In the hybrid approach, a multicast message may be used whenever the information going to many eNBs is the same. It may also be advantageous to send information that is unique to one eNB as a unicast message. In the hybrid communication model, multicast communication may be used for synchronization and announce messages, and unicast communication may be used for follow-up messages.

In particular, announce messages may be sent as PTP multicast messages (e.g., UDP port 319) to the PTP primary address. Moreover, synchronization messages can be unicast or multicast messages. Furthermore, follow-up messages (delay-request, delay-response) may be sent as unicast messages.

Note that, if synchronization is multicast, then there may be less loading on the synchronization master.

Note that is some embodiments there may be multiple synchronization masters in different PTP domains.

In some embodiments, different clusters or sets of eNBs are synchronized. For example, if synchronization masters are all synchronized to GPS or NL, then the synchronization masters may be automatically synchronized with each other. If a synchronization master is deriving its reference from a local clock or a local timing reference and driving the cluster, it may be important to synchronize the synchronization masters of the different clusters. This can be achieved by implementing a boundary clock. Note that a boundary clock can be an eNB in one cluster and synchronization master for another cluster.