A group handoff scheme for the proximity service of sharing mobile data downloading

In this work, a group handoff scheme from a mobile AP to a fixed AP and vice versa for downloading and sharing of group touring's Points of Interests (POIs) based on the concept of proximity service were proposed. In a group touring scenario, the tour guide enables the Wi Fi hot spot service of his own handheld device, which plays the role of mobile proxy and mobile AP (m-AP), and each tourist has his handheld device to connect with the m-AP of the tour guide's handheld device. The tour guide's handheld device can download the corresponding POIs' contents from the server through the 4G cellular network and then forward these contents to all members' handheld devices using the Wi Fi Device-To-Device (D2D) communication paradigm. Related control messages are based on the Machine-To-Machine (M2M) communication paradigm such that the downloading and sharing of POIs are automatic and user transparent. In this way, it can save the 4G cellular network's expense and reduce the traffic in the 4G cellular network. Moreover, when a POI provides free Wi Fi services through a fix APs (f-APs) to users, all of the group members' and tour guide's handheld devices can switch to the f-AP when they are inside the POI and then switch back to the m-AP of the tour guide's handheld device when they move out of the signal coverage of the f-AP. In this way, it can further save the 4G cellular network's expense and reduce the traffic in the 4G cellular network. Two control schemes called conservative and aggressive modes were proposed to handle the handoff from m-AP to f-AP mode and vice versa. An Android system is implemented and some performance analysis were evaluated to measure downloading volume, downloading times and packet delivery ratio.