Carnegie Mellon University

Wireless Andrew

Wireless Andrew: Creating the World's First Wireless Campus

It's easy to imagine walking into your local coffee shop, ordering a latte, sitting down, and hopping online to check email, network with friends, or browse eBay. But a little over a decade ago the thought of wireless computing was, well, just a thought. That is, until Carnegie Mellon University got involved. Recognizing the impact of its Andrew project, which propelled the university to the position of the world's first wired campus, researchers launched Wireless Andrew, a multiple access-point, wireless local-area network (LAN) installation—an ambitious effort to turn Carnegie Mellon into the world's first wireless campus.

The Wireless Research Initiative: The Future of Wireless Computing

In 1993, researchers at Carnegie Mellon's Information Networking Institute (INI) started the Wireless Research Initiative, which was intended to support wireless research and to create a campus-wide user community and mobile computing laboratory. Their aim was to integrate various faculty projects concerning mobile computers and their ability to have continuous, high-speed Internet access. Dr. Alex Hills, founding director of the INI and the "Father of Wireless Andrew," explained, "The idea was to establish a research initiative at INI by pooling ongoing faculty projects to create something bigger." Quite the understatement, Hills' vision quickly evolved into a groundbreaking technological development, the Wireless Andrew project—a precursor to today's Wi-Fi networks.  

Wifi IllustrationIn the mid-1980s and early 1990s, wireless technology was just beginning to take shape. Although cellular phones were increasing in popularity, mobile computers (i.e. laptops) were relatively new and lacked the infrastructure to support the research projects and achieve Hills' vision. Wireless Andrew, so named because it both connects to and extends the Andrew network and because the name offers visibility in computing circles, fulfilled both tasks.

In 1994, after the INI secured a $500,000 grant from the National Science Foundation, the group approached AT&T to develop a wireless LAN system. The original objective was to cover parts of a few buildings—research labs, mainly—with radio-frequency transmissions. Following initial design setbacks, Carnegie Mellon researchers came up with a design methodology that blanketed Wean, Hamerschlag, and Porter Halls—the southwestern corner of campus. But Hills, enticed by his vision and positive feedback from colleagues, wondered how far he could expand the scope of the project.

Wireless Andrew Phase I: Connecting a Campus

By 1997, the INI and Carnegie Mellon's Computing Services Division had developed and made operational Wireless Andrew Phase I. Building on the campus' existing wired infrastructure, Phase I connected remote users to the Andrew system through 73 access points in six buildings—covering nearly half of the campus teaching, research, and office space. (1) The 900 MHz system transmitted via direct-sequence spread-spectrum radio that "chips" a signal into smaller pieces that are exchanged over a greater frequency and at a faster rate than a standard signal. Chipping also has the benefit of providing resistance to noise and interference because the signal uses a larger portion of the radio spectrum. (2)

Coinciding with the completion of Phase I, the Institute of Electrical and Electronics Engineers (IEEE) adopted its new 802.11 standard for wireless LANs. This standardization meant that equipment manufactured by different companies would be compatible and that, as production volumes increased, equipment and technical support would become less expensive. Hills decided that this was the time to move beyond NSF funding and seek private partnerships. In 1998, Carnegie Mellon teamed with Lucent Technologies (formerly owned by AT&T) and began work on Wireless Andrew Phase II—which replaced the original 73 access points and added another 278 access points, thereby covering Carnegie Mellon's academic campus. (3) During the summer of 2001, an additional 275 access points were installed in the residence halls, making the entire campus wireless.

Wireless Andrew Phase II: Expansion

Completed in 1999, Phase II operates on a 2.4 GHz band at a speed of up to 11 Mbps. The newer system transmits over a broader range of frequencies than the Phase I system. The result is that Phase II allows for faster, more-reliable connections. Although its performance is slower than the wired Ethernet system—which can run at a speed of up to 100-1000 Mbps—the advantage in mobility makes the system desirable. (4) Speed aside, Wireless Andrew was designed to provide the functionality and services of Carnegie Mellon's wired computing system to wireless users, researchers, and others on campus. To this end, it has succeeded.

On its completion in 1999, Wireless Andrew Phase II was supported by Lucent's two-fold WaveLAN technology: a network interface card, WaveLAN, and a network access point, WavePOINT. The WaveLAN card, installed in a PC, transmitted a radio signal to the access point, similar to how a cell phone transmits to a tower. The access point is a transmitter-receiver, which physically connects the wireless link to the wired network. At an estimated cost of $1,000 per access point (just for the hardware), an overriding development concern was achieving balance between network coverage and user capacity. A coverage-oriented design would reduce cost by minimizing the number of access points, whereas a capacity-oriented design would ensure adequate throughput for all users. (5) Although at times the respective designs appeared at odds, with careful planning and accurate measurements Carnegie Mellon researchers found equilibrium.

Development Challenges

Each access point had an estimated range of 800 feet outside and could handle 30-50 people running simple Internet connections—email, web browsing, or other tasks. But complicating issues included microwave ovens, concrete walls, and metal—from structural reinforcements to file cabinets—which interfere with radio frequency transmissions and reduce indoor coverage to 100-200 feet. Similarly, a higher number of users, such as in classrooms, lecture halls, and laboratories, strained the system and slowed connection speed. To combat these problems, the university staggered access points on adjacent floors in low- to medium-access areas, and varied frequencies on access points in high-occupancy areas. While there is no hard-and-fast rule for determining access-point location, at least a minimal overlap in coverage area is needed to guarantee connectivity as the user moves across campus and across access points.

In addition to the coverage/capacity balance, another concern during the project's development was user-cost. When Phase II was completed in 1999, the user needed to purchase a wireless card that plugged into a laptop and retailed for roughly $250. Now, virtually all laptops have wireless capability built in; for those that don't, network cards cost under $50 and are available at the campus bookstore.

The final dilemma was network security. Although wireless computing contains an inherently greater risk of unauthorized access than does wired computing, developers at Carnegie Mellon wanted to forge ahead with the project in the spirit of academic support. It should be noted, however, that Wireless Andrew users undergo a Kerberos-supported identification process prior to accessing any campus-sensitive material.

The Current State of Wireless Computing

Without the foresight of the INI, today's Wi-Fi computing environment would not exist. Wi-Fi is a wireless network that connects laptops, cell phones, and PDAs to the Internet. Following the example of Wireless Andrew, Wi-Fi networks rely on radio waves sent by network cards to routers or access points that are hardwired into an established Internet connection. Coffee shops, bookstores, airports, hotels, office buildings, college campuses, and other venues are increasingly Wi-Fi "hotspots."

As of 2006, there were 18,738 wireless cards registered to Carnegie Mellon users. Currently there are over 1,000 IEEE-802.11b, 11Mbps access points on campus, making it possible to connect in 40 academic, research, and administrative buildings, 36 residence halls, and four outdoor areas. In total, Wireless Andrew covers about four million square feet of interior space and 105 acres of campus. (6)

Through Computing Services, Carnegie Mellon offers extensive support for its wired and wireless campus technologies. Because roughly 99% of first-year undergraduates own computers, 83% of which are laptops, many students need help establishing network connections and determining which hardware is correct. The division maintains a phone line, online support, a walk-in office, and a website. Answers to frequently asked questions are posted on its website.

Tomorrow and Beyond

As for the future, Carnegie Mellon will attempt to repeat history by being one of the first research universities to embrace the latest standard for wireless LANs, IEEE 802.11n. 11n will offer speeds from 150 Mbps to 300 Mbps to wireless devices, speeds comparable to the current campus wired connections. "Today, we view Wireless Andrew as a complementary network to our campus wired network," explains Chuck Bartel, director of Network Services and project director for Wireless Andrew, "but with the speeds 11n will offer, we can start to consider Wireless Andrew as a replacement network for some of the applications now used on campus." The goal of the next-generation Wireless Andrew project will be to provide connectivity that will rival the wired connections on campus today so that researchers and the rest of the campus community can benefit from the latest technological advances in wireless communication.

--Douglas Phillips

Dr. Alex Hills and Charles Bartel contributed to this story.

Dr. Alex Hills is Distinguished Service Professor of Engineering & Public Policy and Electrical & Computer Engineering at Carnegie Mellon. Previously, he served as vice provost and chief information officer of the university. He is the founding Director of the Information Networking Institute and the founder of the Wireless Andrew project, which he led until 1999.

He is a researcher in wireless technologies and is affectionately known as the "Father of Wireless Andrew." For more information on the Wireless Andrew project and designing and building wireless networks, watch for Hills' forthcoming book.

Charles Bartel is the director of Network Services for Carnegie Mellon's Computing Services Division. He took over as director of Wireless Andrew in 1999.

AT&T spun off Lucent Technologies in 1997. In 2006, Lucent merged with Alcatel.  Alcatel-Lucent (NYSE: ALU) is headquartered in Paris, France. The company has offices in 130 countries.


1  Bartel, Charles R. and Bernard J. Bennington. "Wireless Andrew: Experience Building a High Speed, Campus-Wide Wireless Data Network." Proceedings of the 3rd Annual ACM/IEEE International Conference on Mobile Computing and Networking. Budapest (1997): 55-56.

2  Hills, Alex. "Terrestrial Wireless Networks." Scientific American, Inc. vol. 278, no. 4. (April 1998): 86-91.

3  See endnote 1.

4  Hills, A. "Large-Scale Wireless LAN Design." (Invited Paper) IEEE Communications Magazine. Vol. 39, no. 11. (Nov 2001): 98-104.
5  Hills, A. "Wireless Andrew." IEEE Spectrum. Vol. 36, no. 6. (June 1999): 49-53.
6  Statistics provided by the Computing Services Department.