Recent changes in user employment of Internet based services, new deployment technologies for mobile networks as well as an ongoing realisation of fixed and mobile converged networks e.g. the EU FP7 project COMBO, are significant examples of enablers for increasing demands on DSL links. Investigating cross-layer dependencies between all layers in the OSI reference model becomes increasingly important. In this paper we present an analytical model and experimental results for the relation between impulse noise on a VDSL2 link and the effect this have on the network layer packet loss. We show how the packet loss rate is dependent not only on the disturbance signal level and periodicity but also on the link utilisation.

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Analytic model for cross-layer dependencies in VDSL2 access networks

This paper aims to characterize how the impulse noise impacts on services and applications for a broadband system using an ADSL2+ (Asymmetric Digital Subscriber Line, extended bandwidth) loop. The first approach employs the impulse noise defined in t he G.996.1 (Test Procedures for DSL Transceivers) and TR-048 (ADSL Interoperability Test Plan) recommendations from ITU-T and DSL Forum, respectively. The second approach assesses system performance under REIN (Repetitive Electrical Impulse Noise) disturbance, which often occurs in the PSTN (Public Switched Telephone Network). REIN does not disturb the telephone service, however being quite harmful to ADSL. Metrics at packet level, as packet rate, lost packet count, bandwidth, short-term average transfer delay, and errored seconds, are used in order to characterize the DSL loop subjected to the referred noise impairments. After that, perceptual metrics are used along with QoS (Quality of Service) objective metrics to identify the impulse noise impact to the final user, leading to a QoE (Quality of Experience ) analysis of the system.

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Impulsive Noise Impact on ADSL2+ Systems

This thesis presents a methodology for performance evaluation of broadband access networks. The performance evaluation of networks is a way to identify and analyze how certain features, such as different traffic types or forms of use, can influence the behavior of the network in focus. This way, we can predict how the network will behave in future situations. The methodology is composed of two approaches: an approach based on measurements and the other based on modeling using Markov processes. The networks analyzed cover the two basic types of access architecture: ADSL2+ (asymmetric digital subscriber line 2+) networks, which are wired networks that use twisted pair cables; FBWN (fixed broadband wireless network) networks, which are wireless networks based on IEEE 802.16 standard. The measurement approach is focused on network behaves against three situations: transmission of a generic traffic, impact of non-stationary noise in the system, and using network for the transmission of real-time multimedia traffic. The modeling approach, in its turn, is based on predicting the behavior of the network using mathematical models based on Markov processes. The results presented indicate the feasibility of applying this methodology as form of performance evaluation. The results also make possible the extension of this methodology to other types of broadband access networks such as fiber optic networks, microwave links, and VDSL/VDSL2 (Very-high-data-rate DSL)

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Aspectos de avaliação de desempenho em redes ponto a ponto e ponto multiponto baseados em modelagem Markoviana e medições

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UNIVERSIDADE FEDERAL DO PARÁ INSTITUTO DE TECNOLOGIA PROGRAMA DE PÓS-GRADUAÇÃO EM ENGENHARIA ELÉTRICA Estudo de viabilidade econômica para implantação de redes de acesso banda larga em cenários amazônicos: um estudo de caso baseado no custo do bit aplicado ao programa NAVEGAPARÁ.

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)

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Dário Russillo

Papers

Impact of non-stationary noise on xDSL systems: an experimental analysis