Development, Training And Implementation Of Test Automation For Adsl Interoperability And Reliability Studies

Energy-saving by low-power modes in ADSL2

This paper presents a study of the effects of bridged taps on very high-speed digital subscriber line (VDSL) transmission systems. It is shown that the short bridged taps; which affect VDSL signals, are much more damaging than the longer bridged taps, which affect other xDSL signals, such as high-rate digital subscriber line (HDSL) and asymmetric digital subscriber line (ADSL). Specifically, short bridged taps introduce a lot of linear distortion in the loop's transfer function. In addition, they also tend to introduce more overall propagation loss than longer bridged taps. The peak-power-to-average-power ratio (PAR) of the signal increases for the loop with short bridged taps, and thus more AID bits are needed in the implementation of a digital VDSL transceiver as compared to the loop with long bridged taps. The performance of various equalizer structures is discussed in the presence of a severe channel distortion caused by the bridged tap.

The design and optimization of the high-speed digital subscriber line (HDSL) need powerful computational strategies. Traditional techniques of distributing poles and zeros on Smith charts generally do not work. In the past, such approaches have lead to suboptimal designs for applications where the data capacity sought is considerably less than the Shannon capacity of the lines. Typical subscriber loops are less than perfect and for the current demands on the HDSL at T1/T2 and El rates every possible venue for the HDSL design needs to be investigated, if not exploited. In this Chapter, flexible computational techniques are presented that explore and optimize system components in view of the operating environment of the HDSL and/or the asymmetric digital subscriber line (ADSL) and inherent limitations of system components. The optimization occurs automatically by forcing the computer to track the effects of incremental changes of the subsystem performance (e.g., echo cancelers or equalizers), or the component values (Rs and Cs in the matching circuits) in context to the functional constraints of the (HDSL, ADSL, duplex, dual-duplex, triplex, etc.) line in conjunction with various subscriber loop environments (CSA loops, loops <18 kft., American, Australian, European, ANSI, ETSI, etc.)

Broadband services require data rates that can only be achieved by using relatively high spectrum frequencies. At such high frequencies, the DSL (Digital Subscriber Line) signal is more susceptible to external noise sources, such as radio frequency interference and impulsive noise. This paper aims to characterize how the impulsive noise impacts on services and applications for a broadband system using an ADSL2+ loop. The first approach was to use the impulsive noise defined in the standards G.996.1 (Test Procedures for DSL Transceivers) from ITU-T and TR-048 (ADSL Interoperability Test Plan) from DSL Forum. In this approach we have also used a HDSL (High Bit Rate DSL) and white noise disturbers on the line. The impulsive noises c1 and c2 (defined in G.996.1) are injected into the circuit at the CO (Central Office) end and CPE (Customer Premises Equipment) end of the loop simulator. Additionally, it was analyzed the spikes of noise's impact on the ADSL2+ line. In this case, pre-defined models of NEXT (Near-end crosstalk) and white noise are injected on CO and CPE side, simultaneously. Metrics like packet rate, lost packet count, bandwidth, short-term average transfer delay, and errored seconds are used to characterize the DSL loop under the noise impairments. (Less)

Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation used in a variety of broadband systems, such as asymmetric digital subscriber lines, very-high-speed digital subscriber lines, digital video and audio broadcasting, and wide local area network standards. OFDM is a promising solution achieving high data rates in a mobile environment. In wireless communication systems, signal distortion and attenuation in transmission caused by multipath effects makes it necessary to obtain knowledge related to the channel impulse response using channel estimation to provide compensation. This study combined a back propagation neural network for the estimation of channel and compensation signals with a genetic algorithm to improve performance and the convergence rate. We compared bit error rates and the mean square error of the proposed neural network with that of the conventional neural network, the least square (LS) algorithm, and the minimum mean square error (MMSE) algorithm in existing OFDM channel environments. Our results demonstrate that the proposed algorithm outperforms the LS algorithm and is on par with the MMSE algorithm.

System-on-a-chip (SoC) is now a trend in digital design because it gives a lot of advantages over discrete electronic based product such as higher speed, lower power consumption, smaller size, lower cost etc. Reconfigurable platforms such as FPGA, CPLD, and PLD are now being used for designing and implementing SoC due to their low cost, high capacity and tremendous speed. In this project single chip Orthogonal Frequency Division Multiplexing (OFDM) transmitter and receiver have been designed using Verilog HDL. OFDM is a multi carrier modulation technique used in the various digital communication systems like 3G GSM, WiMAX and LTE etc. The main advantage of this transmission technique is its robustness to channel fading in wireless communication environment. There are many applications of OFDM in communication such as digital audio broadcasting, Asynchronous Digital Subscriber Line (ADSL) and High bit-rate Digital Subscriber Line (HDSL) systems. In OFDM, two algorithms digital signal processing algorithm Fast Fourier transform (FFT) and Inverse Fast Fourier Transform (IFFT) are mainly involved. The 8-point IFFT/FFT Decimation-In-Frequency (DIF) with radix-2 algorithm has been analyzed and incorporated in the design. The design has been simulated on the FPGA platform with Altera's Quartus II simulator. Simulation results show that each of the modules of the proposed OFDM is working as desired. The test output achieved from the simulation result of the OFDM has been verified with that of the MATLAB output.

In this chapter, we will focus on ADSL modem interoperability and DSLAM reliability testing. The interoperability test is used to perform the reliability test. In this test, we use a single modem against different ports of DSLAM to check the performance of each port. This provides information on how reliable DSLAM ports are in the broadband network. We will also focus on wireless-related tests and the emerging WiMax technology.

The requirement for an automated test system has immensely increased due to the realization that manual testing is associated with additional resources and staffing constraints. In order to achieve a competitive edge, reduced development cost, timely product delivery, and product quality are mandatory in today's organization. Manual testing requires skilled operators that increase cost, time, and product delivery. The low cost computer based automated system helps to get an edge by fulfilling these organizational demands. In this paper, an automated testing system has been developed to support functional testing of Nortel Network's modem system (1-Meg SUT). The modem is an inherently complex asymmetric digital subscriber line (ADSL) product and its testing is far more complex than just verification of process faults. The complexity of ADSL system renders automated test system an important and imperative part of ADSL testing. The subject paper demonstrates the indispensable need of automated test system for ADSL testing and its advantages in providing a competitive edge for the organization.

In this paper the general ADSL (asymmetric digital subscriber line) noise environment is reviewed in the context of the telephone loop plant. Special attention is given to the unique unidirectional transmission nature of ADSL. A set of noise environments is presented for related computer simulation studies and hardware tests. A set of mid-CSA test loops is also proposed for performance evaluation under conditions of T1 NEXT interference. To simplify calibration procedures, noise and loop models are revealed in FIR (finite impulse response) filter form and can be measured in dB loss or dBm/Hz power density terms. A subchannel signal to noise ratio (SNR) based computer simulation method is then used to estimate potential ADSL performance under different noise environments for different serving areas. >

Revisiting Mackay Online

The cumulative emission field resulting from the large-scale deployment of asynchronous digital subscriber line (ADSL) is determined using the model introduced by Papatsoris and Flintoft (see ibid., vol.36, no.13, p.1171-2, 2000) and the implications on medium frequency broadcasting are assessed. Spectrum management issues of ADSL are dealt with and mitigation techniques for minimising potential interference are proposed.

This paper presents the design and implementation of novel decimation filter structure for high speed asymmetric digital subscriber line (ADSL). Existing ADSL circuits use comb-FIR-FIR decimation filter structures, which have low throughput, more hardware and high power consumption. Unlike existing ADSL circuits, we design a novel high speed filter architecture and implement it using the minimal signed digit (MSD) representation. The MSD representation is suitable for common subexpression elimination, and it significantly reduces the number of adders required for the filter synthesis. Each digital-filter structure is simulated using Matlab, and its complete architecture is captured using DSP Blockset and Simulink. The resulting filter architecture has higher throughput, less hardware and consumes less power than the comb-FIR-FIR and comb-IIR-FIR architectures. The filter has been implemented on Xilinx FPGA using Virtex-2 technology. Compared to the comb-FIR-FIR and the comb-IIR-FIR architectures, the designed decimation filter architecture contributes to a hardware saving of 82% and 74%, respectively; in addition, it reduces the power dissipation by 91% and 79%, respectively.

IP over WDM has emerged as a winning network architecture to facilitate today's IP centric Internet. Although the total amount of bandwidth demands keeps increasing, there still exists a huge gap between the increasing full-wavelength capacity and the existing low-rate IP traffic. Efficiently grooming low-rate traffic stream to high-capacity lightpaths helps to alleviate the bandwidth mismatch, effectively improve the network resource utilization, and reduce the overall network cost. In this paper, we study traffic grooming problem in IP over WDM framework. The problem of minimizing the total number of transmitters and receivers in the networks is formulated as an integer linear programming (ILP) optimization problem. The ILP formulation produces optimal solutions for static traffic demands. However, applying the ILP solution to large and realistic networks is not practical due to its prohibitively large computation time. We therefore develop a heuristic algorithm, namely traffic aggregation algorithm. A significant improvement on wavelength utilization is observed in our experiments when we use our traffic aggregation algorithm. I. INTRODUCTION The popularity of the Internet and Internet protocol (IP)- based Intranet is promising enormous growth in data traffic originating from hosts that are IP endpoints. This growth is being fueled by various applications such as those driven by World-Wide-Web (WWW) and by the indirect impact of increased computing power and storage capacity at the end systems. The advent of new services with increasing intelligence and the corresponding bandwidth demands are further adding to the traffic growth. New access technologies such as Asymmetric Digital Subscriber Line (ADSL), High- bit-rate Digital Subscriber Line (HDSL), and fiber to the home (FTTH) would remove the access bottlenecks and enforce an even faster growth of demand on the backbone network. These changing trends have led to a fundamental shift in traffic patterns and the traffic is mostly due to data communications. In the past, the amount of data traffic on carrier networks was smaller than the voice-centric traffic. Therefore, the carrier networks were designed to primarily support voice traffic, and the data traffic was transmitted using the voice channels. Now, the core networks are being designed primarily for data traffic with voice support at the edges. The voice can be carried in the core networks using voice-over-IP or similar paradigms. To meet these growing demands, WDM will continue to emerge as a dominating trend for use in backbone networks. The research reported in this paper is funded in part by the National Science Foundation under grant ANI-0087746, grant ANI-0434872 and grant ANI- 0323374. Architectures will include to satisfy the need for better quality of service (QoS), protection, and availability guarantees in IP networks. WDM significantly increases the fiber capacity utilization by dividing the available bandwidth into non-overlapping wavelength channels, supporting connections between the two end nodes by establishing an all-optical channel, namely lightpath, which allows use of different formats, bit-rates, and protocol transparency. At the same time, most network designers believe that IP is going to be the common traffic convergence layer in communication networks. Consequently, IP over WDM has been envisioned as the winning combination of the network architecture.

Multidimensional TCM schemes can be used to improve the performance of the asymmetrical digital subscriber line (ADSL). The operating principle of how M-D (multidimensional) TCM works in an ADSL channel is analysed and criteria for evaluating and choosing effective multidimensional TCM schemes are described. The results of a simulation for evaluating the performance is presented.

ADSL (Asymmetric Digital Subscriber Line) adopts modulation scheme called DMT (Discrete multi tone), a multi carrier system. The process of allocating bits into various sub-channels is called bit-loading. In this paper, a new bit-loading algorithm that reduces the power required to transmit data is proposed. Comparison on power cut back with other algorithms is presented. Also the implementation of the algorithm in the transmitter is discussed. A Matlab simulation model has been developed to simulate ADSL transmitter (with bit-loading), channel and receiver. The ADSL system with bit-loading algorithm is also implemented in hardware using TT's DSK6713 kit and comparison of software and hardware results are tabulated.