Multiplexers and Network Elements of DPLC Equipment
If DPLC equipment modems are the main part of the system and are responsible for how information will be transmitted through a HF path, then multiplexers are responsible for transmitting/receiving information signals between user interface modules and mod
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Multiplexers and Network Elements of DPLC Equipment
3.1 Multiplexers DPLC equipment includes a multiplexer with time division of signals and/or a network element. The multiplexer can be made as FPGA located on the CPU module board or as a separate module in the system chassis. Basic functions of a multiplexer are as follows: • Multiplexing incoming signals received from user voice frequency interfaces and data interfaces into a single aggregated digital signal transmitted to the modem • Demultiplexing digital signal received from the modem to transmit information to the user interfaces • Prioritization of user interface signals • Routing of user signals in transit connections at the aggregated signal level.
3.1.1 T ypical Schemes for Multiplexer Application in DPLC Equipment Let us consider typical schemes of using a multiplexer as a part of DPLC equipment. Figure 3.1 shows diagram using multiplexer built into the CPU module. In this case, the multiplexer is responsible for processing data signals received from the user interfaces, but it does not process speech signals. This scheme is widely used in DPLC equipment when part of the operating band is used for analog speech transmission, and the remaining part is used for the digital modem operation and data transmission. Multiplexer can use various data interfaces RS-232 and X.21, and it processes data coming from the network element. Various data collecting devices are connected to DPLC equipment via RS-232 interfaces, for example, data © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 A. G. Merkulov et al., High Voltage Digital Power Line Carrier Channels, https://doi.org/10.1007/978-3-030-58365-1_3
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3 Multiplexers and Network Elements of DPLC Equipment
Fig. 3.1 Multiplexer built-in in CPU module
from telecontrol system can be transmitted via IEC 60870-5-101 protocol. X.21 interface is used to connect various external multiplexers and IP routers. Detailed information about parameters of data interfaces can be found in [1]. Figure 3.2 shows diagram using multiplexer as a separate module. Speech signals are sent from voice modules to the multiplexer which compresses them using low bit rate speech codecs. In some industrial models of DPLC equipment, multiplexers have a framed two- megabit E1 interface for connecting PABX or external PDH multiplexers. In this case, multiplexer of DPLC equipment compresses digital voice signal transmitted from the external device in 64 kbps timeslots of the E1 stream. A transit interface which is used for transiting speech and data signals at the level of aggregated digital signal, rather than voice frequency interfaces or user data interfaces can also be implemented in the multiplexer. Network elements are used for connecting various network devices to DPLC equipment via Ethernet interface. Principles of network element operation will be discussed in the next section. As a rule, most DPLC systems use transparent Ethernet bridge which does not perform
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