In an effort to promote open standards for Smart Grid environment and to meet the specific regional and national regulations in a global Smart Grid deployment environment in a scalable and cost-effective way, it is very important to consider the work of the IEEE 802.15.4g Task Group, also known as the Smart Utility Networks (SUN) Task Group to review the IEEE 802.15.4-2006 standards, proposing amendments principally for outdoor low data rate, wireless, smart metering utility networks.

The selection of last mile technologies clearly impacts products and solutions that must comply with local standards. One of the recognized benefits of the adoption of the TCP/IP architecture for Smart Grid is its ability to run over any kind of physical and data link layers by adapting to all wired and wireless communications technologies. However, the physical and data link layer standardization is outside the scope of the Internet Engineering Task Force (IETF). IETF only defines how TCP/IP runs on top of the MAC and PHY layers standardized by the Institute of Electrical and Electronics Engineers (IEEE) or other standards bodies.

IEEE 802.15.4g - currently under ballot, meaning the draft of the full standard is stable and the IEEE imperative principle of consensus has to be found between voters and all comments addressed before 15.4g can be officially published - adds new PHY support for Smart Utility Networks (SUN) to IEEE 802.15.4-2011 that will help in developing and deploying standards-based RF-Mesh solutions around the world. In addition to the new PHY, the amendment also defines MAC modifications (may also require 15.4e add-on features) needed to support their implementation.

The SUN PHY supports multiple data rates in bands ranging from 450MHz to 2450 MHz and working in one of these 3 modes.

• Orthogonal frequency division multiplexing (MR-OFDM) PHY - provides higher data rates at higher spectral efficiency
• Multi-rate and multi-regional offset quadrature phase-shift keying (MR-O-QPSK) PHY - shares the characteristics of the IEEE 802.15.4-2006 O-QPSK PHY, making multi-mode systems more cost effective and easier to design.
• Multi-rate and multi-regional frequency shift keying (MR-FSK) PHY - good transmit power efficiency due to the constant envelope of the transmit signal.

IEEE 802.15.4g addresses regional regulations - North America, Europe, Japan, Korea and China - by adding support for new frequencies including sub-GHz frequency bands. The IEEE 802.15.4 radio can now operate in one of the dedicated use or unlicensed bands. The following table summarizes the various operating frequencies.

IEEE 802.15.4g Frequency Allocations

Given that three PHYs are defined within the application space, it is possible that multiple, different SUN PHYs can be operating in the same location and within the same frequency band. In order to mitigate interference, a multi-PHY management (MPM) scheme is specified for SUN networks to enable inter-PHY coexistence.

With the publication of IEEE 802.15.4-2011 specifications, a new and open ecosystem for large volume of standards-based semiconductors, including management tools, protocol analyzers and diagnostics tools can appear, helping to lower the cost of scaling up Smart Grid deployments worldwide.
However, frequency bands in some region still needs to get harmonized for real success such as the on-going effort from the European Conference of Postal and Telecommunications Administrations (CEPT) to allocate new frequency bands (870-876MHz and 915-921MHz) in Europe