LTE Cellular Carrier Certification Made Easy

Why is Cellular LTE Certification a Challenge?

Cellular carriers and PTCRB require that your product meet certain requirements for over the air performance. This performance is measure in terms of TRP (Total Radiated Power) and TIS (Total Isotropic Sensitivity).  In addition, LTE products require MIMO (Multiple Input Multiple Output) antennas which can act independently to overcome coverage challenges and take advantage of multipath opportunities.  So LTE requires an additional test – ECC (Envelope Correlation Coefficient) to be sure that your MIMO antennas are truly independent.

LTE bands occupy a variety of frequencies, which means that the characteristic elements of your antennas need to be sized and tuned accordingly.  For space constrained applications, integrating or designing and tuning your antennas requires proper RF design techniques and test equipment. If you skip ahead to product design before you have confirmed you have a viable RF design, your LTE product will fail carrier certification. And that leads to costly time and budget overruns and sometimes prevents a product launch altogether.

The BluFlux DFCC™ process is designed to help you be sure you will pass LTE carrier certification (and, correspondingly, PTCRB certification) the first time.  You’ll be sure to make the right RF design decisions in the right order so you launch on time and under budget.  Read on to learn more.

Choose the Product LTE Architecture and Form Factor for Your LTE Bands

When you’re choosing the product architecture and form factor for your cellular connected product, you’re making choices that will determine your RF performance.  RF performance can make or break your LTE certification.

The configuration of your microprocessor, external interfaces, cellular module, interconnections, and antennas can impact cellular performance.

The size of your PCB and enclosure will determine the efficiency and performance of your antennas. Smaller size antennas and ground planes usually correspond to worse performance at lower bands. Knowing how to size your antennas and ground plane is crucial.  Inadequately sized antennas or ground plane will reduce your cellular antennas’ efficiency in your LTE bands below the 40%-50% range that is typically required to pass TIS and TRP tests.

Proximity of noisy components or circuits in your product to your cellular (or other technology) RF front end can wreak havoc with your receive sensitivity.  Such “platform interference” is another common source of costly OTA certification TIS test failures.

BluFlux RF engineers and antenna designers can quickly guide you through your architectural and packaging tradeoffs for your chosen LTE Carriers’ bands and requirements.

Choose the Right Cellular Module

After you define your product architecture and packaging constraints, you can evaluate the cellular modules on your carriers’ approved lists.  For example, as of January 2016, there were 131 modules from 12 manufacturers on ATT’s approved module list. Choosing an approved module will save you hundreds of thousands of dollars in module certification costs.

But with over 100 options, which module is the best for your application?  Even cell modules with similar form factors can vary significantly in RF performance, cost and ease of interfacing. Transmit power and receive sensitivity can vary from module to module.  And if your product volumes are very low, you might be able to select a pre-certified modem instead of a module and thereby avoid a significant portion of the certification process.

All of these factors can impact LTE RF performance and your certification process, timing, and cost.

BluFlux can help you choose the right cellular module to meet your requirements and possibly save you significant time and money when launching your new LTE product.

Choose the Right MIMO Antennas and Integrate Them Correctly

If your product is like most other LTE-connected products on the market, there are probably OTS (off-the-shelf) antennas that can get you the performance you need for your cellular carriers and your customers.

In some cases, your application will present challenges that require custom antennas.  Antenna selection and design is complicated in small portable products, products worn on the body, and products with significant amounts of metal in their operating environments.

Whether you use OTS or custom antennas, the trick is not just finding (or designing) the right antennas but also knowing that they will perform as needed when they are installed in your particular product design.

The free-space efficiency of your antennas will be reduced to some degree when installed into your product and enclosure, depending on how they are installed and tuned. Cross-coupling between your antennas can compromise the individual antenna efficiency even further.

LTE products have multiple (MIMO) antennas to improve cellular perforamance.  If the efficiency of your main or diversity LTE antenna (or both) is compromised, that will affect both uplink and downlink performance, and could even hurt your product’s TRP or TIS test results at your carrier’s OTA testing lab.

The MIMO envelope correlation coefficient (ECC) of your LTE antennas will be a function of how they are positioned and oriented with respect to each other.  Poor MIMO ECC will compromise LTE performance, and can also cause a carrier certification failure.

If your product is worn on (or used in close proximity to) the human body, SAR (Specific Absorption Rate) testing will be highly dependent on your antennas’ radiation patterns and their exact location within your product.

Choose Your Cellular Antenna Before Starting Electronic Design

A smart designer carefully chooses antennas and their placement and orientation in a product before beginning electronic design.  That’s the best way to be sure from the start that you will avoid the typical and costly antenna mistakes that cause LTE certification failures.  Antenna selection before electronic design is one of the core principles of the BluFlux Design For Cellular Certification (DFCC™) process.

BluFlux antenna designers can help you select antennas that will meet your product’s requirements for the lowest possible BOM and integration cost and also help you place and orient them for optimal performance. BluFlux is a CTIA-Authorized Test Lab (CATL). So the BluFlux RF test chamber is officially certified as calibrated to perform all the necessary tests to confirm that your antenna configuration, in combination with your chosen cellular module, will meet your carrier’s requirements.

Another standard part of the DFCC™ process is a quick set of RF chamber tests to make sure your antenna, layout and RF front end components will pass carrier certification before you even begin your electronic design.  If you’re at all concerned about wasting design effort on the wrong architecture or components, call BluFlux first!

Design to Minimize RF Noise and Susceptibility

Every year, electronic products process information at faster speeds. Faster processing requires increasingly sophisticated microprocessors and memory.  Faster chips require high frequency clocks. High frequency clocks can cause harmonic noise.

Another potential source of harmonic noise that can impact RF equipment (including your cellular circuitry) is a switchmode power supply (SMPS). Because of today’s packaging, temperature, efficiency, and portability constraints, there’s a good chance you’ll need to use an SMPS instead of a linear regulator.

The noise from your high frequency circuits will be conducted or radiated into your product’s cellular RF front end (i.e. your module, matching networks, feedlines, and antennas). Such noise can not only cause problems for your FCC testing, but it can also cause your product to fail TIS tests at your carrier’s cellular certification lab.

Radiated Spurious Emissions

When your device causes radiation that interferes with another device’s radio, it is known as Radiated Spurious Emissions (RSE).  RSE limits are specified by various regulatory and industry certification bodies such as the FCC, ETSI, PTCRB and GCF.  You can prevent RSE failures by employing smart RF design best practices.  These include shielding of noise sources, proper PCB layout stackup for noise mitigation, and proper selection and placement of filtering components at noise sources.

Preventing and Solving RF Noise in Cellular Products

BluFlux’s RF and electronics engineers can review your entire product design before you begin enclosure prototyping or PCB fabrication to make sure you are implementing noise mitigation best practices.  It’s a low cost way to avoid wasting valuable time and money on a noisy design that could destroy your RF performance – and your chances of getting LTE certification.

OTA LTE Pre-Certification Testing and Troubleshooting

A typical journey through an LTE carrier’s cellular certification process will likely cost you between $50,000 and $100,000 in internal and external costs and consume several months of your development by the time you have finished a single complete set of testing.  If problems arise during any of your cellular certification testing (FCC, SAR, RSE, OTA, ECC, etc) you’ll eventually have to open your wallet for another round of test lab costs. Meanwhile, your internal costs will continue to grow while your engineers struggle to resolve the root causes of your failures.

Even worse, you’ll miss out on revenue from product sales because your carrier will not permit you on their network until you pass certification.  In the course of a recent 12 month period, several customers finally came to BluFlux for the first time after struggling to solve carrier certification problems on their own for 6 months or more.  It is not uncommon for cellular products to deliver monthly revenue well over $1M.  Do the simple math, and you can’t help but realize that delays due to failing cellular certification can be extremely painful.

If you’ve recently experienced a cellular certification failure, BluFlux can help.  We combine testing and troubleshooting under one roof to quickly hunt down the root cause of any cellular certification. If it’s possible to solve your problem without respinning your PCB, we’ll implement the solution on the units you send us for testing.  And we’ll validate that you’re ready for carrier certification in our RF chamber.

If you’re about to schedule your cellular certification, call us first.  For a small fraction of the cost of full carrier certification testing, we’ll evaluate whether you’re ready – and do whatever is needed to get you to that point.

And if you’re just beginning your product development, you can follow the sequence in our Design for Certification Checklist.  Download the checklist and reach out to us early as possible in your process so we can answer your questions in a free consultation.  Then, when you’re ready, you can schedule a quick set of pre-certification tests to confirm you’re ready to pass Carrier Certification without any trouble.