Value aware wireless protocol design.

摘要

In this work we show that awareness of the value of application data at lower layers of wireless protocol stack can lead to better protocol decisions resulting in enhanced application performance. We demonstrate the validity of the above premise by customizing many pre-existing mechanisms of the MAC and PHY layers of wireless protocols.;The success of the various mechanisms presented in this thesis are a result of two observations, first, not all data bits are created equal. For example, in a video application, I-frame bits are typically more important than P- or B-frame bits. Hence, an application developer would like to ensure a "differential prioritization" of application data based on its criticality to application performance. Over years application developers have implemented systems which provide differential prioritization by encoding data (video and audio) in a manner that optimizes the delivery probability of critical data by increasing the amount of redundancy in the content.Various layers of a typical protocol stack, then attempt to encode this bit stream into packets, frames, and signals, such that overall losses during the delivery process is mitigated.;The work presented in this thesis is complimentary to above mechanisms and is guided by our second observation, that the specific data delivered and the time and sequence with which it is delivered across network are affected by multiple protocol decisions that are taken at various layers of network stack. In particular there are many pr-existing functionalities at different layers of MAC and PHY layers of wireless networking stack which can be modified to enhance the performance of applications.;In this dissertation, we present multiple modifications to existing functions at the PHY and MAC layers of a wireless link to achieve differential prioritization for different units of data as desired by an application. Specifically we present Apex and Medusa, PHY and MAC layer schemes respectively for optimizing performance of media delivery. We also present MOM , a PHY layer scheme for improving delivery performance of non-media application such as file transfer, web browsing etc., by providing wireless PHY layer differential prioritization to application data.