What is Cel-Fi?

Cel-Fi is a carrier-grade, consumer-friendly smart signal booster that maximizes a user’s indoor wireless experience by eliminating in-building dead zones. It can more than quadruple wireless Internet data speeds and eliminate dropped calls for wireless subscribers in their homes or offices by boosting signal strength from one bar to five bars.

How does Cel-Fi work?

Cel-Fi consists of two units: the Window Unit (WU), and the Coverage Unit (CU). Users place the WU in an area with the strongest signal from the carrier network. The CU is then either placed in the center of the home or office, or in the area where the best signal quality is most needed. The two units communicate wirelessly with one another enabling the CU to effectively produce a “bubble of quality signal” throughout the home or office, resulting in significantly better voice quality and greater data throughput. The WU and the CU are placed at varying distances apart, but in general an indoor distance of up to 20 meters, or 66 feet, is common.

Who uses Cel-Fi?

Cel-Fi is typically used by residential subscribers or SMB/SMEs that experience coverage and/or data throughput and performance problems such as in-building dead-zones and dropped calls.

Why should I use Cel-Fi?

Cel-Fi is used to resolve the issue of poor indoor cellular signal quality in homes, home offices small business and enterprises. Cel-Fi is self-learning and self-configuring, making it fast and easy to install and use. There is no professional installation required, no drilling, and no cables. Users most often say, “if you can install a light bulb, you can install Cel-Fi.”

Will Cel-Fi work with my iPhone?

Yes! All versions of the iPhone (including 5S and 5C) are supported on new RS2 Cel-Fi systems sold on this web site.

Old versions of Cel-Fi RS1 (Cel-Fi does not sell RS1 anymore): iPhone models 4S and earlier do not support band 4 AWS band (1700/2100), so they will not work with an RS1 from T-Mobile. iPhone 5 model A1428 will work with an RS1 from T-Mobile if their serial number ends in FH19, FH1C, FH1D, FH1F, FH1G, FH1H. Tap Settings > General > About to check the serial number on your iPhone.

Does Cel-Fi require an Internet connection?


Can Cel-Fi run on batteries?

Cel-Fi does not currently run on batteries and requires a power outlet to operate. You can install a UPS between Cel-Fi and the power outlet.

I’ve installed Cel-Fi, but my mobile phone’s signal strength is the same.

It is very likely that you are using an iPhone, which measures your signal differently than other devices. Even if your Cel-Fi booster is installed correctly and the service you experience is substantially improved, your iPhone may not show you these improvements in relation to the number of signal strength bars on the phone.

Does your iPhone still display low signal after installing a Cel-Fi signal booster? Did you notice that the iPhone signal bars are not the same as other handsets?

One reason is because the iPhone measures your signal differently than other handsets. Even if your Cel-Fi booster is installed correctly and the service you experience is substantially improved, your iPhone may not show you these improvements in relation to the number of signal strength bars.

However, for those who would like to check the actual signal strength, there is a simple procedure to set your iPhone to display an actual signal strength value through the Field Test Mode. Here is how your do it:

  • Dial *3001#12345#* and press Call
  • Now you are in test mode and the “bars” are replaced with signal level (dBm power is a negative number, with 0 being strongest)
  • Hold the OFF button to get Slide to Power OFF
  • Let go the OFF button and now hold Home key down until you return to the Home screen
  • Now tapping on the antenna meter toggles between Bars and Signal Strength!
  • If the value does not update regularly, force updates by making and ending calls.
  • To undo the setting, dial *3001#12345#* and press Call. Then press the Home button once.
  • If you or someone you know would benefit from a signal booster, click the buy link to see if your carrier supports Cel-Fi!

Which mobile operators offer Cel-Fi?

Cel-Fi is authorized for use by 137 mobile operators around the world. Another 65 carriers are currently testing Cel-Fi on their networks. Of the world’s top 20 mobile operators, 13 have either implemented or are testing Cel-Fi.

Is Cel-Fi operator or service provider specific?

Yes, each Cel-Fi system is customized to work on individual operator network.

Why do mobile operators like Cel-Fi?

It’s estimated that 17% to 25% of all mobile users worldwide experience poor quality indoor wireless coverage, translating into well over 1 billion subscribers globally. As a result, carriers lose more than $10 billion through customer churn, and lost upsell opportunities. Cel-Fi immediately increases retention and subscriber satisfaction. Cel-Fi subscribers buy more services and use more of the ones they have, resulting in increased monthly revenue for carriers.

Is it legal to use signal boosters?

Mobile operators have historically adopted an extremely strict policy against the use of consumer-class boosters on their networks due to interference and resulting damage caused by legacy repeaters. However, Cel-Fi is fully compliant with the new Report and Order for signal boosters as defined by the Federal Communications Commission (FCC).

What makes Cel-Fi different from other smart signal boosters?

Cel-Fi relies on intelligent, self-organizing algorithms to maximize the area of coverage for users while ensuring that it does not compromise or interfere with mobile operator networks or impede other subscribers’ signals. Cel-Fi does not require any new equipment or changes to existing network infrastructure, or mobile devices. Recognized for its superior design and effectiveness, Cel-Fi is the only consumer booster authorized and approved by the communications commissions in Australia and the United Kingdom.

Does Cel-Fi require maintenance or adjustments if changes occur to the serving cellular network?

No. Cel-Fi does not require maintenance, and it will automatically adjust to changing cellular network situations.

What technologies does Cel-Fi support?

The current version of Cel-Fi supports 3G WCDMA/HSPA+ technology, commonly referred to as 3G and 4G but not to be confused with 4G LTE.

What is IntelliBoost?

The Cel-Fi’s IntelliBoost Baseband Processor is the first core processor designed specifically to optimize the indoor transmission and reception of 3G wireless signals. With advanced filtering, equalization and echo cancellation techniques, Nextivity has developed an embedded architecture which delivers unprecedented in-building data rates and pervasive 3G connectivity. The IntelliBoost processor ensures that Cel-Fi products never negatively impact the macro network while providing maximum coverage. By continuously monitoring the gain and making real-time adjustments, the system will never overdrive the base station or raise the noise floor.

What frequency is used to communicate between the two units (the Window Unit and the Coverage Unit)?

Cel-Fi uses channels from both the U-NII-1 (either 5.15-5.25 GHz OR 5.25-5.35GHz) and the U-NII-2 block (5.47-5.725 GHz) to communicate between the Window Unit and the Coverage Unit.

Does a Cel-Fi system have to be activated or provisioned on the mobile operator’s network?

No, Cel-Fi products do not require network activation or provisioning. There is also no need to register an IMSI list of active users.

Experience has shown that traditional repeater products often cause significant degradation to mobile network quality. How is Cel-Fi different?

Cel-Fi utilizes an intelligent processor to actively adjust to the network environment. It uses multiple techniques including automatic gain control, real-time path loss analysis, and uplink signal gating to ensure that it never degrades the quality of the macro network signal or artificially raises the noise floor of the Node B.