Protocols for Adaptive Wireless and Mobile Networking

The goal of the Monarch Project1 at Carnegie Mellon University is to develop networking protocols and protocol interfaces to allow truly seamless wireless and mobile host networking. The scope of our efforts includes protocol design, implementation, performance evaluation, and usage-based validation, spanning areas ranging roughly from portions of the ISO Data Link layer (layer 2) through the Presentation layer (layer 6). In this article, we give a status report of our current work in the Monarch Project, placing it in the context of broader efforts by the Internet mobile networking community. Our work will enable mobile hosts to communicate with each other and with stationary or wired hosts, transparently making the most efficient use of the best network connectivity available to the mobile host at any time. To this end, the networking protocols must support adaptive operation in a number of ways. For example, host mobility means that protocols must be able to adapt packet routing to reach each mobile host in its current location. In addition, different wireless networks, intended for example for local-area, metropolitan-area, and wide-area use, make different tradeoffs in factors such as bandwidth, latency, error rate, and usage cost, providing different levels of quality of network connection with each wireless networking product or service. Network protocols should be able to adapt to optimize use of the best available network connection for each mobile host at any time. Further, in order to allow higher-layer protocols and applications to adapt to these changes in network connection quality, network protocols should be able to provide information to higher layers when such changes take place. We are experimenting with our protocols in the context of the “Wireless Andrew” infrastructure,currently being built at Carnegie Mellon [10]. The Wireless Andrew infrastructure builds on the current wired network infrastructure on campus, consisting mostly of 10-megabit per second Ethernet equipment. For high-speed wireless access on campus, we are installing an AT&T WaveLAN network covering most of the campus buildings [32]. WaveLAN uses direct-sequence spread spectrum radio in the 900 MHz ISM band to provide a raw data rate of 2 megabits per second. For wireless access off campus or where otherwise out of range of the WaveLAN network, we are using Cellular Digital Packet Data (CDPD) [4]. The CDPD service uses idle voice channels on the existing AMPS cellular telephone network to transmit data packets at a raw data rate of 19.2 kilobits per second.