# The Role of Smart Meters in Enabling Real-Time Energy Services for Households: The Italian Case
## 6 Communications Technologies for Real-Time Home Services
### Wireless Technologies  
Several wireless solutions specifically tailored for Smart Cities and Smart Grid applications have recently been envisioned. Such solutions can be broadly categorized into three groups [50]: Cellular Mobile Networks, IoT Dedicated Networks, and Multi-Tier IoT Networks. Cellular Mobile Networks are constituted by a front-end Radio Access Network (RAN) operating over a licensed spectrum and a backhand Core Network (CN) managing access and mobility. They are mainly designed to convey human-to-human or human-to-machine traffic and are especially suited for applications requiring high coverage and intensive data rates, with high mobility. Since cellular mobile networks operate on licensed frequencies, they provide high guarantees in terms of interference level and quality of service, even in case of massive numbers of transmitting devices. However, several legacy cellular technologies have recently evolved to support machine-to-machine (M2M) communications, such as smart metering, which is typically characterized by periodic and intermittent transmission of small amounts of data. Among those, we focus on _Extended Coverage GSM_ (EC-GSM), _LTE Machine-to-machine_ (LTE-M) and _Narrow Band IoT_ (NB-IoT). * EC-GSM [51] exploits the existing GSM/GPRS infrastructure and simply relies on a software update that strengthens the coverage by 20 dB w.r.t. the standard GPRS operating at 900 MHzand supporting communications for up to 50 thousand devices per cell. Power efficiency has also been improved, with the aim of increasing the battery lifetime up to 10 years. * _LTE-M_[52; 53], like EC-GSM, relies on the existing LTE infrastructure and only requires a software update of the base stations. After the standard Release 12 for M2M communications, which proposed Category 0 devices with reduced cost and complexity and increased battery duration w.r.t. the Category 1 devices discussed in Release 8, the latest Release 13 introduces further improvements such as the definition of narrowband channels with 1.4 MHz and 200 kHz bandwidth, thus allowing the use of less expensive and more energy-efficient hardware, which increases the link budget up to 100 dBm. * _NB-IoT_[54] adopts a clean-slate approach aimed at re-farming the GSM spectrum to support a new narrowband air interface compatible with GSM 200 kHz-wide channels: every downlink channel is partitioned into 48 narrowband sub channels of 3.75 kHz width, whereas the uplink is divided into 36 sub-channels of 5 kHz width. The reference spectrum bands include the GSM licensed spectrum and the guard bands of the LTE in order to support three different deployment approaches: (i) standalone GSM carrier; (ii) carrier placed in the LTE guardband portion (normally not used for data transmission) adjacent to an LTE carrier; and (iii) inband LTE carrier. NB-IoT is specifically tailored for massive smart metering applications, since it supports transmission from deep indoor devices (located e.g., in the household basement) thanks to the achieved link budget target of 164 dB. It supports the usage of an embedded Subscriber Identity Module (e-SIM), which enables remote configuration of the user profile, supports interoperability, and allows the user to possibly change operator without the substitution of the physical device. Moreover, the authentication and encryption capabilities of the e-SIM guarantee secure data transmission over public networks. The main characteristics of the three abovementioned technologies are reported in Table 4.  
_IoT Dedicated Networks_ such as wM-Bus, LoRa, and SIGFOX are dedicated point-to-multipoint architectures serving exclusively traffic originated from/destined to machine field devices. Their front-end operates over unlicensed spectrum and adopts a simplified backend infrastructure, thus ensuring lower deployment and operational costs w.r.t. traditional cellular mobile networks. This ensures high scalability even with a limited number of concentrator nodes (i.e., gateways that convey the machine field traffic to the core IP network).