This paper presents and discusses the idea that one reason for the success of collaborative problem solving is the polyphonic character of work in small groups. Polyphony, a concept taken from music, may occur in chats for problem solving, transforming dialog into a “thinking device”: Different voices jointly construct a melody (story, or solution) and other voices adopt differential positions,...

In this channel,we study rate region of a Gaussian two-way diamond channel which operates in half-duplex mode. In this channel, two transceiver (TR) nodes exchange their messages with the help of two relay nodes. We consider a special case of the Gaussian two-way diamond channels which is called Compute-and-Forward Multiple Access Channel (CF-MAC). In the CF-MAC, the TR nodes transmit their mes...

abstract—in this paper, the problem of secure transmission in two-hop amplify-and-forward (af) systems with an untrusted relay is investigated. to prevent the untrusted relay from intercepting the source message and to achieve positive secrecy rate, the destination-based cooperative jamming (dbcj) technique is used. in this method the destination sends an intended jamming signal to the relay. t...

Problem statement: WiMAX relay is an emerging cost effective wireless last mile solution for rural and urban broadband Internet access. Approach: One of the key concerns of WiMAX operators is how many users they can support for an access area where the number of users and the amount of data that can be delivered to the end user depends on the available system capacity. Results: This scenario is...

We consider the problem of delivering popular streaming media to a large number of asynchronous clients. We propose and evaluate a cache-and-relay end-system multicast approach, whereby a client joining a multicast session caches the stream, and if needed, relays that stream to neighboring clients which may join the multicast session at some later time. This cache-and-relay approach is fully di...