Can You Hear Me Now . . . ?
Improving Cell Phone Coverage at MIT

Robyn Fizz, Joan Cyr, Jerrold Grochow

Over the past decade, cell phones have become essential to life at the Institute, both for daily business and the many research projects that focus on mobile devices. They can also serve as a critical source of communications during an emergency. Given the ubiquity and importance of mobile devices at MIT, why are cellular signals on campus so variable?

Imagine these three scenarios – which all happen to be true.

• Sprint Nextel leases space for a cell tower on the rooftop of a building near the MIT campus. When the building is sold, the new owner asks Sprint to remove the transmitter.  As a result, cellular coverage with this carrier declines on West Campus. Sprint Nextel engages MIT to search for a new site, and testing pinpoints the top of Building NW14. However, siting the transmitter at this “ideal” location would interfere with sensitive research being conducted inside the building.

• An MIT researcher is developing an in-car system for finding destinations – such as nearby restaurants or local museums. To test his system, he needs reliable cellular coverage in one of the parking levels beneath the Stata Center. Unfortunately, as he discovers, the penetration of cell signals below ground is very limited. 

• On the main campus, MIT constructs Building 6C, an “infill” structure noted for its vibrant atrium floor by Sol LeWitt. As the building rises, the strength of cell signals in surrounding buildings drops significantly.

Say What?

Let’s take a closer look at our three scenarios to zero in on some of the challenges.

• The dragged-out tale of the West Campus transmitter underscores the fact that cellular carriers are the primary factor in this equation. While MIT operates its own networks – including the wireless network for computer communications and the on-campus phone system, now being converted to voice over IP (VoIP) technology – it does not operate its own cellular service. Coverage on campus has been totally dependent on the cellular companies – until recently. (See Bridging the Gaps, below, for how we can now have some impact.)

You might think the MIT name would carry weight with cellular service providers – and to some extent it does. MIT receives special pricing from Verizon Wireless and Sprint Nextel, and also has contracts with T-Mobile and AT&T. Still, with only about 600 business accounts each with Verizon and Sprint Nextel, and even fewer with AT&T and T-Mobile, MIT is hardly a big customer.

The rooftop scenario also illustrates how complicated it can be to site cell towers on campus. Care must be taken to ensure that radio frequencies from transmitters don’t disrupt MIT research. And negotiations for transmitters involve not only the cellular carriers and various MIT departments – Facilities, Information Services & Technology (IS&T), Procurement, and the Office of the General Counsel – but also the City of Cambridge, which grants permits for visible or rooftop structures.

• The researcher’s dilemma in the Stata garage highlights the difficulty of getting cellular coverage in underground locations. This is especially true when the structures are made of cement. Even above ground, signals may be weak or nonexistent in many inside locations. Several materials can impede outside signals from penetrating building exteriors. These include titanium outer shells, filtered glass windows, and older buildings with thicker walls and heavy infrastructures.

• As Building 6C demonstrates, new construction in close proximity to other buildings can affect the path of cellular signals. Shadowing by buildings can weaken or block signals that used to get through. MIT’s building boom has benefited the community in many ways, but has not been a plus in the cellular realm.

Clustered buildings (or clusters of people) can also cause unexpected voids in cellular coverage. This occurs when a large number of mobile devices vie for the same carrier signals in a small space. Just picture Killian Court on Commencement Day.

In physical terms, then, there are several reasons why cellular coverage may be degraded or nonexistent at different places and at different times.

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Contributing Factors

Beyond buildings, signals, and transmitters, other factors complicate the cellular environment at MIT.

• Multiple carriers: As noted, MIT does business with four cellular carriers: Verizon Wireless, Sprint Nextel, T-Mobile, and AT&T. The FCC licenses different signal frequencies for each carrier, so each needs to install and operate its own transmitters. And each carrier requires a separate contract with MIT for use of additional equipment to improve its signal inside buildings. Dealing with four service providers, rather than having leverage with one, makes it that much harder for MIT to resolve coverage issues on campus.

• The moving target of technology: New smartphones and platforms – such as Apple’s iPhone, Google Android, and Cisco’s Mobility Services Engine – may change the cellular landscape. Many analysts expect a migration of services to a converged platform using the IP data network. For now, with technology in flux and budgets being squeezed, investments in cellular solutions need to be targeted and pragmatic.

• Limited resources: To date, no department or group at MIT has been given the mandate or resources (dollars, people, and real estate) to tackle the challenge of ensuring consistent cellular coverage across campus. Resources from cellular carriers have also been scarce.

Bridging the Gaps

IS&T has become the “go-to” group for telephone issues on campus, since IS&T provides the traditional and MITvoip phone services on campus. IS&T has heard a growing chorus of complaints from mobile device users on campus; it’s clearly a frustrating experience for everyone. While IS&T does not control cellular service on campus, it has taken several steps to try to improve the situation.

•  IS&T continues to work with cellular carriers to install outdoor transmitters on campus. Since outside cell signals often permeate building interiors, new transmitters will have the biggest impact on improving cellular coverage on campus.

The transmitter for West Campus is high on the priority list, since Campus Police, the Athletics Department, and other MIT service groups are Sprint Nextel customers. MIT is now negotiating with Sprint Nextel to install a transmitter on the roof of the Johnson Athletic Center – a location that will also boost signals for MIT’s “dormitory row.” To improve its coverage for the center of campus, Sprint Nextel plans to install a pair of transmitters on E17 and E19.

Plans for a new AT&T transmitter on or near Building 37 are moving forward. This installation will improve coverage for all AT&T customers on campus, including iPhone users.

• To bring interior signals up to satisfactory levels, IS&T led the installation of a multi-carrier, in-building Distributed Antenna System (DAS) in the Stata Center, plus its extension to the Broad Institute and the new Ashdown Dormitory (NW35). This type of system uses a group of antennas to capture and relay cellular signals, though at a very high cost. For example, MIT paid almost $250,000 for the Stata DAS.

IS&T has also been involved in installing small, single-carrier, in-building Distributed Antenna Systems in E40, 46, and the Bates Linear Accelerator Center. However, setting up these systems in multiple locations throughout MIT is not a viable solution: in larger numbers, they affect negatively the networks of cellular carriers.

• IS&T has assembled a team to evaluate other promising technologies. Of particular interest are

– Dual-mode handsets. Devices such as T-Mobile’s Unlicensed Mobile Access (UMA) phones allow users to roam by providing a seamless transition between MIT’s wireless network and the carrier’s cellular network. Among its advantages, UMA technology addresses coverage issues in underground spaces.

– Fixed mobile convergence (FMC). This technology fuses WiFi, cellular, VoIP telephony, and location-awareness technology, and supports all cellular carriers. FMC technology provides MIT with the opportunity to leverage its campuswide WiFi network and recent investment in VoIP technology. This fall, in a joint collaborative effort with Agito Networks and Cisco, IS&T plans to conduct an evaluation of Agito’s mobility router and Cisco’s wireless services engine, using the recently upgraded MIT wireless network.

These technologies, along with new transmitters, hold the most promise for taming MIT’s cellular challenges. Even so, to make the best use of new solutions, it will be important for individuals to choose carriers and mobile devices that are in line with MIT's recommendations.  

With mobile devices so central to today’s communications, it’s important that the Institute throw its weight behind improving cellular coverage. It will take vision, resources, and a spirit of collaboration to bring strong signals to all corners of campus.

Click here for a list of Cellular Resources from IS&T.

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