## 2 Related Works
### Multi-Metric Oriented Video Streaming  
The multi-metric based video streaming is discussed based on different metrics considered in vehicular network, which are related to road-based metrics. In [PERSON] et al. [9], a multipath video streaming solution based on node disjoint and link disjoint algorithm that employs Ad-hoc On-Demand Vector (AODV) routing concept has been suggested. However, the node-disjoint and link disjoint concepts are not sufficient to minimize the route coupling effect and wireless contention, because the signal coverage of the nodes in the multiple paths is not put into consideration during path selection. ETX and node disjoint concepts are considered as selection criteria for forwarding vehicle in video streaming. However, other connectivity metrics such as vehicle trajectory and vehicle density have not been considered for ascertaining vehicle connectivity during video transmission. A novel Multichannel Error Recovery Video Streaming (MERVS) protocol is proposed to address the issue of high packet loss in VANETs [19]. MERVS uses an error recovery process for high quality and real-time video streaming. It sends video through two channels: Reliable and unreliable channel. It transmits I-frames through the reliable channel, while inter-frames are transmitted through the unreliable channel. In order to reduce delay, scalable reliable channel, quick start and priority queue were incorporated. However, MERVS lacks routing and a relay selection algorithm; hence, further study is required. QoS-aware Hierarchical Web Caching (QHWC) scheme for online video streaming applications in Internet-based VANETs is presented to address bandwidth and delay challenges. The scheme considers mobile video streaming in order to attain qualitative video delivery at the receiver node [20]. In this proposal, new metrics including Query to Connectivity Ratio (QCR) and Load Utilization Ratio (LUR) are employed to maintain QoS for different video streaming applications. However, in a hierarchical web caching approach, a link breakage or dead node in one level of the hierarchy may cause failure of video message delivery. Further, a Mobility-aware and Quality-driven Retransmission limit Adaptation Scheme for Video streaming over VANETs (MQRASV) is presented [21]. The adaptation scheme employs multi-objective optimization structure that concurrently reduces the likelihood of start-up delay and playback freeze of a streaming video at the destination vehicle. They are reduced by tweaking the MAC retransmission limit in relation to channel delay result and packet communication rate. In addition, the intervallic channel state approximation is carried-out at the RSU considering the information obtained from the Doppler shift effect and Received Signal Strength (RSS). Furthermore, two-hop transmission approach has been employed in the zone where the destination vehicle is found within transmission range of any of the RSU. However, despite its strength in terms of playback freeze and contention window, link breakage has not been considered in the scheme. In addition, in [PERSON] et al. [10], a multi-metric based on map-aware routing protocol for vehicular network has been suggested. Metrics considered include vehicle density, distance, vehicle trajectory and available bandwidth for making forwarding decision. This aims to reduce packet delay and losses. However, since the urban scenario is considered, there is need to check the interference or noise in the signal based on Signal to Interference plus Noise Ratio (SINR). In addition, multimedia data is not employed in implementation and evaluation of the proposed protocol. Further, a similar multi-metric map-aware routing protocol, which is based on multi-multimedia data for vehicular communication has been proposed. The multi-metric considered include distance, vehicle trajectory, vehicle density, MAC losses and available bandwidth for evaluating forwarding vehicle selection [11]. They are important for the achieving quality video delivery.