3D Visual Communications

8.6 Cross-Layer Design

As discussed in Chapter 6, network protocols are organized in what is a called a “layered architecture”. In this architecture, the different functions and services needed for end-to-end communication of information, 3D video in our case, are divided into stacked layers. At the transmitter side, upper layers of the stack pass on information to the layer immediately below and lower layers of the stack provide services to the layer immediately above. The key concept to note in the layered protocol stack architecture is that layers pass on information and provide services only to those contiguous layers immediately below and above a given layer. In a cross-layer approach, this concept is replaced by the idea that layers can exchange information and provide services between noncontiguous layers. This idea of cross-layering still maintains the modularity of layers seen in a layered architecture. Another interpretation for a cross-layer approach where modularity is lost, consists in merging multiple layers into a single one.

One application of cross-layer design for the wireless communication of 3D video is studied in [20]. In this case, cross-layering is proposed for the very interesting application, very much relevant to 3D video, where for the foreseeable future 3D video services will have to maintain backwards compatibility with 2D services. This is because during the period of mass-market deployment of 3D services and viewing devices, a good proportion of users ...