The proliferation of high-end mobile computing devices (e.g., smartphones, tablets, notebooks and more) equipped with high-speed network access, enables the mobile users to watch multimedia content from any source on any screen, at any time, while on the move or stationary. Moreover, nowadays people tend to spend much of their time consuming multimedia content from various devices with heterogeneous characteristics (e.g., TV screen, laptop, tablet, smartphone, etc.). In order to support uninterrupted, continuous, and smooth video streaming with reduced delay, jitter, and packet loss to their customers, network operators must be able to differentiate between their offerings according to device characteristics, including screen resolution. With the mobile networks migrating towards Long Term Evolution (LTE)-Advanced and all-IP networks, people expect to connect to the Internet anytime, anywhere and from any IP-connected device. Therefore, fast surfing speed on Internet, high resolution display screen, advanced multi-core processor and lasting battery support are becoming significant features in the current mobile devices. In this context, this thesis describes research solutions which help establish an Always Best Experienced heterogeneous environment. The proposed solutions include: (1) a novel Utility-based Priority Scheduling (UPS) algorithm for resource allocation over LTE that considers the mobile device differentiation when providing high quality delivery of multimedia services. The priority scheduling decision is based on the device classification, mobile device energy consumption and multimedia streaming tolerance to packet loss ratio; (2) a Device-Oriented Adaptive Multimedia Scheme (DOAS) for multimedia delivery over LTE networks. DOAS is a cross-layer solution built on top of the downlink scheduler in LTE/LTE-A systems. The adaptation decision in DOAS is based on the end-user device display resolution information and Quality of Service (QoS); (3) an enhanced energy-aware DOAS (eDOAS) to provide an energy efficient interworking solution for LTE -WLAN heterogeneous environments and to prolong the battery lifetime of the mobile devices; and (4) an Evolved Energy-saving QoEaware Device-Oriented Adaptive Scheme (e3DOAS) for balancing energy-consumption of mobile devices and perceptual quality of mobile users and fairly adapting trade-off quality level to users by using coalition game theory based mechanism. A real experimental test-bed for mobile device power measurement was setup to measure the energy consumption of different mobile devices classes while performing Video on Demand (VoD). The impact of the device performance, quality levels of the multimedia stream and the transport protocols on energy consumption is analysed. The performance of the proposed solutions is evaluated using network simulators NS-3, LTE-Sim and Matlab.