A burst mode digital communications system which is unique in that it modulates a sinusoidal carrier with discrete cosine segments. The discrete cosine segments may contain different time and amplitude values. The discrete cosine segments may be combined with each other or with zero slope level segments in order to effectively modulate the sinusoidal carrier. Rather than employing the use of filters for controlling instantaneous voltage changes, the present communications system forces the bit edges of the discrete cosine segments to occur at the zero slope points of a cosine wave, where no voltage changes occur. The communications system utilizes direct digital synthesis in order to create a carrier signal which closely represents sinusoidal carrier signal. The present communication system may be used in conjunction with various conventional methods such as phase-shift keying and amplitude-shift keying. A device is also disclosed for demodulating the carrier signal in order to recover the original base band signal. The burst mode digital communications system may also demodulate data by employing adaptive templates for more accurately determining received digital symbols.
CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of application Ser. No. 08/726,785 filed on Oct. 7, 1996, now U.S. Pat. No. 5,864,585.
A system for identifying phase transitions in phase-shift keying signals and frequency transitions in frequency-shift keying signals broadly comprises a memory and a computing element capable of: selecting a portion of the signal to analyze, wherein the signal comprises a plurality of data samples; applying a transform to the signal to obtain a frequency spectrum; determining a maximum frequency spectrum corresponding to a carrier frequency; determining a starting approximation value of a slope of the phase transition; calculating a bounded limit of slopes within which to search for the phase transition; selecting a plurality of lines, calculating a sum for the data samples associated with each of the lines; and based on the sum for the data samples, identifying a line that corresponds to a location of the phase transition.
A method for communicating data over a network having a plurality of nodes thereupon is discussed. A time slot clock signal is transmitted from one node of the plurality of nodes to other nodes of the plurality of nodes. After each of the other nodes of the plurality of nodes receives the time slot clock signal, the time slot clock signal is recalculated to achieve an integer number of slots on the network. The recalculated time slot clock signal is transmitted from the one node of the plurality of nodes to the other nodes of the plurality of nodes.
An error detection and correction apparatus includes three threshold logic units which make decisions based on current and previous bit values in a bit stream of block-coded data. One of the threshold logic units decodes the data stream based on an advancing time stream of data. Another threshold logic unit decodes the data stream based on a time-reversed stream of data, and the last threshold logic unit decodes the data stream based on a time-reversed input stream of data and a time-reversed set of decisions made by the first threshold logic unit. Each threshold logic unit generates decisions and a parity check of those decisions Error identification information is compared between the three streams of decisions and parity checks on those decisions, thereby producing error information, which is processed by a circuit which determines which is the most likely data transmitted.
The present invention relates to a method and apparatus for determining channel degradation information in which a known data sequence is compared to a transmitted version of the known data sequence to provide such information. To assess performance of a public land mobile network, it is convenient if assessment apparatus is located in the network rather than in a mobile station. The invention provides a technique for efficiently sending data characterizing channel degradation caused by the network to mobile station communication channel from the mobile station back to the network, where the channel degradation information is reconstructed.
Method and apparatus for providing high strength, low frequency tactile sensations using an inertial actuator in a haptic feedback interface device, such as an actuator driving an oscillating inertial mass. A commanded low frequency is modulated or combined with a higher frequency at which the tactile sensations feel stronger, where the resulting signal is used to output a tactile sensation at the higher frequency and convey the commanded low frequency to the user. One embodiment provides higher frequency pulse bursts at the desired low frequency wherein the higher frequency pulse bursts are at or near a resonant frequency of the actuator; other embodiments modulate or otherwise vary the amplitude of the higher frequency signal according to the desired low frequency.
