JP6024820B2 - Communication device - Google Patents

Description

  The present invention relates to a communication device, and more particularly to a communication device applied to a packet network.

  In recent years, with an increase in the amount of data transferred over a network, there has been an increasing need for a telecommunications carrier to realize a high-speed data communication network at a low cost. Therefore, a shift from a high-cost network using a time division multiplexing (TDM) method to a low-cost and high-efficiency network using an Internet protocol method (hereinafter referred to as “IP method”). Is being promoted. For example, there is a technology for transferring TDM data using a PWE (Pseudo Wire Emulsion) packet.

  When TDM data is converted to PWE, since TDM data is converted to PWE at a fixed timing and passes through the packet network, it is exchanged with other traffic at other fixed periods or rates on the relayed packet network. Packet collision occurs. Then, since PDV (Packet Delay Variation) is likely to occur, a fluctuation component due to PDV is superimposed on a clock reproduced by ACR (Adaptive Clock Recovery), and there is a possibility that the accuracy of the clock may be lowered.

  As means for solving such a problem, Patent Document 1 discloses a technique for performing clock recovery based on time stamp information that has passed through a packet filter.

  Further, Patent Document 2 discloses a technique for reducing the jitter delay in the apparatus by making the reading time from the jitter buffer variable by using the difference in time stamp information.

International Publication No. 2009/035091 JP 2010-035003 A

  In the technique disclosed in Patent Document 1, there is a problem that a circuit or the like becomes large because a filter or the like for removing the influence of PVD is necessary.

  In the technique disclosed in Patent Document 2, the jitter buffer is controlled, but there is a problem that the influence of jitter itself is not reduced.

  The objective of this invention is providing the communication apparatus which solves the subject mentioned above.

  In order to solve the above problems, the present invention provides a communication apparatus having a function of receiving TDM data and transmitting a PWE packet, and a function of receiving a PWE packet and transmitting TDM data, and the next PWE packet to be transmitted Random timing generation means for changing the transmission timing from a reference value to generate, and PWE packet generation and transmission means for generating a PWE packet having a header including the transmission timing and the received TDM data and transmitting the packet to the packet network; PWE packet receiving means for receiving PWE packets from the packet network and extracting transmission timing information, PWE packet holding means for holding PWE packets, and extracting TDM data from the PWE packets held in the PWE packet holding means for transmission Generated from timing information Using a clock, is characterized by comprising a TDM data extraction output means for outputting the TDM data to the TDM network in a predetermined cycle.

  In order to solve the above problems, the present invention is a communication apparatus having a function of receiving TDM data and transmitting a PWE packet, and changes the transmission timing of a PWE packet to be transmitted next from a reference value. And a PWE packet generation / transmission unit that generates a PWE packet having a header including transmission timing and the received TDM data and transmits the PWE packet to the packet network.

  In order to solve the above problems, the present invention is a communication apparatus having a function of receiving a PWE packet and transmitting TDM data, and receiving a PWE packet from a packet network and extracting transmission timing information. Means, PWE packet holding means for holding the PWE packet, TDM data is extracted from the PWE packet held in the PWE packet holding means, and the TDM data is extracted at a predetermined cycle using the clock generated from the transmission timing information. And a TDM data extracting / outputting means for outputting to the TDM network.

  An effect of the present invention is to provide a communication device that can reduce the influence of PVD with a small circuit scale and can accurately perform clock synchronization between transmitting and receiving nodes.

It is a block diagram which shows the structural example of the communication apparatus in the 1st Embodiment of this invention. It is a block diagram which shows the detailed structural example of the communication apparatus in the 1st Embodiment of this invention. It is a figure which shows the example of a PWE packet format of the communication apparatus in the 1st Embodiment of this invention.

  Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. However, the preferred embodiments described below are technically preferable for carrying out the present invention, but the scope of the invention is not limited to the following.

  [First Embodiment] This embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration example of a communication apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, the present embodiment is composed of an apparatus having a function of converting TDM data into PWE packets and a function of converting PWE packets into TDM data. In FIG. 1, there are a transmission unit 1 and a reception unit 2, and the transmission unit 1 converts TDM data into PWE packets, and the reception unit 2 converts PWE packets into TDM data. Basically, these functions are simultaneously provided in the same apparatus.

  The transmission unit 1 includes a PWE packet generation / transmission unit 3 and a random timing generation unit 5.

  The random timing generation unit 5 generates the transmission timing of the PWE packet to be transmitted next within a predetermined range based on the information on the number of TDM frames stored in one PWE packet. The PWE packet generation / transmission unit 3 generates a PWE packet using the PWE packet header and TDM data, and transmits the PWE packet to the packet network 20 at the transmission timing determined by the random timing generation unit 5.

  In FIG. 1, the receiving unit 2 includes a PWE packet receiving unit 6, a PWE packet holding unit 7, and a TDM data extraction / output unit 8.

  The PWE packet receiving unit 6 receives the PWE packet from the packet network 20 and separates the PWE packet header and the data of the PWE packet.

  The PWE packet holding unit 7 holds the data of the PWE packet written from the PWE packet receiving unit 6 for a certain period. When there is a request from the TDM data extraction / output unit 8, the data of the PWE packet is sent to the TDM data extraction / output unit 8.

  According to the present embodiment, the TDM data received from the TDM network 40 is converted into a PWE packet by the transmission unit 1 and sent to the packet network 20 at the transmission timing determined by the random timing generation unit 5. Then, the PWE packet received from the packet network 20 is generated as TDM data synchronized with the original TDM data by the receiving unit 2 and sent to the TDM network 50.

  The configuration of the communication apparatus according to this embodiment will be described with reference to FIGS. 2 and 3.

  FIG. 2 is a block diagram illustrating a detailed configuration example of the communication apparatus according to the present embodiment.

  FIG. 3 is an example of a PWE packet format in the case of PWE over Ethernet (registered trademark). There is a time stamp field in the PWE header, and random transmission timing information and a time stamp value are stored.

  The communication apparatus of the present embodiment shown in FIG. 2 has a function of converting TDM data into PWE packets and a function of converting PWE packets into TDM data as shown in FIG.

  Reference numerals 10 and 30 in FIG. 2 denote TDM-PWE conversion apparatuses. In the present embodiment, 10 is described as an apparatus for converting TDM data into PWE packets, and 30 is an apparatus for converting PWE packets into TDM data. Basically, these devices are arranged together in the same device.

  Reference numeral 20 in FIG. 2 denotes a general packet network, which includes a layer 2 switch and the like.

  The TDM networks 40 and 50 are networks for transmitting T1 having a frequency of 1.544 MHz and E1 having a frequency of 2.048 MHz according to a general digital leased line standard.

  In FIG. 2, the TDM-PWE converter 10 converts the TDM data received from the TDM network 40 into a PWE packet. Since normal PWE packets are transmitted by packetizing TDM data, the transmission cycle is constant, and the interval is also determined by the number of frames of TDM data encapsulated in one PWE packet. The number of TDM data frames stored in one PWE packet is recommended by the PWE system (SAToP (Structure-Agnostic TDM over Packet): RFC4553), and 8 is required, so the cycle of the reference PWE packet is 125 μs * 8 = 1 ms.

  The TDM-PWE conversion apparatus 10 includes a TDM data termination unit 101 and a TDM data buffer unit 102.

  Further, the TDM-PWE conversion apparatus 10 includes a PWE information storage unit 103, a random timing generation unit 104, a PWE header generation unit 105, a time stamp generation unit 106, and a PWE packet corresponding to the PWE packet generation / transmission unit 3 of FIG. An assembly transmission unit 107 is provided.

  The TDM data termination unit 101 terminates the TDM data and writes the time slot data to the TDM data buffer unit 102. The TDM data buffer unit 102 buffers the data of the TDM time slot terminated and extracted by the TDM data termination unit 101, and sends it to the PWE packet assembly / transmission unit 107.

  The PWE information storage unit 103 stores a PWE packet header and the number of TDM data frames stored in one PWE packet as information necessary for generating a PWE packet in advance.

  Based on the number of TDM data frames stored in one PWE packet stored in the PWE information storage unit 103, the random timing generation unit 104 determines the transmission timing of the next PWE packet to be transmitted within a predetermined range.

  The transmission timing is obtained as a time obtained by shifting the PWE packet to be transmitted next by a predetermined time from the reference time based on the time obtained from the number of TDM data frames stored in one PWE packet. The predetermined time may be set randomly or regularly so as not to exceed one TDM data frame period so as not to cause a reception error on the packet receiving side. The transmission timing is determined for each PWE packet to be transmitted.

  For example, when the number of TDM data frames is 8, the reference PWE packet time is 125 μs * 8 = 1 ms. At this time, the range in which the transmission timing is generated is defined as +/− 5% of the reference time so as not to exceed one TDM data frame period (125 μs). The random timing generation unit 104 determines the transmission timing of the PWE packet to be transmitted next in a range of, for example, +/− 5% with respect to 1 ms, and sends it to the time stamp generation unit 106.

  The PWE header generation unit 105 generates a PWE packet header from the PWE packet generation information set in the PWE information storage unit 103, and outputs the generated PWE packet header to the PWE packet assembly transmission unit 107.

  The time stamp generation unit 106 stores the transmission timing of the PWE packet determined by the random timing generation unit 104 in the time stamp field, and outputs it to the PWE packet assembly transmission unit 107.

  The PWE packet assembly / transmission unit 107 generates a PWE packet using the PWE packet header generated by the PWE header generation unit 105 and the time stamp generation unit 106 and the TDM data read from the TDM data buffer unit 102. The PWE packet assembling / transmitting unit 107 keeps the reference period in accordance with a transmission instruction from the time stamp generating unit 106 for the PWE packet and keeps the transmission timing within a predetermined range for each packet (for example, +/− for 1 ms) The PWE packet is sent to the packet network 20 with a temporal change in the range of 5%.

  2, the TDM-PWE conversion apparatus 30 includes a PWE packet reception decomposition unit 304 and a reception cycle extraction unit 301 as the PWE packet reception unit 6 in FIG. 1. Further, a jitter buffer 305, a TDM data extraction / output unit 306, a PWE packet arrival monitoring unit 302, and a correction unit 303 corresponding to the PWE packet holding unit 7 of FIG.

  The reception cycle extraction unit 301 extracts transmission timing information from the time stamp field added to the PWE header of the PWE packet received by the PWE packet reception decomposition unit 304 and outputs it to the PWE packet arrival monitoring unit 302.

  The PWE packet arrival monitoring unit 302 temporarily stores the transmission timing information output from the reception cycle extraction unit 301 as the arrival timing information of the next arriving PWE packet in a memory (not shown). The arrival time of the packet is estimated, and the arrival timing of the PWE packet from the PWE packet reception decomposition unit 304 is monitored.

  The correction unit 303 includes a PLL (Phase-Locked Loop), and performs clock recovery based on the clock correction information from the PWE packet arrival monitoring unit 302.

  The PWE packet reception / decomposition unit 304 receives the PWE packet from the packet network 20, separates the PWE packet header, and outputs the time stamp field included in the PWE packet header to the reception cycle extraction unit 301. Further, the PWE packet reception / decomposition unit 304 notifies the PWE packet arrival monitoring unit 302 of information on the arrival timing of the PWE packet obtained when the PWE packet is received. Information on the arrival timing of the PWE packet is output to the correction unit 303 and becomes a clock input to the PLL.

  Further, the PWE packet reception / decomposition unit 304 writes the PWE packet (TDM data) in the jitter buffer 305.

  The jitter buffer 305 absorbs the delay time of the packet received when the PWE packet passes through the packet network 20 with respect to the TDM data to be transmitted at the same timing as the TDM data received from the TDM network 40, and the TDM data The data is output to the extraction output unit 306. The TDM data extraction / output unit 306 reads the PWE packet from the jitter buffer 305 at the same period as the TDM data received from the TDM network 40, extracts the TDM data included in the PWE packet, and outputs the TDM data to the TDM network 50.

  The detailed operation of the communication apparatus according to this embodiment will be described with reference to FIGS.

  The TDM-PWE converter 30 regenerates TDM data and TDM clock from the received PWE packet, and outputs TDM data to the TDM network 50.

  The TDM-PWE converter 30 extracts the arrival timing information of the next PWE packet from the transmission timing information of the time stamp field included in the header portion of the received PWE packet, and monitors the arrival of the PWE packet. Then, monitoring is performed while determining whether the arrival time of the PWE packet arrives within a predetermined time based on the timing information described above. If the arrival timing is within a predetermined time when the next PWE packet arrives, the PLL is corrected and the synchronization clock used in the TDM network 40 is set to the TDM network 50. Output.

  In this case, if other traffic is communicated on the packet network 20, ITU-T (International Telecommunication Union Telecommunication Standardization) G. As in 8261, communication of the PWE packet may be hindered by other traffic, and the packet arrival cycle may vary with time.

  The present embodiment operates to reduce this temporal variation.

  That is, TDM data received from the TDM network 40 is stored in the TDM data buffer unit 102 via the TDM data termination unit 101. The PWE information storage unit 103 stores in advance a PWE packet header and the number of TDM data frames stored in one PWE packet as information necessary for generating a PWE packet.

  The PWE header generation unit 105 extracts the information of the PWE packet header from the PWE information storage unit 103, executes PWE packet header generation, and then outputs the PWE packet header to the PWE packet assembly transmission unit 107.

  The random timing generation unit 104 obtains the number of TDM data frames stored in one PWE packet from the PWE information storage unit 103, and calculates the transmission timing at which the PWE packet is transmitted. When the number of TDM data frames stored in one PWE packet is 8, the period of the reference PWE packet is 125 μs * 8 = 1 ms.

  At this time, if the range in which the transmission timing is generated is defined as +/− 5% of the reference period, the random timing generation unit 104 has 1 ms so as not to exceed one TDM data frame period (125 μs). On the other hand, for example, in the range of +/− 5%, the transmission timing of the PWE packet to be transmitted next is determined to move from 1 ms for a predetermined time.

  That is, the reference period is 1 ms, but for example, the next transmission is 1.05 ms, the next is 0.98 ms, the next is 0.95 ms, etc. In the range of −5%, the transmission timing is changed with time from the reference cycle and transmitted.

  When the random timing generation unit 104 determines the transmission timing of the next PWE packet, the random timing generation unit 104 outputs the information to the time stamp generation unit 106.

  The time stamp generation unit 106 stores the transmission timing as transmission timing information in the time stamp field included in the PWE packet header as shown in FIG. 3 and outputs the transmission timing to the PWE packet assembly transmission unit 107.

  The PWE packet assembly / transmission unit 107 receives the TDM data frame number information stored in one PWE packet from the PWE information storage unit 103, the PWE packet header from the PWE header generation unit 105, and the time stamp field from the time stamp generation unit 106. A PWE packet is generated originally. Then, according to the transmission timing stored in the time stamp field output from the time stamp generation unit 106, the transmission timing is temporally changed from the reference period, and the PWE packet is transmitted to the packet network 20.

  The TDM-PWE conversion device 30 is a device opposed to the TDM-PWE conversion device 10 via the packet network 20 and has a function of converting PWE data into TDM data and outputting it to the TDM network 50. At this time, in order to supply a clock synchronized with the TDM network 40 to the TDM network 50, the following processing is performed.

  When receiving the PWE packet via the packet network 20, the PWE packet reception / decomposition unit 304 extracts a time stamp field included in the PWE packet header and outputs the time stamp field to the reception cycle extraction unit 301.

  In addition, the PWE packet reception / decomposition unit 304 notifies the PWE packet arrival monitoring unit 302 of information on the arrival timing of the PWE packet obtained when the PWE packet is received. Further, the PWE packet is stored in the jitter buffer 305.

  The reception cycle extraction unit 301 extracts information from the transmission timing information portion of the time stamp field output from the PWE packet reception decomposition unit 304 as the arrival timing of the next PWE packet arrival, and the PWE packet arrival monitoring unit The arrival timing is notified to 302.

  The PWE packet arrival monitoring unit 302 monitors the arrival of the PWE packet based on the arrival timing information of the next PWE packet received from the reception cycle extraction unit 301. For example, when information of + 5% is received from the reception cycle extraction unit 301, it is assumed that the next PWE packet arrives at a timing delayed by 5% (50 μs) with respect to the 1 ms cycle. Then, the arrival monitoring of the next PWE packet is started around 1.05 ms from the arrival timing of the PWE packet from which the timing information has been extracted.

  The transmission timing information stored in the PWE packet header is different for each PWE packet. Therefore, the PWE packet arrival monitoring unit 302 resets the arrival timing of the next PWE packet every time the PWE packet arrives, and monitors the arrival of the next PWE packet. When the next PWE packet arrives within the monitoring period started according to the transmission timing information, it measures how much delay time has occurred with respect to the arrival timing center time (1.05 ms in the above example). The delay time portion is output to the correction unit 303 as deviation information.

  Based on the deviation information received from the PWE packet arrival monitoring unit 302, the correction unit 303 corrects the arrival timing of the PWE packet with a PLL included in the correction unit 303 and outputs it to the TDM data extraction / output unit 306. I do. The PLL includes a frequency divider and operates as a frequency synthesizer.

According to the above example (a signal having a delay time from 1.05 ms), the PLL phase comparator includes a clock signal output from the PWE packet arrival monitoring unit 302 (the delay time from 1.05 ms in the above example). The generated signal) and the output of the VCO multiplied in frequency are input. The frequency of the VCO output from the PLL is given as design information as the frequency of the clock output to the TDM network 50 (for example, E1 frequency 2.048 MHz). The deviation information received from the PWE packet arrival monitoring unit 302 and the arrival timing information of the PWE packet received from the reception cycle extraction unit 301 are added (a delay time is added to the 1.05 ms cycle in the above example). (This is expressed as a correction cycle C.)
Taking the reciprocal of C, the frequency (1 / C) of the correction period C is obtained. Further, the VCO frequency value (2.048 MHz) output from the PLL is divided by the frequency value (1 / C) of the correction period C to obtain the PLL frequency division ratio (2.048 / 1 / C). Therefore, when the clock signal input to the PLL phase comparator is multiplied by the obtained frequency division ratio (1 / C * 2.048 * C), the VCO frequency clock (2.048 MHz) is output from the PLL. Is done.

  Then, the output clock is output to the TDM data extraction / output unit 306.

  The jitter buffer 305 is a buffer for absorbing the delay time when an arrival delay occurs due to the delay of the packet when the PWE packet passes through the packet network 20, and stores the PWE packet.

  The TDM data extraction / output unit 306 reads the PWE packet from the jitter buffer 305 and extracts the TDM data encapsulated by the PWE packet. Then, TDM data is output to the TDM network 50 using the clock received from the correction unit 306.

  In this way, in this embodiment, the random timing generator 104 transmits the PWE packet once at random timing, thereby avoiding packet delay due to collision with other packets generated on the packet network. Thereafter, the JDM buffer 305 can be used to return to the original timing and output the TDM data to the TDM network 50.

  As described above, according to the present embodiment, the random timing generation unit once transmits the PWE packet at random timing, thereby avoiding packet delay due to collision with other packets generated on the packet network. It becomes possible. Therefore, it is not necessary to remove the influence of packet delay caused by collision with other packets using a filter having a complicated configuration. Therefore, packet delay can be avoided with a small circuit scale without using a filter having a complicated configuration.

  Further, according to the present embodiment, the random timing generation unit once transmits the PWE packet at random timing, thereby avoiding packet delay due to collision with other packets generated on the packet network. . Furthermore, using a jitter buffer, TDM data avoiding packet delay can be returned to the original timing and output to the TDM network. Therefore, it is possible to provide a communication device capable of accurately synchronizing clocks between transmission / reception nodes, rather than making the jitter buffer read time variable to reduce the jitter delay in the device. Become.

  Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention described above.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2013-049786 for which it applied on March 13, 2013, and takes in those the indications of all here.

  The present invention can be used to establish clock synchronization between a plurality of TDM devices by relaying a packet network by PWE.

DESCRIPTION OF SYMBOLS 1 Transmission part 2 Reception part 3 PWE packet generation transmission part 5 Random timing generation part 6 PWE packet reception part 7 PWE packet holding part 8 TDM data extraction output part 10 TDM-PWE conversion apparatus 20 Packet network 30 TDM-PWE conversion apparatus 40 TDM Network 50 TDM network 101 TDM data termination unit 102 TDM data buffer unit 103 PWE information storage unit 104 Random timing generation unit 105 PWE header generation unit 106 Time stamp generation unit 107 PWE packet assembly transmission unit 301 Reception period extraction unit 302 PWE packet arrival monitoring Unit 303 correction unit 304 PWE packet reception decomposition unit 305 jitter buffer 306 TDM data extraction / output unit

Claims (9)

A communication apparatus having a function of receiving TDM (Time Division Multiplex) data and transmitting a PWE (Pseudo Wire Emulsion) packet, and a function of receiving a PWE packet and transmitting TDM data.
Random timing generation means for generating a transmission timing of a PWE packet to be transmitted next by changing from a reference value;
PWE packet generation and transmission means for generating the PWE packet having the header including the transmission timing and the received TDM data and transmitting the generated packet to a packet network;
PWE packet receiving means for receiving the PWE packet from the packet network and extracting the transmission timing information;
PWE packet holding means for holding the PWE packet;
TDM data extraction output for extracting the TDM data from the PWE packet held in the PWE packet holding means and outputting the TDM data to a TDM network at a predetermined cycle using a clock generated from the transmission timing information Means,
A communication apparatus comprising:   2. The communication apparatus according to claim 1, further comprising PWE information storage means for storing PWE information for generating a PWE packet, wherein the random timing generation means generates the transmission timing based on the PWE information.   The communication apparatus according to claim 2, wherein the transmission timing is set within a certain range with respect to a transmission cycle based on the number of TDM data frames included in the PWE information.   4. The communication apparatus according to claim 1, wherein the PWE packet generation / transmission unit transmits the PWE packet according to the transmission timing generated by the random timing generation unit. 5.   The PWE packet arrival monitoring means for monitoring the arrival of the next PWE packet based on the transmission timing information extracted by the PWE packet receiving means, according to any one of claims 1 to 4, The communication device described. 6. The method according to claim 3, wherein the predetermined period in which the ТDM data extraction / output unit outputs the ТDM data is the transmission period based on the number of ТDM data frames included in one PWE packet. The communication device described.
  6. The communication apparatus according to claim 5, further comprising correction means for correcting a delay time from the arrival timing of the PWE packet based on the transmission timing information. A communication device having a function of receiving TDM data and transmitting a PWE packet,
Random timing generation means for generating a transmission timing of a PWE packet to be transmitted next by changing from a reference value;
PWE packet generation and transmission means for generating a PWE packet having a header including the transmission timing and the received TDM data and transmitting the packet to a packet network;
A communication apparatus comprising: A communication device having a function of receiving a PWE packet and transmitting TDM data,
PWE packet receiving means for receiving information on the amount of change from a reference value for the transmission timing of the PWE packet received from the packet network and then receiving the PWE packet ;
PWE packet holding means for holding the PWE packet;
The TDM data is extracted from the PWE packet held in the PWE packet holding means, and the TDM data is output to the TDM network at a predetermined cycle by using a clock generated from the change amount information of the transmission timing. TDM data extraction and output means;
A communication apparatus comprising:

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