Abstract: This inventions provides techniques for estimating both temporal and spectral channel fluctuations with the duration of a data symbol. Certain pulse shaping functions are Discrete Prolate Spheroidal Sequences (DPSSs) and are used primarily because of their relatively limited Inter-Symbol Interference (ISI) properties. During reception, these properties allow one or more parameters of a joint time-frequency channel model to be more easily determined. Once the one or more parameters are determined, they can be applied to received symbols to correct the temporal fluctuations, spectral fluctuations, or both of the channel over which a communication took place. The techniques may be adapted for the Multiple-In, Multiple-Out communication situation.

Abstract: This inventions provides techniques for estimating both temporal and spectral channel fluctuations with the duration of a data symbol. Certain pulse shaping functions are Discrete Prolate Spheroidal Sequences (DPSSs) and are used primarily because of their relatively limited Inter-Symbol Interference (ISI) properties. During reception, these properties allow one or more parameters of a joint time-frequency channel model to be more easily determined. Once the one or more parameters are determined, they can be applied to received symbols to correct the temporal fluctuations, spectral fluctuations, or both of the channel over which a communication took place. The techniques may be adapted for the Multiple-In, Multiple-Out communication situation.

Abstract: This inventions provides techniques for estimating both temporal and spectral channel fluctuations with the duration of a data symbol. Certain pulse shaping functions are Discrete Prolate Spheroidal Sequences (DPSSs) and are used primarily because of their relatively limited Inter-Symbol Interference (ISI) properties. During reception, these properties allow one or more parameters of a joint time-frequency channel model to be more easily determined. Once the one or more parameters are determined, they can be applied to received symbols to correct the temporal fluctuations, spectral fluctuations, or both of the channel over which a communication took place. The techniques may be adapted for the Multiple-In, Multiple-Out communication situation.

Abstract: Techniques for reducing or eliminating effects of noise on a wireless communication system are provided. In one aspect of the invention, the technique comprises monitoring noise attributable to an interference source that may affect one or more components of the wireless communication system. The interference source being monitored is distant from the wireless communication system to the degree that noise arrives at the wireless communication system within a substantially point source-like angular range. For example, the noise may be attributable to the sun or tropospheric ducting. The technique then comprises initiating one or more operations, as a function of the monitored noise, to reduce or eliminate the effects of the noise attributable to the distant interference source at one or more of the components of the wireless communication system that are determined to be affected by such noise.

Abstract: A method and apparatus are disclosed for equalizing a channel using improved channel estimates. The present invention assumes that fading will follow a statistical model and obtains an improved channel estimate using one or more basis functions to describe the channel based on known channel statistics. A Karhunen-Loeve expansion can be used for channel estimation to describe the channel. Waveforms are selected that are matched to characteristics of the channel, such as transmission waveforms whose energy is largely restricted to a bandwidth assigned to the channel. Coefficients are estimated for the basis functions using real-time data.

Abstract: Techniques for reducing or eliminating effects of noise on a wireless communication system are provided. In one aspect of the invention, the technique comprises monitoring noise attributable to an interference source that may affect one or more components of the wireless communication system. The interference source being monitored is distant from the wireless communication system to the degree that noise arrives at the wireless communication system within a substantially point source-like angular range. For example, the noise may be attributable to the sun or tropospheric ducting. The technique then comprises initiating one or more operations, as a function of the monitored noise, to reduce or eliminate the effects of the noise attributable to the distant interference source at one or more of the components of the wireless communication system that are determined to be affected by such noise.

Abstract: Systems and techniques for location determination. A plurality of tags emitting radio frequency signals are dispersed throughout a region, such as a building, within which a user's location is to be determined. The radio frequency signals emitted by the tags include information that can be used to identify the location in which the tags axe placed, or simply to distinguish the tags from one another. A portable device receives signals from the tags and provides the signal information to a location server that computes the location of the portable device by comparing the signal information received from the portable device to a map of location venus stored signal information, and identifies the location of the portable device as the location for which the stored signal information best matches the signal information received from the portable device.

Abstract: Techniques for location determination are described. A plurality of tags emitting radio frequency signals are dispersed throughout an region, such as a building, within which a user's location is to be determined. The radio frequency signals emitted by the tags include information that can be used to identify the location in which the tags are placed, or simply to distinguish the tags from one another. A portable device receives signals from the tags and provides the signal information to a location server that computes the location of the portable device by comparing the signal information received from the portable device to a map of location versus stored signal information, and identifies the location of the portable device as the location for which the stored signal information best matches the signal information received from the portable device.

Abstract: This inventions provides techniques for estimating both temporal and spectral channel fluctuations with the duration of a data symbol. Certain pulse shaping functions are Discrete Prolate Spheroidal Sequences (DPSSs) and are used primarily because of their relatively limited Inter-Symbol Interference (ISI) properties. During reception, these properties allow one or more parameters of a joint time-frequency channel model to be more easily determined. Once the one or more parameters are determined, they can be applied to received symbols to correct the temporal fluctuations, spectral fluctuations, or both of the channel over which a communication took place. The techniques may be adapted for the Multiple-In, Multiple-Out communication situation.

Abstract: A method and apparatus are disclosed for equalizing a channel using improved channel estimates. The present invention assumes that fading will follow a statistical model and obtains an improved channel estimate using one or more basis functions to describe the channel based on known channel statistics. A Karhunen-Loeve expansion can be used for channel estimation to describe the channel. Waveforms are selected that are matched to characteristics of the channel, such as transmission waveforms whose energy is largely restricted to a bandwidth assigned to the channel. Coefficients are estimated for the basis functions using real-time data.

Abstract: Techniques for reducing or eliminating effects of noise on a wireless communication system are provided. In one aspect of the invention, the technique comprises monitoring noise attributable to an interference source that may affect one or more components of the wireless communication system. The interference source being monitored is distant from the wireless communication system to the degree that noise arrives at the wireless communication system within a substantially point source-like angular range. For example, the noise may be attributable to the sun or tropospheric ducting. The technique then comprises initiating one or more operations, as a function of the monitored noise, to reduce or eliminate the effects of the noise attributable to the distant interference source at one or more of the components of the wireless communication system that are determined to be affected by such noise.

Abstract: An improved process for making a structure using three dimensional printing techniques is disclosed. Briefly stated, the method can be summarized by the following steps: A first type of powder material is deposited in a defined area to form a first layer. Next, a binder material is applied to certain regions of the first type of powder to define a portion of the structure to be formed. And finally, a portion of the unbound powder is removed using a technique such as vacuuming. The foregoing steps are repeated a sufficient number of times to create the desired shape of the structure as defined by the regions held by the binder material.

Abstract: An accurate and simplified method of non-destructively measuring the zero-dispersion wavelength along the length of a single-mode fiber is disclosed. The method includes the steps of measuring the FWM intensity of the optical fiber at a plurality of wavelengths, plotting the measured FWM intensity at each of the plurality of wavelengths to obtain a curve representative of the FWM intensity of each of the plurality of wavelength, and performing a non-linear inversion on the curve to obtain the zero-dispersion wavelength along the length of the fiber.

Abstract: Apparatus for generating the family of PSK (phase shift keyed) modulations, which include BPSK (binary PSK), QPSK (quaternary PSK), MSK (minimum shift keying) and the like. The carrier is generated with the desired digital information already phase-modulated onto it by directly introducing a phase shift or delay onto the error path of a phase-locked loop. causing the phase-locked loop to create the phase modulation. The [proposed scheme differs from common practice approaches, which are usually implemented by linear synthesis (an AM technique); rather, it] invention employs direct nonlinear synthesis (an FM technique). The invention [yields good phase precision with arbitrary spectral shaping under the constraint of constant envelope signaling. It] permits the connection of the output of a simple, inexpensive VCO (voltage controlled oscillator) directly to a system's antenna without the need for intervening circuit elements such as phase splitters, mixers, and the like which is applicable to [.

Abstract: The present invention provides a method and apparatus for detecting control signal information for an element of a communication system. The control signal information is included in one or more segments of a signal communicated over a communication system channel. The invention provides for the application of a plurality of tapers to a segment of a communicated signal; the transformation of a tapered segment; the determination of a similarity score based on a transform of a tapered segment and a model of a control signal; the identification of control signal information based on a similarity score; and the creation of an indicator signal representative of the identified control signal information to the communication system element. The control signal information may comprise a dual-tone multi-frequency signal. The tapers may comprise a discrete prolate spheroidal sequence. A similarity score may be determined based on a ratio of energy distributions.

Abstract: Supervisory audio tones received from a mobile telephone unit are converted from analog to digital form. The tone is then converted to a complex number by bifurcating the tone path and multiplying one path by a sine function and the other path by a cosine function. The complex numbers are accumulated and the frequencies where significant power exists is found using the discrete Fourier transform. If the power at an assigned frequency exceeds a threshold, the corresponding supervisory audio tone is declared to have been detected.

Abstract: Received data signals in digital form are sampled a plurality of times during each bit interval and weighted to enhance the statistical effect of a predetermined intermediate amplitude range prior to accumulation over a bit time to obtain an initial average indication of bit value. Plural repetitions of the same bit received at different times are similarly processed and the averages weighted according to received signal strength at the time of reception. Then the weighted averages are accumulated in a two's complement arithmetic fashion so that the accumulation sign bit binary signal state indicates the binary value of the bit. In one embodiment, the initially derived multiple samples of each bit are converted to in-phase and quadrature-phase versions prior to the sample accumulation step; and the separate accumulations of each version are utilized to obtain an arctangent value for adjusting the phase of a local clock to that of the received data.

Abstract: A data signal is processed to change its form and spectral content without introducing undesirable frequency and amplitude effects. Multiple data signal states, which determine the essential characteristics of the output signal wave configuration, are utilized in conjunction with clock signals at a rate substantially in excess of twice the largest frequency component of the data signal in order to read from a memory a bit-duration waveform sample set representing the desired output signal wave configuration. Predistortion to compensate for anticipated transmission effects is also included in that configuration. In one embodiment, an input data signal is in an NRZ format and is processed for conversion to the biphase, or Manchester, format by a ROM table look-up function addressed jointly by the input signal states and the clock signals.

Abstract: A programmable oscillation counter (10) is initially synchronized by presetting the counter to a predetermined correct phase condition by applying thereto a single digital signal set representing the magnitude of the phase correction to be applied. Subsequent tracking of the correct phase condition is accomplished by utilizing additional two's-complement digital signal sets from time to time to preset an incremental counter (11) to a level which indicates the extent of phase error. The latter counter is controlled to reduce the error by altering the phase of the oscillation counter operation by one step at a time each time the oscillation counter cycles through a predetermined phase of its operation and until the incremental counter has counted down its preset phase error magnitude to zero.

Abstract: To stabilize the phase of bit rate clock signals recovered from a self-clocking data signal, e.g., a Manchester coded signal, extra signal level transition pulses (58) occurring during intervals of successive bits of the same info bit type are inverted (59) to reinforce the desired phase of the bit-rate frequency component.