# IEEE 802.11 ah: A Technology to Face the IoT Challenge
## 1 Introduction  
In recent years, we have witnessed an exponential growth in the evolution and development of different communication technologies addressed to support the IoT. New applications require innovative connectivity solutions and new ways of sharing data among different devices and networks, thus creating a new concept of Internet. In the related literature, a collection of new terms have been coined in an attempt to clarify the new scenario of connected applications, the Internet of Everything (IoE) (cf. Figure 1) appears as a concept that contains both the IoT and the Internet of Humans (IoH), including the capability to share data between each other (IoT and IoH) or among themselves using machine to machine (M2M) or machine to human (M2H) communications. Following a similar approach, we could shape the IoT definition to include two different concepts: industrial IoT (iIoT) and consumer IoT (cIoT), exhibiting a new scenario that will dominate the world's communications in the near future, at least in terms of number of participating devices. The upcoming IoT applications are enablers of innovative concepts such as smart cities, smart/e-health, smart metering and smart things. Each of these applications has particular requirements, i.e., different data rates, low power consumption, low cost of implementation, large number of supported devices and the capacity to cover different distance ranges. As signified in [1], it is estimated that the number of devices connected to the IoT will reach 50 billion by 2020. This massive implementation of the IoT paradigm will bring changes to many aspects of our lives. The debate on which technology should lead this revolution has not been settled yet. Over the years there were multiple contenders, while Wi-Fi seemed to be observing from the bench. The legacy IEEE 802.11 standard was originally developed for indoor home and office scenarios with recognized worldwide success. Nowadays, IEEE 802.11 can be considered as a ubiquitous technology found in a wide range of consumer electronic devices and used in heterogeneous scenarios. However, up till now, IEEE 802.11 has not shown a significant presence in the IoT market, without any specification focused on IoT and its singularities. Taking into account the near future scenario for IoT communications, IEEE 802.11 Working Group (WG) aims to bridge the gap by introducing the new amendment called IEEE 802.11 ah [2]. Based on the IEEE 802.11 ah, the Wi-Fi Alliance has recently introduced the Wi-Fi HaLow program and expects to launch the certification process in 2018. Therefore, IEEE 802.11 ah is the first approximation of IEEE 802.11 WG that can enable IoT specific features within thousands of stations operating at Sub 1 GHz Industrial, Scientific and Medical (ISM) frequency band [3; 4; 5]. The amendment has been designed based on the following uses cases:  
* _Smart sensors and meters._ The goal of the new amendment is to enable IEEE 802.11 technology to cover IoT applications for indoor and outdoor spaces in urban, suburban and rural environments. * _Backhaul aggregation._ This is a scenario in which IEEE 802.11 ah routers/gateways would gather data from leaf devices (i.e., sensors) and forward information to servers, utilizing IEEE 802.11 ah links. This use case is attractive for long range communications. * _Extended range hotspot and cellular offloading._ Both high throughput and long transmission range make sub-1 GHz communications very attractive for extending hotspot range and for traffic offloading in mobile networks. Most recently, the IEEE 802.11 WG has triggered other future specifications to include the IoT use case. As of July 2015, the creation of a new Topic Interest Group (TIG) on Long-Range Low-Power (LRLP) operation for IoT was initiated [6], which aimed to bring some of the new IEEE 802.11 ah features to the 2.4 GHz band while keeping compatibility with mainstream IEEE 802.11 devices on that band.