For IoT network designers, achieving interconnection is one of the most frustrating aspects. There are many competing standards around sensors that communicate with each other, and most of them are incompatible. There are two main ways from the edge to the Internet and cloud services: wireless operators and low-power wide area networks (LPWANs). There is undoubtedly fierce competition between them. LPWAN providers use more than one standard, some of which are proprietary standards, while the development route of cellular networks is to focus on simplification and improve the competitiveness of products currently centered on the Long Term Evolution (LTE) standard. Therefore, although there are only two basic competitors in this long-term market, there should be a basic understanding of each competing teammate, including their respective advantages, disadvantages, and applicability of various specific applications.
Why is so concerned about interconnectivity?
Why is all the focus on connectivity? It depends on the price: wireless operators and LPWAN providers charge a certain fee for each connected device, and the number of IoT terminal devices is rapidly increasing. It took more than 30 years for global wireless operators to reach the current 2.3 billion users. However, in the recent years when the Internet of Things has emerged, more than 84 IoT terminal devices have been connected. By 2020, this number will be at least Will reach 20 billion. Although not all IoT devices will be connected to the Internet, "only" 10 billion of them will create huge annual revenue for service providers. Needless to say, this is a huge opportunity, but there are very wide differences between different IoT applications. The current solutions based on cellular networks and LPWAN are different, so no single standard can meet all application requirements.
To illustrate these differences, the smart meter shown in the figure below (Figure 1) is used by 100,000 households, businesses, and other water users in a city and connected to the Internet. This is the same as in a factory. The data sent by 250 machines is very different. In a huge farm, many types of sensors are distributed on the land within miles, instead of a certain building. The emergence of autonomous vehicles will inevitably create a unique Internet of Things. The development environment, this environment will be very complex and requires a connection between the vehicle and the fixed infrastructure.
Figure 1: There are nearly 70 million smart meters in the United States, each of which will be periodically updated via LPWAN, and of course, will use cellular networks soon
However, no matter what applications and services provided by wireless operators or LPWAN providers have a common goal is to be able to install micro-sensors, such as valves, motors, and pumps, on the host device, using button batteries to supply power and within a few years Able to communicate with external devices periodically. Although these two types of service providers use different methods to attack this problem, they both use various technologies to build an IoT environment. For example, they restrict data transmission. The size and interval period of the sensor, and the number of times the sensor must communicate, and they also use a very low data transmission rate, so that only a very narrow bandwidth is required.
In addition, the low-power signals sent by wireless sensors are very weak, and the base station receiver that detects them must be very sensitive. The base station itself will also use some technologies, such as MIMO (Multiple Input Multiple Output), as shown in Figure 2. In some cases Downstream also requires the use of highly directional antennas to ensure continuous connectivity.
Figure 2: Although multipath propagation is very unpopular, MIMO technology uses it
By using multiple transmitting and receiving antennas at both ends of the transmission path, the network capacity can be greatly increased, while the bit error rate can be reduced and throughput can be optimized.
Finally, many small base stations (or become small units) will need to shorten the signal transmission distance, which will reduce the delay, almost reaching the level of the instantaneous response of IoT applications.
Comparison of cellular networks and LPWANs
Cellular networks have unique advantages for Internet of Things applications. Telecom operators in the United States have almost ubiquitous LTE network coverage, with hundreds of thousands of large base stations and three times the number of small base stations providing long-term services. In most cases, updating this infrastructure to meet the communication needs of IoT devices only requires software upgrades, rather than requiring a large amount of hardware investment like RF and microwave transceivers. In addition, although IoT was widely regarded as the next major event before, in fact, wireless operators have used the previous second-generation technology (2G) to provide communication connections for wireless sensors.
The industry has also struggled to adapt to the Internet of Things for many years. The Third Generation Partnership Project (3GPP) is responsible for managing the development and release of wireless standards, which includes a large number of specifications for IoT in the latest standards, which were finalized in June 2016. These functions will continue to be enhanced when the first standard for fifth-generation cells will be released in 2019. By then, wireless operators will lay a solid foundation in IoT connectivity.
In contrast, LPWAN providers have no such advantages. They are an emerging force in the field of wireless communications, so every coverage area and every system must be built from scratch. And the time left for them to deploy these networks in key areas (typical cities) is also very limited, because the cellular network industry is rapidly launching IoT-centric data plans. Fortunately, compared with cellular networks, LPWAN systems have lower construction and deployment costs, do not always need expansion space, and use fewer base stations to cover a wider geographic area.
The question now is whether LPWAN vendors can have a chance to survive in an environment dominated by cellular networks. Most analysts believe this is no problem, because they provide some functions similar to cellular networks, such as carrier-grade security and other mandatory features, and the cost will be more competitive for customers. Analysts also recommend that at least half of IoT cases will use LPWAN services. Therefore, this is a relatively safe bet. Although cellular networks dominate in providing IoT connectivity, they still have a place for LPWAN providers, and there may be price wars in certain single markets.
Cellular Internet of Things
As mentioned earlier, cellular networks are developing IoT interconnection-oriented solutions based on LTE. The overall development path of this industry is to develop and continue to improve on the existing LTE version, including reducing complexity and cost, along with this process With the unfolding, cellular network technology will become more suitable for a wide range of IoT applications, and will eventually promote the launch of the fifth-generation cellular network technology 5G.
The consensus of the industry is mainly focused on the use of three different standards, which are all introduced in the latest standard Release 13. These specifications will eventually be integrated into the 5G standard. Ideally, these solutions should be implemented at frequencies below 1GHz, because this condition is conducive to long-distance transmission and building penetration:
LTE-M: Also known as Enhanced Machine Communication (eMTC), it was developed from the Release 12 standard and further improved in the Release 13 standard.
NB-IoT: The narrowband version of LTE involved in the Release 13 standard.
EC-GSM-IoT: IoT-oriented extended coverage GSM is an extended version of the global mobile communication system. IoT applications are optimized in Release 13, which can be deployed together with GSM operators.
5G: Standardization will be completed in 2020 and will be enhanced on the basis of NB-IoT and EC-GSM-IoT.
A bold speculation is that because the requirements of IoT applications are significantly different from traditional cellular network operations, the future development of using energy-saving modes should positively affect battery life, reduce complexity and equipment costs, and reduce deployment through shared operating facilities Cost, using more advanced coding techniques and increasing signal density can achieve a larger range of network coverage.
Table 1 shows the development of cellular network technology. For example, for traditional cellular network applications, Release 8 provides a peak downlink rate of up to 150Mb/s, but the data rate drops sharply to 150Kb/s in a narrow frequency band to meet the requirements of IoT applications The same is true for the channel bandwidth of user equipment, which drops from the maximum 18MHz to 180KHz in the Release 8 standard. Another important factor is the complexity of modulation and demodulation, which has been reduced by approximately 85% with continuous development. In short, in order to meet the needs of IoT applications, the development of cellular network technology is in many ways the opposite of the standards that traditional voice and data services must implement in 5G. That is to say, it is better to increase the data rate than to increase the data rate. It reduces the complexity of cellular IoT networks and components.
Some choices of LPWAN standard
LPWAN providers use open source standards such as LoRaWAN, managed by the LoRaWAN Alliance, or use proprietary solutions such as Sigfox, which operate within the authorized frequency band, although Sigfox claims it is the world's leading IoT interconnection service , Has been used in 32 countries (mostly in Europe), but LoRaWAN has received the most widespread recognition in the industry, with more than 400 alliance members, which means that the cost of LoRa baseband and RF hardware will continue to decrease, and it has been reduced by half. Above, with the expansion of scale, the cost will be further reduced.
LoRaWAN
It is very important to be able to distinguish between LoRa, LoRaWAN and the products offered by LinkLabs, because it is indeed a bit confusing. LoRa is an open standard physical layer managed by the LoRaWAN Alliance, while LoRaWAN provides a network function media access control (MAC) layer. LinkLabs is a member of the LoRaWAN Alliance. It uses the Sematech LoRa chipset and provides Symphony Link solutions. The solution has some exclusive features, such as the ability to operate without a network server. Symphony Link uses an eight-channel base station, operating at 433MHz or 915MHz in the industrial, scientific and medical (ISM) band and the 868MHz frequency band used in Europe. Its transmission distance is at least 10 miles, and it uses WiFi, cellular network or Ethernet to transmit data with the help of cloud servers, so as to realize routing message processing, supply and network management functions.
Sigfox
The Sigfox standard is designed by a French company of the same name. One of the main differences between it and LoRaWAN is that Sigfox has all the technologies from the periphery or server and terminal. It is actually the supplier of the entire ecological network, and in some cases it is also a network operation. However, this company allows its terminal technology to be freely used by any organization that agrees to its terms, so that it has been able to establish contacts with major IoT equipment suppliers and even some wireless operators. Like LoRaWAN, Sigfox is also Continue to expand market share, especially in Europe. The transmission distance supported by it is in full compliance with the guidelines set by the European Union. In order to meet the regulations of the Federal Communications Commission (FCC), the version used in the United States is very different. The only disadvantage of Sigfox It is its exclusive characteristics.
Weightless
Weightless is a unique kind of IoT interconnection solutions. It is a truly open standard. It is currently managed by the Weightless Special Rights Organization. Its name comes from its "lightweight" protocol, which is usually transmitted every time. Only a few bytes of data are transmitted, which is a good choice for IoT devices that only need to transmit very little data for communication, such as certain types of industrial and medical equipment, smart electricity meters, and water meters. Unlike many other standards, Weightless operates in the so-called TV idle frequency band, below 1GHz. When they switch from analog to digital transmission, wireless broadcasters will vacate this band. Because the frequency is below 1GHz, they have a relatively high frequency. With a large coverage area, the power transmitted from the base station is also low, and the ability to penetrate buildings and other structures that are challenging to RF signals is also relatively strong.
There are currently two versions of Weightless:
Weightless-N is an ultra-narrow band, single-pass communication technology
Weightless-P is the company's flagship two-way communication technology, with carrier-class performance and safety, and uses extremely low power consumption.
Nwave
Nwave is an ultra-narrow band technology based on SDR (Software Defined Radio), which can operate in authorized and unlicensed frequency bands. The base station can accommodate 1 million IoT devices, covering a range of 10KM, and the RF signal output power is 100mW The data rate can reach 100bps. The company claims that battery-powered equipment can continue to operate for up to 10 years. When operating at a frequency of 1GHz, Nwave can take advantage of the ideal transmission characteristics of the region.
Ingenu
Ingenu (previously known as On-Ramp Wireless) has developed a two-way solution based on years of research and realized a proprietary direct sequence spread spectrum modulation technology called RPMA (Random Phase Multiple Access), the design purpose of RPMA It provides high-capacity, safe and wide-ranging interconnection solutions in the 2.4GHz frequency band.
In the United States, a single RPMA access point can cover an area of ​​176 square meters, which is much larger than Sigfox and LoRa standards. It has minimal overhead, low latency and broadcast functions, and can send commands to a large number of devices at the same time, hardware and software And other functions are limited to those provided by the company. This company has to build its own public and private networks dedicated to machine-to-machine communication.
to sum up
Since only cellular network and LPWAN providers are vying for dominance in the long-term market, it is easy to think that the job of a designer is simple compared with those short-distance solution requirements, and a constant truth is every competing technology Both provide different degrees of expansion, which will help enhance their capabilities, but also bring greater design challenges.
For end users, choosing the "right" solution usually boils down to what services are available in their field and the corresponding costs. However, if multiple wireless operators and LPWAN providers can provide services in the same area, Then the decision is a bit difficult. For the Internet of Things interconnection field, it will take several years to determine the final winner.
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