Abstract: The mobile terminal of the present invention receives signals from the base station which receives the control command from the mobile terminal and executes, on the basis of the control command, the antenna switching transmission diversity. The mobile terminal includes: a reception unit for receiving downward signal from the base station; a downward link estimation unit for estimating the downward link on the basis of the received downward signal; an upward link estimation unit for estimating the upward link on the basis of the received downward signal; a base station estimation unit for estimating a state of the base station on the basis of the outputs from the downward estimation unit and the upward estimation unit; and a demodulator unit for demodulating the received signal on the basis of the output from the base station estimation unit.

Abstract: An apparatus relays a signal transmitted from a specified base station to a mobile station in CDMA wireless telecommunications systems. To this purpose, the apparatus, installed in an area where signals transmitted from a plurality of base stations co-exist or a soft blocking occurs, operates by following the steps of receiving the signal transmitted from a specified base station having smaller number of calls than the other neighboring base stations, filtering a signal within a service frequency band from the received signal, amplifying the filtered signal, adjusting a gain of the amplified signal and finally transmitting the gain-adjusted signal to the mobile station. Accordingly, a pilot pollution phenomenon is removed and an effective call distribution is achieved, so that the efficiency in using system resources can be greatly improved.

Abstract: A method and system for reducing the effects of atmospheric ducting on wireless transmissions, wherein a wireless communication system is comprised of a plurality of base stations having antennas, each base station having a beacon signal transmitter and a beacon signal receiver. Each beacon signal transmitter is configured to transmit a wireless beacon signal to be received by the beacon signal receiver at other, preferably every other, base stations. For each wireless beacon signal, a time delay and a propagation loss is measured. Each measured time delay and propagation loss is compared to an expected time delay and an expected propagation loss corresponding to the wireless beacon signal. The results of the comparison are processed so as to determine a location of atmospheric ducts in the region serviced by the wireless system.

Abstract: The time-of-arrival of the line-of-sight component of a received, or incoming, signal is determined by performing a time/frequency analysis of the incoming signal. The term time/frequency analysis refers to an analysis of the frequency components (i.e. the frequency make-up) of the incoming signal at given instants in time. For example, one form of time/frequency analysis according to the present invention is to compare the frequency make-up of the received signal to the frequency make-up of the transmitted signal. Those points in time in which the frequency make-up of the received signal matches the frequency make-up of the transmitted signal are the instants in time at which a multipath component of the transmitted signal is received. In such a time/frequency analysis, the first-identified component, in time, is assumed to be the line-of-sight component of the transmitted signal.

Abstract: The time-of-arrival of the line-of-sight component of a received, or incoming, signal is determined by performing a time/frequency analysis of the incoming signal. The term time/frequency analysis refers to an analysis of the frequency components (i.e. the frequency make-up) of the incoming signal at given instants in time. For example, one form of time/frequency analysis according to the present invention is to compare the frequency make-up of the received signal to the frequency make-up of the transmitted signal. Those points in time in which the frequency make-up of the received signal matches the frequency make-up of the transmitted signal are the instants in time at which a multipath component of the transmitted signal is received. In such a time/frequency analysis, the first-identified component, in time, is assumed to be the line-of-sight component of the transmitted signal.

Abstract: A method and apparatus of assigning fingers in a rake receiver for incorporation in a receiver of a CDMA communications system is disclosed herein. The method includes measuring the multipath profile of a received spread-spectrum radio-frequency (RF) signal to obtain a sequence of measurements, identifying the best candidate path of the RF signal to demodulate by determining which measurement within the sequence has the highest signal strength, deriving a timing offset for the best candidate path as a function of the measurement for the best candidate path and its adjacent measurements, and assigning a finger processing element to the best candidate path using the derived timing offset. The measurements are taken using a searcher having a predetermined timing resolution (e.g., ½ chip), and the resolution of the timing offset is higher (e.g., ⅛ chip). The best candidate path to demodulate is identified using the measurement having the highest amplitude or correlation function.

Abstract: A system and method for assembling a single data stream from multiple instances of that data stream is described. Data transmitted from a cellular telephone subscriber unit is received by a set of base transceiver stations. Each base transceiver station performs various error detection procedures on segments of the data referred to as frames. These error detection procedures may include CRC check sum verification, Yamamoto metric calculation, re-encoded signal error rate calculation, or a combination thereof. The results of these error detection procedures are placed into a frame quality metric. The frame, frame quality metric, a time stamp and an address are placed into a packet that is transmitted from each base transceiver station to a base station controller which matches packets attempting to transmit the same information using the time stamp and selects one frame from the packets for further processing based on the associated frame quality metric.

Abstract: A method and apparatus for dynamically separating and recovering original signal sources by processing a set of mixed received mixtures and convolution of said signals utilizing differential equations and a computer. The system of the invention enables the blind separation and recovery of an unknown number of signals mixed together in dynamically changing interference environments with very minimal assumption on the original signals. The system of this invention has practical applications to nonmultiplexed media sharing, adaptive interferer rejection, acoustic sensors, acoustic diagnostics, medical diagnostics and instrumentation, speech, voice, language recognition and processing, wired and wireless modulated communication signal receivers, and cellular communications.

Abstract: A novel and improved system and method for assembling a single data stream from multiple instances of that data stream is described. Data transmitted from a cellular telephone subscriber unit is received by a set of base transceiver stations. Each base transceiver station performs various error detection procedures on segments of the data referred to as frames. These error detection procedures may include CRC check sum verification, Yamamoto metric calculation, re-encoded signal error rate calculation, or a combination thereof. The results of these error detection procedures are placed into a frame quality metric. The frame, frame quality metric, a time stamp and an address are placed into a packet that is transmitted from each base transceiver station to a base station controller which matches packets attempting to transmit the same information using the time stamp and selects one frame from the packets for further processing based on the associated frame quality metric.

Abstract: A coherent detection type OFDM receiver is disclosed. The coherent detection type OFDM receiver demodulates a digital data sequence. The OFDM receiver obtains a channel frequency response with a frequency spectrum of a received signal and a frequency spectrum of a reference signal. The channel frequency response is filtered in the frequency domain by a filter. At this point, the OFDM receiver estimates delay time of a received delayed signal and designates the bandwidth of the filter with the estimated result. The OFDM receiver compensates the distortion of the waveform of the received signal with the channel frequency response that has been filtered by the filter and demodulates a digital data sequence with the received waveform that has been compensated.

Abstract: A method and system for rejecting interfering signals in a wireless communication system employing antenna diversity. According to the method, the angle between an interfering signal and a desired carrier signal is determined and used to estimate an offset angle. The offset angle is incrementally adjusted such that, when added to the received signal, the carrier-to-interference (C/I) ratio of the received signal is substantially maximized.

Abstract: A method and apparatus for evaluating signal strength of a channel received at a mobile station within a spread spectrum communication systems is disclosed. If the receiver at the mobile station receives a spread spectrum signal, a first sampling means converts the received signal into a first sample stream as a first sampling. A second sampling means converts the first sample stream into a second sample stream at a second sample rate, different from the first sample rate. The signal strength of a pilot channel is measured based upon the first and second sample streams.

Abstract: A SONAD (110) control system (100) detects a received signal strength (RSSI) for a radio frequency (RF) signal (102), selects a threshold transfer function (400-404) in response thereto, generates a threshold control signal in response to the transfer function, and utilizes the threshold control signal to select the SONAD threshold value. During operation, the control system (100) decreases the attenuation of background noise levels for weak RF signals.

Abstract: A fading compensation apparatus and method are provided in which blocks of the analog AM signal (e.g., voice) are time-compressed at a transmitter. Gaps in the time-compressed signal are filled with pilot symbols (or similar complex waveforms) having known characteristics, such as predetermined amplitudes. The time-compressed analog AM signal (e.g., SSB or VSB) is transmitted over the fading channel. At an analog AM receiver, an estimate of the fading that occurred in the transmission channel is made by observing the amplitude of the received pilot symbols at discrete points in time, and interpolating to determine the amount of fading that occurred across the total transmitted signal. A fading compensator compares the received faded time-compressed signal with the interpolation results, and adjusts the amplitude and phase of the received signal accordingly to compensate for the fading that occurred in the transmission channel. The compensated analog AM signal is time expanded and output to a user.

Abstract: A wideband receiver, including a time-varying finite impulse response (FIR) filter, has been provided to combine multipath communications of data in response to pilot channel timing information. The time-varying FIR processes the multipath communications through independent signal paths. Each signal path includes a variable delay circuit and a variable gain circuit. The delay of each separate signal path is adjusted and made equal in response to the pilot channel timing information. Likewise, the gain of each signal path is adjusted in response to pilot channel gain information to maximize the signal to noise ratio of the combined signal paths. The separate signal paths are then summed in a combiner circuit. The time-varying FIR permits the data communication to be summed either before, or after demodulation. A method of combining multipath communications using a time-varying FIR is also provided.

Abstract: A communication system (10) implemented to be specifically matched to the time and spatially dependent statistics of a transmission channel (36). The communication system (10) is used for broadcasting over the channel (36) to users in a coverage region (18). The communication system (10) includes a transmitter (12) having an error correction encoder (30) and a weighted interleaver (32). The error correction encoder (30) includes a first input to receive data bits and a first output. The error correction encoder (30) expands each data bit received at said input by an encoder rate. The weighted interleaver (32) includes a second input to receive the expanded data bits and a second output. The weighted interleaver (32) has a non-uniform delay distribution between a minimum delay and a maximum delay to interleave the expanded data bits by the non-uniform delay distribution.

Abstract: A receiver for a spectrum spread communication system capable of eliminating a deterioration in receive quality due to fading by multipass. A signal of which a spectrum is spread by a direct spread modulation system is transmitted from a transmit side unit. A receive side unit is provided with a plurality of receive antennas, through which receive signals are fed to receiver circuits, followed by conversion of each of the signals into an intermediate frequency signal. Then, the signal is fed to a signal intensity measurement circuit and sampled by a clock n (n: an integer) times as high as a chip frequency, resulting in an intensity thereof being measured. Depending on results of the measurement, a selection signal is fed to a path switching circuit, resulting in one of outputs of the receiver circuits being selected, which is then fed to a direct spread demodulation circuit.

Abstract: A receiver including a signal reception unit, for receiving a signal from a dynamically fading channel, a demodulator, connected to the signal reception unit, for demodulating the received signal, thereby producing a demodulated signal therefrom, a quantizing processor, connected to the demodulator and to the signal reception unit, for analyzing the received signal and for quantizing the demodulated signal, thereby producing a quantized signal, and a decoder, connected to the quantzing processor, for decoding the quantized signal, wherein the quantizing processor normalizes the demodulated signal according to the estimated fading of the received signal.

Abstract: Radio communication apparatus for transmitting control data, comprising output power amplifying means responsive to a control signal from an output power control means for varying a predetermined output power level from the output power amplifying means in accordance with a sequence of power levels indicative of a control message. The predetermined output power level is selectable from a range of predetermined power levels and may be variable between power levels of adjacent predetermined power levels for the range of predetermined power levels. Typically, the control message is a request to vary the output power level for inhibiting radio signal fading.

Abstract: These and other objects of the present invention are achieved using an Adaptive Multi-Path Filter (AMPF) which eliminates audibly objectionable click noise generated at the output of an FM discriminator to prevent audible distortion or other corruption of the desired signal which may include voice and low speed digital data. Clicks are detected at the discriminator output using a colored-noise, matched filter designed and adapted to the click signature/shape as well as to the desired signal characteristics. The colored-noise matched, filter output is then compared to an adaptive threshold. When the threshold is exceeded, a click is registered as detected. Click duration is then estimated. An estimate of the desired signal is generated and that replaces the originally received data signal estimate within the click duration region.

Abstract: The transmission system is designed for links between an infrastructure and moving bodies (10.sub.1, 10.sub.2) constrained to move along a determined path. The infrastructure has fixed transmitter/receiver stations distributed along the path, each having two transmitter/receivers allocated to two adjacent cells, e.g. (E'.sub.1, E.sub.2). The transmitters of two successive fixed stations allocated to the same cell are synchronized and they transmit using a coding system that is capable of tolerating or taking advantage of propagation over multiple paths.

Abstract: With a CDMA mobile communication system of the present invention, the phase difference sensing circuit of the base station senses the phase difference with respect to a reference phase from the cross-correlation value of the up-link channel signals coming from mobile stations and sends timing control information for compensating the phase difference closer to zero to the mobile stations. Then, in each of the mobile stations, the transmission timing control circuit variably sets the amount of delay in the delay circuit of the modulation circuit according to the timing control information sent from the base station. This enables the transmission timing of the transmission signal of each of the mobile stations to undergo delay control, maintaining the orthogonality between the individual up-link channel signals at the base station.

Abstract: A method and system incorporating the use of interference cancellation during synchronized demodulation of a code division multiple access (CDMA) signal is described. A wireless communications receiver uses synchronized demodulation techniques to estimate the data contained in multiple orthogonal sub-channels of multiple CDMA signals. In response to these estimates an ideal waveform is constructed for each CDMA signal. These ideal waveforms are subtracted from the original signal received to form an interference-cancelled version of the original signal which is used when demodulating individual orthogonal sub-channels.

Abstract: An adaptive high speed data transmission system is described. In one aspect, the transmitter for this system employs a plurality of transmit antennas which have controllable offsets. The transmitter also includes signal coding circuitry suitable for use to address transmission impairments due to fast fading in the transmission channel. At the receiver, the received signal is analyzed to determine the fading characteristics of the channel. Where slow fading is detected, the offsets are employed to convert the slow fading into fast fading. The channel characteristics are continually resampled and these characteristics are used to adjust the transmitter and the receiver to achieve optimal transmission speed.

Abstract: A method for simulating RF energy distribution comprises obtaining a binary tree representation of a geometric environment in three-dimensions and forming a 3-D geometric database model therefrom, obtaining one or more specified receive locations within the 3-D geometric database model where RF energy distribution is desirable, simulating the propagation of an RF signal within the geometric database model, the RF signal being represented as a beam having magnitude and direction, the propagation including querying the database model to trace the beam in the geometric environment; and, determining one or more intersections of the traced beam with one or more receive locations to determine RF energy distribution at the receive locations.

Abstract: A system for inducing rapid fading in wireless communication systems, such as digital radio and television transmission is described. Orthogonal polarization combined with time varying offsets are combined to insure rapid fading and result in improved signal reception.

Abstract: A method of optimizing radio communication between a fixed base station having a plurality of antennas and a mobile station by applying, in the base station, processing to all signals S.sub.i (t) received or transmitted via each of the antennas so as to determine corresponding corrected signals S.sub.i (t)=h.sub.i (-t).times.S.sub.i (t), where h.sub.i (-t) is an approximation to the time reversal of the impulse response h.sub.i (t) between antenna and the mobile station.

Abstract: The apparatus and method for estimation and minimization of the residual multipath error signal are disclosed. The reduction of the multipath error signal is achieved by using the weighted or modified tracking. The estimation and minimization of the reduced multipath error signals is achieved by using the generator of additional modified or weighted signals.

Abstract: A radio selective call receiver includes an instruction input device which produces an analog input signal and a radio receiver which receives a radio signal and demodulating it to produce an analog demodulated signal whose amplitude varies in a symbol period. A selector selects one of the analog input signal and the analog demodulated signal and is connected to an A-D converter. The A-D converter is shared between the analog demodulated signal and the analog input signal. An A-D conversion of the analog demodulated signal is performed at intervals synchronizing with the analog demodulated signal. An A-D conversion of the analog input signal is performed within a time period during which the analog-to-digital conversion of the analog demodulated signal is not performed.

Abstract: Radio communication apparatus and method for inhibiting radio signal Rayleigh fading comprises apparatus for varying a nominal output power level in accordance with a sequence of power levels. The sequence may be pseudo-random. The nominal output power level may be one of the system power levels inhibiting normal fading and the sequence of power levels varies the output power in a range between adjacent nominal power levels.

Abstract: In the method for parameterizing at least one receiving device and a receiving device for a radio station, a plurality of decorrelated signals are received by an intelligent antenna device. Antenna weighting factors for suppressing received disturbances and channel coefficients for balancing out the differences in transit time of different signal components of a received signal are determined simultaneously. During a training sequence, test data present in the receiving device is rated in a channel model with channel coefficients and received test data is rated with antenna weighting factors and superposed to form antenna data or model variables. The minimizing of the deviation of antenna data and model variables is performed with the exclusion of the trivial solution. The method is suitable in particular for base stations in mobile radio systems.

Abstract: The invention concerns a system for transmission of spatial diversity radio signals via a geostationary main communication satellite and one or more auxiliary satellites "colocated" in the same orbit. The distance between an auxiliary satellite and the main satellite is in the range from 200 km to 400 km. The system includes conventional bidirectional transmission links between terrestrial mobile terminals and the main satellite and between the latter and a terrestrial station. Additionally, unidirectional transmission links are provided between the auxiliary satellites and the main satellite. Applications include a mobile communication service with portable terminals via a geostationary satellite.

Abstract: A wireless transmitter and receiver are used in a wireless telecommunication system and method including antennas having at least one antenna element with a relatively narrow beamwidth at both the transmitter and receiver for high data rate communication. The antenna element provides beam coverage in both azimuthal and elevational directions, and a processor is operatively connected to the antenna and is capable of determining a suitable communication path with respect to the at least one antenna element and predetermined communications conditions.

Abstract: A method for suppressing the effects of multipath signals in determination of the location of a mobile user, using the speed or magnitude of the velocity v of the user to determine the procedure(s) to be used to determine the range or pseudorange values corresponding to the GPS, GLONASS, LORAN, FM subcarrier or other location determination (LD) signals received from a plurality of LD signal sources. Where the user velocity v satisfies v.ltoreq.v1, or v.gtoreq.v2 (v1 and v2 being two selected velocity threshold values with 0<v1<v2), the range or pseudorange values are determined by a first procedure and by a second procedure, respectively, that reduce or eliminate the effects of multipath signals. Where the user velocity v satisfies v1<v<v2, the range or pseudorange values are determined by a blend of the first and second procedures.

Abstract: A signal processing system and method for improving reception of plural signals received at an antenna array in a wireless communication system by increasing the carrier-to-interference plus noise ratio and by decreasing signal envelope variance of each of the plural signals using single or multiple stage subspace projection and a constant modulus beamformer. Each of the stages separate and optimize one of the signals and projects the remaining signals (if present) to the subspace of the next stage. In the method and system the plural signals received at each antenna are converted to baseband in a wideband RF downconverter. Received signals are thereafter provided in digital form to the constant modulus beamformer where each stage of the beamformer separates one of the plural signals from a stage input so that a stage output has the remaining ones of the plural signals, and projects the stage output onto a subspace of the remaining signals in the next stage.

Abstract: Radio waves having frequencies f.sub.1 and f.sub.2 are radiated to the premises where a wireless LAN is to be constructed. The radio waves of f.sub.1 and f.sub.2 are received by an antenna for scanning the observation plane and a fixed antenna, respectively. Then, the radio wave holograms of the respective radio waves are produced, from which are constructed radio wave source images separated into respective paths. The difference between these source images is found, and then the amplitude and the delay for each path are found. A propagation time response function x(t) of each path is found from the corresponding amplitude, delay and the directivity characteristics of the corresponding antenna, and then the real part and the imaginary part of each time response function are convoluted into a modulated carrier wave signal y(t). The convoluted results are multiplied by the in-phase component R.sub.f and the quadrature component R.sub.f.spsb.* of an unmodulated carrier wave, respectively.

Abstract: An apparatus for measuring multipath propagation characteristics receives a plurality of transmitted waves propagated over a plurality of different propagation paths and subjected to multipath fading over the propagation paths, and measures multipath propagation characteristics with respect to those propagation paths based on the received waves. The multipath propagation characteristics can be measured relative to a plurality of propagation path systems using the same frequency band. The apparatus for measuring multipath propagation characteristics comprises a plurality of transmitters located in different spatial positions, respectively, and a receiver for receiving a plurality of waves transmitted from the transmitters while the receiver is moving. The transmitters generate respective waves to be transmitted that each comprise a plurality of discrete spectral components which are arranged in the frequency domain such that they do not overlap each other in the same frequency band.

Abstract: An FM radio receiver, particularly for mobile receivers, reduces the effects of multipath distortion. It selects either an adaptive process (constant modulus algorithm or CMA) or a antenna diversity process depending on the circumstances of the instantaneous reception. The receiver reduces both the decline of the level of received signals with the diversity process and waveform distortion with the CMA process.

Abstract: A method of automatically determining the reliability of any LOS radio link given certain parameters. Specifically, this method allows a communications network operator to specify and determine the path reliability (PR) for each backbone and extension link in a communications network for a given operating frequency, path length and climatic factor. For each link, the fade margin required (RFM) for a desired path reliability (PRD) is calculated. Then, the actual fade margin of the selected link is calculated using known radio parameters. Preferably, these known radio parameters are stored in a database to facilitate access to this information. Then, the corresponding value of the actual path reliability for the link is calculated using modifications of known statistical models which take into account climatic and geographic factors.

Abstract: A receiver is disclosed for a DS/CDMA communication system wherein a symbol is spread with a predetermined spread code to produce a DS/CDMA signal which is transmitted on a radio frequency carrier. The receiver includes an interference canceller for cancelling signals from undesired sources introduced to a signal received from a desired source using a feedback signal. A phase variation canceller is provided for cancelling a phase variation that occurs in an interval between successive symbols of the received signal. Both cancellers are connected in series. A decision circuit compares an input signal from the interference canceller or from the phase variation canceller with a threshold and produces an output representing one of two discrete values depending on whether it is higher or lower than the threshold. A correction circuit derives a correction signal from a signal produced by the interference canceller and applies it to the interference canceller as the feedback signal.