Cross-Layer Spectral Efficiency of Adaptive Communications Systems with QoS Constraints

In the literature, the spectral efficiency is considered a key performance indicator that is used to classify various communications systems, algorithms, and techniques. However, the classification is typically performed while assuming that all systems have a static structure, and without considering the quality of service (QoS) requirements or the constraints imposed by the system design. Therefore, this work presents a new reliable and accurate approach to evaluate the spectral efficiency of communications systems while considering the system dynamics, QoS requirements and design constraints. To demonstrate its effectiveness, the proposed approach is used to evaluate the spectral efficiency of various blind and pilot-aided channel estimation and synchronization algorithms. The obtained results reveal that the spectral efficiency depends on several system variables such the signal-to-noise ratio (SNR), QoS requirements, system constraints, and the channel characteristics. Contrary to what is usually believed, the obtained results show that pilot-aided systems can be more spectrally efficient than blind systems for several cases of interest.