Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences


UC Berkeley


2009 Research Summary


View Current Project Information

Eric Brewer, Richard Edward Honicky, Michael Demmer, Omar Mohammed Bakr and Kurtis Heimerl

Cell phones are by far the most successful modern technology in developing regions, with hundreds of millions of users in both India and China. Africa, which has wired telephony rates below 2%, is now the world's fastest growing cellular market with about 10% penetration. With continued adoption of current technologies, one can expect roughly 3 billion cellular users within this decade.

Yet even this remarkable expansion has its limitations. Many people living in rural areas have limited or no access to cellular coverage. Other users, both rural and urban, may have access to services, but only with unaffordable fees. Our aim in this project is to address these users and expand cellular usage by one more tier, to the next billion.

We argue that neither better rural penetration nor significantly reduced airtime costs are likely to happen in the near future simply through continued refinements to current technology. Therefore, our central idea is to build a phone that is "voice-message mostly," by which we mean that although the phone can make normal calls, its normal usage is to send and receive voice messages. Because such a system is based on asynchronous messaging, it addresses the two key barriers of penetration to the rural and urban poor:

First, it can extend the effective coverage range by queuing messages on the phone and leveraging user mobility to carry them into and out of connectivity, thereby reducing the required radio coverage area. Also, it should enable significantly lower airtime charges, as communication can be scheduled during times that would otherwise be idle. For existing deployments, this shift means that voice message traffic has little or no marginal cost to the carrier. For new deployments, it means that designers can tailor power and channel capacity for the average case instead of the peak case, and thereby reduce the scalability requirements for the infrastructure. In both cases, this savings can be passed on to the consumer.

We have prototyped this system and deployed it to rural Uganda. We are now in the process of iterating the design and partnering with communication specialists in Uganda to increase the scope of the project.