JP6852957B2 - Subscriber side optical network unit - Google Patents

Description

The present disclosure relates to a band allocation technique in a passive optical network (PON).

A passive optical network (PON) is used to provide subscribers with high-speed access to the network. In the PON, one station-side optical network unit (OLT: Optical Line Thermal) is configured to accommodate a plurality of subscriber-side optical network units (ONU: Optical Network Unit) via a splitter or the like. Then, the OLT allocates resources to the ONU in the upward direction so that the signals transmitted by each ONU to the OLT do not collide.

Conventionally, in PON, resources are allocated by time division multiplexing (TDM: Time Division Multiplexing). That is, each ONU uses the same wavelength in the upstream direction, and the OLT allocates resources to each ONU by designating a transmission timing and a transmission period. However, in recent years, there has been a demand for expansion of the capacity of PON, and Non-Patent Document 1 describes TWDM (Time and Wavelength Division Multiplexing) in which TDM and wavelength division multiplexing (WDM) are applied to PON. It is disclosed. In TWDM-PON, the wavelength, transmission timing and transmission period used by the OLT for the ONU are specified.

As the speed of the radio access network provided by the mobile communication network increases, the area (cell) covered by the base station becomes narrower, and therefore the number of base stations to be installed in the mobile communication network increases. Therefore, the use of PON is being considered as a network for accommodating a plurality of base stations. Here, the delay request of the backhaul portion for accommodating the base station is stricter than the Internet access mainly provided by the PON, and in order to use the PON as the backhaul of the base station, the transmission in the PON is performed. The delay must be suppressed.

Therefore, Patent Document 1 discloses a configuration in which the ONU that can request a resource is limited based on the past resource request history of the ONU, and thereby the transmission delay caused by the transmission / reception of the control signal for resource allocation is suppressed. ..

Japanese Unexamined Patent Publication No. 2014-11660

Daisuke Iida, Shigeru Kuwano, Junichi Kaji, Jun Terada, "Improvement of Bandwidth Utilization Efficiency of Radio Access Network by Dynamic TWDM-PON Technology", 2013 IEICE Society Conference, B-8-35, September 2013

However, in the configuration described in Patent Document 1, when all ONUs require the same transmission band, the transmission delay cannot be suppressed.

The present invention is to provide a Subscriber-side optical termination unit of a passive optical access network that can suppress the transmission delay.

According to one aspect of the present invention, the subscriber-side optical network unit of the passive optical access network is a first subscriber-side optical network unit connected to a communication device that requires a predetermined delay condition for suppressing transmission delay. A holding means for holding information on whether the optical network unit is connected to a communication device that does not require the predetermined delay condition, and the information is the first subscriber optical network unit. When indicating that, it is controlled so that the request signal for requesting the resource is not transmitted to the station side optical network unit of the passive optical access network, and the information is the second subscriber side optical network unit. When the above is shown, the control means for controlling the request signal to be transmitted to the station-side optical network unit is provided, and the control means means that the information is the first subscriber-side optical network unit. When is indicated, when the allocation signal delivered by multicast from the station-side optical network unit is received and the resource is allocated, and the information indicates that the first subscriber-side optical network unit is used. The resource to be allocated is determined based on the number of the first subscriber-side optical network units connected to the station-side optical network unit.

The transmission delay of the passive optical access network can be suppressed.

The block diagram of the passive optical access network by one Embodiment. The block diagram of the station-side optical network unit according to one Embodiment. The block diagram of the subscriber side optical network unit according to one Embodiment. The figure which shows the resource allocation signal by one Embodiment. Communication sequence according to one embodiment.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In each of the following figures, components that are not necessary for the description of the embodiment will be omitted from the drawings. Further, the following embodiments are examples, and the present invention is not limited to the contents of the embodiments.

FIG. 1 is a configuration diagram of PON. One station-side optical network unit (OLT) 1 communicates with a plurality of subscriber-side optical network units (ONUs) 2 via a splitter 3. The PON of this embodiment is TWDM-PON, and wavelength multiplexing and time division multiplexing are used in combination. That is, the PON according to the present embodiment uses a plurality of wavelengths in each direction. Therefore, the OLT1 allocates resources used for data transmission in the upstream direction, that is, from the ONU2 to the OLT1 direction by designating the wavelength and the transmission period. In the following description, it is assumed that the signal for the OLT 1 to notify the ONU 2 of the resource is referred to as a resource allocation signal (Grant in the figure). Further, when the OLT1 allocates resources to the ONU2, the OLT1 acquires information about the amount of data that the ONU2 needs to transmit in the upward direction from each ONU2. In the following description, it is assumed that the signal for ONU2 to notify the OLT1 of the amount of transmitted data is referred to as a resource request signal (Report in the figure).

FIG. 5A is a conventional communication sequence diagram in TWDM-PON. Note that FIG. 5A shows a sequence in one wavelength pair among the plurality of wavelength pairs used in the TWDM-PON, and the m units of the ONU2s among the plurality of ONU2s accommodated in the OLT1 are shown. , It is assumed that this wavelength pair is configured to be transmitted and received. The wavelength pair means a pair of wavelengths in the up direction and the down direction. The OLT 1 transmits a resource allocation signal to each ONU 2 at a predetermined timing, and notifies each ONU 2 of the resources to be used. When each ONU2 receives the resource allocation signal, it transmits data and a resource request signal to OLT1 using the allocated resource. In this example, it is assumed that the same wavelength pair is assigned to the m units of ONU2 by the resource allocation signal. After transmitting the resource allocation signal, the OLT1 receives data and resource request signals from each ONU2, and after receiving all of them, allocates resources based on the resource request signals from each ONU2, and allocates each resource allocation signal. Send to ONU2. In the OLT1, data is transmitted in the downward direction, that is, in the ONU2 direction from the transmission of the resource allocation signal until the next resource allocation signal is transmitted.

FIG. 5B is a communication sequence diagram in TWDM-PON according to the present embodiment. Note that FIG. 5B shows a sequence for one wavelength pair among the plurality of wavelength pairs used in the TWDM-PON, and the m units of the ONU2s among the plurality of ONU2s accommodated in the OLT1 are the same. It shall be configured to transmit and receive wavelength pairs. Further, it is assumed that all of the m units of ONU2 are connected to a communication device that requires low delay. In the following description, ONU2 connected to a communication device that requires low delay will be referred to as low delay ONU2. In the present embodiment, each low-delay ONU2 is notified of a resource by multicasting one resource allocation signal. FIG. 4 shows a resource allocation signal according to the present embodiment. Further, the low delay ONU2 does not transmit the resource request signal, and the OLT1 allocates a predetermined band to the low delay ONU2 regardless of the resource request signal. This predetermined band can be, for example, a fixed value. Alternatively, this predetermined band can be a value obtained by evenly allocating the total upward band available at one wavelength to the low delay ONU2 to which the wavelength is assigned. The total band in the upward direction that can be used at one wavelength can be a predetermined value that is smaller than the entire band in the upward direction at the wavelength or the total band. Information for identifying which ONU2 is the low-delay ONU2 is set in the OLT1. In the present embodiment, the resource request signal is received from each ONU2, it is not necessary to aggregate the amount of data in the upstream direction of each ONU2, and the resource is notified by one resource allocation signal. It is possible to reduce the time from transmission of the resource allocation signal to the transmission of the resource allocation signal, and thus the transmission delay can be reduced.

It is also possible to mix low-delay ONU2 and other ONU2 at a certain wavelength. In this case, for the low-delay ONU2, the OLT1 evenly allocates a predetermined band among all the upward bands at one wavelength to the low-delay ONU2 to which the wavelength is assigned, and allocates the remaining band to the other ONU2. Reserve for. In this case, resources are allocated to the other ONU2s based on the resource request signal as in the conventional case. Further, for example, a configuration may be configured in which the low-delay ONU2 and the other ONU2 are accommodated so as not to be mixed at the same wavelength. In this case, the OLT1 can evenly allocate the entire upward band of the wavelength used only by the low-delay ONU2 to the low-delay ONU2 using the wavelength.

FIG. 2 is a configuration diagram of OLT 1 according to the present embodiment. In the present embodiment, the TWDM-PON uses _{n wavelengths of λ 1-1 to λ n-1 in the downward direction and n wavelengths of λ 1-2 to λ n-2} in the upward direction. Wavelength shall be used. Note that λ _k-1 and λ _k-2 (integers of k = 1 to n) are set as a wavelength pair in the down direction and the up direction. The OLT 1 in this embodiment includes n transmission / reception units 12-1 to 12-n. The transmission / reception unit 12-k (integer of k = 1 to n) performs transmission processing and reception processing of optical signals _{having wavelengths λ k-1} and λ _k-2. Under the control of the control unit 13, the selection unit 14 outputs the input data to the transmission / reception unit corresponding to the wavelength used by the ONU2, which is the destination of the data, in the downward direction. Further, the selection unit 14 outputs data received from each transmission / reception unit in the upstream direction. The control unit 13 holds information for identifying the low-delay ONU2 and other ONU2s, and allocates resources to each ONU2. The wavelength division multiplexing unit 11 outputs _{n wavelengths of wavelengths λ 1-1 to λ n-1} received from n transmission / reception units in the downlink direction by wavelength division multiplexing, and receives in the uplink direction. _{Signals having wavelengths λ 1-2 to λ n-2} included in the optical signal are separated and output to the corresponding transmission / reception unit 12.

FIG. 3 is a configuration diagram of ONU2 according to the present embodiment. The wavelength multiplexing unit 21 separates _{the wavelengths λ 1-1 to λ n-1} in the downward direction and the wavelengths λ _{1-2 to λ n-2 in} the upward direction. The wavelength tunable transmission / reception unit 24 is variable with respect to the transmission wavelength at least λ _{1-2 to λ n-2} , and is variable with respect to the reception wavelength at least with wavelengths λ _{1-1 to λ n-1} , and is used. The wavelength pair is controlled by the control unit 25. The tunable filter 23 _{outputs an optical signal having one of the wavelengths λ 1-1 to λ n-1 to} the tunable transmission / reception unit 24. The control unit 25 controls which wavelength of the optical signal is to be output. In FIG. 3, s is any value among integers 1 to n. The control unit 25 notifies the wavelength tunable transmission / reception unit 24 and the wavelength tunable filter 23 of the wavelength to be used based on the received band allocation signal. Further, the control unit 25 holds information indicating whether or not the own device is the low delay ONU2, and controls so as not to transmit the resource request signal when the own device is the low delay ONU2. On the other hand, when the own device is not the low delay ONU2, a resource request signal is transmitted and resource allocation is received.

Although the present embodiment has been described using TWDM-PON, the present invention can also be applied to TDM-PON that uses only time division multiplexing.

Claims (2)

It is a subscriber-side optical network unit of a passive optical access network.
The first subscriber side optical network unit connected to a communication device that requires a predetermined delay condition for suppressing the transmission delay, or the second subscriber side that is connected to a communication device that does not require the predetermined delay condition. A holding means for holding information on whether or not it is an optical network unit,
When the information indicates that the optical network unit is the first subscriber side optical network unit, the request signal for requesting a resource is controlled so as not to be transmitted to the station side optical network unit of the passive optical access network. When the information indicates that it is the second subscriber side optical network unit, the control means for controlling the request signal to be transmitted to the station side optical network unit and the control means.
With
When the control means indicates that the information is the first subscriber-side optical network unit, the control means receives an allocation signal multicast-distributed from the station-side optical network unit and receives resource allocation.
When the information indicates that it is the first subscriber side optical network unit, the resource to be allocated is based on the number of the first subscriber side optical network units connected to the station side optical network unit. A subscriber-side optical network unit, characterized in that it has been determined. The subscriber-side optical network unit according to claim 1 , wherein the request signal includes an amount of transmitted data.

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