With the increasing applications of ultra-high frequency (UHF) radio-frequency identification (RFID) in various fields that require rapid identification of a large number of tags, improving the throughput of RFID systems has become the research focus currently. By modulating tag signals to different Miller-subcarrier frequencies, the frequency division multiple access (FDMA) RFID system with$M$-values of 2 and 6 has been proposed. Furthermore, after analyzing the spectrum of the Miller-coded signal, the tag harmonic signal suppression algorithm, based on the Costas loop, has been proposed, which reconstructs the harmonic interference signal of the first channel and subtracts the interference in the second channel. The suppression performance of the algorithm can reach 14 dB and 11 dB through simulation and experiment. The reader that supports simultaneous query for tags has been designed and developed utilizing the Xilinx XC7Z020 chip and can successfully receive the tag signals in two channels.

As the use of ultrahigh frequency (UHF) radio-frequency identification (RFID) increases in various fields requiring the rapid identification of a large number of tags, research has shifted toward improving the access capacity of RFID systems. This article proposes a frequency division multiple access (FDMA) extension of conventional time division multiple access (TDMA) RFID systems by modulating tag signals to different Miller-subcarrier frequencies, achieving a theoretical throughput limit value of 0.9135 average successfully read tags per slot, which is 2.48 times that of the usually referred dynamic frame-slotted Aloha algorithm. The power spectral density (PSD) of Miller-modulated subcarrier (MMS) sequences is derived to uncover the tag interference caused by the modulation signal sidelobe power within each subchannel. After that, a successive interference cancellation (SIC) scheme is employed in a four-tag signal reception situation, enhancing the simultaneous tag replies interference suppression and achieving a small performance deterioration if compared with a conventional TDMA system. An experimental analysis is also described to show the feasibility of the proposed FDMA extension of TDMA-based UHF RFID systems.

Temperature sensing based on emerging techniques, such as the novel electromagnetic resonant unit, has been the vital research direction. However, current works only focused on the initial and principal verifications, and it is far away to the real application. In this article, a temperature sensor based on mercury-inspired electromagnetic resonant unit holding high-$Q$-factor and with complete circuit system is proposed. The excellent properties of mercury, including the liquid-shape, highly conductivity, and high-temperature sensitivity, are utilized to achieve the effective fusion of such liquid material and high-$Q$-factor electromagnetic resonant unit, so as to realize the integrated design of high-precision temperature sensing. Furthermore, four functional circuits, including signal generation, temperature sensing, signal reception, and signal processing, are designed and constructed, and finally an integrated mercury-inspired electromagnetic resonant-unit temperature sensor system with good temperature sensing performances is realized. Experimental results show that the temperature measured by the proposed sensor is highly consistent with the actual temperature values, with sensing sensitivity up to 1459 mV/ °C. Such achieved high-precision temperature sensor system can be further integrated and can open a new way for the high-precision environment temperature monitoring in the Internet of Thing (IoT) area.

Existing works on sub-pulse-based frequency modulated continuous wave (FMCW) dual-functional radar-communication (DFRC) lack of a complete analysis of the radar processing links and an effective solution to the radar performance deterioration problem. This letter conducts a complete signal modeling for the FMCW-DFRC signal processing. By compensating the changes generated by data modulation, a radar processing scheme based on dual path compensation and splicing (DPCS) is proposed to achieve the same radar performance of an unmodulated FMCW. Numerical results show that compared with the existing FMCW-DFRC works, DPCS achieves a sidelobe suppression enhancement of about 27 dB

In radio-frequency identification (RFID) applications, RFID tags attached to new, misplaced, or counterfeited commodities sometimes may not be timely registered and are unknown for readers. In applications like inventory management and product tracking, these unknown tags pose several challenges for fast tag identification. A simple method to identify unknown tags is to first deactivate the registered known tags, and then collect IDs of the unknown ones. However, this is a nontrivial task. In fact, unknown tags cause interference with the deactivation of known tags. Moreover, the unknown tag collection methods used in existing protocols either suffer severe tag collisions or generate many empty slots, which increases the final execution time. In this article, we propose an efficient unknown tag identification (EUTI) protocol. First, EUTI builds a vector-based filter to exclude the tags that are not expected to reply in each slot, so that EUTI can use both predicted collision slots and singleton slots for unknown tag deactivation and avoid collisions caused by unknown tags. Second, EUTI adopts a reservation mechanism to reduce collision slots and guide each unknown tag to skip empty slots when replying, thus saving execution time. Moreover, we provide a theoretical analysis of EUTI to minimize execution time and extend EUTI to multi-reader scenarios. Numerical results show that EUTI outperforms the state-of-the-art solutions by reducing up to 44.12% in deactivation time, 26.47% in collection time, and 27.75% in total time.

As one of the healthcare development trends, mobile hospital systems nowadays need more advanced means of treatment and diagnosis and require higher data transmission speed and capacity with lower latency. With its ability to simultaneously support a variety of services in a wide range of application scenarios using network slicing technique, the emerging fifth generation communication system (5G) is expected to offer significant communication performances, including higher throughput, higher mobility, higher connection density, higher transmission reliability with lower latency than the current fourth generation (4G). Hence, 5G can serve as an effective transmission means to meet the modern mobile hospital systems requirements. This article proposes a 5G network slicing-based mobile hospital system where two types of slices, namely, enhanced mobile broadband (eMBB) slice and ultrareliable and low-latency communications (uRLLC) slice, are dedicated to the medical data. We propose an optimization method to maximize the throughput of the medical data assigned to the eMBB slice. We also propose a resource allocation algorithm for very high transmission reliability with very low latency of the medical data assigned to the uRLLC slice. Simulation results indicate that our proposed approach can effectively meet mobile hospital systems requirements for data transmission throughput, reliability, and latency from remote sites to hospital centers.

This article describes the design of a hydrogen concentration monitoring system based on ultrahigh-frequency radio-frequency identification (RFID) passive tags, which adopts ISO/IEC 18000-6 Type C standard. Tag devices have been designed by employing a microcontrol unit, making the proposed solution very suitable for low-cost hydrogen concentration measurement in wireless sensor networks. Furthermore, anti-collision capability has been realized by implementing a new true random number generator based on the hydrogen concentration sensing circuit and analog-to-digital converter, without employing any additional device. The correctness of all operations of the RFID system has been experimentally verified in a multiple-tag environment, as well as the hydrogen concentration monitoring capability. Particularly, measurement on an RFID tag prototype developed for the bandwidth 920-925 MHz has revealed that when the ambient temperature is 25 °C and humidity 80%, a maximum error of 9.8% is found within a hydrogen concentration range from 0.24% to 2.4%.

In the last decade, energy harvesting wireless sensor network (EHWSN) has been well developed. By harvesting energy from the surrounding environment, sensors in EHWSN remove the energy constraint and have an unlimited lifetime in theory. The long‐lasting character makes EHWSN suitable for Industry 4.0 applications that usually need sensors to monitor the machine state and detect errors continuously. Most wireless sensor network protocols have become inefficient in EHWSN due to neglecting the energy harvesting property. In this paper, we propose CPEH, which is a clustering protocol specially designed for the EHWSN. CPEH considers the diversity of the energy harvesting ability among sensors in both cluster formation and intercluster communication. It takes the node’s information such as local energy state, local density, and remote degree into account and uses fuzzy logic to conduct the cluster head selection and cluster size allocation. Meanwhile, the Ant Colony Optimization (ACO) as a reinforcement learning strategy is utilized by CPEH to discover a highly efficient intercluster routing between cluster heads and the base station. Furthermore, to avoid cluster dormancy, CPEH introduces the Cluster Head Relay (CHR) strategy to allow the proper cluster member to undertake the cluster head that is energy depletion. We make a detailed simulation of CPEH with some famous clustering protocols under different network scenarios. The result shows that CPEH can effectively improve the network throughput and delivery ratio than others as well as successfully solve the cluster dormancy problem.

With the increasing demand for high‐speed mobile transmissions for 5G networks, the cooperative relay‐aided non‐orthogonal multiple access (CR‐NOMA) has been highly considered. An efficient and reliable CR‐NOMA not only depends on the network mechanism but on the network coding strategy at the relay. Even though conventional strategies have broadly been studied, they suffer from noise accumulation and interference. Lately, the compute‐and‐forward (CpF) strategy has been identified as a potential technique to mitigate interference and enhance outage probability. In this study, the authors present a mathematical formulation to examine the performance of CpF on downlink CR‐NOMA. In the proposed formulation, a two‐stage downlink cooperative relay network is considered to obtain analytical closed‐form expressions of outage probability and bit error rate. The outage probabilities and bit error rates of existing relaying strategies are compared regarding the network model. The theoretical analysis shows that CpF requires half the number of relays desirable in amplify‐and‐forward and decode‐and‐forward strategies to achieve a proportionate outage probability in CR‐NOMA. Finally, we present results to show that at a lower signal‐to‐noise ratio, the integration of CpF and NOMA enhances error performance irrespective of the number of users.

Distance bounding (DB) protocols are crucial solutions against “distance attacks.” Traditional one-hop DB protocols can estimate an upper-bound of the physical distance between two nodes within their communication range, but they fail when this distance exceeds their coverage. Recently, a two-hop DB protocol to verify the proximity of nodes beyond the first hop was proposed. Nonetheless, this approach is still lacking for meeting security requirements of multihop communication scenarios like ad-hoc wireless network. Motivated by this situation and considering security problems of a relay communication scenario, in this paper, we propose a multihop DB protocol, where a node can detect multihop neighbors and verify legality beyond its communication range. First, we present a description of traditional one-hop DB protocols and provide a general model for easily extending them to multihop capabilities. Then, we analyze one-hop and multihop models security giving theoretical and simulated attack success probabilities for different cases, and showing that the proposed solution can better prevent distance attacks.

Distance bounding(DB) protocol is a critical solution to preventing distance attacks. Since the traditional DB protocols can only estimate the upper-bound within its communication range, it fails to work once the distance exceeds its coverage. Currently, the DB protocol is difficult to apply to wireless sensor networks(WSN) to prevent relay attacks, such as wormhole attack which is one of the most serious threats in WSN's routing. In this paper, a multi-hop DB protocol is proposed to estimate the upper-bound with multi-hop nodes, which can help a Central Node(CN) or Cluster Head(CH) node estimate the communication distance upper-bound of all the nodes in a sub-group, even if the nodes don't lie in its direct communication coverage. The proposed scheme not only ensures the safety of the communication, but also optimizes the routing and networking in WSN.

A low-voltage high-swing voltage-biased Colpitts voltage-controlled oscillator (VCO) is proposed for wireless applications. A small capacitive voltage divide factor is chosen to enhance the output swing and improve the phase noise performance. To further enhance the negative resistance, and thus decrease the start-up time, the bulk terminals of the gm-boosting transistors are dynamic-biased by the low-swing nodes provided by the inherent tapped capacitors in Colpitts VCOs. Due to the switching operation mode of the gm-boosting transistors and the absence of common-mode nodes for the switching transistors, the flicker noises up-conversion is largely suppressed. Designed in a 0.18-μm CMOS process, the postlayout simulation results show that it provides a phase noise of -127.66 dBc/Hz at 1 MHz offset centered at 3.76 GHz and a figure-of-merit (FoM) of 192.4 dBc/Hz while dissipating 4.71 mW from a 0.6 V supply. The tuning range is 17% (from 3.28 GHz to 3.89 GHz) and the 1/f3phase noise corner is only 60 kHz.

A wideband low-noise transconductance amplifier (LNTA) with high linearity is proposed for SAW-less applications. Complementary source-follower and common-source stage are adopted to solve the second-order nonlinear feedback problem. Derivative superposition (DS) method is employed to decrease the second- and third-order nonlinearity of the main path. Moreover, large-signal input matching performance is preserved due to the push-pull operation. Designed in a 0.18-μm CMOS process, the simulation results show that it provides a minimum noise figure (NF) of 2.4 dB, and a maximum trans-conductance of 81 mS from 0.17 to 3.17 GHz. An input 1-dB compression/desensitization point of 4.14/1.58 dBm and an IIP3 of 20.8 dBm are obtained, respectively. The input matching performance is maintained even with a 6 dBm blocker, and the blocker NF is 3.1 dB under a 0 dBm blocker. The circuit draws 9.1 mA from a 1.8 V supply and the core area is only 0.068 mm2.

A one-step sneak-path free read scheme for resistive crossbar memory is proposed in this article. During read operation, it configures the crossbar array into a four-terminal resistance network, which is composed of the selected cell and three other resistors corresponding to unselected cells that contribute to the sneak-path. Two sensing voltages with equal potential are applied to three terminals of the network. One is for sensing the resistance of the selected cell; the other is for creating zero-voltage drop across one of the three resistors, which connects the sneak-path to the selected cell. This effectively suppresses the current injected by the sneak-path to the selected cell-sensing loop. This work also proposes a cost-effective data-encoding circuit that guarantees that at least half of the memory cells are in a high-resistance state, which further minimizes sneak-path current. The impact of key design parameters, such as sensing voltage, switch on-resistance, and the ratio of memory cell resistances in different states, as well as nonideal effects are investigated. Equations for estimating the maximum array size to share a single read circuit are derived. The effectiveness of the proposed design has been validated via circuit simulations. Impacts of the word-/bit-line resistance are also analyzed.

Tag collision severely affects the performance of radio-frequency identification (RFID) systems. Most anti-collision algorithms focus on preventing or reducing collisions but waste lots of idle slots. In this letter, we propose a time efficient anti-collision algorithm based on a query tree scheme. Specifically, the dual prefixes matching method is implemented based on the traditional query tree identification model when the reader detects the consecutive collision bits, which can significantly remove idle slots. Moreover, the proposed method can also make extensive use of collision slots to improve the identification efficiency. Both theoretical and simulation results indicate that the proposed algorithm can achieve better performance than existing tree-based algorithms.

Voltage comparators have been widely used in low-power sensor wake-up circuits for extracting digital bits from the envelope of received RF signals. This paper presents an alternative circuit to such comparators. The proposed circuit extracts digital bits by detecting the falling edge of the envelope signal. Since it essentially compares the values of the same signal at different times, it is potentially more robust than the comparator based approach, which compares the peak voltage of the envelope signal with another reference voltage. The design issues for using the proposed edge detection circuit into different wake-up receiver architectures are discussed and simulation results are also presented to demonstrate the performance of the proposed circuit.

With recent rapid advances in wireless communication and networking, the demand for wireless video streaming is exploding. Unlike data streaming, video streaming is much more challenging due to unique characteristics such as bursty flow, stringent delay bound, and selective loss tolerance. Under the dynamic nature of wireless channels, wireless video streaming is virtually impossible to achieve deterministic quality-of-service (QoS) guarantee. Recent development in statistical QoS guarantees has shown great potential for wireless video streaming. However, in the case of statistical QoS guarantee, loss of data due to queue length bound violation or delay violation is often inevitable. Because of unequal importance of video data stream and their inherent dependency, different loss patterns will result in distinctive loss impact. It is critical to design an appropriate scheme to control the loss of video data in such a way that it will minimize the impact of such loss. We develop in this research a prioritized packet dropping scheme based on virtual leaky bucket to control the delivery of video streams. We have carried out analysis based on effective capacity, effective bandwidth, and virtual leaky bucket to demonstrate the potential of the proposed scheme. Preliminary results obtained from simulations show that an improved performance in QoS guarantees can be achieved for wireless video streaming.