An in-building cellular enhancement system, commonly implemented in conjunction with a

distributed antenna system A distributed antenna system, or DAS, is a network of spatially separated antenna nodes connected to a common source via a transport medium that provides wireless service within a geographic area or structure. DAS antenna elevations are general ...

(DAS), is a telecommunications solution which is used to extend and distribute the cellular signal of a given

mobile network operator A mobile network operator (MNO), also known as a wireless service provider, wireless carrier, cellular company, or mobile network carrier, is a provider of wireless communications services that owns or controls all the elements necessary to sell ...

(hereafter abbreviated as an MNO) within a building. In the United States, operators commonly supported by such solutions include

AT&T Mobility AT&T Mobility LLC, also known as AT&T Wireless and marketed as simply AT&T, is an American telecommunications company. It is a wholly owned subsidiary of AT&T Inc. and provides wireless services in the United States. AT&T Mobility is the thi ...

Verizon Wireless Verizon is an American wireless network operator that previously operated as a separate division of Verizon Communications under the name Verizon Wireless. In a 2019 reorganization, Verizon moved the wireless products and services into the divi ...

Sprint Corporation Sprint Corporation was an American telecommunications company. Before it Merger of Sprint Corporation and T-Mobile US, merged with T-Mobile US on April 1, 2020, it was the fourth-largest mobile network operator in the United States, serving 54.3 ...

T-Mobile US T-Mobile US, Inc. is an American wireless network operator headquartered in Overland Park, Kansas and Bellevue, Washington, U.S. Its largest shareholder is a multinational telecommunications company Deutsche Telekom AG, which , holds 48.4 perc ...

, in addition to smaller regional carriers as required. Below ground level, large buildings and high rises are examples where mobile phones are unable to properly reach the carrier's macro or outdoor network. In these environments, the in-building cellular enhancement system will connect to the carrier's signal source which is typically a

bi-directional amplifier A cellular repeater (also known as cell phone signal booster or cell phone signal amplifier) is a type of bi-directional amplifier used to improve cell phone reception. A cellular repeater system commonly consists of a donor Antenna (radio), anten ...

or a

base transceiver station A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, o ...

. This signal source transmits (and receives) the mobile network operator's licensed

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...

. This frequency is then transported within the building using

coaxial cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

or Category 5e/ Category 6

twisted pair cable Twisted pair cabling is a type of wiring used for communications in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted ba ...

. In-building coverage antennas are strategically placed to provide the best overall coverage for users.

Application independence

A cellular enhancement system does not read or modify the information represented within the radio frequency (RF) that passes through the system; rather, it reinforces the signal penetration of voice and data frequencies in low signal areas and in dead spots within structures,

2G to 4G migration

As the industry evolves, most MNO networks are now made up of 3G based services and are migrating towards 4G based services. In-building cellular enhancement systems designed for 2G or primarily voice-based services may not be sufficient to support 4G services since signal strength and signal quality specifications become more stringent as the applications move from a voice-centric paradigm to a high speed data-centric paradigm. Therefore, a system designed to provide good quality 2G services may be insufficient or unable to provide quality 4G services. Traditionally, MNO services have been delivered within two frequency ranges: the 800 MHz band and the 1900 MHz band. Additional frequency bands have been auctioned by the FCC resulting in increased capacity for the MNOs which are starting to implement 4G services in the 700 MHz and 2100 MHz frequency ranges.

Passive in-building cellular enhancement system

A coaxial cable-only system is typically referred to as a passive system when all system components (other than the signal source) are coaxial cable, coverage antennas and other components that do not require AC or DC power to function.

Pros and cons of a passive system

A passive system is less expensive to install and is best suited for smaller buildings where one or possibly two MNOs need to be enhanced within the building and are not usually installed in spaces over . Passive systems require the RF power to be balanced among all the coverage antennas so there is uniform signal strength throughout the building. Expanding a passive system after the initial deployment could require a re-engineering of the entire system to ensure proper operation throughout the building. The number of in-building antennas and coverage area is dependent on the output power of the signal source.

Active in-building cellular enhancement system

Systems that require conversion of the radio frequency into other forms, such as optical signals, use products that require AC or DC power to perform the conversion near the signal source. Additional products located throughout the building are then used to convert the signals back into native radio frequency format, which are then transmitted through the coverage antennas. Since the equipment at both ends of the cable require AC or DC power to operate, the system is considered to be active.

Pros and cons of an active system

An active system can be deployed in large buildings and/or within a campus of buildings by converting and transporting the radio frequency over optical fiber. Many active systems have been deployed covering areas of and larger. Active systems are best suited when there is a need to support multiple MNOs or large single buildings or campuses with multiple buildings. Expansion of an active system is usually in the form of adding more active equipment to increase the number of coverage antennas within the building, to increase the number of MNOs, or to increase the service offerings of an MNO such as adding 3G or 4G services. In a properly designed active system, no reengineering or rebalancing of the original system is required when the system is expanded. Optical fiber systems can provide coverage in areas up to 2 km from the signal source making them ideal for campus environments. An active system will always be more expensive than a passive system.

References

{{Reflist Mobile telecommunications