Abstract:
Provided is an apparatus that enables improvement of efficiency of up/downstream packet tensception by reflecting a plurality of variables of packet transmission, such as a temporal variety of packet lengths, asymmetry of downstream and upstream traffics, and an instantaneous burst of a traffic amount, on a loop-back-based WDM-PON. The apparatus includes: a downstream code sensor sensing an idle code from a downstream data frame to be transmitted to an optical network terminal (ONT); a trailer transmission controller receiving an idle code sensing signal from the downstream code sensor and forming a trailer of the downstream data frame (hereinafter, a downstream trailer) by adding overhead for a reception control of the downstream data frame by the ONT and a transmission control of an upstream data frame to be loop-back-transmitted from the ONT; an upstream code sensor receiving and sensing a trailer of the loop-back-transmitted upstream data frame (hereinafter, an upstream trailer); and a trailer reception controller receiving overhead information, which is added by the ONT, for a reception control of the upstream data frame from the upstream code sensor and controlling a reception of the upstream data frame.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application claims the priority of Korean Patent Application No. 2003-89359, filed on Dec. 10, 2003, and No. 2004-89722, filed on Nov. 5, 2004 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.  
         [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a wavelength division multiplexing-passive optical network (WDM-PON)-based packet transceiver, and more particularly, to an apparatus that can improve the efficiency of up/downstream packet transceiving by reflecting a plurality of variables of packet transmission, such as a packet lengths, asymmetry of downstream and upstream traffics, and an instantaneous burst of a traffic amount, on a WDM-PON in which a light source is not used in an optical network terminal (ONT), so called a loop-back based WDM-PON.  
         [0004]     2. Description of the Related Art  
         [0005]     Since a loop-back based ONT (LB-ONT) in a WDM-PON is an ONT, which does not require a light source to which a wavelength is designated, there exist advantages in terms of manufacturing, management, and installation of products. However, since the ONT must use downstream light as upstream light by loop-backing the downstream light in the ONT, upstream information and downstream information must be distinguished.  
         [0006]     Two methods for a loop-back based WDM-PON using downstream light as upstream light have been suggested.  
         [0007]     First, there is an interleave method of arranging upstream information and downstream information not to be temporally overlapped. The interleave method is divided into a packet interleave method of arranging upstream packets and downstream packets to temporally cross and a bit interleave method of alternatively arranging upstream bits and downstream bits.  
         [0008]     Second, there is a superposed modulation method of transmitting a downstream optical signal to an ONT by making the modulation depth of the downstream optical signal low and modulating the downstream optical signal with upstream information after making a modulated optical power uniform to some degree by amplifying the modulated optical power in a saturated-gain region. Or by making the modulation depth of the the upstream optical signal high and extracting upstream information in an OLT receiver regardless of the low modulated downstream optical signal by modulating upstream data using the downstream optical signal.  
         [0009]     Problems of the methods described above are as follows.  
         [0010]     1) Packet and bit interleave methods 
        Packet or bit interleave synchronization between an OLT and an ONT is necessary.     Can be difficultly applied to packets having variable lengths, and segmentation assembly and reassembly (SAR) for the packet interleave is required.     When asymmetry between a downstream and an upstream is greater, a waste of bandwidth is more increased.        
 
         [0014]     2) Superposed modulation method 
        Since a modulation depth of a downstream optical signal is low or since a modulation depth of an upstream optical signal is high, error occurrence possibility is high.     A modulation depth of a downstream optical signal must be adjusted according to a distance between an OLT and an ONT, and it is difficult to change a distance between subscribers.     In order to amplify an optical power modulated by an ONT in a saturated-gain region, expensive devices, such as a preamplifier, a semiconductor optical amplifier (SOA), and an external optical modulator, are necessary.        
 
       SUMMARY OF THE INVENTION  
       [0018]     The present invention provides a packet transceiver having high efficiency of up/downstream packet transceiving by reflecting a plurality of variables of packet transmission, such as packet lengths, asymmetry of downstream and upstream traffics, and an instantaneous burst of a traffic amount, on a WDM-PON.  
         [0019]     According to an aspect of the present invention, there is provided a first apparatus for transceiving packets in a WDM-PON, the apparatus comprising: a downstream code perceiving part perceiving an idle code from a downstream data frame to be transmitted to an optical network terminal (ONT); a trailer transmitting control part receiving an idle code perceiving signal from the downstream code perceiving part and forming a downstream trailer of the downstream data frame by adding an overhead for a reception control of the downstream data frame by the ONT and a transmission control of an upstream data frame to be loop-back transmitted from the ONT; an upstream code perceiving part receiving and perceiving an upstream trailer of the loop-back transmitted upstream data frame; and a trailer receiving control part controlling a receiving of the upstream data frame after receiving overhead information, which is added by the ONT, for a receiving control of the upstream data frame from the upstream code perceiving part.  
         [0020]     According to another aspect of the present invention, there is provided a second apparatus for transceiving packets in a WDM-PON, the apparatus comprising: a downstream code perceiving part receiving and perceiving a downstream trailer, to which overhead for a receiving control of a downstream data frame transmitted from an optical line terminal (OLT) is added; a trailer receiving control part receiving a perceiving signal of the downstream trailer from the downstream code perceiving part and controlling a receiving of the downstream data frame; a TS processing part analyzing trailer size (TS) information of an upstream data frame to be loop-back-transmitted to the OLT by receiving the perceiving signal of the downstream trailer from the downstream code sensor; an upstream code perceiving part perceiving an idle code from the upstream data frame to be loop-back transmitted to the OLT; and a trailer transmission control part forming an upstream trailer by adding overhead for a transmission control of the upstream data frame after receiving an idle code perceiving signal from the upstream code perceiving part, a downstream trailer perceiving signal from the downstream code perceiving part, and the TS information from the TS processing part. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
         [0022]      FIG. 1  is a block diagram of a conventional LB-ONT;  
         [0023]      FIG. 2  illustrates a concept of a loop-back transmission method using the ONT of  FIG. 1 ;  
         [0024]      FIG. 3  illustrates a loop-back protocol for a dynamic control of upstream and downstream bandwidths;  
         [0025]      FIG. 4  illustrates a detailed configuration a data frame transmitted using the loop-back transmission method;  
         [0026]      FIG. 5  illustrates an event generated due to insertion of an overhead, which complies with a downstream packet format, when an OLT transmits a downstream packet (frame) to an ONT;  
         [0027]      FIG. 6  illustrates an event generated due to processing of the overhead, which complies with a downstream packet format, when an ONT receives a downstream packet (frame);  
         [0028]      FIG. 7  illustrates an event generated due to insertion of an overhead, which complies with an upstream packet format, when an ONT transmits a downstream packet (frame) to an OLT;  
         [0029]      FIG. 8  illustrates an event generated due to processing of the overhead, which complies with an upstream packet format, when an OLT receives an upstream packet (frame);  
         [0030]      FIG. 9A  illustrates a configuration of communication protocol layers installed in an OLT according to an embodiment of the present invention;  
         [0031]      FIG. 9B  is a detailed block diagram of a TCE included in the OLT illustrated in  FIG. 9A ;  
         [0032]      FIG. 10A  illustrates a configuration of communication protocol layers installed in an ONT according to an embodiment of the present invention; and  
         [0033]      FIG. 10B  is a detailed block diagram of a TCE included in the ONT illustrated in  FIG. 10A . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     Hereinafter, the present invention will now be described more fully with reference to the accompanying drawings, in which embodiments of the invention are shown. Like reference numbers are used to refer to like elements through at the drawings.  
         [0035]      FIG. 1  is a block diagram of a conventional LB-ONT.  
         [0036]     Referring to  FIG. 1 , in the ONT, a 1:2 optical coupler  10  distributes an optical power of a downstream optical signal to an optical receiver (ORx)  11  and a modulator  12 .  
         [0037]     The downstream optical signal input to the ORx  11  is converted to an electrical signal and input to a modulation timing control signal generator  13 . The modulation timing control signal generator  13  determines start timing and end timing for modulating upstream data by loop-backing the downstream optical signal and transmits a timing control signal corresponding to the timings to an upstream data driving controller  14 .  
         [0038]     The upstream data driving controller  14  outputs or does not output the upstream data to the modulator  12  in response to the timing control signal. The modulator  12  modulates the upstream data by receiving the downstream optical signal and transmits the modulated upstream optical signal to the OLT.  
         [0039]      FIG. 2  illustrates a concept of a loop-back transmission method using the ONT of  FIG. 1 .  
         [0040]     Referring to  FIG. 2 , a downstream data frame transmitted from the OLT to the ONT includes a downstream trailer having a downstream data packet and an upstream trailer in which an upstream data packet is going to be loaded. A unique trailer header is added to each trailer for identification of the upstream and downstream and a control required for transmission.  
         [0041]     Unlike the downstream trailer having meaningful data, the upstream trailer has unmodulated data, i.e., meaningless data, and the unmodulated data included in the upstream trailer is replaced by modulated upstream data to be transmitted to the OLT by being controlled by the modulation timing control signal generator  13 . The size of each trailer is automatically determined by the OLT according to a user request or a traffic status.  
         [0042]      FIG. 3  illustrates a loop-back protocol for a dynamic control of upstream and downstream bandwidths.  
         [0043]     Referring to  FIG. 3 , communication between an OLT and an ONT is performed using upstream and downstream trailers having a predetermined size in operation S 31 . When a bandwidth change is requested by a user, the ONT requests bandwidth adjustment of the OLT in operation S 32 . The OLT analyzes the bandwidth adjustment request in operation S 33  and transmits whether the adjustment request is granted or not to the ONT in operation S 34 . When the adjustment request is granted, communication between the OLT and the ONT is performed using a changed bandwidth in operation S 35 .  
         [0044]      FIG. 4  illustrates a detailed configuration a data frame transmitted using the loop-back transmission method. In  FIGS. 4 through 8 , stream blocks shown using the same color or symbol are all the same.  
         [0045]     Referring to  FIG. 4 , a downstream trailer  40  includes an idle set (ISET), a downstream trailer header (DSTH), a downstream payload. The ISET is inserted so that a receiver end, i.e., an ONT, can detect the bit period of(synchronize) a received packet. That is, the ISET is always inserted after a period A in which bit information does not exist so that the ONT can detect the bit period of a received packet. When a packet is transmitted via a network, the receiver can detect bit information only when the receiver senses an exact cycle of the transmitted packet. Since the bit information cannot be detected if bits are suddenly input to the receiver, an OLT inserts and transmits ISET which includes bits having a predetermined pattern to the receiver, i.e., the ONT so that the ONT can detect the bit period.  
         [0046]     The DSTH is a specific pattern used to indicate a beginning point of downstream data. For example, one of 500 code groups that are not used among the 10B (802.3z) code groups can be selected for the DSTH. As described in  FIG. 2 , a downstream trailer transmitted from an OLT to an ONT is feedbacked with an upstream trailer transmitted from the ONT to the OLT according to features of the loop-back transmission method. Therefore, a main purpose of the DSTH is to remove the feedbacked downstream trailer by distinguishing the downstream trailer from the upstream trailer.  
         [0047]     Data to be transmitted from the OLT to the ONT, i.e., data to be actually provided to a user, is carried on the downstream payload.  
         [0048]     An upstream trailer  41  includes an upstream trailer header (USTH), a front gap (FGAP), an ISET, an upstream payload, an upstream trailer end (USTE), and a rear gap (RGAP). The USTH is a specific pattern used to indicate a beginning point of upstream data. For example, one of  499  code groups except the code group used for the DSTH among the  1  OB ( 802 . 3 z) code groups that are not used can be selected for the USTH. The USTH is used to provide the beginning point for carrying data on the upstream trailer  41  to be transmitted from the ONT to the OLT and used for the OLT to distinguish the upstream trailer  41  from signals received to the OLT.  
         [0049]     The FGAP is a time taking for operations that an ONT receiving processing unit detects the USTH from a downstream frame and requests an ONT transmission processing unit to load upstream data on the upstream trailer  41  and that the ONT transmission processing unit loads upstream data on the upstream trailer  41  in response to the request. The FGAP varies according to ONT systems. The ISET is inserted so that an OLT receiving processing unit can detect the bit period of the upstream data packet since bit information does not exist for the FGAP duration.  
         [0050]     Data to be transmitted from the ONT to the OLT, i.e., data requested by a user, is carried on the upstream payload. The USTE indicates the end of the upstream trailer  41 , and the OLT receiving processing unit recognizes an end point of the upstream trailer  41  by detecting the USTE. The RGAP is inserted to prevent the upstream trailer  41  from being overlapped with a subsequent downstream trailer.  
         [0051]     Trailers are repeated in a predetermined cycle, the cycle of  2 msec illustrated in  FIG. 4  is only an example. In the present embodiment, by controlling frequencies and locations of trailer headers, up/downstream bandwidths can be controlled according to transmission amounts, and a cycle of trailers can be flexibly and easily changed.  
         [0052]     Overhead, such as DSTH, ISET, RGAP, USTE, FGAP and USTH, used to support the loop back protocol (LBP) transmission method is, for example, calculated as follows: 
        Overhead=DSTH(20 bits)+ISET(1000 bits)+RGAP+USTE(20 bits)+ISET(1000 bits)+FGAP+USTH(40 bits)=2100 bits+200 bits(80 nsec assumed for FGAP and RGAP)=2280 bits        
 
         [0054]     Overhead/cycle=[2280/(1.25*10 9 *2*10 −3 )]*100=0.046%  
         [0055]     Therefore, the overhead per cycle is less than 0.1%, i.e., very little.  
         [0056]      FIG. 5  illustrates an event generated with insertion of overhead, which complies with a downstream packet format, when an OLT transmits a downstream packet (frame) to an ONT.  FIG. 9A  will be quoted for convenience of understanding.  
         [0057]     The OLT allows an ISET to be transmitted to a trailer control engine (TCE)  941  by turning off a switch  911  of a media access control (MAC) control part  91  and turning on a driver switch  961  in operation S 51 .  
         [0058]     The TCE  941  counts idle code bits, e.g., 1000 bits, and then starts inserting a DSTH in operation S 52 . Here, the counted number is the number of bits of the ISET.  
         [0059]     After inserting the DSTH, the OLT turns on the switch  911  of the MAC control part  91  and then commands the TCE  941  to start inserting a user service data unit (SDU) into a downstream payload in operation S 53 .  
         [0060]     Before a USTH is inserted, the TCE  941  cuts off the SDU transmission by turning off the switch  911  of the MAC control part  91  in order to prevent a frame loss and inserts the USTH in operation S 54 .  
         [0061]     After inserting the USTH, the TCE  941  turns off the driver switch  961  after waiting for a guard time in order to guarantee for the USTH to pass through an transmitter end (OTx) of the OLT in operation S 55 .  
         [0062]     The TCE  941  calculates a region in which upstream data is loaded by counting the idle code bits in operation S 56 .  
         [0063]     Operations  51  through  56  are repeated in operation S 57 .  
         [0064]      FIG. 6  illustrates an event generated with processing of the overhead, which complies with a downstream packet format, when an ONT receives a downstream packet (frame).  FIG. 10A  will be quoted for convenience of understanding.  
         [0065]     A physical medium attachment (PMA)  105  of a receiving processing unit of the ONT takes a clock/code block sync using an idle ordered set in a resync mode in operation S 61 .  
         [0066]     A TCE  1041  of the receiving processing unit of the ONT checks that a physical coding sublayer (PCS)  103  is in a sync mode and then detects a DSTH in operation S 62 . The TCE  1041  substitutes the DSTH by an idle code so that the PMA  105  and the PCS  103  operate in the same mode in operation S 63 .  
         [0067]     The TCE  1041  makes both the PMA  105  and the PCS  103  operate in the resync mode by transmitting a USTH to the PCS  103  in operation S 64 .  
         [0068]      FIG. 7  illustrates an event generated with insertion of overhead, which complies with an upstream packet format, when an ONT transmits a downstream packet (frame) to an OLT.  FIG. 10A  will be quoted for convenience of understanding.  
         [0069]     The ONT prevents any signal from being transmitted by turning off a switch  1011  of a MAC control part  101  and a driver switch  1061  in operation S 71 .  
         [0070]     The TCE  1041  detects a USTH, calculates a trailer size (TS) from the USTH, and calculates a length of an upstream trailer in operation S 72 . The driver switch  1061  is maintained in an off state during a predetermined time (FGAP) after detecting the USTH in order to prevent a collision between an idle code to be inserted by the ONT and an idle code that may be attached next the USTH when an OLT inserts the USTH to transmit downstream data.  
         [0071]     The ONT inserts the idle code (ISET) into the upstream trailer by turning on the driver switch  1061  in operation S 73 .  
         [0072]     The TCE  1041  starts inserting data requested by a user into an upstream payload by turning on the switch  1011  in operation S 74 .  
         [0073]     Before a USTE is inserted into the upstream trailer, the TCE  1041  cuts off the SDU transmission by turning off the switch  1011  in order to prevent a frame loss and inserts the USTE into the upstream trailer in operation S 75 .  
         [0074]     After inserting the USTE into the upstream trailer, a predetermined time (RGAP) is required in order to guarantee for the USTE to pass through an transmitter end (OTx) of the ONT in operation S 76 .  
         [0075]     Operations  71  through  76  are repeated in operation S 77 .  
         [0076]      FIG. 8  illustrates an event generated with processing of the overhead, which complies with an upstream packet format, when an OLT receives an upstream packet (frame).  FIG. 9A  will be quoted for convenience of understanding.  
         [0077]     A receiving processing unit of the OLT operates in the resync mode in operation S 81 .  
         [0078]     After detecting a DSTH, a PMA  95  operates in the sync mode while a PCS  93  operates in the resync mode in operation S 82  (the resync mode, in which the PCS  93  considers the DSTH, which is not a standard code block, as a code validity fail and does not transfer user data to a MAC, is used to discard a downstream payload).  
         [0079]     The receiving processing unit of the OLT prevents the PCS  93  from operating in the sync mode due to an idle code included in the downstream payload by generating an error code next the DSTH and transmitting the error code to the PCS  93 . In other words, the receiving processing unit of the OLT maintains the PCS  93  to operate in the resync mode in operation S 83 .  
         [0080]     The receiving processing unit of the OLT stops generating the error code, changes the operation mode of PMA  95  to the resync mode in order to synchronize again by a subsequently received ISET, and then transmits data to the PCS  93  in operation S 84 .  
         [0081]     The PMA  95  and the PCS  93  operating in the resync mode receives upstream data in the sync mode by synchronizing again by the subsequently received ISET in operation S 85 .  
         [0082]     The receiving processing unit of the OLT makes the PMA  95  and the PCS  93  operate in the resync mode by transmitting a USTE to the PCS  93  in operation S 86 . Here, a upstream bandwidth in a next cycle can be determined using an arriving time of the USTE and a up length bit count.  
         [0083]      FIG. 9A  illustrates a configuration of communication protocol layers installed in an OLT according to an embodiment of the present invention.  
         [0084]     Referring to  9 A, the MAC controller  91  performs transferring data between an upper layer and a framing/deframing processing unit  92 , controlling data flows between the MAC and the upper layer, processing a MAC control protocol, and processing SDU transfer control.  
         [0085]     The framing/deframing processing unit  92  frames downstream data or deframes upstream data. In a WDM-PON, the framing/deframing processing unit  92  commonly frames downstream data or deframes upstream data according to the Ethernet standard.  
         [0086]     The PCS  93  performs an 8-bit/10-bit encoding/decoding, a code-group validity checking, and a PMA resynchronization.  
         [0087]     A trailer control part  94  is a part in which the present embodiment is realized, transmits and receives data to and from other layers via a ten bit interface (TBI), inserts a USTH/DSTH into an upstream/downstream frame, detects a USTH/DSTH/USTE from an upstream/downstream frame, and includes the TCE  941  corresponding to the present embodiment in order to realize the transmitting, receiving, inserting and detecting functions. Detailed functions of the TCE  941  will be described later.  
         [0088]     The PMA  95  transmits and receives physical signals, and optical sub-assembly (OSA) electronics  96  correspond to receiving/transmitting optical signals. Since detailed functions of the two elements are generally understood by those skilled in the art, description of the two elements are omitted.  
         [0089]      FIG. 9B  is a detailed block diagram of the TCE  941  included in the OLT illustrated in  FIG. 9A .  
         [0090]     Referring to  FIG. 9B , the TCE  941  is largely divided into a downstream processing part  9411  and an upstream processing part  9412 , and operations of the processing parts  9411  and  9412  will now be separately described.  
         [0091]     [Downstream Processing Part  9411 ] 
         [0092]     A downstream code perceiving part  94111  perceives an idle code by receiving downstream data from the PCS  93  and then transmits an idle code perceiving signal to an OLT trailer transmission control part  94112 . Here, a matching process is required before transmitting the idle code perceiving signal since headers of a trailer are composed of predetermined bit patterns and the bit patterns(codes) can be detected only when received codes must be matched with codes stored in downstream processing part  9411 .  
         [0093]     The OLT trailer transmission control part  94112  receives the idle code perceiving signal, outputs an on/off control signal of SDU transmission to the MAC control part  91 , and outputs an on/off control signal for controlling data received via a transmission line to the driver switch  961 . Also, the OLT trailer transmission control part  94112  transmits a USTH/DSTH swap control signal to a code swapping part  94114 .  
         [0094]     A USTH/DSTH code generation part  94113  generates a USTH/DSTH code in advance and transmits the USTH/DSTH code to the code swapping part  94114 . The code swapping part  94114  swaps the USTH/DSTH code for a K28.5 code by receiving the USTH/DSTH swap control signal from the OLT trailer transmission control part  94112 . After swapping, the code swapping part  94114  transmits the downstream data received from the PCS  93  to the PMA  95 , and the transmitted downstream data is transmitted to an ONT.  
         [0095]     [Upstream Processing Unit  9412 ] 
         [0096]     An upstream code perceiving part  94121  receives an upstream data frame from the PMA  95 , perceives an idles code, a USTH, a DSTH, and a USTE from an upstream trailer of the upstream data frame, and transmits an idle/USTH/DSTH/USTE perceiving signal to an OLT trailer receiving control part  94122 .  
         [0097]     The OLT trailer receiving control part  94122  receives the idle/USTH/DSTH/USTE perceiving signal, transmits an on/off control signal of SDU transmission to the MAC controller  91 , and receives a signal, which is for transferring sync fail information to the PMA  95 , from the PCS  93  in order to check an operation mode of the PCS  93  (in detail, whether the PCS  93  operates in the resync mode or in the sync mode). Also, the OLT trailer reception control part  94122  transmits a control signal, which is for determining an operation mode of the PMA  95  in the sync/resync mode, to the PMA  95  and an error code generation control signal to an error code generation part  94123 .  
         [0098]     The error code generation part  94123  receives the error code generation control signal, generates an error code (why the error code is generated is described in  FIG. 8 ), and transmits upstream data to the PCS  93 .  
         [0099]      FIG. 10A  illustrates a configuration of communication protocol layers installed in an ONT according to an embodiment of the present invention.  
         [0100]     Referring to  FIG. 10A , the MAC controller  101  performs transferring data between an upper layer and a framing/deframing processing unit  102 , controlling data flows between the framing/deframing processing unit  102  and the upper layer, and processing a MAC control protocol.  
         [0101]     The framing/deframing processing part  102  deframes downstream data or frames upstream data. Like the OLT of  FIG. 9A , the framing/deframing processing part  102  commonly deframes downstream data or frames upstream data according to the Ethernet standard.  
         [0102]     The PCS  103  performs an 8-bit/10-bit encoding/decoding, a code-group validity check, and a PCS resynchronization.  
         [0103]     Like the OLT in  FIGS. 9A and 9B , a trailer control part  104  is a core layer to realize the present embodiment, transmits and receives data to and from other layers via a TBI, inserts a USTE into an upstream frame, detects a USTH/DSTH from an upstream/downstream frame, and substitutes DSTH 10-bit data by the K28.5 code. Like the OLT of  FIG. 9A , the trailer control part  104  includes the TCE  1041 , and detailed functions of the TCE  1041  will be described later.  
         [0104]      FIG. 10B  is a detailed block diagram of a TCE included in the ONT illustrated in  FIG. 10A .  
         [0105]     Referring to  FIG. 10B , like in  FIG. 9B , the TCE  1041  is largely divided into an upstream processing unit  10411  and a downstream processing unit  10412 , and operations of the processing units  10411  and  10412  will now be separately described.  
         [0106]     [Upstream Processing Unit  10411 ] 
         [0107]     An upstream code perceiving part  104111  perceives an idle code by receiving upstream data from the PCS  93  and then transmits an idle code perceiving signal to an ONT trailer transmission controller  104112 .  
         [0108]     The ONT trailer transmission control part  104112  receives the idle code perceiving signal, outputs an on/off control signal of SDU transmission to the MAC controller  101 , and outputs an on/off control signal for controlling data received via a transmission line to the driver switch  1061 . Also, the ONT trailer transmission controller  104112  receives header information, such as a USTH and a DSTH, from a downstream code perceiving part  104121  and packet transmission timing information from a TS processing part  104122  and outputs a USTE code swapping control signal to a code swapping part  104114 .  
         [0109]     A USTE code generating part  104113  generates a USTE code in advance and outputs the USTE code to the code swapping part  104114 . The code swapping part  104114  swaps the USTE code for a K28.5 code by receiving the USTE code swapping control signal from the ONT trailer transmission control part  104112  and transmits the upstream data received from the PCS  103  to the PMA  105 .  
         [0110]     [Downstream Processing Part  10412 ] 
         [0111]     The downstream code perceiving part  104121  receives downstream data from the PMA  105 , perceives a USTH/DSTH code, and transmits a USTH/DSTH code perceiving signal to an ONT trailer receiving control part  104123 . Also, the downstream code perceiving part  104121  transmits the USTH/DSTH code perceiving signal to the ONT trailer transmission control part  104112 . Since packet transmission timing is controlled by header information and TS information extracted by the downstream processing unit  10412 ,. ONT trailer transmission control part  104112  and ONT trailer reception receiving control part  104123  must share the header information and TS information. The downstream code perceiving part  104121  also transmits the USTH/DSTH perceiving signal to the TS processing part  104122  in order to calculate a transmission time.  
         [0112]     The ONT trailer receiving control part  104123  receives sync fail information from the PCS  103  in order to check an operation mode of the PCS  103  (in detail, whether the PCS  103  operates in the resync mode or in the sync mode) and transmits a control signal to the PMA  105  in order to operate the PMA  105  in the sync/resync mode. Also, the ONT trailer receiving control part  104122  transmits a DSTH code swapping control signal to a code swapping part  104125 .  
         [0113]     The TS processing unit  104122  receives the USTH/DSTH code sensing signal from the downstream code perceiving part  104121 , analyzes the TS information, and transmits a transmission time control signal (setup length) to the ONT trailer transmission receiving control part  104112  of the upstream processing part  10411  and the ONT trailer reception controller  104123 .  
         [0114]     A DSTH code generating part  104124  generates a DSTH code and transmits the DSTH code to the code swapping part  104125 . The code swapping part  104125  receives the DSTH code swapping control signal from the ONT trailer receiving control part  104123 , swaps the DSTH code for the K28.5 code, and transmits the downstream data to the PCS  103 .  
         [0115]     As described above, according to embodiments of the present invention, by inserting unique patterns indicating durations in which downstream and upstream information is loaded and extracting or inserting downstream and upstream data using a method of recognizing the patterns, downstream and upstream bandwidths can be controlled in realtime in response to a user request or a traffic transmission situation as compared with conventional packet transmission technology, an impulsive traffic burst, a feature of Internet traffic, can be smoothly accommodated, and a bandwidth waste can be minimized due to an efficient bandwidth use.  
         [0116]     While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The preferred embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.