The two opposite requirements of tightly synchronizing the network with a minimum number of RF transmissions and with high accuracy can be efficiently addressed using the approach suggested by the FTSP, where multiple inactive nodes can hear the synchronization messages transmitted by the master node in one-way timing cells exchange mechanisms. To increase the utility of this one-way mechanism, Maroti et al. proposed the synchronization of nodes present in the communication range of the master node (broadcasting the timing beacons), where each node receiving the timing cells transmitted by the master node estimates its own clock parameters and synchronizes with the master node accordingly. However, the similar situation pertaining to the two-way timing exchange mechanism, i.e., the framework in which the nodes located in the common broadcast region of a master and slave node can overhear the time synchronization packets between them and exploit the acquired information to achieve clock synchronization remained largely unnoticed until the PBS protocol introduced it (as discussed in detail in Chapter 8). Note that although the idea of SRS is quite old and has most famously been used in NTP for a long time, it is due to the wireless nature of communication channels in sensornets that the technique of synchronization of silent nodes located in their common broadcast region can be exploited. Therefore, the clock synchronization requirements can be reasonably met without paying any price on the network lifetime (i.e., without exchanging additional messages for clock synchronization purposes and thereby reducing battery life) or node hardware (e.g., by improving the quality of the quartz crystals or by utilizing more expensive power-efficient batteries).