• First of all, there are slight differences between laboratory data and actual data. In practice, due to insufficient base stations, poor signal coverage, and many 5G coverage holes, the network speed may not reach the highest peak. Under normal circumstances, the 4G upload speed is stable at 20-40Mbps, and the 5G upload speed is stable at 100Mbps (the fewer people, the faster the speed is closer to the base station.)
• Using a high-performance host (connected to the same 5G module, under the same environment, the Internet speed of a laptop can reach several times that of a Raspberry Pi, and the host used in mainstream brand 5G smartphones is also quite good, the Internet speed won't be too bad), using high-gain antennas and trying to spread the antennas as far apart as possible in an inverted V shape (the internal antenna layout of the phone has a comparative advantage), can also effectively improve the bottleneck of Internet speed
• For different module frequency bands, communication performance and other parameters also vary. If you are pursuing the ultimate Internet speed, it is recommended to use high-performance Qualcomm modules (with a higher ceiling for high-performance mobile Internet speed), such as the SIM8262, RM520N, and other modules
• Ensure sufficient power supply; sometimes, to ensure stable Internet access, the module may appropriately reduce speed, especially when power supply is insufficient, so please provide sufficient power to the device
• Base stations are dense, not congested, resulting in smoother networks; using SIM cards and high-quality packages by operators with more base stations and wider coverage (under the same conditions, higher fees correspond to higher speed limits)
• Please replace SIM cards from multiple operators for comparative testing. Different operators support different 5G frequency bands, and the lack of frequency bands prevents registration to 5G. Even with the same bands, bandwidth differences can also lead to varying network speeds
• Speed tests on different nodes also vary, which can be felt when testing speed on a regular phone or computer. Therefore, you can switch to several different nodes or speed test servers for comparative testing and calculate the average network speed
• Actually, fast Internet speed isn't the only pursuit; stability is what matters. Therefore, you can switch different modules and SIM cards from different operators for comparison testing to quickly find a more suitable solution

• The x86 computer processor has higher efficiency in processing 5G data packets, while the Raspberry Pi's ARM architecture is prone to overload during encryption/protocol stack operations, resulting in reduced throughput.
• Computers typically use PCIe 3.0/4.0 to directly connect 5G modules, providing sufficient bandwidth, while Raspberry Pi often uses USB 3.0 to connect to actual module, resulting in a bottleneck.

• Uneven distribution of spectrum resources: The network design optimization is biased towards the downlink, and most of the traffic demand is concentrated on receiving content; There are few uplink spectrum resources;
• Antenna transmission power limit: The uplink signal of the 5G module needs to be transmitted through the antenna of the device. SIM8202, for example, can be received by four antennas, and only two antennas can transmit data. The lower transmission power leads to a slower uplink speed.
• Network design priority level: The design of 5G networks usually gives priority to download traffic requirements. Most users' Internet usage behavior is mainly focused on receiving content, such as watching videos, browsing the Web, downloading files, etc.

• It may be switched to SIM card 2, please use the following command to switch to SIM card 1:

 AT+SMSIMCFG=1,1

• To switch to SIM card 2, use the following command: (Some HATs have SIM2)

 AT+SMSIMCFG=1,2

If it still does not work, consider that the flight mode is on, and turn off the flight mode with the following command:

 AT+CFUN=1

• The 5G frequency bands supported by the brand phone may be much more than the module, and the 5G frequency bands supported by the SIM card cover the phone but not the 5G module, so the phone may register to 5G, but the module may not;

Different operators' base stations support different 5G frequency bands. Please compare the Internet speed by testing the SIM cards of several frequency bands that cover the 5G module frequency bands.

• The mobile baseband chip (SOC) is more advanced, with faster data processing speeds, and is more powerful than the Raspberry Pi;

Please replace the 5G module with a computer host or other high-performance SOC for comparative testing

• The mobile cellular baseband is more advanced, and the baseband of brand smartphones can reach X75, while the baseband of SIM82XX is X55 or X62;

Replacing with a high-performance module can effectively improve Internet speed. If you aim for the ultimate Internet speed, it is recommended to use high-performance Qualcomm modules, such as SIM8262, RM520N, and other modules

• The mobile phone antenna design is stronger, and the device antenna may have weak signal reception;

Replace with a higher gain external antenna to enhance signal reception capability

• The phone may be deeply adapted to the operator, resulting in better network optimization, support for higher-order modulation, intelligent background connection management, and the device may maintain inefficient links while supporting higher-order modulation, with the device possibly limiting modulation methods; while the 5G module is still continuously optimizing and upgrading, it is believed that in the near future, network speeds can keep pace with ordinary phones
• Most smartphones' internal main controllers (SOC) and modules are not connected via USB, but rather use faster high-performance interfaces like PCIE;

Consider using a motherboard with PCIE direct connection, PCIE to network port, etc., to achieve the optimal network speed

In this case, the network connection may not be successful. Follow the steps below to troubleshoot:
1. First, check the hardware:

• Check whether the connected SIM card can communicate and surf the Internet normally on mobile phones and other devices. It is recommended to test with SIM cards from several different operators to rule out issues related to SIM card frequency bands;
• Check whether the antenna is connected properly;
• Check that the NET light is flashing, and it is always on, indicating that it is not registered to the network.

2. After confirming that the hardware is OK, you can use the following command (AT LOG) to further confirm the network situation:

*Open ttyUSB2 through minicom:
 ls /dev/ttyUSB*
 sudo apt-get install minicom
 sudo minicom -D /dev/ttyUSB2
*Check the firmware version information:
AT+SIMCOMATI
*Check if the sim card is in good contact:
AT+CPIN?
*Turn the radio on (turn off airplane mode):
AT+CFUN=1
*Check that the network mode is set to auto-seek:
AT+CNMP=2
*Check the signal quality of the current environment:
AT+CSQ
*Check if the registration to the network is successful:
AT+CGREG?
*Check internet connection:
AT+CPSI?
*Check if the APN corresponds to the operator of the SIM card:
AT+CGDCONT?
*Check operator access:
AT+COPS?

• It is recommended to replace the SIM card of different operators to test: different operators support different 5G frequency bands, change the card at the same time can also solve other problems with the card;
• There is no configuration of APN. APN determines the way to enter the network. It is the agent of the operator and the cellular module. Sometimes APN can be obtained automatically, but many times it needs to be obtained manually. You can set it through the following command:

AT+CGDCONT=1,"IP","APN"   //The APN of different operators is different. Here the APN is changed to that of the corresponding operator, for example:
China Mobile APN: CMNET; China Unicom APN: 3GNET; China Telecom APN: CTNET

You can check the APNS of major operators on the following website: APN query website

• You can switch to a different neighborhood or go to another district to test: Different areas cover different operators' networks, leading to different 5G frequency bands in different places.
• To ensure the module registers on the power-efficient LTE 4G network, it must have adequate power supply; insufficient power can also cause the module to register on the LTE 4G network.
• Although it shows 4G LTE network, 5G speed is already available, which do not affect usage, and you can also send the following command:

AT+CNMp=109

• It may be that the antenna's band does not cover the band of the operators you are using, please change to a full band high gain antenna suitable for your local area to test, and connect all antennas, all antennas are useful, otherwise it may also cause network problems;

All antennas are connected, and all antennas are useful; otherwise, it may also cause network issues;

• If you are using an IoT card, it is recommended to switch to a regular mobile SIM card (one that can make calls and send messages) for testing. Some pure data cards or IoT cards may be restricted on other devices or after switching devices and cannot register to the 5G network. You can also check the status of the card with the IoT card provider.
• The SIM card bands of 5G operators should cover the bands of SIM820X; sometimes, when querying 4G networks, speeds have reached 5G, and direct speed testing can confirm whether 5G speeds are available.
• Plug the SIM card into the phone to test if it can register to the 5G network. If the phone cannot register, it means the SIM card has not been activated for a 5G data package, or there is insufficient balance, etc.

• Confirm if there is 5G network coverage in the test environment and what frequency band it is registered to (whether the registered frequency band is one of the bands supported by the 5G module).
  • Android phones can be installed with 5G phones to install Cellular-Z (available in major App stores) to view detailed network information:

• • iPhone can get band information by following these steps:
    • Turn on your phone dialer, enter *3001#12345#*, and tap the dial button
    • In the pop-up page, find and click on "Serving Cell Info", then find and click on "Freg Band Indicato".
    • You can find out by making an inquiry according to the form sent by the operator

AT+CSYSSEL="nr5g_band",41:78

• It is recommended to use the more convenient SIM820X RNDIS Dial Up.
• You can flash the latest Raspberry Pi Raspbian system and reconfigure the NDIS dial-up.

• You can use the following commands to check if the SIM820X and the Raspberry Pi are well connected. If the connection is OK, you can see Qualcomm device and ttyUSB0-USB4:

lsusb
ls /dev

• 1) It is recommended to replace the SIM card of different operators to test: different operators support different 5G frequency bands, change the card at the same time can also solve other problems with the card; If you are using an IoT card, it is recommended to switch to a regular mobile SIM card (one that can make calls and send messages) for testing. Some pure data cards or IoT cards may be restricted on other devices or after switching devices and cannot register to the 5G network. You can also check the status of the card with the IoT card provider.

• 2) Please configure the APN correctly. There is no configuration of APN. APN determines the way to enter the network. It is the agent of the operator and the cellular module. Sometimes APN can be obtained automatically, but many times it needs to be obtained manually. You can set it through the following command:

AT+CGDCONT=1,"IP","Your_APN"   //The APN of different operators is different. Here the APN is changed to that of the corresponding operator.
For example: China Mobile APN: CMNET; China Unicom APN: 3GNET; China Telecom APN: CTNET

• 3) It may be that the antenna's band does not cover the band of the operators you are using, please change to a full band high gain antenna suitable for your local area to test, and connect all antennas, all antennas are useful, otherwise it may also cause network problems;

• 4) If it still doesn't work, please refer to the following steps to print the network AT log and give the log to our service support team for analysis.

*Check the firmware version information:
AT+SIMCOMATI
*Check if the sim card is in good contact:
AT+CPIN?
*Turn the radio on (turn off airplane mode):
AT+CFUN=1
*Check that the network mode is set to auto-seek:
AT+CNMP=2
*Check the signal quality of the current environment:
AT+CSQ
*Check if the registration to the network is successful:
AT+CGREG?
*Check internet connection:
AT+CPSI?
*Check if the APN corresponds to the operator of the SIM card:
AT+CGDCONT?
*Check operator access:
AT+COPS?

• Open ttyUSB2 through minicom:

ls /dev/ttyUSB*
sudo apt-get install minicom
sudo minicom -D /dev/ttyUSB2

• Plug the GPS antenna into the GNSS antenna socket (SIM8200EA is ANT5; SIM8202G is ANT2), and place the receiver in the open air (note that it cannot be tested in rainy weather). It takes about 1 minute to receive the positioning signal after power-on.

• M2 module needs to use a passive antenna to obtain positioning information. If you do not have a passive positioning antenna, a 5G antenna can also be used. Replace the 5G antenna and place the module outdoors for positioning (the 5G antenna does not come with an extension cable):

USB, when running sudo ./install on the Raspberry Pi, it will load the USB driver, and we will connect and communicate via the 3B/4B USB connector; following the tutorial on Windows will also load the USB driver, and when there is no USB driver, it will be displayed as an unknown device.

It is not occupied by default.

Ensure your system kernel is 5.4 or higher. Do not use sudo update to upgrade to the latest version on Raspberry Pi, as this will upgrade the kernel version to a level higher than the current firmware, causing it to be unrecognizable.

sudo ./simcom-cm -i wwan0
sudo ./simcom-cm -i wwan1

You can use the following command to save the SMS to the module memory:

   AT+CPMS="MT"   

You can use the following command to enable VOLTE function:

 at+voltesetting=1
 at+cnv=/nv/item_files/modem/mmode/ue_usage_setting,1,01,1

You can use the following command to disable VOLTE function:

 at+voltesetting=0
 at+cnv=/nv/item_files/modem/mmode/ue_usage_setting,0,01,1

Please refer to the following figure for installation:

• ANT 0 and 1 functions can replace each other, and 2 and 3 functions can replace each other. Usually, if one antenna is missing, it does not affect the basic functions.
• If the copper foil has also come off, it usually cannot be repaired.
• When removing it, please wiggle it gently from side to side and pull it out evenly, avoiding forceful pulling.
• The IPEX4 generation connectors are relatively fragile, so please handle them with extra care.

• Yes, it needs to be connected with a USB cable. After connecting with a pin header, the USB adapter and USB socket are not fully aligned, and the USB cable is used for the connection

You can use the following command to check if there is a Qualcomm device. If the COM driver has already been loaded (which is usually included in Raspberry Pi systems), a series of ttyUSB * will also appear:

lsusb
ls /dev/ttyUSB*

After the roller fan works for a long time, the lubricating oil may evaporate, resulting in increased noise, which is the general nature of the roller fan, not the fan fault:

• We do not guarantee that the modules that have not been verified (including disassembled modules such as FM350X) will be supported, but the following modules have been verified and supported:

Fibocom: FM650-CN FM160-EAU	
SIMCOM: SIM8202G-M2 SIM8262E-M2 SIM8262A-M2
Quectel (USB AA module): RM500U-CNV RM500Q-GL/RM502Q-AE RM520N-GL RM530N-GL

• Quectel module special instructions: This is a USB3.0 protocol module, you need to use Quectel AA modules that support USB, not the AP silk screen module (RM520 AP ~~) that does not support the PCIE protocol. It is not recommended to use modules bought from the second-hand market, as we do not provide support for them. It is suggested to choose modules that we have verified and listed, which is more guaranteed. As shown in the image, the RM520_AA module is supported:

• If you need to use M.2 TO 4G/5G HAT for other 4G/5G modules, you can refer to the M.2 connection diagram in the figure below, check if there is a pin conflict, and then connect it for testing:
  

• USB 3.2 Gen1 5G DONGLE and USB TO M.2 B KEY kit does not include the 5G module, which must be purchased separately; if used with other modules, pin compatibility must be confirmed, and the actual measurement shall prevail.

For different work states, power consumption varies. With 5V power supply, the current generally ranges from 0.5 to 2.5A after successful networking, with an average of about 1.2A (this is for reference; the actual value depends on the network environment and networking work state).

• Yes, it's like two mobile phones using 5G cellular networks that can interconnect through the operator's base stations
• The Raspberry Pi A and B are respectively registered to the network via the RM500U-CN 5G HAT and SIM8262E-M2 5G HAT cellular modules, and after going online (at this point, two phones are born), they can communicate via TCP, MQTT, email, or instant messaging tools, etc., to achieve interconnection on the 5G network.
• However, cellular modules cannot communicate point-to-point, and even at zero distance, the cellular network still needs to communicate with the operator's base station, which also incurs data costs; If point-to-point communication is required, Bluetooth, WiFi, or Lora can be used to bypass communication with the operator's base station