In this work, a novel over-the-air (OTA) radio frequency (RF) energy harvester (EH) architecture implementing a microelectromechanical system (MEMS) as matching network is presented. The system operates at a frequency of 820 MHz and is composed of a sub-50 Ω single-meandered antenna on printed circuit board, a MEMS film bulk acoustic resonator (FBAR), and a Schkotty diode half-bridge full wave rectifier followed by a sample-and-hold circuit.Experimental results demonstrate that the inclusion of the FBAR leads to an improvement of the energy harvester’s efficiency, resulting in a 8-fold increase of the harvested power compared to a system without the MEMS resonator. This first demonstration of an increased efficiency over-the-air energy harvester implementing MEMS resonator representS an encouraging and viable solution for ultra-low or zero-power electronic devices for Internet of Things applications, including distributed and remote sensor networks.

An energy-efficient and scalable vector backscatter transponder architecture utilizing delta-sigma digital-to-digital converter (DDC) based antenna load modulation is proposed. In contrast with the current state of the art (SoA) M-QAM backscatter transponder that uses multiplexer (MUX)-based antenna load modulation and requires M antenna loads, the proposed architecture can be scaled to e.g. 256-QAM using only 4 antenna loads. A 256-QAM, 86.7Mbps backscatter transponder design capable of forming RF channels is developed utilizing 1-bit delta-sigma DDCs. The proposed design achieves an estimated 30pJ/bit figure of merit which constitutes a 4.4x improvement over the SoA MUX-based architecture. An energy model of an IEEE 802.11 compatible IoT device is developed. A battery life of 40 years corresponding to an uplink (UL) transaction cycle of 1 hour is estimated for an IEEE 802.11 compatible IoT device employing the proposed backscatter transponder based UL. This constitutes an 8x improvement in battery life compared to an IoT device that uses a conventional direct-conversion transmitter based UL.

Enabling Internet of Things (IoT) in harsh environments relies on improving battery life, which can be achieved using Wake-Up Receivers (WuRX) with high quality factor (Q) RF components. MEMS micro-acoustic RF resonators have been proposed as strategic components to provide large passive voltage amplification as well as noise and interference rejection, ultimately providing means to reduce system-level link budget and power-hungry cells count in the back-end circuitry. In this work, we present an integration effort of a high-Q MEMS with an IoT RF front-end. Integration issues are discussed first at simulation level, and then verified on an WuRX designed thanks to the integration of in-house fabricated FBAR resonator and commercial integrated circuits. The result is a compact IoT RF sensor operating at 820 MHz with an outstanding measured RF gain of 12 dB, a 3 dB bandwidth of 7 MHz and an out-of-band rejection of 23 dB. Communication test shows that digital bit streams are fully recoverable at –46 dBm RF power with zero error rate above that threshold.

A zero-energy downlink air-interface (ZE-DL) that does not draw power from the device's battery is introduced. Information packets sent on the ZE-DL are preceded by a power-optimized preamble (POP) where the energy harvested from the POP is used by an ultra-low power receiver (ULP-RX) to decode the information packets. An approach for estimating the POP duration as a function of free-space path loss, the energy harvester efficiency and the ULP-RX power consumption is outlined. An IoT device architecture is proposed where the ZE-DL functions as a supplement to the 3GPP Uu air-interface. On-demand features are introduced into the 3GPP system using a broad class of wake-up signal (WUS) transmissions on the ZE-DL. An analytical framework for estimating the network resource overhead associated with POP transmissions is developed. An energy model for the IoT device is developed and a pathway to 20, 40-year battery life for Uu uplink (UL) transaction cycles of 1, 5 days is demonstrated where the POP transmission related network overhead is limited to less than 6%.

This paper presents the performance results for a series of outdoor experiments conducted on a fifth generation (5G) mmW Mesh Transport system to show multiplexing of high throughput fronthaul (FH) and backhaul (BH) traffic over a long-range mmW link with exceedingly low latency. The EdgeLinkTM millimeter wave (mmW) system was deployed as part of the European 5G-Crosshaul H2020 5G-PPP project where an outdoor mesh network was setup in Berlin with link distances up to 185 meters. The inclusion of a self-organizing Mesh topology guarantees failure recovery within the system through redundant paths which are managed by a cloud based software defined network (SDN) controller. Key performance metrics (KPIs) such as throughput, jitter and latency results were collected for analysis and will be discussed in this paper. In addition to performance characterization, one of the main goals of the 5G-Crosshaul project was as a proof-of-concept exercise for using a mmW wireless Mesh network as a cost efficient fifth generation (5G) transport solution that can seamlessly support both packet based fronthaul and backhaul traffic on one unified network in place of the 2 separate networks that is commonly used in today's infrastructure. The proposed solution involved moving away from the legacy Common Public Radio Interface (CPRI) communication between the baseband unit (BBU) and remote radio head (RRH) to a less demanding in terms of capacity and latency, packet data convergence protocol-radio resource controller (RLC-PDCP) functional split that is further enhanced with the deployment of a SDN based mmW transport as a Next Generation fronthaul interface and CloudRAN architecture. Based on our experiments we were able to conclude that a longrange wireless mmW Mesh transport network can effectively be used to support future 5G Cloud Ran (C-RAN) upper layer stack splits requirements.

Recent developments in the communications industry to accommodate user demand for ubiquitous, instantaneous over the air access to multimedia rich content has made spectrum utilization efficiency one of the key research topics. Full-Duplex radios have great potential to improve spectrum utilization efficiency and are well-studied for below 6 GHz applications. In this paper, we explore the possibility of mmWave Full-Duplex operation in 5G. We group the Full-Duplex radio system components into four modules: antenna systems, analog frontend and digital baseband self-interference cancellers, and protocol stack enhancements. We create a system model to analyze link-budget and determine the usable range for Full-Duplex operation by focusing on antenna systems, analog RF frontend design assumptions, and the channel models. We also highlight tradeoffs for employing cancellation techniques and criteria for protocol stack enhancements.

Millimeter wave communications promises to enable the very high data rates demanded of 5G networks, but there are several hurdles that must be negotiated first. One of these hurdles is the small energy collecting capability of the small aperture antennas at these wavelengths. High gain antennas are required to overcome this limitation. The 60 GHz band is of particular interest due to the large 7-9 GHz of unlicensed spectrum available. The often cited atmospheric absorption in the band (~13dB/km) is easily tolerated in the 100-200m links envisioned for 5G networks. In order to test the feasibility of a 60GHz network, a platform is being constructed and a low cost, high gain antenna is required. For a low cost and small size solution, a low profile microstrip phased array antenna has been designed and fabricated on low-loss, two-layer Liquid Crystal Polymer (LCP) substrate. 4×4, 8×8 antenna array prototypes have been characterized and the results are described.

This work investigates the propagation characteristics of an office building in the 60 GHz band. From reflection and scattering measurements of several painted and un-painted common building materials recorded at 60 GHz, the complex permittivity and Lambert's Law scattering coefficient of each material are extracted. Diffraction measurements from two building corners at 60 GHz are also presented and analyzed. Lastly, power angular profiles of building penetration and scattering at 60 GHz are presented and used to characterize the outdoor to indoor propagation, and the significant scatterers on a building surface, respectively.

This paper investigates diffracted and scattered waves in unlicensed millimeter wave mobile-to-mobile, access and backhaul radio links. Narrowband 60 GHz measurements of diffraction at building corners, and scattering by a car, lamppost and building, as well as blocking by humans are presented. Semi-analytical corner diffraction and human blocking models are proposed and verified based on the measurements. Analysis of the diffraction and scattering shows that the contributions from vehicular and lamppost scattered paths can be dominant compared to corner diffracted paths. Measurements also show that the majority of power from building scattering arrives in and near the horizontal plane containing the transmit and receive antennas.

In this work, we investigate building scattering at 2 GHz by performing 60 GHz scattering measurements on a 1/30 scale building model. The materials used to build this model were chosen to have similar reflected and transmitted power characteristics at 60 GHz to common building materials at 2 GHz. Co-polarized and cross-polarized scattering measurements of the model were performed with and without furniture and the front building surface. Near the specular direction, results show that the contribution from waves that enter a building, internally scatter and/or reflect, and then exit the building are not significant compared to those that only interact with the features on the front building surface. However, away from the specular direction, this contribution can be observed.

In this paper, we investigate the loss caused by multiple humans blocking millimeter wave frequencies. We model human blockers as absorbing screens of infinite height with two knife-edges, We take a physical optics approach to computing the diffraction around the absorbing screens, This approach differs to the geometric optics approach described in much of the literature. The blocking model is validated by measuring the gain from multiple-human blocking configurations on an indoor link. The blocking gains predicted using Piazzi ' s numerical integration method (a physical optics method) agree well with measurements taken from approximately 2.7 dB to -50 dB. Thereofre, this model is suitable for real human blockers, The mean prediction error for the method is approximately -1.2 dB, and the standard deviation is approximately 5 dB.

The loss from multiple human blockers is investigated at millimeter wave frequencies. We model the blocking as absorbing screens of infinite height with two knife-edges, and use a physical optics approach, as opposed to a geometric optics approach used in literature, to compute the diffraction around the absorbing screens. The blocking model is validated with blocking gain measurements of multiple human blocking configurations on an indoor link. The blocking gains predicted using Piazzi’s physical optics numerical integration method have good agreement with the measurements in the range of approximately 2.7 dB to -50 dB, making this model suitable for real human blockers. The mean prediction error for the method is approximately -1.2 dB and standard deviation is approximately 5 dB.