Optimizing practical adaptive frequency hopping and medium access control in ad hoc networks. Invited Paper

Adaptive frequency hopping (AFH) as proposed, e.g., in IEEE 802.15.2 aims at increasing system reliability in the presence of quasi-static external interference. Practical approaches require autonomous sensing of the interference environment, with the measurements containing both external interference and network self-interference. In prior work, a simplistic model for AFH-based ad hoc networks was developed to analyze how this issue affects the area spectral efficiency (ASE). It was found that the AFH mechanism severely degrades ASE when self-interference is increased. In this paper, we modify the model to account for the correlation between the nodes’ adapted hop sets. We then address the question of how to design the system parameters to achieve optimal performance and avoid the degradation. We discuss different optimization problems and identify sensing techniques that can cope with increased self-interference. Among these techniques, carrier detection sensing was found to be robust against self-interference while showing good performance. We further discuss cases where joint optimization of the AFH and CSMA mechanisms is beneficial and cases where there is little to be gained.