Hear that whooshing sound? That's the Internet racing down to your smartphone at full wireline broadband speeds, thanks to new LTE mobile networks.

If you haven't experienced LTE firsthand yet, you will. While analysts have been haggling over the true definition of 4G, the mobile industry has been steadily coalescing around LTE as the de facto standard for the next generation of mobile broadband. As of May 2011, 208 wireless carriers in 80 countries are investing in LTE systems. According to the Global mobile Suppliers Association (GSA), LTE is now the fastest-growing mobile technology in the history of the industry.

Andrew GreenThere are good reasons for this growth. LTE combines high data rates, low latency and relatively low rollout costs, providing mobile operators an attractive option for slaking our endless thirst for mobile data capacity. For those designing products and applications to take advantage of it, however, LTE also poses some unique challenges. To succeed with LTE, OEMs and system integrators need to think very carefully about the LTE modems or embedded modules they plan to use in their solutions, and the LTE communications suppliers who will provide them.

The Next Big Thing in Mobile Broadband
So what's driving the mad dash to LTE? Try to envision an application or user that couldn't benefit from data rates 10 times faster than most current 3G systems. With up to 100-Mbps/50-Mbps download/upload speeds and latency a fraction of today's mobile networks, LTE can power the new generation of mobile broadband, video and cloud applications. Mobile consumer devices, connected cars, enterprise applications, machine-to-machine (M2M) connected products — all can benefit from the capacity and performance boost LTE enables.

Effectively, LTE can deliver a wireline-grade broadband experience — or better — literally anywhere you want it, at a comparable cost per bit. In fact, expect wireless carriers to start competing directly with cable and telco service providers over the next few years for residential broadband customers, especially in rural and hard-to-reach areas. This is to say nothing of the huge savings wireless carriers realize from LTE, which offers much lower cost-per-bit compared to other high-speed mobile broadband options.

This is all good news — for wireless network operators, mobile device and application developers, and especially for users. But, if you're an OEM or system integrator, LTE also introduces some new design issues you're going to have to consider. The most important being that your modem or embedded module needs to do much more than just LTE.

Designing for a Multi-Mode World
For the foreseeable future, the vast majority of LTE-connected devices will operate in pockets of LTE coverage separated by large areas of 3G or even 2G service. That means any practical LTE solution needs to support a complex combination of wireless technologies, including HSPA+, 3G HSPA and 2G, often in multiple frequency band combinations. Cellular engineers will be earning their salaries, dealing with more components, more heat, higher power consumption and more extensive testing requirements to account for so many operating states.

Fitting all those components into a small, power-efficient package is just the first step. The harder task is making it all play nicely together as the device negotiates handoffs from one type of coverage to another. It's not good enough to simply maintain a network connection. The device needs to preserve the best possible user experience by transparently selecting the next-best available option when roaming out of LTE coverage. (If you're videoconferencing on the train ride to work and your tablet PC switches from LTE to 2G, the fact that you still technically have a data connection will be little consolation.)

All of those consideration — multi-mode/multi-frequency operation, power efficiency, heat control, handover intelligence — depend entirely on a well-designed LTE modem or module.

Thinking Antennas
If you haven't thought much about your cellular devices' antennas recently, you're not alone. Despite many other innovations in 2G and 3G technologies, standard diversity antennas have stayed pretty much the same for a few years. With LTE though, the underappreciated field of antenna design is about to make a comeback.

In the first place, LTE often operates in lower frequency bands that are inherently noisier than most 3G spectrum. LTE also uses multiple-input multiple-output (MIMO) antennas, which are far more complicated than those used in 3G solutions. Balanced antenna structure, distance between antennas, polarity and even directionality suddenly become very important. Engineers also need to realize that, since many wireless carriers are re-using existing 2G cell sites to roll out LTE, those cell sites are not necessarily located in the ideal spots you would want them if you were building an LTE network from scratch.

Put all of this together, and you reach one conclusion: If the antennas in your modem or module aren't expertly designed, they will noticeably deteriorate the user experience.

Avoiding Bottlenecks
Imagine trying to attach a fire hose to your lawn sprinkler. That's effectively what you're doing when you bring a high-capacity LTE connection to a USB modem. You better make sure that interface is well designed, or you're going to end up with a big mess.

A successful LTE modem needs to interface efficiently with the user's computer. It should be able to provide ample throughput with a minimal footprint on the host, and be architected so the host doesn't run out of CPU cycles just servicing that modem.

Careful consideration should also be given to the installer software and drivers, which tend to be the cause of most problems users experience with USB devices. Given the complexity of LTE technology, architecting the installation properly becomes even more important.

Getting Down to Business
These are just some of the issues you have to consider when developing LTE-connected products. Given these complexities, it's best to assume that any modem or embedded module you use will likely be a largely customized solution, designed to accommodate the specific requirements of the markets and applications you're targeting. It's critically important, then, to work with an LTE communications supplier who has thought extensively about these questions.

Look for LTE partners with:

  • A long history of successful multi-mode/multi-frequency solutions
  • Expertise in antenna design and testing
  • A strong track record of successful modem integration
  • Global expertise, with a clear understanding of how operators are deploying LTE in different regions
  • Strong professional services as well as technology, to help shepherd products from early design through testing and validation

Even more important than in the past, you also want a cellular partner with strong relationships with wireless carriers and a track record of certifying different types of products on many different networks worldwide. That know-how will go a long way toward streamlining the certification process. Ultimately, it will help you deliver the LTE product your users want, and get it in their hands as quickly as possible.

Andrew Green is the vice president of marketing for mobile computing at Sierra Wireless (