Enhancing the Wi-Fi Direct protocol for Vehicular Ad-hoc Networks

Abstract

We present a technique for enhancing Wi-Fi Direct (WD) for vehicular environments. Dedicated short range communication (DSRC) has been standardized for communication in Intelligent Transportation Systems (ITS). However, due to high costs at initiation, alternative communication strategies are of interest in order to facilitate the quick deployment of ITSs. WD, which is a relatively mature technology available in mobile devices, has come across as a possible alternate candidate. However, the presence of large communication delays in the WD protocol stack is a shortcoming in deploying this in highly dynamic vehicular scenarios. The objective of our work is to propose and evaluate a method to overcome some of the large transmission delays in WD. Our proposal is to use a broadcast mechanism in the downlink between the group owner (GO) and the clients of a WD group, as an alternative to the currently used peer-to-peer (P2P) method. We study our technique by simulating a bi-directional highway scenario with multiple lanes. We set up the vehicular channel model using two well-known models: Friis propagation model and the Nakagami fading model. Performance measures such as average total delay, average energy consumption of the GO, average packet loss ratio, and average packet reception ratio are presented. While the proposed GO Broadcast method reduces the downlink delay, it increases the probability of packet losses due to the lack of retransmissions. Our results demonstrate a gain in terms of average total delay and the average energy consumption of the GO. We use a theoretical analysis as well as a simulation study using OMNeT-r-K It is also shown that the degradation in performance on the downlink due to packet losses is within tolerable limits, given that the size of the group is selected properly.