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Overview

The ubiquity of cellular networks gives the perception that it is easy to implement reliable M2M connectivity anywhere.

The complexity and dynamics of cellular networks can however can make M2M cellular data connectivity in fringe and remote areas troublesome; and insuring operation of cellular devices in new areas problematic.

Critical M2M cellular links may fail at unforeseen times due to network changes;  equipment degradation; tree and foliage growth; and extreme weather conditions. For systems relying on critical M2M links intermittent operation may not be unacceptable or cause systems shut-downs. Conversely when you have problems with voice calls you may move to a better coverage area or retry calls.

We wanted to point out some of the factors in optimizing cellular data communication based on our years of experience with cellular data networks for SCADA and M2M applications.

Antenna Selection

Proper Cellular antenna selection is important. You want to make sure that your selected antenna supports the correct bands and beams pattern for the application. Sometimes cellular equipment tested in area with good cellular signal levels masks out the fact that cellular antenna is not optimal.

Omni direction antenna are used when you are unsure of the tower direction or your application is mobile. Direction antenna’s – YAGI are used in fringe area when specific directional beam pattern is required. Ensure that the antenna covers proper cellular RF band.  Multi-band antenna may be preferred for many applications.  Antenna with single band may become problematic over time if there are network changes and operation changes to a different band is no longer supported. This was the case for single band YAGI used to optimize 3G operation and the local tower was updated to 4G operation.

We have seen the totally incorrect antenna utilized.  To prevent these types of problems make sure to check the antenna specifications and model numbers. Also, one can have multiple alternative antenna for comparisons.

Antenna Height

Antenna height is important to clear obstructions.  A direct path ensures reliable signals. Antenna without line of site path may rely on reflections. Reflection from equjpment and vehicles can cause intermittent communications due to multi-path conditions. Antenna height can be achieved by the use of antenna masts or antenna towers. Telescopic masts can be used for portable applications.

Antenna Cabling

Elevated antenna or remote antenna may be required to clear obstructions or get out of a building. Ensure that cable has low losses and is properly terminated. Frequently there are problems improperly installed cable connectors or cables / connectors getting water ingress.

Amplifiers

Cellular amplifiers may assist when for long antenna cables are used or the tower is a long way from the site. Make sure the cellular amplifiers cover the appropriate bands.

Carriers and Provisioning

Make sure that the carrier that you are planning to use has good coverage in the area. Sometimes the carrier are using may not be available in the area.  Sometimes there is need to have SIM card from another carrier to test alternative carrier. Alternatively one may have a cellular phone operating on other to test alternative carrier coverage.  Note some cellular providers require the device to be approved and registered on network to operate. If this is the case, unless the device is registered having a SIM is not suffice.

Modem Settings

Many times cellular data communication problems is caused by improper modem configuration including the wrong APN, port numbers, or socket types configured.

Testing

Testing can help determine optimal cellular data device operation.  Use of the RSSI and SNR diagnostics in the cellular devices can be invaluable. Antenna and cable analyzers can also be used to verify the integrity of the antenna and antenna cabling.

3G network Sunsetting

Make sure that there is coverage for modem/services that you are using. Your 3G modem will not work if you are in area that no longer has 3G coverage.

Private Data Networks & VPN

Use of Private data networks can prevent denial of service attacks and data overages.

Roaming

Make sure that cellular data plan you have for your application is appropriate. If you are required to operate or move your equipment between countries, insure it has roaming plan otherwise you may have encounter extremely costly roaming charges.

Managed Services

Managed services are available from carriers, MVNO, or providers to help alleviate provisioning issues. Services such as  management portals are available to monitor and control data usage of data devices and prevent data costly overruns.

Experiences Field Services

The use of RF / cellular data expertise may be needed to expedite cellular coverage and cellular data problem resolution.

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