Video streaming is expected to acquire a massive share of the global internet traffic in the near future. Meanwhile, it is expected that most of the global traffic will be carried over wireless networks. This trend translates into considerable challenges for Service Providers (SP) in terms of maintaining consumers' Quality of Experience (QoE), energy consumption, utilisation of wireless resources, and profitability. However, the majority of Radio Resource Allocation (RRA) algorithms only consider enhancing Quality of Service (QoS) and network parameters. Since this approach may end up with unsatisfied customers in the future, it is essential to develop innovative RRA algorithms that adopt a user-centric approach based on users' QoE. This chapter focus on wireless video over Critical communication systems that are inspired by QoE perceived by end users. This chapter presents a background to introduce the reader to this area, followed by a review of the related up-to-date literature.
TopThe Triple-Q Model
The roots of “quality” have been discussed in (Reeves, and Bednar, 1994) where different but mutually related definitions have been suggested. Quality has been defined as “excellence”, “value”, “conformance to specifications”, and “meeting and/or exceeding customers' expectations”. In the context of multimedia communications, quality is attached to the three main elements shown in Figure 1: the network, the end-user, and the Service Provider (SP). Accordingly, a triple-Q model (Moorsel, 2001) has been proposed to combine network’s Quality of Service (QoS), customer’s Quality of Experience (QoE) and service provider’s Quality of Business (QoB). The objective is to increase each quality until an overall optimality is achieved. Recently, the triple-Q model has grabbed even more attention by researchers. For instance, an extended multidimensional approach for this model has been proposed in (Ibarrola et al., 2014).
Figure 1. The main three players in the multimedia delivery chain
Vast majority of research efforts have focused on exploring the interaction between QoS and QoE and have overlooked the service provider’s interest, until QoB was put into context in the triple-Q model. In a typical multimedia communications scenario (Tektronix, 2008), as illustrated in Figure 2, emphasis is put on the stages where QoS and QoE are considered. In this model, the content passes through several stages over the “data plane” before it is delivered to and consumed by the end-user. Firstly, the audio-visual content is created by the content provider and subsequently passed to the application provider where it is encoded and may be stored. In the third stage, the encoded stream is transported over the network provider’s core IP network. This is a controlled network such that QoS parameters can be controlled and guaranteed. Fourthly, the content is transported to the access network, which is another QoS control facility, after which the content is delivered to the Consumer Premise Equipment (CPE) for end-user consumption. This final stage is where user’s QoE can be measured. On a reverse path, measured QoE parameters are conveyed back to the application provider over the “control plane”. Accordingly, the application provider advises the network provider to set appropriate QoS conditions. This model is said to be an adequate model to help SPs accommodate multimedia services at controllable levels of QoE (Tektronix, 2008). However, the model focuses on the importance of user satisfaction trusting it will result in better customer loyalty, which is believed to generate more profit for SPs, but there is no direct link between profit and customer satisfaction. Instead, it is an indirect link emerged as a result of customer loyalty. Consequently, there is a gap between customer satisfaction (QoE) and business revenue (QoB). Therefore, QoB was introduced as a significant element in formulating the triple-Q model.
Figure 2. Typical multimedia communications scenario