem] To select an optimal transmission path having a minimum total MTIE value of total MTIE values between a plurality of master apparatuses configured to transmit time information serving as a reference and a specific relay apparatus configured to receive the time information via a plurality of relay apparatuses to achieve time synchronization.
[Solution] A time path selection apparatus 30 selects a transmission path employed for time synchronization, on the basis of a MTIE value evaluated in each of relay apparatuses 13 to 16, between master apparatuses 11 and 12 configured to transmit time information serving as a reference and a relay apparatus 15 or 16 at an edge configured to receive the time information via a relay apparatus 13 or 14 to achieve the time synchronization. The time path selection apparatus 30 includes a time information reception unit 31 configured to receive the MTIE value evaluated in each of the relay apparatuses 13 to 16, and an optimal path derivation unit 33 configured to evaluate, on the basis of the received MTIE value, a total MTIE value for every transmission path in transmission paths between the relay apparatus 15 and the master apparatuses 11 and 12 and to select and derive, as the transmission path employed for the transmission path for time synchronization, a transmission path where the total MTIE value is a minimum (170 ns).

公开(公告)号：US10250348B2

公开(公告)日：2019-04-02

申请号：US15526927

申请日：2015-11-26

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yoshiaki Yamada ,  Kengo Shintaku ,  Takuya Ohara ,  Kei Kitamura ,  Takashi Kotanigawa ,  Takafumi Hamano ,  Kaoru Arai ,  Masahiro Yokota ,  Hideki Maeda

IPC: H04J3/06 ,  H04J14/02 ,  H04J14/08 ,  H04J3/16 ,  H04J14/00 ,  H04J3/07

Abstract: In the optical transport system a transport frame generator divides a transport frame accommodating plural client signals into plural transmission signals. Subcarrier transmission units convert the signals into optical signals using different optical carriers and transmit the converted optical signals. Subcarrier reception units receive the transmitted optical signals and convert the optical signals into reception signals. A transport frame termination unit combines the reception signals to restore the transport frame. A time-demultiplexing processor time-demultiplexes the restored transport frame to be separated into the client signals. A time slot control unit determines a new time slot allocation when time-multiplexing the client signals in the transport frame and stops supply of electric power to a subcarrier transmission unit and a subcarrier reception unit that transmit and receive an optical signal to which the client signals are not allocated.