A social-based routing protocol for opportunistic networks considers the direct delivery as forwarding metrics. By ignoring the indirect delivery through intermediate nodes, it misses chances to find paths that are better in terms of delivery ratio and time. To overcome this limitation, we propose to incorporate transitivity, which considers the indirect delivery through intermediate nodes, as one of the forwarding metrics. We also found that some message forwards do not improve the delivery performance. To reduce the number of these useless forwards, the proposed scheme forwards messages to an encountered node when the increase of total utility value is greater than a threshold. Using a simulator with real world trace data sets, we compare the proposed scheme with the existing protocols, epidemic routing and SimBetTS. Compared with SimBetTS, the proposed scheme increases delivery ratio by 1.5 percent and decreases delay time by 2 percent while reducing overhead by 30 percent.

In this paper, we propose QoS-constrained peer selection and nondisruptive rate adaptation schemes with considering shared bottleneck problem to provide a stable peer-to-peer live video streaming service during vertical handoff. In the proposed scheme, a QoS-constrained peer is selected by estimating bandwidth with active probing, and a reception rate converges to a stable state without any QoS degradation with help of multi-path handoff. The shared bottleneck problem is addressed by adjusting the estimated bandwidth and yielding the redundant bandwidth usage.

One of the most evident characteristics of an ad hoc ubiquitous computing environment is the dynamism of connections. Due to the mobility of nodes, paths between communicating peers change over time and hence should be discovered continually. Applications also dynamically discover available services and replace connections to provide contextually more appropriate services. In such an environment, the reduction of discovery cost and the reflection of context are main design factors. In order to avoid discovery cost being paid by both application and routing layer and to delay a service binding until forwarding time, we propose a shim layer called shared generic routing (or SGR) that discovers paths by accommodating application layer labels as well as IP addresses as routing targets and manages forwarding states. On top of SGR, IP and application layer routing can be efficiently implemented. Through simulation, we show that SGR can effectively remove duplicated discovery efforts.