# Ambient Environmental Parameter Estimation for Reliable Diffusive Molecular Communications
## 1 Introduction  
In recent years, research on molecular communication has been more active with the expectation of realizing nano-networks [1, 2, 3]. Molecular communication (MC) is a communication technology that uses molecules such as proteins and ions to transmit information. MC differs from existing communication technologies, which use electromagnetic waves, because it uses biomolecules for information transmission [4, 5]. Most molecular communications are a few nanometers to a few micrometers in size and exhibit biocompatibility. These characteristics of MC are expected to lead to applications in environments, including medical and healthcare fields, where existing communication technologies are not applicable [6, 7]. An example of the application of MC is the communication between bio-nanomachines [8]. Given that it is difficult to miniaturize existing wireless communication technologies because the length of the antenna is dependent on wavelength, MC can potentially be applied for biomonamachines. Furthermore, the application of biomonamachines in drug delivery systems (DDS) is under consideration. Molecular communication is expected to be applied not only to the body, but also to the out-of-body environment. An example involves the use of MC to transport materials and reagents between components, such as sensors and reactors in lab-on-chip [7]. In recent years, not only short-range (a few nanometers to a few micrometers) communication, but also long-range (centimeter-order) MC methods have been proposed wherein blood is used as a medium to carry information molecules and transmit information [9]. Furthermore, the characteristics of a micro-fluidic network have been characterized, and adielectrophoretic relay-assisted MC system has been modeled using transmission line technology, as an example, for establishing communication between various entities in lab-on-chip [10]. Moreover, other methods, such as the Monte Carlo method, simplified Poisson method, simplified Gaussian method, and simplified gamma method, have been proposed to study the inter-sign interference problem [11]. Additionally, recent studies have experimentally evaluated pH-based coding systems [12; 13] and the use of superparamagnetic iron oxide nanoparticles (SPIONs) as transmission particles [14; 15]. One form of molecular communication is diffusive molecular communication, which is a type of communication based on the diffusion of released information transfer molecules [16]. In recent years, research on diffusive molecular communication has led to the development of a system with multiple-input multiple-output (MIMO) [17; 18] channels, and a neural network detection method based on sequential learning [19]. Additionally, a mathematical model was proposed to investigate the effect of multiple measurements of molecular concentration on the performance of mobile molecular communication [20]. In diffusive molecular communication, the diffusion model of a molecule is mathematically modeled as channel impulse response (CIR). This enables the design of optimal detectors and other devices based on CIR. In previous studies, CIR has been derived for diffusive molecular communication, and communication methods wherein thresholds based on the CIR have been examined [16; 21]. However, a derived CIR assumes an idealized environment, where the temperature is constant during diffusion and the transmitting molecule is a point-wave source to simplify the boundary conditions. This assumption does not reflect the characteristics of real-world molecular communication. In this study, we assumed the application of molecular communication in a lab-on-chip as a change in temperature. We analyzed over time in the number of received molecules when environmental temperature was varied from 10 to 40 \({}^{\circ}\)C, and we focused on 25 and 35 \({}^{\circ}\)C to evaluate bit error rate (BER) characteristics because the temperature on the lab-on-chip increases from room temperature by 11 \({}^{\circ}\)C on the chip [22].