I. Major Classifications of Wireless Communication Technologies
1. U.S. Communications Commission (FCC) Classification
In 2015, the U.S. Federal Communications Commission's (FCC) Technology Advisory Committee (TAC)
The Cybersecurity Working Group of the Internet of Things (IoT) categorized IoT communication technologies into the following four types in a white paper:
Mobile/WAN, Wide Area Network - Mobile wide area network with wide coverage.
WAN, Wide Area Network, has a large coverage area and is not a mobile technology.
LAN, Local Area Network – has a relatively small coverage area, such as residential areas, buildings, or campuses.
PAN, Personal Area Network - coverage ranges from a few centimeters to several meters.
The main wireless technologies and their classifications are shown in the table below:
For some reason, the FCC TAC categorized Sigfox as a LAN and LoRaWAN as a WAN. Both Sigfox and LoRaWAN belong to the narrowband technology category of LPWAN, and both offer wide-area coverage. Weightless SIG will primarily promote Weightless-P in the LPWAN field. NB-IoT is not included either. New technologies are constantly emerging and reshaping the landscape of the IoT market.
2. KEYSIGHT Classification
In a PowerPoint presentation titled "Low Power Wide Area Networks, NB-IoT and the Internet of Things," KEYSIGHT provides a detailed breakdown of IoT wireless technologies, as shown in the diagram below:
KEYSIGHT categorizes wireless communication technologies into three main types based on their communication range or distance: 10cm, 5km, and 100km.
3. Close range and long range
As can be seen from the above classification, wireless communication technologies are basically categorized by coverage area or communication distance. After some refinement, we have divided communication technologies into two main categories: short-range and long-range communication technologies, as shown in the following diagram:
Narrowband wide-area optics has been one of the fastest-growing fields in the past two years, with NB-IoT and LoRa network construction in China proceeding rapidly. However, there isn't a complete historical record of transmission performance, and it's primarily used in civilian applications, such as smart parking systems. In my country, short-range wireless communication technology is relatively mature, and the industry chain is well-established. Wireless product quality varies greatly, and prices differ significantly, so it's crucial to choose products based on specific applications. For personal testing, lower-priced products are sufficient. For industrial manufacturing applications requiring long-term use, reputable brands should be chosen. As the saying goes, you get what you pay for; the quality of the core hardware in a stable and reliable product is the primary guarantee of stability.
4. Institute of Electrical and Electronics Engineers (IEEE)
The Institute of Electrical and Electronics Engineers (IEEE) has defined several standards, such as the IEEE 802 series of standards for local area networks (LANs) and metropolitan area networks (MANs), which have also become the basis for some Internet of Things (IoT) technologies.
These main standards include:
IEEE 802.11 Wireless LAN (WLAN) & Mesh (Wi-Fi certification)
IEEE 802.15 Wireless PAN
IEEE 802.15.1 Bluetooth certification
IEEE 802.15.3 High-Rate wireless PAN (eg, UWB, etc.)
IEEE 802.15.4 Low-Rate wireless PAN (eg, ZigBee, WirelessHART, MiWi, etc.)
IEEE 802.15.6 Body area network
IEEE 802.11 defines a set of Media Access Control (MAC) and Physical Layer (PHY) specifications for enabling wireless local area network (WLAN) computer communication in the 900MHz, 2.4GHz, 3.6GHz, 5GHz and 60GHz frequency bands, and is now the standard commonly used in wireless local area networks.
IEEE 802.15 defines the Wireless Personal Area Network (WPAN) standard, which has 10 main areas.
IEEE 802.11ah, also known as "Wi-Fi HaLow," is a WLAN network defined in the unlicensed 900MHz frequency band. Compared to 2.4GHz and 5GHz Wi-Fi, it consumes less power and has a longer range. 11ah can be used in a variety of applications, including large-scale sensor networks.
IEEE 802.15.4c China's WPAN has added new RF spectrum specifications: 314-316MHz, 430-434MHz, and 779-787MHz.
The IEEE 802.11p communication protocol is primarily used for wireless communication in automotive electronics. It is an extension of IEEE 802.11, mainly targeting applications related to Intelligent Transportation Systems (ITS).
IEEE 802.15.4 is the technical standard for Low-Rate Wireless Personal Area Networks (LR-WPANs). It forms the basis for technologies such as ZigBee/ISA100.11a/WirelessHART/MiWi and Thread, all of which extend the standard by developing upper layers not defined in IEEE 802.15.4. Additionally, it can be used with 6LoWPAN to define upper layers.
Sensing technologies collect data, while the transport layer is responsible for transmitting and processing various types of information. IoT transport layer technologies can be mainly divided into short-range wireless communication technologies and long-range wireless communication technologies based on distance. Short-range wireless communication technologies mainly include RFID, NFC, ZigBee, Bluetooth, and WiFi, with typical applications such as intelligent transportation and intelligent logistics. Wide-area network (WAN) communication technologies are generally defined as LPWAN (Low Power Wide Area Network), with typical applications including LoRa, NB-IoT, BTA-OIT (Browser-to-Internet-IT), 2G/3G cellular communication technologies, LTE, and 5G technologies.
I. Bluetooth
Bluetooth technology is a short-range wireless digital communication standard jointly proposed by Toshiba, IBM, Intel, Ericsson, and Nokia in May 1998. Bluetooth is a low-power, short-range wireless connection technology that can penetrate walls and other obstacles, enabling secure, flexible, low-cost, and low-power voice and data communication between various digital devices through a unified wireless link. Its goal is to achieve a maximum data transmission speed of 1 Mb/s (effective transmission speed of 721 kb/s) and a maximum transmission distance of 10 meters. It utilizes the 2.4 GHz ISM (Industrial, Scientific, and Medical) free spectrum band, which can be used without application. This band has 79 channels with a bandwidth of 1 MHz, switching frequencies 1600 times per second, and uses spread spectrum technology for radio wave transmission and reception.
Bluetooth is a short-range wireless communication technology specification. It boasts advantages such as small size and low power consumption, and is widely used in various digital devices, especially mobile and portable devices that do not require high data transmission rates. The characteristics of Bluetooth technology are as follows:
(1) Global applicability. Bluetooth operates in the 2.4GHz ISM band. In most countries around the world, the ISM band ranges from 2.4 to 2.4835GHz, which is a free band. No license application is required from government authorities to use this band.
(2) Simultaneous transmission of voice and data. Bluetooth employs circuit switching and packet switching technologies, supporting one data channel, three voice channels, and a channel for simultaneous asynchronous data and synchronous voice transmission. Each voice channel has a data rate of 64 kb/s, and the voice signal is encoded using Pulse Code Modulation (PCM) or Continuously Variable Slope Decrement Modulation (CVSD). When using an asymmetric channel for data transmission, the maximum rate is 721 kb/s, and inversely, 57.6 kb/s; when using a symmetric channel, the maximum rate is 342.6 kb/s. Bluetooth has two link types: Synchronous Directed Connection (SCO) link and Asynchronous Connectionless (ACL) link.
(3) Temporary peer-to-peer connections can be established. Based on their role in the network, Bluetooth devices are divided into master devices and slave devices. A master device is the Bluetooth device that actively initiates the network connection request. When several Bluetooth devices are connected to form a piconet, there is only one master device, and the rest are slave devices. A piconet is the most basic form of Bluetooth network; the simplest piconet is a point-to-point communication connection consisting of one master device and one slave device.
(4) It has excellent anti-interference capabilities. Many wireless devices operate in the ISM band, such as wireless local area networks (WLANs) and household microwave ovens. To effectively resist interference from these devices, Bluetooth uses frequency hopping to spread the spectrum. The 2.402~2.48GHz band can be divided into 79 frequency points, with adjacent frequency points spaced 1MHz apart. After transmitting data on a certain frequency point, a Bluetooth device hops to another frequency point to transmit. The frequency points are arranged pseudo-randomly, and the frequency can change 1600 times per second, with each frequency lasting approximately 625 seconds.
(5) Small size and easy integration. The small size of personal mobile devices means that the Bluetooth module embedded inside them is even smaller.
(6) Low power consumption. Bluetooth devices have four working modes in the communication connection state: Sniff mode, Active mode, Hold mode, and Park mode. Active mode is the normal working state, and the other three are low power consumption modes specified for energy saving.
(7) Open interface standards. In order to promote the use of Bluetooth technology, the SIG has made all Bluetooth technical standards public. Any organization or individual worldwide can develop Bluetooth products, and as long as they can pass the SIG's Bluetooth product compatibility test, they can promote them to the market.
(8) Low cost. With the continuous expansion of market demand, various suppliers have launched their own Bluetooth chips and modules, causing the price of Bluetooth products to drop rapidly.
Bluetooth technology stipulates that for each pair of devices to communicate, one must be the master device and the other the slave device. During communication, the master device must initiate the pairing process. Once the connection is successfully established, both devices can send and receive data. Theoretically, one Bluetooth master device can communicate with up to seven Bluetooth slave devices simultaneously. A device with Bluetooth communication capabilities can switch between these two roles: normally operating in slave mode, waiting for other master devices to connect, and switching to master mode when needed to initiate calls. When a Bluetooth device initiates a call in master mode, it needs to know the other device's Bluetooth address, pairing passcode, and other information. After pairing is complete, it can directly initiate a call.
The Bluetooth master device initiates a call by first searching for nearby discoverable Bluetooth devices. Once the master device finds the slave device, it requires the slave device's PIN code for pairing; some devices may not require a PIN code. After pairing, the slave device records the master device's information, and the master can then initiate a call to the slave. Paired devices do not need to be re-paired for subsequent calls. A paired device, such as a Bluetooth headset acting as a slave, can also initiate a connection request. Once the link is successfully established, bidirectional voice or data communication can occur between the master and slave devices. During communication, both the master and slave devices can initiate a disconnection and break the Bluetooth link.
In Bluetooth data transmission applications, one-to-one serial communication is one of the most common uses. Before leaving the factory, Bluetooth devices are pre-configured with pairing information between the two devices. The master device pre-stores the slave device's PIN code, address, etc. The two devices automatically establish a connection upon power-up, enabling transparent serial transmission without external circuitry intervention. In one-to-one applications, the slave device can be configured in two types: a silent state where it cannot be found by other Bluetooth devices; and a state where it can be found by the designated master device and can be found and connected by other Bluetooth devices.
The Bluetooth system is functionally divided into four units: Link Controller, Radio Frequency Unit (RF Unit), Bluetooth Protocol Unit, and Link Manager Unit. The RF Unit is primarily responsible for transmitting and receiving data and voice. Bluetooth antennas are characterized by their small size, light weight, short range, and low power consumption. The Link Controller converts RF signals to and from digital or voice signals, implementing the baseband protocol and other underlying connection procedures. The Link Manager manages communication between Bluetooth devices, performing operations such as link establishment, authentication, and link configuration. The Bluetooth protocol is a protocol designed for wireless communication within a personal area, consisting of two parts: the Core and the Profile. The protocol stack uses a layered structure, performing functions such as data stream filtering, transmission, frequency hopping and data frame transmission, connection establishment and release, link control, and data assembly/disassembly.
II. ZigBee
The Internet of Things (IoT) primarily encompasses wireless sensing and process communication technologies. Process communication technologies include RFID, Bluetooth, WiFi, and ZigBee. ZigBee is one of the most popular technologies in wireless sensor networks. It can be used in building monitoring, cargo tracking, and environmental protection. Sensor networks require nodes to be low-cost, easy to maintain, low-power, capable of automatic networking, and highly reliable. ZigBee offers significant advantages in networking and low power consumption.
ZigBee technology is a short-range, low-power wireless communication technology. It is derived from the figure-eight dance of bees. Bees communicate the location of pollen to their companions by flying and "buzzing" (zig) with their wings. The ZigBee protocol is similar in its characteristics, hence the name ZigBee.
ZigBee technology employs AES (Advanced Encryption System), which is 12 times more secure than bank card encryption, resulting in high security. Furthermore, ZigBee uses a cellular network architecture, allowing each device to communicate with the gateway in multiple directions, ensuring network stability. ZigBee devices also function as wireless repeaters, relaying communication information and extending the wireless range to over 1000 meters. In addition, the theoretical network capacity of ZigBee is 65,300 nodes, sufficient for home network coverage needs. Even in smart communities and smart buildings, only a single host can achieve full coverage. ZigBee also features bidirectional communication capabilities, sending commands to devices while the devices simultaneously provide feedback on their execution status and relevant data. ZigBee utilizes an extremely low-power design, capable of being powered entirely by a battery, theoretically lasting over two years on a single battery.
ZigBee uses DSSS technology and has the following characteristics:
(1) Low power consumption. According to the ZigBee Alliance website, ZigBee products can last from months to years compared to ordinary batteries. This determines the demand for devices that need to replace their batteries for a year or even longer.
(2) Multiple access devices. ZigBee's solution supports 255 active nodes per network coordinator, and multiple network coordinators can connect large networks. The 2.4GHz band can accommodate 16 channels, and each network coordinator has 255 active nodes (Bluetooth only has 8). ZigBee technology allows more than 4,000 nodes in a single network.
(3) Low cost. ZigBee only requires a processor like the 80C51 and a small amount of software, without the need for a host platform. From antenna to application implementation, only one chip is needed. Bluetooth relies on a more powerful host processor (such as ARM7), and the chip architecture is also more complex.
(4) Low transmission rate. ZigBee’s low power results in a low transmission rate. Its raw data throughput is 250kb/s in the 4GHz (10-channel) band, 40kb/s in the 915MHz (6-channel) band, and 20kb/s in the 868MHz (1-channel) band. The transmission distance is 10~20m.
(5) Low latency. ZigBee has a fast response speed. It generally takes only 15ms to switch from sleep to working state and only 30ms to connect to the network, which further saves power.
(6) High capacity. ZigBee can adopt star and mesh network structures, with one master node managing several child nodes. One master node can manage up to 254 child nodes; at the same time, the master node can also be managed by the network node at the next higher level, forming a large network of up to 65,000 nodes.
(7) High security. ZigBee offers three security modes, including no security settings, using access control lists (ACLs) to prevent unauthorized data access, and using symmetric cryptography with an advanced encryption standard (AES128) to flexibly determine its security attributes.
(8) License-free bands. The Industrial, Scientific and Medical (ISM) bands are used, namely 915MHz (USA), 868MHz (Europe), and 2.4GHz (global). Besides the different physical layers, the channel bandwidths of these three bands also differ, at 0.6MHz, 2MHz, and 5MHz respectively. They have 1, 10, and 16 channels respectively. The spreading and modulation methods for these three bands also differ. Direct Sequence Spread Spectrum (DSSS) is used for all three, but the bit-to-chip conversion varies significantly. Phase modulation is used for all three, but BPSK is used for the 868MHz and 915MHz bands, while OQPSK is used for the 2.4GHz band.
III. NFC
NFC (Near Field Communication), also known as short-range wireless communication, is a high-frequency wireless communication technology that enables contactless point-to-point data transfer (less than 10cm) between electronic devices. NFC evolved from contactless radio frequency identification (RFID) and internet technologies, and is backward compatible with RFID. It was initially developed by Sony and Philips, primarily for providing M2M (Machine-to-Machine) communication in handheld devices such as mobile phones. NFC allows consumers to easily and intuitively exchange information, access content and services. Since its introduction in 2003, NFC has gained popularity and support from numerous companies due to its excellent security and ease of use.
NFC, as a logical connector, enables rapid wireless communication on devices. By bringing two NFC-enabled devices close together, NFC can wirelessly configure itself and initialize other wireless protocols, such as Bluetooth and IEEE 802.11, allowing for short-range communication or data transfer. NFC can be used for data exchange, offering short transmission distances, fast connection creation, high transmission speeds, and low power consumption. NFC's functionality is very similar to Bluetooth, both being short-range communication technologies frequently integrated into mobile phones. NFC does not require complex setup procedures and offers a simplified version of Bluetooth functionality. NFC data transfer speeds are available at 106kb/s, 212kb/s, and 424kb/s, significantly lower than Bluetooth V2.1 (2.1Mb/s).
IV. IEEE 802.11ah
Wireless local area network (WLAN) standards are prefixed with IEEE 802.11, followed by one or two letters to distinguish their specific features. The Institute of Electrical and Electronics Engineers (IEEE) proposed the 802.11ah standard to meet the needs of seamless interconnection applications, enabling low-power, long-range wireless LAN connections, requiring the use of sub-1 GHz frequency bands. This effectively improves upon the shortcomings of WiFi signals being easily obstructed by buildings, thus affecting transmission distance and coverage.
The first wireless LAN standard developed by IEEE was 802.11, which was also the first internationally recognized protocol in the wireless LAN field. It was primarily used to solve the wireless access problems for users and user terminals in campus networks and office LANs, with services mainly limited to data access and a maximum speed of only 2Mb/s. Because 802.11 could not meet people's needs in terms of speed and transmission distance, the JEEE group subsequently introduced many new standards, such as 802.11a and 802.11b, whose main technical differences lay in the MAC sublayer and physical layer.
Since the release of the first-generation 802.11 standard in 1997, WiFi has experienced tremendous development and widespread adoption. Today, WiFi is the preferred way for users to access the internet. Throughout the development of WiFi systems, each generation of the 802.11 standard has significantly improved speeds. For example, 802.11ac can reach speeds of 1Gb/s. The 802.11ac standard operates in the 5GHz band, offering faster speeds compared to the 2.4GHz 802.11n or 802.11g. The 802.11ah standard, under ideal conditions, can achieve a transmission distance of up to 1km, achieving a wider coverage area. 802.11ah uses the 900MHz band, resulting in significantly lower operating speeds, reaching only between 150kb/s and 18Mb/s. This is suitable for low-power devices with short-duration data transmission and is a viable wireless communication technology for the Internet of Things (IoT).
1. IEEE 802.11 Channel Allocation
IEEE 802.11 is divided into the 2.4 GHz and 5 GHz carrier frequency bands, and further divided into multiple sub-channels.
1) 2.4GHz band
The IEEE 802.11 working group and the national standard GB15629.1102 jointly stipulate that the 2.4 GHz operating frequency band is 2.4~2.4835 GHz, with 12 sub-channels and a bandwidth of 22 MHz. The specific channels vary by country: channels 1-11 are available for the United States; channels 1-13 are available for EU countries; and channels 1-13 are available for China, as shown in Figure 1.
Communication technology is the foundation of the Internet of Things (IoT), and the interconnection of everything relies on the support of various communication technologies. If we compare the IoT to an information logistics system, then communication technologies are the different modes of transportation.
Common communication technologies can be divided into wired communication technologies and wireless communication technologies. Refer to "Overview of Common IoT Communication Technologies". Wired and wireless technologies are further subdivided into many different standards based on the application scenarios and technical characteristics.
I. Wired Communication Technology
Ethernet Introduction
Ethernet architecture consists of two main layers:
PHY—the physical layer—primarily converts digital signals into analog signals for transmission over supported media. It defines the electrical signals, symbols, line states and clock requirements, data encoding, and connectors for data transmission.
MAC—Media Access Control—corresponds to the data link layer in the OSI 7-layer model. The data link layer consists of two parts: MAC (Media Access Control) and LLC (Logical Link Control). The MAC is responsible for sending and receiving data, synchronizing data transmission, identifying errors, and controlling the flow of data.
