On the Achievable Throughput of Energy-Harvesting Nanonetworks in the Terahertz Band

In this paper, the maximum achievable throughput of electromagnetic nanonetworks in the terahertz (THz) band (0.1–10 THz) is comprehensively investigated. On the one hand, the peculiarities of the THz-band channel are taken into account by capturing the impact of the molecular absorption loss on the signal propagation. On the other hand, a two-state medium access control protocol is utilized to reflect the behavior of energy-harvesting nano-devices with constrained harvesting rate and maximum transmission power <inline-formula> <tex-math notation="LaTeX">$P_{0}$ </tex-math></inline-formula>. An ad-hoc nanonetwork is considered with <inline-formula> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> identical randomly located nano-devices, and each is capable of utilizing <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> Hz of bandwidth. When the node density of nanonetworks is low, the achievable throughput is <inline-formula> <tex-math notation="LaTeX">$O (W P_{0} ( { (n\log n )^{({\alpha _{spr}-1}/{2})}}/{\exp (({ \alpha _{abs}}/{({n \log n})^{1/2}} ))}) )^{({1}/{2})}$ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$\alpha _{spr}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$\alpha _{abs}$ </tex-math></inline-formula> refer to the spreading loss coefficient and the molecular absorption loss coefficient. When the node density of nanonetworks is very high, the interference among nano-devices governs the network behavior and the achievable throughput becomes <inline-formula> <tex-math notation="LaTeX">$O (({W^{2} P_{0}/ {I(n)}}) ({ (n\log n )^{({\alpha _{spr}-1}/{2})}}/~{\exp (({ \alpha _{abs}}/{({n \log n})^{1/2}}) )} ))^{({1}/{2})}$ </tex-math></inline-formula>. For both the cases, the upper boundaries of the achievable throughput are analytically derived, and the numerical results are provided. Numerical results illustrate that the molecular absorption loss plays the main role when the nanonetwork is sparse, and the interference dominates when the nanonetwork node density is very high.