IoT Protocols for Low-power Massive IoT: A Communication Perspective Martin Stusek 1 , Krystof Zeman 1 , Pavel Masek 1 , Jindriska Sedova 2 , and Jiri Hosek 1 1 Department of Telecommunications, Brno University of Technology, Brno, Czech Republic 2 Faculty of Economics and Administration, Masaryk University, Brno, Czech Republic Contact author’s e-mail: xstuse01@vutbr.cz Abstract—The constantly growing number of resource-limited MTC (Machine-Type Communication) devices is challenging both the telecommunication operators as well as industrial companies to efficiently design communication technologies, protocols, and end-devices for data transmissions in the upcoming 5G and beyond wireless communication networks. As the communication technologies for mMTC (massive Machine Type Communica- tions) / massive IoT (Internet of Things) attracted significant attention over the past years due to the extended communication range and improved lifetime of battery-operated devices, the debate turned from the communication parameters of avail- able Low-Power Wide-Area (LPWA) technologies towards the implementation issues related to efficient data transmissions with respect to certain level of Quality of Service (QoS). In this regard, this paper aims to analyze already introduced communication protocols (i.e., TCP, UDP, CoAP (Constrained Application Protocol), and MQTT (Message Queuing Telemetry Transport)) possible to use for data transmission in massive IoT scenarios. Along with the highlights of the protocols in question, a practical implementation is done using the emerging cellular IoT standard, namely, NB-IoT (Narrowband IoT). Out of the obtained data, the focus is primarily given to the side-by-side comparison of protocols’ overheads and the subsequent data usage as the amount of transmitted data is deriving the monthly fees. Index Terms—IoT, massive MTC, TCP, UDP, CoAP, MQTT, NB-IoT, communication overheads. I. I NTRODUCTION Over the past years, the telecommunication companies shared their predictions about a number of industrially con- nected devices e.g., Smart Grids as well as devices targeted for Smart Homes and Smart Cities. The evolving of fifth generation (5G) mobile networks is becoming closer to the market as a major driver of the sunrise of Internet of Things (IoT) applications [1]. From the definition of next-generation communication systems, it is evident the ubiquitous connec- tivity is the foundation for future massive IoT communication scenarios [2]. As various IoT requirements resulted in diverse network designs and principles, today, there is a myriad of communication technologies and standards which can be merged into a heterogeneous communication networks. From the customer viewpoint, the whole communication system can be abstracted and called as “network as a service” i.e., based on the customers’ decision, the communication technology which suits the best for the selected scenario is chosen. For the mMTC (massive Machine Type Communications) which is the scope of this paper, so called LPWA (Low- Power Wide-Area) technologies come into play as a part of heterogeneous system. LPWA technologies are by purpose characterized by low energy consumption, long battery life, extended communication coverage, and support for massive numbers of end devices [3], [4]. As the mMTC represents over 60 % of the IoT market, the data transmissions utilizing the LPWA technologies are gaining attention from both the industrial sector and researcher community [5]. The most recent LPWA technologies available to use these days i.e., NB-IoT (Narrowband-IoT), LTE Cat-M1, LoRaWAN, and Sigfox do significantly differ in case of communication capabilities, see the TableI. Following the need for the first field deployments (mostly related to remote metering in Smart Grid infrastructure), telecommunication operators experiment with the deployment of a range of LPWA technologies and standards [6]. The results from the field testing lead us to the point where the market momentum will switch from the first-to-market license-exempt LPWA standards e.g., LoRaWAN and Sigfox to the emerging licensed LPWA technologies i.e., 3GPP NB-IoT or LTE Cat-M1, which are envisioned to have a significant share of the LPWA market by 2020 [7]. TABLE I KEY PARAMETERS AND CHARACTERISTICS OF LPWA TECHNOLOGIES. LoRaWAN Sigfox NB-IoT LTE Cat-M1 Coverage (MCL) 157 dB 162 dB 164 dB 155 dB Technology Proprietary Proprietary Open LTE Open LTE Spectrum Unlicensed Unlicensed Licensed (LTE/any) Licensed (LTE/any) Duty cycle limit Yes Yes No No Output power restrictions Yes (14 dBm = 25 mW) Yes (14 dBm = 25 mW) No (23 dBm = 200 mW) No (23 dBm = 200 mW) Downlink data rate 0.3-50 kbps < 1 kbps 0.5-27.2 kbps < 300 kbps Uplink data rate 0.3-50 kbps < 1 kbps 0.3-32.25 kbps < 375 kbps Max. message size UL 243 B 12 B 1280 B 1280 B Max. message size DL 243 B 8B 1280 B 1280 B Battery life / Current consumption 8+ years <2 uA 10+ years <2 uA 10+ years <3 uA 10+ years <8 uA Module cost <$ 10 <$ 10 $ 10 (2019) <$ 25 (2019) Security Medium (AES-128) Low (AES-128) Very high (LTE Security) Very high (LTE Security) 2019 11th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT) 978-1-7281-5764-1/19/$31.00 ©2019 IEEE