In this paper, we present the Connected Consumption Network (CCN) that allows a community of consumers to collaboratively sense the market from a mobile device, enabling more informed financial decisions in geo-local context. The mobile application allows one to log one's wish list and itemized list of transactions to form a social network around the list of interests. Individuals can share this data to inform and guide others in a timely, personal and contextual manner when they are shopping for a product or seeking a service. It can also help people connect opportunistically in a local area to make group purchases, to pick up an item for a friend, and to perform reverse auctions. We present the design, architecture and concept prototype. We simulate a social network with three months of existing credit/debit card transaction data in various geographical areas to analyze the mutual information and recommendations that can be shared among networked consumers.

In this demonstration we present SnapN'Share, the first sample application of a new platform implementing a wireless, peer-to-peer information system that bypasses the need for any centralized servers, coordination, or administration. SnapN'share runs on wireless pocket devices as well as stationary computers, and enables users to generate and seamlessly share content with different groups and communities that they belong to, as they come into close vicinity of their peers. At CCNC'08 we demonstrate the capabilities and features of the system, as well as its advantages when compared to traditional central-infrastructure based platforms.

Given a mobile mesh network, we attempt to address the question of which nodes are accessible at any point in time through some path from a given node. From the viewpoint of some node in the mesh network, we claim that it is impossible to deterministically infer which other nodes are still accessible through some path from the current node. By formulating the arrival of presence updates from various nodes in the network as a Poisson process, we introduce a probabilistic presence mechanism that offers user-defined levels of assurance on whether a remote node is still accessible and provide a distance metric for each node, based on the corresponding arrival rate of presence updates.

Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. However, most of the proposed solutions require distributed space-time coding algorithms, the careful design of which is left for future investigation if there is more than one cooperative relay. We propose a novel scheme that alleviates these problems and provides diversity gains on the order of the number of relays in the network. Our scheme first selects the best relay from a set of M available relays and then uses this "best" relay for cooperation between the source and the destination. We develop and analyze a distributed method to select the best relay that requires no topology information and is based on local measurements of the instantaneous channel conditions. This method also requires no explicit communication among the relays. The success (or failure) to select the best available path depends on the statistics of the wireless channel, and a methodology to evaluate performance for any kind of wireless channel statistics, is provided. Information theoretic analysis of outage probability shows that our scheme achieves the same diversity-multiplexing tradeoff as achieved by more complex protocols, where coordination and distributed space-time coding for M relay nodes is required, such as those proposed by Laneman and Wornell (2003). The simplicity of the technique allows for immediate implementation in existing radio hardware and its adoption could provide for improved flexibility, reliability, and efficiency in future 4G wireless systems.

This paper presents a design principle that helps guide placement of functions among the modules of a distributed computer system. The principle, called the end-to-end argument, suggests that functions placed at low levels of a system may be redundant or of little value when compared with the cost of providing them at that low level. Examples discussed in the paper include bit-error recovery, security using encryption, duplicate message suppression, recovery from system crashes, and delivery acknowl-edgment. Low-level mechanisms to support these functions are justified only as performance enhance-ments.

Synchronization of accesses to shared data and recovering the state of such data in the case of failures are really two aspects of the same problem--implementing atomic actions on a related set of data items.In this paper a mechanism that solves both problems simultaneously in a way that is compatible with requirements of decentralized systems is described.In particular, the correct construction and execution of a new atomic action can be accomplished without knowledge of all other atomic actions in the system that might execute concurrently.Further, the mechanisms degrade gracefully if parts of the system fail: only those atomic actions that require resources in failed parts of the system are prevented from executing, and there is no single coordinator that can fail and bring down the whole system.

In this paper, a new approach to coordinating accesses to shared data objects is described. We have observed that synchronization of accesses to shared data and recovering the state of such data in the case of failures are really two sides of the same problem—implementing atomic actions on multiple data items. We describe a mechanism that solves both problems simultaneously in a way that is compatible with requirements of decentralized systems. In particular, the correct construction of a new atomic action can be done without knowledge of all other atomic actions in the system that might execute concurrently. Further, the mechanisms degrade gracefully if parts of the system fail—only those atomic actions that require resources in failed parts of the system are prevented from executing.

The design of computer systems to be concurrently used by multiple, independent users requires a mechanism that allows programs to synchronize their use of shared resources. Many such mechanisms have been developed and used in practical applications. Most of the currently favored mechanisms, such as semaphores and monitors are based on the concept of mutual exclusion.