Abstract: A central node of a MIMO system may transmit, to one or more communication terminals of the MIMO system, a long-duration downlink pilot signal carrying a pilot sequence having a first duration. The first duration may be equal to or greater than a quantity of antennas of the central node. The central node may receive retransmitted long-duration downlink pilot signals from the communication terminals. The central node may further transmit, to one or more communication terminals, a short-duration downlink pilot signal carrying a pilot sequence having a second duration. The second duration may be less than or equal to the quantity of antennas. The central node may receive a retransmitted short-duration downlink pilot signal from the one or more communication terminals. An uplink and downlink between the central node and one or more communication terminals may be estimated based on the received signals.

Abstract: A central node may include a processor configured to empirically compute an approximation of power coefficients based on estimates of the channel coefficients such that a same one of the approximation of the power coefficient is assigned to each of a plurality of access terminals (ATs), and transmit components of a signal vector to associated access points (APs), the signal vector being based on at least the approximation of the power coefficient.

Abstract: A central node may include a processor configured to empirically compute an approximation of power coefficients based on estimates of the channel coefficients such that a same one of the approximation of the power coefficient is assigned to each of a plurality of access terminals (ATs), and transmit components of a signal vector to associated access points (APs), the signal vector being based on at least the approximation of the power coefficient.

Abstract: A central node of a MIMO system may transmit, to one or more communication terminals of the MIMO system, a long-duration downlink pilot signal carrying a pilot sequence having a first duration. The first duration may be equal to or greater than a quantity of antennas of the central node. The central node may receive retransmitted long-duration downlink pilot signals from the communication terminals. The central node may further transmit, to one or more communication terminals, a short-duration downlink pilot signal carrying a pilot sequence having a second duration. The second duration may be less than or equal to the quantity of antennas. The central node may receive a retransmitted short-duration downlink pilot signal from the one or more communication terminals. An uplink and downlink between the central node and one or more communication terminals may be estimated based on the received signals.

Abstract: A base station servicing a cell of a cellular network provides power control of a cell independent of any other cell in the network. For downlink power control, the base station transmits information at its full power and applies a downlink power control factor to each downlink channel to equalize downlink throughputs of the mobile terminals in the cell. For uplink power control, the base station transmits instructions to have the uplink channel with the worst channel condition to transmit at its full power and the other uplink channels to transmit at that same full power. Each transmission is scaled by a corresponding uplink power control factor such that uplink throughputs for the mobile terminals in the cell are equalized. The base station applies an approximation of a rigorous capacity lower bound algorithm using propagation channel conditions and channel parameters to calculate the uplink and downlink power control factors.

Abstract: A base station servicing a cell of a cellular network provides power control of a cell independent of any other cell in the network. For downlink power control, the base station transmits information at its full power and applies a downlink power control factor to each downlink channel to equalize downlink throughputs of the mobile terminals in the cell. For uplink power control, the base station transmits instructions to have the uplink channel with the worst channel condition to transmit at its full power and the other uplink channels to transmit at that same full power. Each transmission is scaled by a corresponding uplink power control factor such that uplink throughputs for the mobile terminals in the cell are equalized. The base station applies an approximation of a rigorous capacity lower bound algorithm using propagation channel conditions and channel parameters to calculate the uplink and downlink power control factors.

Abstract: A multiple-input, multiple-output (MIMO) communication system is configured to utilize a variable slot structure. The system includes multiple terminals and at least one base station configured to communicate with the terminals. The base station is operative to determine mobilities for respective ones of the terminals, to arrange the terminals into groups based on the determined mobilities, and to utilize at least first and second different slot structures for communicating with the terminals of at least respective first and second ones of the groups. The system may be, for example, a multi-user MIMO system in which the multiple terminals comprise autonomous single-antenna terminals.

Abstract: A method is provided to reduce inter-cell interference in mobile wireless systems, and particularly in TDD wireless systems. In an embodiment, a base station receives a pilot signal from at least one of the mobile terminals that it serves at a plurality of base station antennas, which include both main antennas and auxiliary antennas. In response, each of the base station antennas provides an output that is processed to obtain a set of precoding weights for a transmission from the main antennas. The processing includes nulling at least one interfering signal using the outputs from at least the auxiliary antennas.

Abstract: A construction is provided for uplink pilot signals in a cellular network. Three sets of pilot signals are defined, having orthogonality properties that lead to reduced inter-cell interference. In example embodiments, the network has a reuse factor of 3 for pilot signals, with sets U, V, and W of pilot signals assigned to cells in respective reuse classes. The pilots of each set form an orthogonal basis. Some pilots of each class, i.e. those which will generally be assigned to mobile stations near the cell edges, will also form an orthogonal basis with some pilots of each of the other classes.

Abstract: A method is provided to reduce inter-cell interference in mobile wireless systems, and particularly in TDD wireless systems. In an embodiment, a base station receives a pilot signal from at least one of the mobile terminals that it serves at a plurality of base station antennas, which include both main antennas and auxiliary antennas. In response, each of the base station antennas provides an output that is processed to obtain a set of precoding weights for a transmission from the main antennas. The processing includes nulling at least one interfering signal using the outputs from at least the auxiliary antennas.

Abstract: A construction is provided for uplink pilot signals in a cellular network. Three sets of pilot signals are defined, having orthogonality properties that lead to reduced inter-cell interference. In example embodiments, the network has a reuse factor of 3 for pilot signals, with sets U, V, and W of pilot signals assigned to cells in respective reuse classes. The pilots of each set form an orthogonal basis. Some pilots of each class, i.e. those which will generally be assigned to mobile stations near the cell edges, will also form an orthogonal basis with some pilots of each of the other classes.

Abstract: A security mechanism is provided for wireless power transfer applications including resonant source and device objects, wherein tuned resonance between source and device objects is necessary for efficient power transfer. Tuning parameters associated with the source object are periodically adjusted so as to require corresponding changes in tuning parameter(s) of the device object to maintain tuned resonance. The tuning parameters are communicated to authorized users such that only authorized users capable of matching the changes made by the transmitter would be capable of receiving power. Unauthorized users that are unaware of the transmit tuning parameters will be rendered unable to maintain tuned resonance and thus unable to receive power.

Abstract: A method for transmitting a sequence of data blocks of equal length includes obtaining part of a matrix for the impulse response function of a communication channel between a transmitter and a receiver. The part relating to channel-induced interference between sampling intervals of adjacent ones of the data blocks. The method includes designing a set of one or more linearly independent waveforms based on the obtained part of the matrix for the impulse response function and transmitting a sequence of the data blocks over the channel from the transmitter to the receiver. Each data block of the sequence is a weighted linear superposition of the one or more waveforms of the designed set.

Abstract: A multiple-input, multiple-output (MIMO) communication system is configured to utilize a variable slot structure. The system includes multiple terminals and at least one base station configured to communicate with the terminals. The base station is operative to determine mobilities for respective ones of the terminals, to arrange the terminals into groups based on the determined mobilities, and to utilize at least first and second different slot structures for communicating with the terminals of at least respective first and second ones of the groups. The system may be, for example, a multi-user MIMO system in which the multiple terminals comprise autonomous single-antenna terminals.

Abstract: Training is performed to characterize one or more communication channels between a first communication unit (CU) and one or more additional CUs. Channel characteristic(s) are determined by using first training signals received by the first CU from one of the additional CUs. Second training signals, defined at least in part by the channel characteristic(s), are determined. The channel characteristic(s) may comprise a unitary factor and power levels for subchannels. The second training signals are transmitted from the first CU to the one additional CU, which not only determines characteristics of the channel but also usually determines scheduling information. Each CU independently determines communication rates on subchannels. Typically, the two communication rates will be in agreement. The one additional CU sends modified training signals so that the first CU lowers the communication rate on subchannels.

Abstract: A method is disclosed for generating unitary space-time signals for wireless communication using an array of M transmitting antennas. Each unitary space-time signal comprises T symbols. The method can be used to generate arbitrarily large signal constellations. The resulting unitary space-time signals have statistical properties that are favorable for reliable use in communication, and they can lead to very high data transmission rates. The disclosed method involves the mapping of binary strings of data to matrix products of the kind obtained by left-multiplying an initial T×M matrix by an ordered multiplicative sequence of exponentiated T×T unitary matrices, referred to as generator matrices. The result of each such multiplication is a unitary space-time signal matrix that may be transmitted. Each generator matrix corresponds to a single bit or a collection of bits of a binary string that is to be mapped.

Abstract: We describe a method for CDMA transmission of sets of data symbols to users that are organized into one or more user groups. Each user group is paired with a group of spreading codes, referred to as a “code group.” Each set of data symbols that are destined for respective users of a given user group is transmitted in the form of two or more distinct signal sequences. Each such signal sequence is transmitted from a respective one of two or more transmitting antennas. Each signal sequence is a linear combination of spreading code sequences belonging to the corresponding code group. Within each of these linear combinations, each spreading code sequence that appears has a scalar coefficient. Each of these scalar coefficients is a linear combination of pertinent data symbols (i.e., data symbols destined for users in the given user group) or of complex conjugates of pertinent data symbols.

Abstract: Messages according to a method of wireless signal transmission are sent as sequences of unitary space-time signals. Each signal is representable as a matrix in which each column represents a respective transmitting antenna of a transmitting array, and each row represents a time segment. Each such matrix is proportional to a complex-valued matrix, all columns of which are mutually orthonormal. A new method for creating a constellation of signal matrices comprises providing an initial signal in the form of a complex, orthonormal matrix. The method further comprises generating a further plurality of matrices by a process that assures that each of the generated matrices is related to the initial matrix as a product of one or more multiplications of the initial matrix by one or more unitary matrices.

Abstract: In a system for sending wireless communication signals on at least one downlink wavelength and receiving wireless communication signals on at least one uplink wavelength, there is a ratio r equal to the larger divided by the smaller of these wavelengths. The system comprises a receiver operative to receive signals imposed on a carrier having the uplink wavelength, a transmitter operative to transmit signals imposed on a carrier having the downlink wavelength, and an array of independent antenna elements. The array comprises a first and a second sub-array. One sub-array is electrically coupled to the transmitter, such that transmitted signals can be radiated from it, and the other sub-array is electrically coupled to the receiver, such that signals to be received can be extracted from it. The sub-arrays are geometrically similar to each other with a relative scale factor equal to the wavelength ratio r. The sub-arrays have at least one common antenna element.

Abstract: Disclosed is a modulation method for wireless signal transmission. Each message that is transmitted is made up of a sequence of signals, each selected from a constellation of L such signals, L a positive integer. Each transmitted signal is distributed spatially across a transmitting antenna array, and is also distributed in time. Thus, each signal may be represented as a T×M matrix, in which each of the M columns represents a distinct antenna of the array, and each of the T rows represents a distinct time interval. Each entry in this matrix represents a complex baseband voltage amplitude. Each of these signal matrices is proportional to a matrix having orthonormal columns.