LPWAN or LPN, the full name of LowPower Wide Area Network or LowPower Network, refers to a wireless network. This wireless network emphasizes low power consumption and long distance, and is usually used for battery-powered sensor node networking. Because of the characteristics of low power consumption and low speed, this network is distinct from other wireless networks (such as WiFi, Bluetooth, etc.) used for business and personal data sharing.
In application, LPWAN can use a concentrator to form a private network, or use a gateway to connect to a public network.
Because LPWAN has a similar name to LoRaWAN, coupled with the recent upsurge of LoRaWAN in the IoT field, many people are confused about these two concepts. In fact, LoRaWAN is only one type of LPWAN, and there are several similar technologies competing with LoRaWAN.
The relationship between LPWAN vs LoRaWAN
1. LPWAN compared to other wireless networks
Features of LPWAN:
1.1 Two-way communication, with response
1.2 Star topology (generally, neither repeaters nor Mesh networking is used for simplicity)
1.3 Low Data Rates
1.4 Low cost
1.5 Very long battery life
1.6 Long communication distance
1.7 Suitable applications for LPWAN:
1.8 IoT, M2M
1.9 Industrial Automation
1.10 Low-Power Applications
1.11 Battery powered sensors
1.12 Smart City, Smart Agriculture, Meter Reading, Street Light Control, etc.
2. What is LPWAN?
The Internet of Things refers to a network of billions of devices around the world connected to the Internet. Common IoT devices include wearable devices and smart home devices. These kinds of apps basically gain some convenience at the expense of some privacy. In the industrial field, the advantages of the Internet of Things are extremely significant. It can not only improve productivity, reduce costs, and reduce energy consumption, but also allow machines to read massive amounts of data and perform actions accordingly. By analyzing the data generated by all your IoT devices, you can increase your productivity or provide better service to your customers. New types of services can be offered and expanded as you gain a deeper understanding of your customers.
LPWAN is a technology that meets both coverage and battery life needs. It provides the longest range with very little power consumption and only a slight drop in data rate.
Many smart city and smart utility applications, such as smart street lighting, humidity sensors, smart metering, and smart parking, do not require high data rates, but require very broad coverage. This is where LPWAN can come in handy.
3. The relationship between LoraWAN and Lora
Also because of the similar names, many people confuse the concepts of LoRaWAN and LoRa. In fact, LoRaWAN refers to the networking protocol of the MAC layer. And LoRa is just a physical layer protocol. Although the existing LoRaWAN networking basically uses LoRa as the physical layer, the LoRaWAN protocol also lists that GFSK can also be used as the physical layer in certain frequency bands. From the perspective of network layering, LoRaWAN can use any physical layer protocol, and LoRa can also be used as the physical layer of other networking technologies. There are actually several competing technologies with LoRaWAN that also employ LoRa at the physical layer.
LoraWAN network layering (the physical layer uses Lora, but it should be noted that the physical layer is independent of the MAC layer. As for the wireless frequency band, the ISM frequency band is used, but from a technical point of view, any other frequency band can also be used)
4. The main competing technologies of LoraWAN
There are several LPWAN technologies on the market that also use LoRa as the physical layer, such as AISenz Inc.'s aiCast. aiCast supports unicast, multicast and multicast, which is more complex and complete than LoRaWAN. Many applications that are not possible under LoRaWAN can thus be realized.
Sigfox uses slow rate BPSK (300bps), and there are some more promising application cases.
NB-IoT (Narrow Band-IoT) is an IoT network based on existing mobile communication technology in the telecommunications industry. It is characterized by the use of existing cellular communication hardware and frequency bands. Whether it is a telecommunication business or a hardware business, they are very enthusiastic about this technology.
5. LPWAN Technology Comparison
Because cellular networks are expensive, power-hungry, and require expensive hardware and services, many network providers have turned to unlicensed spectrum (such as LoRa, SIGFOX, and Telensa) to develop their wireless network. These suppliers develop their own low-cost base stations for applications such as critical infrastructure and agriculture. They start with a small coverage area, gradually expand the coverage of the infrastructure to the whole country or region, and finally connect to the cloud through a cellular backhaul link.
On the other hand, licensed LPWAN technologies such as 3GPP NB-IoT or LTE Cat-M1 support software updates to existing cellular infrastructure, such as upgrading existing LTE and GSM base stations. By reusing existing 3G or 4G spectrum, they can rapidly achieve national and international coverage and deployment. These technologies support applications that rely on broad coverage, such as vehicle tracking, pet tracking, and logistics. As technology evolves, they continue to develop stronger standards to expand services into other areas, such as mobile communications, roaming, security and authentication.
Licensed and unlicensed LPWAN technologies have a few things in common: both have high link budgets and long battery life. The main difference between the two is the ecosystem around these technologies.
SIGFOX is an ecosystem of multiple chip vendors whose products use sub-GHz spectrum bands, and Sigfox manages the protocols and certifications. The company offers very small packets (12 bytes) and very low installation cost, and is one of the first LPWAN vendors.
LoRa is a proprietary technology whose chips are provided by Semtech. LoRaWAN is a protocol built on the LoRa technology developed and certified by the LoRa Alliance. LoRaWAN is primarily a media access control (MAC) layer protocol that provides extreme flexibility for applications, but also presents a major challenge for engineers developing complete solutions.
Narrowband Internet of Things (NB-IoT), LTE Cat-M1, and EC-GPRS are all cellular IoT standards that employ a multi-vendor ecosystem of chips or devices from multiple manufacturers. Like other cellular formats, its certification is managed by GCF/PTCRB. You can support these new technologies by simply upgrading the software used by your existing cellular infrastructure. Although they came out a few years later than unlicensed technologies, they have been widely adopted by domestic and international businesses since their release to support applications that require large coverage, such as vehicle tracking, logistics, and asset tracking.
LTE Cat-M1 is a revision of the LTE technology released by 3GPP and is a simplified version of the existing technology. It uses simpler, cheaper chipsets and can provide faster data rates than other LPWAN technologies. LTE Cat-M1 is also supported through software updates to existing LTE infrastructure. The Cat-M1 was originally deployed in the United States.
NB-IoT is a new technology released by 3GPP that can be supported through a software update to LTE or existing RAN infrastructure. Compared to other technologies, the advantages are relatively low device cost and good link budget. NB-IoT is initially deployed mainly in Asia or Europe.
EC-GPRS is an improved version of GPRS that can be supported with a software update to the existing GSM infrastructure. Through signal relay or retransmission, it can achieve a better link budget than GPRS.
Other LPWAN formats include Telensa, Ingenu, and Weightless. Telensa is a single-vendor device that uses chips from multiple manufacturers and operates in the sub-GHz band. The vertically integrated manufacturer mainly focuses on the smart street lighting business and is starting to enter the parking sensor space. Telensa has been widely deployed in street lighting applications in the UK, US and Asia. Ingenu is based on its proprietary RPMA technology and operates in the unlicensed 2.4 GHz frequency band. Weightless has three different wireless designs and is managed by the Weightless Special Interest Group (SIG).
6. LPWAN requirements and challenges
LPWAN technologies come in all shapes and sizes, but they all share some characteristics in order to meet the requirements of IoT applications.
Reliability: Provides 10 years or more of operation without human intervention, self-recovery after IoT service interruption
High density: supports a large number of connected devices
Low cost: modules cost less than $5 each
Excellent battery life: 10+ years of life, typically several messages a day, each containing tens of bytes for extended battery life
Maximum Coverage: Covers hard-to-reach or remote areas
Meeting these requirements is a challenge for IoT device vendors.
Reliability: To ensure reliability, device manufacturers must recreate different real-world operating scenarios in the lab or on the production line and test them with a high degree of repeatability. They also need to test for adverse scenarios, such as IoT server outages and connection failures, to make sure the device can recover on its own without consuming too much power.
Maximum coverage: To ensure maximum coverage, manufacturers need to simulate different RF environments, including remote locations, basements, hidden locations, concrete buildings, and industrial environments, where RF conditions vary widely. Device manufacturers need to perform transmitter and receiver characterization to understand how IoT devices perform under these different RF conditions.
Longer battery life: To extend battery life, manufacturers need to analyze the current consumption of IoT devices in active, idle, standby and sleep modes. Device manufacturers also need to re-establish operating conditions such as remote software updates, repeated transfers at extreme coverage conditions, and the inability of devices to connect to servers to fully understand how much current is required in each scenario.
Low component cost: To effectively reduce component cost, many manufacturers use low-cost components and simplify hardware design. The performance of these components must be carefully characterized to ensure that their reliability is not compromised. Careful selection of the correct test setup can help reduce component costs. A complete solution can cover the entire product development cycle from design, manufacturing to compliance testing to help customers significantly reduce test set capital expenditures.
Wide range of formats supported: Products from many manufacturers use different LPWAN technologies to meet the requirements of different applications and countries. Therefore, they need a test solution that supports the most LPWAN technologies.
Acceptance or certification testing: Components using cellular technology, such as NB-IoT modules and Cat-M1 modules, must pass certification and regulatory tests such as GCF and PTCRB. You must perform multiple use-case tests on these components to ensure compliance with the relevant standards.
7. Introduction to key technology Lora
The core technology of LoRaWAN is LoRa. LoRa is a proprietary modulation technology of Semtech (acquired from CycleoSAS in 2012). In order to facilitate the understanding of readers who are not familiar with digital communication technology, two common modulation technologies, FSK and OOK, are introduced first. These two modulation methods are chosen because:
7.1 These two are the simplest, most basic, and most common digital communication modulation methods
7.2 It is supported at the same time as LoRa on Semtech's SX127x chip, especially FSK is often used to compare performance with LoRa.
8. OOK
The full name of OOK is On-Off Keying. The core idea is to use a carrier to represent a binary value (usually 1, or 0 in the reverse direction), and no carrier to represent another binary value (0 in the forward direction and 1 in the reverse direction).
When switching between 0 and 1, a relatively short empty carrier-free interval is also inserted, which can add a little redundancy to the multipath delay for demodulation at the receiving end. OOK is advantageous for low-power wireless applications, because only about half of the carrier is transmitted, and the carrier can be turned off the rest of the time to save power. The disadvantage is that the anti-noise performance is poor.
9. FSK
The full name of FSK is Frequency Shift Keying. The LoRaWAN protocol also states that (G)FSK is also supported in addition to LoRa in some frequency bands. The core idea of ??FSK is to use two frequency carriers to represent 1 and 0 respectively. As long as the difference between the two frequencies is large enough, the receiver can use a simple filter to complete the demodulation.
For the transmitter, the simple way is to make two frequency generators, one frequency is in Fmark, and the other frequency is in Fspace. FSK modulation can be accomplished by controlling the output with 1 and 0 of the baseband signal. However, in such an implementation, the phases of the two frequency sources are usually not synchronized, resulting in discontinuity when switching between 0 and 1, which will eventually cause additional interference to the receiver. The actual FSK system usually uses only one frequency source, and the control frequency source shifts when 0 and 1 are switched.
GFSK is to add a Gaussian (Gaussian) window before the baseband signal enters the modulation to make the frequency offset smoother. The purpose is to reduce the power of sideband frequencies to reduce interference to adjacent frequency bands. The tradeoff is increased intersymbol interference.
