QoS considerations for DMT-based ADSL and VDSL systems

This Recommendation describes Asymmetric Digital Subscriber Line (ADSL) Transceivers on a metallic twisted pair that allows high-speed data transmission between the network operator end (ATU-C) and the customer end (ATU-R). It defines a variety of frame bearers in conjunction with one of two other services or without underlying service, dependent on the environment: 1) ADSL transmission simultaneously on the same pair with voice band service; 2) ADSL transmission simultaneously on the same pair with ISDN (Appendix I or II/G.961

ASEE Gulf Southwest Annual Conference, 2022

The Multi-Carrier Modulation is a technique used in breaking up the frequency spectrum into multiple sub-carriers, each of which is orthogonal to the other sub-carriers. The discrete multi-wavelet transform (DMWT) reduces the computation complexity and improves the performance efficiency. Most of the multi-carrier transmission systems use different techniques such as OFDM and single-carrier modulation techniques such as QAM for the ADSL technology. The bit error rate is poor, and the performance, flexibility, compatibility, and operational issue may arise during the information transmission. The DMT techniques combined with the ADSL can overcome these problems. The DMT partitions a broadband channel into many virtually independent, narrowband subchannels and maximizes the ADSL system's bit rate. The implementation of wavelets in the ADSL system improves the suitability, flexibility, and complexity of the multi-tone ADSL system. The paper compares the existing ADSL system problems with the DMWT-ADSL system. The main objective of this project work is to comparatively study the traditional multi-tone ADSL with the DWMT-ADSL, which provides a clear understanding of the application of wavelets in the broadband communication system. This paper is intended to share the results of the study. The method used is via simulation using MATLAB Simulink programs. We performed a detailed study of the ADSL system. The result of the simulation of the ADSL provides a broad view of how it works and transmits the data over the AWGN channel and demonstrates and documents the bit errors. The BER is the performance metrics compared using Meyer, DB-2 wavelets where the DB-2 shows low BER.

This paper considers the throughput of ADSL (Asymmetric Digital Subscriber Line) modems, used for high speed data transmission over relatively unreliable connections, e.g., copper telephone wires. The modem technique uses an error correcting code and interleaving. The settings include a grouping factor S which affects the amount of data per code word, the number of redundant bytes per code word (R) and the interleave depth D. The influence of these parameters on both the effective data transmission rate and the resulting error rate in the received signal are determined for two error situations: random errors and bursts of errors. An approximate analysis for the random error case of the throughput of a TCP (Transport Control Protocol) connection using an ADSL modem shows that maximum throughput is obtained for the highest values of S and R.

IEEE Transactions on Communications, 2003

This paper considers discrete multitone (DMT) modulation for multiuser communications when multiple users are supported by the same system, a zero-padding redundancy is employed at the transmitter output, and linear redundancy removal is used at the channel output. These users may have differing quality of service (QoS) requirements, as quantified by bit rate and symbol-error rate specifications, and are each assigned an equal number of subchannels. Our goal is to minimize the transmitted power, given the QoS specifications and subject to the knowledge of the channel and the second-order statistics of the colored interference at the receiver input. In particular, we find an optimum bit-loading scheme that distributes the bit rate transmitted across the various subchannels belonging to each user, and subject to this bit allocation, determine the precise subchannels assigned to each user, and the optimum transceiver, characterized by the input/output block transforms, and the redundancy removal operation. A major conclusion of this paper is that even though the optimum bit-rate allocation differs from the single-user case, the optimum transceiver does not. Further, it is determined entirely by the channel and interference conditions, and is unaffected by the QoS requirements.

IEEE Transactions on Communications, 2001

The performance degradation of filter-bank-based multicarrier transmission due to timing errors is investigated. The receiver is made of a fractionally spaced linear or decision-feedback equalizer designed for some sampling phase. The actual sampling phase is different and the impact of the difference on the performance is investigated. Sampling phase offset and jitter are considered. Besides, assuming the sampling phase error can be estimated the efficiency of various types of interpolation is investigated.

2007 IEEE International Conference on Acoustics, Speech and Signal Processing - ICASSP '07, 2007

Crosstalk is one of the main impairments of digital subscriber line (DSL) systems. To combat this impairment, several techniques were proposed in the literature that employ some form of precoding in the downstream. However, most existing bit allocation algorithms are not applicable to precoded DSL systems when the power in each transmission line is constrained. In this paper, we propose a bit allocation algorithm for this scenario. The proposed algorithm maximizes the bit rate given the available power. It somewhat extends single-user algorithms in that it sequentially allocates bit to the "best" user and tone. In the proposed algorithm we use a definition of "best" that is suitable for precoded systems. Simulation results show that the proposed algorithm achieves almost the same rates as those of power allocation algorithms, which do not take into account the discrete nature of the transmitted information.

World Applied Sciences Journal, 2008

Digital subscriber lines (DSL) offer the possibility to deliver broadband services over the existing telephone network. Before deploying DSL, the subscriber loops must be tested to see whether they can support high-speed data services, and at what rate. With regards to Voice over IP, VoIP converts analog voice signals into IP packets and distributes them across a WAN. VoIP is a delay-sensitive application. For POTS-quality voice, the network must be fine tuned end-to-end before implementing VoIP. This fine-tuning should incorporate a series of optimization techniques in order to improve the overall quality of service (QoS). Furthermore traffic shaping must be used to ensure VoIP reliability. There are two essential requirements to ensure VoIP quality: minimization of end-to-end delay and jitter. In this paper, the performance of QoS architecture was analyzed.. The basic metrics that were evaluated are the end-to-end delay of voice packets across the access network and the bandwidth consumed by a voice call.

IEEE Transactions on Signal Processing, 2002

In this paper, we develop solutions for the loading of digital subscriber loop (DSL) multicarrier (MC) systems that present constraints both on overall available energy and maximum energy per carrier. In the emerging G.DMT-based systems planned for high-throughput multimedia applications, the constraint on the peak-energy arises from spectral compatibility issues. However, until today, optimal solutions for loading peak-energy constrained MC systems do not seem explicitly developed in the literature. Hence, starting from suitable applications of the Kuhn-Tucker conditions, in this paper, we present the analytical relationships characterizing the optimal solution of the peak-energy-limited loading for the general case of concave "rate-functions," and then, we apply them in the context of the so-called "gap analysis." Thus, a low-complexity iterative algorithm implementing this solution is also developed, and its performance is numerically tested on several ANSI-standard asymmetric DSL (ADSL)-type loops impaired by crosstalk. Furthermore, a version of the presented loading algorithm that guarantees integer bit rates with low computational effort is also presented, and its performance is tested. The carried-out performance comparisons allow us to evaluate the throughput loss induced by peak-energy constraints in emerging ADSL-like services.

Adaptive filtering techniques were used for the first time for channel equalization and echo cancellation when the Digital Subscriber Line (DSL) were developed in the early 80's for the basic rate ISDN (BR-ISDN). Since then there has been much study regarding the feasibility of data transmission at higher bit rates which has also led to improved methods in channel equalization, spectral pulse shaping and matching hybrids for the transhybrid attenuation in addition to echo cancellation. This raises many technical questions regarding the feasibility of matching functions for the transhybrid attenuation at rates higher than the T1 rates. In this paper we investigate the possibility of such matching functions for certain CSA loops in Asymmetrical Digital Subscriber Line (ADSL). The Computer Aided Design, Simulation and Analysis techniques is used to study these issues. One of the main objective of this study is to determine if these matching functions could be used to realize matchi...