KR20170129044A - Frame transmission method adjusting interval between frames based on a drift and ethernet passive optical network adopting the frame transmission method - Google Patents

Abstract

When OLT or ONU transmits a plurality of frames in parallel using a plurality of wavelengths, the OLT or ONU can adjust the time interval of outputting the plurality of frames so that the order of transmitting the plurality of frames is not changed. Therefore, the ONU or OLT receiving a plurality of frames can easily rearrange the order of the plurality of frames according to the order of receiving the frames. Therefore, an EPON using multiple wavelengths can be easily implemented without including additional information indicating the order of frames in the frames.

Description

TECHNICAL FIELD [0001] The present invention relates to an Ethernet passive optical network, and more particularly, to a frame transmission method and a frame transmission method for adjusting a frame interval based on a drift,

The present invention relates to an Ethernet passive optical network.

An Ethernet passive optical network (EPON) is an optical subscriber network in which devices connected to a network communicate using an Ethernet frame. The structure of the EPON may be a 1: N structure in which at least one optical network unit (ONU) is connected to one optical line terminal (OLT).

Recently, the optical network is applied to backhaul networks connecting the base station and the core network. As traffic is explosively increased, the bandwidth required by the subscriber and the base station is expected to increase. In addition, 10G-EPON, 1G-EPON and NG-EPON equipment are expected to coexist in the next generation optical network without changing the current optical distribution network (ODN).

The ONU and the OLT disposed in the EPON use only one wavelength and transmit the frame using Time Division Multiplexing (TDM). Due to chromatic dispersion and power dispersion of optical fibers, it has been reached to increase the transmission speed at one wavelength.

The present invention relates to a time-division multiplexing Ethernet passive optical network for transmitting frames as well as time division multiplexing (TDM) as well as wavelength division multiplexing (WDM) And method.

According to an embodiment of the present invention, there is provided a method for transmitting a plurality of frames to a device, the method comprising: determining a lane to which the plurality of frames are to be transmitted based on an identifier of the device; Determining a time point at which the plurality of frames are to be transmitted, considering a delay caused by a position of an idle bit and a parity bit in a frame of the frame.

The present invention can transmit frames in a WDM (Wavelength Division Multiplexing) as well as a time division multiplexing (TDM).

1 is a view briefly showing an EPON for transmitting and receiving a frame according to a frame transmission method according to an embodiment of the present invention.
2 is a block diagram of a physical coding sublayer (PCS) of an OLT and an upstream physical layer of an ONU that performs a frame transmission method according to an embodiment of the present invention.
3 is a diagram for explaining an operation of each of the IDLE eliminator and IDLE inserter of FIG. 2 to delete and insert idle bits; FIG.
4A to 4C show the case where the IDLE eliminator deletes the idle bits and the IDLE inserter adds the idle bits to each other.
FIG. 5 is a diagram illustrating a situation where a plurality of frames are multiplexed to a plurality of wavelengths in an EPON to which a frame transmission method according to an embodiment is applied.
6 is a flowchart illustrating an operation of an OLT or an ONU performing a frame transmission method according to an exemplary embodiment of the present invention.
FIG. 7 is a diagram for explaining a situation where a drift occurs as a position where an idle bit is removed and a position where an idle bit is added are changed.
FIG. 8 is a flowchart illustrating an operation of a frame transmission by an OLT and an ONU performing a frame transmission method according to another embodiment of the present invention.

It is to be understood that the specific structural or functional descriptions of embodiments of the present invention disclosed herein are presented for the purpose of describing embodiments only in accordance with the concepts of the present invention, May be embodied in various forms and are not limited to the embodiments described herein.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. However, it is not intended to limit the embodiments according to the concepts of the present invention to the specific disclosure forms, but includes changes, equivalents, or alternatives falling within the spirit and scope of the present invention.

The terms first, second, or the like may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example without departing from the scope of the right according to the concept of the present invention, the first element being referred to as the second element, Similarly, the second component may also be referred to as the first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Expressions that describe the relationship between components, for example, "between" and "immediately" or "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms " comprises ", or " having ", and the like, are used to specify one or more of the features, numbers, steps, operations, elements, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, the scope of the patent application is not limited or limited by these embodiments. Like reference symbols in the drawings denote like elements.

1 is a view briefly showing an EPON for transmitting and receiving a frame according to a frame transmission method according to an embodiment of the present invention. 1, the EPON includes an OLT 110 and an ONU 120, and the OLT 110 and the ONU 120 can simultaneously transmit and receive a plurality of wavelengths according to a time-division multiplexing method.

The ONU 120 may transmit the optical signal upwardly or downwardly using one or more wavelengths. The number of wavelengths used by the ONU 120 can be determined by the maximum transmission rate of the optical signal. For example, if the EPON supports a transmission rate of 25 Gb / s per wavelength, a 25 G ONU can use one wavelength, a 50 G ONU can use two wavelengths, and a 100 G ONU can use four wavelengths. Hereinafter, it is assumed that the ONU 120 is a 100G ONU using wavelengths? 0 to? 3.

When the OLT 110 receives a frame having a transmission rate of 100 Gb / s from the external metro network, the OLT 110 performs a multiplexing process of distributing a frame to four wavelengths when transmitting a frame received by the 100 G ONU can do. The OLT 110 can transmit the frame to the ONU 120 through the optical cable using the four wavelengths distributed. 1, the OLT 110 divides a frame having a transmission rate of 100 Gb / s in the order of frame 1 (131) to frame 4 (134), and then transmits the frames Frame 1 (131) to frame 4 (134). Accordingly, the OLT 110 can efficiently transmit frames by distributing the frames to a plurality of wavelengths having a high transmission rate. That is, a frame having a high transmission rate can be multiplexed and transmitted at a plurality of wavelengths.

The ONU 120 can receive the frame 1 (131) to the frame 4 (134) by performing a demultiplexing process. The ONU 120 can recover a frame having a transmission rate of 100 Gb / s received from the OLT 110 from the frame 1 (131) to the frame 4 (134). In other words, the ONU 120 can demultiplex the frame according to the order in which the frames are received. It is very important that the order of the frames is not changed since the ONU 120 restores the frames according to the order in which the frame 1 131 to the frame 4 134 are received.

In a case where a plurality of frames having the same destination are transmitted using a plurality of wavelengths, the OLT 110 and the ONU 120 can adjust the arrival time of a plurality of frames to a destination. The time point at which each of the plurality of frames arrives at the destination may be determined according to the order of the plurality of frames. Referring to FIG. 1, the OLT 110 can allocate the frame 1 131 to the frame 4 134 as wavelengths that can output the fastest frames according to the order in which the frames are input. The ONU 120 can demultiplex the frame in the order in which the first bit of the frame arrives.

When a plurality of frames are transmitted using the wavelength division multiplexing scheme and the frames are demultiplexed according to the arrival order of a plurality of frames, the order of frames can be easily determined without displaying information relating to the order in the frames. That is, since only the arrival sequence of the frame is considered when demultiplexing the frame, the frame can be processed at a high speed.

Frames 131 to 4 (see FIG. 1) are multiplexed until a plurality of frames (frame 1 131 to frame 4 134 in FIG. 1) are multiplexed and arrive at a destination (ONU 120 in FIG. 1) 134) need to be maintained. A transmission delay can be generated in the physical layer of the OLT 110 in the process of the OLT 110 outputting the frame 1 (131) to the frame 4 (134). In particular, the transmission delay occurring in the physical layer may be different for each lane, which is a path classified by wavelength as a path for processing a signal. If the transmission delay is different for each lane, the transmission start time, which is the time at which transmission of the frame 1 (131) to the frame 4 (134) starts, may be different from the order of the frames. In this case, the ONU 120 can not correctly recover the data from the frame 1 (131) to the frame 4 (134).

The OLT 110 and the ONU 120 can determine a transmission start time of a frame in consideration of a transmission delay generated for each lane. Referring to FIG. 1, in consideration of a transmission delay occurring in lane 0 to lane 3 corresponding to each of lambda 0 to lambda 3, OLT 110 determines the order of frames in lane to which frame 1 131 to frame 4 134 are allocated It is possible to determine the transmission start time of each of the frames 1 (131) to 4 (134). Referring to FIG. 1, the transmission start times of the frames 1 131 to 134 are different from each other, and the ONU 120 can receive frames in the order of frame 1 131 to frame 4 134 . Accordingly, the ONU 120 can demultiplex the frames in the order of frame 1 (131) to frame 4 (134) to recover the data contained in frame 1 (131) to frame 4 (134).

2 is a block diagram of a Physical Coding Sublayer (PCS) of the downlink physical layer of the OLT 210 and the ONU 220 performing the frame transmission method according to an embodiment of the present invention.

2, the OLT 210 and the ONU 220 may include an FEC encoder 212 or an FEC decoder that performs forward error correction (FEC) to increase optical transmission reliability. The FEC encoder 212 may combine parity bits for error correction with data transmitted from an upper layer. Since the FEC encoder 212 adds a parity bit, the transmission rate needs to be increased.

2, the OLT 210 can delete IDLE bits, which are meaningless information between frames, by the size of a parity bit to be added in the FEC encoder 212 using the IDLE eliminator 211. [ Therefore, even if parity for FEC is added, the transmission rate can be maintained. When the OLT 210 receives a plurality of frames, the IDLE eliminator 211 of the OLT 210 deletes the idle bits from the data including the plurality of frames, and the FEC encoder 212 deletes the positions of the deleted idle bits The parity bit can be added.

The ONU 220 can correct errors of a plurality of frames based on the parity bits included in the received frames, and then delete the parity bits using the FEC decoder. The IDLE inserter 221 of the ONU 220 may add the idle bit again considering the position of the deleted parity bit.

In summary, the IDLE eliminator 211 of the OLT 210 may delete the idle bits of the length corresponding to the length of the parity bit. The IDLE inserter 221 of the ONU 220 may insert the idle bit into the deleted space in order to compensate for the space where the parity bits used for the FEC are deleted. That is, the IDLE inserter 221 can recover the combined data of a plurality of frames before passing through the FEC encoder 212 of the OLT 210.

For data in which a plurality of frames and idle bits are combined, the IDLE eliminator 211 can remove only idle bits present between a plurality of frames. The FEC encoder 212 may add a parity bit at a preset interval regardless of the position where the idle bit is removed. Therefore, the position where the idle bit is deleted and the position where the parity bit is added in the OLT 210 can be changed.

The IDLE inserter 221 of the ONU 220 may add an idle bit to an area between a plurality of frames. The position where the idle bit is added can be determined according to the position where the parity bit is inserted. The position where the idle bit is deleted in the OLT 210 and the position where the parity bit is added may be different from each other, Additional locations may also be different.

Drift is a phenomenon in which the transmission delay varies depending on lanes in frame transmission and data processing. The drift may be generated by changing the intervals of adjacent frames as the position where the idle bit is deleted in the IDLE eliminator 211 and the position where the idle bit is added in the IDLE inserter 221 are different. The OLT 210 and the ONU 220 performing the frame transmission method according to the embodiment can adjust the arrival order of the frames considering the drift. More specifically, the frame transmitter of the OLT 210 and the ONU 220 may determine a time to transmit a plurality of frames in consideration of a delay caused by positions of idle bits and parity bits of a plurality of frames.

3 is a diagram for explaining an operation of each of the IDLE remover 211 and the IDLE inserter 221 of FIG. 2 to delete and insert idle bits. Referring to FIG. 3, frames 1 to 4 output from the IDLE eliminator and frames 1 to 4 output from the IDLE inserter are shown with respect to time. Referring to FIG. 3, frames 1 to 4 to be distributed to a plurality of lanes or wavelengths can be sequentially inputted to the IDLE eliminator and the IDLE inserter in order. 3, the idle bit is shown as 'I'.

Referring to FIG. 3, the IDLE canceller may remove a portion 310 of the idle bits. The size of the portion to be removed may match the size of the parity bits added in the FEC encoder. Although the IDLE eliminator removes a certain portion 310 of the idle bits considering the size of the parity bits, the FEC encoder can add the parity bits at predetermined intervals regardless of the removed portion 310. [ Therefore, the position of the fixed portion 310 removed by the IDLE eliminator may be different from the position of the parity bit added by the FEC encoder. 3, it is assumed that the FEC encoder adds a parity bit to a certain portion 310 of the idle bits removed by the IDLE eliminator.

The position of the idle bit 320 added by the IDLE inserter may be the same as the position of the certain portion 310 since the position of the parity bit is added and the position of the certain portion 310 removed by the IDLE eliminator is the same. In this case, no drift occurs.

That is, the position where the idle bit is deleted in the OLT (or IDLE eliminator) (for example, a certain portion 310 in FIG. 3) and the position where the idle bit is added in the ONU (or IDLE inserter) 3 are always the same as in Fig. 3, no drift occurs. The OLT and the ONU according to the embodiment can predict whether drift occurs depending on whether the position where the idle bit is deleted and the position where the idle bit is added are different. If drift is expected to occur, the OLT and the ONU can determine the transmission start time of the frame in consideration of the transmission delay due to the drift.

4A to 4C show the case where the IDLE eliminator deletes the idle bits and the IDLE inserter adds the idle bits to each other. The idle bit is shown as 'I'. 4A, even if the IDLE eliminator of the transmitting OLT or ONU deletes a certain portion 410 of the idle bit between frame 3 and frame 4, the IDLE inserter of the receiving ONU or OLT is able to insert an IDLE inserter between frames 2 and 3 An idle bit 420 may be added. Referring to FIG. 4B, even though the IDLE eliminator on the transmitting side deletes a certain portion 411 of the idle bit between frame 2 and frame 3, the IDLE inserter on the receiving side has idle bit 421 between frame 3 and frame 4 Can be added. Referring to FIG. 4C, the IDLE eliminator on the transmitting side calculates a certain portion 412 of the idle bit between Frame 2 and Frame 3 and a certain portion 413 of the idle bit between Frame 3 and Frame 4 in consideration of the parity bit size , The receiver's IDLE inserter may add an idle bit 421 between frame 3 and frame 4.

As shown in FIGS. 4A to 4C, when the positions where the idle bits are removed from the transmitting-side OLT or the ONU and the positions where the idle bits are added by the receiving-side ONU or the OLT are different, a drift may occur. At this time, if the transmission OLT or the ONU multiplexes the frames 1 to 4 with a plurality of wavelengths, the transmission delay is different for each wavelength, and the order of outputting the first bit of the frames 1 to 4 is frame 1 to frame 4 ≪ / RTI >

As a result, when a propagation delay occurs due to a drift where a position where an idle bit is deleted in a channel or a lane corresponding to a specific wavelength and a position where an idle bit is added are different from each other, The order of the frames received via the channel may be different from the order of the frames transmitted. The transmission-side OLT or the ONU can adjust the transmission start time at which the output of a plurality of frames is started in consideration of the above-mentioned transmission delay. That is, the transmission-side OLT or the ONU can compensate the influence of the transmission delay on the transmission start time. Therefore, the receiving-side ONU or OLT can receive a plurality of frames in the same frame order as the original frame order, and can restore the data to be transmitted through a plurality of frames according to the order of the received frames.

FIG. 5 is a diagram illustrating a situation where a plurality of frames are multiplexed to a plurality of wavelengths in an EPON to which a frame transmission method according to an embodiment is applied. When two or more frames having the same LLID (Logical Link Identifier) are transmitted simultaneously in two or more lanes or in a frame interval smaller than the maximum drift size between frames, The interval between the frames output from the transmitting-side OLT or the ONU can be maintained to be equal to or larger than the drift, in order to prevent the case of being changed by the drift. For example, if the maximum drift size between the first frame and the second frame is 100 bytes and the difference between the first frame and the receiving time when the second frame arrives at the receiving side is expected to be 60 bytes, The second frame to be transmitted may be delayed by 40 bytes (100-60 bytes) from the transmission time of the first frame and then transmitted.

In the case of FIG. 5, it is assumed that the OLT transmits a frame to the ONU for convenience of explanation. It is assumed that the OLT can use four lanes (lanes 0 to 3). C_L0_s, C_L0_e, C_L0_LLID} for the lanes 0 (L0) to 3 (L3), the transmission start time Ln_s, the transmission end time Ln_e and the LLID of the frame being transmitted through the lane n {C_L1_s, C_L1_e, C_L1_LLID}, {C_L2_s, C_L2_e, C_L2_LLID}, {C_L3_s, C_L3_e, C_L3_LLID}. N_L0_s, N_L0_e, N_L0_LLID}, {N_L1_s, N_L1_e, N_L1_LLID} for the lanes 0 (L0) to lanes 3 (L3), the expected start time, end time and LLID when the frame is assigned to the lane n , {N_L2_s, N_L2_e, N_L2_LLID}, {N_L3_s, N_L3_e, N_L3_LLID}. The initial value of each variable may be all zero.

Hereinafter, it is assumed that the OLT transmits three frames to the ONU having LLID = 3. Assume that the OLT communicates with an ONU with LLID = 3 using lane 0 and lane 1. That is, the candidate lanes that can allocate three frames to be transmitted to the ONU in which the OLT is LLID = 3 are lane 0 and lane 1. Referring to FIG. 5, it is assumed that, among the three frames, frame 1 510 and frame 2 520 are allocated to lane 0 and lane 1, respectively, and are transmitted. The transmission start time, the transmission end time and the LLID of the frame 1 510 are {C_L0_s, C_L0_e, C_L0_LLID}, assuming that the transmission start time of the frame 1 510 allocated to the lane 0 is 100 and the transmission end time is 200, = {100, 200, 3}. The transmission start time, the transmission end time, and the LLID of the frame 2 520 are {C_L1_s, C_L1_e, C_L1_LLID}, assuming that the transmission start time of the frame 2 520 assigned to the lane 1 is 150 and the transmission end time is 300, = {150, 300, 3}.

The OLT can allocate frame 3 to either lane 0 or lane 1 when the OLT starts transmission of frame 3, which is the last frame among the three frames to be transmitted to the ONU with LLID = 3. It is assumed that the transmission time required for transmitting frame 3 is 150. The expected transmission start time of frame 3 should be set after the transmission end time (C_Ln_e) of the frame in which each lane is being transmitted. In addition, the expected transmission start time may be set to a value obtained by adding a certain value (alpha) to the transmission end time (C_Ln_e) to maintain a minimum frame interval. That is, when transmitting the frame 3 to the lane 0, the expected transmission start time N_L0_s of the frame 3 can be C_L0_e + α. That is, if N_L0_s and N_L1_s are the same, L1 is determined to have a higher lane number, and N_L1_s = CL1_e + α.

In the example of FIG. 5, it is assumed that alpha = 50. Therefore, when transmitting frame 3 to lane 0, the expected transmission start time of frame 3 is C_L0_e = 200 or later, and N_L0_s = 200 + alpha = 250. When transmitting frame 3 to lane 1, the expected transmission start time of frame 3 is a value after C_L1_e = 300, and N_L1_s = 350. The OLT can compare N_L0_s and N_L1_s and assign it to lane 0 that can output frame 3 first (ie, with a smaller N_Ln_s value). Therefore, the estimated transmission start time, estimated transmission end time, and LLIDs of the frame 3, {N_L0_s, N_L0_e, N_L0_LLID}, can be determined as {250, 400, 3}. The OLT can update {C_L0_s, C_L0_e, C_L0_LLID} based on the set {N_L0_s, N_L0_e, N_L0_LLID}.

The OLT can allocate the frame 3 to the lane 0 and adjust the transmission start time and the transmission end time of the frame 3 in consideration of the drift. The OLT can compare the difference between the start time (C_Ln_s) of the frame being transmitted and the transmission start time (N_Ln_s) of the frame 3 in the lanes other than the lane 0 to which the frame 3 is allocated. At this time, the OLT can perform comparison only for frames having the same LLID. Referring to FIG. 5, the OLT can compare the frame start time (C_L2_s = 150) of frame 2 520 of lane 1 with the transmission start time (N_L1_s = 250) of frame 3. N_L1_s - C_L2_s = 100.

The maximum value of the drift that can be generated in one lane may be 32 bytes, which is the size of the parity bit added in the FEC encoder. Thus, if drift occurs in two lanes, the difference in transmission delays between the two lanes can be 64 bytes, twice the size of 32 bytes. The OLT can determine the difference in transmission start time of frame 1 510, frame 2 520 and frame 3 to be at least twice the absolute value of the drift.

In this case, the order of frames received by the ONU may not be changed even if drift occurs depending on the position where the idle bit is removed from the OLT and the position where the idle bit is added in the ONU. 5, the transmission start time of the last frame (i.e., frame 2 520) of the current transmission frame and the transmission start time of the frame to be transmitted next (i.e., frame 3) are shifted by N_L1_s - C_L2_s = Is equal to or larger than twice the absolute value (i.e., 64), even if drift occurs, the ONU can receive frame 1 (510) to frame 3 in the order in which the OLT outputs.

If N_L1_s - C_L2_s = 20 and less than twice the drift absolute value (ie, 64), the OLT can increase the transmission start time of Frame 3 by the difference value 64 - 20 = 44 from D. In this case, the difference between the transmission start time of frame 3 and the transmission start time of frame 2 (520) may be twice the absolute value of the drift. The OLT can update C_L1_s by increasing the transmission start time of frame 3. [

In the example of FIG. 5, the OLT can compare the transmission start time of frame 2 520 of lane 1 with the transmission start time of frame 3. Assume that the OLT transmits frames to the ONUs using all of lanes 0 through lanes 3. It is also assumed that frame 1 'to frame 4' is being transmitted to each of lanes 0 to lanes 3, and the OLT has allocated frame 5 'to lane 0.

In this case, the OLT can compare the transmission start time of the frame 5 'with the transmission start time of the frame being transmitted in the lanes 1 to 3. That is, the difference value of the transmission start time to be compared by the OLT can be three in total. The OLT may find the smallest difference value and then add the difference between the smallest difference value and the maximum drift (D) between the lanes to the transmission start time of frame 5 '. For example, a difference value between the transmission start time of the frame being transmitted in the lane 1 and the transmission start time of the frame 5 'is 20, the difference value between the transmission start time of the frame being transmitted in the lane 2 and the transmission start time of the frame 5' 100, and the difference between the transmission start time of the frame being transmitted in the lane 3 and the transmission start time of the frame 5 'is 50, the OLT uses the smallest difference value of 20 as the transmission start time of the frame 5' 64) -20 = 44 at the transmission start time of frame 5 '. Therefore, C_L0_s of lane 0 can be updated to (N_L0_s + 44).

Hereinafter, the operation of determining the transmission start time of the frames 1 to 3 of the OLT of FIG. 5 will be described in more detail with reference to FIG. 6 is a flowchart illustrating an operation of an OLT or an ONU performing a frame transmission method according to an exemplary embodiment of the present invention.

Referring to FIG. 6, in step 610, the OLT or the ONU may determine a lane to which a plurality of frames are to be transmitted. The OLT or the ONU can use the identifier (e.g., LLID) of the ONU or OLT to receive the frame to determine the lane to which the frame is to be transmitted.

If the LLID of the frame is an LLID corresponding to a 25G ONU, the candidate lane to which the OLT or ONU can allocate a frame may be one. If the LLID of a frame is an LLID corresponding to a 50G ONU, the number of candidate lanes to which the OLT or ONU can allocate a frame may be two. If the LLID corresponds to a 100G ONU, the candidate lane may be four.

In step 620, the OLT or ONU may determine if the number of lanes that can transmit frames is two or more. When the number of lanes capable of transmitting a frame is two or more, the OLT or the ONU can simultaneously output a plurality of frames having the same LLID using wavelength division multiplexing. The OLT or the ONU can allocate a plurality of frames to a plurality of determined lanes in consideration of the order of a plurality of frames. Furthermore, the OLT or the ONU can adjust the transmission start time of each of the plurality of frames in consideration of a transmission delay (e.g., a transmission delay due to drift) generated for each lane.

In step 630, the OLT or the ONU may determine a transmission delay occurring for each lane in consideration of a system or a transmission link situation. That is, the OLT or the ONU can determine the maximum drift occurrence time or the drift interval D in advance. If the maximum drift interval between lanes is 64 bytes, D becomes 64 bytes. For each lane, the OLT or ONU can operate a time counter (TC) long enough to represent the absolute time.

In step 640, the OLT or ONU may assign a plurality of frames to a plurality of lanes. The OLT or the ONU can allocate a frame to the lane in consideration of whether or not the lane is currently in use. When the LLIDs of a plurality of frames are the same, the OLT or ONU can allocate a plurality of frames to lanes in consideration of the order of a plurality of frames. When a plurality of frames are sequentially allocated to a plurality of lanes, the OLT or the ONU can allocate a frame to a lane that can output the frame first. In this case, the expected transmission start time of each of the plurality of frames may be determined according to the minimum inter-frame interval.

In step 650, the OLT or ONU may determine the transmission start time of the plurality of frames. The transmission start time may be determined based on the drift interval. That is, the transmission start time of a plurality of frames may be determined such that a difference in transmission start time of a plurality of frames transmitted to an OLT or ONU having the same LLID is equal to or greater than a drift interval. Therefore, the transmission start time of the plurality of frames can be determined in consideration of the delay caused by the positions of the idle bits and the parity bits of the plurality of frames.

In step 660, the OLT or the ONU may transmit a plurality of frames in accordance with the determined transmission start time. That is, the interval at which a plurality of frames are output may be equal to or greater than the drift interval. Therefore, even if drift occurs, the order in which the frames are outputted may not be changed. An ONU or OLT receiving a plurality of frames can detect the order of a plurality of frames according to the order of receiving the first bit of the frame. Since the order of the frames is maintained, the ONU or the OLT can restore the data according to the order in which the frames are received.

According to another embodiment, the OLT or the ONU can prevent drift by matching the position where the idle bit is removed and the position where the idle bit is added. Since the drift is prevented, the order of the frames can be maintained. FIG. 7 is a diagram for explaining a situation where a drift occurs as a position where an idle bit is removed and a position where an idle bit is added are changed. Hereinafter, it is assumed that the OLT transmits frame 1 to frame 6 to the ONU.

Referring to Fig. 7, frames 1 to 6 processed in the PCS block of the OLT and the ONU are shown with time. Only the numbers of the frames 1 to 6 are shown in Fig. Referring to FIG. 7, the idle bit may be included between the frames 1 to 6 (a part where a separate number is not described). If frames 1 through 6 of the OLT are passed from the RS to the IDLE canceller, the IDLE canceller can remove certain parts 710 in the idle bits. Referring to FIG. 7, a drift may occur if the IDLE eliminator has a portion 710 where the idle bit is removed and a portion 720 where the IDLE inserter adds the idle bit is different. For example, if the idle bit following the n-th frame is removed and a parity bit is inserted midway or after the n-1 th frame, the IDLE inserter of the ONU may insert an idle bit after the n-1 th frame . In this case, drift may occur.

In the OLT and the ONU according to another embodiment of the present invention, if the idle bit following the n-th frame is removed and the parity bit is inserted in the middle or next of the n-th frame, an idle bit is added next to the n- . More specifically, the OLT and the ONU can synchronize the MAC control block with the beginning of the MAC, RS, and PCS blocks so that idle bits can be removed in consideration of the portion where parity bits are added.

Further, when the IDLE eliminator removes the idle bits by a size of the parity bit (for example, 32 bytes), the IDLE inserter divides the parity bits into 22 bytes by 10 bytes, Since bits are added at once, drift necessarily occurs. The OLT and the ONU can adjust the frame interval using the RS so that the idle bit can be removed in multiples of 32 bytes. Thus, a drift that may occur as the IDLE eliminator removes the idle bit below the parity bit size can be prevented.

FIG. 8 is a flowchart illustrating an operation of a frame transmission by an OLT and an ONU performing a frame transmission method according to another embodiment of the present invention.

In step 810, the OLT and the ONU can adjust the interval between the frames based on the data output per lane or the number of bytes of the idle bit by using the MAC control block. The OLT and the ONU can adjust the interval between the frames so that the size of the idle bits removed by the IDLE eliminator does not become less than the size of the parity bits.

In step 820, the OLT and the ONU may use the IDLE eliminator to remove the idle bits corresponding to the size of the parity bits. Therefore, the size of the idle bit to be removed may not be smaller than the size of the parity bit. The OLT and ONU can reset the data decoder and the FEC encoder to match the starting point. When the reset positions of the data decoder and the FEC encoder are matched, the position where the idle bit is removed and the position where the idle bit is added can be matched.

In sum, when the OLT or the ONU transmits a plurality of frames in parallel using a plurality of wavelengths, the OLT or the ONU can adjust the time interval during which a plurality of frames are outputted so that the order of transmitting the plurality of frames is not changed . Therefore, the ONU or OLT receiving a plurality of frames can easily rearrange the order of a plurality of frames according to the order of receiving the frames. Therefore, an EPON using multiple wavelengths can be easily implemented without including additional information indicating the order of frames in the frame.

The components described in the embodiments may be implemented by a programmable logic device such as one or more DSP (Digital Signal Processor), a processor, a controller, an application specific integrated circuit (ASIC), and a field programmable gate array Logic Element, other electronic devices, and combinations thereof. ≪ RTI ID = 0.0 > At least some of the functions or processes described in the embodiments may be implemented by software, and the software may be recorded in a recording medium. The components, functions and processes described in the embodiments may be implemented by a combination of hardware and software.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA) , A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

110: OLT
120: ONU
131: Frame 1
132: Frame 2
133: Frame 3
134: Frame 4

Claims (1)

Determining a lane to which to transmit the plurality of frames based on an identifier of the device when transmitting a plurality of frames to the device; And
Determining a time to transmit the plurality of frames in consideration of a delay caused by positions of idle bits and parity bits of the plurality of frames when the determined number of lanes is two or more
/ RTI >

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