## 3 Review of PLC Systems
### Evolution of PLC Standardization  
#### 3.2.1 UNB and NB PLC Standardization  
Standardization has not always been a priority in PLC systems. PLC priority has been historically to create systems that managed to work on real field conditions. Eventually, some parts of the systems were somehow promoted to standards, due to the adoption or the influence of the technology promoters. A good example of this statement were ripple control systems, that having their origin in the 1950s [51], were only standardized through [52] for receiver type testing. NB PLC systems have also been subject to standardization efforts. In 1991, CENELEC issued the European Norm EN 50065-1+A1:2010 [53] and although some of the existing PLC proprietary systems remained proprietary, some others followed different standardization paths. LonWorks [54] (ANSI/EIA/Consumer Electronics Association (CEA) 709 and ISO/IEC 14908-1 [55]) is the result of the system created by Echelon [56] and supported by the EIA and the CEA, initially for industrial and building automation. The ANSI standard has four parts, one for network control protocol (EIA 709.1-B, 2002), and three more for different physical media (EIA 709.2 is the one for PLC). Konnex (KNX, EN 50090), promoted by Konnex Association [57], was initially created for home and building automation, as an evolution to harmonize three other protocols (namely, BatiBUS Club International (BCI), European Installation Bus Association (EIBA), and European Home Systems Association (EHSA)). Konnex version in EN 50090 ([58]), includes several communications media options, PLC among them. The relevant examples in the IEC 61334-5 domain [59] are the International Standard IEC 61334-5-1 with a Spread-Frequency Shift Keying (SFSK) NB PLC system. IEC 61334-5-2 to IEC 61334-5-5 as Technical Specifications: IEC 61334-5-2 a FSK NB PLC system; IEC 61334-5-3 with a Direct Sequence Spread Spectrum Adaptive Wideband (SS-AW) NB PLC; IEC 61334-5-4 with a MCM with differential PSK, mainly for MV PLC; and IEC 61334-5-5 with Spread Spectrum Fast Frequency Hopping (SS-FFH) NB PLC system. A complementary standardization effort took place for NB PLC systems with the so-called (DLMS/COSEM) [36]. The DLMS/COSEM is the application level and objects language that many smart metering systems worldwide use. DLMS/COSEM has its origins in the car-manufacturing industry in the 1970s. In 1980 an initiative called Manufacturing Automation Protocol (MAP) started to design a network standard to interconnect different electronic devices and machines in manufacturing plants [60]. This effort produced a communications suite [61], that at the application layer defined a protocol known as Manufacturing Message Specification (MMS), standardized as [62,63]. MMS became a reference for utilities when the American Electric Power Research Institute (EPRI)focused its attention on it. In the first half of the nineties, some European utilities and manufacturers started working to adapt MMS to the electricity distribution grid [64], and this work resulted in a simplified version of the protocol, and then called Distribution Line Message Specification (DLMS). DLMS was standardized by IEC TC57 as [65, 66]. In 1996, the DLMS User Association was created, and inside the smart metering context, a whole new \"abstract object\" model (COSEM) was created based on the German Energy Data Identification System (EDIS, [67]). DLMS took the definitive name of \"Device Language Message Specification\", and together with COSEM addressed the overall market of utilities (not only electricity utilities), supporting non-PLC communication means. The evolution of this second generation [51] standard systems follows with the introduction of OFDM systems, being PRIME and G3 the first instances to appear [68]. As it was mentioned at the beginning of the chapter, and specifically true for PRIME, the efforts were initially focused on producing an industry supported systems, that should be demonstrated on the field, and that could eventually be standardized.