Cell phone signal boosters, which are also referred to as repeaters, are available for all of the GSM frequency bands. Some repeaters will handle different types of networks (such as multi-mode GSM and UMTS). A cell phone signal booster can amplify incoming signals up to 32 times. Typical setups can consist of a donor antenna that receives and transmits signals from nearby cell towers, coaxial cables, a signal amplifier, and an indoor rebroadcast antenna.

Utilizing cell phone signal boosters can entail involved technical specifications, but most companies selling such systems are eager to provide assistance to help anyone find the best solution that suits their needs. This article acts as a starter guide to offer an overview of considerations that prospective buyers are to be aware of when choosing a cell phone signal booster system.

When considering signal boosters there are typically four categories mobile-oriented consumers would need to consider. Signal boosters are available for home or small office structures, commercial or industrial buildings, car or truck sized vehicles, RV or camper vehicles.

GSM 900MHz Cell Phone Signal Booster Repeater Mobile Signal AmplifierMore emphasis will be applied to a home-based consumer setup over commercial/industrial operators that could require advanced consulting sessions to provide appropriate solutions to more challenging setups. Non-commercial cell phone users might only want to consider simpler setups with fewer working or installation parts such as to be found with Cel-Fi or femtocell packages in deciding whether or not to deploy their own mobile signal booster for their personal or family/household use.

Essentially, consumers can have a choice of two types of signal boosters. Wide-band/ broadband signal boosters should amplify all frequencies from cell phone carriers. They tend to have system gain of 65 dB (for the low LTE 700MHz bands) to 72 dB (for higher frequencies such as AWS). Then, carrier specific (or provider specific) signal boosters are only designed to boost frequencies (and signal) that belong to a particular carrier. Generally, such carrier specific boosters have larger system gains (sometimes 100 dB).

The process behind how a mobile phone signal booster works can be highly technical and is beyond the scope of this article to fully explain. But a few fundamental aspects explained can be helpful for someone looking to make the right choice of device suited to their particular needs.

Most consumers will likely choose not to get too bogged down in arcane specs regarding signal boosters and would rather be presented with a quick installation solution. Essentially, consumers considering a purchase should need to have the key information about how signal boosters work, how to pick the right accessories, and how to install the signal booster (amplifier) to get the absolute best performance.

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So, anyone contemplating a mobile phone signal booster setup would need to be aware or concerned of crucial elements that make up an efficiently working device. Outlined below are the very needed aspects to be concerned with to get the most effective cell phone signal repeater device into place and operational.

  • Outside or donor antenna
  • Cable that runs from the outdoor antenna to the interior space leading to an amplifier
  • Amplifier that will serve to boost the signal
  • Inside antenna that connects to the amplifier through a second cable

Knowing the location of the closest cell phone tower to you for the purpose of assessing the need for a home-based (or office) mobile phone signal booster setup is a preliminary step and can be done in certain ways (refer to video). Connection strength can be measured through apps, websites, or directly from a cell phone to learn the most powerful direction it points from. 

Cell phone signal boosters are engineered to:

  • Improve 4G LTE & 3G for any phone, tablet, hotspot, etc. on any carrier
  • Amplifies cell phone signal to and from the cell tower
  • Works without being connected to the internet or wifi
  • Expect it to be approved in advance by the FCC and all carriers

Video explaining how a signal booster works

The following YouTube video from weBoost briefly explains fundamentals of signal strength and how the cell phone signal booster works to correct a weak signal. Although the video is produced by a particular corporate brand of signal booster, the explanations offered serve as a basis that can be applied industry-wide.



The Cel-Fi Signal Booster Option

Cel-Fi is a device, engineered by Nextivity, Inc., that works to eliminate in-building dead zones and improve indoor mobile phone reception. The Cel-Fi systems are designed with smart antenna technology that monitors for the best available signal to maximize signal gain to phone users. Each Cel-Fi system consists of two units. The Network Unit is placed in the area (likely to be a window) where the strongest native signal can be received from the carrier network (signal levels as low as -120 dBm are acceptable).

cell phone signal booster Telstra Cel Fi Pro 3G4G Repeater smart repeater yagi connection

The Network Unit comprises a transmitter and receiver which communicates with the cell tower. The Coverage Unit is placed in the center of the home, communicates wirelessly with the Network Unit and provides the affected area with significantly enhanced signal levels, providing better quality calls and greater data throughput.

Distinguishing characteristics of the Cel-Fi booster technology are that Cel-Fi systems are designed with smart antenna technology to seek out the best available signal to maximize signal gain to phone users. Cel-Fi relies on intelligent, self-organizing algorithms to provide the largest area of coverage without compromising or interfering with a mobile operator’s networks or conflicting with other subscribers’ signals. The YouTube video below explains the principles of operation of a Cel-Fi cellular booster and its setup.

 The Femtocell Signal Booster Option

A femtocell allows service providers to extend service coverage indoors or at the cell edge, especially where access would otherwise be limited or unavailable. Much focus of this technology is on WCDMA, but it is applicable to all standards, including GSM, CDMA2000, TD-SCDMA, WiMAX and LTE solutions.

The use of femtocells allows network coverage in places where the signal to the main network cells might be too weak. Also, femtocells de-emphasize overloading the main network cells, by forming a connection from the end user, through an internet connection, to the operator's private network infrastructure elsewhere. Many operators worldwide offer a femtocell service, mainly targeted at businesses but also offered to individual customers (often for a one-off fee) when they complain to the operator regarding a poor or non-existent signal at their location.

Femtocells are an alternative way to deliver the benefits of fixed–mobile convergence (FMC). The distinction is that most FMC architectures require a new dual-mode handset which works with existing unlicensed spectrum home/enterprise wireless access points, while a femtocell-based deployment will work with existing handsets but requires the installation of a new access point that uses licensed spectrum. The YouTube video below explains how femtocell works while comparing it to a cell phone booster to show highlight the differences.

Consumers and small businesses benefit from greatly improved coverage and signal strength since they have a de facto base station inside their premises. As a result of being relatively close to the femtocell, the mobile phone (user equipment) expends significantly less power for communication with it, thus increasing battery life. They may also get better voice quality (via HD voice) depending on a number of factors such as operator/network support, customer contract/price plan, phone and operating system support. Some carriers may also offer more attractive tariffs, for example, discounted calls from home.

Signal quality can limit the number of bars just as much as signal strength. Understanding this fact is really important for installing a signal booster correctly. But it is also helpful, if not essential to understand some of the pertinent terms and definitions that go a long way to make the right equipment purchase and following setup. The following terminology helps to further clarify cell phone signal booster technology and how to communicate your needs to a setup specialist

Signal and Cell Repeater Terminology

3 dB – dB is a logarithmic scale, and 3 dB is exactly half the power. Most splitters have around 3 dB attenuation – they split the power coming through a coaxial cable in half.

AGC- Automatic gain control. This can also be referred to as automatic volume control (AVC). The purpose of the AGC is to provide controlled signal amplitude, even with variances in the amplitude of the input signal.

ALC - Automatic level control. There is little difference between this and AGC with the exception that ALC typically refers to audio output to a speaker.

Antenna gain (dBi) – Indicates how strong a signal an antenna can send or receive in a specified direction. Gain is calculated by comparing the measured power transmitted or received by the antenna in a specific direction to the power transmitted or received by a hypothetical ideal antenna in the same situation. The gain is measured in dBi (decibels-isotropic).

Attenuation (dB) – Attenuation is the weakening of signal over distance, or as it passes through building material. Attenuation is measured in dB, and is typically a negative value (signal gets weaker). -10 dB attenuation is 10 times weaker signal. -20 dB attenuation is 100 times weaker signal.

AWS – Advanced Wireless Services is a microwave frequency spectrum band used for voice, data, video, and messaging services. It's used in the US, Canada, Argentina, Colombia, Mexico, Chile, Peru Paraguay, Ecuador, and Uruguay.

Bluetooth – A wireless technology standard invented by mobile phone maker Ericsson in 1994 that exchanges data over short distances from mobile and fixed devices, and can be used to build personal area networks and linking to mobile and peripheral devices.

CDMA – Code division multiple access; a channel access method used by different radio communication technologies. As a form of multiple access, several transmitters can send information simultaneously over a single communication channel.

Cell Phone Signal Booster (a.k.a. Signal Repeater, Signal Amplifier, Signal Booster or Amplifier, or a Cellular Repeater) – A type of bi-directional amplifier used to improve cell phone reception, strength and increase coverage, especially indoors, but outdoor systems are available too.

Coaxial cable – Coaxial cable is a special type of cable designed to carry radio frequency (RF) signal. It typically has a copper center conductor, some sort of shielding, and an outer conductor.

dB – Cellular signal strength is measured in decibels (dB), and typically range from -50 dB to -110 dB. The dB scale is logarithmic. This means that every 3 dB increase doubles the power. For example, -67 dB is twice the power of -70 dB.

dBm – Abbreviation for the power ratio in decibels (dB) of the measured power referenced to one milliwatt. Used in radio, microwave, and fiber-optical networks. It is a measure of absolute power used for describing very large and very small values in a short form.

Directional (beam) antenna – This antenna is adapted to radiate or receive greater power for specific (front-facing) directions allowing for increased performance and reduced interference from unwanted sources. They perform better than omnidirectional antennas in situations when they are pointed toward a target direction. Three main types of directional antenna are “panel,” “yagi,” and “log periodic” antennas.

Dome antenna – A dome antenna is a type of indoor antenna that needs to be installed in the ceiling of a building, and transmits its signals downwards but over a wide area in all directions.

Donor (outside) antenna – The donor antenna in a signal booster system is the antenna placed outside the building or vehicle and that connects with the cell phone tower.

Downlink signal – the signal sent from the cell phone tower to a phone utilizing the signal booster setup.

External antenna – An omnidirectional or directional antenna installed outside to pull in the radio signals from the cell phone tower. Unlike a Donor antenna, the omnidirectional aspect of this antenna is ideally suited for automotive and other vehicular (camper, boat) use.

FCC – The Federal Communications Commission, the government organization responsible for regulating use of the airwaves (and signal boosters) in the US.

Gain (dB) – Gain is the measure of amplification. The higher the gain, the more the signal is amplified. Gain is typically a positive dB number, and it’s measured on a logarithmic scale. 0 dB gain means no gain. 10 dB gain equates to 10 times the signal strength, but 20 dB gain is 100 times more signal, and 30 dB gain is 1,000 times more signal.

GPRS (General Packet Radio Service) – A packet oriented mobile data service on 2G and 3G cellular communication systems' global system for mobile communications.

GSM (Global System for Mobile Communications) – A standard introduced by the European Telecommunications Standards Institute (ETSI) and deployed through much of the globe.

HSPA+ – Evolved High-Speed Packet Access or HSPA+ is a technical standard for wireless, broadband telecommunication; it is the second phase of HSPA. It can achieve data rates of up to 42.2 Mbit/s. Advanced HSPA+ is the next step of this technology and can attain data rates of up to 84.4 and 168 Mbit/s. It uses antenna array technologies such as beamforming and MIMO.

Indoor (internal) antenna – The indoor antenna of a signal booster setup is the antenna that is installed inside the building or vehicle and that links with the cell phone operating off of the signal booster arrangement.

ISO – Short for isolation. The amount of signal that travels from the input to the output of a switch represents the measure of isolation in decibels (dB). -65 dB is considered the best for isolation. When two antennas are physically close to each other, radiofrequency isolation is decreased. The two antennas can "hear" each other. This translates in practice by placing the outdoor and indoor antennas far apart from each other to reduce this kind of interference. Using building structures such as walls will help increase isolation.

Lightning surge protector – A device that protects sensitive electronic equipment (such as a computer) and signal boosting equipment in case lightning hits the donor antenna. It can be an independent accessory from the signal booster apparatus.

LTE – Short for Long Term Evolution; this stands for the evolving technology standards of mobile service providers to keep data speeds improving across their networks.

MiFi – Introduced into the U.S. by Novatel Wireless in 2009, it is a wireless router that acts as a mobile Wi-Fi hotspot. These can be connected to a cellular network and provide access to the internet for multiple devices. An alternative to this is using your mobile phone as a Wi-Fi hotspot using "tethering," as increasingly more cell phones have become capable of doing so.

Omni-directional antenna – An antenna with low antenna gain that receives and transmits a signal in almost all directions equally.

Panel antenna – A panel antenna is a type of antenna that can be installed as a donor antenna outdoors or indoors on a wall, and transmits signal outwards in the direction it is facing. It uses UHF (ultra-high frequencies) and is often used for cellular base stations or wireless networking.

PCS (Personal communications service) – PCS refers to any of several types of wireless voice and/or wireless data communications systems. It gives a user an all-in-one wireless phone, paging, messaging, and data service to work from.

Radio frequency (RF) – Radio frequency is any frequency used to transmit a wireless radio signal, which includes cellular signal, WiFi signal, and regular FM and AM radio.

RSSI – Received signal strength indicator. This is the measurement of the power present in a received radio signal.

Signal strength (dBm) – A wireless signal’s strength is measured in dBm. Similar to gain, the signal is logarithmic. 0 dBm is 1 milliwatt, or 0.001 Watts; 30 dBm is 1 Watt; -10dBm is 0.0001 W, or 0.1 milliwatt.

UMTS (Universal Mobile Telecommunications System) – A third generation mobile cellular system for networks based on the GSM standard. It was developed and maintained by the 3GPP (Third Generation Partnership Project). UMTS is a component of the International Telecommunications Union IMT-2000 standard set and is an alternative to the CDMA2000 standard set for networks based on the competing CDMA-One technology. It uses wide-band code division multiple access for greater spectral efficiency and bandwidth to mobile network operators. This technology is also occasionally called FOMA (Freedom of Mobile Multimedia Access) or 3GSM. It is more commonly deployed in Europe, Japan, and China.

Uplink signal – the signal sent from a cell phone back to the tower.

WCDMA (Wideband Code Division Multiple Access) – Technology developed by GSM community to support 3G mobile devices. This supported voice, text, and MMS services, WCDMA also increased data speeds. This was the technology used by UMTS to improve service to mobile network operators






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Cell phone signal boosters, how they work and are set up for home, office, and vehicle