Unlicensed boosters could improve reception but could also increase interference

When you’re trying to make a cell phone call, have you ever been thwarted by those pesky laws of physics? You know, those ones that cause signals to fade at long distances from base stations or impede signals in tunnels, buildings or dense foliage. If so, the FCC thinks it may have an answer to your problems – wireless consumer signal boosters. While signal boosters have been an option for certain FCC wireless licensees for a while, the FCC recently issued a Notice of Proposed Rulemaking (NPRM) kicking off a proceeding designed to allow individual consumers to purchase and use such boosters. 

The NPRM was released both in response to a number of petitions filed by private parties and as part of the Commission’s overarching effort to deploy wireless and broadband services. In it, the Commission recognizes not only the potential value in signal boosters, but also the significant potential for interference created by poorly designed or installed boosters. To attempt to ensure that boosters are deployed effectively and safely, the Commission proposes to impose requirements on the manufacture and marketing of boosters themselves, rather than adopting a licensing regime for their use. The NPRM seeks comment generally on this approach, as well as on a number of more discrete issues.

The type of wireless signal booster contemplated by the NPRM is essentially a system consisting of an inside antenna paired with an amplifier and an outside antenna. The inside antenna communicates with the user’s cell phone or other wireless device and the outside antenna with a wireless service provider’s base station, with the amplifier boosting the signal to improve the connection.  Such boosters could be designed for either fixed use, such as in a building or tunnel, or mobile use, such as in a car. The NPRM notes that such devices would be particularly useful in rural areas where wireless coverage gaps exist, and in other difficult-to-serve indoor areas. Signal boosters could also provide public safety benefits by allowing users to connect to 911 and emergency services where their wireless signals would otherwise be blocked (e.g., tunnels, garages, inside buildings). 

While the benefit of wireless signal boosters seems clear, their use also creates a number of potential problems. The FCC identified five primary issues in the NPRM, four of them involving different types of interference. Those four types of interference are:

  • “Near-far” interference. This type of interference arises when a signal booster is closer to a base station on an adjacent channel than to the base station with which it is attempting to communicate. In some applications, particular mobile, an improperly designed booster may amplify and interfere with communications on that adjacent channel.
  • Oscillation. This arises when the booster’s signal level remains elevated as it approaches the base station with which it is communicating, creating an effect similar to that of moving a microphone too close to a speaker.
  • Base station overload. This affects base stations that use dynamic power control to maximize performance by adjusting the power of both the base station and the handsets with which they are communicating. Boosters which are not dynamically controlled by the base station may continue to provide amplification when it is not necessary, interfering with the base station’s efficient operation and potentially causing an overload.
  • 800 MHz spectrum interference. This arises in the 800 MHZ spectrum band, where channels used commercially, primarily by Sprint Nextel, are interleaved with public safety channels. Unless there is proper coordination between the two, use of a wideband signal booster by either type of user may overload base stations operating on the adjacent channels, causing dropped calls and reduced network capacity. 

The fifth booster-related problem identified in the NPRM is not an interference problem, but a distortion of network-based E- 911 systems. These systems determine the location of handsets used to call 911 by measuring the time it takes for the handsets signal to reach units installed at the operators’ base stations. If the handsets signals are amplified by a signal booster, this may lead to inaccurate location estimates. 

The Commission in the NPRM discusses some “real-world” examples of these problems identified by Verizon, AT&T, and other operators, noting that the interference issues can have wide-ranging effects, sometimes entirely disabling a base station. According to the NPRM, operators claim that it is often extremely difficult to identify a specific signal booster as the source of these problems, particularly where the signal booster may be used in a mobile setting. 

Despite these issues, the Commission believes that there is a genuine need for “well-designed” signal boosters. It therefore proposes a regulatory regime which will allow for their use while avoiding the various harms they may cause. The Commission’s proposal is to regulate consumer signal boosters through a “license by rule” regime. Under such a regime, no individual licenses are issued for consumer signal boosters; rather, rules are adopted setting the technical parameters such boosters must satisfy before being marketed or sold. The NPRM generally seeks comment on whether this type of regulation is appropriate for signal boosters. Assuming this is the appropriate means by which to regulate boosters, the NPRM provides the broad outlines of its proposed technical requirements, seeking further comment on the appropriateness of these requirements. 

First, the NPRM proposes requiring all signal boosters operated in a given band to satisfy the existing technical requirements (e.g., power, out-of-band emissions) for mobile units (not base stations) operating in that band. The NPRM also proposes requiring signal boosters to be designed to “self-monitor” to ensure their compliance with these rules and to automatically shut down if they detect any non-compliance. Similarly, boosters would be required to automatically shut-down if they were to detect any feedback or oscillation. The NPRM requests comment on:  the effectiveness of such a requirement; the appropriate specific triggers for shut-down; and whether a booster’s power should be measured by effective radiated power (ERP) or transmitter output power.

The NPRM proposes to ensure compliance with radiofrequency (RF) exposure limits through existing procedures, requiring all applications for equipment authorization for signal boosters to demonstrate compliance with the RF exposure limits applicable to the device’s intended use. As with existing devices, the NPRM proposes requiring labeling and clear instructions for end users regarding appropriate use and installation of signal boosters. 

In addition to labeling related to potential RF exposure, the NPRM proposes requiring labeling regarding the responsibility of the signal booster owner and installer to ensure that the booster does not cause interference and, for fixed boosters, to coordinate the booster’s installation and use with the appropriate local wireless carrier. The NPRM proposes that for fixed boosters, this label include reference to an FCC website where licensee information will be available (www.fcc.gov/signalboosters – as of this writing, this site is not active). 

The NPRM further proposes requiring the operator of any signal booster to immediately cease operations if the booster is causing harmful interference. The NPRM also seeks comment on whether and how signal boosters should be regulated to prevent interference between and among boosters themselves. 

In addition to the above proposals, which would apply to all signal boosters, the NPRM proposes additional requirements that would apply only to fixed or mobile boosters. The NPRM would require that all fixed signal boosters coordinate frequency selection and power levels with local wireless carriers before use; it seeks comments on what specific coordination procedures should be required. The NPRM specifically asks how, under any coordination procedure, to ensure that the wireless carrier responds to any coordination requests in a timely manner. 

The Commission recognizes that for mobile signal boosters, the type of advance coordination appropriate for fixed boosters may be impossible. Rather than requiring such coordination, the NRPM proposes requiring mobile boosters to automatically reduce power as they approach the base station with which they are communicating; it also seeks further comment on how to address interference concerns, particularly the “near-far” interference issue identified above. 

The Commission also generally requests comment on any other issues related to signal boosters, in particular seeking input on whether, and if so how, it should require remote shut-off capability, location detection features, and activation of boosters by wireless carriers before use. Recognizing that signal boosters are already in use in many areas, the Commission requests comment on how to treat these existing boosters, suggesting that it may allow their use to continue, at least for some period of time, although it might require that they be registered. 

The Commission also notes that many wireless providers have expressed concerns that interfering boosters are often difficult to locate. Accordingly, the NRPM proposes setting up a national clearinghouse for registration of boosters and suggests including features in boosters that would prevent them from operating unless they were first registered in this clearinghouse.

Finally, the NPRM proposes some additional requirements that would apply only to non-consumer signal boosters operated by wireless licensees under Part 90 of the Commission’s Rules. Under Part 90, certain signal boosters have been allowed since 1996, generally for internal, non-public communications. The NPRM generally proposes to retain the existing rules for such Part 90 boosters, with certain modifications to prevent interference. Although narrower in application than the changes proposed in the rest of the NPRM, any parties who currently operate Part 90 boosters should review these proposals. 

Comments will be due to the FCC 45 days after the NPRM is published in the Federal Register, with reply comments due 30 days later. Check back here for updates on that front.