## 3 Standards for Cyber-Physical Energy Systems (CPES) Wireless Networking
### Low Power Wide Area Networks (LPWANs) as a Service  
For wireless networking, CPES can use several LPWAN providers that offer NaaS nationwide in one or more countries. The best-known competing technologies in Europe are LoRaWAN [32], SigFox [33], NB-IoT (Release 13) [19], and LTE-M [34], which differ in technical parameters and marketing concepts. The SaaN Sigfox of the French company Sigfox S.A. is available in 53 countries (December 2018), but without seamless coverage. Sensors with Sigfox modules are available for applications in smart homes, smart cities, agriculture, environment, health and assisted living, industry, and fleet management. The network works in the ISM band at 868 MHz and supports half-duplex communication, which can only be invoked by the node. For modulation, the differential binary phase shift keying (DBPSK) method is used for the uplink and the gaussian frequency shift keying (GFSK) method for the downlink [35]. To further reduce energy consumption, Sigfox can also be used in an operating mode with a unidirectional uplink so the nodes act exclusively as transmitters. The elimination of the receiver also reduces hardware costs. The payload is 12 bytes small. Technical parameters, restrictions, and rules for competing access are country-specific. In Europe, up to 140 messages can be uplinked daily at a rate of 100 bit/s and the network usage ratio must not exceed 1%. This amount of data restricts the usability of Sigfox to sensors with transmission of single values at an interval of not less than five minutes. The transmission range of a base station can be up to 50 km in flat rural areas, but only 3 to 10 km in an urban environment [35]. In the United States, Ingenu [36] offers another commercial NaaS of the same name for IoT applications and smart grids operating in the 2.4 GHz band with random phase multiple access (RPMA) modulation. As a part of the Long Term Evolution (LTE) [37] standard family, Narrowband IoT (NB-IoT) (also: LTE Cat-NB1) [19], and LTE for Machines (LTE-M) (also: LTE Cat-M1 or eMTC) [34] are standards for cellular LPWANs maintained by the Third-Generation Partnership Project (3 GPP). Both are based on GSM/LTE networks and operate in licensed frequency bands. Providers are large mobile operators who can expand their existing LTE radio systems with extensions for IoT services. Using the existing  
LTE system design for media access, channel coding, interleaving, rate matching, and more gives providers a significant time and cost advantage. In LTE-M, a software update of the existing LTE systems is sufficient [34], while Narrowband IoT (NB-IoT) requires a hardware upgrade of the base stations to perform the required modulation. Unlike LTE-M, which only works for LTE in-band, NB-IoT can be operated in three different modes: standalone as a carrier in the GMS band, LTE in-band, or within an LTE guard band. To fulfill the additional need of 20 dB maximum coupling loss (MCL), NB-IoT uses techniques to increase coverage, such as power boosting in the downlink or subframe repetition in the uplink and downlink [38]. Both standards use the single carrier frequency division multiplex access (SC-FDMA) method for uplink modulation and the orthogonal frequency-division multiple access (OFDMA)method for downlink modulation. With its 180 kHz wide channels, NB-IoT achieves a data rate in the uplink of about 200-250 kbit/s and can handle up to 50,000 devices per cell. With LTE-M, an upload rate of up to 1 MBit/s is possible, and the capacity of a cell is about 10,000 devices. Compared to regular LTE, 3 GPP has introduced some simplifications for NB-IoT: a single antenna is sufficient for receivers and transmission hardware just implements a half-duplex mode, resulting in a less complex hardware design and cheaper radio modules. LTE-M provides full duplex communication.