Introduction IoT and low-power WAN technology

Introduction IoT and low-power WAN technology

The Internet of Things (IoT) has begun to come into reality. By 2020, it is estimated that billions of services and devices will be connected anytime, anywhere. Smart home, wearable devices, smart cities, smart medicine, smart transportation, smart agriculture, smart instruments, etc., all kinds of new applications emerge in endlessly, promoting the rapid development of new business models.

In order to support the further development of the Internet of Things, the mobile industry has developed new wireless access technologies, including Low Power Wide Area Network (LPWAN). This technology can better support the characteristics and requirements of these devices and their applications.

Low power WAN has been available for some time, but the existing solutions are different, with low standardization, and many security vulnerabilities and reliability problems have arisen. At the same time, the potential operating costs may be higher because it is not well compatible with the existing infrastructure.

Here you can understand the basic driving factors for the application of this new technology in the Internet of Things market, as well as the fundamental reasons for the development of this technology to the current level, and also the challenges faced when adopting this new application. At the same time, you can also learn about new ways to quickly and safely launch narrowband Internet of Things (NB IoT) applications to the market.

Old problems in the new environment

Let's take a real water meter as an example to explain the challenges faced by rapid deployment of narrowband IoT applications. Over the years, the intelligent instrument company has provided various solutions to connect the water meter with the data center through wireless, so as to realize the automatic meter reading function.

The way these meters work is very simple. The equipment continuously measures water consumption and creates small data packets containing basic information. These small data packets will be sent to the center regularly, and only a few bytes will be sent every few hours.

However, in most scenarios, a challenge faced by intelligent instrument companies is that water meters usually cannot use AC power (easy to leak electricity), so they use ordinary batteries for power supply.

To this end, designers have now designed special technologies to solve this demanding problem. However, the following problem is that these companies need to deploy their own network infrastructure, ensure its security, and carry out routine maintenance. The above work requires huge investment, which has set many obstacles for the large-scale popularization of this application. Current solutions usually use proprietary technology, which requires huge investment in infrastructure deployment. Sometimes, the standards followed by these solutions are not formal standards and cannot meet the coverage and power requirements.

In most cases, cellular networks are used as backhaul, allowing all devices to connect to the cloud. Because the solution provided by the cellular low-power WAN technology reuses the cellular infrastructure, the equipment can be directly connected to the operator's network. In this way, operators can adopt stronger and standardized technologies, establish networks covering the whole country, and provide rich value-added services, such as mobile services, roaming, security services and authentication services.

3GPP started to promote a standardization task in 2014, and the narrowband Internet of Things (NB IoT) is the result of this work. As a part of 3GPP version 13 standard, the first version of narrowband IoT technical specification was frozen and released in June 2016 to support similar applications with the following requirements:

– Optimize the network architecture over the existing LTE air interface

– Better deployment flexibility

– Extended indoor coverage (+20 dB compared to GSM)

– Support a large number of two-way communication devices (data transmission rate is only dozens of kbps)

– Low cost equipment (unit price less than $5)

– Low power consumption (battery life exceeds 10 years)

Narrow band IoT is a new wireless access technology. Although it is incompatible with the existing 3GPP equipment, it inherits many characteristics of LTE, such as frequency band, physical layer foundation, parameter value definition and high layer multiplexing (NAS, RRC, RLC and MAC processes). However, it must be noted that since its bandwidth is reduced to 180 kHz (plus the guard band is 200 kHz), it is necessary to create new physical channels and programs different from LTE.

Like other Internet of Things technologies, the ultimate goal of this application is to achieve greater coverage and lower power consumption. In order to reduce equipment complexity and cost, it does not support many basic LTE functions, such as spatial multiplexing, carrier aggregation, evolving multimedia broadcast multicast services (eMBMS) and dual connectivity. It also does not support high-level services, such as IP Multimedia Subsystem (IMS).

Optimized network architecture over existing LTE air interfaces

Although narrowband IoT is incompatible with existing 3GPP devices, it still inherits many LTE features, such as physical layer foundation and high-level architecture.

The only duplex mode to realize standardization is frequency division duplex (FDD); Therefore, the uplink and downlink use different frequencies. At present, there is no time division duplex (TDD) version of the narrowband Internet of Things, and 3GPP has no plans to define this version in the short term.

In order to reduce equipment complexity and cost, 3GPP has made three main design decisions. First of all, the narrowband IoT follows the half duplex design, which eliminates the need to use expensive duplexer filters to separate the transmit and receive links; You can use switches instead. Secondly, MIMO is not supported, especially spatial multiplexing technology, so user equipment (UE) only needs to implement one receiver link. Finally, it is very important that the channel bandwidth is only 180 kHz, which reduces the overall platform cost.

Although narrowband IoT inherits many LTE features, its goal is low data rate and low power consumption applications. Therefore, some advanced data centric LTE/LTE Advanced functions, such as CSI reporting, carrier aggregation, and IMS, are not supported.

Flexibility of cellular IoT deployment

3GPP defines three different deployment modes for the narrowband Internet of Things, supporting deployment in any available spectrum above 180 kHz. The three modes are shown in the figure below.

The separate mode supports the sub switching of GSM carriers to narrowband IoT cells, which is conducive to the multiplexing of the existing 2G spectrum. The protection band uses LTE carriers to protect unused resource blocks in the band, which can achieve guaranteed coexistence. For LTE operators, in band is the best method, because its spectrum utilization is the highest, and the cost of using existing LTE carriers to support narrowband IoT is low. In this example, the narrowband IoT carrier is embedded into the LTE signal by replacing the available LTE physical resource block (PRB), which will not cause the interruption of LTE operation.

Because narrowband IoT devices are expected to support all three modes, narrowband IoT carriers deployed in a separate mode can continue to operate after the spectrum is migrated to LTE (by protecting the frequency band or in band), replanning the spectrum used by the old technology will not cause obstacles.

Each operator can adopt different deployment modes according to the deployed technology and spectrum reorganization plan. Therefore, in order to ensure the global interoperability of IoT devices, all three modes must be properly tested and verified in real use cases.

When configuring the wireless tester as a narrowband IoT base station simulator, you can choose the deployment mode. If in band or protection band deployment is selected, the wireless tester will automatically simulate the narrowband IoT cell and its corresponding LTE cell, avoiding the following complex configuration. This can greatly shorten the setup time and does not require narrowband IoT developers to master too much in-depth knowledge.