Navegando por Assunto "G.fast"

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Acesso aberto (Open Access)
A Comparison between RS+TCM and LDPC FEC schemes for the G.fast standard
(Universidade Federal do Pará, 2016-02-01) TAKEDA, Marcos Yuichi; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
The need for increasing internet connection speeds motivated the creation of a new standard, G.fast, for digital subscriber lines (DSL), in order to provide fiber-like performance using short twisted pair copper wires. This dissertation focuses in the two former candidate codes for the forward error correction (FEC) scheme, namely Reed-Solomon (RS) with trellis-coded modulation (TCM), from previous DSL standards, and low density parity check (LDPC) codes, from the G.hn standard for home networking. The main objective is to compare both schemes, in order to evaluate which of them performs better, considering metrics such as error correction performance and computational cost. Even though the selected code for G.fast was RS with TCM, it is believed that this choice was biased, as a more recent iterative code like LDPC is known to have a better error correction performance.
Acesso aberto (Open Access)
Modelos paramétricos simples e causais para cabos de cobre apropriados para caracterização de enlaces em sistemas G.fast
(Universidade Federal do Pará, 2014-12-12) NUNES, Diogo Lobato Acatauassú; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
The G.fast is a new standard from the International Telecommunication Union that targets 1 Gb/s over short copper loops, using frequencies up to 212 MHz. This new technology requires accurate parametric cable models for simulation, design and performance evaluation tests. Most existing copper cable models were designed for the VDSL spectra - i.e., frequencies up to 30 MHz - and adopt assumptions that are violated when the frequency range is extended to G.fast frequencies. This thesis presents new simple and causal cable models that are able to accurately characterize copper loops composed by single or multiple segments, in both frequency and time domains. Results using G.fast topologies show that, besides being accurate, the new models are attractive due to their low computational cost and closed-form expressions for fitting their parameters to measurement data.
Acesso aberto (Open Access)
Simulação e avaliação das tecnologias LTE e DSL como backhaul utilizando software OPNET
(Universidade Federal do Pará, 2013-12-20) LINS, Silvia Cristina Feijó; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
The increasing demand for capacity has been driving the wireless communication standards to provide support to the coexistence of macro and small cells. The backhaul, which is the link between the radio access network and the backbone, is of particular interest due to the many involved technical challenges on keeping up with the user demand for bandwidth. Line-of-sight microwave radio and optical fiber are the preferred choices and widely adopted for the mobile backhaul (MBH) of macrocells. However, in many situations of practical interest, both options are not feasible due to cost and logistics. This work evaluates the backhaul of small cells, focusing on the adoption of copper pairs. Opnet was also used to evaluate copper MBH requirements in specific scenarios taking into consideration QoS provisioning. Assuming traffic demands for LTE and LTE-Advanced, VDSL2 and G.fast technologies are evaluated and the results show that even with a heavy load of video, these technologies can accommodate the small cell MBH traffic. VDSL2 is capable of delivering the required data rates for LTE small cell scenarios but not if considered LTE-Advanced traffic. Otherwise, if considered G.fast data rates, backhaul traffic for LTE-Advanced small cells can still be delivered by xDSL technology with QoS guaranteed. Also, this work enables the implementation of heterogeneous access networks scenarios considering LTE NLOS out-of-band backhaul. A solution of LTE backhaul implementation in OPNET is proposed and simulations are performed to validate such solution as a QoS-aware LTE Backhaul for WiFi and LTE radio access technologies.
Acesso aberto (Open Access)
Techniques of downstream rate balancing for vectored digital subscriber line systems: case study of the ITU G.9700 standard
(Universidade Federal do Pará, 2015-03-10) COUTINHO FILHO, Claudio de Castro; KLAUTAU JÚNIOR, Aldebaro Barreto da Rocha; http://lattes.cnpq.br/1596629769697284
As the DSL (Digital Subscriber Line) technology reaches its physical bandwidth limit and the Fiber-to-the-Home (FTTH) model becomes a potential substitute, new techniques and standards are developed to cope with the requirements from the Internet access industry. In this context, the newly agreed G.9700 (G.fast) standard, from the International Telecommunication Union (ITU), brings to the copper plant a renewal of its lifespan with the use of techniques such as Vectoring. Although Vectoring is a powerful tool for DSL to become a competitive technology for optical fiber, it must deal with the problem that subscribers still may get differing rates at their CPEs (Customer Premises Equipment), caused mainly by physical aspects of the channel. With that in mind, this work proposes methods of balancing the achievable rates delivered to user lines at Downstream. This is done by using different column sortings of the channel matrix, in scenarios that utilize the Tomlinson-Harashima Precoder (THP) up to 200 MHz. Simulations using each rate balancing method on six measured cables are made in order to show each method’s progress. These simulations are extended to the Near-Far Scenario, which tries to resemble the situations where some lines have greater length than others, that is, differing distances between the CPE and the DSLAM (Digital Subscriber Line Access Multiplexer). The proposed methods yielded promising balancing result, with reductions of up to 95.79% of the standard deviation for the Swisscom I51 cable, when comparing results of a genetic algorithm method with those of the THP.