Quorum Sensing-enabled Amplification for Molecular Nanonetworks Sergi Abadal, Ignacio Llatser, Eduard Alarc´ on, Albert Cabellos-Aparicio NaNoNetworking Center in Catalonia (N3Cat) Universitat Polit` ecnica de Catalunya C/ Jordi Girona 1-3, 08034 Barcelona, Spain {abadal,llatser,acabello}@ac.upc.edu and eduard.alarcon@upc.edu Abstract—Nanotechnology is enabling the development of de- vices in a scale ranging from a few to hundreds of nanome- ters. The nanonetworks that result from interconnecting these devices greatly expand the possible applications, by increasing the complexity and range of operation of the system. Molecular communication is regarded as a promising way to realize this interconnection in a bio-compatible and energy efficient manner, enabling its use in biomedical applications. However, the trans- mission range of molecular signals is strongly limited due to the large and inherent losses of the diffusion process. In this paper, we propose the employment of Quorum Sensing so as to achieve cooperative amplification of a given signal. By means of Quorum Sensing, we aim to synchronize the course of action of a certain number of emitters, which will transmit the same signal. Under the assumption of a linear channel, such signal will be amplified and thus the transmission range will be consequently extended. Finally, we validate our proposal through simulation. Index Terms—Quorum Sensing; Synchronization; Molecu- lar Communication; Amplification; Nanonetworks; Wireless NanoSensor Networks; Bio-inspired I. I NTRODUCTION Nanotechnology enables the development of nanomachines, that is, devices in a scale ranging from one to a few hun- dreds of nanometers. These nanomachines are not just the downscaled version of classical devices, but the result of taking advantage of the unique properties of nanomaterials at this scale, possibly following a bottom-up approach [1]. For instance, novel nanosensors are able to detect the presence of virus and other harmful agents [2], or to sense chemical compounds in concentrations as low as one molecule [3]. Still, nanomachines are expected to be capable of perform- ing very simple tasks due to their reduced size and energy constraints. Communication between nanodevices greatly en- hances and expands the capabilities of single nanodevices. The operational range of nanodevices is extremely limited as it is their size, and that is why networks of nanomachines (also referred to as nanonetworks) allow the application in larger scenarios [1]. Furthermore, nanonetworks can be used to coordinate tasks and realize them in a distributed manner, achieving higher global complexity while maintaining the energy consumption of single entities low. One example of such nanonetworks are the Wireless NanoSensor Networks (WNSNs) [4], in which nanosensor motes communicate in order to measure phenomena in a precise, autonomous and non-invasive manner. Numerous ap- plications of WNSNs have been proposed in the biomedical, environmental, industrial and military fields [4], being the biomedical applications the ones that are expected to take the most of the unique features of WNSNs. For instance, intra- body networks are envisaged to provide ultra-accurate new health monitoring systems [5] by gathering data about the level of different substances or the presence of certain agents (e.g. cancer biomarkers) and transmitting it wirelessly to the macroscale. How nanomachines will communicate is still an impor- tant research challenge. Traditional wireless electromagnetic communication, by means of graphene-based nano-antennas, has been proposed to address this issue [5], [6], [7]. These techniques are expected to produce electromagnetic radiation in the THz range [8], offering low propagation delays and high bandwidth. However, the aforementioned biomedical applications generally demand the use of biostable and energy efficient solutions and it remains unclear whether EM-based techniques will meet these requirements. Either way, many research efforts are focused on systems that will enable the use of these techniques. In contrast, diffusion-based molecular communication has caught the attention of the scientific community as a novel and promising way to achieve short-range communication between devices in the nanoscale [9]. This new communication paradigm mimics the way cells communicate among them, encoding information into molecules that are released until they eventually reach the receiver, that is, the molecules are physically transported by means of diffusion to the receiver. In this diffusion process, molecules move following concen- tration gradients in a way that can be mathematically modeled by using the Fick’s laws of diffusion [10]. As we can see, molecular communication mechanisms are based on completely different principles when compared to EM-based communications and indeed offer a high degree of biocompatibility and energy efficiency [11]. However, molecu- lar communication also poses important challenges that require the development of radically new principles. One of such challenges is the severe attenuation that molecular signals suffer as they propagate through the medium [9]. In this paper, we address the need for novel amplification schemes