Capacity analysis of G.fast systems via time-domain simulations

Abstract

The evolving broadband access systems using copper networks are currently deployed in a frequency band that goes up to 30 MHz, as specified in VDSL2. As hybrid fibercopper architectures become more important in the industry and academia, using shorter loop lengths (i.e. up to 250 meters) from the last distribution point to users enables adopting even higher frequencies to achieve very high data rates of 500 Mbps and beyond, as is the case with the G.fast standard under development by ITU-T. In this work, a time-domain simulator has been developed to evaluate G.fast system performance. System capacity is evaluated with different cyclic extension lengths and different reference loop topologies specified by ITU-T. The simulation results show that G.fast systems are robust to bridgetaps and capable of providing very high data rates for all simulated loop topologies to support next generation ultra high speed broadband services.

Accurate low complexity modeling of twisted pairs suitable for G.fast frequencies

“…Evidently, only minor differences in both Eqs (17), (18), and (19) can be observed. Therefore, in order to approximate Eqs (17) and (18), the expression of a propagation constant γ(f) in Eq.…”

“…(19), the inverse hyperbolic sine arguments in Eq. (17), (18) should contain terms slowly approaching a number one using appropriate frequency f fractions. With the respect to this conclusion and Eq.…”

“…As the modern transmission systems occupy higher and higher frequency bands of metallic cables and lines, it is necessary to develop adequate and accurate models to estimate their transmission channels at high frequencies [17]. The accurate modeling of the transmission line coefficients, especially its propagation constant γ( f), which consists of an attenuation constant α( f) and a phase constant β( f), is important mainly in practice, because it is required for various further estimations, such as the transmission performance modeling [18], crosstalk approximations (far-end crosstalk vectoring process in DSL) [19], signal propagation modeling, and so on. The estimation of line transmission characteristics can be performed by either modeling of its primary coefficients or the secondary line coefficients [20].…”

Performance Evaluation of MGfast Systems Over Coaxial Cables

“…In fact, in STDD MGfast systems, the cyclic prefix only has to counter the impulse response delay spread, whereas in full-duplex MGfast the cyclic prefix is used to counter the delay spread and a cyclic suffix is employed to counter the propagation delay in the cable [5], [6]. This paper adopts cyclic prefix configurations compatible with G.fast [4], which include an associated overhead to the system varying between 0 and 13% [3], [5], [31].…”

Modelling of Propagation Constant of Twisted Pairs and Its Temperature Dependence at G.fast Frequencies

“…The main innovations include vectoring of transmitted DMT symbols through Vectored DMT modulation (VDMT) [3], the time-division duplex (TDD) technique, the reverse power-feeding mechanism [5], etc. However, the successful implementation of all these features require accurate and quick estimation of elementary transmission characteristics and parameters of the transmission channel [7], [8].…”