EPON/EPOC time division duplex (TDD) mode
View Patent ↗Embodiments enable a half-duplex Time Division Duplex (TDD) mode for Ethernet Passive Optical Network (EPON) or EPON over Coax (EPoC) networks. Specifically, embodiments provide systems and methods for enabling an Optical Line Terminal (OLT)/Coaxial Line Terminal (CLT) to share a physical medium spectrum in time with the Optical Network Units (ONUs)/Coaxial Network Units (CNUs) that it services. In an embodiment, the OLT/CLT includes an EPON scheduler that can schedule downstream and upstream transmissions over the same physical medium spectrum. In another embodiment, the OLT/CLT is equipped with a burst mode transmit physical layer (PHY) module, which can be controlled by an EPON Medium Access Control (MAC) module, to transmit in burst mode over the physical medium. In a further embodiment, there is provided an ONU/CNU with a burst mode receive PHY module. The burst mode receive PHY module can maintain clock timing even with non-continuous reception from the OLT/CLT.
1. A line terminal coupled via a physical medium to a network the line terminal comprising:
a transmit physical layer (PRY) module, coupled to the physical medium;
an Ethernet Passive Optical Network (EPON) scheduler configured to generate a control signal identifying a downstream transmission slot on the physical medium, wherein the downstream transmission slot is scheduled to not overlap in time with any upstream transmission slots on the physical medium; and
an EPON Medium Access Control (MAC) module configured to receive, from the EPON scheduler, the control signal and to control the transmit PHY module, according to the control signal, to transmit a data signal during the downstream transmission slot to the network unit,
wherein the transmit PHY module includes a burst transmitter, and wherein the EPON MAC module is farther configured to turn off the burst transmitter after an end time of the downstream transmission slot, so that the burst transmitter is turned off when, any upstream transmission slots occupy the physical medium.
2. The line terminal of claim 1 , wherein the EPON MAC module is further configured to turn on the burst transmitter before a start time of the downstream transmission slot.
3. The line terminal of claim 2 , wherein the EPON MAC module is further configured to forward MAC layer data to the transmit PHY module in accordance with the control signal, and wherein, the transmit PHY module includes a data detector configured to detect the presence or absence of the MAC layer data from the EPON MAC module and to control the burst transmitter responsive to the presence or absence of the MAC layer data from the EPON MAC module.
4. The line terminal of claim 1 , wherein the control signal identifies a periodic time interval for the downstream transmission slot, and wherein the EPON MAC module is further configured to control the transmit PHY module to transmit the data signal periodically to the network unit in accordance with the periodic time interval.
5. The line terminal of claim 1 , wherein the line terminal includes an Optical Line Terminal (OLT) or a Coaxial Line Terminal (CLT).
6. The line terminal of claim 1 , wherein the network unit includes an Optical Network Unit (ON U) or a Coaxial Network Unit (CNU).
7. The line terminal of claim 1 , wherein the physical medium includes one or more of: an optical fiber and a coaxial cable.
8. The line terminal of claim 1 , wherein the physical medium is an optical fiber using a single wavelength.
9. A line terminal coupled via a physical medium to a network unit, the line terminal comprising:
a transmit physical layer (PHY) module, coupled to the physical medium;
an Ethernet Passive Optical Network (EPON) scheduler; and
an EPON Medium Access Control (MAC) module configured to receive, from the EPON scheduler, a control signal identifying a downstream transmission slot on the physical medium, and to control the transmit PHY module, according to the control signal, to transmit a data signal during the downstream transmission slot to the network unit,
wherein the EPON scheduler is configured to receive a reservation message from the EPON MAC module and to send the control signal to the EPON MAC module responsive to the reservation message.
10. The line terminal of claim 9 , wherein the reservation message includes a desired time duration for the downstream transmission slot.
11. The line ten ii al of claim 9 , herein the reservation message includes a Multi-Point Control Protocol (MPCP) Report message.
12. The line terminal of claim 9 , wherein the control signal includes a Multi-Point Control Protocol (MPCP) GATE message.
13. The line terminal of claim 12 , wherein the EPON MAC module is further configured to control the transmit PHY module to transmit the MPCP GATE message over the physical medium before a start time of the downstream transmission slot.
14. The line terminal of claim 9 , wherein the EPON scheduler is further configured to receive a second reservation message that is received from the network unit, and to schedule an upstream transmission slot for the network unit responsive to the second reservation message.
15. The line terminal of claim 14 , wherein the EPON scheduler is further configured to account for a turn-around-time over the physical medium between the downstream transmission slot and the upstream transmission slot.
16. The line terminal of claim 12 , wherein the MPCP GATE message includes a size of a downstream queue of the EPON MAC module.
17. A method for transmission from an Optical Line Terminal (OLT) or a Coaxial Line Terminal (CLT) to a network unit over a physical medium, comprising:
receiving, by an Ethernet Passive Optical Network (EPON) Medium Access Control (MAC) module of the OLT or CLT, a control signal identifying a downstream transmission slot on the physical medium from an EPON scheduler, wherein the downstream transmission slot is scheduled to not overlap in time with any upstream transmission slots on the physical medium; and
controlling, by the EPON MAC module, a physical layer (PHY) transmitter of the OLT or CLT to transmit a data signal during the downstream transmission slot to the network unit, wherein controlling the PHY transmitter of the OLT or CLT comprises turning off the PHY transmitter after an end time of the downstream transmission slot so that the PHY transmitter is turned off when any upstream transmission slots occupy the physical medium.
18. The method of claim 17 , wherein controlling the PHY transmitter of the OLT or CLT comprises turning on the PHY transmitter before a start time of the downstream transmission slot.
19. The method of claim 17 , wherein the control signal includes a Multi-Point Control Protocol (MPCP) GATE message, the method further comprising:
transmitting the MPCP GATE message over the physical medium before a start time of the downstream transmissions slot.
20. The method of claim 17 , further comprising:
receiving a reservation message from the network unit; and
scheduling, responsive to the reservation message, an upstream transmission slot for the network unit, wherein scheduling the upstream transmission slot comprises accounting for a turn-around-time over the physical medium between the downstream transmission slot and the upstream transmission slot.