Cellular Gateway vs. Cellular Modem

Cellular gateway and cellular modem are the most common equipment in the industrial cellular machine-to-machine (M2M) network. Follwoing will explain the key differences between these two devices, and help you choos the most appropriate for your applications.

 

Features

Cellular Modem

Cellular Gateway

How does it work?

Dail-in/out to other modem

Serial/Ethernet to IP

Knowledge requirement

AT Command

TCP/IP

Connection

Dial-in/out

Always on, pause when no data

Operation Types

Dial-in/out

Virtual Com, TCP Server/Client, UDP

Bandwidth

Low (up to 14.4kbps)

High (up to 300 mbps for 4G LTE)

Network bridging

No (except PPP)

Yes

Local intelligence

No

Yes

Charge

Per minute (high)

Per data packet (low)

Cellular Modems

Cellular modems are the earlier devices of M2M connectivity. Their uses are very limited due to cellular providers upgrading their networks and removing the older generations of cellular data. They are beneficial for users only transmitting serial data and regions with only 2G cellular networking available. (As April 1st, AT&T is the only provider activate 2G service).

 

For a cellular modem and/or PSTN modem to work, they need to be used in pairs. One modem would reside at the end device and one on the server side. For a connection to be established, either modem must dial out to establish a connection (for example AOL internet access). Once a link is established speeds are limited to 14.4 Kbps. The data can only be transmitted and received in serial format so your end device must be sending and receiving cellular data.

 

M2M Cellular Modem

 

In addition to the limitations listed, another device needs to interface between your end device and your cellular modem. Typically a computer or a PLC (Programmable Logic Controller) can be found in between your two devices. The cellular modem is unable to perform the dial out process and requires the PC/PLC to issue the proper commands and dial to the correct number. Users are required to have a good knowledge of AT commands to program the device.

 

Data is measured by the time of the connection so a large amount of data being transmitted may be very costly. Since there is a dial out process it can only serve one user at a time. If other users are trying to reach the end device they would be locked out.

 

 
 

Cellular Gateway

 

Cellular gateways are the newest devices of M2M networking and are readily found on the market. They offer the latest cellular technologies offering higher speeds and bandwidth. Gateways are usually more robust and offer more options than cellular modems. Once the Gateway establishes a connection with the cellular network it is “always on”. Data can be sent or received on demand without delay. In addition, a PC/PLC is no longer required to issue AT commands for a dial out. The gateway is capable of establishing and maintaining its own connection.

 

M2M Cellular Gateway

 

Setup is also much easier with web interfaces embedded within the device. The interface provides the user information and status of the device as well as the ability to program and configure the serial, network, security and cellular parameters. Customers no longer need AT programming knowledge and can be setup by anyone with its friendly user interface.

 

Cellular gateways are not limited to only transmitting serial data and can only transmit any data that can be packetized using TCP/IP. Special software is only necessary on the server side that can convert the packetized serial data back into serial. Any device that communicates via TCP/IP can connect with the cellular gateway to retrieve and send data. TCP/IP standards also allow devices to connect and establish multiple connections which cannot be done with a cellular modem.

 

 

Here are the industrial cellular gateway with above mentioned functions.

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