A securely pre-coded orthogonal frequency division multiplexing (SP-OFDM) system includes a transmitter configured to transmit a secure transmit signal through a dynamic constellation and a receiver configured to recover the original signal from the received secure transmit signal. It is aimed to reinforce the physical layer security of wireless communications under hostile interference. Potential applications include 4G and 5G communication systems, ASTC3.0 HDTV systems, WiFi systems, and any future wireless systems that utilize OFDM.

A weight switching unit outputs weights for modulation signals so that, on a constellation diagram in the complex plane, a position of a signal point in a communication direction corresponds to that of the modulation symbol, and the position of the signal point in a non-communication direction becomes different from that of the signal point in the communication direction. Weight applying units apply, to the modulation signals emitted from antennas, weights for each modulation symbol output from the weight switching unit.

A weight switching unit outputs weights for modulation signals so that, on a constellation diagram in the complex plane, a position of a signal point in a communication direction corresponds to that of the modulation symbol, and the position of the signal point in a non-communication direction becomes different from that of the signal point in the communication direction. Weight applying units apply, to the modulation signals emitted from antennas, weights for each modulation symbol output from the weight switching unit.

A random phase modulation method depending on a communication distance is provided. In the method, time synchronization is carried out by means of a transmitter and a receiver, a local random signal is generated, and an original signal to be sent is pre-coded according to a transmission delay and the generated local random signal, such that random phase modulation depending on a communication distance is realized, potential security brought about by positions of the transmitter and the receiver is fully utilized, a receiver at an expected distance position can receive a signal with a correct phase, and a receiver at another distance position receives a signal with a scrambled phase, thereby improving the secure communication capability of a wireless communication system in terms of the dimension of space.

In one embodiment, a method includes receiving, by a network controller and from a first node of a network, information associated with a data stream of the network and determining, by the network controller, a segmentation for the data stream. The segmentation includes a plurality of data segments and the plurality of data segments includes a first data segment. The method further includes determining, by the network controller, a data flow path for each of the plurality of data segments and determining, by the network controller, a first wavelength to assign to the first data segment. The first wavelength is one of a plurality of wavelengths spanning between the first node and a second node of the network.

The application is generally directed to transmitting and receiving signals in a fashion that can mask the presence of the signals by including timing information in the signals using artifacts in a carrier signal. For example, one embodiment includes a method of transmitting a signal in a way to mask the presence of the signal or to reduce the ability of external entities to extract data from the signal. The method includes accessing a data signal. A phase of the data signal is correlated to a phase of a substantially continuous carrier signal carrying the data signal. The substantially continuous carrier signal carrying the data signal with the phase of the data signal correlated to the phase of the substantially continuous carrier signal is transmitted to a receiver, such that the data signal can be extracted by using phase correlation between the data signal and the substantially continuous carrier signal.

Certain aspects provide a method for radar detection by an apparatus. The method including transmitting a radar waveform in transmission time intervals (TTIs) to perform detection of a target object. The method further includes varying the radar waveform across TTIs based on one or more radar transmission parameters.

Disclosed is a secure scheme that incorporates both internal and external eavesdroppers to secure all users' links in the downlink PD-NOMA. In particular, the proposed scheme implies that the BS induces a phase shift in each user's symbol based on its corresponding instantaneous channel phase. The phase shift of each user is restricted such that the original symbol is moved to the location of another symbol in the constellation diagram. Therefore, as each user is aware of its instantaneous channel phase only, it will be able to recover the actual phase of its corresponding symbol. Thus, the proposed scheme does not only protect the data against eavesdroppers, but it also guarantees confidentiality and privacy against all other users.

Quantum key distribution device includes a transmitter, including a light source, a first polarization controller, a phase modulator and an optical attenuator, all connected in series using a first optical fiber; a receiver, including a second polarization controller, a second phase modulator, a third polarization controller, a beamsplitter, and two single photon detectors, all connected in series using a second optical fiber; and a communication channel providing a light path from the transmitter to the receiver. The first and/or second optical fiber is a polarization maintaining fiber. The first and second phase modulators are actively controlled Pockels cell crystals, lithium niobate crystals or gallium arsenide crystals. The polarization controllers include a piezo-driven fiber compression device, a Pockels cell controller, a piezo-driven fiber twist device, or a non-linear optical crystal. The first and third polarization controllers use a /2 plate, or 45 fiber splice polarizer.

The concepts, systems and methods described herein are directed towards encrypting optical signals prior to the optical signals being sensed, for example, by a sensor. An optical phased array (OPA) may be disposed between an optical chain and a sensor to encrypt an optical signal being sensed before the signal is received at the sensor. The method includes receiving an optical signal having a plurality of beams organized in a first arrangement at an optical phased array, encrypting the optical signal in the optical phased array by steering or otherwise phase shifting the plurality of beams from the first arrangement to a second arrangement, transmitting the plurality of beams in the second arrangement from the optical phased array to a sensor and sensing the encrypted optical signal having the plurality of beams in the second arrangement at the sensor.