In a May survey of 1,000 U.S. consumers, market strategy consultant iGR found that 47% didn't know what a femtocell was. A mere 2% were using one. But if offered one, 57% said they would up their carrier's rating by a full letter or plus sign. "While many people are not aware of residential femtocells, the fact is that many people have poor or marginal in-home cellular coverage," Iain Gillott, iGR's president and founder said in a release. Femtocell rollout has been steady, said Germano with the Small Cell Forum. He estimates that each of the three U.S. carriers have sent out "upwards of a half-million units each." Most are 2G and 3G devices, which created an issue for new iPhone 5 owners because the 4G phone was incompatible. There are 4G femtocells in the works. Sprint, the first in the U.S. to launch its Airave femtocell in 2007, said in an FCC filing in July that it had 950,000 femtocells in operation, nearly quadruple from 15 months earlier, as noted by FierceWireless. In a Small Cell Forum update, Sprint said it plans to double femtocell rollout in 2013. Sprint currently offers Airave free to customers with poor in-home coverage. For others, it sells the Airave for $129, though customers of Sprint-owned Boost Mobile and Virgin Mobile can't use it. The non-femtocell carriers do offer some alternatives. Signal boosters by Wilson Electronics and Wi-Ex are readily available online at in stores. T-Mobile offers distressed customers the Cel-Fi signal booster from Nextivity. Also, as previously mentioned, it has long offered Wi-Fi calling service, which allows a Wi-Fi enabled phone to use a home's Wi-Fi for calls. For more tips on improving signal indoors, also read New Ways to Improve Cellphone Reception Indoors and 7 Apps That Improve Smartphone Reception. While residential femtocells made up 100% of all sales initially, last year one-third sold for enterprise use, according to Small Cell Forum. Today, there are also picocells being deployed in indoor public areas like airports and shopping centers, and metrocells and microcells that target urban areas suffering from bottlenecks. The new small cells target data usage -- existing home femtocells target better voice calls. Small cells are being used to offload data usage so carriers don't worry about bogged down networks. "Now we're seeing data explosion where coverage is not the only factor," Germano said. "We recently released a report that with a relatively small number of small cells attached to macrocell, you can offload a significant number of users. We're seeing small cells being offloaded strategically. As few as 10 small cells in a macro can offload 75 percent of all the (data) traffic." This article was written by an independent contributor, separate from TheStreet's regular news coverage.