Line code

Abstract: Introduction to Data Communications. Theoretical Foundations of Digital Communications. Error Correcting and Detecting Codes. Baseband Pulse Transmission. Passband Data Transmission. Synchronization. Optimum Data Transmission. Automatic and Adaptive Equalization. Echo Cancellation. Topics in Digital Communications. Index.

Abstract: A multi-channel digital transceiver (400) receives uplink radio frequency signals and converts these signals to digital intermediate frequency signals. Digital signal processing, including a digital converter module (426), is employed to select digital intermediate frequency signals received at a plurality of antennas (412) and to convert these signals to baseband signals. The baseband signals are processed to recover a communication channel therefrom. Downlink baseband signals are also processed and digital signal processing within the digital converter module (426) up converters and modulates the downlink baseband signals to digital intermediate frequency signals. The digital intermediate frequency signals are converted to analog radio frequency signals, amplified and radiated from transmit antennas (420).

Abstract: From the Publisher: Digital Baseband Transmission and Recording provides an integral, in-depth and up-to-date overview of the signal processing techniques that are at the heart of digital baseband transmission and recording systems. The coverage ranges from fundamentals to applications in such areas as digital subscriber loops and magnetic and optical storage. Much of the material presented here has never before appeared in book form. The main features of Digital Baseband Transmission and Recording include: -- a survey of digital subscriber lines and digital magnetic and optical storage; -- a review of fundamental transmission and reception limits; -- an encyclopedic introduction to baseband modulation codes; -- development of a rich palette of equalization techniques; -- a coherent treatment of Viterbi detection and many near-optimum detection schemes; -- an overview of adaptive reception techniques that encompasses adaptive gain and slope control, adaptive detection, and novel forms of zero-forcing adaptation; -- an in-depth review of timing recovery and PLLs, with an extensive catalog of timing-recovery schemes. Featuring around 450 figures, 200 examples, 350 problems and exercises, and 750 references, Digital Baseband Transmission and Recording is an essential reference source to engineers and researchers active in telecommunications and digital recording. It will also be useful for advanced courses in digital communications.

Abstract: A modem operating selectively in the voice frequency and higher frequency bands which supports multiple line codes. A DSP is used to implement different existing ADSL line codes on the same hardware platform. The modem negotiates in real time for a desired line transmission rate to accommodate line condition and service cost requirements which may be implemented at the beginning of each communication session by exchange of tones between modems. A four step MDSL modem initialization process provides line code and rate compatibility. The handshake protocol and receiver algorithm for CAP based MDSL modems allows reliable modem synchronization over severely amplitude distorted channels and makes use of a short length sequence to train a synchronizing equalizer at the receiver. The algorithm and corresponding training sequence to train the transmitter filter are provided. After training to this sequence, a matched filter or correlator detects the inverted sync sequence. Detection of the inverted sequence signals commencement of normal reference training of the demodulation equalizers. An internal state machine in an MDSL modem records and monitors line status and notifies state change to other MDSL and host processor. The protocol for exchanging line connection management messages is a simplified LCP for MDSL. In a DMT system, a transmitter filter reduces the length of effective channel impulse response. Iimplementation of the filter combines time domain convolution and frequency domain multiplication to reduce needed computation power. The filter coefficients update may occur through a feedback channel.