The Internet of Things (IoT) is extremely broad, and the operation of the Internet of Things requires wired and wireless communication. For the home, it requires wireless communication support such as Wi-Fi, Bluetooth, Z-Wave, or G.hn, HomePNA, etc. Wired communication support.
In the context of IoT's object connection, various items will have networking capabilities.
The industry uses ZigBee wireless communication, but the communication distance of each node of ZigBee is generally about tens of meters, up to 100 meters, 300 meters, and it is impossible to reach the communication distance of more than one kilometer.
If you want to transfer more than one kilometer, you can use the method of adding nodes. The several nodes in the process are only responsible for transferring the data. You do not need to sense and generate data. However, the disadvantage of this method is that it must be Build and maintain more nodes, even if there is no failure, you must replace the battery for a long time (unless the node has the ability to collect energy at the local level, but the current energy collection is mostly to extend battery life, not to completely replace the battery) .
If the path of data transmission is through rivers, mountains, cliffs, etc., it is difficult to build, and it is difficult to replace the battery. The alternative long-distance communication scheme may be the 2G and 3G communication used by existing mobile phones, but this type of There are two points involved in communication. One is the self-construction and self-use of industrial applications. It must also seek spectrum authorization. Some countries need to pay. The other is to directly cooperate with telecom operators (such as Chunghwa Telecom and Taiwan University) to use their base station to transmit. It must also be paid to the telecommunications industry.
Alternatively, Wi-Fi can also be adopted, but the Wi-Fi frequency band is high (2.4 GHz). To transmit transmission power over long distances, industrial applications do not require Wi-Fi transmission rates above Mbps, only kbps levels are required. Just fine.
Sub 1GHz wireless communication that can be transmitted remotely
Therefore, the industry began to develop wireless communications below the 1GHz band, such as 315MHz, 433MHz, 868MHz, 915MHz, etc., commonly known as Sub 1GHz, of which 868MHz, 915MHz and ZigBee the same frequency band, but 315MHz, 433MHz is the lower frequency, other also 300MHz, 387MHz, 470MHz, 779MHz, etc., different countries have different planning configurations.
The advantage of low frequency is that the transmission distance can be obtained at the same transmission power. If 315MHz is used, the difference is about 8 times compared with 2.4GHz of Wi-Fi. If Wi-Fi can reach 100 meters, 315MHz can reach 800 meters. The ruler (covering area is 64 times wider), plus Sub 1GHz does not require high transmission rate, and does not require complex modulation such as 16QAM and 64QAM. The result of simple modulation (such as ASK, FSK, etc.) is that the transmission distance is farther. , up to several kilometers.
As a result, more and more chip companies are investing in the development of Sub 1GHz, such as TI, STMicro, Infineon, etc., to meet the long-distance, low data rate requirements of the industry.
Sub 1GHz has advantages, but the disadvantage is that countries have not yet unified the available frequency bands. For example, 310MHz is available in Japan and 470MHz is available in the mainland. Therefore, when designing chips, the chip industry can support as many chips as possible in a single chip. All frequency bands may also support multiple low frequency bands (300, 400MHz) and the other support multiple high frequency bands (800, 900MHz). In addition, the transmission power must also comply with local regulations, such as European ETSI, US FCC and other certifications.
IEEE 802.11ah standard is under development
Also because Sub 1GHz has not yet been fully standardized, the IEEE has also begun to develop and develop its standards. This is IEEE 802.11ah. If there is no other delay, it is expected to be completed in March 2016. Currently, the relevant organizations involved in the establishment of this standard are Motorola Mobility (still confirmed to be Google or already Lenovo), NEC, CSR, ETRI, Intel, etc., and also include Broadcom, Huawei, Qualcomm, Marvell, Samsung.
Although still under development, some technical details can be learned from the draft version. For example, the channel bandwidth can be 1, 2, 4, 8, or 16 MHz, and the high transmission rate is required to be 8 or 16 MHz, which requires low transmission rate. 1, 2MHz, obviously different from today's mainstream Wi-Fi, mainstream Wi-Fi is to pursue high transmission rate, 11n era allows 40MHz (11g only 20MHz), 11ac to 80MHz, 11ac Wave to 80+80MHz or 160MHz. In addition, 11ah/Sub 1GHz only needs low transmission rate, but it is known to support at least 150kbps.
Once the 11ah standard is established, the development of the IoT Internet of Things will have more powerful reliance. In particular, the 2G and 3G of Km-level communication are also developing at a high transmission rate (4G, LTE, LTE-Hi, etc.), and more specialized Sub 1GHz technology standard for industrial applications, I hope this will come sooner.
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