Petr Jares

Increasing the transmission capacity of digital subscriber lines

The digital subscriber lines with very high speed data rates combined together with passive optical networks are considered as a promising high-speed solution for modern metallic and hybrid access networks. To increase the transmission capacity in such case, it would be possible to implement an idea of using multiple pairs of local cables and group them together using an inverse multiplexing technique. This article first introduces the basic parameters of broadband measurements of phantom circuit created from pairs within one star-quad, together with the description of method for far-end crosstalk modeling. Based on these results, a practical experiment was performed using real metallic cable. The next part is focused on the simulation of digital subscriber line using phantom circuit together with and without crosstalk elimination technique using vector multi-tone modulation. The results and calculations of possible transmission capacity of phantom circuit are compared with measured results.

Optimal position of external node for very-high-bitrate digital subscriber line

This paper describes a specific variant of very-high-speed digital subscriber line (VDSL) for access network in the Czech Republic under the terms of frequency bands released by Telefonica O2 CR. The spectral profiles are characterized by alternating bands for upstream and downstream directions when using frequency duplex. Further discussion deals with achievable bitrates under different conditions and the expected profiles that should be offered to subscribers. The resulting bitrates are calculated with respect to the length of the line with a copper core diameter of 0.4 mm and the number of disturbance sources for upstream and downstream directions. The analysis was performed using real distribution of subscriber line lengths in the Czech Republic. Higher penetration can be achieved with optical-metallic hybrid network. The optimal position of external node for very-high-speed digital subscriber line is deduced and proposed.

Modeling of the multi-carrier modulation benefits for data transmission

More efficient data transmission is an important element for increasing an overall transmission performance in broadband access networks. Advanced access network infrastructure can have a dual nature. First, it may entirely consist of optical elements, which mean that the network has a nature of a passive optical access network. In addition, in a network topology there can be found elements that work with signals in an electrical form. Then, the network has a character of a hybrid access network. Modulation principles for user signals transmission in the second part of the hybrid access network belong to the group called multi-carrier modulation. This paper is focused on finding a more suitable simulation principles used when calculating the benefits of multi-carrier modulation used for user data transmission. Consecutive chapters describe a simplified method of modeling the user data transmission performance with regard to the real parameters of the transmission environment. Concrete results for typical situations are calculated and discussed.

Modeling of Middle-range Metallic Lines for Ethernet with VDMT

The optic fibers are gradually replacing the metallic lines and data bit rates are increased from tens Mb/s to hundreds Mb/s and Gb/s in LANs and in the first miles of digital subscriber lines. However information capacity of metallic lines can be increased, if the systems will use VDSL2 physical layer with vectored DMT modulation and line bounding concept. The methods for partial crosstalk cancellation are discussed and simulation results are presented for middle-range used especially for connection of Ethernet network nodes.

Reliability study of selected communication systems for energy grid

The concept of Smart Grid technology, which promises highly efficient and dynamic energy systems, has to be backed by suitable information and communication system. The availability and reliability must be important features of the power energy grid. These are features which must satisfy too the communication network built to support it. The paper analyses theoretical basis and presents selected practical experience with circuit oriented and packet oriented network technologies to enable build of the fault tolerant systems. This paper describes availability model of the communication network with different network technology based on our own experiences and experiments. The common topology with path protection on optical fibres is considered.