Abstract:
An apparatus comprising a wavelength division multiplexer (WDM), an optical network unit (ONU) coupled to the WDM, a passive optical network (PON) data over cable service interface specification (DOCSIS) upstream proxy (PDUP) coupled to the ONU and configured to couple to a coaxial cable, and a downstream (DS) optical/electrical (O/E) converter coupled to the WDM and configured to couple to the coaxial cable. An apparatus comprising a WDM, an optical line terminal (OLT) coupled to the WDM, a cable model termination system (CMTS) coupled to the OLT via an upstream external physical (PHY) interface (UEPI), and a DOCSIS and a Quadrature Amplitude Modulation (QAM) unit coupled to the WDM and the CMTS.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application 61/246,032, filed Sep. 25, 2009 by Yuxin Dai, and entitled “PON DOCSIS Upstream Architecture over the Next Generation HFC Networks,” which is incorporated herein by reference as if reproduced in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND 
       [0004]    Hybrid fiber-coaxial (HFC) is a broadband network that is employed by cable Television (TV) operators and that combines optical fiber and coaxial cable technologies. The HFC comprises point-to-point (P2P) fiber that extends from an operators&#39; site, e.g. a headend or central office, to an optical node (ON), which serves a plurality of customers or customer premise equipment (CPE) via a coaxial plant that comprises branching coaxial cables. The headend comprises telephony equipment for providing telecommunications services, satellite dishes to receive distant video signals, and/or Internet Protocol (IP) aggregation routers. The services are encoded, modulated, up-converted onto Radio Frequency (RF) carriers, and/or combined onto an electrical signal and then forwarded using an optical transmitter from the headend to the ON. The optical transmitter converts the electrical signal to an optically modulated signal before sending the signal downstream to the ON via a fiber optic cable, e.g. in a P2P topology. The ON comprises an optical receiver, which converts the received optical signal from the headend to an electrical signal, which is then forwarded to the customers via the coaxial plant or coaxial cables. The ON also comprises a reverse/return path transmitter that sends communications from the customers to the headend. The reverse/return transmitter converts electrical signals from the customers into an optical signal, which is then forwarded upstream to the headend. 
       SUMMARY 
       [0005]    In one embodiment, the disclosure includes an apparatus comprising a wavelength division multiplexer (WDM), an optical network unit (ONU) coupled to the WDM, a passive optical network (PON) data over cable service interface specification (DOCSIS) upstream proxy (PDUP) coupled to the ONU and configured to couple to a coaxial cable, and a downstream (DS) optical/electrical (O/E) converter coupled to the WDM and configured to couple to the coaxial cable. 
         [0006]    In another embodiment, the disclosure includes an apparatus comprising a WDM, an optical line terminal (OLT) coupled to the WDM, a cable model termination system (CMTS) coupled to the OLT via an upstream external physical (PHY) interface (UEPI), and a DOCSIS and a Quadrature Amplitude Modulation (QAM) unit coupled to the WDM and the CMTS. 
         [0007]    In yet another embodiment, the disclosure includes an apparatus comprising at least one processor coupled to a memory and configured to receive an electrical burst signal from a plurality of customer equipment via a coaxial plant, wherein the electrical burst signal comprises a preamble and a plurality of DOCSIS media access control (MAC) frames, and wherein each of the DOCSIS MAC frames comprise a packet data unit (PDU), encapsulate the upstream burst in a payload portion of an Ethernet frame, and transmit the Ethernet frame upstream to an OLT on an optical carrier channel. 
         [0008]    These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
           [0010]      FIG. 1  is a schematic diagram of an embodiment of a standard HFC. 
           [0011]      FIG. 2  is a schematic diagram of an embodiment of a modified HFC. 
           [0012]      FIG. 3  is a schematic diagram of an embodiment of a PON DOCSIS upstream proxy architecture. 
           [0013]      FIG. 4  is a schematic diagram of an embodiment of a standard DOCSIS protocol stack. 
           [0014]      FIG. 5  is a schematic diagram of an embodiment of a modified DOCSIS protocol stack. 
           [0015]      FIG. 6  is a schematic diagram of an embodiment of a framing scheme. 
           [0016]      FIG. 7  is a flowchart of an embodiment of an upstream transmission method. 
           [0017]      FIG. 8  is a schematic diagram of an embodiment of a general-purpose computer system. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
         [0019]    A PON system may use QAM RF overlay to deliver broadcast video, which is often referred to as hybrid Internet Protocol (IP) television (IPTV). For example, Verizon&#39;s FIOS system uses a Hybrid IPTV architecture to deliver triple play services to customers, which may comprise bundled home communications services, such as television services, Internet, and/or telephone. The QAM video services may be delivered via a PON optical distribution network (ODN), e.g. using downstream optical signals at about 1550 nanometer (nm) wavelength. Additionally, the PON may deliver Internet data, Voice over IP (VoIP), and/or Video on Demand (VOD) services using a time division multiplexing (TDM) scheme. However, the hybrid IPTV architecture may be based on a PON topology, where each PON supports a limited quantity of users and that may be difficult to extend to more users. For example, each PON may not serve more than about 32 video end-users. As such, additional PONs may be needed to provide video services to more customers, which may increase cost for deployment and operational support. 
         [0020]      FIG. 1  shows a traditional or standard HFC  100  that may be typically used to provide QAM video services and Internet, VoIP, and/or VOD services to a plurality of customers, e.g. at residential locations. The HFC  100  may comprise a headend  110  and a plurality of ONs  120  that may be coupled to the headend  110  via a plurality of corresponding optical fiber cables  115  in a P2P topology. Each ON  120  may also be coupled to a plurality of customer equipment  130 , such as cable modems (CMs) and/or set-up boxes (STBs) via a plurality of corresponding coaxial plants  125 , e.g. at the residential locations. 
         [0021]    The headend  110  may be configured to modulate a video service in electrical signal format using QAM, e.g. at a RF carrier, convert the electric signal to an optical signal format and broadcast the optical signal downstream to the ONs  120  via the corresponding optical fiber cables  115 . Additionally, the headend  110  may transmit Internet and/or other IP services (e.g. data, video, and/or VoIP) to the ONs  120  via the optical fiber cables  115  using DOCSIS protocols. The QAM video service, Internet service, and/or other IP services may be transmitted from the headend  110  to the ONs  120  over a downstream wavelength channel, e.g. at about 1,550 nm (represented by the solid lines between the headend  110  and the ONs  120 ). 
         [0022]    The ONs  120  may be configured to receive the optical signals, converge them into corresponding electrical signals, and transmit the electrical signals into coaxial cable plants. Additionally, the ONs  120  may be configured to transmit upstream optical signals, which may comprise Internet, data, and/or other communications to the headend  110  via the corresponding optical fiber cables  115  on an upstream wavelength channel, e.g. at about 1,310 nm (represented by the dashed lines between the headend  110  and the ONs  120 ). 
         [0023]    The customer equipment, such as CMs and/or STBs, may be configured to receive the IP services, video services, and/or system control data, from the corresponding ON  120  via the coaxial plant  125  in electrical signal format. The CMs/STBs may demodulate or process the received electrical signal to provide the services to the customers or end-users that are associated with the customer equipment  130 . The CMs/STBs may also modulate and send data in the format of electrical signals from the customer equipment  130  to the ON  120  via the coaxial plant  125 . The data may correspond to uploaded Internet data, user requests, user settings, and/or system control data. 
         [0024]    Disclosed herein is a system and apparatus for improving the QAM RF video PON overlay (hybrid IPTV) architecture, e.g. to provide video and data services to more end-users, reduce system cost, or both. The system may use a PDUP architecture that may use a TDM PON scheme and may be based on a star or point-to-multipoint (P2MP) PON ODN topology. The PDUP architecture may combine the DOCSIS protocol and the TDM PON scheme to extend the coaxial plants to serve a greater number of end-users. As such, the DOCSIS protocol may be used for scheduling upstream transmissions from a plurality of CMs to the headend via TDM PON. 
         [0025]    The P2MP ODN in the PDUP architecture may deliver video services (e.g. QAM video services) to more end-users than standard Hybrid IPTV architectures that do not support coaxial plant extensions. The PDUP architecture may also provide more scalable RF return than standard HFC architectures and reduce the network deployment and operational cost, e.g. by supporting more end-users and/or services using a unified access network, e.g. PON, for multiple system operators (MSOs). Additionally, the system may use the DOCSIS protocol and substantially the full bandwidth, e.g. about five Gigabits per second (Gbps), of the coaxial plant from the ON to provide a combine platform for residential and business services for MSOs. 
         [0026]      FIG. 2  shows an embodiment of a next generation (NG) or improved HFC  200  that may be used to provide QAM video services and Internet, VoIP, and/or VOD services to a greater number of customers than the HFC  100 , e.g. at a lower deployment and operation cost. The HFC  200  may comprise a headend  210  and a plurality of ONs  220  that may be coupled to the headend  210  via a plurality of optical fiber cables  215  in a P2MP topology. Additionally, the HFC  200  may comprise a plurality of customer equipment  230  coupled to the ONs  220  via a plurality of corresponding coaxial plants  225 . The components of the HFC  200  may be configured to operate similar to the corresponding components of the HFC  100 , e.g. to send the video service, Internet service, and/or other services to the ONs  220  and the customer equipment  230  and transmit upstream communications from the customer equipment  230  and the ONs  220 . However, at least some of the components of the HFC  200  may be modified, as described in detail below, to support the extension of the QAM video services to a greater quantity of customer equipment in comparison to the standard HFC  100  at a lower system cost. The HFC  200  may also provide better use of the system&#39;s RF bandwidth capacity and combined residential and business services on a single platform, e.g. for MSOs. 
         [0027]    Based on the P2MP topology, the headend  210  may be coupled to the ONs  220  via a PON, which may comprise an OLT in the headend  210 , a plurality of ONUs in the ONs  220 , and an ODN between the headend  210  and the ONs  220 . The PON may be configured to implement a time division multiple access (TDMA) scheme for upstream communications, and as such the PON may be a Gigabit PON (GPON) as defined by the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T) G.984 standard or an Ethernet PON (EPON) as defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.3ah standard. Alternatively, the PON may be a Next Generation Access (NGA) system, such as a 10 Gbps GPON (XGPON), a 10 Gigabit EPON as defined by the IEEE 802.3av standard, an asynchronous transfer mode PON (APON), or a broadband PON (BPON) as defined by the ITU-T G.983 standard, all of which are incorporated herein by reference as if reproduced in their entirety. 
         [0028]    The ODN may comprise the optical fiber cables  215  and any combination of couplers, splitters, distributors, and/or other equipment. The optical fiber cables  215 , couplers, splitters, distributors, and/or other equipment may be passive optical components, e.g. which do not require any power to operate. Alternatively, the ODN may comprise one or a plurality of active components, such as optical amplifiers. 
         [0029]    The ODN may extend from the headend  210  to the ONs  220  in a star topology or branching configuration, e.g. using at least one splitter  218 , as shown in  FIG. 2 . For instance, the splitter  218  may couple about 32 ONs  220  to the headend  210 . Such P2MP topology may allow extending the quantity of ONs  220  and therefore the quantity of served customer equipment at a lower system cost that in the case of the P2P topology of the HFC  100 . However, in the modified HFC  200  the headend  210  may also be configured to transmit data, Internet and/or other services over a second downstream wavelength channel, e.g. at about 1,490 nm. In  FIG. 2 , the downstream channels are represented by solid lines and the upstream channels are represented by dashed lines between the headend  210  and the ONs  220 . The data in the second downstream wavelength channel may be sent in the ODN to the ONUs in the ONs  220 , which may act as distribution sites for the services, e.g. for the customer equipment  230 , business customers, and/or other customers. Thus, the HFC  200  may provide a single or common platform to provide residential services (e.g. by the customer equipment  230 ) and business services (e.g. by the ONUs at the ONs  220 ). Allocating the video service to a first downstream wavelength channel (e.g. at about 1,550 nm) and other data, Internet, and/or IP services to the second downstream wavelength channel (e.g. at about 1,490 nm) may provide greater bandwidth capacity for transporting the video service in the PON and with coaxial cable extensions may provide great numbers of more end-users than normal TDM PON and thus allow for better usage of the system&#39;s RF bandwidth capacity, e.g. at about five Gbps. Consequently, video service may be extended to more ONs  220  and more customer equipment  230  attached to the coaxial cable extension, e.g. about ten times more than the quantity of video end-users that can be supported using current TDM PON technologies. This may also result in providing more scalable RF return than standard HFC architectures in  FIG. 1 . 
         [0030]    The first downstream wavelength channel (e.g. at about 1,550 nm), the second downstream wavelength channel (e.g. at about 1,490 nm), and the upstream wavelength channel (e.g. at about 1,310 nm) for each ON  220  and their corresponding customer equipment  230  may be transported via the same optical fiber cable  215  (e.g. a trunk fiber) between the headend  210  and the splitter  218 , and therefore a mechanism may be needed to separate the different channels that correspond to the different ONs  220 . As such, the components of the HFC  200  may be configured based on a PDUP to process the upstream wavelength channels that correspond to different ONs  200  and their corresponding customer equipment  230  using the TDM scheme and the DOCSIS protocol, as described below. 
         [0031]      FIG. 3  shows an embodiment of a PDUP architecture  300 , which may be used for a NG HFC, such as the NG HFC  200 . Accordingly, the NG HFC may comprise a headend  310  that may be coupled to a plurality of ONs  320  via a plurality of optical fiber cables  315  in a P2MP topology, e.g. using a star or branching ODN configuration as described above. Although one ON  320  is shown in  FIG. 3 , the NG HFC may comprise any quantity of ONs  320 . The ONs  320  may also be coupled to a plurality of customer equipment  330  via a plurality of corresponding coaxial plants  325 . The components in the PDUP architecture  300  may be configured substantially similar to the components of the HFC  200 . Specifically, the headend  310  may comprise a DOCSIS and edge QAM (EQAM) unit  312 , a first splitter  313  (e.g. a WDM) coupled to the DOCSIS and QAM unit  312 , an OLT  314  coupled to the first splitter  313 , and a CMTS  316  coupled to the OLT  314  and the DOCSIS and EQAM unit  312 . The ON  320  may comprise a second splitter  321  (e.g. a WDM), an ONU  322  coupled to the second splitter  321 , a DS O/E converter  324  also coupled to the second splitter  321 , and a PDUP  326  coupled to the ONU  322  and the DS O/E converter  324 . 
         [0032]    The DOCSIS and EQAM unit  312  may be configured to modulate the video and data services using QAM and up-convert the video and data services on a RF carrier in electrical signal format. The DOCSIS and EQAM unit  312  may also comprise or may be coupled to an O/E signal converter (not shown) that may convert the electrical signal to an optical signal. Thus, the QAM video service may be transported from the DOCSIS and EQAM unit  312  to the multiplexer/demultiplexer  313  on an optical carrier, e.g. at about 1,550 nm, which may be broadcast to the ONs  320 . Additionally, the DOCSIS and EQAM unit  312  may use the DOCSIS protocol to support relatively high speed data transfer over the HFC infrastructure, e.g. to provide Internet access (e.g. cable internet) over a cable TV (CATV) system. The DOCSIS protocol may substantially increase transmissions speeds, e.g. for upstream and/or downstream channels, and may support IP transport, such as IP version 6 (IPv6). 
         [0033]    The OLT  314  may be part of the PON in the system and may be any device configured to communicate with the ONs  320  and optionally another network (not shown). The OLT  314  may act as an intermediary between the other network and the ONs  320 . For instance, the OLT  314  may forward data received from the network to the ONs  320 , and forward data received from the ONs  320  onto the other network. Although the specific configuration of the OLT  314  may vary depending on the type of PON, in an embodiment, the OLT  314  may comprise a transmitter and a receiver. When the other network is using a network protocol that is different from the PON protocol used in the PON, the OLT  314  may comprise a converter that converts the network protocol into the PON protocol. The OLT converter may also convert the PON protocol into the network protocol. 
         [0034]    The first splitter  313  may be configured to separate and redirect the first downstream wavelength channels (e.g. at about 1,550 nm) from the DOCSIS and EQAM unit  312  towards the ONs  320  and the upstream wavelength channels (e.g. at about 1,310 nm) from the ONs  320  to the OLT  314 . Additionally, the first splitter  313  may redirect the second wavelength channel (e.g. at about 1,490 nm) from the OLT  314  to the ONs  320 . In an embodiment, the first splitter  313  may comprise a wavelength division multiplexer/demultiplexer that may be configured to separate and redirect the different wavelength channels to their corresponding components. 
         [0035]    The CMTS  316  may be configured to receive and process the upstream data, Internet, and/or other services from the OLT  314 . Such data and/or services may be transmitted from the CMs in the customer equipment  330  and may be received and converted by the OLT  314  from optical signal format to electrical signal format. The OLT  314  may then forward the data and/or services to the CMTS  316  via an UEPI. The CMTS  316  may implement a DOCSIS protocol stack to process the received data and/or services, as described in more detail below, and then send the processed information to higher network layers. 
         [0036]    The second splitter  321  may be configured to separate and redirect the first downstream wavelength channels from the headend  310  to the DS O/E converter  324  and the upstream wavelength channels from the customer equipment  330  and the ONU  322  to the headend  310 . Additionally, the second splitter  321  may redirect the second wavelength channel from the headend  310  to the ONU  322 . Similar to the first splitter  313 , the second splitter  321  may comprise a wavelength division multiplexer/demultiplexer that may be configured to separate and redirect the different wavelength channels to their corresponding components. 
         [0037]    The ONU  322  may be any device that is configured to communicate with the OLT  314  and the customer equipment and/or another customers or users (not shown). Specifically, the ONU  322  may act as an intermediary between the OLT  314  and the customer. For instance, the ONU  322  may forward data received from the OLT  314  to the customer, and forward data received from the customer onto the OLT  314 . Although the specific configuration of the ONU  322  may vary depending on the type of PON, in an embodiment, the ONU  322  may comprise an optical transmitter configured to send optical signals to the OLT  314  and an optical receiver configured to receive optical signals from the OLT  314 . Additionally, the ONU  322  may provide native TDM PON services for other customers, such as business customers, that are not associated with the customer equipment  330 . 
         [0038]    Further, the ONU  322  may be configured to receive electrical signals from the CMs in the customer equipment  330  via the PDUP  326  and convert the signal into an optical signal, which may be sent in the upstream wavelength channel to the headend  310 . The electric signals from the CMs may comprise data and/or services that are intended for the CMTS  316 . Since a plurality of ONUs  322  in a plurality of ONs  320  may send different data and/or services for different customer equipment on the same upstream wavelength channel, e.g. according to the P2MP topology, the PDUP  326  in each ON  320  may be configured to implement to use TDM PON for upstream scheduling on ODN, as described below. As such, the ONs  320  may act as PDUPs in the HFC that properly schedule upstream transmissions to the headend  310 . The ON  320  and the ONU  322  may be typically located at distributed locations, such as customer and/or business premises, but may be located at other locations as well. 
         [0039]    The DS O/E converter  324  may be configured to convert the optical signal in the first downstream wavelength channel into electrical signals that may be forwarded to the customer equipment  330 . The electrical signal may carry the QAM video service and/or other data services, such as DOCSIS system control and triple play services. For instance, the QAM video service and other Internet or IP services may be received, via the coaxial plant  325 , by the STBs and the CMs in the customer equipment  330 , respectively. The different data and/or services in the first downstream wavelength channel that may be intended for different ONs  320  and/or different customer equipment  330  may be properly scheduled, e.g. by the components of the headend  310 , using the DOCSIS scheme. 
         [0040]      FIG. 4  illustrates an embodiment of a standard or traditional DOCSIS protocol stack  400 , which may be implemented to process the downstream and/or upstream transmitted data and/or services in a traditional or standard HFC, such as the HFC  100 . The DOCSIS protocol stack  400  may comprise a first stack  410  that may be implemented in a CMTS at the headend, e.g. the headend  110 , and a second stack  430  that may be implemented in a CM at a customer equipment, e.g. the customer equipment  130 . At the bottom of the first stack  410  and the second stack  430 , communications may be established via an ON  441  in the HFC, such as the ON  120 . ON  441  performs optical signals to electrical signals conversion. Specifically, the ON  441  may converge optical downstream and/or upstream signals between the CMTS and the CM. 
         [0041]    The first stack  410  may comprise a first IP layer  412  at the top for which corresponding frames may be encapsulated by a first IEEE 802.2 Logical Link Control (LLC) layer  414 , and subsequently by a first DOCSIS Security layer  416 . For downstream transmissions, the frames corresponding to the first DOCSIS security layer  416  may be encapsulated by a first DOCSIS DS MAC layer  418 , followed by a first DS Transmission Container (TC) layer  422 , and transmitted over the optical fiber cable  443  according to a first DS Physical Medium Dependent (PMD) layer  424 . For upstream transmissions, the frames corresponding to the first DOCSIS security layer  416  may be encapsulated by a first DOCSIS upstream (US) MAC layer  420 , and received over the optical fiber cable  443  according to a first US PMD layer  426 . The layers may be implemented from a higher logical level at the top of the stack (e.g. the first IP layer  412 ) to a lower physical level at the bottom of the stack (e.g. the first DS PMD layer  424 ) for transmitted downstream traffic, similar to that used for the International Organization for Standardization (ISO) protocol stack. Thus, the first stack  410  may be implemented to send data and/or services from a logical frame or packet format (e.g. IP packets) into a physical optical signal that may be forwarded to the ON  441 . Similarly, the upstream optical signal that is received from the ON  441  may be processed from a lower physical level at the bottom of the stack (e.g. the first US PMD  426 ) to a higher logical level of the stack. Thus, the first stack  410  may be implemented to convert the received data and/or services from a physical optical signal into a logical frame or packet format. 
         [0042]    Similarly, the second stack  430  may comprise a second IP layer  432  at the top for which corresponding frames may be encapsulated by a second IEEE 802.2 LLC layer  434  and subsequently by a second DOCSIS Security layer  436 . For downstream transmissions, the frames corresponding to the second DOCSIS Security layer  436  may be encapsulated by a second DOCSIS DS MAC layer  438 , followed by a second DS TC layer  442 , and transmitted over the coaxial cable  445  according to a second DS PMD layer  444 . For upstream transmissions, the frames corresponding to the second DOCSIS Security layer  436  may be encapsulated by a second DOCSIS US MAC layer  440 , and received over the coaxial cable  445  according to a second US PMD layer  446 . The second layers may implemented from the top of the stack to the bottom of the stack for transmitted upstream traffic and from the bottom of the stack to the top of the stack for received downstream traffic, similar to that used for the first stack  410 . 
         [0043]    As is typical in the case of upstream transmissions, an upstream electrical signal in QAM and/or quaternary phase-shift keying (QPSK) format may be transmitted from the CM via the coaxial plant to the ON  441 . The upstream electrical signal may be converted into a corresponding optical signal at the ON  441  and then transmitted via an optical fiber cable  442  to the CMTS, where the DOCSIS US MAC layer  420  information may be processed. In this case, the DOCSIS protocol may be implemented and the signals/frames may be processed accordingly in the CMTS and/or the CM in a manner transparent to the ON  441 . 
         [0044]      FIG. 5  illustrates an embodiment of a modified DOCSIS protocol stack  500 , which may be implemented to process the downstream and/or upstream transmitted data and/or services in a NG or modified HFC, such as the HFC  200 . Specifically, the DOCSIS protocol stack  500  may be used to support multiple ONs (or ONUs) in the HFC PON, which may be arranged in a P2MP topology, to properly schedule upstream transmissions from the different ONs to the headend. The DOCSIS protocol stack  500  may be arranged to allow each ON (or ONU) to act as a PDUP that may be aware of the DOCSIS protocol stack and process the signals/frames between the CMTS and the CM accordingly or may encapsulate an entire upstream burst including preambles into TDM PON frames from the CM to the CMTS. 
         [0045]    The DOCSIS protocol stack  500  may comprise a first stack  510  in the CMTS at the headend and a second stack  530  in the CM at the customer equipment. The first stack  510  and the second stack  530  may communicate via a PDUP  541 , e.g. in an ON in the NG HFC. The first stack  510  may be coupled to the PDUP  541  via an optical fiber cable  543  and the second stack  530  may be coupled to the PDUP  541  via a coaxial cable  545 . As such, the PDUP  541  may exchange optical upstream signals with the first stack  510  and electrical upstream signals with the second stack  530 . 
         [0046]    The first stack  510  may comprise a first IP layer  512  at the top for which corresponding frames may be encapsulated by a first IEEE 802.2 LLC layer  514 , and subsequently by a first DOCSIS Security layer  516 . For downstream transmissions, the frames corresponding to the first DOCSIS Security layer  516  may be encapsulated by a first DOCSIS DS MAC layer  518 , followed by a second DS TC layer  522 , and transmitted over the optical fiber cable  543  according to a first DS PMD layer  524 . For upstream transmissions, the frames corresponding to the first DOCSIS Security layer  516  may be received by a first DOCSIS US MAC layer  520  over the optical fiber cable  543  via a UEPI  521 . Similarly, the second stack may comprise a second IP layer  532  at the top for which corresponding frames may be encapsulated by a second IEEE 802.2 LLC layer  534 , and subsequently by a second DOCSIS Security layer  536 . For downstream transmissions, the frames corresponding to the second DOCSIS Security layer  536  may be encapsulated by a second DOCSIS DS MAC layer  538 , followed by a second DS TC layer  542 , and transmitted over the coaxial cable  545  according to a second DS PMD layer  544 . For upstream transmissions, the frames corresponding to the second DOCSIS Security layer  536  may be encapsulated by a second DOCSIS US MAC layer  540 , and received over the coaxial cable  545  according to a second US PMD layer  546 . The first layers and second layers may be implemented in a similar manner as in the DOCSIS protocol stack  400  to process the downstream and/or upstream signals between the CMTS and the CM. 
         [0047]    However, unlike US PMD  426  in the DOCSIS protocol stack  400 , the US PMD layer  546  in the DOCSIS protocol  500  may be implemented by the PDUP  541  instead of the CMTS to receive the upstream traffic over the coaxial cable  545 . The US PMD layer  546  may allow the PDUP  541  to receive the frames or packets that comprise data and/or services from the customer equipment and using TDM PON to encapsulate the frames or packets to provide an upstream scheduling mechanism in the P2MP topology of the NG HFC. Thus, the US PMD layer  546  may serve as a proxy layer to process upstream electrical signals from the CM at the PDUP  541 , e.g. converting the electrical signals into corresponding upstream optical signals that may be sent in a single channel/fiber to the headend. Thus, the corresponding optical signal may be transmitted over the optical fiber cable  543 , received by the UEPI  521 , and then processed by implementing the first DOCSIS US MAC layer  520  at the CMTS. 
         [0048]      FIG. 6  illustrates an embodiment of a framing scheme  600  that may be used by an ON (e.g. ON  220  or ON  320 ) that acts as a PDUP to properly schedule upstream transmissions to the headend. For instance, the framing scheme  600  may be implemented in the PDUP  541 . At the ON, an upstream burst electrical signal may be received in QAM and/or quaternary phase-shift keying (QPSK) format from the CM via the coaxial plant. The upstream electrical burst signal may comprise data and/or services from different customer equipment. 
         [0049]    The ON may encapsulate the upstream burst from CM that including DOCSIS MAC frames and preambles into TDM PON upstream frames. As such, the DOCSIS MAC frame  650  may comprise the US burst preamble  652 , a concatenated MAC header  654  that corresponds to a plurality of PDUs from the customer equipment, and a plurality of MAC headers and data PDUs. For instance, the DOCSIS MAC frame  650  may comprise a first MAC header (# 1 )  656  and a corresponding first data PDU  658 , and a second MAC header (# 2 )  660  and a corresponding second data PDU  662 . The first MAC header  656  and the first data PDU  658  may correspond to a first customer equipment and the second MAC header  660  and the second data PDU  662  may correspond to a second customer equipment. As such, the first MAC header  656  and the second MAC header  660  may indicate the first customer equipment and the second customer equipment, respectively. Since the PDUP layer may function as a second type repeater (or 2R regenerator), the ON may not need to include DOCSIS timing information. As such, the data from the CM is encapsulated and forwarded upstream without time synchronization or multiplexing. 
         [0050]    The ON may also encapsulate the DOCSIS MAC frame  650  into an EPON frame  610  using an Ethernet protocol. The DOCSIS MAC frame  650  may be embedded into a payload  640  of the EPON frame  610 , which may comprise an EPON header  612  and an Ethernet frame portion  614 . For example, the EPON header  612  may comprise an Inter-Frame Gap (IFG)  621 , a first unused field  622 , a first logical link identity (LLID)  624 , a second unused field  626 , a second LLID  627 , and a Cyclical Redundancy Check (CRC)  632 . In an embodiment, the first unused field  622  and/or the second unused field  626  may comprise markers to indicate that the payload  640  comprises the DOCSIS MAC frame  650 . The IFG  621  may be used to align the frame and the CRC  632  may be used to detect transmission errors. The Ethernet frame portion  614  may comprise a destination address (DA)  634 , a source address (SA)  636 , a link trace (LT)  638 , the payload  640  that comprises the DOCSIS MAC frame  650 , and a Frame Check Sequence (FCS)  642 . The FCS  642  may also be used to detect transmission errors. 
         [0051]    The ON may then convert the electrical signal into an optical signal, and thus send the EPON frame  610  in the upstream wavelength channel to the headend. At the headend, an OLT may receive and covert the optical signal into an electrical signal, and process the EPON frame  610  and may be forwarded DOCSIS MAC frames and preambles to the CMTS (e.g. CMTS  316 ) via UEPI interfaces. 
         [0052]      FIG. 7  is a flowchart of one embodiment of an upstream transmission method  700 , which may be used to properly schedule upstream transmissions from a plurality of customer equipment in a P2MP PON HFC, e.g. the HFC  200 . The upstream transmission method  700  may be implemented by an ON (e.g. the ON  220  or ON  320 ) that acts as a PDUP, e.g. according to the DOCSIS protocol stack  500 . At block  710 , the ON may receive an electrical burst signal from a customer equipment coupled to the ON, such as the CMs in the customer equipment  230  or  330 . The electrical burst signal may comprise a preamble and a plurality of DOCSIS MAC frame that each comprises at least one PDU. The DOCSIS MAC frame may comprise information that indicates the customer equipment associated with each of the PDUs. At block  720 , the electrical burst may be encapsulated into at least one frame using a TDM PON protocol, such as EPON. The frame may comprise information that indicates the ON associated with the customer equipment. At block  740 , the frame may be transmitted upstream to a headend in an optical signal that correspond to the received electrical burst signal. For instance, the ONU at the ON may convert the electrical burst signal on an optical carrier. The method  700  may then end. 
         [0053]    The network components described above may be implemented on any general-purpose network component, such as a computer or network component with sufficient processing power, memory resources, and network throughput capability to handle the necessary workload placed upon it.  FIG. 8  illustrates a typical, general-purpose network component  800  suitable for implementing one or more embodiments of the components disclosed herein. The network component  800  includes a processor  802  (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage  804 , read only memory (ROM)  806 , random access memory (RAM)  808 , input/output (I/O) devices  810 , and network connectivity devices  812 . The processor  802  may be implemented as one or more CPU chips, or may be part of one or more application specific integrated circuits (ASICs). 
         [0054]    The secondary storage  804  is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an overflow data storage device if RAM  808  is not large enough to hold all working data. Secondary storage  804  may be used to store programs that are loaded into RAM  808  when such programs are selected for execution. The ROM  806  is used to store instructions and perhaps data that are read during program execution. ROM  806  is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of secondary storage  804 . The RAM  808  is used to store volatile data and perhaps to store instructions. Access to both ROM  806  and RAM  808  is typically faster than to secondary storage  804 . 
         [0055]    At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, R l , and an upper limit, R u , is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R l +k*(R u −R l ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. The discussion of a reference in the disclosure is not an admission that it is prior art, especially any reference that has a publication date after the priority date of this application. The disclosure of all patents, patent applications, and publications cited in the disclosure are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to the disclosure. 
         [0056]    While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented. 
         [0057]    In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.