Abstract: A dynamically selectable multimode pulse width modulation system includes ramp generator means for generating a ramp; pulse edge modulation means responsive to the ramp generator means for defining a leading edge modulated pulse, a trailing edge modulated pulse and a dual edge modulated pulse; and mode selection means responsive to the pulse edge modulation means for selecting one of the leading edge modulation, trailing edge modulation, and dual edge modulation modes of pulse width modulation.

Abstract: One of a reference phase signal and an orthogonal phase signal is inverted to provide an inverted phase signal. when an arrangement of a local frequency is the same between transmitting and receiving sides, a carrier wave signal is FM-modulated by the reference and orthogonal phase signals. On the other hand, when the above arrangement is different between the transmitting and receiving sides, a carrier wave signal is FM-modulated by the inverted phase signal and the remaining one of the reference and orthogonal phase signals.

Abstract: Methodology, and associated circuitry, for encoding and decoding an incoming data stream utilize a coordinated code constellation that effects robust signal detection in the presence of channel interference. The encoder partitions the incoming data stream into contiguous data segments in proportion to the number of levels for a given coordinated code. Each data segment is mapped with reference to the coordinated code to signal levels suitable for transmission over a plurality of channels. The decoder measures the received signals on the channels and estimates noise statistics for the channels. A metric relationship engendered by the coordinated code is evaluated with reference to the received signals, estimates to the received signals, and the noise statistics. An output data stream is then generated based on the evaluation of the metric.

Abstract: Data receiver in which a received signal is sampled and converted to a digital signal by an analog-to-digital converter (1), the signal samples being detected by a Viterbi detector (3). In order to have the sampling effected at the correct instants, these sampling instants are derived from the received symbol values and an error signal which is a metric for a difference between an expected and a recent signal sample. This is effected by a multiplier 4, a low-pass filter 5 and a control signal for a controllable clock oscillator (6). For utilizing the energy in a precursor of the received signal, an error signal e(k-1) is used which is obtained at a later instant than the instant at which a provisional decision about the relevant data symbol a(k-2) is made.

Abstract: A method and apparatus for improving the performance of the transferring of transaction handshakes between sections of synchronous logic which are in different timing domains providing immunity from set-up and hold violations and associated problems of metastability, by reducing the time overhead required for signal synchronization.

Abstract: An interactive call is set up by a method including the steps of: emitting a message from the terminal to the connection network defining the resources required for all of the connections and for all the periods of the call, and emitting a message from the connection network to the terminal indicating that the network possesses such resources for at least one call. During each interactive call, prior to each new period requiring different resources, and for each connection of the call, the method further includes the steps of: emitting a message from the terminal to the connection network indicating each connection that is going to be necessary during the new period and indicating the resources that will be required for the connection, emitting a message from the connection network to the terminal confirming that the resources have been reserved by the network, and storing in the terminal data to be transmitted over the connection network until the terminal receives the message.

Abstract: A receiver for use in digital cellular communication systems determines the type of data transmitted without having to decode the data. Digital cellular communication systems typically use convolutional forward error correction (FEC) coding to allow for error detection and correction at the receiver. The type of encoding is different depending on whether voice data or control data is transmitted. In general, FEC coding is a redundant coding of the encoded data so that for a given encoding algorithm with FEC coding, there will be a limited number of valid code sequences less than the total possible number of code sequences for a transmission of the same number of bits. This characteristic is used to identify the type of encoding without decoding the received information. Consequently, decoding requirements are reduced to those corresponding to the active transmitting encoder, resulting in receiver complexity reduction.

Abstract: A method for optimizing a set of equalizer parameters of an equalizer to be used to equalize a multicarrier data signal that has been transmitted through a distorting channel, comprised of the steps of initializing the parameters, repeatedly sending a training sequence through the channel to the receiver, using the equalizer parameters, the received sequence, and a local replica of the training sequence to update a set of channel target response parameters, windowing the channel target response parameters, using the channel target response parameters, the received sequence and the local replica to update the equalizer parameters, and windowing the equalizer parameters. This training process is repeated until a predetermined convergence condition is detected.

Abstract: The present invention addresses a timing synchronization problem which arises in tandem modem operation when a single codec strobed by a common sample clock is used for A/D and D/A signal conversion in a modem. Tandem modem operation is defined as a system application when two modems have their RS-232 interfaces directly connected to one another. In accordance with the present invention, a digital interpolator connected to the A/D converter in the modem effectively alters the timing phase of the A/D converter in response to first and second control signals. The first control signal is generated in response to an externally supplied clock and an internal modem clock and is representative of any perturbations in the externally supplied clock with respect to the internal modem clock.

Abstract: A system and method for frequency acquisition by a mobile receiver 14 in a cellular communication system. Data for part of a frame 10 is sampled. Synchronization pattern 36 is rotated by a pattern rotator 37 to simulate fixed frequency offsets. The known sync pattern 36 is correlated with the sampled data by correlator 30 for a number of phase advances corresponding to the simulated fixed frequency offsets. The peak outputs 54 and 58 of the correlator 30 for the number of fixed frequency offsets is interpolated by parabolic interpolator 46 to adjust the receivers voltage controlled crystal oscillator 49 to reduce the offset.

Abstract: A clock recovery circuit employs a method of and apparatus for adjusting the phase of a recovered clock signal. The clock signal is recovered from a received input signal. The clock recovery circuit generates a sampling clock signal which is synchronous with the received signal. Additionally, the phase adjustment apparatus generates at least two error signals which indicate the quality of the received signal at different sampling phases. The smallest error signal is referred to as the minimum error value. Each error signal is compared to the minimum error value, creating a corresponding normalized error magnitude signal. Each normalized error magnitude signal is processed to determine the desired phase of the sampling clock signal. Dependent upon the processing of the normalized error magnitude signals, the phase of the sampling clock signal is either shifted or maintained until the next sampling point.