Internet of Things, all things connected. However, the device itself is typically connected wirelessly to the IoT system. This wireless connection is the most important or weak link in the system. Therefore, it is important to choose a wireless technology that matches the device and its surroundings. This article describes several wireless candidate technologies that are most likely to be adopted for new designs.
Internet of Things, all things connected. In this era, more and more objects will be connected to the Internet, and eventually to the host / cloud connection. These connections can be implemented using a variety of communication links.
However, the device itself is typically connected wirelessly to the IoT system. This wireless connection is the most important or weak link in the system. Therefore, it is important to choose a wireless technology that matches the device and its surroundings. This article describes several wireless candidate technologies that are most likely to be adopted for new designs.
The device is wirelessly linked to the gateway is a typical IoT connection scenario (Figure). The gateway is an interface that connects to the Internet through a public broadband cable or DSL modem, and then connects to the Internet through an Internet service provider. In another application scenario called machine-to-machine (M2M), the device connection goes through a cellular carrier, then to another carrier, or directly to the Internet.
Figure: Typical wireless connection scenario for IoT (a) and M2M(b) applications
There are many design factors that must be examined in detail when choosing a wireless technology:
• The data rate of the device: video stream, measuring the temperature per minute, or other parameters between.
• Range or distance to the gateway: a few inches from the room, or more than a mile in rural areas.
• Environment: Hazardous environments in the factory, outdoor environments exposed to the weather, noise or electromagnetic interference from electronic equipment.
• Need encryption or authentication: What are the requirements for data security?
• Power consumption: battery life, energy efficiency, and may require AC power.
• Capacity: The number of connected devices.
• Quality of service and reliability.
• Network topology: star, mesh, or other topology.
• Simplex or Duplex: One-way or two-way communication.
• Appropriate and available spectrum: licensed or license-free.
• Available ICs, modules and devices.
• Cost: Design, manufacturing or Internet access service fees.
• Development platform: Do you need an operating system? What other software do you need?
• Internet access: cellular, digital subscriber line (DSL), cable, satellite.
• Standard license conditions are available.
2G/3G cellular
Many use cases, commonly referred to as machine-to-machine (M2M), are similar to the Internet of Things. Many vendors offer cellular phone modules for embedding into other products, and most major cellular operators offer M2M connectivity services on the standard licensed spectrum. Although 2G technologies such as GSM/GPRS/EDGE are popular, some operators have plans to phase out 2G services.
However, most networks still support 3G technologies such as WCDMA and CDMA2000 with data rates of up to several megabits per second. The range is the distance to the cell site and can be as long as several kilometers. Cellular connectivity is clearly an option, but it is more expensive than the other options described later.
802.15.4
802.15.4 targets short-range, low-mid data rates and low-power use cases and is the basis for several other standards mentioned later. Its main operating spectrum is the 2.4GHz Industrial, Scientific, and Medical (ISM) license-free band, which is sometimes used in the 902MHz to 928MHz and 868MHz bands.
The 802.15.4 standard provides packet-based protocols for the PHY and MAC network layers. Other standards add more layers based on this to provide enhanced network capabilities and performance.
6LoWPAN address node
The 6LoWPAN of the Internet Engineering Task Force (IETF) is short for Internet Protocol version 6 (IPv6) based on low-power wireless personal area networks.
The original target of this standard was 802.15.4, which was later adopted by Bluetooth Smart and low-power HaLow Wi-Fi. Specifically, 6LoWPAN defines a way to adapt IPv6 packets into other protocol frames using encapsulation and header compression techniques.
Bluetooth
Perhaps the most widely used short-range wireless technology is Bluetooth (BT) operating in the 2.4 GHz ISM band. Several different versions offer a variety of different data rates, power levels and ranges. The basic working principle is Frequency Hopping Spread Spectrum (FHSS) technology with different modulation methods.
The latest version of Bluetooth is Bluetooth Smart or version 4.1, also known as Bluetooth Low Energy (BLE). This configuration uses shortened packets with a maximum rate of 1 Mb/s and GFSK modulation. Its biggest benefit is its excellent low power consumption. The transmission power is 10mW and its distance is up to 100 meters. There are multiple software profiles for different purposes, and their interoperability certification is effectively compatible.
LoRa
LoRa (Long Distance) is a technology developed by Semtech. The typical operating frequency is 915MHz in the US, 868MHz in Europe, and 433MHz in Asia. LoRa's physical layer (PHY) uses a unique form of frequency-modulated spread spectrum technology with forward error correction (FEC). This spread spectrum modulation allows multiple radios to use the same frequency band, as long as each device uses a different bandwidth and data rate. The typical range is from 2km to 5km and the longest distance is up to 15km, depending on the location and antenna characteristics.
LTE Cat 0/1
LTE is an abbreviation for Long Term Evolution and is the fourth generation of cellular technology.
LTE Cat 0 and Cat 1 are simplified versions of LTE that are specifically designed to match the low power and low speed requirements of M2M. M2M applications, also known as machine-like communications (MTC), use existing cellular networks in the licensed spectrum rather than short-range wireless and the Internet.
The standard LTE network is too wasteful for most basic monitoring and control applications. LTE Cat 0 and Cat 1 are simplified versions that provide the right solution for M2M applications with maximum data rates of 1Mb/s and 10Mb/s. Cat 0 and Cat 1 use existing LTE bandwidth and orthogonal frequency division multiple access (OFDMA) modulation techniques. This long range solution can support a range of several kilometers.
Narrowband Internet of Things (NB-IoT)
A relatively new variant of using LTE for the Internet of Things is the narrowband Internet of Things. Unlike all 10 MHz or 20 MHz bandwidths using standard LTE, the narrowband IoT uses a 180 kHz wide resource block containing 12 15 kHz LTE subcarriers. The data rate is in the range of 100 kb/s to 1 Mb/s.
This more simplified standard provides very low power consumption for networked devices. In addition, it can be deployed as a software overlay into any LTE network. The resource blocks of the narrowband IoT can be well adapted to the standard LTE channel or guard band. When operators repartition their earlier 2G spectrum, they can also fit into the standard GSM channel. The modulation employs an OFDMA downlink and an SC-FDMA uplink.
SIGFOX
SIGFOX is both a wireless technology and a network service. SIGFOX operates in the ISM band of 868MHz and 902MHz, but consumes very narrow bandwidth or power consumption.
SIGFOX radios employ a technique called ultra-narrowband (UNB) modulation, which only occasionally transmits short messages at low data rates. The maximum length of a message is 12 bytes, and the maximum number of messages a node can transmit per day is 140. Due to its narrow bandwidth and short messages, it can achieve a long transmission distance of several kilometers in addition to its 162dB link budget.
Weightless
Weightless is a set of open wireless technology standards that target IoT applications. It comes in three different versions, each corresponding to a different segment of the LPWAN market.
The simplest version is Weightless-N for low cost applications. The goal of this version is for simplex or one-way use, such as sensor monitoring. It works in less than 1Gb of the license-free ISM band. Modulation uses differential BPSK with frequency hopping to minimize interference. 128-bit AES encryption with full signing capabilities is a key feature of this technology. Due to the low data rate and narrow bandwidth channels, the transmission distance can reach 5km.
Wireless Technology List
If you need higher performance two-way communication, Weightless-P may be the best choice. It uses both Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) technology to manage access to multiple 12.5 kHz wide channels. This technique uses GMSK and interleaved QPSK modulation with data rates ranging from low speeds of 200b/s up to 100kb/s. The typical maximum transmission distance is approximately 2km. Support AES-128/256 encryption and signing in security.
The third version is Weightless-W, which is designed to work in the white space of the TV. The blank band is those 6 MHz wide channels previously used by television stations in the 470 MHz to 790 MHz range. It can reach data rates from 1 kb/s to 10 Mb/s, depending on the link budget. The maximum transmission distance can be more than 5km under non-line-of-sight conditions.
Wi-Fi
Wi-Fi is widely used in many IoT applications, the most common being the link from the gateway to the router that connects to the Internet. However, it is also used for major wireless links requiring high speed and medium distance.
Most Wi-Fi versions work in the 2.4 GHz unlicensed band with transmission distances of up to 100 meters, depending on the application. The popular 802.11n speed can reach 300Mb/s, and the updated 802.11ac working in the 5GHz ISM band can even exceed 1.3Gb/s.
A new version of Wi-Fi for IoT applications called HaLow is coming soon. This version is code-named 802.11ah, which uses unlicensed bands from 902MHz to 928MHz in the United States and similar bands below 1GHz in other countries. While most Wi-Fi devices can only reach a maximum of 100 meters under ideal conditions, HaLow can be as far as 1km with the right antenna.
The modulation technique of 802.11ah is OFDM, which uses 24 subcarriers in a 1 MHz channel and 52 subcarriers in a larger bandwidth channel. It can be BPSK, QPSK or QAM, thus providing a wide range of data rates. In most cases, a rate of 100 kb/s to several Mb/s is sufficient - the real goal is low power consumption. The Wi-Fi Alliance revealed that it will complete the 802.11ah testing and certification program by 2018.
Another new Wi-Fi standard for IoT applications is 802.11af. It is designed to use TV white space or unused TV channels from 54MHz to 698MHz. These channels are ideal for long distance and non-line-of-sight transmissions. The modulation technique is OFDM using BPSK, QPSK or QAM. The maximum data rate per 6MHz channel is approximately 24Mb/s, although longer distances are expected in the lower VHF TV bands.
WirelessHART
This is a wireless version of the widely used High Speed ​​Addressable Remote Sensor (HART) industrial networking technology for process monitoring, sensor networking, building automation and transportation. The technology is based on the popular IEEE 802.15.4 standard codenamed 802.15.4e.
WirelessHART adds a time synchronization grid protocol to the base standard. In addition to the mesh topology, it can also be configured in a star configuration. WirelessHART uses TDMA and Time Slot Hopping (TSCH) technology to access up to nodes.
ZigBee
ZigBee is one of the ideal choices for the Internet of Things.
Although ZigBee generally works in the 2.4 GHz ISM band, it can also be used in the 902 MHz to 928 MHz and 868 MHz bands. The data rate is 250 kb/s in the 2.4 GHz band. It can be used in point-to-point, star and grid configurations to support up to 216 nodes. As with other technologies, security is guaranteed by AES-128 encryption. One of the main advantages of ZigBee is the availability of pre-developed software application profiles for specific applications, including the Internet of Things. The final product must be licensed.
Z-Wave
Z-Wave is a single source of proprietary wireless technology. Works in the ISM band of 908.42MHz. It uses efficient GFSK to achieve data rates of 9600b/s or 40kb/s; in some applications it can even reach 100kb/s. Typical power levels are 1 mW (0 dBm) and the maximum coverage is approximately 30 meters, depending on the specific application. Z-Wave can be used in point-to-point links or in star configurations with up to 232 nodes. In terms of security, it uses AES-128 encryption. This technology must be licensed for use in commercial products.
From the table in this article, we can quickly compare the 12 techniques mentioned in the article. At the same time, the Internet of Things market is all-encompassing, involving industries, transportation, agriculture and medical services, and the needs of applications vary. Therefore, for a long tail market such as the Internet of Things, we can be sure that no standard will dominate. However, we can easily find the most appropriate technology for a specific application to correspond to.
Caster wheels Manufacturer
NingBo Casters (China)Tecgnology Co., Ltd112 , http://www.sitez.com