Directional Modulation from a Wrist-Wearable Compact Antenna

Abstract

This work proposes compact multiport antennas for directional modulation (DM) on wrist-wearable devices to improve the secrecy and privacy of the transmitted data. The DM performance is investigated using the antenna in free-space and with a human forearm-phantom. The system achieves a low Bit Error Rate (BER) < 10 −1 with 44 • beamwidth, in a unique steerable secure direction over the entire azimuth plane. Full-wave simulations including the phantom at 5 GHz show realized gains of up to 4.26 dBi. The specific absorption rate is below the standard limits, with maximum values of 0.487 W/kg and 1.42 W/kg for the wrist-worn and next-to-mouth conditions, respectively.

Energy-Efficient Physical Layer Security for Wearable IoT Devices

“…To analyze the performance of the energy-efficient directional modulation scheme, a simulation setup comprising a multimodal beamsteering stacked-patch antenna proposed in [12] and a forearm phantom are used. For completeness, the design is shown in Fig.…”

“…It then uses phase compensations dependent on the desired secure direction of the legitimate user, and a random number n corresponding to the antenna port used for signal transmission (see [15] for a detailed discussion of the scheme). The method then offers several advantages compared to [11], [12], e.g. : no excessive artificial noise is generated in the directions where the illegitimate users are, which reduces interference with legitimate users present in other systems.…”

“…In state-of-the-art it is executed using antenna arrays [7]- [9], which due to the inter-element spacing, are too large for wearable IoT devices at sub-6 GHz bands. DM implementations using small antennas are discussed in [10]- [12]. However, those implementations require simultaneous port activation to realize DM, which is still challenging for wearable IoT systems, as the necessary number of active RF transceivers increases the cost and exacerbates the tight energy constraint of wearable technologies.…”

“…In this work, we propose a single-port DM scheme for on-body IoT devices. The system is tested using a fourlayer human forearm phantom and a 5-port stacked patch antenna capable of unidirectional beamsteering around the entire horizontal plane [12]. It is demonstrated that a low Bit Error Rate (BER) of 1.5 × 10 −5 is experienced by the desired receiver, while a high error rate of up to 0.498 is observed outside the desired regions.…”

Spherical Modes Driven Directional Modulation With a Compact MIMO Antenna

“…To address the size-constraints in IoT scenarios, few works have investigated DM using compact multimodal antennas, e.g. : in [13], a dual-mode antenna of λ/2 diameter is proposed for DM; in [14], a four-mode antenna of 0.7λ diameter is presented for dynamic DM; in [15], a five-mode antenna of 0.65λ is proposed for DM in onbody IoT devices. However, in those works either a relatively large size/profile is still used (limiting their implementation for small IoT scenarios), high side-lobes are present (which can be exploited by eavesdroppers to retrieve the transmitted information), experimental verifications are not discussed, or a model highlighting the complete theoretical framework for synthesizing different beam patterns around the azimuth plane, for a given antenna space, is not presented.…”