Mobile collaborative community (MCC) is an emerging technology that allows multiple mobile nodes (MNs) to perform a resource intensive task, such as large content download, in a cooperative manner. In this paper, we introduce a proxy-based collaboration system for the MCC where a content proxy (CProxy) determines the amount of chunks and the sharing order scheduled to each MN, and the received chunks are shared among MNs via Wi-Fi Direct. We formulate a multi-objective optimization problem to minimize both the collaborative content download time and the energy consumption in an MCC, and propose a heuristic algorithm for solving the optimization problem. Extensive simulations are carried out to evaluate the effects of the number of MNs, the wireless bandwidth, the content size, and dynamic channel conditions on the content download time and the energy consumption. Our results demonstrate that the proposed algorithm can achieve near-optimal performance and significantly reduce the content download time and has an energy consumption comparable to that of other algorithms.

We propose a contents-aware multicast (CAM) scheme in rate adaptive wireless networks. In CAM, transmission rate is determined depending on the contents type. That is, base layer packets are transmitted by the lowest rate for higher reliability. On the contrary, enhancement layer packets are sent by higher transmission rates. Moreover, enhancement layer packets are combined with base layer packets and redundantly transmitted, which allow higher decoding probability in error-prone wireless networks.