Boost Weak Cell Service at Home: Your Options

Revised July 15, 2011. Originally published April 12, 2010.

The problem is familiar to many cell phone users: When you're indoors, even within your carrier's coverage area, the network's signal sometimes simply isn't strong enough to support voice calls or data services. With so many consumers ditching their landlines for cell phones, poor reception at home is no longer acceptable. Fortunately, a slew of products now address the problem, though they don't come cheap.

Ssignal-boosting products generally fall into one of two categories: femtocells or signal repeaters. Both types of equipment can deliver strong signals within buildings, but they work in fundamentally different ways.

Femtocells act as miniature cell phone towers that connect to a home network router and use your wired broadband connection to move voice calls and data services to and from your carrier's network. Femtocells don't rely on the carrier's towers at all, but because they use technology that can direct data and calls back to the carrier networks over the Internet, most of them are sold by the carriers themselves.

Repeaters and boosters, on the other hand, amplify and rebroadcast cell tower signals. Since they don't require carrier support, they tend to be manufactured and sold by third parties such as Wi-Ex (under the brand name ZBoost) and Wilson Electronics.

Understanding Femtocells

While repeaters have been around for several years, femtocells are relative newcomers to the mobile scene. Of the four major U.S. carriers, two--Sprint and Verizon--have been selling femtocells (under the brand names Airave and Network Extender, respectively) for the past few years; AT&T introduced its 3G MicroCell femtocell last year.

AT&T 3G MicroCell.
AT&T's 3G MicroCell, made by Cisco. Image: AT&T
The first Sprint and Verizon Wireless femtocells supported only voice calls, but current models support high-speed data as well as voice. Sprint charges $130 for its Airave access point (with a two-year service plan); there's no additional charge for using Airave to enhance coverage with an existing plan, but Sprint does offer a $25-a-month unlimited calling plan for Airave calls--which might appeal to anyone who is considering dropping landline voice service. Current Airave access points support EvDO Rev. A 3G data speeds and up to six simultaneous calls.

Verizon Wireless charges $250 for its Network Extender, which also supports 3G data, and the carrier imposes no monthly service fee. AT&T sells the MicroCell for $150, also with no mandatory service fee; it also offer an optional $20-a-month unlimited calling plan, plus price breaks for customers who sign up for the company's DSL service.

The Beauty of the Femtocell

Femtocells appeal to consumers and carriers on several levels. Consumers like them because they provide immediate five-bar coverage across an area of up to 2500 square feet, regardless of how far you are from a cell phone tower. A strong signal typically means better voice quality, fewer dropped calls, and faster data speeds. Good signals also improve a phone's battery life, since its radios don't have to work as hard.

How femtocells work.
Femtocells are low-power wireless access points that operate within a licensed spectrum to connect standard mobile devices to a mobile operator’s network via residential DSL or cable broadband connections. Image: Femto Forum
Another benefit: You can configure the femtocell to recognize and prioritize the phones you authorize, so neighbors can't mooch off your service at your expense. Interestingly, Verizon Wireless's FAQ for its Network Extender says that, though you can prioritize up to 50 Verizon Wireless numbers, the device will remain available to all Verizon Wireless subscribers within range when priority numbers aren't using it.

This brings us to a big reason why wireless providers like femtocells: They offload some of the expense that the carriers might otherwise incur in order to expand network capacity and/or coverage. Femtocells also help retain customers in locations where carriers can't significantly improve reception on their own (such as basements, suburbs that don't want new cell towers, locales with difficult topography such as steep hills and valleys, and skyscrapers with thick walls). In fact, forum posts indicate that Sprint has occasionally given customers Airave units to keep them from switching to another carrier.

Femtocell Weaknesses

Price aside, femtocells have some limitations. For one thing, you can use a femtocell only at the address where it is registered. To enforce that restriction, the FCC stipulates that all femtocells must be equipped with GPS receivers, and that they either must be placed close enough to a window to receive GPS signals directly or must be connected to a GPS antenna that can pick up the signals.

David Nowicki, marketing vice president for femtocell vendor Airvana and for the Femto Forum trade association, says that the FCC imposed the location restriction to enable carriers to track the femtocell's position and disable its operation in areas where the carrier doesn't own the frequencies that the femtocell supports and where, consequently, using the femtocell might interfere with another carrier's network. Even so, forum posts suggest that femtocells sometimes hurt neighbors' regular network reception when deployed in close proximity.

Then again, it’s not necessarily a bad thing that femtocells are aware of their location. That, coupled with the device's ability to recognize when an authorized phone is nearby, could enable carriers to offer customers additional services that go beyond improving reception, including 911 services.

Network handoff issues are another concern. You can start a call on femtocell service and then hand it off to the regular network as you leave the femtocell's coverage area (assuming that the nearest cell tower is close enough). But calls initiated on the regular network can't be handed off to a femtocell.

And finally, critics complain about having to pay for a service that essentially deliver what the wireless network is supposed to have provided all along. "It's a fair point," Nowicki concedes. But carrier spokespeople say that no carrier can provide coverage in all locations of its service area. Verizon Wireless spokesperson Thomas Pica describes the Network Extender as a "niche product," given that the vast majority of Verizon customers don't need one because of the carrier's robust network.

What about the broadband ISP that now gets to carry the wireless carrier's traffic? Nowicki says that the bandwidth consumption of mobile devices is tiny compared to that of most home and office networks. For that reason, femtocells don't impose a significant burden on the ISP, which in some cases is run by the same company as the mobile carrier anyway.

T-Mobile’s Approach

T-Mobile has taken a different approach to improving weak cell signals. Phones that support Wi-Fi Calling use UMA (Unified Mobile Access) technology to route calls over Wi-Fi hotspots. T-Mobile notes that this helps with calls made through any hotspot that its phones can access, and not just at a single location (which is the case with femtocells). However, T-Mobile's Android phones can't hand off calls made using Wi-Fi hotspots to T-Mobile's cellular network; other phones that support Wi-Fi Calling can. T-Mobile has no announced plans to introduce femtocells, but a spokesperson says that the carrier continues to review customer equipment options for improving coverage.

Repeaters and Boosters

Repeaters (also called "boosters")--the other class of products designed to improve poor cell reception--depend on at least a weak cell tower signal to amplify and rebroadcast. They work with specific frequencies, independent of carrier; some support more than one frequency. On the frequencies they support, repeaters improve both voice calls and data speeds.

The Wi-Ex ZBoost repeater kit includes a signal antenna (for outside reception), a coaxial cable, a power supply, and a mountable base unit. Image: Wi-Ex
Many repeaters have multiple parts, starting with an antenna that you place as close as possible to the strongest cell tower signal--typically, near a window or even outdoors. The antenna transmits signals over a cable connected to an amplifier, which boosts the signal and retransmits it indoors. In some cases, the amplifier and indoor antenna are integrated; in others, the amplifier hooks up to a separate, centrally located indoor antenna in the home or office. The area of coverage depends on the strength of the amplifier and of the signal being amplified.

Unlike femtocells, repeaters can't be configured to recognize specific phones. Consequently, the amplified signals benefit any mobile device within range that operates on the supported frequencies--though obviously the owner's devices are more likely to benefit than a neighbor's devices located farther away from the indoor antenna. It's up to you (with the help of your reseller) to ensure that your repeater kit amplifies the frequency or frequencies that your carrier uses in your area. You can get help in choosing the right repeater kit from specialty retailers such as or RepeaterStore.

Repeaters Don’t Come Cheap

Repeater kits can be more expensive than femtocells. Pricing depends on how large an area you want to cover. Wi-Ex's ZBoost line includes SoHo products that range in price from $169 to $399, and you can spend up to $600 for kits that cover areas larger than 2500 feet--the maximum handled by femtocells. On the other hand, Wi-Ex marketing vice president Sharon Cupett notes, there are no monthly fees for repeaters--and of course, no broadband service is involved.

Though repeaters rebroadcast over carrier-owned frequencies, they are legal if they don't interfere with cell tower signals (which is why repeater signals have limited strength). One way to avoid problems is to look for FCC-certified repeaters; some are still awaiting approval, however. Check with the reseller.

Repeater vs. Femtocell

Should you get a repeater or a femtocell? Generally, femtocells are a good match for cell phone customers with broadband service who don't want to pay $300 or more for equivalent repeater coverage and who want to avoid many of the antenna-positioning hassles that repeaters entail. You do need a GPS signal, but those are available pretty much everywhere. Cell tower sites with signals that repeaters can work with are probably less common. But if your carrier doesn't offer a femtocell, a repeater may be the only way to improve your indoor coverage.

Subscribe to the Best of PCWorld Newsletter