text: In a hybrid PON xDSL access network, multiple customer premise equipment (CPE) nodes connect over individual digital subscriber lines (DSLs) to a drop-point device. The drop-point device, which is typically reverse powered from the customer, is co-located with an optical network unit (ONU) of the passive optical network (PON). We demonstrate that the drop-point experiences very high buffer occupancies when no flow control or standard Ethernet PAUSE frame flow control is employed. In order to reduce the buffer occupancies in the drop-point, we introduce two gated flow control protocols that extend the polling-based PON medium access control to the DSL segments between the CPEs and the ONUs. We analyze the timing of the gated flow control mechanisms to specify the latest possible time instant when CPEs can start the DSL upstream transmissions so that the ONU can forward the upstream transmissions at the full PON upstream transmission bit rate. Through extensive simulations for a wide range of bursty traffic models, we find that the gated flow control mechanisms, specifically, the ONU and CPE grant sizing policies, enable effective control of the maximum drop-point buffer occupancies.
  @cite_41: We investigate the challenges in designing the network architecture for running EPON (Ethernet Passive Optical Network) Protocol over Coax, or EPoC in short. EPoC is the transparent extension of EPON over a cable operator's Hybrid Fiber-Coax (HFC) network, and uses a hybrid of optical and coaxial technologies to carry traffic to and from end-users and the Internet backbone. For managing and controlling such a hybrid network, a network operator will prefer to have a unified scheduling, management, and quality-of-service (QoS) environment that includes both the optical and coax portions of the network. This can be achieved by extending the EPON Medium Access Control (MAC) to run over the coax physical layer, to have a centralized end-to-end network control from the cable head-end to the end-users' premises. The use of the coax portion of the network is transparent to EPON protocol operation in the headend, as the same MAC runs over the entire network. In this article, we describe the architecture of EPoC, and outline how the EPON MAC Control, i.e., the EPON Multi-Point Control Protocol (MPCP) can be extended for designing an end-to-end Multi-Point MAC Control for EPoC. We explain the design of several MAC functions and their operation, including framing for coax, Ethernet frame fragmentation, generation of upstream and downstream Media Allocation Plans, and automatic discovery and registration of user equipment. With strong backing from both service operators and equipment vendors, EPoC is set to become a rapidly-evolving standard within the next few years, and the creation of the IEEE 802.3bn Task Force for EPoC is a major step in that direction.
  @cite_5: We present different mechanisms for downstream transmissions in the coax segment of Ethernet Passive Optical Network (EPON) Protocol over Coax (EPoC). EPoC is the transparent extension of EPON over a cable operator's Hybrid Fiber-Coax network. For managing and controlling such a hybrid network, a network operator prefers to have a unified scheduling, management, and quality of service environment that includes both the optical and coax portions of the network. In EPoC, this is achieved by extending the EPON Medium Access Control to run over the coax physical layer, to have a centralized end-to-end network control from the cable head-end to the end users premises. In this paper, we focus on the downstream transmissions in EPoC. We study three different framing approaches for downstream coax frames based on how sub-carriers in an orthogonal frequency division multiplexed symbol are modulated. We discuss the merits and demerits of each approach and then compare them based on their control overheads and the maximum average data transmission rates each of them can achieve. We analyze how different parameters such as modulation profile, symbol duration, number of sub-carriers and length of resource blocks affect the data rates and the performance of downstream transmissions. We present simulation results to examine the implications of these factors on packet-level performance, such as delay. The results indicate that dynamic and hybrid framing approaches tend to perform better than static approaches, when traffic and usage pattern are identical to those in real-world scenarios. Finally, we outline the important engineering and research problems in this area which can be topics of future research.
  @cite_1: We propose a dynamic bandwidth allocation (DBA) scheme for EPON (Ethernet Passive Optical Network) Protocol over Coax, or EPoC in short. EPoC is the transparent extension of EPON over a cable operator's Hybrid Fiber-Coax (HFC) network, and is set to become a rapidly-evolving standard within the next few years, with strong backing from the industry, and with the creation of the IEEE 802.3bn Task Force. For managing and controlling EPoC, a network operator prefers to have a unified scheduling and quality-of-service (QoS) environment that includes both the optical and coax portions of the network. This is achieved by extending the EPON Medium Access Control (MAC) to run over the coax physical layer, to have a centralized end-to-end network control from the cable headend to the end-users' premises. In this paper, we describe a centralized DBA scheme for EPoC, where all allocation decisions are made at the operator's headend. The DBA is aware of the hybrid nature of the network, and considers round-trip times between optical and coax network units for intelligent and efficient allocations. We also formulate the allocation problem as a generalized optimization problem, which can be extended according to specific deployment scenarios. We present some initial simulation results to demonstrate the performance of the DBA.
summary: In November 2011, the IEEE 802.3 working group initiated the creation of a study to extend the EPON protocol over hybrid fiber-coax cable television networks; the developing standard is referred to as EPON Protocol over Coax (EPoC) @cite_41 . Developing bandwidth allocation schemes for EPoC has received little research attention to date. In particular, a DBA algorithm that increases channel utilization in spite of increased propagation delays due to the coaxial copper network was designed in @cite_1 . Mechanisms to map Ethernet frame transmissions to from the time division multiplexed channel of the PON to the time and frequency division multiplexed coaxial network have been studied in @cite_41 @cite_5 .