Vehicular networks are highly mobile wireless networks that can provide wide variety of services and applications such as public safety communications, crash avoidance, multimedia and Internet access in highways. Designing routing algorithm in vehicular network is a challenging task due to rapidly changing topology and high speed mobility of vehicles. One of the critical issues of vehicular network is frequent path disruptions caused by high speed mobility that leads to broken links which results in low throughput. This poses complex challenge in ensuring quality of service (QoS). A lot of research around the world is being conducted to define the standards for vehicular communication. In this paper, we study the effect of different duration of transmitting packet and compare different packet size on sending and received packet rate in IEEE 802.16j MMR networks using NCTUns. Meanwhile, cross-layer routing approach is proposed to overcome the challenge. The routing approach is expected to significantly improve QoS in vehicular networks.

In mobile communication, routing data through intermediate mobile node is a challenging task due to high mobility of nodes which causes rapid change in network topology and frequent disconnection between pair of nodes. To address these issues, Mobile Relay Station (MRS) is introduced into the network based on IEEE 802.16j standard. The MRS features are similar to the Fixed Relay Station (FRS), however the MRS has capability to move as Mobile Station (MS). In intermittent connection, by adapting the features of Delay Tolerant Network (DTN), the MRS can store and carry the data until it find the destination to forward the data. Assuming that MS is aware of its' own movement as well as its closest neighbor nodes. In this paper, Dynamic Routing Algorithm (DyRA) has been proposed to select next hop node towards the destination. The forwarding decision is based on a computed metric which is a combination of Packet Reception Rate (PRR), Link Expiration Time (LET) information and Number of Slots (NoS) available at the candidate MRS nodes. Also, the proposed Relay-based Vehicular Network (RVN) in WiMAX using cross layer design (CLD) is designed to select the optimal next hop node and set new route when current routing path is no longer available. The preliminary results for system throughput performance and average end-to-end delay are analyzed. The results show that by deploying relay-based in vehicular network can enhance system throughput in terms of packet loss ratio (PLR), packet delivery ratio (PDR), and average end-to-end (ETE) delay. NCTUns simulation environment has been used to study the mobile node performance.