ific problems. Some other cases, such as circuit emulation, are covered earlier in the chapter in the discussion of frequency synchronization using packet-based methods. The idea here is not to delve into the myriad details around every unique scenario, but to demon- strate how the knowledge gained up until this point can be applied to other cases. No matter what is the problem that requires solving, the solution will involve the same principles of frequency trans- fer, and phase/time alignment. It will entail using physical and packet methods in combination with sources of frequency, phase, and time such as atomic clocks and GNSS receivers. 9.9.1 DOCSIS Cable and Remote PHY Devices Cable operators, under pressure for ever-higher bandwidth from their subscribers, are working on relieving bottlenecks on their hybrid fiber coax (HFC) networks by adopting a new architecture, one that replaces the analog fiber plant with packet-based transport. In this new design, the converged cable access platform (CCAP) core functions are split from the PHY (physical) function. The PHY function is moved further toward the edge of the network, and the two systems communicate with pseudowires over an IP/Ethernet network. This new network is called the converged interconnect network (CIN). This evolution pushes the beginning of the cable portion of the network much closer to the sub- scriber and fills the gap in the middle with Ethernet-style devices. A new device called a Remote PHY Device (RPD) is used at the head of a cable run, and existing coax cable is used to complete the last mile. This allows the cable operator to offer much higher bandwidth services, on par with fiber services, but still retain the investment in its existing HFC plant. Figure 9-37 illustrates the building blocks of the new architecture. DOCSIS signaling Remote PHY signaling Cable Cable modem modem IP/Ethemet fiber network Coax network Internet Converged interconnect network Cable Cable modem modem Figure 9-37 Cable Network Using Remote PHY Architecture To e