# Telecommunication Technologies for Smart Grid Projects with Focus on Smart Metering Applications
## 2 Technologies for LV Smart Metering--Background Information  
### Wired Technologies  
#### 2.1.1 Narrowband PLC (NB-PLC)  
Narrowband PLC (NB-PLC) technology implies that data is transmitted through a narrow frequency band at a low bit rate. NB-PLC technologies aim at offering indoor (home automation) and outdoor (smart grid) command and control services. One application of NB-PLC is the control and telemetry of electrical equipment such as meters, switches and heaters. NB-PLC is usually applied for the telecommunication link between the smart meter and data concentrator. [7; 8]. In Europe the NB-PLC band goes roughly from 3 kHz to 150 kHz and is further divided into four sub-bands. More specifically, the CENELEC A band (3-95 kHz) is mostly used by power utilities for applications like monitoring or controlling the low-voltage and distribution network. CENELEC B-band (95-125 kHz) can be used for any kind of applications, the C-band (125-140 kHz) for home networking systems while the CENELEC D-band (140-148.5 kHz) is specified for alarm-and security systems. In Japan, ARIB has specified the 10-450 kHz frequency band for PLC applications, whereas in USA FCC has defined the 10-490 kHz frequency band for this purpose [9]. Two Orthogonal Frequency Division Multiplexing (OFDM)-based NB-PLC solutions that can offer high data rates, and which have been introduced to the market prior to high data rate standards, are namely PRIME and G3-PLC: Both PRIME [10] and G3-PLC [11] use the (OFDM) transmission method and the DBPSK/DQPSK modulation technique. The difference is that in PRIME the DPSK concept is used in the frequency domain, whereas in G3-PLC in the time domain. Another difference lies in the encoding procedure of the two specifications [12]. Some of the available standards for NB-PLC are as follows:  
* IEEE 1901.2--It is a high data rate standard and it defines NB-PLC both via alternating and direct current. Smart Grid applications are included. Other PLC technologies operating below 500 kHz can also coexist. It is noteworthy that the standard includes three physical and MAC layer specifications, the G3-PLC (10-500 kHz), the G3-PLC for CENELEC A and the PRIME for CENELEC A [8]. * ITU-T G.hnem--This standard can be used for a variety of Smart Grid applications such as smart metering, demand response, _etc._ It is a high data rate standard and uses the OFDM technology that refers to in-home energy management and home automation. It should be noted, that in this standard, the recommendations ITU-T G.9902, ITU-T G.9903, ITU-T G.9904 are included, which contain the physical and data link layer specifications for ITU-T G.9902, G3-PLC and PRIME NB-PLC OFDM transceivers respectively [13]. * IEC 61334--Part 5 of this standard defines NB-PLC systems, whereas part 5-1 defines in particular an S-FSK scheme (G1 specification). Single carrier technologies are used, meaning that the data rate is low. The data concentrator in such a system acts as a \"local relay\" for a management centre [14]. * IEC 62056 is a set of standards for electricity metering data exchange and they are the standard versions of the DLMS/COSEM specification. Part 21 defines how data transmission of electricity meters takes place, while mode E indicates that the use of DLMS/COSEM through High-Level Data Link Control (HDLC) is supported. Single carrier techniques are used also in this case, thus leading to low data rates transmitted [14]. * ISO/IEC 14908-1 (Lonworks)--Lonworks technology has been created by Echelon. For electric utility applications, the CENELEC A band is used. CENELEC C band is used for in-home applications. The resulting data rate is kept at low levels (few kbps) [8]. To complete the picture, there is another technology that is also popular for smart meter applications when it comes to the data transmission from the smart meter to the data concentrator, namely Meters and More. According to it the physical layer is designed by using the Binary Phase-Shift Keying (BPSK) modulation, while the LLC layer is based on IEC 61334-4-3.