1 Low Power Wide Area Networks: An Overview Usman Raza, Parag Kulkarni, and Mahesh Sooriyabandara Abstract—Low Power Wide Area (LPWA) networks are at- novel communication technologies are all positive indicators, tracting a lot of attention primarily because of their ability to supporting the forecasted trends. offer affordable connectivity to the low-power devices distributed Low Power Wide Area (LPWA) networks represent a novel over very large geographical areas. In realizing the vision of the Internet of Things (IoT), LPWA technologies complement and communication paradigm, which will complement traditional sometimes supersede the conventional cellular and short range cellular and short range wireless technologies in addressing wireless technologies in performance for various emerging smart diverse requirements of IoT applications. LPWA technologies city and machine-to-machine (M2M) applications. This review offer unique sets of features including wide-area connectivity paper presents the design goals and the techniques, which differ- for low power and low data rate devices, not provided by ent LPWA technologies exploit to offer wide-area coverage to low- power devices at the expense of low data rates. We survey several legacy wireless technologies. Their market is expected to be emerging LPWA technologies and the standardization activities huge. Approximately one fourth of overall 30 billion IoT/M2M carried out by different standards development organizations devices are to be connected to the Internet using LPWA (e.g., IEEE, IETF, 3GPP, ETSI) as well as the industrial consortia networks using either proprietary or cellular technologies [3]. built around individual LPWA technologies (e.g., LORa™ Al- Figure 1 highlights variety of applications across several busi- liance, WEIGHTLESS-SIG, and DASH7 Alliance). We further note that LPWA technologies adopt similar approaches, thus sharing ness sectors that can exploit LPWA technologies to connect similar limitations and challenges. This paper expands on these their end devices. These business sectors include but not research challenges and identifies potential directions to address limited to smart city, personal IoT applications, smart grid, them. While the proprietary LPWA technologies are already smart metering, logistics, industrial monitoring, agriculture, hitting the market with large nationwide roll-outs, this paper etc. encourages an active engagement of the research community in solving problems that will shape the connectivity of tens of billions LPWA networks are unique because they make different of devices in the next decade. tradeoffs than the traditional technologies prevalent in IoT landscape such as short-range wireless networks e.g., Zig- Index Terms—Internet of Things, IoT, Low Power Wide Area, LPWA, LPWAN, Machine-to-Machine Communication, Cellular Bee, Bluetooth, Z-Wave, legacy wireless local area networks (WLANs) e.g., Wi-Fi, and cellular networks e.g. Global Sys- tem for Mobile Communications (GSM), Long-Term Evolu- tion (LTE) etc. The legacy non-cellular wireless technologies I. INTRODUCTION are not ideal to connect low power devices distributed over HE Internet of Things (IoT) promises to revolutionize the large geographical areas. The range of these technologies T way we live and work. It could help us in overcoming is limited to a few hundred meters at best. The devices, the top global challenges due to population explosion, energy therefore, cannot be arbitrarily deployed or moved anywhere, crisis, resource depletion, and environmental pollution. To a requirement for many applications for smart city, logistics realize this vision, things need to sense their environment, and personal health [4]. The range of these technologies is share this information among themselves as well as with extended using a dense deployment of devices and gateways humans to enable intelligent decision making for positively connected using multihop mesh networking. Large deploy- affecting our entire ecosystem. Due to this promise, an interest ments are thus prohibitively expensive. Legacy WLANs, on in IoT is phenomenal. Multiple independent studies have the other hand, are characterized by shorter coverage areas and arXiv:1606.07360v2 [cs.NI] 11 Jan 2017 forecasted a rampant growth in volume and revenue of IoT higher power consumption for machine-type communication and Machine-to-Machine (M2M) industry in the next ten (MTC). years. Number of connected M2M devices and consumer A wide area coverage is provided by cellular networks, a electronics will surpass the number of human subscribers using reason of a wide adoption of second generation (2G) and third mobile phones, personal computers, laptops and tablets by generation (3G) technologies for M2M communication. How- 2020 [1]. Moving forward, by 2024, the overall IoT industry is ever, an impending decommissioning of these technologies [5], expected to generate a revenue of 4.3 trillion dollars [2] across as announced by some mobile network operators (MNOs), will different sectors such as device manufacturing, connectivity, broaden the technology gap in connecting low-power devices. and other value added services. Recent improvements in cheap In general, traditional cellular technologies do not achieve sensor and actuation technologies along with an emergence of energy efficiency high enough to offer ten years of battery lifetime. The complexity and cost of cellular devices is high All authors are with Toshiba Research Europe Limited, UK, Email: fusman.raza, parag.kulkarni, [email protected]. due to their ability to deal with complex waveforms, optimized ©2016 IEEE. Personal use of this material is permitted. Permission from for voice, high speed data services, and text. For low-power IEEE must be obtained for all other uses, in any current or future media, MTC, there is a clear need to strip complexity to reduce cost. including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers Efforts in this direction are underway for cellular networks by or lists, or reuse of any copyrighted component of this work in other works. the Third Generation Partnership Project and are covered as 2 Fig. 1. Applications of LPWA technologies across different sectors part of the discussion in Section IV. metering, home automation, wearable electronics, logistics, With a phenomenal range of a few to tens of kilometers [6] environmental monitoring etc. (see Figure 1) that exchange and battery life of ten years and beyond, LPWA technologies small amount of data and that also infrequently. Therefore, are promising for the Internet of low-power, low-cost, and low- appeal of LPWA technologies, although limited by its low data throughput things. A very long range of LPWA technologies rate, is still broad. This is the reason why LPWA technologies enables devices to spread and move over large geographical generated so much interest after the proprietary technologies areas. IoT and M2M devices connected by LPWA technolo- such as SIGFOX [9] and LORa [10] hit the market. gies can be turned on anywhere and anytime to sense and At this moment, there are several competing LPWA tech- interact with their environment instantly. It is worth clarifying nologies, each employing various techniques to achieve long that LPWA technologies achieve long range and low power range, low power operation, and high scalability. Section II operation at the expense of low data rate (typically in orders presents these design goals and describes how a combina- of tens of kilobits per seconds) and higher latency (typically in tion of different novel techniques actually achieves them. orders of seconds or minutes). Therefore it is clear that LPWA Section III then discusses several early proprietary LPWA technologies are not meant to address each and every IoT use technologies and their technical features, highlighting the case and caters to a niche area in IoT landscape. Specifically, need for standardization to flourish IoT ecosystem. To this LPWA technologies are considered for those use cases that effect, several well-known standard developing organizations are delay tolerant, do not need high data rates, and typically (SDOs) such as European Telecommunications Standard In- require low power consumption and low cost, the latter being stitute (ETSI) [11], Third Generation Partnership Project an important aspect. Such MTC application are categorized as (3GPP) [12], Institute of Electrical and Electronics Engineers Massive MTC [7] in contrast to Critical MTC [7] applications (IEEE) [13], and Internet Engineering Task Force (IETF) [14] that require ultra-low latency and ultra high reliability. The are working towards the open standards for LPWA technolo- latter are definitely out of the remit of LPWA technologies gies. Further, multiple industrial alliances are built around because their stringent performance requirements such as up individual LPWA technologies to promote new standards. to five nines (99.999%) reliability and up to 1-10 ms latency LORa™ Alliance [15], WEIGHTLESS-SIG [16] and DASH7 cannot be guaranteed with a low cost and low power solution. Alliance [17] are a few examples of such special interest While LPWA technologies, for this reason, are not suitable groups (SIGs). Section IV covers the standardization efforts for many industrial IoT, vehicle to vehicle (V2V), and vehicle led by all these SDOs and SIGs. to infrastructure (V2I) applications [8],