This paper presents 7DS, a novel peer-to-peer data sharing system. 7DS is an architecture, a set of protocols and an implementation enabling the exchange of data among peers that are not necessarily connected to the Internet. Peers can be either mobile or stationary. It anticipates the information needs of users and fulfills them by searching for information among peers. We evaluate via extensive simulations the effectiveness of our system for data dissemination among mobile devices with a large number of user mobility scenarios. We model several general data dissemination approaches and investigate the effect of the wireless coverage range, 7DS host density, query interval and cooperation strategy among the mobile hosts. Using theory from random walks, random environments and diffusion of controlled processes, we model one of these data dissemination schemes and show that the analysis confirms the simulation results for this scheme.

This paper presents 7DS, a novel peer-to-peer data sharing system. 7DS is an architecture, a set of protocols and an implementation enabling the exchange of data among peers that are not necessarily connected to the Internet. Peers can be either mobile or stationary. It anticipates the information needs of users and fulfills them by searching for information among peers. We evaluate via extensive simulations the effectiveness of our system for data dissemination among mobile devices with a large number of user mobility scenarios. We model several general data dissemination approaches and investigate the effect of the wireless coverage range, 7DS host density, query interval and cooperation strategy among the mobile hosts. Using theory from random walks, random environments and diffusion of controlled processes, we model one of these data dissemination schemes and show that the analysis confirms the simulation results for this scheme.

Abstract-Our goal is to explore characteristics of the wireless environment that provide opportunities for caching, prefetching, coverage planning, and resource reservation. We conducted a one-month measurement study of locality phenomena among wireless web users and their association patterns on a major university campus using the IEEE 802.11 wireless infrastructure.We evaluate the performance of different caching paradigms, such as single user cache, cache attached to an access point (AP), and peer-to-peer caching. In several settings such caching mechanisms could be beneficial. Unlike other measurement studies in wired networks in which 25% to 40% of documents draw 70% of web access, our traces indicate that 13% of unique URLs draws this number of web accesses. In addition, the overall potential ideal hit ratios of the user cache, cache attached to an access point, and peer-to-peer caching paradigms (where peers are coresident within an AP) are 51%, 55%, and 25%, respectively.We distinguish wireless clients based on their interbuilding mobility, their visits to APs, their continuous walks in the wireless infrastructure, and their wireless information access during these periods. We model the associations as a Markov chain using as state information the most recent AP visits. We can predict with high probability (86%) the next AP with which a wireless client will associate. Also, there are APs with a high percentage of user revisits. Such measurements can benefit protocols and algorithms that aim to improve the performance of the wireless infrastructures by load balancing, admission control, and resource reservation across APs.

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