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Wireless charging of devices has significant outcomes for mobile devices, IoT devices and wearables. Existing technologies consider using Point to Point type wireless transfer from a transmitter Tx (node that is sending Power) to a receiver Rx (node that receives power), which limits the area of coverage for devices. As a result, existing systems are forced to use near field coupling to charge such devices. Fundamental limitation is also that such methods limit charging to a small hotspot. In partnership with Wireless Electrical Grid LANs (WiGL pronounced “wiggle”), we demonstrate patented Ad-hoc mesh networking method(s) to provide wireless recharging at over 5 feet from the source, while allowing significant lateral movement of the receiver on the WiGL (Wireless Grid LAN or local area network). The transmitter network method leverages a series of panels, operating as a mesh of transmitters that can be miniaturized or hidden in walls or furniture for an ergonomic use. This disruptive technology holds the unique advantage of being able to provide recharging of moving targets similar to the cellular concept used in WiLAN, as opposed to prior wireless charging attempts, which only allow a hotspot-based charging. Specifically, we demonstrate the charging of a popular smartphone using the proposed system in the radiating near field zone of the transmitter antennas, while the user is free to move in the space on the meshed network. The averaged received power of 10 dBm is demonstrated using 1W RF-transmitter(s), operating in the 2.4 GHz ISM band. The proposed hardware consists of antennas arrays, rectennas, power management and USB 2.0 interfaces for maintaining a voltage between 4.2 and 5.3 V and smooth charging. We also show extending the wireless grid coverage with the use of multiple transmitting antennas, and mechanical beam-steering even further an increased coverage using the proposed system.

We study the energy-efficient power allocation techniques for OFDM-based cognitive radio (CR) networks, where a CR transmitter is communicating with CR receivers on a channel borrowed from licensed primary users (PUs). Due to non-orthogonality of the transmitted signals in the adjacent bands, both the PU and the cognitive secondary user (SU) cause mutual-interference. We assume that the statistical channel state information between the cognitive transmitter and the primary receiver is known. The secondary transmitter maintains a specified statistical mutual-interference limits for all the PUs communicating in the adjacent channels. Our goal is to allocate subcarrier power for the SU so that the energy efficiency metric is optimized as well as the mutual-interference on all the active PU bands are below specified bounds. We show that the green power loading problem is a fractional programming problem. We use Charnes-Cooper transformation technique to obtain an equivalent concave optimization problem for what the solution can be readily obtained. We also propose iterative Dinkelbach method using parametric objective function for the fractional program. Numerical results are given to show the effect of different interference parameters, rate and power thresholds, and number of PUs.

Surface Electromyography (sEMG) is a non-invasive measurement process that does not involve tools and instruments to break the skin or physically enter the body to investigate and evaluate the muscular activities produced by skeletal muscles. The main drawbacks of existing sEMG systems are: (1) they are not able to provide real-time monitoring, (2) they suffer from long processing time and low speed, (3) they are not effective for wireless healthcare systems because they consume huge power. In this work, we present an analog-based Compressed Sensing (CS) architecture, which consists of three novel algorithms for design and implementation of wearable wireless sEMG bio-sensor. At the transmitter side, two new algorithms are presented in order to apply the analog-CS theory before Analog to Digital Converter (ADC). At the receiver side, a robust reconstruction algorithm based on a combination of ℓ1-ℓ1-optimization and Block Sparse Bayesian Learning (BSBL) framework is presented to reconstruct the original bio-signals from the compressed bio-signals. The proposed architecture allows reducing the sampling rate to 25% of Nyquist Rate (NR). In addition, the proposed architecture reduces the power consumption to 40%, Percentage Residual Difference (PRD) to 24%, Root Mean Squared Error (RMSE) to 2%, and the computation time from 22 s to 9.01 s, which provide good background for establishing wearable wireless healthcare systems. The proposed architecture achieves robust performance in low Signal-to-Noise Ratio (SNR) for the reconstruction process.

Silicon photonic interconnects hold great promise in meeting the high bandwidth and low-energy demands of next-generation interconnects. System-level driven electronic-photonic co-design is the key to improving the bandwidth density and energy efficiency. In this study, a comprehensive co-optimization framework is developed for high-speed silicon photonic transmitters utilizing compact models and a detailed optical simulation framework. Given technology and link constraints, microring and Mach-Zehnder transmitter designs are optimized and compared based on a unified optical phase shifter model. Non-return-to-zero (NRZ) and pulse-amplitude-modulation-4 (PAM-4) modulation schemes are analyzed and compared for microring-based transmitters. Using the co-design approach, a monolithic 40Gb/s optical NRZ transmitter based on microring modulators is designed and demonstrated in zero-change 45nm CMOS SOI process. Electronic-photonic co-design with the high swing driver enables this transmitter to achieve total energy efficiency of 330fJ/b and the photonics and modulator driver area bandwidth density of 6.7 Tb/s/mm2. This dissertation also discusses the design and demonstration of the first full silicon photonic interconnect on a 3D integrated electronic-photonic platform. These results make the microring-based silicon photonic transceivers an attractive solution for the next-generation inter and intra-rack photonic interconnects. Finally, a short-reach laser-forwarding coherent link architecture is proposed to further improve the energy efficiency of silicon photonic interconnects. The key concepts of the proposed architecture are verified experimentally with microring-based silicon photonic transmitters. The architecture saves the laser power by 6-7.5x and could enable complex modulation schemes for the future short-reach optical links.

We consider incremental redundancy (IR) hybrid automatic repeat request (HARQ) over independent block-fading channels with turbo coding. We consider different cases of channel state information (CSI) at the transmitter: the transmitter has no knowledge of any CSI, or knows the CSI in previous transmission rounds through a perfect feedback channel, or knows both current and previous CSI. The transmitter decides the forward error correction code rate based on the CSI it has. We minimize the energy consumption of turbo-coded HARQ, subject to a packet loss rate constraint. Numerical results show that the energy consumption of HARQ decreases when more CSI information is available at the transmitter. We also compare IR combining with Chase combining and the system without combining, and IR combining yields the least energy consumption.

Data Acquisition Systems (DAS) are used for a variety of applications such as environmental monitoring, indoor climate control, health management and medical diagnostics, traffic surveillance and emergency response, disaster management among others. This paper presents the design of a DAS for monitoring environmental temperature, pressure and relative humidity. The system employs Arduino Uno microcontroller for signal processing and Zigbee transceivers operating on the 2.4 GHz license-free Industrial, Scientific and Medical (ISM) band as communication modules at both the transmitter and receiver ends. While the transmitter board houses the sensors, a GPS module and an LCD, the receiver system is interfaced with a PC which runs a developed MATLAB GUI for data display and analysis and it incorporates an SD card for data storage. The battery-powered system is a low cost, low-power consumption system which serves as a mini-weather station with real-time data logging, wireless communication and tracking capabilities.

Switched-mode RF power amplifiers (PAs) under bitstream modulations such as bandpass or envelope delta-sigma modulations have received increasing attentions over the past years. They have been proposed to overcome a trade-off between linearity and efficiency with an idea to discretize analog envelope from a complex modulation signal into discrete driving points for high efficiency operation. Such amplifiers offer enhanced efficiency under power back-off conditions with pulse train waveforms yet maintain linearity in amplification through digital coding and modulations. The quantization noise generated during a discretization process, however, is a challenge to be rejected properly and restore desired signal.This work presents a switched-mode PA based on the pulsed load modulation (PLM) technique with multi-level envelope delta-sigma modulation (EDSM) to realize broadband efficient amplification of non-constant-envelope signals. PLM technique modulated load impedance to be optimized for dynamic power range and maintained optimum efficiency over 6 dB back-off. Multi-level EDSM introduced additional transition levels and reduced quantization noise power with improved signal to noise ratio.In addition, active noise filtering scheme is proposed with a potential to replace an external high-Q passive bandpass filter in delta-sigma modulation. Multiple PA units were driven by identical signal with different phase. Challenged quantization noise power was suppressed by multi-path combining filtering.The proposed transmitters were demonstrated at X-band using GaN devices. Both 2-level and 3-level EDSM techniques were tested and compared. Two channel active noise filtering is also presented with regard to their quantization noise levels and power efficiencies.

We study the $K=3$ user multiple input single output (MISO) broadcast channel (BC) with $M=3$ antennas at the transmitter and 1 antenna at each receiver, from the generalized degrees of freedom (GDoF) perspective, under the assumption that the channel state information at the transmitter (CSIT) is limited to the finite precision. In particular, our goal is to identify a parameter regime where a simple layered superposition (SLS) coding scheme achieves the entire GDoF region. With $\alpha _{ij}$ representing the channel strength parameter for the link from the $j^{th}$ antenna of the transmitter to the $i^{th}$ receiver, we prove that the SLS is GDoF optimal without the need for time-sharing if $\max (\alpha _{ki},\alpha _{im})\leq \alpha _{ii}$ and $\alpha _{ki}+\alpha _{im}\le \alpha _{ii}+\alpha _{km}$ for all $i,k\in [{3}],m\in [M]$ . The GDoF region under this condition is a convex polyhedron. The result generalizes to arbitrary $M\geq 3$ .

Graphical abstract, Point to point communication in free-space is severely dependent upon the alignment of the transmitter and receiver devices. The simplest low cost method for the alignment is achieved by utilising two geographical coordinates and an electronic compass. However, some regions of the Earth have a strong magnetic deviation that can introduce large errors to such systems. Other known methods, that can be utilised are a radio direction finder or stars sensor however these methods are too expensive. Here, we present a system which uses three GPS coordinates for the alignment of the transmitter and the receiver, of which two coordinates are measured on the transmitter side, while the receiver is previously known. The transmitter side positions can be relocated for convenience. The methods were tested using Google™ Maps for a long distance within the northern and southern hemisphere, while the experiment was performed for a short distance within the southern hemisphere. The system was developed based on the following considerations: • Algorithm Implementable into a Micro-Controller Unit (MCU) or a standard computer. • The local magnetic deviation does not have any influence on the method. • Can be use where the internet connection is not available, such as mountains and others remote areas.

In this paper, we make an investigation of robust beamforming for secure directional modulation in the multiuser multiple-input and multiple-output systems in the presence of direction angle measurement errors. When statistical knowledge of direction angle measurement errors is unavailable, a novel robust beamforming scheme of combining main-lobe-integration and leakage is proposed to simultaneously transmit multiple different independent parallel confidential message streams to the associated multiple distinct desired users. The proposed scheme includes two steps: designing the beamforming vectors of the useful confidential messages and constructing artificial noise (AN) projection matrix. Here, in its first step, the beamforming vectors for the useful confidential messages of desired user $k$ are given by minimizing the useful signal power leakage from the main-lobe of desired user $k$ to the sum of main-lobes of the remaining desired directions plus main-lobes of all eavesdropper directions. In its second step, the AN projection matrix is constructed by simultaneously maximizing the AN power leakage to all eavesdropper directions such that all eavesdroppers are disrupted seriously, where AN is viewed by the transmitter as a useful signal for eavesdroppers. Due to independent beamforming vectors for different desired users, a more secure transmission is achieved. Compared with conventional nonrobust methods, the proposed method can provide a significant improvement in bit error rate along the desired directions and secrecy-sum-rate toward multiple desired users without needing the statistical property or distribution of angle measurement errors.

Power amplifiers (PAs) determine much of the efficiency and linearity of transmitters in wireless communication systems, both on the base station side and in the handset device. With the move to third-generation (3G) communication systems as well as other systems such as Ultra-Wideband (UWB), a higher linearity is required due to envelope variations of the radio frequency (RF) signal. The traditional way of guaranteeing sufficient linearity is backing off the PA; however, this results in a significant drop in efficiency, and thus in reduced battery lifetime for the handheld device and increased cooling requirements for the base station. With the current energy costs, and increased density of base stations, this is fast becoming an important issue. A second issue in current wireless communication systems is the requirement for a certain range of transmitter output power control, e.g. for 3G systems. Depending on the distance to the base station, a difference in handset output power in the range of tens of dB may occur. If the PA efficiency is peaking for maximum output power, and is reduced considerably for lower output power, the average efficiency of the transmitter calculated over its full output power range of operation will be low. Thus, efficiency improvement for lower output power is an important aspect in transmitter design. Moreover, current wireless communication handsets require a multi-band/multi-standard approach, so that several communication standards are incorporated in one device. Ideally this would all be achieved by one PA, but current standard is that multiple PAs are used for multiple standards, in worst case each with its bulky, costly output filter. In order to address efficiency and linearity issues, different transmitter architectures have been proposed and implemented throughout the years, such as for instance Envelope Elimination and Restoration (EER) or Envelope Tracking (ET), varieties of polar transmission where the envelope and phase of the signal are processed separately. Also, different PA architectures have been used, such as Doherty and switched mode amplifiers, often complemented with linearity-improving measures such as digital predistortion or feedback. With the coming of age of handset production, cost effectiveness has driven wireless communication transceiver design to higher levels of integration. As many building blocks as possible are integrated on the same chip, and the use of external bulky filters is avoided if possible. CMOS technology has been the main choice for this development, due to the possible integration of digital, mixed-signal and analog circuits. However, CMOS was not

This paper investigates multi-mode and orbital angular momentum (OAM) mode data transmission techniques by a using a circular antenna array, operating at 28 GHz. The classical mode excitation of the latter is modified such that in the horizontal plane the antenna array operates as multimode transmitter (i.e., it provides broad- , uni- and/or multi-cast transmission), while in the vertical direction OAM transmission occurs: this dual-functionality by a single antenna-array at 28 GHz is presented for the first time. Specifically, it can transmit/receive in either broad-, uni-, multi-cast mode in the horizontal plane and also, it is capable of generating up to 15 spatially orthogonal OAM modes in the vertical direction. The proposed circular array is designed using twelve, low-complexity, multi-layer microstrip patch antennas with high radiation efficiency. It was tested through full electromagnetic analysis in terms of impedance matching, mutual coupling and radiation pattern. It was, also, fabricated and measured: good agreement between simulated and measurement results was observed. The proposed antenna array is perfect candidate for high spectral efficiency data transmission for 5G and beyond wireless applications., Comment: 11 pages, 10 figures, submitted to the Scientific Reports

Rate-Splitting Multiple Access (RSMA) is a robust multiple access scheme for downlink multi-antenna wireless networks. RSMA relies on multi-antenna Rate-Splitting (RS) at the transmitter and Successive Interference Cancellation (SIC) at the receivers. In this work, we study the performance of RSMA under the important setup of imperfect Channel State Information at the Transmitter (CSIT) originating from user mobility and latency/delay (between CSI acquisition and data transmission) in the network. We derive a lower bound on the ergodic sum-rate of RSMA for an arbitrary number of transmit antennas, number of users, user speed and transmit power. Then, we study the power allocation between common and private streams and obtain a closed-form solution for optimal power allocation that maximizes the obtained lower bound. The proposed power allocation greatly reduces precoder design complexity for RSMA. By Link-Level Simulations (LLS), we demonstrate that RSMA with the proposed power allocation is robust to the degrading effects of user mobility and has significantly higher performance compared to conventional multi-user (massive) Multiple-Input Multiple-Output (MIMO) strategies. The work has important practical significance as results demonstrate that, in contrast to conventional multi-user (massive) MIMO whose performance collapse under mobility, RSMA can maintain reliable multi-user connectivity in mobile deployments.

Fessenden’s work was a milestone in telephony that generated great interest in general public, however, needed many improvements in detection and amplification of signals. This chapter describes the role of thermionic devices in the promotion of wireless telephony systems from the perspective of efficient use of continuous waves as a carrier of sound waves. The thermionic emission was basically carved out of research pursued on the production of light using electric current many personalities like Sir Humphry Davy, James Bowman Lindsay and Frederick Guthrie discovered that red hot or thermally heated conductor can easily lose negative charge but can hold positive charge. John Ambrose Fleming working under James Clerk Maxwell was influenced by Frederick Guthrie also started working in thermionic emission. The invention of the Edison effect provided a mechanism of flow of negative charge. John Ambrose Fleming used the Edison effect in radio detection and constructed a device called Fleming’s Valve. Although Edison and Fleming were successful in demonstrating thermionic emission practically, Lee de Forest adopted a more systematic path to study thermionic emission and invented a device called “Audion” capable of providing ampliation to the detected signal. These devices provided great service for wireless transmission of voice and music and provided a great boost to broadcasting and become also hobbyists business. The amateurist assigned their own call signs to their radio transmitters and the registry was maintained and published by “Wireless Association of America”, This also layed the foundations for the regulations of radio transmitters and the US Department of Commerce took initiative in the direction of licensing. Radio Act of August 1912 came into force with effect from December 13, 1912, for assigning call signs to radio transmitters. This act included the licensing of radio transmitting apparatus and divided radio frequency spectrum for licensing in 187.5 to 1500 KHz wavebands. The invention of regeneration, autodyne and superheterodyne principles greatly improved receiver performance and radio broadcasting widely spread after world war I and during this world war, wireless radio systems were also being used for direction finding and finding enemy targets.

Target localization has a wide range of military and civilian applications in wireless mobile networks. Examples include battle-field surveillance, emergency 911 (E911), traffic alert, habitat monitoring, resource allocation, routing, and disaster mitigation. Basic localization techniques include time-of-arrival (TOA), direction-of-arrival (DOA) and received-signal strength (RSS) estimation. Techniques that are proposed based on TOA and DOA are very sensitive to the availability of Line-of-sight (LOS) which is the direct path between the transmitter and the receiver. If LOS is not available, TOA and DOA estimation errors create a large localization error. In order to reduce NLOS localization error, NLOS identification, mitigation, and localization techniques have been proposed. This research investigates NLOS identification for multiple antennas radio systems. The techniques proposed in the literature mainly use one antenna element to enable NLOS identification. When a single antenna is utilized, limited features of the wireless channel can be exploited to identify NLOS situations. However, in DOA-based wireless localization systems, multiple antenna elements are available. In addition, multiple antenna technology has been adopted in many widely used wireless systems such as wireless LAN 802.11n and WiMAX 802.16e which are good candidates for localization based services. In this work, the potential of spatial channel information for high performance NLOS identification is investigated. Considering narrowband multiple antenna wireless systems, two xv NLOS identification techniques are proposed. Here, the implementation of spatial correlation of channel coefficients across antenna elements as a metric for NLOS identification is proposed. In order to obtain the spatial correlation, a newmulti-input multi-output (MIMO) channel model based on rough surface theory is proposed. This model can be used to compute the spatial correlation between the antenna pair separated by any distance. In addition, a new NLOS identification technique that exploits the statistics of phase difference across two antenna elements is proposed. This technique assumes the phases received across two antenna elements are uncorrelated. This assumption is validated based on the well-known circular and elliptic scattering models. Next, it is proved that the channel Rician K-factor is a function of the phase difference variance. Exploiting Rician K-factor, techniques to identify NLOS scenarios are proposed. Considering wideband multiple antenna wireless systems which useMIMO-orthogonal frequency division multiplexing (OFDM) signaling, space-time-frequency channel correlation is exploited to attain NLOS identification in time-varying, frequency-selective and spaceselective radio channels. Novel NLOS identification measures based on space, time and frequency channel correlation are proposed and their performances are evaluated. These measures represent a better NLOS identification performance compared to those that only use space, time or frequency.

In the near future, it is envisioned that cellular networks will have to cope with extensive Internet of Things (IoT) devices. Therefore, a required feature of cellular IoT will be the capability to serve simultaneously a large number of devices with heterogeneous demands and qualities of Channel State Information at the Transmitter (CSIT). In this paper, we focus on an overloaded Multiple-Input Single-Output (MISO) Broadcast Channel (BC) with two groups of CSIT qualities, namely one group of users (representative of high-end devices) for which the transmitter has partial knowledge of the CSI, the other group of users (representative of IoT devices) for which the transmitter only has knowledge of the statistical CSI. We introduce Rate-Splitting Multiple Access (RSMA), a new multiple access based on multi-antenna Rate-Splitting (RS) for cellular IoT. Two strategies are proposed, namely, Time Partitioning-RSMA (TP-RSMA) and Power Partitioning-RSMA (PP-RSMA). The former independently serves the two groups of users over orthogonal time slots while the latter jointly serves the two groups of users within the same time slot in a non-orthogonal manner. We first show at high Signal-to-Noise Ratio (SNR) that PP-RSMA achieves the optimum Degrees-of-Freedom (DoF) in an overloaded MISO BC with heterogeneous CSIT qualities and then show at finite SNR that, by marrying the benefits of PP and RSMA, PP-RSMA achieves explicit sum rate gain over TP-RSMA and all baseline schemes. Furthermore, PP-RSMA is robust to CSIT inaccuracy and flexible to cope with Quality of Service (QoS) rate constraints of all users. The DoF and rate analysis helps us draw the conclusion that PP-RSMA is a powerful framework for cellular IoT with a large number of devices., 30 pages, 10 figures, submitted to the potential transaction for publication

Full-color smart displays, which act both as a display and as a high-speed visible light communication (VLC) transmitter, can be realized by the integration of red-green-blue micron-sized light emitting diodes (micro-LEDs) onto a common platform. In this work, we report on the integration of aluminum gallium indium phosphide red micro-LEDs onto diamond and glass substrates by micro-transfer printing and their application in VLC. The device on-diamond exhibits high current density and bandwidth operation, enabled by diamond’s superior thermal properties. Employing an orthogonal frequency division multiplexing modulation scheme, error-free data rates of 2.6 Gbps and 5 Gbps are demonstrated for a single micro-LED printed on-glass and on-diamond, respectively. In a parallel configuration, a 2x1 micro-LED array achieves error-free data rates of 3 Gbps and 6.6 Gbps, on-glass and on-diamond, respectively.

Ultrasonic Power Transmission (UPT) has gained attention for powering implanted diagnostic devices due to its non-invasive properties. However, UPT in free-space is still less exploited with considerable potential for powering Wireless Sensor Networks (WSNs). An important challenge in understanding the significant parameters for a UPT system is to comprehend the losses and quantify the limitations of the technology in terms of distance, frequency and transmission power (ISO226). In this work, the authors attempt to model the transmission link of an UPT system, identifying variables which can be modified for obtaining maximum power output from the wireless power transfer through formulation and experimental results. Ultrasonic transducers of two varying frequencies were used in free space power transmission to understand the absorptive and geometric attenuation of sound waves in air, experimentally. A measured power of 6.3$\mu$W(40kHz) and 8. 3nW(100kHz) was observed over 30cm. These observations may enable acoustic powered WSNs in automobiles powering multi-nodes using single transmitter.

Inductive power transfer has gained significant interest by researchers over the last decade. The technology is showing great potential for inclusion in home appliances, industrial devices, biomedical implants and automotive vehicles. The efficiency of a wireless power transfer system (WPTS) is of utmost interest and is proportional to the coupling factor and quality factor of the transmitter and receiver coils used. Existing methods to calculate the efficiency assume fundamental harmonic approximation (FHA) at the resonant frequency, use SPICE software, and rely on experimental results. The AC resistance of the coils increase exponentially with frequency and is a vital parameter for the analytical calculation of the efficiency. The best-known methods to calculate the AC losses of the coils are the Ferreira's method, Dowell's method, or a modified version of these methods. Approaches involving electromagnetic field solvers require high computational time, and are not practical if the wire consists of thousands of twisted strands. Due to that, the focus of this paper would be on 1D analytical calculations. Experimental results show that Dowell's and Ferreira's method overestimate the AC losses. Moreover, these methods are unable to approximate the AC resistance of litz wire accurately at high frequencies. Error could exceed 100%. This paper proposes a modified Ferreira's method to calculate the AC resistance of WPTS coils and a novel method to calculate the efficiency of a WPTS at any operational frequency considering higher order harmonics. Lastly, SiC and GaN converters are compared for an efficiency check for high power applications.

This paper considers the secrecy performance of several schemes for multi-antenna transmission to single-antenna users with full-duplex (FD) capability against randomly distributed single-antenna eavesdroppers (EDs). These schemes and related scenarios include transmit antenna selection (TAS), transmit antenna beamforming (TAB), artificial noise (AN) from the transmitter, user selection based their distances to the transmitter, and colluding and non-colluding EDs. The locations of randomly distributed EDs and users are assumed to be distributed as Poisson Point Process (PPP). We derive closed form expressions for the secrecy outage probabilities (SOP) of all these schemes and scenarios. The derived expressions are useful to reveal the impacts of various environmental parameters and user's choices on the SOP, and hence useful for network design purposes. Examples of such numerical results are discussed., Comment: Paper accepted for publication in IEEE Transactions on Information Forensics and Security

Unmanned Aerial Vehicles (UAVs), a.k.a. drones, are increasingly used for different tasks. With more drones in the sky, the risk of accidents rises, sparkling the need for conflict management solutions. Aircraft use a system called Automatic Dependent System-Broadcast (ADS-B) to continuously broadcast their position and speed but this system is not suitable for small drones because of its cost, complexity and capacity limitations. Broadband technologies such as Wi-Fi beacons are more suited for such dense scenarios, and they also offer the benefit of wide availability and low cost. The main challenges for Wi-Fi are (a) the multi-channel nature of the technology makes transmitter and receiver coordination difficult, and (b) standard chipsets are not designed for frequent broadcast transmission and reception. In this paper, we propose and analyze a multi-channel position broadcast solution that is robust against jamming and achieves a reliable location update within 125~ms. In addition, we implement the protocol on inexpensive embedded Wi-Fi modules and analyze the hardware limitations of such devices. Our conclusions are that even on the simplest Wi-Fi chipsets, our protocol can be implemented to achieve a realistic location broadcast solution that still perfectly mimics simulation and analytical results on the lab bench and still can achieve approximately 4~message/s throughput at a distance of 900~m on flying UAVs.

The last decade has witnessed a tremendous growth in wireless communications. Consumer demands for battery-operated mobile devices with versatile, high data-rate communication capabilities that are of low cost, small form-factor and long operating cycle have motivated the research on fully-integrated, back-off-efficient and coexistence-friendly wireless transceivers in CMOS VLSI technology. However, the full integration of an efficient CMOS power amplifier (PA) into such a transceiver is still among the most difficult challenges towards a true System-On-Chip (SOC) solution. This thesis investigates the PA efficiency enhancement techniques for a complete power transmitter system that is fully-integrated and coexistable. Direct digitally modulated transmitter architecture has been identified as one of the most promising solutions to the above challenges. Within such a transmitter, the PA efficiency is able to back off from a high peak efficiency at least with class-B characteristic; meanwhile, the transmit linearity can be more easily improved by digital predistortion due to the direct digital modulation scheme. To validate such a promising architecture, we have built a fully-integrated CMOS digital power transmitter for the IEEE 802.11g 54Mbps application. System-level considerations and design choices are presented with an aim for low out-of-band noise and good transmit linearity. As the core of the transmitter, the RF switching PA is designed for high efficiency with minimum number of on-chip passives that only exercise an accurate control over fundamental and second-harmonic terminations. The class-B efficiency back-off characteristic is further improved by a dynamic impedance modulator which boosts the PA drain impedance at a low instantaneous envelope level. Open-loop phase interpolator based topology is used for the polar phase modulator, which achieves wideband phase modulation with competitive power consumption. Digital baseband filtering is fully optimized at both the algorithm and the hardware level, which offers larger than 60dB attenuation on the close-in spectral images with reduced filter complexity. The prototype has been implemented in a 65nm bulk CMOS technology and has demonstrated a combination of good output power, overall efficiency and spectral purity with a very high level of system integration.

DOI: 10.5152/iujeee.2018.1819Cognitive radio (CR) technology presents a mechanism for efficient spectrum usage. Spectrum sensing is an essential CR function which includes an intelligent signal processing algorithm to identify the vacant frequency bands. Cooperative spectrum sensing (CSS) has been widely adopted to improve the performance of CR networks. Unfortunately, CR networks are vulnerable to security threats. In this study, we propose an optimal threshold selection approach to address one of the most important attacks called primary user emulation attack (PUEA). In PUEA, a malicious attacker mimics some important primary signal features and deceives CR sensors to prevent them from accessing the available channels. In this study, we assume a malicious PUEA which is relatively located near the potential user (PU) transmitter and senses the spectrum and accurately detects the vacant frequency bands to transmit its fake signal. We estimate attack strength and then apply the K-out-of-N rule to obtain an optimum and dynamic threshold K, minimizing the global error probability. Here, the attack strength is defined as the ratio of the average transmission power of the PUEA to the average power of the PU. The achieved simulation results indicate that the performance of the suggested method is satisfactory in detecting the malicious PUEA compared with conventional methods., DOI:10.5152/iujeee.2018.1819Cognitiveradio (CR) technology presents a mechanism for efficient spectrum usage.Spectrum sensing is an essential CR function which includes an intelligentsignal processing algorithm to identify the vacant frequency bands. Cooperativespectrum sensing (CSS) has been widely adopted to improve the performance of CRnetworks. Unfortunately, CR networks are vulnerable to security threats. Inthis study, we propose an optimal threshold selection approach to address oneof the most important attacks called primary user emulation attack (PUEA). InPUEA, a malicious attacker mimics some important primary signal features anddeceives CR sensors to prevent them from accessing the available channels. Inthis study, we assume a malicious PUEA which is relatively located near thepotential user (PU) transmitter and senses the spectrum and accurately detectsthe vacant frequency bands to transmit its fake signal. We estimate attackstrength and then apply the K-out-of-N rule to obtain an optimum and dynamicthreshold K, minimizing the global error probability. Here, the attack strengthis defined as the ratio of the average transmission power of the PUEA to theaverage power of the PU. The achieved simulation results indicate that theperformance of the suggested method is satisfactory in detecting the maliciousPUEA compared with conventional methods.

This paper proposes the optimum resonance frequency of a transmitter (Tx) coil driven by a series-resonant inverter in wireless power transfer. While typical wireless power systems include a dc–dc buck converter at the receiver (Rx) side to output a constant voltage, it is revealed that the Tx design affects the operation of an Rx buck converter and Tx-to-Rx transfer efficiency. Specifically, it is found that if the resonant frequency of the Tx coil is too close to inverter switching frequency, the Rx buck converter is not allowed to operate at high duty cycle, which degrades the Tx-to-Rx transfer efficiency. Therefore, the Tx resonance frequency should be sufficiently lower than the inverter switching frequency in order to allow high-duty operation of the Rx buck converter. This is to guarantee high Q-factor of the Rx coil and thus the Tx-to-Rx transfer efficiency. The required Tx resonant frequency is proposed as a function of magnetic coupling, Rx coil property, Rx buck duty cycle, and Rx load condition. Simulation and experimental results with a constant-output-voltage system support the discussions.

Wireless dynamic charging is one of the most promising power supply methods for electric vehicles (EVs), which can reduce battery volume and extend EVs’ range. Stable output power and high system efficiency are two of the most important features for practical applications of wireless dynamic charging. For the low-speed application scenarios of dynamic charging, an efficiency optimization method is proposed to improve the system efficiency while regulating the output voltage. Two overlapped DD coils are employed to generate an enhanced magnetic field without dead points. An optimized current control method is proposed to adjust the direction and the ratio of the two transmitter currents as the receiver moves along the track, dynamically. By applying this method, the efficiency of dynamic charging system can be optimized while the output power can be regulated to the desired value at the same time. A 600 W prototype is established to validate the performance of the proposed method. The experimental results show that the system efficiency for dynamic charging reaches 88.3%–90.4% with the proposed method. The maximum efficiency improvement of proposed algorithm is 2.3% compared to that with the same energized currents for both DD coils.

In this paper, an efficient I/Q management with Q-learning-based transmitter swing adjustment and receiver compensation is developed for energy-efficient 2.5-D memory-logic integration. The proposed approach is able to achieve significant power reduction over other state-of-the-art methods.

We investigate the effect of intermediate resonators (i.e., intermediate receiver (i-Rx) or relay) on the power transfer efficiency (PTE) for nonradiative wireless power transfer (WPT) with transmitter (Tx), intermediate-resonators, and end receiver (e-Rx). Specifically, we consider WPT systems with two different types of an intermediate resonator: 1) WPT relay systems, where the relay has no load resistor and just forwards the power from the Tx to the e-Rx, and 2) WPT i-Rx systems, where both i-Rx and e-Rx have a load resistor each and the power transmitted by the Tx is consumed at each Rx. Using an equivalent circuit model, we derive a closed-form solution for representing the optimal coupling coefficients between the Tx and the intermediate resonator for a given placement of the intermediate resonator and the e-Rx, i.e., $k_{12,\rm {opt}}$ for WPT i-Rx systems and $k_{1r,\rm {opt}}$ for WPT relay systems, respectively. The analytical result indicates that the quality factors of resonators have a great effect on determining their optimal positions. We also provide performance comparisons between the considered WPT systems. From the result, it is observed that $k_{12,\rm {opt}}$ is always larger than $k_{1r,\rm {opt}}$ , which indicates that the optimal position of the Tx is closer to the i-Rx rather than the relay. Moreover, in this case, WPT i-Rx systems can attain a higher PTE than WPT relay systems. Performing experiments under a variety of scenarios, we verify that the analytical results are in concordance with the measured ones.

In this brief, we present a virtual channel (VC) optimization approach for overloaded multiple-input multiple-output (MIMO) systems. With this approach, a VC vector is generated at the transmitter, which is combined with the actual wireless channel matrix to form the overall transmission channel matrix. Through VC optimization, the overall transmission channels can be properly adjusted in favor of the signal detection, leading to an improved performance. Moreover, we investigate the overloaded MIMO system in which the number of receive antennas equals the number of transmit antennas. By using superposition VC method, this overloaded MIMO system allows more number of data streams to be transmitted than the number of transmit antennas. The methods for obtaining the optimal VC vector are presented. Simulation results illustrate the effectiveness of the proposed approaches.

The problem of transmitter source localization in a dense urban area has been investigated where a supervised learning approach utilizing neural networks has been adopted. The cellular phone network cells and signals have been used as the test bed where data are collected by means of a smart phone. Location and signal strength data are obtained by random navigation and this information is used to develop a learning system for cells with known base station location. The model is applied to data collected in other cells to predict their base station locations. Results are consistent and indicating a potential for effective use of this methodology. The performance increases by increasing the training set size. Several shortcomings and future research topics are discussed. (C) 2017 Elsevier Ltd. All rights reserved.

Multiple transmitters powering a single receiver simultaneously is a good alternative to upgrade the power capacity of the wireless power transfer (WPT) system by using multiple modular inverters manufactured in a larger quantities, since the demand for high power applications is on the rise. A multiple overlapped transmitters based WPT system is presented in this paper. In order to alleviate the effects of the cross couplings between the transmitters, additional capacitors are adopted in the transmitters and the configuration of additional capacitors is provided. Virtual active and reactive powers are defined to decompose the transmitter current into active and reactive components. A transmitter current control scheme based on the proposed current decomposition method consisting of one reactive current control loop and one active current control loop is also presented in this paper. Finally, a low-scale experimental setup using two overlapped transmitters WPT system is provided to verify the proposed approach. The experimental results indicate that the proposed method could improve the stability of output voltage control and achieve minimal current difference amongst transmitters. Besides, the overall system efficiency is improved to 90.34% with the proposed control method at 1.45 kW output power, which demonstrates that the proposed method is a potential solution for high power applications.

In this paper, a complete wireless power transfer system with transmitter (TX) and receiver (RX) chips is presented. Both RX local and TX wireless output voltage regulations are achieved by the proposed constant-idle-time control without using any wires or additional discrete components, such as MCU, DAC, various kinds of controllers, and decoders, which were required in previous works. The system and circuitry design complexity is significantly reduced. Both TX and RX chips are fabricated in the TSMC 65-nm process with standard 2.5-V I/O devices, and the RX coil is fabricated using flexible printed circuits to demonstrate the performance for implantable applications. Up to 17.5% end-to-end total efficiency improvement is observed when enabling the wireless constant-idle-time controlled TX voltage regulation, and an instant load-transient response is also achieved. As a result, compared to previous works, this design achieves a higher total efficiency, a faster load-transient response, and a higher level of integration with a much lower system and circuitry design complexity.

This paper presents an all-digital polar pulsewidth modulated (PWM) transmitter for wireless communications. The transmitter combines baseband PWM and outphasing to compensate for the amplitude error in the transmitted signal due to aliasing and image distortion. The PWM is implemented in a field programmable gate array (FPGA) core. The outphasing is implemented as pulse-position modulation using the FPGA transceivers, which drive two switch-mode power amplifiers fabricated in 130-nm standard CMOS. The transmitter has an all-digital implementation that offers the flexibility to adapt it to multi-standard and multi-band signals. As the proposed transmitter compensates for aliasing and image distortion, an improvement in the linearity and spectral performance is observed as compared with a digital-PWM transmitter. For a 20-MHz LTE uplink signal, the measurement results show an improvement of up to 6.9 dBc in the adjacent channel leakage ratio.

In recent years, wireless power technology has been promoted for recharging systems for portable devices that are used in everyday life. The conventional technology used for this purpose, which is based on magnetically coupled resonators, has provided promising results but is limited in range and direction at the receiving terminal. In this paper, we propose an omnidirectional wireless power transfer (WPT) system with a novel cubic transmitter to achieve relatively high efficiency. Specifically, a single power source is utilized to drive the current of the transmitter without phase and current control methodology. Energy delivery is transmitted to the receiver through magnetic resonant coupling in the medium-range WPT mode. In addition, an equivalent circuit model of a coupling two-coil system is derived and mathematically analyzed. The efficiency of the proposed omnidirectional WPT system depending on the various distances between the transmitter and the receiver, as well as the transmitter structure, is evaluated via analysis and implementation. Finally, practical experimental results from the resonant coupling system confirm the theoretical analysis of the cubic transmitter and the omnidirectional power transfer capability, which demonstrate approximately 60% power transfer efficiency.

Interference alignment (IA) is a remarkable technique to manage interference, and artificial noise (AN) can be utilized to combat one main threat of security, passive eavesdropping. Nevertheless, in the existing schemes AN is only eliminated at each legitimate receiver, which is a waste of energy. In this paper, we propose an AN assisted IA scheme with wireless power transfer (WPT). In the proposed scheme, AN is generated by each transmitter along with data streams, which can disrupt the eavesdropping without introducing any additional interference. Due to the fact that the transmit power of AN should be high enough to ensure the security, energy harvesting (EH) is also performed in the scheme. A power splitter is equipped at each receiver, which can divide the received signal, including desired signal, interference and AN, into two parts: one for information decoding (ID) and the other for EH. To optimize the antieavesdropping performance, the total transmit power of AN is maximized by jointly optimizing the information transmit power and the coefficient of power splitting, with the requirements of signal-to-interference-plus-noise ratio (SINR) and harvested power satisfied. Due to the non-convex nature of the problem, a suboptimal solution is also derived to calculate the closed-form solutions with extremely low computational complexity. Extensive simulation results are presented to show the effectiveness of the proposed scheme.\ud

In this paper, we propose a hybridly connected structure for hybrid beamforming in millimeter-wave (mmWave) massive MIMO systems, where the antenna arrays at the transmitter and receiver consist of multiple sub-arrays, each of which connects to multiple radio frequency (RF) chains, and each RF chain connects to all the antennas corresponding to the sub-array. In this structure, through successive interference cancelation, we decompose the precoding matrix optimization problem into multiple precoding sub-matrix optimization problems. Then, near-optimal hybrid digital and analog precoders are designed through factorizing the precoding sub-matrix for each sub-array. Furthermore, we compare the performance of the proposed hybridly connected structure with the existing fully and partially connected structures in terms of spectral efficiency, the required number of phase shifters, and energy efficiency. Finally, simulation results are presented to demonstrate that the spectral efficiency of the hybridly connected structure is better than that of the partially connected structure and that its spectral efficiency can approach that of the fully connected structure with the increase in the number of RF chains. Moreover, the proposed algorithm for the hybridly connected structure is capable of achieving higher energy efficiency than existing algorithms for the fully and partially connected structures.

Power-digital-to-analog converters (DAC) circuits for high capacity and high spectral efficiency optical transmitters are presented in this paper. They are based on a 0.7- μ m InP DHBT semiconductor process, of which main differentiating characteristics are highlighted. We introduce the Power-DAC circuit concept, its usual architectures, and we provide design details of its latest generation. Named SPDAC, it integrates multiplexing front-end blocks composed of three 2:1-selectors. With this architecture, the input interface operates at half rate. 107-GBd operation for PAM-4 and 64-GBd for PAM-8 were demonstrated with quality suitable for direct detection and datacenter applications. 90-GBd operation in a PDM-64QAM transmitter with coherent detection was also enabled by SPDAC modules. With 3.7 to 4 V differential output voltage swing, Power-DAC circuits can be directly connected to different types of E/O modulators (Mach–Zehnder, EAM). We show in particular how the SPDAC circuit enables single-carrier transmission at 100-GBd in PAM-4 IM/DD modulation for datacenters. In this experiment, the feed-forward equalizer combined with stacking a

A 1-V 10-Gb/s/pin single-ended transceiver with a controllable active inductor-based output driver and adaptively calibrated cascaded-equalizer with infinite impulse response and finite impulse response filters for a post-LPDDR4 interface in a 65-nm CMOS technology is proposed. The proposed cascaded-equalizer removes the received long-tail inter symbol interference with the help of an IIR filter while the coefficients for the cascaded-equalizer are adaptively calibrated. In addition, the received single-ended ground-terminated data are converted to the differential pair by the proposed input buffer using a calibrated reference voltage. In the transmitter (TX), an output driver with controllable active inductors is proposed to reduce both power consumption and design complexity. At the maximum operating data rate, the measured power efficiencies of TX and receiver are 1.16 and 3.02 pJ/b, respectively, excluding the power dissipation of internal phase locked loop. In addition, the overall active area is 0.0091 mm2.

This paper represents a new scheme using the drill strings as the medium to deliver logging information via a compressional acoustic wave. Considering the comb-type frequency characteristics of an acoustic channel, non-contiguous orthogonal frequency division multiplexing (NC-OFDM) has been selected as a promising technique for achieving high-rate transmission with high spectral efficiency and immunity to multipath channels. However, the irregular pilot design and high peak-to-average power ratio (PAPR) halted the widespread application of NC-OFDM. To overcome these two disadvantages, we propose an adaptive pilot design scheme in which the dynamic range of available frequency is pre-simulated and an improved discrete Fourier transformation based least square (PDFT-LS) channel estimation scheme to obtain the channel characteristics and an improved selected mapping (PSLM) scheme with low-complexity to reduce the PAPR of the transmitter are applied. Computer simulation and circuit test results are presented to demonstrate that the data transmission rate can be in excess of 500 bps along a 53.76 m experimental channel under the conditions of the simulated impulse noise and surface noise with a low bit error rate (BER), and the PAPR reduction performance can reach almost the same as that of a conventional SLM (CSLM) scheme.

Frequency modulation continuous wave (FMCW) radar receivers generally suffer from transmitter leakage due to insufficient TX-to-RX isolation. One of the effective approaches to solving this problem is using reflected power cancelers (RPCs) that cancel the leakage from the transmitter adaptively. In this paper, a linear time invariant (LTI) model of the RPC is derived in order to carry out a comprehensive study of the mechanism of leakage cancelation and output noise performance for CW radar applications. Loop frequency responses for receiving signal, loop stability, and the influence of dc offset of IQ mixer are analyzed by a simplified transfer function. A detailed noise model of the RPC is established based on the LTI model to study the output noise components of the RPC under a large incident leakage, then the internal noise cancelation mechanism is elucidated. A prototype with its operating frequency range from 820 to 1020 MHz at UHF band is implemented. Measured loop frequency responses are in agreement with simulation results obtained with the proposed model. Furthermore, measured cancelation ratios for leakages of different ramp rates comply with the normalized power gain at corresponding frequency offsets. The input-referred receiving noise of the RPC prototype is measured to be −155 dBm/Hz at 100-kHz offset under +10-dBm incident leakage power. The proposed LTI model provides a useful tool for the design of high-performance RPC for FMCW systems in different application environments.

This paper proposes a new approach for inductive wireless power transfer (IWPT) tag-to-reader communication. A new technique to achieve transmitter/receiver (Tx/Rx) frequency separation is demonstrated. A two-tone Tx is adopted at the reader, and the third-order intermodulation (IM3) frequency generated by the tag rectifier nonlinearity is used as the Rx carrier, which is modulated by a baseband signal sent by the tag. The uplink signal at the IM3 frequency can be picked up by the reader coil. The IWPT impedance matching networks for both the reader and the tag coil can be reused efficiently, since the IM3 frequency at 5.06 GHz is close to the Tx fundamental frequencies at 4.94 and 5 GHz. Due to the Tx/Rx frequency separation, the Tx-to-Rx leakage at the Rx frequency can be suppressed by external filters to improve the Rx signal-to-noise ratio (SNR). The proposed technique is implemented within a 5-GHz IWPT system, and a tiny CMOS tag with a coil size of only 0.01 mm2 is used. This paper also implements conventional direct and intermediate frequency-based backscattering uplinks for comparison, and the proposed IM3 uplink is able to improve the Rx SNR by more than 20 dB. The achieved uplink data rate (100 kb/s) is also higher than the published work (20 kb/s) that adopted the conventional backscattering method.

In this paper, a fully synthesizable all-digital transmitter (ADTX) is first proposed. This transmitter (TX) uses Cartesian architecture and supports wide-band quadratic-amplitude modulation with wide carrier frequency range. Furthermore, the design methodology for ADTX and corresponding bandpass filter is discussed. This TX is synthesized with digital register transfer level-graphic database system flow, and can be easily implemented in any standard CMOS technology. An exemplary TX is synthesized by TSMC 28-nm standard cell library with extremely small area (0.0009 mm2) and supports carrier frequency as high as 6 GHz with excellent error vector magnitude (

We consider the secrecy rate for the multiple-input single-output optical wireless scattering communication, where the detected signal can be characterized by discrete photoelectrons. Assuming a legitimate receiver and an eavesdropper, we propose two secure communication protocols, the non-jamming protocol, and the cooperative jamming protocol, where for the former the transmitter does not send jamming signals but for the latter the transmitter sends jamming signals. We formulate the corresponding power and duty cycle optimization problems for both protocols. We also analyze the properties on the optimal solution, and adopt the alternating optimization to obtain a tractable solution. Moreover, we analyze the condition on the positive secrecy rate for the case where all the sub-channels to the receiver are weaker than their counterparts to the eavesdropper, where the secrecy transmission cannot be realized via a non-jamming protocol. The performance of the proposed two protocols is evaluated by numerical results. It is seen that for the iterative optimization solution, two to three iterations suffice for the convergence of the secrecy rate.

A prototype of a high-resolution synthesized magnetic field focusing (SMF) system for a possible application to radio frequency (RF) barcodes is proposed in this paper. It was recently found that coordinated control of array coil currents makes it possible to focus magnetic field, which is requisite for medical imaging, wireless power, and RF identification. Different from conventional phased array RF antennas, SMF is independent of frequency, which is quite promising for various applications. In this paper, an array of rectangular air coils is proposed, and various implementation issues, such as accurate control of coil currents and compact RF barcode design, are newly suggested. A prototype of an SMF system composed of a transmitter (Tx), an RF barcode, and a receiver (Rx) was implemented at below 1 MHz operating frequency. The Tx includes modularized control drivers, full-bridge switching converters, and 16 arrayed air coils, where the RF barcodes proposed in this paper include a self-resonating circuit at 20 mm × 20 mm and a tunable resonating circuit at 15 mm × 15 mm. In this way, a 5 mm resolution at a distance of 20 mm was achieved for the Tx arrayed air coils with spacing of 5 mm, which is about four times sharper magnetic field focusing compared to a nonfocusing conventional coil. Furthermore, the proposed SMF system allows the designed 5-bit RF barcode array to be fully distinguishable at a 15 mm distance.

A new wireless power transfer (WPT) system based on ball-joint structure is presented in this paper. A ball-joint WPT system consists of a ball structure with a mechanical rod attached to the ball and a ball socket that accommodates the ball structure. This ball-joint structure comprises at least one winding in the ball structure and at least one winding in the ball socket structure. The ball structure can be flexibly rotated over a wide range of angle inside the ball socket, while wireless power can still be transferred from the transmitter winding to the receiver winding through magnetic resonance. The magnetic coupling coefficient between the transmitter and receiver coil over a wide rotating angular range has been analyzed and experimentally checked. Experimental results confirm that an energy efficiency of up to 81% can be achieved.

Wireless transmitters (Tx) targeting Internet-of-things (IoT) applications impose tough end-to-end efficiency requirements. The frequency synthesis problem is usually solved by incorporating a variant of the phase-locked loop. However, power-hungry dividers and large loop time constants hurt the aggregated Tx power consumption and produce systems with slow start-up and turnaround times, particularly when operating at low output power. This paper demonstrates an agile ultralow power and energy-efficient transmitter architecture for IoT applications to address these concerns. The Tx leverages the characteristics of the wideband frequency-shift keying modulation and uses an openloop ring oscillator based on a vertical delay cell as its local oscillator (LO) generator. When followed by an edge-combiner-type power amplifier, the required LO operating frequency drops to one-third of the RF frequency, which further reduces the Tx power consumption. Moreover, LO frequency correction is achieved through a digitally assisted scheme with specially designed delay cells for fast frequency calibration. The Tx was fabricated in 0.18- $\mu \text {m}$ CMOS technology and occupies an active area of 0.112 mm2. The experimental results show a Tx energy efficiency of 0.2 nJ/b for a 3-Mb/s data rate and a normalized energy efficiency of 3.1 nJ/b $\cdot $ mW when operating at a maximum output power of −10 dBm.

A time-based (TB) receiver (RX) with a 2-tap TB decision feedback equalizer (DFE) is proposed for mobile DRAM interface. The TB RX consists of a voltage-to-time converter (VTC), a TB DFE, and a time comparator. The VTC converts the RX input voltage to a time difference between two VTC outputs by using the difference in clock-to-Q delays between two latches with different input offset voltages. The TB DFE inserts an additional delay to one of the two VTC outputs and bypasses the other VTC output to increase the time opening. The time comparator makes a decision with the first arriving edge of the two outputs of the TB DFE. While the feedback loop delay must be less than 1 UI for proper operation in the conventional voltage-based DFE, the TB DFE allows the feedback loop delay up to 1.43 UI in this paper. A transmitter (TX) transmits a single-ended signal of 200-mV swing by using an n-over-n voltage-mode driver. The transceiver in a 65-nm CMOS process achieves a 12.5 Gb/s with a 0.8-V supply through a 15-inch FR-4 channel of 14-dB loss. The TX and RX chip consume 4.3 and 3.4 mA, respectively. The energy efficiency is 0.49 pJ/b.

A new spectrum sensing scheme based on spatial-temporal opportunity detection is proposed in this paper. To verify the practicability and validity of the method, we proposed a more real 2-D cognitive wireless sensor network (CWSN) topology model, where the primary signal transmitter is distributed in a given sensing area randomly at each iteration. The proposed 2-D sensing nodes selective fusion scheme consists of three main sensing steps: non-cooperative spectrum sensing for all wireless sensor nodes, location estimation, and the decision fusion of selected sensing nodes. One other thing to note is the limitation of energy in CWSN. To save more energy, a sensing nodes selection procedure for energy sufficiency is used to address the problem of too much energy consumption of direct transmissions to the fusion center. Simulation results show that the proposed scheme not only has a desirable property to process the spectrum-heterogeneous problem in spatial-temporal 2-D sensing environment but shows satisfactory detection performance with less energy consumption as well.

The multitier heterogeneous structure of 5G with dense small cells deployment, relays, and device-to-device (D2D) communications operating in an underlay fashion is envisioned as a potential solution to satisfy the future demand for cellular services. However, efficient power allocation among dense secondary transmitters that maintains quality of service (QoS) for macro (primary) cell users and secondary cell users is a critical challenge for operating such radio. In this paper, we focus on the power allocation problem in the multitier 5G network structure using a noncooperative methodology with energy efficiency consideration. Therefore, we propose a distributive intuition-based online learning scheme for power allocation in the downlink of the 5G systems, where each transmitter surmises other transmitters power allocation strategies without information exchange. The proposed learning model exploits a brief state representation to account for the problem of dimensionality in online learning and expedite the convergence. The convergence of the proposed scheme is proved and numerical results demonstrate its capability to achieve fast convergence with QoS guarantee and significant improvement in system energy efficiency.

A 0.1–5.0 GHz software-defined radio (SDR) transmitter for private network wireless communication is presented. A V-I converter with the 3rd-order nonlinearity cancellation and current-mode power-mixers are introduced to improve the CIM3 performance. The complete self-calibration scheme is proposed to alleviate the non-ideal effects, including RF resonant frequency self-tuning, LO leakage and image rejection calibration, output power control. With the self-calibration, the transmitter obtains good robustness in RF operation frequency self-tuning and achieves the average LO leakage of −61 dBc and image-rejection ratio (IRR) of 58 dBc. Moreover, the system verifications have demonstrated 24.5 dBm Pout (output power) with 0.7% EVM, 20 dBm Pout with 1.6% EVM, 6.2 dBm Pout with 2.1% EVM for 905 MHz GSM, 905 MHz EDGE and 3.5 GHz LTE signals, respectively. This SDR transmitter has achieved comparable or even better performance in linearity, CIM3 and power consumption compared with the state-of-the-art reconfigurable transmitters.