PTP transparent clock system upgrade solution

#The present invention relates generally to timing synchronization in communication systems and, more particularly, to timing synchronization for non-timing aware network nodes.

#It is often advantageous in a communication network for devices in the network to have a common time base. For example, in 3G mobile/cellular communication systems, radio base stations (RBS) are synchronized to within a few microseconds. Precise synchronization facilitates efficient communication such as for allocation of time slots among devices and interference reduction. The electronics industry has developed several standard protocols for use in synchronizing clocks, for example, the Precision Time Protocol (PTP) of IEEE Std. 1588. PTP includes sending timing-related messages between nodes in a communication network. The timing-related messages include, for example, a first node transmitting over a link a time-stamped packet to supply its time base to a second node, and the second node transmitting, over the link, a packet to the first node requesting and thereafter receiving a reply with the time of receipt of the request packet, so that the second node may have information regarding packet time of travel over the link. With these timing related messages the second node may be able to synchronize its local clock to the clock time of the first node.

#In many instances a network could have multiple nodes between nodes which are to be synchronized. Not surprisingly, a variety of constructs have been developed relating to timing distribution, and nodes may serve as or be identified as master clocks, boundary clocks, ordinary clocks (a category that may include master clocks), and transparent clocks, for example. The use of such constructs has been helpful in synchronizing nodes of larger networks.

#FIG. 1 is a block diagram of portions of a communications network in accordance with aspects of the invention.

#FIG. 2 is a block diagram of a network node in a communications network in accordance with aspects of the invention.

#FIG. 3 is a further block diagram a network node in a communication network in accordance with aspects of the invention.

#FIG. 1 is a block diagram of portions of a communications network in accordance with aspects of the invention. The portions of the communications network illustrated include 5 nodes. A first node 111 is a PTP-aware node, that is, the first node processes packets in accordance with the Precision Time Protocol. The first node is coupled to a second node 112 and a third node 113, with the second node also coupled to the third node. The third node is also a PTP-aware node, and the first node and the third node may synchronize their clocks using PTP operations. In some embodiments the first node may provide a master clock and the third node may provide a boundary clock, for example, although in various embodiments the determination of which node includes the master clock will generally be determined using a best master clock algorithm (BMCA).

#The second node is not configured to process PTP packets in accordance with the PTP protocol. The second node is therefore not a PTP-aware node, instead the second node is a PTP-unaware node. It is possible that some packets communicated between the first and third nodes may pass through the second node, depending on various packet and network parameters. In such an event, such packets may cause difficulties in achieving or maintaining proper time synchronization of the first and thirds nodes.

#A first transparent clock converter 121, however, couples the second node with the first and third nodes. The first transparent clock converter is generally placed about a line side of the node, and the first transparent clock converter implements a PTP transparent clock for the node. The first transparent clock converter may implement the PTP transparent clock by determining a transit time of a packet through the node, and setting a value in the packet indicative of the transit time. Placement of the first transparent clock converter on the line side of the second node may be considered to convert the second node from a PTP-unaware node to a PTP transparent clock node 125.