Network-Coding-Based Content Sharing for Mobile Devices via Multiple Relays of WiFi Direct

Sharing content, such as video, with others via personal mobile devices has become more and more popular. However, it tends to incur extremely high traffic fee to share large files in commercial networks. In this paper, we propose an efficient network-coding-based content sharing scheme (NCCSS) for mobile devices via WiFi Direct. When the file owner wants to share a file to others, it equally splits the file into multiple pieces, and then linearly encodes the pieces into segments with random linear network coding (RLNC). After that, it switches itself to an access point (AP), and waits to accept request from other devices. For each device in the network, it connects to the AP, and requests linearly independent segments. After it has received a fixed number of encoded segments, it switches itself to a new AP to enlarge the coverage of sharing. By strategically switching devices between the AP mode and ordinary mode, all devices could receive sufficient segments and recover the original file. NCCSS was evaluated in a real-world testbed consisting of 20 mobile devices. The experimental results show that compared to the traditional replication-based transmission scheme and erasure-coding-based transmission scheme, NCCSS could provide higher sharing rate.