A survey of routing protocols for THz-based mobile wireless nanonetworks

Mobile wireless nanonetworks are emerging communication systems composed of nanoscale devices capable of sensing, processing, and exchanging information in highly constrained environments. Electromagnetic communication in the terahertz (THz) band is considered a promising solution for such networks because it enables very high data rates and fast signal propagation. However, routing in THz-based mobile wireless nanonetworks remains a major challenge due to the limited energy, memory, and processing capabilities of nanonodes, the very short communication range, and the dynamic topology caused by node mobility. This paper presents a systematic survey of routing protocols for THz-based mobile wireless nanonetworks. The selected protocols are organized into several categories, namely thermal-aware, flow-guided, mobile nanorouter-based, energy-aware, learning-based, adaptive, and heuristic-based routing approaches. The analysis shows that only few studies explicitly address mobile THz-based routing, and this limited corpus highlights the emerging nature of the field. The survey also identifies key open challenges, including reliable relay selection under dynamic topology, energy-efficient forwarding, realistic mobility modeling, scalability, and the need for stronger validation frameworks. Finally, the paper outlines future research directions for designing lightweight, robust, and mobility-aware routing protocols for THz-based mobile wireless nanonetworks.