FIELD OF THE INVENTION

The field of the invention relates generally to synchronization of wireless nodes which are used to initiate a pyrotechnic device.

BACKGROUND OF THE INVENTION

Previous attempts at achieving zero latency for timed pyrotechnic events specify that synchronization between modules must be achieved. In some systems the latency of RF communications packets transmitted and received are asymmetric, i.e. the transmit latency is not equal to nor directly correlatable to the receive latency.

In many systems the transmit latency is unpredictable, as it is dependent on various queues and real-time thread sequencing within the host system and the RF system, plus the additional latency of waiting for a clear transmission channel and/or an unpredictable number of potential retransmit cycles. In contrast, most systems have relatively predictable receive latency because the receiver must respond in real time to the incoming transmit timing and bitrate.

It is also true that in pyrotechnic systems event timing is critical to the show performance and bandwidth of the transmission system is often limited. While other synchronization techniques, such as Network Time Protocol (NTP), used in Ethernet systems are effective in wired systems and those with high bandwidth wireless bridges, they require significantly greater bandwidth than may be available in a pyrotechnic controller. Moreover, the pyrotechnic control system may not be operating in a true peer-to-peer system applicable to NTP.

The bandwidth problem is exacerbated if the pyrotechnics system is implemented as a centralized controller communicating with some number of pyrotechnic ignition modules. The modules may be constructed so as to minimize communications between ignition modules and maximize the communications bandwidth available to the central controller. In some systems there may be 1000 or more ignition modules for each centralized controller. It is also worth noting that the bandwidth limitations diminish with the number of modules such that if there are a very small number of modules, such as but not limited to one ignition controller and one central controller for example, other synchronization strategies such as NTP may become acceptable.

In other systems, synchronization is achieved by transmitting one or more packets from one communications node with knowledge of the given system time to another node with no knowledge of the system time. Over a number of packet transmissions in one or both directions, one can assume that the average latency between the two can be subtracted out but this leaves the actual skew between the two nodes equivalent to the magnitude of the average latency in the worst case transmission path. As discussed above, this average latency may be large and is subject to change over time as the RF environment of the pyrotechnics venue changes. Measurements of useable channels and channel saturation may be radically different between the morning of setup and evening showtime when perhaps tens of thousands of spectators with cellular network devices, wireless microphones, wireless speaker systems, and other wireless infrastructure devices are added to the venue.

Accordingly, it would be beneficial to have a method and apparatus for synchronization that takes into account one or more of the issues discussed above as well as possibly other issues.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide improved systems and methods for effecting time synchronization between disparate nodes on a network in a pyrotechnic environment. According to an embodiment of the present invention, a system and method for effecting time synchronization between disparate nodes on a network where at least one node has knowledge of the true network time, at least one other node requires synchronization to the true network time, and a third node is utilized to facilitate the synchronization process

This synchronization strategy is implemented with at least two other communications nodes in the system other than the centralized controller. The application purpose of these nodes is immaterial, as long as they utilize the same or compatible RF signaling and communications system and protocol as the centralized controller.

Given at least three communications nodes denoted herein as A, B, and C, A will be designated as the central controller whose function will include being the master clock. The purpose of the system is to synchronize B and C. Here B will be designated as the node to be synchronized, and C will be designated a “helper” node.

In one embodiment, the first transmission is a unicast packet from A to C. The centralized controller sends a request to the helper node to send a synchronization transmission. This first transmission is not dependent on any latency in A's transmission path or C's receiver path. The second transmission is a broadcast packet from C to all other modules, here A and B.

This transmission is independent of the C's transmission latency but is dependent on A and B's receive latency. It is assumed that the receive latency is nearly equivalent for A and B. The final transmission is a broadcast message from A to B with the time on the Master Clock at which A received the synchronization message from C. This message is not dependent on the transmit or receive latency of A or B. B calculates the offset to its clock given the time at A and B should be identical, and B is now synchronized with a skew limited to the difference between the receive latency of A and B.

These and other objects, aspects and advantages of the present invention will be better appreciated in view of the drawings and following detailed description of preferred embodiments.

