JP6592250B2 - Synchronous circuit - Google Patents

Description

  The present invention relates to a synchronization circuit in a communication system.

  Communication systems, particularly optical access networks, are mainly provided by PON (Passive Optical Network) systems. FIG. 1 shows a configuration example of the PON system. The PON system includes an ONU (Optical Network Unit) 91 installed in a home, an OSU (Optical Subscriber Unit) 92 installed in a station, and an optical fiber network 93 connecting the ONU 91 and one OSU 92. The ONU 91 transmits a bandwidth request and upstream data to the OSU 92. Uplink data received by the plurality of OSUs 92 is collected by the concentrator 94.

  The distance between the OSU 92 and the ONU 91 is in the range of about 0 km to 40 km. In ranging or discovery in which the distance between the OSU 92 and the ONU 91 is measured, there is a time during which the ONU 91 does not transmit upstream data in order to wait for arrival of an upstream frame for distance measurement from the ONU 91 whose distance is indefinite.

IEEE Std. 802.3av-2009, “Physical Layer Specifications and Management Parameters for 10 Gb / s Passive Optical Networks”, Oct. 2009 ITU-T Recommendation G. 983

  Normally, the OSUs 92 are asynchronous with each other, and therefore, the phase relationship between the bandwidth allocation periods between the OSUs 92 and / or the phase relationship during the period in which no uplink data is transmitted from the ONU 91 such as discovery and ranging between the OSUs 92 changes with time. For this reason, there is a problem that a phase in which uplink data is transmitted between the OSUs 92 coincides with each other, a queue that stays in the concentrator 94 is generated even when there is no congestion, and excessive delay is added in the concentrator 94.

  Therefore, an object of the present invention is to prevent the occurrence of a queue that stays in a concentrator during non-congestion.

  The OSUs are synchronized with each other so that the timing at which the upstream data arrives at the concentrator does not overlap between the OSUs.

Specifically, the synchronization circuit according to the present invention is a communication system in which uplink data from a subscriber-side device is transmitted to a station-side device, and the uplink data from a plurality of the station-side devices is concentrated by a concentrator. wherein from the station side device to the concentrator as the arrival timing of the uplink data do not overlap with each other, to each station side device that performs the bandwidth allocation of the subscriber unit, synchronized shifts for each of the station-side device .

  In the synchronization circuit according to the present invention, the station side device shifts the phase of the period for performing bandwidth allocation to the subscriber side device for each of the station side devices, so that the station side device transfers to the concentrator. The arrival timing of the uplink data may be shifted for each station side device.

  In the synchronization circuit according to the present invention, the subscriber-side device, such as discovery or ranging, shifts the phase of the period during which uplink data is not transmitted for each station-side device, thereby allowing the station-side device to the concentrator. The arrival timing of the uplink data may be shifted for each station side device.

In the synchronization circuit according to the present invention, the station side device shifts the phase, which is the starting point of the time when the station side device permits transmission to the subscriber side device, for each station side device, so that the concentrator You may shift the arrival timing of the said uplink data to an apparatus for every said station side apparatus.

  Specifically, a communication system according to the present invention is a communication system in which uplink data from a subscriber side is transmitted to a station-side device, and the uplink data from a plurality of the station-side devices is concentrated by a concentrator. The synchronization circuit according to the present invention is provided.

  The above inventions can be combined as much as possible.

  According to the present invention, since a plurality of OSUs are synchronized in a state in which the phase of the OSU bandwidth allocation is shifted for each OSU, it is possible to prevent the occurrence of a queue staying in the concentrator during non-congestion.

It is an example of a structure of a PON system. An example of the timing which transmits uplink data between OSUs is shown. An example of the timing at which the OSU transmits uplink data when the discovery / ranging period Pt is longer than the bandwidth allocation period Pr is shown. An example of the timing at which the OSU transmits uplink data when the discovery / ranging period Pt is shorter than the band allocation period Pr is shown. An example of timing at which the OSU transmits uplink data when the period of Tr and Ts cannot be separated is shown. 2 shows an example of phase shift synchronization according to the first embodiment. It is the 1st schematic diagram of traffic and queue length which arrives at a concentrator from OSU, (a) shows a comparative example and (b) shows an example. The maximum queue length for traffic arriving at the concentrator during non-congestion is shown. It is the 2nd schematic diagram of the traffic and queue length which arrives at a concentrator from OSU, (a) shows a comparative example and (b) shows an Example. The example of the phase shift synchronization which concerns on Embodiment 2 is shown. The maximum queue length for traffic arriving at the concentrator during non-congestion is shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. These embodiments are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

  The system of the embodiment is shown in FIG. The system according to this embodiment includes an ONU 91, an OSU 92, an optical fiber network 93 connecting the ONU 91 and the OSU 92, a concentrator 94, and a synchronization circuit (not shown) that shifts the phase between the OSU 92 and synchronizes with each other. . Here, a configuration in which a plurality of ONUs 91 are connected to each OSU 92 is shown, but the timing at which the ONU 91 transmits uplink data to the OSU 92 or the timing at which uplink data may arrive at the concentrator 94 or the ONU 91 transmits uplink data to the OSU 92 The ONU 91 connected to the OSU 92 may be a single number, or the OSU 92 connecting the single ONU 91 and the OSU 92 connecting the plurality of ONUs 91 may be used. It may be mixed.

  The synchronization circuit is disposed in any device capable of shifting the phase between the OSUs 92. For example, the synchronization circuit may be arranged in an independent device other than the OSU 92 and the line concentrator 94, may be arranged in a device constituted by the OSU 92 and the line concentrator 94, or on a board that accommodates a plurality of OSUs 92. May be arranged in any of the OSUs 92, or may be incorporated in the concentrator 94. Although it is desirable that the synchronization circuit synchronizes all the OSUs 92 connected to the same concentrator 94, the effect of the present invention can be obtained by synchronizing only some of the OSUs 92. Even if at least a plurality of OSUs 92 are accommodated in the same concentrator 94 and the OSUs 92 accommodated in the concentrator 94 are synchronized, the effect of the present invention can be obtained.

[Embodiment 1]
The invention according to the present embodiment shifts the phase of the period related to the bandwidth allocation of the OSU 92 to each OSU 92 so that the timings of the periods in which uplink data is not transmitted such as the bandwidth request period and the discovery / ranging period do not overlap with each other. To synchronize.

  FIG. 2 shows an example of timing for transmitting uplink data between the OSUs 92. The synchronization circuit according to the present embodiment synchronizes by shifting the phase between the OSUs 92 so that the timing at which the uplink data arrives at the concentrator 94 is not easily matched between the OSUs 92. Specifically, the bandwidth request period Tr in which the ONU 91 makes a bandwidth request to the OSU 92 or its period Pr, the period Td in which the ONU 91 does not transmit uplink data for discovery or ranging, or its period Pd, or the OSU 92 with respect to the ONU 91 The phases are synchronized with each other so that at least one of the start points Tt of the time during which transmission is permitted does not overlap between the OSUs 92. The synchronization circuit only shifts the phase and synchronizes between the OSUs 92 only in the period related to band allocation, and the synchronization circuit does not need to allocate the band of each ONU 91 individually.

  The phase shift between the OSUs 92 may be a phase shift of any one of the period Tr, the period Td, or the starting point Tt, or a combination thereof. Hereinafter, the phase shift amount Sr of the period Tr or its period Pr, the phase shift amount Sd of the period Td or its period Pd, and the phase shift amount St of the starting point Tt are referred to as a phase shift amount Sp.

  In the following, for simplicity, a period Td in which the ONU 91 does not transmit uplink data for discovery or ranging is referred to as a discovery ranging period Td, and a period of the discovery ranging period Td is referred to as a discovery ranging period Pd. The discovery and ranging period Td is, for example, a discovery or ranging window size. The discovery / ranging cycle Pd includes a period during which the ONU 91 does not transmit uplink data and a period during which uplink data is transmitted for discovery or ranging.

  The phase shift amount Sp of each OSU 92 is determined so that uplink data transmission is not easily matched between the OSUs 92 when there is no congestion. For example, the phase shift amount Sp between other OSUs 92 in which the phase of each OSU 92 is adjacent is determined using a function proportional to or inversely proportional to the number of ONUs 91 for each OSU 92 or the number of active ONUs 91. Here, weighting may be performed for each ONU 91. In this case, the phase shift amount Sp of each OSU 92 is, for example, a function proportional to or inversely proportional to the sum of values multiplied by the weights for each ONU 91.

  The proportional function is suitable when the amount of uplink data for each OSU 92 is assumed to be approximately proportional to the number of ONUs, the number of active ONUs 91, or the sum of weights. As for the phase shift amount Sp of each OSU 92, for example, the phase shift amount Sp with another OSU 92 in which the phase of each OSU 92 is adjacent is set to Td and Tr during which no uplink data is transmitted. By overlapping the period during which uplink data is not transmitted with a period during which another OSU 92 can transmit uplink data, the OSU 92 during the period during which uplink data can be transmitted has the effect of avoiding the collision of the timing of uplink data arriving at the concentrator. is there.

For example, the phase shift amount Sp of each OSU 92 is set as follows.
Sp = Sr = bandwidth allocation period Pr × (number of ONUs 91 accommodated in corresponding OSU 92) / (number of ONUs 91 accommodated in all OSUs 92) Expression (11)
Sp = Sr = Bandwidth allocation period Pr × (total sum of weights of ONUs 91 accommodated in corresponding OSU 92) / (total sum of weights of all ONUs 91 accommodated in all OSUs 92) Expression (12)
Sp = Sd = Discovery ranging period Pd ÷ {(Discovery ranging period Td of corresponding OSU 92) / (Total of discovery ranging period Td of all OSUs 92)} Expression (13)
Sp = Sd = Discovery and ranging period Td of OSU 92 Equation (14)
Sp = Sr = band request period Tr of OSU 92 (15)
Sp = Sd = OSU 92 discovery and ranging period Td + OSU 92 bandwidth request period Tr (16)

  When the bandwidth allocation period Pr and the discovery / ranging period Pd are different for each OSU 92, the bandwidth allocation period Pr, the discovery / ranging period Pt, or a period of a common multiple of these may be used.

  The synchronization accuracy of the synchronization circuit (accuracy accuracy of synchronization deviation between OSU 92 and OSU 92) is at least less than the period to be synchronized. When the synchronization circuit shifts the phase of the band request period Tr, the synchronization accuracy of the synchronization circuit has a lower limit of the length of the period constituting the band allocation period Pr. When the synchronization circuit performs phase shift of the discovery / ranging period Td, the synchronization accuracy of the synchronization circuit has a lower limit of the length of the period constituting the discovery / ranging period Pt.

The relationship between the discovery / ranging period Pt and the bandwidth allocation period Pr is arbitrary.
For example, the discovery / ranging period Pt may be longer than the band allocation period Pr. In this case, as shown in FIG. 3, a plurality of band allocation periods Pr are included in one discovery / ranging period Pt, and a band request period Tr and an uplink data transmission period Ts are included in each band allocation period Pr. .
For example, the discovery / ranging period Pt may be shorter than the band allocation period Pr. In this case, as shown in FIG. 4, the upstream data transmission period Ts of the band allocation period Pr includes a plurality of discovery / ranging periods Pd, and the ONU 91 for discovery or ranging is included in each of the discovery / ranging periods Pt. It includes a discovery / ranging period Td and an uplink data transmission period Ts, which are periods during which uplink data is not transmitted.
For example, the discovery / ranging period Pd and the band allocation period Pr may be the same. In this case, as shown in FIG. 2, the discovery / ranging period Td, the band request period Tr, and the uplink data transmission period Ts are included in the discovery / ranging period Pd and the band allocation period Pr.

  Further, the discovery / ranging period Td may not be included. In this case, the discovery / ranging period Td in FIG. 2 may disappear and the band allocation period Pr may not appear. For example, when the discovery / ranging period Td is eliminated, the discovery / ranging period Td may be extended by the data transmission period Ts or the bandwidth request period, or may be replaced with Tr or a period of nothing.

  Although Tr and Ts have been shown in an example that can be explicitly separated and set in the bandwidth allocation period, in the present embodiment relating to discovery and ranging, for example, as shown in FIG. Even if the period of Ts cannot be separated, the effect of this embodiment can be obtained.

  FIG. 6 shows an example of phase shift synchronization according to the present embodiment. In FIG. 6, the number of OSUs 92 per line concentrator 94 is four, the weights for each OSU 92 are equal, the ONU 91 transmits upstream data in the upstream direction within the upstream data transmission period Ts, and the allocated bandwidth is all The phase shift amount Sr is set to 1/4 of the band allocation period Pr.

  FIG. 7 shows a schematic diagram of the traffic arriving at the concentrator 94 from the OSU 92 and the queue length. Fig.7 (a) shows a comparative example and FIG.7 (b) shows an Example. When the phases for transmitting uplink data between the OSUs 92 match, as shown in FIG. 7A, traffic of 10 Gbit / s × 4 total 40 Gbit / s arrives at the concentrator 94 at the same time even during non-congestion. However, the traffic can be accumulated and the queue L3A can be extended. On the other hand, when the phase shift of the band allocation period Pr is performed for synchronization, as shown in FIG. 7B, traffic arriving from the OSU 92 to the concentrator 94 is dispersed and does not stay in the concentrator 94. Therefore, the expansion of the queue L3B can be prevented.

  FIG. 8 shows the maximum queue length for traffic arriving at the concentrator 94 when there is no congestion. L4A indicates a comparative example, and L4B indicates an example. Here, the link between the ONU 91 and the OSU 92 and the output of the concentrator 94 are 10 Gbit / s, the number of ONUs 91 per OSU 92 is 128, the time required for the bandwidth request per ONU 91 is 3 microseconds, and the bandwidth allocation period Pr is 1 mm. Seconds and others were the same as in FIG.

  As shown in FIG. 8, the queue length L4A when the phases match between the OSUs 92 is such that the queue staying in the concentrator 94 is extended even during non-congestion. On the other hand, the queue length L4B in the case of synchronizing by performing the phase shift of the band allocation period Pr does not match the phase of the transmission data between the OSUs 92, and it can be seen that queue expansion is suppressed. For this reason, in the invention according to the present embodiment, since the queue does not expand at the time of non-congestion, an excessive delay is not added by the concentrator 94 at the time of non-congestion.

  Note that FIG. 9 shows an example in which there is uplink traffic with only two OSUs 92 adjacent in phase instead of the four OSUs 92 in the setting of FIG. FIG. 9A shows a comparative example, and FIG. 9B shows an example. The number of OSUs 92 per concentrator 94 is two, the weighting for each OSU 92 is equal, the ONU 91 transmits upstream data just before the upstream data can be transmitted, and traffic is evenly distributed across all OSUs 92. It is assumed that the phase shift amount Sr is 1/4 of the band allocation period Pr.

  The queue length L5B in the case of synchronizing by performing the phase shift of the band allocation period Pr shown in FIG. 9B is longer than the queue length L3B in FIG. 7B, but transmits upstream data between the OSUs 92. It can be seen that the queue length L5A is reduced when the phases match.

  As described above, the description has been given focusing on the bandwidth allocation cycle Pr, but the same applies to the discovery / ranging cycle Pd when the bandwidth allocation cycle Pr and the discovery / ranging cycle Pd are combined.

  Further, in the simulations shown in FIGS. 7 and 9, an example is shown in which upstream data transmission is permitted in a front-end manner. However, upstream data transmission permission is acceptable as long as upstream data is difficult to collide during non-congestion. For example, the upstream data transmission permission may be backpacked or may be a pseudo-random number. In the case of pseudo-random numbers, it is preferable to use the same function for generating pseudo-random numbers between the OSUs 92 so that upstream data does not collide between the OSUs 92 when there is no congestion, and it is desirable to set the same value as the seed of the random numbers. .

  The communication system including the OSU 92 as the station side device and the ONU 91 as the subscriber side device has been described as an example. However, the station side device changes from the subscriber side device to the concentrator via the station side device. A communication system for transmitting data, a communication system for notifying the subscriber side device of the time at which data transmitted from the subscriber side device to the concentrator via the station side device may be communicated or not. Then, this embodiment of this application and embodiment shown below are not limited to the optical communication system containing OSU92 as a station side apparatus and ONU91 as a subscriber side apparatus.

  In addition, the bandwidth request period and the discovery ranging period have been described as examples in which the data transmitted from the subscriber side device to the concentrator via the station side device is not communicated. It may be a time during which data to be transmitted to the concentrator via the side device is not communicated, for example, a period for transmitting control or management related information terminated between the subscriber side device and the station side device such as OAM and OMCI. . The same applies to other embodiments of the present application.

[Embodiment 2]
The synchronization circuit according to this embodiment is configured so that the start point Tt of the time when the OSU 92 permits transmission to the ONU 91 is different for each OSU 92 so that the arrival timing of the upstream data from the OSU 92 to the concentrator 94 is difficult to match. The phases that are the starting points Tt of bandwidth allocation between the OSUs 92 are mutually shifted and synchronized.

  FIG. 10 shows an example of phase shift synchronization according to the present embodiment. The shift amount St of the starting point Tt is determined so that uplink data transmission is not easily matched between the OSUs 92 when there is no congestion. For example, the shift amount St of the starting point Tt is a function proportional or inversely proportional to the number of ONUs 91 for each OSU 92 or the number of active ONUs 91. In addition, the shift amount St of the starting point Tt is a function that is proportional or inversely proportional to the sum of values multiplied by the weights for each ONU 91.

  The proportional function is suitable when the amount of uplink data for each OSU 92 is assumed to be approximately proportional to the number of ONUs or the number of active ONUs or the sum of weights. The phase shift amount Sp between other OSUs 92 whose phases of each OSU 92 are adjacent to each other is a discovery / ranging period Td or a band request period Tr which is a period during which uplink data is not transmitted. By overlapping the period in which the uplink data is not transmitted and the period in which another OSU 92 can transmit the uplink data, the OSU 92 in the period in which the uplink data can be transmitted can avoid the collision of the timing of the uplink data arriving at the concentrator 94. effective.

In the present embodiment, the phase shift amount Sp of each OSU 92 is set as follows, for example.
Sp = St = Uplink data transmission period Ts × (number of ONUs 91 accommodated in corresponding OSU 92) / (number of ONUs 91 accommodated in all OSUs 92) Expression (21)
Sp = St = Uplink data transmission period Ts × (total sum of weights of ONUs 91 accommodated in corresponding OSU 92) / (total sum of weights of ONUs 91 accommodated in all OSUs 92) Expression (22)
Sp = St = OSU 92 discovery and ranging period Td Equation (23)
Sp = St = band request period Tr of OSU 92 (24)
Sp = St = Discovery and ranging period Td of OSU 92 + Band request period Tr of OSU 92 Equation (25)

Expression (24) is a case where the bandwidth request period Tr ≦ (uplink data transmission period Ts / number of OSUs 92).
Expression (25) is a case where the discovery / ranging period Td of the OSU 92 + the bandwidth request period Tr of the OSU 92 ≦ the uplink data transmission period Ts ÷ the number of OSUs 92.
Sp = St = OSU bandwidth request period,
When the bandwidth allocation period Pr and the discovery / ranging period Pd are different for each OSU 92, the bandwidth allocation period Pr, the discovery / ranging period Pt, or a period of a common multiple of these may be used. In that case, the left side of the inequality sign in parentheses is a common multiple.

  The synchronization accuracy of the synchronization circuit (accuracy accuracy of synchronization deviation between OSU 92 and OSU 92) is at least less than the period to be synchronized. When the synchronization circuit performs a phase shift of the band allocation period Pr, the synchronization accuracy of the synchronization circuit is limited to the length of the period constituting the band allocation period Pr. When the synchronization circuit shifts the phase of the discovery / ranging period Pd, the synchronization accuracy of the synchronization circuit is about the length of the period constituting the discovery / ranging period Pd.

  FIG. 10 shows an example of phase shift synchronization according to the present embodiment. In FIG. 10, the number of OSUs per line concentrator 94 is four, the weights for each OSU 92 are equal, and the OSU 92 permits transmission of upstream data to the ONU 91 from the start point Tt within the upstream data transmission period Ts, and traffic Are equal for all the OSUs 92, the start points of the bandwidth allocation periods Pr of all the OSUs 92 are synchronized at the same time, and the starting point Tt is phase-shifted by 1/4 the uplink data transmission period Ts included in the single bandwidth allocation period Pr. The phase shift amount St is set to ¼ of the data transmission period Ts.

  FIG. 11 shows the maximum queue length for traffic arriving at the concentrator 94 when there is no congestion. L7A indicates a comparative example, and L7B indicates an example. The maximum queue length with respect to the traffic amount arriving at the concentrator 94 up to 7.5 Gbit / s is shown. Here, the link between the ONU 91 and the OSU 92 and the output of the concentrator 94 are 10 Gbit / s, the number of ONUs 91 per OSU 92 is 128, the time required for the bandwidth request per ONU 91 is 3 microseconds, and the bandwidth allocation period Pr is 1 mm. Seconds and others were the same as in FIG.

  As shown in FIG. 11, the queue length L7A when the phases match between the OSUs 92 is such that the queue staying in the line concentrator 94 extends even during non-congestion. On the other hand, the queue length L7B in the case of synchronizing by performing the phase shift of the starting point Tt of the time permitted for transmission does not match the phase of the transmission data between the OSUs 92, and the expansion of the queue is suppressed. I understand that. For this reason, since the queue according to the present embodiment does not expand, an excessive delay is not added by the concentrator 94 up to 7.5 Gbit / s.

  Further, although the example of permitting upstream data transmission from the starting time Tt is shown as an example, the upstream data transmission permission is not limited as long as upstream data is difficult to collide at the time of non-congestion. For example, the upstream data transmission permission may be backpacked or may be a pseudo-random number. In the case of pseudo-random numbers, it is preferable to use the same function for generating pseudo-random numbers between the OSUs 92 so that upstream data does not collide between the OSUs 92 when there is no congestion, and it is desirable to set the same value as the seed of the random numbers. .

  In addition, although the synchronization is performed in such a manner that the phases of the band allocation periods Pr of the OSUs 92 are matched, the phase of the band allocation period Pr is also shifted, and the sum of the shift amount Sp and the shift amount Sp of the start point Tt of the time permitted for transmission. By shifting in the above, it is possible to permit transmission of uplink data that is difficult for uplink data to collide during non-congestion.

  The present invention can be applied to the information communication industry.

91: ONU
92: OSU
93: Optical fiber network 94: Concentrator

Claims (3)

In a communication system in which uplink data from a subscriber-side device is transmitted to a station-side device, and the uplink data from a plurality of the station-side devices is concentrated by a line concentrator,
Period of performing bandwidth allocation for each station side device that performs bandwidth allocation of the subordinate subscriber devices independently so that arrival timings of the uplink data from the station side device to the line concentrator do not overlap each other Is proportional to or inversely proportional to the sum of values obtained by multiplying the phase of each of the station side devices by a function proportional to or inversely proportional to the number of subscriber side devices or active subscriber side devices, or weighting for each subscriber side device. not performed the bandwidth allocation of the synchronized, or one prior Symbol subscriber unit to shift on the basis of the function, the shift amount corresponding to,
Synchronous circuit. In a communication system in which uplink data from a subscriber-side device is transmitted to a station-side device, and the uplink data from a plurality of the station-side devices is concentrated by a line concentrator,
For each station side device that independently performs bandwidth allocation of the subordinate subscriber devices so that the arrival timing of the uplink data from the station side device to the concentrator does not overlap each other, the station side device A function that is proportional or inversely proportional to the number of subscriber-side devices or the number of active subscriber-side devices for each station-side device, or the subscription shifted based on the shift amount corresponding function, the proportional or inversely proportional to the sum of the value obtained by multiplying the weighting of each shielding-side apparatus does not perform the bandwidth allocation in synchronization, or one prior Symbol subscriber unit,
Synchronous circuit. A communication system in which uplink data from a subscriber side is transmitted to a station side device, and the upstream data from a plurality of the station side devices is collected by a line concentrator,
The synchronization circuit according to claim 1 is provided.
Communications system.

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