Systems and methods for quantum key distribution using orbital angular momentum (OAM)-modes-enabled secure multidimensional coded modulation. The quantum key distribution including symbols of a raw key across subcarriers and multiplexing the subcarriers to form an electrical carrier. Then optically modulating the electrical carrier with an electro-optical modulator using an optical signal. The optically modulated electrical carrier is then imposed on a pre-determined OAM mode using an optical OAM multiplexer, attenuated, and transmitted across a quantum channel. A receiver then receives the transmitted signal and demultiplexes it with an optical OAM demultiplexer to extract projections. The projections then undergo optical-to-electrical conversion using a coherent optical detector with an optical signal from a local oscillator. A resulting estimated electrical carrier is then demultiplexed into subcarriers. The subcarrier undergo phase noise cancellation and subsequent demodulation to extract estimated symbol constellation points corresponding the symbols of the raw key.

A Radio Network Node (RNN) 110 and a method therein for improving capacity in a wireless communications system 100. The RNN is configured to serve a first wireless device 120 and a second wireless device (WD) 130. The RNN assigns a shared uplink pilot signal to the first and second WDs. Further, the RNN transmits, to the first WD, an indication of how possible second data intended for the second WD will be comprised in a signal to be transmitted to the first WD. Furthermore, the RNN estimates a combined channel based on a received shared uplink pilot signal from the first WD and/or the second WD. Yet further, the RNN determines a beamforming vector for the estimated combined channel; and transmits the signal to the first WD, wherein the signal comprises first data and the possible second data, which first data is decodable only by the first WD.

A simple construction for a family of non-uniform APSK constellations by the radial isomorphism between squares to circles is provided. The mutual information values indicate gains of at least 0.5 dB up to 1.5 dB with respect to the state of the art, such as the DVB-S2X constellations with 256 symbols. The invention also provides for a low-complexity detector of high-order modulated signals.

Transmitting apparatus and receiving apparatus for communication systems using coded orthogonal frequency-division multiplexed (COFDM) dual-subcarrier modulation (DCM) signals. The same coded data is mapped both to COFDM subcarriers located in the lower-frequency half spectrum of the DCM signal and to COFDM subcarriers located in its upper-frequency half spectrum. The mapping of COFDM subcarriers in those half spectra employ labeling diversity preferred for reception of DCM with less error when accompanied by interfering additive white Gaussian noise (AWGN). In preferred forms of COFDM DCM signal, the quadrature amplitude modulation (QAM) of COFDM subcarriers is Gray mapped to position palindromic lattice-point labels along one of the diagonals of each square QAM constellation.

Systems and methods for orbital angular momentum (OAM)-based multidimensional signaling with multiple-input-multiple-output (MIMO). The wireless communication is achieved using a transmitter including a plurality of orthogonal pulse shapers of a multidimensional modulator, the plurality of orthogonal pulse shapers generating a multidimensional modulated signal by imposing one or more data sequences on corresponding mutually orthogonal filter impulse responses derived from multiple orthogonal basis functions including Slepian sequences. An OAM antenna array including OAM antenna elements is used such that each of the OAM antenna elements includes an azimuthal phase shifter for shifting an azimuthal phase term of a wavefront generated by an antenna element such that the OAM antenna elements impose the multidimensional modulated signal on pre-determined OAM modes of a carrier signal corresponding to the azimuthal phase term.

A space time labelling technique for wireless communication systems is provided. A transmitter for implementing the technique includes a first bit mapper and a second bit mapper which is different to the first bit mapper and first and second transmitters. A processor is connected to the first and second mappers and the first and second transmitters and controls these to receive two bit streams and simultaneously feed these into the first mapper and the second mapper. The first mapper maps these into first and second mapped bit streams and the second mapper maps these into third and fourth mapped bit streams which are different from the first and second mapper bit streams. The first mapped bit stream is transmitted in a first time slot via the first transmitter and the second mapped bit stream is transmitted in the first time slot via the second transmitter. The third mapped bit stream is transmitted in a second time slot via the second transmitter and finally the fourth mapped bit stream is transmitted in a second time slot via the first transmitter.

Systems and methods for orbital angular momentum (OAM)-based multidimensional signaling with multiple-input-multiple-output (MIMO). The wireless communication is achieved using a transmitter including a plurality of orthogonal pulse shapers of a multidimensional modulator, the plurality of orthogonal pulse shapers generating a multidimensional modulated signal by imposing one or more data sequences on corresponding mutually orthogonal filter impulse responses derived from multiple orthogonal basis functions including Slepian sequences. An OAM antenna array including OAM antenna elements is used such that each of the OAM antenna elements includes an azimuthal phase shifter for shifting an azimuthal phase term of a wavefront generated by an antenna element such that the OAM antenna elements impose the multidimensional modulated signal on pre-determined OAM modes of a carrier signal corresponding to the azimuthal phase term.

Systems and methods for quantum key distribution using orbital angular momentum (OAM)-modes-enabled secure multidimensional coded modulation. The quantum key distribution including symbols of a raw key across subcarriers and multiplexing the subcarriers to form an electrical carrier. Then optically modulating the electrical carrier with an electro-optical modulator using an optical signal. The optically modulated electrical carrier is then imposed on a pre-determined OAM mode using an optical OAM multiplexer, attenuated, and transmitted across a quantum channel. A receiver then receives the transmitted signal and demultiplexes it with an optical OAM demultiplexer to extract projections. The projections then undergo optical-to-electrical conversion using a coherent optical detector with an optical signal from a local oscillator. A resulting estimated electrical carrier is then demultiplexed into subcarriers. The subcarrier undergo phase noise cancellation and subsequent demodulation to extract estimated symbol constellation points corresponding the symbols of the raw key.

Systems and methods for orbital angular momentum (OAM)-based multidimensional wireless communication. The OAM-based multidimensional wireless communication is preformed with a transmitter for generating an RF modulated signal carrying a data sequence. Further included is an OAM antenna array including OAM antenna elements, each of which includes an azimuthal phase shifter and an antenna element. The azimuthal phase shifter shifts an azimuthal phase term of a wavefront generated by the antenna element such that the OAM antenna element imposes the multidimensional modulated signal on a pre-determined OAM mode of a carrier signal corresponding to the azimuthal phase term.

A space time labelling technique for wireless communication systems is provided. A transmitter for implementing the technique includes a first bit mapper and a second bit mapper which is different to the first bit mapper and first and second transmitters. A processor is connected to the first and second mappers and the first and second transmitters and controls these to receive two bit streams and simultaneously feed these into the first mapper and the second mapper. The first mapper maps these into first and second mapped bit streams and the second mapper maps these into third and fourth mapped bit streams which are different from the first and second mapper bit streams. The first mapped bit stream is transmitted in a first time slot via the first transmitter and the second mapped bit stream is transmitted in the first time slot via the second transmitter. The third mapped bit stream is transmitted in a second time slot via the second transmitter and finally the fourth mapped bit stream is transmitted in a second time slot via the first transmitter.