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LTE RF: Complicated by Design

Band fragmentation and a host of other radio frequency (RF)-related issues could derail the 4G LTE experience, making life particularly tricky for mobile antenna vendors, according to a new Heavy Reading report, "LTE RF Design: Challenges and Opportunities".

And that's tough on the antenna component specialists: They are the Rodney Dangerfields of wireless, reckons Heavy Reading analyst Tim Kridel -- they don't get no respect, but they sure should.

Everyone wants great LTE coverage across the globe on a sleek, thin device with an enormous screen and days-long battery life. However, none of this is possible without multi-band RF capabilities built into the smartphones, and the big problem is that the available space to squeeze antennas into these mobile devices is shrinking by 25 percent annually, according to antenna vendor Ethertronics. (See Next-Gen Challenges of LTE RF Design.)

"With a bigger screen, you'd think there's more space for antennas, but the screen sucks it up and the battery gets bigger," Kridel says. "Antennas are low on the pecking order."

What's more, device makers are used to paying pennies for RF antennas, so the more sophisticated antenna and RF systems required for LTE are a hard sell for the antenna makers.

The reason LTE is such a game changer is that, while the underlying technology is a global standard, the spectrum being licensed for 4G services around the world comprises multiple disparate bands. Antenna makers are therefore being required to cost-effectively support more than 40 potential bands, 19 of which are currently in use, in addition to 3G/2.5G/2G fallback, Bluetooth, NFC (near-field communications), Wi-Fi and GPS, as well as designing products that will fit into increasingly thin smartphones.

By comparison, the antennas for 3G devices were required to support just four or five bands. (See The Myth of LTE Global Roaming.)

To be called a truly global LTE phone, a device would need to support 12 to 13 of the 19 bands, Kridel says. That still wouldn't match 3G's footprint, but it'd be good enough for most.

Antenna makers are starting to address this spectrum support challenge by developing active antennas that are tunable based on environmental conditions. Changes in the physical environment can mess with a device's antenna -- remember "antennagate"? -- but tunable, multiple input multiple output (MIMO) antennas help alleviate that issue.

Kridel says active antennas are still a niche play right now, but they are a good fit for LTE and operators' heterogeneous networks (het-nets), which will see customers spending more time connected via small cells at the fringes of mobile networks. Qualcomm Inc.'s forthcoming RF360 front-end solution is an early example of an active antenna: It currently supports 40 bands and uses a dynamic antenna matching tuner to work around external issues. (See Qualcomm Unveils Single Global LTE Chip and Qualcomm: Multiband Chips Will Take LTE Global.)

RF vendors will just have their work cut out convincing the handset makers to take on the premium cost. The vendors' goal will be to retain as few SKUs (stock keeping units) as possible for each device model while still reaching the widest possible market, including price-sensitive developing markets. But they'll have to find a solid business reason to do so.

"Price is a consideration, but performance is the big one," Kridel says. "You're paying for LTE and you expect certain things. You think it'll be superfast, and if it doesn't deliver great performance, you question it. Everyone's reputation takes a hit."

— Sarah Reedy, Senior Editor, Light Reading

Tim Kridel 6/18/2013 | 9:33:18 PM
re: LTE RF: Complicated by Design I agree that call quality is terrible. In fact, I'll go a step further and say that it's shit. My hobby is ham radio. I talk to people on the other side of the world using single sideband, and it still blows away any mobile call I've ever had.

It's been that way since I got into the industry in '98. I think the culprits are vocoders and transcoding rather than RF. (Note that I'm not talking about dropped calls, but rather the audio quality of a successful call.) But with VoLTE, RF becomes a big factor in call quality.

Data performance is far more important to me. I'll churn or change phones in a heartbeat over that.
JSBrewerJr 6/17/2013 | 5:08:47 PM
re: LTE RF: Complicated by Design The answer here is for integration of RF front end functions onto the antenna module. Many of the antenna vendors are already a couple generations into integrating antenna tuning ICs onto the antenna module. The 2G PA will be next, as will 3G front end later. 4G will probably remain on the circuit board for quite a while given the mix-and-match frequency allocations worldwide. Putting RF FE onto the antenna module promises better RF FE performance, increases area for battery by shrinking the PC board, and creates a value-added position for the antenna vendors that the RF FE component guys simply won't take on.
Sarah Thomas 6/17/2013 | 3:42:35 PM
re: LTE RF: Complicated by Design BTW, I don't have an exact figure for how much more LTE RF antennas are than 3G. We checked with Ethertronics, who wouldn't put a number to it, but said, "while the cost would be more, the capabilities within help offset other things by speeding up time to market, increasing device efficiency, etc."
Sarah Thomas 6/17/2013 | 3:17:25 PM
re: LTE RF: Complicated by Design I disagree. I think expectations are high for mobile quality and will be even more so on LTE. Look at the backlash to antennagate. People may be used to dropping a few calls, but they expect the operators to do something about it. People will notice if their quality sucks on LTE and whether they blame the device maker, OS vendor or operator, it'll hurt everyone.
derac7020 6/17/2013 | 2:29:57 PM
re: LTE RF: Complicated by Design And no one will notice. The bar is so low on smartphones that it will be a non-issue. Voice quality is terrible. Connectivity is ok but try listening to streaming media and moving around [like walking] and it can be pretty pathetic. The cameras are amazing... for phones.. but as real cameras they are pretty poor. The expectations are so low these days that if you can tweet and post on FB or upload a blurry photo to Instagram you're good. I guess there's a social comment in there somewhere.
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