| Where can I get the specifications for short-range communication devices (SRD)? |
| Abstract: Although the use of short-range communication devices (SRD) does not require a license, each country has different laws and regulations for these devices. These devices are under the jurisdiction of different regulatory agencies. This article aims to give an overview of these regulations and tell the reader how to find this information on the Internet. This article also includes an overview of FCC Part 15 and ETSI EN 300-220. Although the use of short-range (SRD) devices does not require a license, each country has different laws and regulations for these devices. These devices are under the jurisdiction of different regulatory agencies. This article aims to give an overview of these regulations and tell the reader how to find this information on the Internet. In the United States, the Federal Communications Commission (FCC) is responsible for managing all radio frequency (RF) equipment. Any product that performs unlicensed work must comply with Article 47, Part 15 of the Federal Regulations. Part 15 can be obtained from the following address: http: //. [15.231 covers the 260MHz to 470MHz band, and 15.249 covers the 902MHz to 928MHz band. The following is a summary of 15.231 and 15.249. Section 15.231 According to section 15.231 (Sections a to d), a device is allowed to transmit: control or command signal ID codeword wireless control signal in case of emergency However, the device is not allowed to: transmit voice or video control toys transmit continuous data if the transmitter To be manually activated, transmission must stop within 5 seconds after the switch is released. If the transmission is automatic, then it must stop within 5 seconds of activation. Periodic transmission at regular predetermined intervals is not allowed unless the transmission period of each transmitter does not exceed 1 second per hour, such as periodic query or monitoring of transmitters in safety applications. The maximum field strength of the fundamental frequency (260MHz to 470MHz) increases linearly from 3750µV / m to 12500µV / m. The distance targeted by these limits is 3 meters. The clutter signal will be attenuated to 20dB below the fundamental frequency signal. The bandwidth cannot exceed 0.25% of the center frequency. The bandwidth is determined by the modulated carrier attenuation at 20dB. The device can be used for any type of work (segment e), as long as the output power is halved, the maximum transmission time is limited to 1 second and the interval between transmissions is 30 times the transmission duration (but not less than 10 seconds). All other provisions in paragraphs b to d are still valid. Section 15.249 Equipment operating in the 902MHz to 928MHz frequency band must comply with 15.249, and the allowed field strength is up to 50mV / m (distance 3m). Harmonics are limited to 500µV / m, while other clutter signals are limited to 50dBc. There are no restrictions on the content and duration of the launch. In Europe, the European Post and Telecommunications Authority (CEPT) is responsible for managing frequency band allocation and output power. The European Radio Administration (ERO) is the permanent office of the CEPT Telecommunications Commission (ECC) and is responsible for issuing the recommendations in ERC REC 70-03. The following is an overview of the 433MHz and 868MHz bands. The complete documentation can be obtained from the following address: http: //.
The European Telecommunications Standards Institute (ETSI) is responsible for the development of testing and verification standards. The standards for SRD equipment are in EN 300 220: http://pda.etsi.org/pda/home.asp?wki_id=9343 (EN 300 220-1) http://pda.etsi.org/pda/home.asp?wki_id=8804 (EN 300 220-2) http://pda.etsi.org/pda/home.asp?wki_id=6474 (EN 300 220-3) The following is a brief summary: Frequency error (Section 8.1) Frequency error or drift should not exceed the value under nominal or extreme conditions.
Note: (b) = fixed base station; (m) = mobile base station; (p) = portable base station carrier power (feed) (Section 8.2) applies to devices with fixed external antenna connectors. The carrier output power should not exceed the given power level.
The measurement of clutter signal emission (Section 8.7) shall be carried out without modulation. For transmitters operating below 470MHz, measurements must be made from 9kHz to 4GHz. For devices operating above 470MHz, the upper frequency limit is 12.75GHz. The power of any clutter emission, conducted or radiated, shall not exceed the following values:
Receiver clutter radiation (Section 9.4) Receiver clutter radiation comes from equipment and antennas. For receivers operating below 470MHz, measurements must be made from 9kHz to 4GHz. For devices operating above 470MHz, the upper frequency limit is 12.75GHz. The power of any clutter emission, conduction or radiation shall not exceed the following values:
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First, Wireless Router
So what is a wireless router?
Wireless router, according to the definition of Baidu Encyclopedia: Wireless router is used for users to access the Internet, with wireless coverage of the router.
A wireless router can be thought of as a repeater that forwards the broadband network signal from the wall of your home through an antenna to nearby wireless network devices (laptops, Wifi-enabled phones, tablets, and all Wifi-enabled devices).
The popular wireless routers in the market generally support four access methods: dedicated xdsl/cable, dynamic xdsl, pptp, and generally can only support 15 to 20 devices online at the same time. It also has some other network management functions, such as dhcp service, nat firewall, mac address filtering, dynamic domain name and so on. The signal range of the general wireless router is 50 meters radius, and the signal range of some wireless routers has reached 300 meters radius.
The name of wireless router can be separated out of two keywords: wireless and routing.
Understand the technical principle behind these two words, you understand the wireless router.
Wireless is also what we often call Wi-Fi. Wireless routers can convert home broadband from wired to wireless signals, and all devices can happily surf the Internet as long as they connect to their own Wi-Fi. In addition, these devices also form a wireless local area network, where local data is exchanged at high speed and is not limited by the bandwidth of home broadband.
For example, many people have smart speakers in their homes that can be used to control various smart appliances. When you say small X small X, turn on the TV, the speaker actually finds the TV through the LAN and sends instructions, and does not need to connect to the Internet; And if you let it broadcast news, you have to get data through the Internet.
The Local Area Network we talked about earlier, also known as the Intranet, is represented by the Local Area Network (LAN) on the router, so the Wi-Fi signal is also called WLAN(Wireless LAN); The Internet we want to access, also known as the extranet, is represented on the router by the WAN(Wide Area Network).
On the Intranet, the IP address of each device is different, which is called a private address. All devices on the Internet share the same public address, which is assigned by broadband operators such as China Telecom Unicom.
The router is the bridge between the Intranet and the external network. The above mentioned IP address translation, packet forwarding, is the router routing function. In other words, the router is the hub of the home network, and the data of all the devices must be forwarded through it to access each other or reach the external network, which means that one husband is the key and ten thousand men are not open, so the comprehensive router is also called "home gateway".
Second, the demand for wireless routers
I do not know if there is a sudden WIFI break when you play games at home, and a stable router is crucial at this time. However, it is important to note that your WIFI frequently dropped may not be a problem with the router, it may also be a problem with the carrier network. (Router means I don't back this pot)
In fact, for most people, there are two basic requirements for wireless routers
Stable and do not drop
Fast Internet and easy setup
Some people will have some advanced needs:
There are some features, USB interface, can be external U disk or hard disk, can achieve simple nas functions, QOS, etc., to advertising and so on
Mesh networking, when the house area is large, multiple routers can be used for Mesh networking
How to choose a wireless router
The wireless router market is in the transition stage from WiFi 5 to WiFi 6, if you want to buy the first choice is definitely WiFi 6 wireless router, which is the future trend.
The speed of WiFi 6 is nearly 40% higher than the previous generation 802.11ac, and the highest connection speed can even reach 9.6Gbps, while the highest speed of 802.11ac is only 6.93Gbp. More importantly, unlike 802.11ac, which only covers the 5GHz band, WiFi 6 covers 2.4GHz and 5GHz. Although the 5GHz band has less interference, it has weak wall penetration ability, and the 2.4GHz band has strong wall penetration ability, which takes into account each other.
So why choose a WIFI6 router?
Compared with the previous generation of 802.11ac WiFi 5, the maximum transmission rate of WiFi 6 in the 5Ghz band has been increased from 3.5Gbps to 9.6Gbps, and the theoretical speed has been increased by nearly 3 times. WiFi 6's 5Ghz single-stream 80Mhz bandwidth can reach theoretical speeds of up to 1201Mbps and 160Mhz bandwidth of up to 2402Mbps.
The band supports 2.4Ghz and 5Ghz.
In terms of modulation mode, WiFi6 supports 1024-QAM, which is higher than the 256-QAM of WiFi 5, and the data capacity is higher. Some high-end WiFi 6 routers support 4096-QAM.
WiFi6 supports MU-MIMO (multi-user multiple-input multiple-output) technology, and supports both upstream and downstream MU-MIMO, with a maximum support of 8T×8R MU-MIMO. The speed is greatly improved. High concurrency, WiFi6 5GHz band, terminal connections up to 128! 5 times that of WiFi5. Effectively solve the Internet needs of multi-person networking and smart home;
WiFi6 adopts OFDMA (orthogonal frequency division multiple access) technology. After using OFDM to parent the channel, the transmission technology of transmitting data is loaded on the subcarrier, allowing different users to share the same channel, allowing more devices to access, with shorter response time and lower delay.
Low latency, WiFi6 time delay can be as low as 10ms, compared to WiFi5 30ms delay, only 1/3. This performance refresh is extremely friendly to game lovers;
If WiFi6 (wireless router) devices need to be certified by the WiFi Alliance, they must use the WPA 3 security protocol, which is more secure.
The WiFi6 wireless router is backward compatible with WiFi5 and WiFi4 terminals.
Fourth, the misunderstanding of purchasing routers
Is the through-wall router really through-wall?
Mistake; The country has strict limits on the transmission power of the wireless router antenna, if you have a lot of rooms in your home, and there are many walls between them, even if you buy an expensive wireless router, you can not do one to cover all the room signals. If the signal is not good, you can consider multiple wireless router Mesh networking.
Does a wireless router have a stronger signal with more antennas?
More antennas just to match the X*X MIMO mode, the more antennas, the more channels, can only ensure that the network is more stable, the impact on the signal is little, the strength of the signal is only related to the wireless transmission power. The wireless transmission power of the country has a standard.
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Shenzhen MovingComm Technology Co., Ltd. , https://www.szmovingcomm.com