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Capacity and Throughput Analysis of Nanoscale Machine Communication through Transparency Windows in the Terahertz Band
The expectedly very limited communication distance of nanoscale machines in the Terahertz Band (0.1–10 THz) is one of the main factors narrowing the scope of the nanonetworking applications. In this paper, the use of the transparency windows in the THz Band, which provide molecular-absorption-free transmission, is proposed as a way to extend the communication distance of nanomachines. The trade-offs between the signal-to-noise (SNR) ratio, channel capacity, transmission bandwidth and communication distance for these windows are identified. The results suggest that, by focusing on the first transparency window (0.1–0.54 THz), reliable communication up to 10 m is feasible when using just 0.1 aJ per symbol to achieve a capacity of up to 10 Mbps. For the same energy per symbol, when using the entire THz Band, the capacity is up to 2 Tbps, but only for distances below a few centimeters. Motivated by these results, the achievable link throughput of a simple binary digital modulation scheme based on the transmission of width-adaptive pulses is investigated. The results show that, due to the relaxation time of molecular absorption noise, additional pauses between pulse transmissions are required, but reliable communication is possible even for very small SNR values. These results extend the application scope of nanonetworks and illustrate that they are not limited to small coverage areas but can also be used to carry traffic generated by both low-rate transactional and bandwidth-greedy applications at small-to-medium distances.