I. What is SIM CPE?

II. Advantages of SIM CPE

1. Extremely simple installation and deployment: Insert card, power up, auto-connect—no professional personnel required, reducing installation time by 90%.
2. Stable and reliable connection: Compared to ordinary WiFi routers, industrial-grade SIM CPE uses high-quality components with Mean Time Between Failures (MTBF) typically exceeding 100,000 hours.
3. Extensive coverage: Deployable wherever there’s mobile signal, especially suitable for remote area monitoring systems.
4. Dual SIM redundancy design: Most SIM CPEs support dual SIM backup, automatically switching to the backup SIM when the primary one encounters issues, ensuring business continuity.
5. VPN encryption support: Built-in various VPN protocols for direct encrypted data transmission, meeting security-sensitive scenario requirements.

III. Key Indicators When Purchasing SIM CPE

1. Network support: Whether it supports 5G/4G full-network compatibility, RedCap, and other new technologies
2. Interface richness: Industrial applications often need RS232/RS485 and other serial ports
3. Operating temperature: Ordinary devices 0-40°C, industrial grade typically -35-75°C
4. Power supply method: Whether it supports wide voltage input (e.g., 9-36V DC)
5. Management features: Whether it supports remote management platforms
6. Protection rating: IP30 or above to handle harsh environments

IV. Actual Testing Case Sharing

V. Technical Details and Configuration Optimization of SIM CPE

5.1 Detailed Parameters for SR820 5G CPE

• Hardware configuration: 512MB RAM, 4GB EMMC flash storage
• Network support: 5G NR/RedCap networks, supporting SA/NSA dual-mode
• Rich interfaces: 4 gigabit LAN ports (1 can be repurposed as WAN), 1 RS232, 1 RS485
• Dual SIM design: Supports 2 physical SIM card slots + eSIM
• Operating temperature: -35°C to +75°C, far exceeding ordinary CPE
• Power control: Only 300-350mA@12V in standby, 400-600mA@12V when running
• Protection rating: IP30 metal casing, sturdy and durable

5.2 Network Optimization Tips

1. Frequency Band Locking Technology The SR820 supports 5G frequency band locking, which can lock onto the band with the best signal in complex signal areas:

# Example: Lock n41/n78 bands
at+qnwlock="common/4g",0
at+qnwlock="common/5g",0,"n41 n78"

2. Antenna Position Optimization AT commands can be used to check signal quality in different directions:

at+qeng="servingcell"

When RSRP value is greater than -105dbm, it indicates good signal. My suggestion is: first use a mobile phone to test and find the optimal position, then fix the antenna.

3. APN Setting Tips Public network SIM cards and private network SIM cards have different APN settings, for example:

# Public network card
at+cgdcont=1,"IP","cmnet"

# Private network card (using a power industry private network as an example)
at+cgdcont=1,"IP","dl.myapn.com"

5.3 Advanced Configuration Solutions

1. Dual Link Redundancy Solution The SR820 supports wired+5G dual link redundancy, configuration method:

# Enable link detection
link_detection enable

# Set primary and backup links
primary_link eth0
backup_link wwan0

# Set detection targets
detection_target 114.114.114.114 8.8.8.8

# Set switching threshold
failover_threshold 5

2. Industrial Protocol Transparent Transmission Configuration The SR820 has built-in DTU functionality, and its RS485 interface can directly collect PLC data:

# Enable Modbus RTU to TCP bridge
dtu_mode modbus_bridge
serial_params 9600,8,1,none
server_addr 192.168.1.100
server_port 502

3. VPN Tunnel Configuration Most of our industrial clients use IPsec VPN to ensure data security:

# IPsec configuration example
ipsec_type esp
ipsec_auth sha256
ipsec_encrypt aes256
ipsec_mode tunnel
local_subnet 192.168.1.0/24
remote_subnet 10.0.0.0/24
psk_key "YourStrongPreSharedKey"

5.4 Common Troubleshooting

1. Strong signal but slow speed: Check if connected to the correct network mode (NSA/SA), performance is better in SA mode
2. Frequent disconnections: Check if the keepalive feature is enabled, recommend setting a 30-second heartbeat
3. VPN connection failure: Check if NAT-T traversal option is enabled in NAT environment
4. Device overheating: In industrial scenarios, recommend adding heatsinks and setting automatic temperature-controlled frequency reduction

Conclusion