You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Survey of QoS routing protocols in Wireless Multimedia Sensor Networks 
Chapter Title:  (viii) Packet Service Time (PST). 
1. Abstract of Cited Paper (BIB001):  Wireless Multimedia Sensor Networks (WMSN) are new and emerging networks of wirelessly connected devices, which consist of cameras, microphones, infra-red sensors, scalar sensors and others. These networks are fast gaining popularity due to their potential to be incorporated in various applications, such as, traffic monitoring, border surveillance, smart homes, environment and habitat monitoring, to retrieve heterogeneous data from the environment. However, these networks present many challenges as they are highly sensitive to delay and errors. The paper presents a Cross-layer QoS Routing protocol for WMSNs (CR-WMSN) that is aimed at providing soft end-to-end delay guarantees. Evaluation of this protocol shows that it provides better delay guarantees as compared to minimum hop routing protocol. 
2. Abstract of Cited Paper (BIB002):  Wireless Multimedia Sensor Networks (WMSNs) consist of networks of interconnected devices involved in retrieving multimedia content, such as, video, audio, acoustic, and scalar data, from the environment. The goal of these networks is optimized delivery of multimedia content based on quality of service (QoS) parameters, such as delay, jitter and distortion. In multimedia communications each packet has strict playout deadlines, thus late arriving packets and lost packets are treated equally. It is a challenging task to guarantee soft delay deadlines along with energy minimization, in resource constrained, high data rate WMSNs. Conventional layered approach does not provide optimal solution for guaranteeing soft delay deadlines due to the large amount of overhead involved at each layer. Cross layer approach is fast gaining popularity, due to its ability to exploit the interdependence between different layers, to guarantee QoS constraints like latency, distortion, reliability, throughput and error rate. The paper presents a channel utilization and delay aware routing (CUDAR) protocol for WMSNs. This protocol is based on a cross-layer approach, which provides soft end-to-end delay guarantees along with efficient utilization of resources. Extensive simulation analysis of CUDAR shows that it provides better delay guarantees than existing protocols and consequently reduces jitter and distortion in WMSN communication.

Literature Review:
It is a combination of queuing time, network layer processing time, MAC layer processing time, and the transmission time of a node at each sensor node BIB003 BIB002 . (ix) Sleeping Delay. In duty cycle based sensor network, a node can be in active or sleeping state. To forward the packet, current node must wait for the neighboring node to wake up. This delay is called sleeping delay BIB001 .