Minsik Hwang

Design and implementation of a fast handoff scheme supporting vehicular mobility over IEEE 802.11 WLAN

The wide spread deployment of IEEE 802.11 based wireless local area network (WLAN) and its ability to provide low cost as well as high speed Internet access attract the information technology (IT) practitioners to utilize the WLAN to also serve mobile stations with vehicular speed. However, there are some issues in its realization due to significant amount of time required to finish handoff process and small coverage area of WLAN access point (AP). To cope with these issues, we propose a network assisted fast handoff scheme. The information of AP is stored in the server, thus by requesting this information a user knows the working channel of AP. In addition, we suggest a cluster based network architecture, in which the APs in a single cluster are assigned the same BSSID. These two techniques allow only channel switching during the handoff process. We also propose a semi-static IP address allocation for efficient handoff between APs with different subnet addresses. This reduces the delay caused by the DHCP process during the L3-handoff. We have implemented the proposed handoff scheme using existing devices and evaluated its performance through experiments. It is shown that the proposed handoff scheme outperforms the legacy handoff in terms of handoff delay as well as throughput.

Design and implementation of a lightweight data dissemination protocol for V2V communications

IEEE 802.11 b/g/n enabled devices are popular and widely used to provide wireless network access. Therefore, it is often considered for configuring networks for vehicles. However, because of its short signal coverage and long link setup latency, this standard cannot be used directly to support vehicle-to-vehicle (V2V) communications. In this paper, a lightweight data dissemination protocol is proposed to tackle the aforementioned issues. By utilizing a management frame format of IEEE 802.11 for data transmission, the devices can directly communicate with each other without a prior link setup process. Moreover, it supports multihop transmission to deliver data to out of its transmission range through relay nodes. The proposed protocol has been implemented in commercial devices and evaluated in a real vehicular network environment. The experimental results show that it is able to support seamless data dissemination through multihop communications in vehicular environments.