Optimization of Unicast Services Transmission for Broadcast Channels in Practical Situation

Mobile access networks (e.g. LTE/3G) have enabled the emergence of multiple video-oriented mobile services, such as non-linear services (VoD and catch-up TV) as well as linear or near live services (live or internet TV). Additionally, due to the proliferation of highly "smart" mobiles and portable devices, a huge increase in demand of data services is observable [1]. Consequently the users will have to stream or to download video-oriented services through shared networks which need to fully exploit their already restricted spectrum resource. Optimal radio resource sharing techniques are highly desirable for mobile operators in order to enable all these devices to be connected over wireless networks, with a pre-defined guaranteed Quality of Service. In 1970's Cover [2] demonstrated that in the case of AWGN broadcast channel the simultaneous transmission of superimposed information from one source to multiple users achieves better spectrum efficiency compared with time-sharing or other orthogonal division schemes of the channel resources among users. Bergmans and Cover demonstrate that superposition coding reaches the theoretical capacity limit for two-user additive white Gaussian noise (AWGN) channel using an infinite Gaussian input alphabet [3]. Motivated by these remarkable results, practical implementation of superposition coding known as Hierarchical Modulation (HM or layered modulation) has been included in various standards, such as DVB-T for digital terrestrial television [4], DVB-H/SH for mobile digital TV transmission [5] for the transmission of broadcast scalable digital media [6].