Synchronization of distributed nodes

Abstract

Dynamic, untethered array nodes are frequency, phase, and time aligned/synchronized, and used to focus their transmissions of the same data coherently on a target or in the target's direction, using time reversal or directional beamforming. Information for alignment/synchronization may be sent from a master node of the array to other nodes, over non-RF links, such as optical and acoustic links. Some nodes may be connected directly to the master nodes, while other nodes may be connected to the master node through one or more transit nodes. A transit nodes may operate to (2) terminate the link when the alignment/synchronization information is intended for the node, and (2) pass through the alignment/synchronization information to another node without imposing its local clock properties on the passed through alignment/synchronization information. In this way, an end point node may be aligned/synchronized to the master node without a direct link between the two nodes.

What is claimed is: 
     
         1 . A method of synchronizing an array of nodes, the method comprising steps of:
 receiving a first non-radio frequency (non-RF) signal carrying a first radio frequency (RF) signal from a master node of the array, the step of receiving the first non-RF signal being performed at a first transit node of the array over a first non-RF side channel link, the first RF signal including properties of a local reference of the master node;   dividing the first non-RF signal into a first portion of the first non-RF signal and a second portion of the first non-RF signal, the first portion of the first non-RF signal carrying a first portion of the first RF signal, the second portion of the first non-RF signal carrying a second portion of the first RF signal, the first portion of the first RF signal including the properties of the local reference of the master node, the second portion of the first RF signal including the properties of the local reference of the master node;   passing the first portion of the first non-RF signal through the first transit node to at least a first end point node of the array without imposing clock properties of the first transit node on the first portion of the first non-RF signal;   synchronizing local reference of the first end point node to the local reference of the master node using the properties of the local reference of the master node included in the first portion of the first RF-signal, the step of synchronizing the local reference of the first end point node to the local reference of the master node comprising frequency and phase alignment of the first end point node to the master node; and   synchronizing local reference of the first transit node to the local reference of the master node using the properties of the local reference of the master node included in the second portion of the first RF signal, the step of synchronizing the local reference of the first transit node to the local reference of the master node comprising frequency and phase alignment of the first transit node to the master node;   
       wherein:
 each node of the master node, the first transit node, and the end point node comprises a separate clock; and 
 each of the master node, the first transit node, and the end point node is free to move in at least one dimension with respect to other nodes of the master node, the first transit node, and the end point node. 
 
     
     
         2 . The method as in  claim 1 , further comprising:
 terminating the second portion of the first non-RF signal at the first transit node.   
     
     
         3 . The method as in  claim 2 , wherein the step of terminating is performed concurrently with the step of passing the first portion of the first non-RF signal. 
     
     
         4 . The method as in  claim 3 , wherein the step of passing the first portion of the first non-RF signal comprises indirectly passing the first portion of the first non-RF signal to the first end point node via a second transit node of the array. 
     
     
         5 . The method as in  claim 4 , further comprising synchronizing local reference of the second transit node to the local reference of the master node using the properties of the local reference of the master node included in the first portion of the first RF-signal, the step of synchronizing the local reference of the second transit node to the local reference of the master node comprising frequency and phase alignment of the second transit node to the master node. 
     
     
         6 . The method as in  claim 3 , wherein the step of passing the first portion of the first non-RF signal comprises directly passing the first portion of the first non-RF signal to the first end point node. 
     
     
         7 . The method as in  claim 3 , further comprising:
 receiving the first portion of the first non-RF signal at a second end point node of the array; and   synchronizing local reference of second end point node to the local reference of the master node using the properties of the local reference of the master node included in the first portion of the first RF-signal, the step of synchronizing the local reference of the second end point node to the local reference of the master node comprising frequency and phase alignment of the second end point node.   
     
     
         8 . The method as in  claim 3 , wherein:
 the step of synchronizing the local reference of the first end point node to the local reference of the master node further comprises time alignment of the first end point node to the master node; and   the step of synchronizing the local reference of the first transit node to the local reference of the master node further comprises time alignment of the first transit node to the master node.   
     
     
         9 . A method as in  claim 3 , wherein the step of dividing comprises separating the first portion of the first non-RF signal from the second portion of the first non-RF signal using an optical power splitter. 
     
     
         10 . A method as in  claim 3 , wherein the step of dividing comprises separating the first portion of the first non-RF signal from the second portion of the first non-RF signal using an optical wavelength filter. 
     
     
         11 . The method as in  claim 3 , wherein the each of the master node, the first transit node, and the end point node is free to move in at least two dimensions with respect to other nodes of the master node, the first transit node, and the end point node. 
     
     
         12 . The method of  claim 3 , wherein each of the master node, the first transit node, and the end point node is free to move in three dimensions with respect to other nodes of the master node, the first transit node, and the end point node. 
     
     
         13 . The method of  claim 12 , wherein the first non-RF side channel link is a free-space optical link, and each node of the array is free to move in three dimensions and free to rotate around a plurality of axes. 
     
     
         14 . The method as in  claim 3 , wherein:
 the step of passing comprises transmitting the first portion of the first non-RF signal to the first end point node over a second non-RF side channel link; and   the first non-RF side channel link and the second non-RF side channel link are RF-over-optics links.   
     
     
         15 . The method as in  claim 3 , wherein:
 the step of passing comprises transmitting the first portion of the first non-RF signal to the end point node over a second non-RF side channel link; and   the first non-RF side channel link and the second non-RF side channel link are RF-over-acoustic links.   
     
     
         16 . A communication method comprising steps of:
 synchronizing the array nodes as in  claim 3 ;   distributing across the array common data for transmission to a target;   operating all nodes of the array as a phased array to transmit to the target RF signals carrying the common data.   
     
     
         17 . A communication method comprising steps of:
 synchronizing the array nodes as in  claim 3 ;   distributing across the array common data for transmission to a target;   coherently transmitting from all nodes of the array to the target RF signals carrying the common data, so that the signals carrying the common data add constructively at the target, the step of coherently transmitting comprising location-focusing using time-reversal.   
     
     
         18 . An array of nodes, comprising:
 a master node comprising a master node processor, a master node radio frequency (RF) transceiver coupled to the master node processor, a master node local reference, and a master node non-radio frequency (non-RF) transceiver coupled to the master node processor, wherein the master node is configured by the master node processor to emit a non-RF signal over a non-RF side channel link, the non-RF signal carrying an RF signal including properties of the master node local reference;   a first transit node comprising a first transit node processor, a first transit node RF transceiver coupled to the first transit node processor, a first transit node local reference, and a first transit node non-RF processing module coupled to the first transit node processor, wherein the first transit node non-RF processing module comprises a first transit node non-RF transceiver configured to receive from free-space the non-RF signal, a first transit node non-RF splitter configured to separate the non-RF signal into a first non-RF component terminated at the first transit node and a second non-RF component passed through the first transit node into free-space without properties of the first transit node local reference being imposed on the second non-RF component, and first transit node electronic circuitry configured to obtain from the first non-RF component data in the non-RF signal, wherein the first non-RF component comprises a first RF portion of the RF signal that includes the properties of the master node local reference and the second non-RF component comprises a second RF portion of the RF signal that includes the properties of the master node local reference, and wherein the first transit node is configured by the first transit node processor to synchronize the first transit node local reference to the master node local reference using the properties of the master node local reference included in the non-RF signal received by the first transit node;   a first end point node comprising a first end point node processor, a first end point node RF transceiver coupled to the first end point node processor, a first end point node local reference, and a first end point node non-RF transceiver coupled to the first end point node processor, wherein the first end point node is configured by the first end point node processor to receive from free-space a first part of the second non-RF component passed through the first transit node using the first end point node non-RF transceiver and synchronize the first end point node local reference to the master node local reference using the properties of the master node local reference in the second RF portion of the second non-RF component, the first part of the second non-RF component comprising a first part of the second RF portion of the RF signal;   
       wherein:
 each node of the first transit node, the master node, and the first end point node is free to move in at least one dimension with respect to other nodes of the first transit node, the master node, and the first end point node. 
 
     
     
         19 . The array of nodes as in  claim 18 , wherein said each node of the first transit node, the master node, and the first end point node is free to move in at least two dimensions with respect to the other nodes of the first transit node, the master node, and the first end point node. 
     
     
         20 . The array of nodes as in  claim 18 , wherein said each node of the first transit node, the master node, and the first end point node is free to move in three dimensions with respect to the other nodes of the first transit node, the master node, and the first end point node. 
     
     
         21 . The array of nodes as in  claim 20 , wherein said each node of the first transit node, the master node, and the first end point node is free to rotate around a plurality of axes. 
     
     
         22 . The array of nodes as in  claim 21 , wherein:
 the first transit node, the master node, and the first end point node are configured to transmit to a target coherent RF signals carrying common data, so that the coherent RF signals carrying the common data add constructively in a general direction from the array to the target, whereby the array of nodes is configured to operate as a phased array.   
     
     
         23 . The array of nodes as in  claim 21 , wherein the first transit node, the master node, and the first end point node are configured as a time-reversal mirror to transmit to a target coherent RF signals carrying common data so that the coherent RF signals carrying the common data add constructively at the target. 
     
     
         24 . The array of nodes as in  claim 18 , further comprising:
 a second transit node, the second transit node comprising a second transit node processor, a second transit node RF transceiver coupled to the second transit node processor, a second transit node local reference, and a second transit node non-RF processing module coupled to the second transit node processor, the second transit node non-RF processing module comprising a second transit node non-RF transceiver, a second transit node non-RF splitter, and second transit node electronic circuitry;   
       wherein:
 the first end point node receives the first part of the second non-RF component passed through the first transit node indirectly through the second transit node; and 
 the second transit node is configured by the second transit node processor to synchronize the second transit node local reference to the master node local reference using the properties of the master node local reference included in the second non-RF signal. 
 
     
     
         25 . The array of nodes as in  claim 18 , further comprising:
 a second end point node, the second end point node comprising a second end point node processor, a second end point node RF transceiver coupled to the second end point node processor, a second end point node local reference, and a second end point node non-RF processing module coupled to the second end point node processor;   
       wherein:
 the second end point node is configured to receive from free-space a second part of the second non-RF component passed through the first transit node, and to perform synchronization of the local reference of the second end point node to the local reference of the master node using the properties of the local reference of the master node carried by the second RF portion, the synchronization comprising frequency, phase, and time alignment of the second end point node. 
 
     
     
         26 . The array of nodes as in  claim 18 , wherein the non-RF side channel link is an RF-over-optical link. 
     
     
         27 . The array of nodes as in  claim 18 , wherein the non-RF side channel link is an RF-over-acoustic link.