Abstract: A method and apparatus are disclosed for modulating a communication signal in a CDMA environment using orthogonal N by N Hadamard spread spectrum codes. Orthogonal spreading codes are used that have lengths that are not a power-of 2 to provide additional channel variability for various multimedia applications and increase the flexibility of the number of channels/bandwidth relationship. The Hadamard codes are multiples of 4 (4n) and demonstrate a good cross-correlation property, making them very useful in the flexible design of CDMA systems. A transmitter encodes each of N data streams (N not being a power of 2), to be transmitted using a 4n codeword, Ni. The received signal is passed through a filter matched to the characteristics of the appropriate codeword, Ni, and PN spreading sequence.

Abstract: A method and apparatus for generating a pronunciation score by receiving a user phrase intended to conform to a reference phrase and processing the user phrase in accordance with at least one of an articulation-scoring engine, a duration scoring engine and an intonation-scoring engine to derive thereby the pronunciation score. The scores provided by the various scoring engines are adapted to provide a visual and/or numerical feedback that provides information pertaining to correctness or incorrectness in one or more speech-features such as intonation, articulation, voicing, phoneme error and relative word duration. Such useful interactive feedback will allow a user to quickly identify the problem area and take remedial action in reciting “tutor” sentences or phrases.

Abstract: An improved OFDM receiver is disclosed that repositions peaks in an OFDM frame to a desired position away from the frame boundary to reduce the probability of timing ambiguity. Each OFDM frame is divided into at least two windows during an acquisition mode to identify the index within each window having the maximum correlation. The improved timing acquisition of the present invention permits the Fast Fourier Transform (FFT) operation to operate on the correctly aligned symbol for improved accuracy. In addition, the present invention provides improved mechanisms for declaring when timing is acquired or when timing has been lost. In one implementation, the peaks are shifted from the frame boundary to the center of the OFDM frame, thereby removing the ambiguity of whether a given peak is associated with a previous or subsequent frame.

Abstract: The invention includes a method for determining an expenditure associated with a network. A method includes obtaining network information associated with a portion of a network, categorizing each of a respective plurality of cells as one of an aggregated cell and a non-aggregated cell, determining an aggregating node configuration for at least one aggregating node associated with at least one base station associated with an aggregated cell, determining a deaggregating node configuration for at least one deaggregating node associated with at least one of the at least one aggregating node, and determining the expenditure according to at least one of the aggregating node configuration and the deaggregating node configuration. The categorization of cells is performed using the network information.

Abstract: A CDM satellite transmission system is disclosed that broadcasts programming content, such as audio and video information, using one or more geo-synchronous satellites based on Code Division Multiple Access technology. Forward error correction coding and interleaving are used prior to broadcasting the signals over the CDM channel to account for signal loss due to short-term fading. The CDM satellite transmission system provides a tuning channel corresponding to each program channel that reduces the delay when a mobile receiver is first tuned to a selected program channel. The tuning channel utilizes a shorter interleaver length, if any, than the corresponding primary program channel. The CDM satellite transmission system transmits a delayed version of a program signal with the on-time version of the audio output to accommodate uninterrupted reception in the event of such a blockage.

Abstract: A system and method is disclosed for improving diversity in a multiple transmitter or multiple receiver orthogonal frequency division multiplexing (OFDM) system. Signal diversity is improved by introducing phase offsets at the transmitters and/or the receivers. The phase offsets are unique to each transmitter or receiver. The unique phase offsets are applied to individual symbols of the OFDM signal in the frequency domain.

Abstract: A satellite digital audio radio system (SDARS) transmitter provides a broadcast transmission signal including a time division multiplex (TDM) mode of transmission and a coded orthogonal frequency multiplex (OFDM) mode of transmission. The SDARS transmitter provides a transmission signal that supports four transport mechanisms or traffic channels: (1) multiple audio and data program channels (program channels), (2) a cluster control information channel (CC), (3) a global control information channel (GC), and (4) a synchronization channel (CS). In particular, the SDARS transmitter processes 100 program channels into 5 clusters, each cluster comprising GC and CS information, along with a program cluster comprising 20 program channels and CC information. The SDARS transmitter further partitions each cluster into 255 cluster segments and interleaves the cluster segments from each cluster for transmission.

Abstract: A terrestrial repeater is disclosed for use in a satellite transmission system that may also include a plurality of satellites. The terrestrial repeaters are implemented as OFDM transmitters to minimize the channel impairments caused by multi-path propagation. The OFDM terrestrial repeaters differentially encode the transmitted signal over frequency, as opposed to time, in order to avoid channel phase distortion. The OFDM receiver allocates two unmodulated sub-carriers as pilot bins and thereby provides two sub-carriers as a reference within each OFDM symbol. At the OFDM receiver, the two unmodulated pilot bins contain no phase information and provide a reference for the differential demodulation performed by the OFDM receiver. The OFDM transmitter operates in two modes, namely, a normal mode and a transmitter identifier information (TII) mode.

Abstract: A CDM satellite transmission system that broadcasts programming content, such as audio or video information, using two geo-synchronous satellites and a plurality of terrestrial repeaters based on Code division multiple access [(CDMA)] technology is disclosed. A plurality of programming channels is multiplexed onto a carrier frequency using Code division multiple access [(CDMA)] technology. A delayed version of the signal is transmitted with the on-time version of the programming content to accommodate uninterrupted reception in the event of a blockage. The on-time and delayed version of each information channel is transmitted by each of the satellites and repeaters, providing additional diversity gains. Thus, the satellites and terrestrial repeaters occupy the entire available bandwidth. CDM transmissions are used where the pseudo-noise sequences are the same, or linear translates of one another.

Abstract: A method and apparatus for generating a pronunciation score by receiving a user phrase intended to conform to a reference phrase and processing the user phrase in accordance with at least one of an articulation-scoring engine, a duration scoring engine and an intonation-scoring engine to derive thereby the pronunciation score. The scores provided by the various scoring engines are adapted to provide a visual and/or numerical feedback that provides information pertaining to correctness or incorrectness in one or more speech-features such as intonation, articulation, voicing, phoneme error and relative word duration. Such useful interactive feedback will allow a user to quickly identify the problem area and take remedial action in reciting “tutor” sentences or phrases.

Abstract: A satellite digital audio radio system (SDARS) transmitter provides a broadcast transmission signal including a time division multiplex (TDM) mode of transmission and a coded orthogonal frequency multiplex (OFDM) mode of transmission. The SDARS transmitter provides a transmission signal that supports four transport mechanisms or traffic channels: (1) multiple audio and data program channels (program channels), (2) a cluster control information channel (CC), (3) a global control information channel (GC), and (4) a synchronization channel (CS). In particular, the SDARS transmitter processes 100 program channels into 5 clusters, each cluster comprising GC and CS information, along with a program cluster comprising 20 program channels and CC information. The SDARS transmitter further partitions each cluster into 255 cluster segments and interleaves the cluster segments from each cluster for transmission.

Abstract: In all wireless systems, the first operation that must take place at the receiver is the acquisition of the carrier and timing. OFDM systems are particularly sensitive to carrier offsets since these can introduce inter-carrier interference and loss of signal power. An algorithm, termed modulo-sub-carrier (ModSC), which can estimate the local oscillator offset in a fast and efficient manner has been devised. The carrier offset can be brought to within one half the carrier spacing within 1 to 10 OFDM symbols. By inserting a null in the center carrier, carrier acquisition can be easily accomplished by locating this null in the FFT bins at the receiver. The offset of this null from the designed position indicates the local oscillator offset in units of number of sub-carriers. An additional carrier tracking algorithm is used to estimate the offset within one half the inter-carrier spacing. Together, the ModSC and carrier tracking algorithms completely estimate the local oscillator offset.

Abstract: In a wireless transmission system that transmits the same information in parallel using two or more different types of modulation schemes, such as a satellite-based digital audio transmission system transmitting two TDM signals and a single OFDM signal, a receiver processes the differently modulated signals to generate separate demodulated signals that are then combined to form a single combined signal for further processing (e.g., decoding). In one embodiment, the receiver applies a maximal ratio combining (MRC) technique to generate a single optimal ratio combined signal from the differently modulated signals. By combining the differently modulated signals using an MRC technique, the adverse affects of noise related to inter-symbol interference in the individual signals can be reduced and the complexity of hardware in the receiver can be reduced.

Abstract: An automatic gain control technique is disclosed for adjusting the gain of an IF amplifier in a communication system, such as an OFDM or DMT communication system. The gain of an RF amplifier is controlled by a known RF automatic gain control circuit that generates an RF gain value. The disclosed IF automatic gain control (AGC) circuit controls the gain of an IF amplifier in the receiver. The disclosed IF AGC monitors the RF gain value, as well as pre-FFT and post-FFT signal energy measurements performed before and after a fast Fourier transform (FFT) stage, respectively, to maintain a desired set point. The IF AGC adjusts the previous IF gain value by an amount opposite to the adjusted RF gain value, if any. If there is no RF gain adjustment, then the IF AGC will adjust the IF gain based on thresholds established for the pre-FFT and post-FFT measurements. If the pre-FFT measurement is within a desired tolerance of the pre-FFT threshold, then the IF gain will be lowered in stepped increments.

Abstract: A method and apparatus are disclosed for modulating a communication signal in a CDMA environment using orthogonal N by N Hadamard spread spectrum codes. Orthogonal spreading codes are used that have lengths that are not a power-of 2 to provide additional channel variability for various multimedia applications and increase the flexibility of the number of channels/bandwidth relationship. The Hadamard codes are multiples of 4 (4n) and demonstrate a good cross-correlation property, making them very useful in the flexible design of CDMA systems. A transmitter encodes each of N data streams (N not being a power of 2), to be transmitted using a 4n codeword, Ni. The received signal is passed through a filter matched to the characteristics of the appropriate codeword, Ni, and PN spreading sequence.

Abstract: An improved OFDM receiver is disclosed that repositions peaks in an OFDM frame to a desired position away from the frame boundary to reduce the-probability of timing ambiguity. Each OFDM frame is divided into at least two windows during an acquisition mode to identify the index within each window having the maximum correlation. The improved timing acquisition of the present invention permits the Fast Fourier Transform (FFT) operation to operate on the correctly aligned symbol for improved accuracy. In addition, the present invention provides improved mechanisms for declaring when timing is acquired or when timing has been lost. In one implementation, the peaks are shifted from the frame boundary to the center of the OFDM frame, thereby removing the ambiguity of whether a given peak is associated with a previous or subsequent frame.

Abstract: A carrier signal acquisition technique is disclosed that improves the reliability of the generated carrier frequency offset. An improved course carrier frequency offset algorithm is employed in conjunction with a conventional fine carrier frequency offset algorithm. The course carrier frequency offset algorithm associated with the present invention estimates large offsets that are multiples of the carrier spacing that may occur at system startup. A spectral null is placed in the center of the transmit spectrum and is thereafter located in a received signal. The position of the spectral null provides an estimate of the local oscillator carrier offset. A frequency finite state machine (FSM) is disclosed that processes a number of metrics to ensure the reliability of the course carrier frequency offset and of transitions between acquisition and tracking modes. The frequency FSM will utilize the frequency offset (modin) generated by a MODSC algorithm provided one or more predefined thresholds are satisfied.

Abstract: A method and apparatus for estimating the signal-to-noise ratio in Orthogonal Frequency Division Multiplexing (OFDM) and Discrete Multi-tone (DMT) systems is disclosed. In all OFDM and DMT systems, the transmitter uses an Inverse Fast Fourier Transform (IFFT) of a significantly longer length than the number of sub-carriers that are used for information transmission (i.e., the active sub-carriers). The additional IFFT buffer locations (i.e., the inactive sub-carriers) are filled with zeroes. At the receiver, after the FFT operation, the active sub-carriers will contain the signal plus noise information whereas the inactive sub-carriers will contain only noise.

Abstract: Methods of estimating the signal-to-noise ratio (SNR) of a signal in an orthogonal frequency division multiplexed (OFDM) system include the steps of representing the signal as a complex symbol and rotating the complex symbol in a complex plane so that the signal component of the function lies substantially on the real axis of the complex plane and the noise function lies substantially on the imaginary axis of the complex plane. By obtaining the means squared value of the complex symbol and the variance of the complex symbol and dividing them, an estimate for the SNR of the signal is obtained.

Abstract: Techniques for more accurately detecting the data rate of a frame of data in a cellular telephone system are described. Data is preferably received at one of four rates: full, half, quarter and eighth. A correlation is performed between the incoming soft data and the data generated by re-encoding and re-repeating the data. Variations on the approach make it readily possible to accurately perform rateset 1 or rateset 2 rate detection.