摘要:
A circuit for detecting a transmit diversity signal comprises a first circuit (706) arranged to receive a first synchronization code. The first synchronization code is modulated by a data signal. The first circuit produces a first output signal. A second circuit (732) is arranged to receive a plurality of predetermined signals. The second circuit produces a channel estimate. A detection circuit (710, 712) is arranged to receive the first output signal and the channel estimate. The detection circuit produces a signal corresponding to the data signal.
摘要:
An improved interference cancellation technique is disclosed. Digital baseband circuitry (40) includes user and symbol detection circuitry (50) for performing a Gibbs sampler type of interference cancellation, either embodied in custom hardware (44) or in software. Random initial guesses for a signal sample (either a symbol or chip) are made for each user. Interference cancellation is performed on a user-by-user basis, using the then-current data decision values for the other, interfering users. A soft data decision is used to derive a probability distribution function for the actual data decision for the sample for the user. A randomly selected value is applied against the probability distribution function to generate the next data decision value for that user, and the process is repeated until convergence. Following convergence, a statistic is used to select a final data decision value for each user, from the set of intermediate data decision values stored in memory.
摘要:
In an equalizer filter unit, the filter is divided into a plurality of sequential segments. While all the components of the equalizer unit multiply data signal groups by the a coefficient signal group, in only one segment are the coefficient signal groups updated. The data and the coefficient signal groups are periodically transferred to the next sequential filter segment while the filter segments are reconfigured in the original sequential order. In this manner, the each data signal group interacts with a coefficient signal group in the original sequential order. Because the coefficients are updated in only one of the filter segments, the amount of apparatus required for processing signal groups is reduced.
摘要:
A linecard codec (250) permitting an increased throughput connection between a subscriber modem (20) and a service provider coupled to a digital backplane (150). The linecard codec (250) includes an analog interface (152) to the Public Switched Telephone Network, a digital interface (119) to the digital backplane (150), conversion circuits (258, 280) interspersed between the analog interface (152) and the digital interface (119), and a controller (340) having a network interface (350) and configured to format requests for bandwidth and transmit them to a network administrator of the digital backplane (150). A code recognition mechanism (272) is used to monitor the Pulse Code Modulated (PCM) signals from service providers and in combination with control logic (300) and the controller (340) provides a way to allocate and deallocate timeslots on the digital backplane (150).
摘要:
The preferred embodiments generalize the Band Edge Component Maximization (BECM) timing recovery method and provide blind timing recovery in Quadrature Amplitude Modulation (QAM) using all the available information rather than sampling the BECM output at the symbol rate.
摘要:
A data processing system includes a digital signal processor core and a co-processor. The co-processor has a local memory within the address space of the said digital signal processor core. The co-processor responds commands from the digital signal processor core. A direct memory access circuit autonomously transfers data to and from the local memory of the co-processor. Co-processor commands are stored in a command FIFO memory mapped to a predetermined memory address. Control commands includes a receive data synchronism command stalling the co-processor until completion of a memory transfer into the local memory. A send data synchronism command causes the co-processor to signal the direct memory access circuit to trigger memory transfer out of the local memory. An interrupt command causes the co-processor to interrupt the digital signal processor core.
摘要:
A digital filter can be implemented with a reduced number of components for a transform function having specific characteristics in the regions outside of a center region. The characteristics are that the transform function waveform is periodic with period T and has or can be approximated by at least one envelope, the envelope decaying a multiplier constant for each period T in a direction away from the waveform center. The digital filter has three groups of elements. A center group of components functions in a manner similar to the prior digital filters. A positive time group of components receives the signals from the center, and using a group of delay component, delays the signal by one period T, is reduced by the multiplier constant factor, and after having the current signal from the center group applied thereto, is once again applied to the positive time group delay components. Each positive time group delay component has coefficient multiplier component which multiplies the signal in the associated delay component by a cumulative coefficient prior to applying the signal to the output line. The negative time group of components can include a group of delay components and coefficient multiplier components which function in the prior art manner. In the alternative, the negative time group of components can include a series of delay component which applies the signal transmitted therethrough to the center group of components and to the a negative time group of component similar in structure and function to the positive time group of components.
摘要:
An MDSL modem is provided that is inter-operable with an ADSL modem. The present invention provides a method for modem operation, by dividing available bandwidth for the modem into a plurality of subsets, selecting at least one of the plurality of subsets for use as a communication path, reducing the SNR value used for bit loading for the selected subsets by a predetermined amount, undersampling any received data, and fast fourier transforming the received data to recover the data transmitted. An MDSL modem is provided having circuitry for dividing available bandwidth for the modem into a plurality of subsets, circuitry for selecting at least one of the plurality of subsets for use as a communication path, circuitry for reducing the SNR value used for bit loading for the selected subsets by a predetermined amount, circuitry for undersampling any received data, and circuitry for fast fourier transforming the received data to recover the data transmitted.
摘要:
Apparatus and method (10) for recovering timing information from a vestigial sideband (VSB) modulated signal generate a left hand component signal and a right hand component signal from the received signal, and filters B.sub.1 (f) and B.sub.r (f) (12, 14) filter the left hand and right hand component signals respectively. The filtered signals are then multiplied together without taking the complex conjugate of either signal, as in band edge component maximization (BECM). The generated output signal may be used in a feedback loop to regulate the sample rate of an analog to digital converter (32).