An asymmetric protocol for digital cellular communications

Abstract

Describes the design, validation, implementation and performance of an asymmetric link-layer protocol for a wireless link. The motivation for designing a new link-layer protocol is to obtain better performance in terms of end-to-end throughput and latency by correcting errors in an unreliable wireless link in addition to end-to-end correction rather than by correcting errors only by end-to-end retransmissions. The protocol described concentrates on asymmetry, although the concept of adaptive forward error correction is briefly introduced. The protocol also supports mobility. The asymmetry is needed in the design because the wireless terminals have limited power and smaller processing capability than the base stations. The key ideas in the design consist of placing the bulk of the intelligence in the base station as opposed to placing it symmetrically, in requiring the wireless terminal to combine several acknowledgments into a single acknowledgment to conserve power, and in designing the base stations to send periodic status messages, while making the acknowledgment from the wireless terminal event driven. The asymmetry in the protocol design results in a one-third reduction of the compiled code and a two-thirds reduction of processing overhead in the wireless terminal. Some performance results are also presented.