Abstract：Based on the reflection principle of digital signal propagation theory, a mathematical model of G.fast channel is established when the impedance of digital subscriber line is not matched.The reflection coefficient is used to describe the line impedance mismatch and the channel data (direct channel, far-end crosstalk channel and near-end crosstalk channel) measured when line impedance matching are used in the model.When the terminal is disconnected, the channel data calculated by the model is consistent with the actually measured data, which proves the accurateness of the model.Since the reflection coefficient is used to describe the degree of impedance mismatch, the model can simulate the influence of the terminal equipment on the signal noise ratio of the communication system under different impedances.Therefore, we propose a maximum allowable variation range of the terminal impedance which provides some theoretical guidance for terminal manufacturer for designing terminal impedance.
李俏杰. G.fast数字用户线路阻抗不匹配信道模型研究[J]. 电子学报, 2020, 48(2): 403-406.
LI Qiao-jie. On the Impedance Mismatch Channel Model of G.fast Digital Subscriber Line. Acta Electronica Sinica, 2020, 48(2): 403-406.
[1] ITU-T G.9701-2014,Fast Access to Subscriber Terminals-Physical Layer Specification[S].
[2] GinisG,Cioffi J M.Vectored transmission for digital subscriber line systems[J].IEEE Journal on Selected Areas in Communications,2002,20(5):1085-1104.
[3] Alcatel-Lucent.Influence of an Impedance Change on a Leaving Line onto the Direct and Crosstalk Channels of the Active Lines[Z].ITU-T SG15 Contribution,2013-10-Q4-058.
[4] Futurewei Technologies.G.fast:SNR Drop and FEXT Channel Variations Due to Change of Alien Termination[Z].ITU-T SG15 Contribution,2013-10-Q4-046.
[5] Lafata P.Simple Attenuation models of metallic cables suitable for G.fast frequencies[J].Information and Communication Technologies and Services,2015,13(2):147-155.
[6] Digo A,Stenfan H,Lu C G,Miguel B.Simple and causal copper cable model suitable for G.fast frequencies[J].IEEE Transactions on Communications,2014,62(11):4040-4051.
[7] Medeiros E,Magesacher T,Odling P,Wei D,Wang X,Li Q J,Eriksson P,Lu C G,Boschma J.Modeling alien-line impedance mismatch in wideband vectored wireline systems[J].IEEE Communications Letters,2014,18(9):1527-1530.
[8] Diogo A,Stenfan H,Lu C G,Miguel B,Aldebaro K,Börjesson P O.Simple and causal twisted-pair channel models for G.fast systems[A].2013 IEEE Global Communications Conference[C].Atlanta,GA,USA:GLOBECOM,2013.2834-2839.
2020, Vol. 48 
