The upcoming AWS auction of 1700 MHz and 2100 MHz spectrum, now slated for August, raises the question of how many frequency bands might be jammed onto a handset and whether that poses technical challenges for component and handset vendors.
The answer, at least from two analysts who study the semiconductor industry, is that certain handsets might become seven-band devices. And while each individual chipset or other component may not pose major technical challenges-most already are being made for other markets in Europe and Japan that utilize these 1700 MHz and 2100 MHz frequencies-cramming the components together in the confines of a handset may raise issues of radio interference, while increasing the number and cost of parts.
Component makers that can resolve these issues stand to gain, though obviously it’s impossible to predict who the auction winners might be, or whether they in fact will use their spectrum for cellular networks.
According to Chris Taylor, an RF and component analyst with Strategy Analytics, presumed bidders Cingular Wireless L.L.C. and T-Mobile USA Inc., if successful, will probably offer handsets in the United States with three UMTS bands and four GSM/GPRS bands for a seven-band phone. Such a device, Taylor said, would require multiple power amplifiers, complex radio-frequency switches, additional filters to protect incoming and outgoing signals from interfering with each other, multiple or more complex transceiver chips and two baseband chips or a single baseband with a more complex combination of UMTS and legacy GSM capabilities. For feature-rich phones, toss in RF chips for Bluetooth, Wi-Fi, GPS and, conceivably, digital TV and multiple input, multiple output, which can simultaneously run two or more data streams in the same radio channel.
Combining all these modes and bands in a handset can be tricky; components that work in isolation may not work in combination. Combining modes and bands can impact handoffs between cell sites and interference between the various incoming and outgoing signals.
“This is the primary consideration, but not the only one,” Taylor said. “Running multiple bands in one handset gets complicated. We’re talking filters more than anything. But there are a host of issues that can come up.”
Companies that offer compact components that minimize these effects will have an advantage, according to Taylor. “That’s pretty much the essential proposition going forward,” he said.
The biggest challenge is putting chipsets together that support all the desired combinations of UMTS and legacy GSM bands in a small footprint (read: slim phone) without doubling or tripling the part count. “Thin being in” is great for the style-conscious consumer, but one can imagine roomfuls of engineers gnashing their teeth over how to meet the new design specifications. “All components must be 1.1 [millimeter] high or less,” Taylor pointed out. “Any thicker and you get into issues with the thickness of the phone.”
Likely winners in the filter space, especially bulk acoustic wave filters, with advantages in the higher frequencies, include Infineon Technologies AG; Avago Technologies-pioneers in a product known as an F-bar filter; Triquint Semiconductor Inc.; and Skyworks Solutions Inc.; according to Taylor. Power amplifier vendors and RF transceiver companies also will benefit. Baseband chip makers must combine two baseband chips into one. Some compact baseband chips for W-CDMA and legacy GSM have been successfully combined in a single part by the leading vendors such as Nokia Corp., Texas Instruments Inc., Qualcomm Inc. and Ericsson Mobile Platforms, according to Taylor.
“The devil’s in the details,” Taylor added. “Components are available now. How well they’ll work in some of the more complex handsets is a bit of a question. There might be some hiccups. Seven bands is kind of an extreme case. You might see some handsets supporting five and six bands, even fewer. Today, a phone from Cingular might use one UMTS band and three or four GSM bands. They’re talking about adding additional UMTS bands; that’s where things begin to get complicated.”
According to Will Strauss, principal analyst at Forward Concepts, the entire discussion may be premature. The AWS auction offers a patchwork quilt of coverage areas and likely bidders probably will include traditional cellular players with gaps in coverage, cable and content companies that want an “in” to the wireless industry and, possibly, a couple of 800-pound gorillas such as Google Inc. and Microsoft Corp. However, Strauss said, many players may be tempted to sit out the AWS auction and set their sights on a future auction of 700 MHz spectrum that will offer a complete, nationwide footprint, unless the Federal Communications Commission decides to break it up.
“With one spectrum acquisition you’ve covered the entire U.S.,” Strauss said, “while this AWS thing is a patchwork around the country. Plus, the 700 MHz frequency has better propagation characteristics, so the signal carries further and you can build a network with fewer base stations.”
