Internal vs external antennas

A common decision point that comes up in every IVMS (in-vehicle monitoring system) rollout is the choice to deploy either internal or external antennas.

I say antennas (plural) because there are two signals at a minimum that need to be established by the onboard IVMS unit. One is the GPS (location) signal and one is the communications (data) signal from the mobile carrier.

Smartrak supports multiple antenna options to facilitate different operational requirements. Suffice to say there is no right and wrong answer, so it usually takes quite some consideration to work through the best solution for each rollout.

Telco Communications Blackspots

A true mobile blackspot is just that. No coverage at all. It might sound obvious but no antenna will work in a true blackspot so there is no point spending additional funds and effort trying to chase a requirement that can't be met.

Telco Communications Grey Spots

Grey spots tend to occur in areas between blackspots and good coverage areas as the signal strength degrades from useable to un-useable. These areas while potentially unsuitable for regular phone calls or broadband use can be perfectly fine for an IVMS unit with an appropriate antenna.

Real-Time v Cached Data Transmission

The requirement for real-time connectivity can also be a contributor to antenna selection criteria. An IVMS solution installed for efficiency, utilization, and productivity purposes may not need to be connected all the time.  A fully offline capable solution (such as Smartrak) will transition into and out of coverage areas and is perfectly fine storing locally and forwarding events to the central server if and when it is able to communicate. The resulting fleet related insights are seamlessly be posted to the server so that all historic data can be viewed as per normal.

A very different requirement, however, is presented where the solution is a health and safety solution which is supporting worker safety in the field.  Being connected at all times is a mandatory requirement in this case.

Internal Vs External Mounting

External antennas do tend to have a more reliable and increased coverage footprint especially in grey service areas, even when comparing antennas (internal vs external) of equal specifications.  They tend to be mounted higher on the vehicle and enjoy a better line of sight to the available signal. Having said that they will also be more susceptible to damage in both minor and major accidents and pose additional risks to pedestrians when mounted on guards, quarter panels and front bars. When considering the safety aspect of being connected, internal antennas absolutely have merit in many situations.

High-gain external antennas can be used to attract a weaker signal and tend to be larger in size. They are used in an attempt to minimize the blackspot areas. In the end, however, if there is no signal (i.e. a true blackspot) then no antenna big enough is going to solve the problem. In scenarios where there is a known blackspot, it is more cost effective and reliable to keep the antennas to a reliable size / mounting location and deal with the blackspot with something like a satellite modem for communications only when the Telco signal is not available. A practice known as least cost routing keeps expensive satellite data charges to a minimum while providing connectivity in otherwise non-service areas.

Vehicle Types

Vehicle types are a huge consideration in this discussion also.

White Fleet

The typical white fleet which includes sedans and wagons rarely have appropriate mounting locations for external antennas unless bars and racks are also part of the vehicle specification. Further, there is usually driver / fleet manager desires to minimize external visual items and avoid external holes and fixtures.  Vehicle resale value always comes up as a topic to be conscious of with these installations.

The vast majority of white fleet do typically spend their time in telco coverage areas and subject to a very urban lifestyle such as low parking garages, drive through car washes, high levels of pedestrian traffic. All of these considerations typical lead to internal antenna recommendations. One other alternative which can help in edge cases is glass mounted adhesive external kits. These can be very handy in solving isolated problems of connectivity such as parking in undercover carparks in offices/apartment complex's.

Grey Fleet

The field service fleet including, Utes and light trucks often have plenty of mounting opportunities for external antennas if this is required, but it also needs to be considered with what gets loaded onto these vehicles as part of their normal operation in the field. Apart from the obvious consideration of avoiding damage by items being loaded onboard, the shielding effect of loads on roof bars can impact the performance of antennas and is not always obvious when diagnosing intermittent connectivity problems.

Yellow Fleet

Heavy, specialised plant is a category where external antenna fitment is usually the chosen approach. Often operating in poor coverage areas by the nature of their activity, and with less emotion when compared to the white fleet around holes in roofs and physical appearance considerations.

Have you thought about your antenna choice?

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