Using GPS Positioning and Time Synchronization in Mobile Networking

Soheila V. Bana and Pravin Varaiya

Abstract:	Lack of infrastructure brings two challenges to designing a mobile communication network (i) address resolution, and (ii) medium access control. Address resolution refers to providing a binding between the user personal ID and its communication address. An email address, soheila@eecs.berkeley.edu, is an example of a unique binding of a personal ID, soheila, and the Internet address, eecs.berkeley.edu. Medium access control refers to providing contention-free communication channel access to each user for transmitting data. We present an innovative design that relies on GPS positioning and time synchronization by every user. The design, Space/Time Division Multiple Access (STDMA), provides solutions to both problems of address resolution and medium access control. The scheme requires no infrastructure. The main requirement for a user, in addition to a GPS receiver, is prior knowledge of the geographical space and transmission time divisions. That is, we provide a map of the geographical area of the network to every user where the map divides the area into small cells. To every cell on the map we allocate a time slot for data transmission where time allocations are also known a priori to the users. A vehicle is aware of its position via a GPS receiver. Thus, every vehicle is aware of its allocated time slot. Furthermore, GPS time synchronization allows every vehicle to transmit data in its allocated time slot. This unique space/time allocation not only resolves the medium access issue for every user, but also solves the address resolution problem by allowing every user to transmit its personal ID and communication address. We provide a specific example of this scheme for a network of vehicles in an automated highway system. We explain the advantages and disadvantages of this scheme with respect to different applications. We also discuss the bandwidth efficiency of STDMA with respect to the GPS accuracy in time synchronization and positioning.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	100 - 105
Cite this article:	Bana, Soheila V., Varaiya, Pravin, "Using GPS Positioning and Time Synchronization in Mobile Networking," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 100-105.
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