Recent legal cases between some wireless carriers and manufacturers of signal boosters also known as handset amplifiers have moved the FCC to issue a Notice of Proposed Rulemaking (NPRM) to address interference concerns by the mobile operator. The FCC initiated the proceeding to “facilitate the development and deployment of well-designed signal boosters” In the proceeding, the FCC proposes to amend Parts 1, 2, 22, 24, 27, 90, and 95 to adopt new technical, operational, and coordination parameters for fixed and mobile signal boosters. Several firms have previously filed petitions for rulemaking all of which relate to signal boosters. The NPRM proposes to authorize individuals to use fixed and mobile consumer signal boosters under Part 95 subject to specific technical requirements including out-of-band-emissions (OOBE), oscillation detection feature, power down or shut down operation when near a base station (BTS) as well as Class A or Class B operation and frequency selection.

Typical Signal Booster System
Typical Signal Booster System

Although some signal boosters installed improperly are proven to disrupt cellular/PCS services, they also provide public safety benefits where E911 coverage is lacking. While signal boosters can be a cost effective “quick fix” for carriers to bridge service gaps in weak coverage in building environments such as inside office buildings or even shipping vessels, they also can cause problems. Unlike wireless handsets which are under the control of the wireless licensee’s base station (BTS), signal boosters are not controlled directly by the wireless licensee.

Although Distributed Antenna Systems (DAS) are becoming more widespread in a carrier’s network, this NPRM should be a response to the fixed or mobile signal booster that inconspicuously enters and disrupts a wireless network with no prior knowledge by the operator. DAS configurations may be considered signal boosters when the network of internal antennas achieves communication through the use of an amplifier that is connected to an external antenna that talks to a base station wirelessly. Moreover, a DAS can degrade the performance of a wireless carrier network if not designed and installed properly. However, many of the anomalous and sometimes random severe cases of network performance issues owing to “repeaters” are due to improperly installed signal boosters.

Signal boosters that do not meet OOBE, for example, or improperly installed or malfunctioning can cause interference to both commercial and public safety wireless networks. Typically, mobile signal boosters transmit and receive wireless signals to and from a cell phone operating inside a vehicle, RV or boat. Mobile signal boosters can be most problematic since they can move rapidly toward a base station and raise the noise floor of the BTS receiver which can cause failed call attempts, reduced coverage area or dropped calls. Wireless carriers can deal with a multitude of network performance issues but signal boosters are not the only driving factor for increasing revenue and reducing churn. New site builds, capacity issues, backhaul, hardware upgrades and antenna system integrity all can contribute to radio interface failures that effect the bottom line.

This NPRM proposes to require a signal booster operating in a mobile environment to power down (or shut off?) as the device approaches the base station. Some of the signal boosters on the market have existing gain control circuitry that could be enhanced to address this requirement. Unlike mobile handsets which constantly monitor both the serving BTS and its neighbors, signal boosters do not tabulate a list of multi-carrier signal strengths and bit error rates (BER) and adjust their transmissions for optimum emission/handoff. One wireless carrier proposes their authority to shut down a signal booster at any time. Another feature that is proposed and required of the signal booster is oscillation detection. When a signal booster antenna system does not have adequate physical isolation, electromagnetic oscillation can cause the booster to emit spurious signals (noise) which then manifests itself in base station performance issues.

Remote shut-off capability may be in the best interest of the wireless carrier but how will that effect the manufacturer and its business if the carrier does not utilize best practices in interference mitigation techniques?  In addition, the proposal to require signal booster operators to register their devices using a nationwide “clearinghouse” if managed efficiently could speed up interference resolution by providing licensees with a quick resource for identifying nearby signal boosters and points of contact. How do we handle the existing signal boosters?

The NPRM remarks that there appears to be some commonality between the proposals from AT&T, CTIA, and Wilson Electronics regarding the need for signal boosters to include a form of remote shut-off capability – that is a good thing. We need cooperation within the manufacturers and operators so that wireless networks operate at a high level. Given the need for more wireless spectrum and capacity issues right now, high quality coverage enhancing devices including signal boosters are a benefit to everyone.

LBA offers diagnosis and remedial services on engineering, intermodulation, and other interference issues affecting cellular, PCS and broadband systems.  To discuss technical interference issues, contact

About The Author

LBA Group, Inc. has 60 years of experience in providing RF asset solutions and risk management for industrial and telecommunications infrastructure assets.The group is comprised of LBA Technology, a leading manufacturer and integrator of radio frequency systems, lightning protection and EMC equipment for broadcast, industrial and government users worldwide; the professional consultancy Lawrence Behr Associates and LBA University, providing on-site and online professional training.The companies are based in Greenville, N.C., USA.

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