Directional enhancements for mobile ad hoc networks (MANET) via doppler null scanning (DNS)
A system is disclosed. The system may be a directional communications network (e.g., MANET) including at least a receiver or transmitter node. The receiver or transmitter node may include a communications interface with an omnidirectional antenna element and a controller. The controller may include one or more processors and have information of own node velocity and own node orientation relative to a common reference frame known to the receiver or transmitter node prior to the receiver or transmitter node receiving signals from a source. The receiver or transmitter node may be time synchronized to apply Doppler corrections associated with the receiver or transmitter node's own motions relative to the common reference frame. The transmitter and receiver nodes may exchange medium access control (MAC) packets prior to establishing directional communications links, determining bearings to each other via Doppler corrections with respect to the packet exchanges.
1 . A system, comprising:
at least two nodes including a transmitter (Tx) node and a receiver (Rx) node, wherein each node comprises:
a communications interface including at least one omnidirectional 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 is in motion relative to each other and to a common reference frame;
wherein each node is time synchronized to apply Doppler corrections associated with the motion of said node relative to the common reference frame;
wherein the common reference frame is known to each node prior to the Tx node transmitting signals to the Rx node and prior to the Rx node receiving the signals from the Tx node;
wherein at least the Rx node is configured to:
receive at least one first control message transmitted by the Tx node, the first control message associated with a directional communications link from the Tx node to the Rx node;
determine a bearing from the Rx node to the Tx node based on one or more Doppler corrections associated with the first control message;
establish a directional communication link to the Tx node based on the determined bearing;
and
transmit at least one second control message in response to the received first control message.
2 . The system of claim 1 , wherein:
the at least one first control message includes at least one Request to Tune (RTT);
and
the at least one second control message includes at least one Response to Tune.
3 . The system of claim 1 , wherein:
the at least one first control message includes at least one Request to Send (RTS);
and
the at least one second control message includes at least one Clear to Send (CTS).
4 . The system of claim 1 , wherein the Tx node is configured to:
determine a bearing to the Rx node based on Doppler corrections associated with the received second control message;
and
establish the directional communications link to the Rx node based on the determined bearing.
5 . The system of claim 4 , wherein the Tx node is further configured to determine a range from the Tx node to the Rx node.
6 . The system of claim 1 , wherein the at least two nodes further comprise:
at least a first additional node and a second additional node configured to determine, based on at least one of the first control message, the second control message, or the one or more Doppler corrections:
a first bearing to the Tx node;
a second bearing to the Rx node;
and
at least one third bearing between the first and second additional nodes based on the one or more Doppler corrections.
7 . The system of claim 6 , wherein the first and second additional nodes are configured to establish mutual directional communications links based on the at least one third bearing.
8 . The system of claim 7 , wherein:
the directional communications links between the Tx and Rx nodes are associated with at least one frequency band;
and
the mutual directional communications links established between the first and second additional nodes are associated with the at least one frequency band.
9 . The system of claim 1 , wherein:
the Tx node has at least one first directional communications link to a silent node of the two or more nodes, the silent node associated with at least one of a state of reduced emissions or a state of radio silence;
the Tx node has at least one second directional communications link to an additional node of the two or more nodes;
and
the Tx node is configured to relay one or more transmissions between the silent node and the additional node via the first directional communications link.
10 . The system of claim 1 , wherein the Rx node is further configured to determine a range from the Rx node to the Tx node.
11 . The system of claim 1 , wherein the Rx node is configured to adjust a receiver frequency of the Rx node according to an own speed and an own velocity direction of the Rx node so as to perform a receiver-side Doppler correction.
12 . The system of claim 11 , wherein an amount of adjustment of the adjusted receiver frequency is proportional to an Rx node velocity projection onto a Doppler null direction.
13 . The system of claim 12 , wherein the Rx node is configured to determine a relative speed between the Tx node and the Rx node.
14 . The system of claim 13 , wherein the Rx node is configured to determine a direction that the Tx node is in motion and a velocity vector of the Tx node.
15 . The system of claim 14 , wherein a maximum net frequency shift for a Doppler correction by the Rx node occurs when a resultant vector is parallel to a Doppler null direction, wherein the resultant vector is equal to a velocity vector of the Rx node minus the velocity vector of the Tx node.
16 . The system of claim 14 , wherein a minimum net frequency shift for a Doppler correction by the Rx node occurs when a resultant vector is antiparallel to a Doppler null direction, wherein the resultant vector is equal to a velocity vector of the Rx node minus the velocity vector of the Tx node.
17 . The system of claim 1 , wherein each node of the Tx node and the Rx node are in relative motion in two or three dimensions.