Patent ID: 8305954
Filing Date: 2012-11-06
Classification: H04J,H04W

Abstract:
1. Method for synchronizing clocks of a set of nodes in a TDMA (“Time Division Multiple Access”) multi-hop communication network comprising a plurality of nodes, among which some called time reference (TR) nodes are synchronized to a common time reference through a predetermined out-of-band synchronization mechanism, other nodes being called non-TR nodes, each node comprising an internal clock, the method comprising transmitting, at the level of at least one of said TR nodes, a broadcast beacon packet during a given time slot of sub-frames, each sub-frame comprising a plurality of time slots; propagating among the remaining nodes said beacon packet using the slotted structure of the TDMA protocol, each node being pre-assigned a conflict-free time slot in a sub-frame to broadcast said beacon packet received from another node in a previous slot of said sub-frame; upon reception of said beacon packet by a first node from a second node, of estimating the time when the first node transmitted said beacon packet and computing the offset between internal clock of the first node and internal clock of the second node; and updating in at least two of said non-TR nodes the internal clock based on an updated offset estimate, upon reception of said beacon packet.