Digital preemphasizer for transmission of PCM codes

Abstract

A method for digital preemphasizer high fidelity reconstruction of an original pulse code modulation (PCM) serial stream binary data signal which has suffered degradation of fidelity, and consequent increase in bit-error-rate, during transmission on a single channel from a transmitter to a receiver. Prior to transmission, amplitude encoded digital pre-emphasis of each bit of the original binary data signal to be transmitted mitigates or remedies the signal degrading frequency dependent losses concomitant with the signal transfer network characteristics of the fixed transmission line. Subsequently, the amplitude encoded signal is transmitted to the receiver connected to the other end of the fixed transmission line. Compared to a conventional transmitter, transmision line, and receiver system, the end result of amplitude encoded pre-emphasis is superior reconstructed fidelity and quality of the PCM waveform, i.e. lower bit-error-rate, at the output of the receiver for the same length of transmission line.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention, disclosed hereinafter, concerns generally an apparatus and method for reducing signal errors attendant to pulse or digital communications transmitted along lossy, band-limited, time-invariant, fixed length, single channel transmission path. In particular, the present invention provides apparatus and method for reducing the error-rate of digital PCM (pulse code modulation) data by means of preemphasis precoding or encoding of the binary PCM data signal prior to transmission on a single channel of a cable system.[0003]2. Description of the Related Art[0004]The electronic transmission of data and information by means of pulse and digital systems typically involves either a variable path, such as a radio link between a cellular or cordless is telephone and a repeater node, or alternatively, a fixed, time variant path, such as a copper fiber optic cable connecting a cable television subscriber's receiv...

AI Technical Summary

Benefits of technology

[0008]An object of the present invention is to provide a means for high fidelity reconstruction, i.e. low, acceptable bit error-rate, of an original pulse code modulation (PCM) serial stream binary data signal which has suffered degradation of fidelity, and consequent increase in bit-error-rate, during transmission on a single channel from a transmitter to a receiver, connected to each other by a transmission line exhibiting both resistive and frequency dependent loss. This object is accomplished prior to transmission by amplitude encoded digital pre-emphasis of each bit of the original binary data signal to be transmitted in such manner as to mitigate or remedy the signal degrading frequency dependent losses concomitant with the signal transfer network characteristics of the fixed transmission line. Subsequent to this pre-emphasis process, the amplitude encoded signal is transmitted to the receiver connected to the other end of the fixed transmission line. Compared to a conventional transmitter, transmission line, and receiver system, the end result of amplitude encoded pre-emphasis is superior reconstructed fidelity and quality of the PCM waveform, i.e. lower bit-error-rate, at the output of the receiver for the same length of transmission lie or, alternatively, a longer transmission line for the same bit error-rate.

[0009]A further object of the present invention is to reduce the complexity and cost of signal processing equipment at the receiver while maintaining a low, acceptable bit error-rate. As a consequence of employing the present invention, the excellent high fidelity reconstruction of the received, amplitude encoded signal obviates many requirements for complex, expensive signal processing equipment at or following the receiver, such as bit synchronizers, filters, equalizers, and compensators.

Problems solved by technology

These constraints foreclose the option of a separate clocking or timing channel.

Also, there may be constraints to the low frequency response of the designed transmission system.

Unfortunately, such codes effectively reduce the available data and information bandwidth by half.

Intended to reconstruct the degraded fidelity of the signal present at the input to Receiver 24 to a replication of Waveform 21 by compensating for the frequency dependent losses attendant to the Fixed Transmission Line 23, Network 26 tends to be complex and difficult to implement.

Although Network 26 may also include some techniques to correct the slope or rise time of the attenuated received signal, such techniques are often primitive and inadequate for reliable, high-quality digital PCM data transmission.

Containing expensive, complex circuitry, this synchronizer component can cost thousands to tens of thousands of dollars; proper utilization often entails lengthy, difficult adjustments,

Images