Asymptotically-Optimal Incentive-Based En-Route Caching Scheme

Content caching at intermediate nodes is a very effective way to optimize the operations of Computer networks, so that future requests can be served without going back to the origin of the content. Several caching techniques have been proposed since the emergence of the concept, including techniques that require major changes to the Internet architecture such as Content Centric Networking. Few of these techniques consider providing caching incentives for the nodes or quality of service guarantees for content owners. In this work, we present a low complexity, distributed, and online algorithm for making caching decisions based on content popularity, while taking into account the aforementioned issues. Our algorithm performs en-route caching. Therefore, it can be integrated with the current TCP/IP model. In order to measure the performance of any online caching algorithm, we define the competitive ratio as the ratio of the performance of the online algorithm in terms of traffic savings to the performance of the optimal offline algorithm that has a complete knowledge of the future. We show that under our settings, no online algorithm can achieve a better competitive ratio than $\Omega(\log n)$, where $n$ is the number of nodes in the network. Furthermore, we show that under realistic scenarios, our algorithm has an asymptotically optimal competitive ratio in terms of the number of nodes in the network. We also study an extension to the basic algorithm and show its effectiveness through extensive simulations

Exploring Link Correlation for Performance Improvements in Wireless Networks

University of Minnesota Ph.D. dissertation. February 2017. Major: Computer Science. Advisor: Tian He. 1 computer file (PDF); x, 96 pages.In wireless communication, many technologies, such as Wi-Fi, BlueTooth and ZigBee, operate in the same ISM band. With the exponential growth of wireless devices, the ISM band becomes more and more crowded. These wireless devices compete with each other to access spectrum resources, generating cross-technology interference (CTI). Since cross-technology interference may destroy wireless communication, the field is facing an urgent and challenging need to investigate the packet reception quality of wireless links under CTI. In this dissertation, we propose an in-depth systematic study from empirical measurement, theoretical analysis, modeling, to design and implementation of protocols that exploit packet reception patterns of wireless links under cross-technology interference. Based on extensive measurements, we exploit link correlation phenomenon that packet receptions from a transmitter to multiple receivers are correlated. We then propose link correlation model which contradicts the widely made link independent assumption. The proposed model has a broad impact on network designs that utilize concurrent wireless links, which include (i) traditional network protocols such as broadcast, and (ii) diversity-based protocols such as network coding and opportunistic routing. In the study of the impact of link correlation model on traditional network protocols, we present the design and implementation of CorLayer, a general supporting layer for energy efficient reliable broadcast that carefully blacklists certain poorly correlated wireless links. We integrate CorLayer transparently with sixteen state-of-the-art broadcast protocols specified in thirteen publications on three physical testbeds running TelosB, MICAz, and GreenOrbs nodes, respectively. The experimental results show that CorLayer remarkably improves energy efficiency across a wide spectrum of broadcast protocols and that the total number of packet transmissions can be reduced consistently by 47% on average. In the study of the impact of link correlation model on diversity-based protocols, we propose link correlation aware network coding and link correlation aware opportunistic routing. In link correlation aware network coding, we introduce Correlated Coding which seeks to optimize the transmission efficiency by maximizing necessary coding opportunities. In link correlation aware opportunistic routing, we propose a novel candidate forwarder selection algorithm to help opportunistic routing fully exploit the diversity benefit of the wireless broadcast medium. Testbed evaluation and extensive simulation show that the traditional network coding and opportunistic routing protocols’ transmission efficiency is significantly improved with our link correlation model