Systems and methods for Doppler frequency shift compensation in free space optical links include a modulator configured to modulate a transmitter laser; a receiver including a Local Oscillator (LO) laser configured to receive a coherent signal; and circuitry configured to tune a frequency of the transmitter laser and the LO laser based on an amount of Doppler frequency shift to be compensated. The systems and methods determine an amount of Doppler shift between a first and second satellite and tune the frequency of the transmitter and LO laser based on the determined amount of Doppler frequency shift.

Diversity receiver front end system with methods for improving signal processing using tunable matching circuits. The methods can include tuning impedance matching circuits based on frequency bands. For a first path, an impedance can be provided that reduces an in-band noise figure, increases an in-band gain, decreases an out-of-band noise figure, and/or decreases an out-of-band gain. In this way, signals propagated along selectively activated paths between an input of a receiving system and an output of the receiving system can be improved. The signals can be amplified using amplifiers disposed on corresponding paths between the input and output of the receiving system.

Diversity receiver front end system with methods for improving signal processing using tunable matching circuits. The methods can include tuning impedance matching circuits based on frequency bands. For a first path, an impedance can be provided that reduces an in-band noise figure, increases an in-band gain, decreases an out-of-band noise figure, and/or decreases an out-of-band gain. In this way, signals propagated along selectively activated paths between an input of a receiving system and an output of the receiving system can be improved. The signals can be amplified using amplifiers disposed on corresponding paths between the input and output of the receiving system.

The disclosed subject matter relates to techniques for determining channel state information (CSI) in New Radio (NR) access communication systems with phase tracking. In one embodiment, a method is provided that comprises receiving, by a device comprising a processer, configuration information from a network device of a wireless communication network indicating that a PTRS protocol has been configured for wireless communications between the device and the network device. The method further comprises, determining, by the device, a resource density of resource elements of the wireless communication network allocated for the phase tracking reference signal protocol, determining, by the device, CSI based on the resource density, and reporting, by the device, the CSI to the network device.

The disclosed subject matter relates to techniques for determining channel state information (CSI) in New Radio (NR) access communication systems with phase tracking. In one embodiment, a method is provided that comprises receiving, by a device comprising a processer, configuration information from a network device of a wireless communication network indicating that a PTRS protocol has been configured for wireless communications between the device and the network device. The method further comprises, determining, by the device, a resource density of resource elements of the wireless communication network allocated for the phase tracking reference signal protocol, determining, by the device, CSI based on the resource density, and reporting, by the device, the CSI to the network device.

A code division multiaccess (CDMA) communications system with low probability of intercept, low probability of detect (LPI/LPD) includes at least one data dictionary stored on a storage device of a sender subsystem and a recipient subsystem. The at least one data dictionary includes at least one data predetermined start time and date, at least one data predetermined end time and date based on a mission length or a predetermined wrap time and date, a CDMA chip rate, and a complex zero-mean independent and identically distributed (iid) sequence where each complex number in the complex zero-mean iid sequence represents a CDMA chip stored on the storage device of the sender subsystem and the recipient subsystem. The system includes a tangible, non-transitory, machine-readable medium comprising machine-executable instructions which, when executed by at least one processor of a machine, cause the at least one processor to: receive a message, convert the message to symbols with corresponding phasors, determine a date and time to send the message, look up a data spreading vector for each corresponding phasor by providing a mutually agreed number of chips per phasor stored on the storage device of the sender subsystem and the recipient subsystem and by matching the date and time the message is to be sent to the at least one data predetermined start time and date and the at least one data predetermined end time and date. Each data spreading vector is multiplied by its corresponding phasor to create a data spread vector for each data spreading vector. The sender subsystem is configured to sequentially transmit each chip of each data spread vector as a signal.

A code division multiaccess (CDMA) communications system with low probability of intercept, low probability of detect (LPI/LPD) includes at least one data dictionary stored on a storage device of a sender subsystem and a recipient subsystem. The at least one data dictionary includes at least one data predetermined start time and date, at least one data predetermined end time and date based on a mission length or a predetermined wrap time and date, a CDMA chip rate, and a complex zero-mean independent and identically distributed (iid) sequence where each complex number in the complex zero-mean iid sequence represents a CDMA chip stored on the storage device of the sender subsystem and the recipient subsystem. The system includes a tangible, non-transitory, machine-readable medium comprising machine-executable instructions which, when executed by at least one processor of a machine, cause the at least one processor to: receive a message, convert the message to symbols with corresponding phasors, determine a date and time to send the message, look up a data spreading vector for each corresponding phasor by providing a mutually agreed number of chips per phasor stored on the storage device of the sender subsystem and the recipient subsystem and by matching the date and time the message is to be sent to the at least one data predetermined start time and date and the at least one data predetermined end time and date. Each data spreading vector is multiplied by its corresponding phasor to create a data spread vector for each data spreading vector. The sender subsystem is configured to sequentially transmit each chip of each data spread vector as a signal.

A wireless communication method includes generating a pilot signal that is represented using a complex exponential signal having a first linear phase in a time dimension and a second linear phase in a frequency dimension; and transmitting the pilot signal over a wireless communication channel using transmission resources that are designated for pilot signal transmission in a legacy transmission network such as a Long Term Evolution (LTE) network.

A wireless communication method includes generating a pilot signal that is represented using a complex exponential signal having a first linear phase in a time dimension and a second linear phase in a frequency dimension; and transmitting the pilot signal over a wireless communication channel using transmission resources that are designated for pilot signal transmission in a legacy transmission network such as a Long Term Evolution (LTE) network.

A method for wireless communication in a reflective environment includes (a) receiving first wireless signals at a first antenna assembly at least partially via a first reflective environment, (b) generating a first electrical signal from a first antenna element of the first antenna assembly in response to the first wireless signals, the first antenna element having a first polarization, (c) generating a second electrical signal from a second antenna element of the first antenna assembly in response to the first wireless signals, the second antenna element having a second polarization different from the first polarization, (d) shifting phase of at least one of the first electrical signal and the second electrical signal, and (e) after shifting phase, combining at least the first electrical signal and the second electrical signal to generate a combined electrical signal.