Digital Subscriber Line Access Research Articles

Twisted Pair Cable Fault Diagnosis via Random Forest Machine Learning

Applying the fault diagnosis techniques to twisted pair copper cable is beneficial to improve the stability and reliability of internet access in Digital Subscriber Line (DSL) Access Network System. The network performance depends on the occurrence of cable fault along the copper cable. Currently, most of the telecommunication providers monitor the network performance degradation hence troubleshoot the present of the fault by using commercial test gear on-site, which may be resolved using data analytics and machine learning algorithm. This paper presents a fault diagnosis method for twisted pair cable fault detection based on knowledge-based and data-driven machine learning methods. The DSL Access Network is emulated in the laboratory to accommodate VDSL2 Technology with various types of cable fault along the cable distance between 100 m to 1200 m. Firstly, the line operation parameters and loop line testing parameters are collected and used to analyze. Secondly, the feature transformation, a knowledge-based method, is utilized to pre-process the fault data. Then, the random forests algorithms (RFs), a data-driven method, are adopted to train the fault diagnosis classifier and regression algorithm with the processed fault data. Finally, the proposed fault diagnosis method is used to detect and locate the cable fault in the DSL Access Network System. The results show that the cable fault detection has an accuracy of more than 97%, with less minimum absolute error in cable fault localization of less than 11%. The proposed algorithm may assist the telecommunication service provider to initiate automated cable faults identification and troubleshooting in the DSL Access Network System.

Virtual signal‐integrity verification tool for copper twisted‐pairs using TDR

Time-domain reflectometry (TDR) is an important technique for verifying the impedance and quality of signal paths in components, interconnects, and transmission lines. However, the success of channel condition assessment through on-site interpretation of TDR echoes hinges on the skill and experience of the operator. This study presents a TDR simulator to assist loop diagnostics on copper twisted pairs widely used in current digital subscriber line (DSL) access networks. The simulator is developed based on established frequency-dependent cable models to synthesise realistic TDR echoes arising from various cable discontinuities. Modelling of arbitrary loop configurations and faults is accomplished by cascading multiple sub-lines with different characteristics through ABCD parameters modelling. The usability of the simulator is enhanced using a graphical user interface and its accuracy has been verified experimentally using TDR echoes obtained from commercial TDR testers. Since lengthy twisted pairs are deployed in real DSL access networks, the TDR simulator can be used to perform on-site simulation and verification during DSL network maintenance and troubleshooting, as well as to gain mastery of TDR handling while circumventing the need for bulky and costly cabling test beds. The simulator can also be useful to supplement the teaching of electromagnetics and high-frequency measurement.

SCDN: A Novel Software-Driven CDN for Better Content Pricing and Caching

In conventional content delivery networks (CDNs), where the content providers (CPs) are lack of the topology information, it is difficult for them to determine the content caching and pricing scheme. Furthermore, the small CPs cannot maintain their own cache servers as it is costly. To solve these problems, we propose a novel CDN architecture named software-driven CDN (SCDN) by leveraging the benefit provided by the software defined networks. In SCDN, the infrastructure provider (IP) hosts the cache servers at the back of the digital subscriber line access multiplexer, and it takes over the tasks to determine the content pricing and caching. By adopting a suitable revenue sharing scheme, SCDN achieves a win-win situation between IP and CPs. Simulation results show that with SCDN, the CPs can get about 25% more revenue than they can get in conventional CDNs.

Access and home networking technology standards

This IEEE Communication Standards Series addresses industry standards and the technologies used for the portion of the communications network nearest to the customer. This includes home networking technology used by a multitude of networked devices within the home or business to communicate with each other (local area networking) and to communicate with the public network (wide area networking). This Series also addresses the access technologies providing communications between the customer premises and the nearest traffic aggregation node of the public network, such as a digital subscriber line access multiplexer (DSLAM) or optical line terminal (OLT). This Series focuses on the industry standards for access and home networking including standards development organizations such as the International Telecommunication Union - Telecommunication Standardization Sector (ITU-T), IEEE, Internet Engineering Task Force (IETF), European Telecommunications Standards Institute (ETSI), and Alliance for Telecommunications Industry Solutions (ATIS), industry organizations such as the Broadband Forum, Cable- Labs, Metro Ethernet Forum (MEF), TeleManagement Forum (TMF), and open source entities such as Open Compute Project (OCP) and Open Platform for NFV (OPNFV). Article submissions related to the work of these and other relevant industry standards bodies are invited for future issues of IEEE Communications Standards. The article in this issue is written by experts working on fixed broadband access technologies and participating in several SDOs as well as cooperative projects. From a customer point of view, not only is downstream data rate important but also upstream.

Analytical Framework for Preliminary Planning of Very High-Speed Digital Subscriber Line Access Networks

In this paper, we introduce an analytical framework for the performance evaluation of the VDSL2-based access systems. It allows for the obtaining of approximations of the achievable bit rate per user, taking into account several factors, such as the bit-loading limitation per sub-carrier; interference scenario, including the number and positions of the active interferers along the cable; crosstalk statistics; and vectoring. A closed-form expression for the maximum sub-carrier frequency that can be loaded with the maximum number of allowed bits is also presented. Formulas are obtained assuming log-normal statistics for the signal-to-interference-plus-noise ratio (SINR) per sub-carrier. The validity of the proposed formulas has been assessed by computer calculations. A very good agreement between the exact and the approximated bit rates has been obtained. The framework can be used for preliminary design of VDSL2 systems in terms of the bit rate coverage, as well as to analyze performance of other access technologies such as ADSL and G.fast.

Access and home networking technology standards

This IEEE Communication Standards Series addresses industry standards and the technologies used for the portion of the communications network nearest to the customer. This includes home networking technology used by a multitude of networked devices within the home or business to communicate with each other (local area networking) and to communicate with the public network (wide area networking). This Series also addresses the access technologies providing communications between the customer premises and the nearest traffic aggregation node of the public network, such as a digital subscriber line access multiplexer (DSLAM) or optical line terminal (OLT). This Series focuses on the industry standards for access and home networking including standards development organizations such as the International Telecommunication Union - Telecommunication Standardization Sector (ITU-T), IEEE, Internet Engineering Task Force (IETF), European Telecommunications Standards Institute (ETSI), and Alliance for Telecommunications Industry Solutions (ATIS), industry organizations such as the Broadband Forum, Cable- Labs, Metro Ethernet Forum (MEF), TeleManagement Forum (TMF), and open source entities such as Open Compute Project (OCP) and Open Platform for NFV (OPNFV). Article submissions related to the work of these and other relevant industry standards bodies are invited for future issues of IEEE Communications Standards. The article in this issue is written by experts working on fixed broadband access technologies and participating in several SDOs as well as cooperative projects. From a customer point of view, not only is downstream data rate important but also upstream.

Measurement and Test Performance for Integrated Digital Loop Carrier for White Noise Impairment Using Interleaved Mode

ABSTRACT This paper presents results of measurement and test performance for integrated digital loop carrier (IDLC) technology. The study focuses on cable modem termination systems (CMTSs) that are reported on assortments of operating parameters to the end user based on upstream and downstream modes that are incorporated with statistical analysis approach. The study focuses on the statistical analytical measurement for noise margins on a particular type of loops--white noise Keywords: integrated digital loop carrier, DSL, broadband, interleaved mode INTRODUCTION Service providers in the past have extensively used digital loop carriers (DLC) in delivering reliable, robust and high quality voice service to end users. Recently, telecommunications network providers (TNP) improve and change their path in broadband technologies for better services and costs reduction to customers. As a result, they increased the number of lines with extended distances from Central Office (CO) with high quality of services in voice and data. From analog technology in plain old telephone services (POTs) to digital in DLC, TNP have made great stride and break through to service providers and end-users. Digital loop carrier (DLC) technology is based on digital techniques to provide large services to users via copper lines. In today technologies, IDLC systems are broadly installed in delivering telecommunications services. Significant wiring and advantages of cost can be profited with IDLC at remote locations. In this work, the study illustrates the statistical analysis for the results of measurement of a test performance for integrated digital loop carrier (IDLC) type of white noise impairment. This paper is arranged as follows: A review of literature provides an overview of voice over digital subscriber line (VoDSL), digital subscriber line (DSL), and carrier serving area (CSA). A description of the DLC and IDLC are then presented, with a discussion and network setup following. Regression analysis is then presented, with statistical analysis and hypothesis testing on the difference between the two means, of the noise margin, of the upstream and downstream cases in the interleaved mode setup completing the section. The paper is completed with a summary of the results and the conclusion. LITERATURE REVIEW Early studies showed that the first generation integrated access systems served as a platform for delivering voice, data and voice services over multiple T1/E1 lines and OC-3 fiber link. Later studies showed that the universal digital loop carrier system (UDLC), evolved into what are now known as the integrated digital loop carrier (Opara & Etnyre, 2010) Musa, Akujuobi, & Mir (2007) indicated that when measuring call quality, three categories of study include listening quality, conversational quality and transmission quality. According to Musa et al., the objective of call quality measurement is to obtain a reliable estimate of one or more within the above categories using either subjective or objective testing methods. A baseline test for the listening quality (LQ) using voice over digital subscriber line (VoDSL) access technology has been studied (Musa, Opara, Shayib, & El-Aasser, 2010). Researchers used voice/listening quality (V/LQ) transmission with voice compression while continuously downloading files. Indeed, those results enable the efficiency of the LQ and its statistical analysis based on a digital subscriber line (DSL) service at level 1.5M/384K for each American National Standards Institute (ANSI) and carrier serving area (CSA) loops. Furthermore, based on the experimental VoDSL network architecture and the following DSL service levels 640K/ 640K, 1.5M / 384K, 3.0M/ 512K, and 1.5M/ 256K for each ANSI/CSA loops by using voice quality transmission testing with voice compression while continuously downloading files, it was found that on certain loops, all eight derived lines were not supported on IADs for VoDSL solution (Musa et al. …

Fault diagnosis in DSL networks using support vector machines

The adequate operation for a number of service distribution networks relies on the effective maintenance and fault management of their underlay DSL infrastructure. Thus, new tools are required in order to adequately monitor and further diagnose anomalies that other segments of the DSL network cannot identify due to the pragmatic issues raised by hardware or software misconfigurations. In this work we present a fundamentally new approach for classifying known DSL-level anomalies by exploiting the properties of novelty detection via the employment of one-class Support Vector Machines (SVMs). By virtue of the imbalance residing in the training samples that consequently lead to problematic prediction outcomes when used within two-class formulations, we adopt the properties of one-class classification and construct models for independently identifying and classifying a single type of a DSL-level anomaly. Given the fact that the greater number of the installed Digital Subscriber Line Access Multiplexers (DSLAMs) within the DSL network of a large European ISP were misconfigured, thus unable to accurately flag anomalous events, we utilize as inference solutions the models derived by the one-class SVM formulations built by the known labels as flagged by the much smaller number of correctly configured DSLAMs in the same network in order to aid the classification aspect against the monitored unlabeled events. By reaching an average over 95% on a number of classification accuracy metrics such as precision, recall and F-score we show that one-class SVM classifiers overcome the biased classification outcomes achieved by the traditional two-class formulations and that they may constitute as viable and promising components within the design of future network fault management strategies. In addition, we demonstrate their superiority over commonly used two-class machine learning approaches such as Decision Trees and Bayesian Networks that has been used in the same context within past solutions.

An Improved Particle Swarm Optimization Based on Deluge Approach for Enhanced Hierarchical Cache Optimization in IPTV Networks

In recent years, IP network has been considered as a new delivery network for TV services. A majority of the telecommunication industries have used IP network to offer on-demand services and linear TV services as it can offer a two-way and high-speed communication. In order to effectively and economically utilize the IP network, caching is the technique which is usually preferred. In IPTV system, a managed network is utilized to bring out TV services, the requests of Video on Demand (VOD) objects are usually combined in a limited period intensively and user preferences are fluctuated dynamically. Furthermore, the VOD content updates often under the control of IPTV providers. In order to minimize this traffic and overall network cost, a segment of the video content is stored in caches closer to subscribers, for example, Digital Subscriber Line Access Multiplexer (DSLAM), a Central Office (CO) and Intermediate Office (IO). The major problem focused in this approach is to determine the optimal cache memory that should be assigned in order to attain maximum cost effectiveness. This approach uses an effective Grate Deluge algorithm based Particle Swarm Optimization (GDPSO) approach for attaining the optimal cache memory size which in turn minimizes the overall network cost. The analysis shows that hierarchical distributed caching can save significant network cost through the utilization of the GDPSO algorithm.

Integration of QoS Metrics, Rules and Semantic Uplift for Advanced IPTV Monitoring

Increasing and variable traffic demands due to triple play services pose significant Internet Protocol Television (IPTV) resource management challenges for service providers. Managing subscriber expectations via consolidated IPTV quality reporting will play a crucial role in guaranteeing return-on-investment for players in the increasingly competitive IPTV delivery ecosystem. We propose a fault diagnosis and problem isolation solution that addresses the IPTV monitoring challenge and recommends problem-specific remedial action. IPTV delivery-specific metrics are collected at various points in the delivery topology, the residential gateway and the Digital Subscriber Line Access Multiplexer through to the video Head-End. They are then pre-processed using new metric rules. A semantic uplift engine takes these raw metric logs; it then transforms them into World Wide Web Consortium's standard Resource Description Framework for knowledge representation and annotates them with expert knowledge from the IPTV domain. This system is then integrated with a monitoring visualization framework that displays monitoring events, alarms, and recommends solutions. A suite of IPTV fault scenarios is presented and used to evaluate the feasibility of the solution. We demonstrate that professional service providers can provide timely reports on the quality of IPTV service delivery using this system.

Unbundling in Current Broadband and Next-Generation Ultra-Broadband Access Networks

This article overviews the methods that are currently under investigation for implementing multi-operator open-access/shared-access techniques in next-generation access ultra-broadband architectures, starting from the traditional “unbundling-of-the-local-loop” techniques implemented in legacy twisted-pair digital subscriber line access networks. A straightforward replication of these copper-based unbundling-of-the-local-loop techniques is usually not feasible on next-generation access networks, including fiber-to-the-home point-to-multipoint passive optical networks. To investigate this issue, the article first gives a concise description of traditional copper-based unbundling-of-the-local-loop solutions, then focalizes on both next-generation access hybrid fiber–copper digital subscriber line fiber-to-the-cabinet scenarios and on fiber to the home by accounting for the mix of regulatory and technological reasons driving the next-generation access migration path, focusing mostly on the European situation.

Design and control of next generation distribution frames

In today’s access networks, the permutation of circuits connecting the subscriber lines to Plain Old Telephone Service (POTS) and to Digital Subscriber Line Access Multiplexers (DSLAMs) occurs in the Main Distribution Frame (MDF) and is still manually configured. However, new market regulations and new policies adopted by operators require increasingly more frequent permutations, making the manual configuration activity particularly expensive. Very recently, Automated MDFs (AMDFs) have been developed to provide inexpensive and almost real-time switching capability. Our study, based on more than 50years of research activities on architectures for circuit switching, is focused on overcoming the limits of classical architectures. In fact, strictly non-blocking multistage networks are too expensive, as a consequence of the large number of ports they require (sometimes exceeding 100,000). In addition, rearrangeable multistage networks can temporarily interrupt active circuits, affecting the performance of ADSL subscriber lines.As a possible solution to these problems, we propose the design of AMDFs based on Non-Interruptive Rearrangeable (NIR) networks. We show how to optimize the routing control to minimize the setup time of a circuit and to exploit output grouping. We believe that the solution described above is not only relevant for the theory of multistage interconnection networks, but also for the design and operation of large AMDFs.

IPTV Multicast With Peer-Assisted Lossy Error Control

Internet protocol television (IPTV) systems employ IP multicast to deliver television programs to end-users. To provide reliable IPTV services over the error-prone digital subscriber line (DSL) access networks, a combination of multicast forward error correction and unicast retransmissions is employed to mitigate the impulse noise in DSL links. In current systems, the error control function is provided by special retransmission servers. In this paper, we propose an alternative distributed solution where the burden of packet loss repair is partially shifted to end-user set-top boxes. Using a peer-assisted repair (PAR) protocol, we demonstrate how packet repairs can be delivered in a timely, reliable, and decentralized manner using the combination of server-peer coordination and redundant repairs. We also show that this distributed protocol can be seamlessly integrated with an application-layer source-aware error protection mechanism called forward and retransmitted systematic lossy error protection (SLEP/SLEPr). Analysis and simulations show that this joint PAR-SLEP/SLEPr framework not only efficiently improves the resistance to the impulse noise but also effectively mitigates the bottleneck experienced by the retransmission servers, thus greatly enhancing system scalability.

Design of reliable fiber‐based distribution networks modeled by multi‐objective combinatorial optimization

SUMMARYIn this work, we investigate the planning of hybrid fiber/very high bit rate digital subscriber line (HFV) access networks. This HFV variant is considered as an alternative to passive optical access network. It consists of implementing optical fibers in the access network part from the central office to the street cabinets, whereas the very high bit rate digital subscriber line technology is used in the last meter part, from street cabinets to subscribers. Firstly, we discuss the different tasks of this planning problem. We model this planning problem as a multi‐objective optimization problem, where different conflicting objectives have to be optimized at the same time. We consider network costs and network reliability. This problem is solved by two different approaches: the classical single‐objective optimization (SOO) and the multi‐objective optimization (MOO), which is a recent optimization approach that is gaining an increasing interest in practical optimization problems. MOO solves the problem by searching for different optimal trade‐offs between the optimization objectives. The performances of SOO and MOO are analyzed and compared with each other using three network instances. Copyright © 2012 John Wiley & Sons, Ltd.

NoBot: Embedded malware detection for endpoint devices

NoBot is a novel malware detection system that employs packet classification and distinct counting techniques to achieve reliable detection and identification of malware by observing the traffic to and from a network-connected host. The solution is designed to be economically incorporated into endpoint devices, such as Ethernet switches, Gigabit passive optical network (GPON) devices, and digital subscriber line access multiplexers (DSLAMs) leveraging the integral features of the hosting device, such as packet classification, packet counting, packet-forwarding features, and the computing resources of the control processor. NoBot combines these features with deep packet inspection and distinct counting to detect the presence of malware with a low rate of false positive detections. The NoBot software has been incorporated into a Linux device driver, installed into an Android-based smart phone, and implemented as a preprocessor module for the open source Snort Intrusion detection and prevention System (IDS/IPS).

Market Coverage and Service Quality in Digital Subscriber Lines Infrastructure Planning

Digital subscriber lines (xDSL) belong to a family of technologies that provide the ability to transmit digital data over local telephone (copper) infrastructure. As the second most popular broadband platform in the United States, it is estimated that over twenty-five million xDSL lines are in service, capturing nearly 30 percent of the U.S. broadband market. While the service range of xDSL is somewhat limited, often extending to a maximum of 18,000 feet from a central office (CO), available bandwidth also decays as distance increases from the CO. As a result, there are often marked disparities in the quality of xDSL service within market areas. This article proposes a bi-objective location model for maximizing both service coverage and quality of coverage in siting digital subscriber line access multiplexers (DSLAMs). An application of the developed model highlights important implications for telecommunication policy.

Power-efficient copper access

While the data rate has traditionally been a key performance measure for copper access technology, power efficiency is becoming increasingly important. Line drivers are receiving significant focus since they account for roughly 50 percent of the total power consumption of a digital subscriber line access multiplexer. One approach to reduce this power consumption is to insightfully exploit currently available features. The low power mode (L2), as standardized for Asymmetric Digital Subscriber Line 2 (ADSL2/2plus), can contribute to huge power savings by reducing transmit power during periods of low user traffic. However, effective single or multi-line management is required to ensure that time-varying crosstalk generated by the lines exiting L2 does not jeopardize the stability of neighboring lines. Another approach is to develop an advanced, scalable, joint optimization of power allocation to tones on multiple lines (potentially time varying), with an explicit objective to lower power consumption as well as to optimize the data rate.

Femtocells [Guest Editorial

Femtocells are destined to transform the way mobile operators build their cellular networks and grow their coverage and capacity. Femtocells are small base stations operating in the licensed cellular bands. They are so small and inexpensive, and transmit at such low power, that they are meant to be placed in individual homes and backhauled onto the operator?s network via conventional digital subscriber line (DSL) or cable broadband access (or, when available, fiber).

Bandwidth provisioning in ADSL access networks

AbstractWe consider an ADSL access network consisting of subscribers, digital subscriber line access multiplexers (DSLAMs), metro Ethernet switches and a broadband remote access aggregation server (BRAS). We obtain expressions for dimensioning the access network in the upstream direction. Specifically, we show that the bandwidth required at each DSLAM, metro Ethernet switch, and BRAS can be expressed as an exponential function of the subscribers in a log scale when the number of subscribers does not surpass a certain value. After this value, it grows linearly as a function of the subscribers. Copyright © 2009 John Wiley & Sons, Ltd.

Analytical Model for Hierarchical Cache Optimization in IPTV Network

In an IPTV network, video on demand and other video services generate large amount of unicast traffic from video hub office (VHO) to subscribers and, therefore, require additional bandwidth and equipment resources in the network. To reduce this traffic and overall network cost, a portion of the video content (the most popular titles) may be stored in caches closer to subscribers, e.g., in a digital subscriber line access multiplexer (DSLAM), a central office (CO), or in an intermediate office (IO). The problem becomes to minimize cost by optimizing cache memory placement and amount. We present an analytical model of hierarchical cache optimization. This model depends on several basic parameters: traffic volume, cache hit rate as a function of memory size, topology (i.e. number of DSLAMs, service routers at CO, service switches at IO locations), and cost parameters. Some reasonable assumptions about a network cost structure and a hit rate function allow us to obtain an analytically optimal solution for the problem. We then analyze the factors that affect this solution.