Situational awareness (SA) in radio silence (spatial awareness)
A system may include a transmitter node and a receiver node. Each node may include a communications interface including at least one antenna element and a controller operatively coupled to the communications interface, the controller including one or more processors, wherein the controller has information of own node velocity and own node orientation. Each node of the transmitter node and the receiver node may be in motion relative to each other. Each node may be time synchronized to apply Doppler corrections associated with said node's own motions relative to a common reference frame. The common reference frame may be known to the transmitter node and the receiver node prior to the transmitter node transmitting signals to the receiver node and prior to the receiver node receiving the signals from the transmitter node. The receiver node may be configured to be in a state of reduced emissions.
1. A system, comprising:
a transmitter node and a receiver node, wherein each node of the transmitter node and the receiver node comprises:
a communications interface including at least one antenna element; and
a controller operatively coupled to the communications interface, the controller including one or more processors, wherein the controller has information of own node velocity and own node orientation;
wherein each node of the transmitter node and the receiver node are in motion relative to each other,
wherein each node of the transmitter node and the receiver node are time synchronized to apply Doppler corrections associated with said node's own motions relative to a common reference frame,
wherein the common reference frame is known to the transmitter node and the receiver node prior to the transmitter node transmitting signals to the receiver node and prior to the receiver node receiving the signals from the transmitter node,
wherein the receiver node is configured to be in a state of reduced emissions.
2. The system of claim 1 , wherein the state of reduced emissions includes at least one of: a state of radio silence or a state of emissions control (EMCON).
3. The system of claim 1 , wherein the signals transmitted by the transmitter node to the receiver node include low probability of detection (LPD) signals.
4. The system of claim 1 , wherein the common reference frame is a common inertial reference frame.
5. The system of claim 1 , wherein the receiver node is configured to adjust a receiver frequency of the receiver node according to an own speed and an own velocity direction of the receiver node so as to perform a receiver-side Doppler correction.
6. The system of claim 5 , wherein an amount of adjustment of an adjusted transmit frequency is proportional to a transmitter node velocity projection onto a Doppler null direction, wherein an amount of adjustment of the receiver frequency is proportional to a receiver node velocity projection onto the Doppler null direction.
7. The system of claim 6 , wherein the receiver node is configured to determine a relative speed between the transmitter node and the receiver node.
8. The system of claim 7 , wherein the receiver node is configured to determine a direction that the transmitter node is in motion and a velocity vector of the transmitter node.
9. The system of claim 8 , wherein a maximum net frequency shift for a Doppler correction by the receiver node occurs when a resultant vector is parallel to the Doppler null direction, wherein the resultant vector is equal to a velocity vector of the receiver node minus the velocity vector of the transmitter node.
10. The system of claim 8 , wherein a minimum net frequency shift for a Doppler correction by the receiver node occurs when a resultant vector is antiparallel to the Doppler null direction, wherein the resultant vector is equal to a velocity vector of the receiver node minus the velocity vector of the transmitter node.
11. The system of claim 8 , wherein a net frequency shift for a Doppler correction by the receiver node is zero when a vector pointing to the receiver node from the transmitter node is parallel to the Doppler null direction.
12. The system of claim 1 , wherein the transmitter node and the receiver node are time synchronized via synchronization bits associated with acquisition.
13. The system of claim 12 , wherein the synchronization bits operate as physical layer overhead.
14. The system of claim 1 , wherein each node of the transmitter node and the receiver node are in motion in three dimensions.
15. The system of claim 1 , wherein each node of the transmitter node and the receiver node are in motion in two dimensions.
16. The system of claim 1 , wherein the system is a mobile ad-hoc network (MANET) comprising the transmitter node and the receiver node.
17. A method, comprising:
providing a transmitter node and a receiver node, wherein each node of the transmitter node and the receiver node are time synchronized, wherein each node of the transmitter node and the receiver node are in motion relative to each other, wherein each node of the transmitter node and the receiver node comprises a communications interface including at least one antenna element, wherein each node of the transmitter node and the receiver node further comprises a controller operatively coupled to the communications interface, the controller including one or more processors, wherein the controller has information of own node velocity and own node orientation;
based at least on the time synchronization, applying, by the transmitter node, Doppler corrections to the transmitter node's own motions relative to a common reference frame; and
based at least on the time synchronization, applying, by the receiver node, Doppler corrections to the receiver node's own motions relative to the common reference frame;
wherein the common reference frame is known to the transmitter node and the receiver node prior to the transmitter node transmitting signals to the receiver node and prior to the receiver node receiving the signals from the transmitter node,
wherein the receiver node is configured to be in a state of reduced emissions.
18. The method of claim 17 , wherein the state of reduced emissions includes at least one of: a state of radio silence or a state of emissions control (EMCON).
19. The method of claim 17 , wherein the signals transmitted by the transmitter node to the receiver node include low probability of detection (LPD) signals.
20. The method of claim 17 , further comprising:
adjusting, by the receiver node, a receiver frequency of the receiver node according to an own speed and an own velocity direction of the receiver node so as to perform a receiver-side Doppler correction;
determining, by the receiver node, a relative speed between the transmitter node and the receiver node; and
determining, by the receiver node, a direction that the transmitter node is in motion and a velocity vector of the transmitter node,
wherein an amount of adjustment of an adjusted transmit frequency is proportional to a transmitter node velocity projection onto a Doppler null direction, wherein the amount of the adjustment of the receiver frequency is proportional to a receiver node velocity projection onto the Doppler null direction.