Toward Modeling and Assessing the Disorientation and Misalignment Effect in Optical Wireless Nano-Networks

It is true that medical diagnosis and treatment have always been at the top of research activities. Recently, a very promising area that combines the operation of human body with the principles of wireless communications has arisen and given birth to the field of bio-photonics. Although the deployment of nano-networks inside the human body seems to be an achievable goal, the implementation of optical wireless nano-networks remains a very challenging field due to the lack of accurate channel modeling. Therefore, in this paper, we comprehensively investigate the optical wireless nano-communication channels by considering the deterministic geometric losses (e.g., optical absorption and scattering in human tissues), and modeling the impact of nano-node disorientation and misalignment in in-body nano-networks. To this end, we analytically study the stochastic nature of disorientation and misalignment coefficient in terms of the position and orientation of the nano-node with reference to the out-of-body optical receiver. In particular, we study the statistics of the joint disorientation and misalignment coefficient in terms of the probability density function, which is given in closed-form expression, whereas its cumulative distribution function is introduced as a semi-infinite series expression. Building upon them, we extract novel analytical expressions for the average signal-to-noise-ratio and the outage probability, and a thorough study on the impact of the human tissues on the above performance metrics is conducted. The analytical results are corroborated and cross-compared by means of Monte Carlo simulations, which reveal the importance of accounting for the joint impact of disorientation and misalignment of nano-node when designing optical wireless nano-networks.