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16 By Barry Manz Connectivity is one of the most frustrating aspects to tackle for designers of IoT networks. At the "edge" where sensors communicate with each other, there are multiple, mostly incompatible, competing standards. From the edge to the Internet and cloud there are only two: Wireless carriers and Low-Power Wide Area networks (LPWANs) in competition. LPWAN providers use more than one standard, and some are proprietary, while the cellular industry roadmap focuses on streamlining and enhancing the capabilities of current offerings centered on the Long-Term Evolution (LTE) standard. So even though there are only two basic competitors in the longer-range market, it's still necessary to have basic knowledge about each one, along with their advantages, disadvantages and applicability for specific applications. Why All the Attention About Connectivity? Why all the focus on connectivity? It comes down to money: Wireless carriers and LPWAN providers charge a fee for every connected device, and the number of IoT devices is growing rapidly. It took more than three decades for global wireless carriers to reach the current 2.3 billion subscribers, but in the few years that IoT services have been available, more than 8.4 billion IoT devices have been connected, and by 2020 there should be at least 20 billion. Even though all IoT devices won't ultimately connect to the Internet, "only" 10 billion of them would still create immense annual revenues for service providers. Needless to say, this is a huge revenue opportunity. However, there are broad differences between IoT applica- tions, and the current capabilities of cellular-based and LPWAN solutions are different, so there is no single standard that will satisfy every need. To illustrate these differences, consider that connecting "smart" electric utility meters (Figure 1) to the Internet in a city with 100,000 residences, businesses, and other water-using entities is vastly different from sending data outward from 250 machines in a single industrial facility. On a sprawling farm, many types of sensors are spread over miles of land rather than in a single building, and the seeming inevitability of autonomous vehicles will create a unique IoT environment of immense complexity requiring connectivity between vehicles as well as fixed infrastructure. Figure 1: There are already nearly 70 million "smart" electricity meters in the U.S., each one transmitting periodic usage updates typically via a LPWAN but soon via cellular networks a well. However, regardless of the application, services provided by wireless carriers and LPWAN providers have the common goal of allowing tiny sensors installed on host devices—such as valves, motors, and pumps—to communicate periodically to an external point for years while powered by a coin cell battery. Although both types of service providers attack this problem in somewhat different ways, both use a variety of techniques expressly designed for the IoT environment. For example, they limit the amount and duration of data transmission and times at which sensors must be communicating, and they also use very low data rates that require only narrow bandwidths. In addition, as low-power signals transmitted by wireless-enabled sensors are very weak, the base station receivers that detect them must be extremely sensitive. The base stations themselves must also use techniques such as Multiple Input Multiple Output (MIMO), illustrated in Figure 2, and in some cases use highly directional antennas to ensure constant connections. Figure 2: Multipath propagation is generally considered highly undesirable, but MIMO exploits it to significantly increase network capacity using multiple transmit and receive antennas at both ends of the transmission path to minimize errors and optimize throughput. Finally, many small base stations (the so-called small cells) will be needed to shorten the distance signals must travel, which reduces latency to the almost instantaneous levels that some IoT applications require. Cellular And LPWANs Compared The cellular industry has unique advantages for IoT. Carriers already have almost ubiquitous LTE coverage in the U.S. delivered by several hundred thousand macro base stations and perhaps three times that many small cells. Updating this infrastructure to accommodate communication with IoT devices in most cases requires just a software upgrade rather than a major investment in hardware such as RF and microwave transceivers. In addition, even before IoT was widely recognized as the next big thing, wireless carriers were already providing connectivity to wireless-en- abled sensors using legacy Second-Generation (2G) technology. The industry has also been working for years to accommodate IoT. The Third Generation Partnership Project (3GPP) that manages develop- ment and issuance of wireless standards has included substantial specifications dedicated to IoT in its latest standard called Release 13 that was finalized in June 2016. These capabilities will continue to be enhanced between now and when the first standards for the fifth generation of cellular will be released, most likely in 2019. By that time, wireless carriers will have a solid foundation in IoT connectivity.

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