Abstract: An adaptive method for channel assignment in a cellular multiple access wireless communication system that has a cell station (CS) and a number of subscriber stations augments existing channel assignment protocol and thus is downward compatible with existing time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA), and spatial division multiple access (SDMA) system protocols. The method adaptively determines the power required for establishing an acceptable quality connection between a subscriber station and the cell station and provides an early warning trial signal for advising existing connections that a new connection is about to be established. The early warning, followed by a pause, provides a basis and a time interval for taking corrective interference action if the trial signal indicates that an unacceptable level of interference will result if the trial connection is established.

Abstract: A method operating in a communications station for calibrating the communications station, the communications station including an antenna array of antenna elements, each having associated with it and included in a transmit apparatus chain and a receiver apparatus chain. The method comprises transmitting a prescribed signal from each antenna element using the transmit apparatus chain associated with the antenna element while receiving the transmitted signal in receiver apparatus chains not associated with the antenna. Calibration factors for each antenna element are determined as dependent on the associated transmit apparatus chain and receiver apparatus chain transfer functions using the prescribed signal and each of the signals received during transmissions.

Abstract: An RF-signal combiner-splitter comprises a microwave cavity that is intended to mix together radio signals in the 2.0 GHz spectrum. A hollow cylindrical metal tube with a volume of a few cubic feet to a few cubic yards is closed at one end and open at the other. Many RF-ports into the microwave cavity are provided at random positions that penetrate the hollow cylindrical metal tube. For example BNC-type bulkhead connectors with 10 dB attenuator pads are used with a 2 to 3 inch whip antenna inside the cavity volume. The attenuator pads brute-force an impedance match between the radio equipment under test and their corresponding RF-ports. The open end of the hollow cylindrical metal tube allows for the quick decay of RF-reflections that reverberate inside the cavity volume. Such open end is preferably directed toward nadir because interfering signals are generally minimum from that direction.

Abstract: A method and apparatus for estimating the parameters of a wireless communication system which includes at least one base station and at least one remote terminal, each of the base stations having m antenna elements, the parameters being one or more of: the time alignment; the frequency offset; and the weight vector for spatial processing. At any stage, some of the parameters may already be estimated. A signal of known characteristics is transmitted and received as m received signals at the antenna elements. A cost function that is related to the at least one or more parameters of the second set is determined using a copy signal determined from samples of the received signals, estimates of one or more parameters, if available, known characteristics of transmitted first signal. The estimate of the parameters to be determined is obtained by minimizing the cost function.

Abstract: A wireless communication subscriber unit comprises a radio frequency downconversion stage that produces in-phase and quadrature phase digital samples. A digital signal processor is connected to receive the samples and process them to produce a control channel correlation output and a carrier frequency offset estimate. The acquisition of the control channel is made substantially immune from initial carrier frequency offsets by differential sample encoding the samples. These are input to a correlator whose coefficients are a pre-stored differential sample encoded, decimated and rate expanded version of the known reference sequence. When the the reference sequence is present, the correlator produces a peak output that can be used to detect the presence of the reference sequence. The time position of the peak can be used for time alignment, for signal quality estimation, and to directly obtain a frequency offset estimate.

Abstract: A method and apparatus for generating a reference signal for use in an alternating projection loop which is part of demodulation in a base station of a wireless communication system, the reference signal relaxed to minimize the effects of frequency offset and amplitude variations, the base station including an array of antennas. The alternating projection loop demodulates in the presence of co-channel interference and includes correction for time alignment and/or frequency offset.

Abstract: The methods for channel assignment and channel reassignment are suitable for SDMA systems that accommodate the dynamically adaptive spatial channel conditions and allow for more frequent reuse of conventional channels. Three methods for uplink channel assignment are described: a cost function method, a predictive method, and a hierarchical method. The cost function method computes a cost function for each conventional channel based on a weighted correlation matrix of spatial signatures (vectors) of active subscribers. A spatial channel is created for the selected conventional channel if it is in use. The predictive channel assignment method predicts the uplink received power and interference-plus-noise for each conventional channel. Either the conventional channel with the minimum interference-plus-noise level or the channel with the maximal SINR is selected and a spatial channel is also assigned if the selected channel is in use.

Abstract: A wireless system includes a network of base stations for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to said plurality of remote terminals using a plurality of channels. A plurality of antenna elements at each base station receives uplink signals, and a plurality of antenna elements at each base station for transmits downlink signals. A signal processor at each base station is connected to the receiving antenna elements and to the transmitting antenna elements for determining spatio-temporal signatures. Spatio-temporal multiplexing and demultiplexing functions are provided for each remote terminal antennae for each channel, and a multiple base station network controller optimizies network performance, whereby communication between the base stations and the plurality of remote terminals in each of the channels can occur simultaneously.

Abstract: A wireless system comprising a network of base stations for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to the plurality of remote terminals using a plurality of conventional channels including a plurality of antenna elements at each base station for receiving uplink signals, a plurality of antenna elements at each base station for transmitting downlink signals, a signal processor at each base station connected to the receiving antenna elements and to the transmitting antenna elements for determining spatial signatures and multiplexing and demultiplexing functions for each remote terminal antenna for each conventional channel, and a multiple base station network controller for optimizing network performance, whereby communication between the base stations and a plurality of remote terminals in each of the conventional channels can occur simultaneously.

Abstract: A method and apparatus for calibrating antenna array systems comprising of a portable transponder (118) and a calibration processor (124). Calibration processor (124) generates calibration transmit signals which it transmits using transmit signal processor (104) and antenna array (111). Transponder (118) echoes these signals back and they are acquired by calibration processor (124) through antenna array (111) and receive signal processor (106). Calibration processor (124) processes the received signals to calculate antenna calibration vector (102).

Abstract: A method and apparatus for increasing the capacity and quality of wireless communication between a plurality of remote users and a base station is disclosed. Using measurements from an array of receiving antennas at the base station, parameters of multiple signals transmitted to the base station from a plurality of users in the same channel are calculated and used to obtain the positions and velocities of the users. The locations and other related signal parameters are used to calculate appropriate spatial demultiplexing strategies, reconstructing the individual transmitted signals from the receiver measurements and reducing interference to acceptable levels. This heretofore unavailable location information is used in solving the hand-off problem. This information is also used to calculate an appropriate spatial multiplexing strategy for simultaneous transmission of signals to users in the same channel. This can be the same as or distinct from the aforementioned receive channel.