Showing papers on "High-bit-rate digital subscriber line published in 2009"

Computationally efficient joint partial crosstalk cancellation and multi-user power control algorithm in xDSL networks

Abstract: Far-end crosstalk (FEXT) is the major limitation to achieve high data rates in very high bit rate digital subscriber line (VDSL) systems. Full crosstalk cancellation (FCC) techniques have been proposed to mitigate the effect of crosstalk. However, these are too complex for application in typical VDSL binders. Considering the fact that there are only a few strongest cross-talkers that contribute to main part of crosstalk, the crosstalk cancellation can be simplified to line selection (LS), tone selection (TS) and joint line-tone selection (JLTS) partial crosstalk cancellation (PCC). These all result in much less online complexity. In this paper, first, we propose a new modified JLTS algorithm with significantly lower initialisation complexity than the optimal JLTS (OJLTS) algorithm and approximately with similar performance. Then a novel joint algorithm is presented that combines the multi-user power control technique with the PCC scheme to achieve near the capacity rates. We also consider dynamic online complexity constraint for each user. This joint algorithm leads to a much larger online complexity reduction (around 60% for long lines) and higher data rates at the expense of slightly higher initialisation complexity. The performance of the proposed algorithm is verified by some simulation results and compared with current algorithms that use flat power spectral densities (PSDs) and other existing joint algorithms. Copyright © 2009 John Wiley & Sons, Ltd.

Wireless digital code division multiple access (cdma) communication system

Abstract: PROBLEM TO BE SOLVED: To provide a wireless digital CDMA communication system which supports all types of voice and data communications while utilizing the minimum frequency bandwidth for each application. SOLUTION: This system efficiently allocates ISDN bandwidth in response to a demand by a subscriber. When a subscriber unit is started, the system sets a channel and generates a spectrum spreading code necessary for supporting a maximum capacity channel required by the subscriber unit. It is not performed that part of the communication bandwidth is reserved until actually required by a subscriber unit. Since a call setup including the assignment of a spectrum spreading code is performed at the beginning of a call from a subscriber unit, a subscriber unit can quickly gain access to part of the frequency spectrum necessary for supporting a required specific application. COPYRIGHT: (C)2010,JPO&INPIT

Method and apparatus for high speed data services

Abstract: A system that incorporates teachings of the present disclosure may include, for example, receiving, by a first line card coupled to minimally twisted or non-twisted pair cables, a very high digital subscriber line signal, modifying the very high digital subscriber line signal for transmission over the minimally twisted or non-twisted pair cables to generate an updated very high digital subscriber line signal that overcomes a transmission deficiency, and transmitting from the first line card the updated very high digital subscriber line signal to a second line card to cause the second line card to receive the adapted very high digital subscriber line signal at a desired signal quality and convert the updated very high digital subscriber line signal to a very high digital subscriber line signal for presentation of interactive television services at the customer premise equipment. Other embodiments are disclosed.

Design, Simulation and Implementation of Asymmetric Digital Subscriber Line Modem on DSP Kit

Abstract: In this paper, design, simulation and implementation of Asymmetric Digital Subscriber Line (ADSL) modem is presented which can be applied to different telephone networks. The ADSL modem is modeled and simulated under the MATLAB version 7.3 (R2006b) environments by which the simulation is achieved for both the downstream and upstream directions of the modem. The ADSL modem with a transmission throughput between 640 kbps and 6 Mbps operating over most of existing telephone subscriber loops has been implemented on TI TMS320C6713 DSP for consumer multimedia applications. Except the Analog Front End, all the basic building blocks of the ADSL modem functionalities are implemented with DSP platform. We use Real-Time Data Exchange (RTDX) as a way to debug and test our DSP designs. INTRODUCTION Asymmetric Digital Subscriber Line (ADSL) is a high speed data transmission technology that allows reuse of existing copper phone line [1]. It allows up to 8 Mbps data transmission on downstream and 640 Kbps on upstream[2]. To increase the spectral efficiency of the available bandwidth, ADSL employs a transmission technique based on Multicarrier modulation, namely, discrete multitone (DMT) [3, 4]. ADSL uses two separate frequency bands, the band from 25.875 kHz 138 kHz is used for upstream communication, while 138 kHz – 1104 kHz is used for downstream communication. DMT divides the available bandwidth into N parallel subchannels or tones, by means of an N-point inverse fast Fourier transform (IFFT). At the transmitter, each tone is modulated by quadrature amplitude modulation (QAM) and IFFT transformed to obtain a time domain signal. At the receiver, an N-point FFT can be used for demodulation. Prepending each data block after IFFT modulation with a cyclic prefix ensures that the subchannels remain independent after transmission over a channel. If the order of the channel is smaller than the cyclic prefix length, ν, the transmitted signal can easily be recovered by the so-called frequency domain equalizers (FEQs). Besides equalization, echo cancellation is required to separate upstream and downstream signals and to enable efficient bidirectional communication over the same telephone wire. Echo cancellation can improve the reach and/or noise margin of an ADSL system by allowing both

Subscriber unit of wireless digital code division multiple access (cdma) communication system

Abstract: PROBLEM TO BE SOLVED: To provide a CDMA wireless digital communication system which supports all types of voice and data communications while utilizing the minimum amount of frequency bandwidth for each application.SOLUTION: The system efficiently allocates ISDN bandwidth on demand by a subscriber. Upon initialization of a subscriber station unit, the system establishes a channel and generates necessary spectrum spreading codes to support the highest capacity channel desired by the subscriber station unit. A portion of the communication spectrum bandwidth is not reserved until actually required by the subscriber station unit. Since the call setup is performed at the beginning of a call from the subscriber station unit, including the assignment of spectrum spreading codes, the subscriber station unit can quickly gain access to the portion of the frequency spectrum that is necessary to support a required particular application.