Flex Your Symbol: A Case for Adapting Symbol Duration in Communication Systems

In wireless networks, different links often have different signal power to noise power ratios (SNRs). SNR affects the reliability and throughput of a link. Current wireless systems adapt transmission power, modulation or coding to improve reliability and throughput, based on link SNR. However, all these systems transmit a modulated symbol for a fixed duration across all links. Theory and systems research, alike, ignore symbol duration as a variable to optimize for reliability and throughput. This paper shows that by adapting symbol duration, wireless links can realize significant improvements in both reliability and throughput. We implement symbol duration adaptation for an orthogonal frequency division multiplexing (OFDM) system in a software-defined radio platform. The goodput gains depend on link SNR and the coding strategy. At low and mid SNR regimes, our system observes anywhere from 30% to 350% improvement in throughput. At high SNR regimes, as the link quality is already very high, symbol duration extension usually does not show a significant improvement. However, at all SNRs, the ability to extend the symbol duration increases link reliability in terms of packet reception ratio. This work has deep implications to network architecture and analysis, some of which are detailed in this paper.