Near-field Communication Link Research Articles

In Situ Near-Field Path Loss and Data Communication Link for Brain Implantable Medical Devices Using Software-Defined Radio

The rapid evolution in brain implantable medical devices (BIMDs) promises a new paradigm of medical diagnosis, monitoring, and therapeutics. The MedRadio frequency band (401–406 MHz) offers an acceptable penetration of electromagnetic (EM) fields in biological tissues and thus is well suited for wireless medical telemetry (WMT). Unlike other parts of the body, head tissues exhibit a high level of EM fields absorption, which provides a significant challenge for devices implanted in this part of the body. Therefore, it is important to appraise data communication and path loss over this difficult channel. In this article, a brain implantable antenna and an exterior antenna are developed to operate at 406 MHz MedRadio band. The exterior antenna is a miniaturized composite loop-patch antenna with tuning slots, whilst the implantable antenna is a capacitively loaded loop with parasitic patches. A near-field communication link is tested via a software-defined radio (SDR) module in a cerebrospinal fluid (CSF) phantom and pig primate. The link budget of the in situ communication link demonstrates a reliable data transfer of 200 kb/s with a low level of input power (−17.55 dBm) and high signal-to-noise ratio (SNR) for near-field transmission. Since, the EM fields decay rapidly in head tissues, a path loss model is thus essential for BIMDs. The developed path loss model in CSF phantom and pig primate yield an attenuation between 43 and 56 dB for a distance ranging from 20 to 60 mm at 406 MHz. Overall, the results show that near-field data communication link for BIMDs can be utilized over the conventional far-field link for a better signal-to-noise ratio (SNR) with a low power requirement.

Wireless powering and communication for implants, based on a Royer oscillator with radio and near-field links

A compact wireless power and communication development system for implantable devices was designed and tested with two receiver circuits based on a 433MHz separate RF link and a uni-directional near-field communication link that uses the powering field. The power transmitter was designed around a Royer oscillator with additional hardware for power and frequency control using a novel Schottky varactor method allowing 560kHz frequency shift. The near-field link was found to be at least 10 times more efficient than the separate radio in terms of data rate vs. power consumption when used in similar circumstances with the same receiving coil, as well as requiring much less board space. Furthermore, a second system was designed to extend the study of near-field communication to include a bidirectional link as well as to correct the deficiencies of the first system that included problems with noise and parasitic oscillations. The main goal of this system was to assess the efficiency of power transfer for short range (subcutaneous) mm-size implants with flexible cuff-like transmitting coils. A 1.5W power transfer was achieved with up to 32% efficiency, yielding downlink and uplink data rates of 20kbps and 400bps respectively. Finally, effects of load impedance and tissue losses on efficiency were measured and discussed.

Numerical simulation of broadband vortex terahertz beams propagation

Orbital angular momentum (OAM) represents new informational degree of freedom for data encoding and multiplexing in fiber and free-space communications. OAM-carrying beams (also called vortex beams) were successfully used to increase the capacity of optical, millimetre-wave and radio frequency communication systems. However, the investigation of the OAM potential for the new generation high-speed terahertz communications is also of interest due to the unlimited demand of higher capacity in telecommunications. Here we present a simulation-based study of the propagating in non-dispersive medium broadband terahertz vortex beams generated by a spiral phase plate (SPP). The algorithm based on scalar diffraction theory was used to obtain the spatial amplitude and phase distributions of the vortex beam in the frequency range from 0.1 to 3 THz at the distances 20-80 mm from the SPP. The simulation results show that the amplitude and phase distributions without unwanted modulation are presented in the wavelengths ranges with centres on the wavelengths which are multiple to the SPP optical thickness. This fact may allow to create the high-capacity near-field communication link which combines OAM and wavelength-division multiplexing.

Formal security analysis of near field communication using model checking

Near field communication (NFC) is a short-range wireless communication technology envisioned to support a large gamut of smart-device applications, such as payment and ticketing. Although two NFC devices need to be in close proximity to communicate (up to 10 cm), adversaries can use a fast and transparent communication channel to relay data and, thus, force an NFC link between two distant victims. Since relay attacks can bypass the NFC requirement for short-range communication cheaply and easily, it is important to evaluate the security of NFC applications. In this work, we present a general framework that exploits formal analysis and especially model checking as a means of verifying the resiliency of NFC protocol against relay attacks. Toward this goal, we built a continuous-time Markov chain (CTMC) model using the PRISM model checker. Firstly, we took into account NFC protocol parameters and, then, we enhanced our model with networking parameters, which include both mobile environment and security-aware characteristics. Combining NFC specifications with an adversary's characteristics, we produced the relay attack model, which is used for extracting our security analysis results. Through these results, we can explain how a relay attack could be prevented and discuss potential countermeasures.

A Wireless Powering and Communication System for Implantable Devices Based on a Royer Oscillator with Radio and Near-field Communication Links

A compact wireless power and communication development system for implantable devices was designed and tested with two receiver circuits based on a 433MHz separate RF link and near-field communication link using the power transfer field. Operating ranges were 9 and 6cm respectively. The power transmitter was designed around a Royer oscillator with the possibility of power control and frequency control using a unique Schottky varactor method allowing 560kHz frequency shift.

Direct Antenna Modulation (DAM) for Enhanced Capacity Performance of Near-Field Communication (NFC) Link

Shannon's theorem suggests that the capacity of a wireless link is determined by both the power received and the bandwidth of the system. However, in a conventional setup of an inductively coupled near-field communication (NFC) link, there is a trade-off between the power coupled through and the bandwidth. Direct antenna modulation (DAM) is a feasible scheme to mitigate this dilemma. With DAM utilized in a NFC link, the power and bandwidth product limit in a high Q system can be circumvented because the non-linear/time-varying nature of the operation allows high speed modulations decoupled from the charging and discharging process of the high-Q resonator. In this paper, the theory of NFC link with DAM on the transmitter is presented and validated with an experimental setup. Improvement in reception of the high-speed modulation information is observed in the experiment, implying that a superior capacity performance of a NFC link is achieved through DAM versus the traditional scheme.

Authentication Systems Using ID Cards over NFC Links: The Spanish Experience Using DNIe

The personal identification in mobile scenarios has attracted a lot of attention in the last few years due to the emergence of new communications paradigms that enable the establishment of ad hoc communications. These communications must be carried out in a secure way since they can be involved in applications such as payments and access systems. Consequently, new secure systems should be proposed for managing security in such complex, mobile and variable conditions. This paper proposes a new authentication system based on the Spanish ID card and the wireless NFC (Near Field Communication) technology. It uses cryptography techniques and authentication certificates to establish secure communications between two interlocutors. The proposed network oriented architecture enables the proposed authentication system to operate in both local and remote modes.

Link Budget and Capacity Performance of Inductively Coupled Resonant Loops

A near field power transfer equation for an inductively coupled near field system, analogous to Friis transmission equation for far field communications, is derived based on the equivalent circuit model of the coupled resonant loops. Experimental results show the proposed near field coupling equation is trustworthy as it correctly predicts the transferred power versus distance relationship for different values of loaded quality factors at the transmitter and the receiver. Capacity performance of near field communication (NFC) links are analyzed based on information theory, respectively for noise limited and interference limited scenarios. The analytical results provide guidelines for power and capacity budget in inductively coupled antenna systems. Examples of inductively coupled VLF NFC links are evaluated for different operating scenarios, demonstrating the efficacy and importance of the proposed method for near field link budget.