Wireless Design Research Articles

Design, development, and performance evaluation of a low-cost, low-power wake-up radio system for wireless sensor networks

Energy-efficient operation is a challenge for wireless sensor networks (WSNs). A common method employed for this purpose is duty-cycled operation, which extends battery lifetime yet incurs several types of energy wastes and challenges. A promising alternative to duty-cycled operation is the use of wake-up radio (WuR), where the main microcontroller unit (MCU) and transceiver, that is, the two most energy-consuming elements, are kept in energy-saving mode until a special signal from another node is received by an attached, secondary, ultra-low power receiver. Next, this so-called wake-up receiver generates an interrupt to activate the receiver node's MCU and, consequently, the main radio. This article presents a complete wake-up radio design that targets simplicity in design for the monetary cost and flexibility concerns, along with a good operation range and very low power consumption. Both the transmitter (WuTx) and the receiver (WuRx) designs are presented with the accompanying physical experiments for several design alternatives. Detailed analysis of the end system is provided in terms of both operational distance (more than 10 m) and current consumption (less than 1 μA). As a reference, a commercial WuR system is analyzed and compared to the presented system by expressing the trade-offs and advantages of both systems.

ArgMax and ArgMin: transitional probabilistic models in cognitive radio mesh networks

AbstractThe erratic nature of spectrum availability and diversity imposes the use of a probabilistic framework for channel selection in cognitive radio networks protocol design. In this work, two probability distributions called ArgMax and ArgMin are proposed, which have broad applications in channel selection mechanisms, routing, and media access control protocols. The ArgMax probability distribution locates the maximum random variable among a set of random variables, while the ArgMin locates the minimum random variable. We show that the ArgMax probability distribution is a better candidate than the frequently used odds‐on‐mean probability distribution through theoretical analysis and simulation. The ArgMin probability distribution has a variety of applications and is shown to be useful in achieving a lower bound on the network's minimum spectral capacity. In simulation, we develop a probabilistic selection routing procedure (PSRP) that adopts the ArgMax probability distribution to guide packets throughout the network. The stochastic framework of probabilistic selection routing procedure is also an appropriate skeleton for building stochastic‐based routing protocols for dynamic networks such as cognitive radio networks. The simulation results suggest that ArgMax enables the routing scheme to adapt to the network dynamic more quickly and to more accurately locate the best candidate to route to than the odds‐on‐mean probability distribution. The ArgMax enhances the network throughput and end‐to‐end delay by over 30% when network load increases. Copyright © 2013 John Wiley & Sons, Ltd.

Full duplex radios

This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.

Double helix dipole design applied to magnetic resonance: A novel NMR coil

A new radio frequency coil design for NMR experiments is presented. The coil generates a magnetic field purely perpendicular to the longitudinal axis of the main magnet, and its sensitivity is higher than the traditional transversal resonators. This is achieved by adding the contribution of two tilted solenoid coils fed with opposite currents. The work presents the mathematical model for the new coil, numerical simulations performed to validate that model and a comparison with an equivalent saddle coil. The new design is tested experimentally in low- and high-field NMR experiments and compared with results obtained with equivalent saddle coils. The results lead to conclude that the new design provides better sensitivity than the transverse resonators commonly used in NMR.

Downlink/uplink identification of time-division duplexing-OFDMA systems for cognitive radios

When coexisting with dual-link primary systems, secondary systems in cognitive radios should first distinguish between the primary downlinks and uplinks in order to efficiently explore their respective spectrum opportunities. Because of the assumptive prior knowledge about the time-frequency locations of primary downlinks and uplinks, this procedure is usually not considered in the design of cognitive radios. In this paper, a cooperative method is proposed for the downlink/uplink identification of time-division duplex-based orthogonal frequency-division multiple access systems. In this method, the power level of the primary link is extracted as the key feature, which also contributes to the subsequent cognitive behaviours. The effects of the primary and secondary systems and the effects of the detection parameters on the identification accuracy are all analysed in detail. The simulation results show that the proposed method can identify the primary links precisely and quickly with low complexity.

Design of compact circularly polarized radio frequency identification tag antenna for metallic object application

AbstractA passive UHF band radio frequency identification tag antenna design is presented in this article. To allow compact size and circular polarization (CP) radiation, a radiating square patch is loaded with two pairs of unequal slits, while a quarter‐wave microstrip line connected to a tag chip and terminated by a short‐circuited stub line is used to excite the radiating patch. The 10‐dB impedance bandwidth of the tag antenna is measured to be 31 MHz (896–927 MHz), whereas its 3‐dB CP bandwidth is 6 MHz (911–917 MHz). Further experiment has demonstrated that the proposed tag antenna can provide better reading distance when mounted on a metallic surface as compared with the free‐space condition. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1481–1485, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27607

Design of an intelligent car radio and music player system

With the rapid development of the Internet and digital technology, digital music and Internet radio stations have come to attract increasing investment from various sources. Through the Internet, users are able to listen to music and radio stations without geographical limitations. The Internet also provides users more options in their music and radio station choices. The technological developments in this field allow for improvements in car audio systems. However, across all relevant studies, the question of how best to recommend radio or music choices to users remains an important topic in the research relating to digital music and radio. Therefore, in this paper, we try to improve these recommendations by recording user behavior and analyzing the music preferences of users with similar background information. This is different to traditional recommendation mechanisms as we simplify the feedback procedure for users. In addition, by adjusting the weightings in the formula for calculating the recommendations, we are able to provide personalized recommendations. This would better satisfy the needs of different types of users. Through experimental results, we prove that our recommendation mechanism significantly helps users to select radio stations and music.

A Framework for Distributed Resource Allocation and Admission Control in a Cognitive Digital Home

The advances in radio design and wireless networking, along with the growth of multimedia home entertainment technologies, is creating the concept of a cognitive digital home requiring spectrum coexistence of various devices and networks of networks. A framework for resource allocation in a Cognitive Digital Home (CDH) with a multiplicity of radio access technologies (RAT) such as cognitive radios and legacy radio devices supporting heterogeneous applications is developed. We consider two channel access models in the CDH for addressing spectrum coexistence of legacy devices: (i) Pessimistic Controllability (PC) Model where the Home Genie node (HG) has no influence over legacy devices, and (ii) Switched RAT (SR) Model where the HG has perfect control of legacy devices. Distributed algorithms for maximizing sum rate and maximizing service capacity are designed using partial dual decomposition techniques. A distributed power control scheme is also designed for efficient use of energy. An admission control scheme based on pricing information obtained from the distributed algorithms is used to improve system feasibility.

Laboratory Trials and Evaluations of In-Band Digital Radio Technologies: HD Radio and DRM+

Many countries are converting their analog communication and broadcasting services into digital services. However, digital radio broadcasting service is still an issue to be addressed. In order to provide digital radio broadcasting service, it is very important to choose the most appropriate digital radio method for their frequency environment and listeners. This paper depicts laboratory test results of in-band digital radio technologies, HD Radio and DRM+. To contribute to decision of digital radio standard and design of digital radio transmission network, various results of many test items are expressed.

The plasmonic J-pole antenna

The plasmonic J-pole antenna is the nanoscale version of a radio frequency design, consisting of a half wavelength arm connected to a quarter wavelength feed pair. Here, we report on an optical J-pole antenna that displays both a dipole (1015 nm) and quadrupole resonance (653 nm). The excitation of the quadrupole resonance is optimum at an angle of incidence directly related to the geometry of the antenna, demonstrating the flexibility of the design. The J-pole antenna shows great promise for enhancing and shaping the angular emission pattern of quantum emitters.

Detecting and Preventing Wormhole Attacks In Wireless Sensor Networks

Due to the rapid development of wireless sensor devices in terms of low power and inexpensive data-relaying has been partially achieved because of the rapid progress in integrated circuits and radio transceiver designs and device technology. Because of this, the wireless sensor devices are able to gather information, process them if required and send them to the next sensor device. The resource constrained ad hoc wireless sensor network is versatile yet vulnerable to attacks. The communication infrastructure with less sensor networks may interact with the sensitive data in the hostile environment where the nodes may fail and new nodes may join the network, which may leads to the susceptibility to many kinds of security attacks. An adversary can eavesdrop on all the messages within the emission area, by operating in promiscuous mode. So, it is imperative that the protection of the network routing from the adversaries for the wireless ad hoc sensor network must be adopted for critical missions. A particularly devastating attack, predominant in today's world is the wormhole attack. In this paper, the wormhole attack made by the malicious attacker in sensor networks has been implemented and also the number of Guard nodes required has been decided and implemented. Functions of the guard nodes like local inter-node collaborative data fusion and decision fusion to detect, isolate and prevent any further attacks is to be implemented. Simulations have been performed under different scenarios and from the results of simulation we have observed that our scheme is capable of improving the

A Switched-Line Phase Shifter Fabricated with Additive Manufacturing

Additive manufacturing, also known as 3D printing, has proven to be advantageous compared to conventional planar methods when utilizing the volume of a structure to miniaturize the design. The use of additive manufacturing can allow for high frequency circuitry to be conformed to an arbitrary shape while maintaining or enhancing performance. Recent advancements in low loss materials applicable to additive manufacturing have pushed performance levels even further. Utilizing additive manufacturing to build a three dimensional structure can improve factors such as reliability and repeatability by making the structure one solid piece as opposed to assembling multiple planar objects into the 3D shape. This allows the circuitry to be built around the structure. With this design approach other considerations, such as stability and strength, can be concentrated on during the structure design to realize new shapes. The purpose of this work is to investigate a 3D printed material, ULTEM, for radio frequency use and design a switched line phase shifter using the derived material properties. The first step in any high frequency circuit design is to have accurate material properties. An efficient way to determine the permittivity and loss tangent of a material is to place a ring resonator on the substrate and measure the resonant frequency and Q factor. An equivalent circuit model can then be built to match the measured response and the material properties extracted through circuit theory. From here accurate transmission line models can be analyzed to optimize the performance of the RF circuit. In this paper a ring resonator was designed on ULTEM to characterize the material properties. A 90° phase shifter was then fabricated on a 3D printed ULTEM substrate and a benchmark model was fabricated using traditional planar methods on Rogers RO4003C substrate. A comparison between the two models is given in this paper.

RADIO INTERFACE DESIGN FOR INKJET-PRINTED BIOSENSOR APPLICATIONS

Biomedical wireless sensors require thin, lightweight, and ∞exible single-layer structures operating in immediate proximity of human body. This poses a challenge for RF and antenna design required for wireless operation. In this work, the radio interface design for a 2.4GHz wireless sensor including a discrete fllter balun circuit and an antenna operating at 0.3mm distance from the body is presented. Thin, lightweight single-layer structure is realized using printed electronics manufacturing technology. The RF and antenna designs are validated by measurements, and a sensor with a fully functional radio interface is implemented and verifled. At 0.3mm from the body, 2.4dB insertion loss and i10dBi realized gain at 2.4GHz were achieved for a discrete fllter balun and antenna, respectively. The received power level on a Bluetooth low energy (BLE) channel was above i80dBm at 1m distance from the body, indicating capability for short-range ofi-body communications. The paper also provides guidelines for printed electronics RF and antenna design for on-body operation.

Field-programmable gate array-based software-defined radio for millimetre-wave single-carrier transmission

Recently, variants of wireless local and personal area networks (WLANs/WPANs) have emerged with different communication protocols that require extremely high-performance signal processing techniques. Taking advantage of the recent advances in the programmable and reconfigurable devices, the implementation of reliable, high data-rate software-defined radios that support multiple protocols has become possible. This study introduces the design and hardware implementation details of a software-defined radio using a field-programmable gate array platform. The implemented software radio consists of a baseband single-carrier transceiver that is compliant with the IEEE 802.15.3c standard for the millimetre-wave wireless personal area network (WPAN), results of bit-error-rate against signal-to-noise ratio are presented and line-of-sight transmission has been demonstrated over millimetre-wave indoor channel.

Second order statistics of selection combining receiver over κ‐μfading channels subject to co‐channel interferences

Radio propagation performances in interference‐limited faded environment are studied in this paper. Selection combining (SC) based on signal‐to‐interference ratio (SIR) overκ‐μfading channels is performed. Probability density function (PDF) and cumulative distribution function (CDF) of the received SIR are determined. Based on the results obtained for PDF and CDF, infinite‐series expressions are derived for the output level crossing rate (LCR) and average fade duration (AFD). These second order statistical measures are regarded as necessary for supporting technical documentation in every radio communication link design. Influences of various system parameters such as fading severity and the number of co‐channel interferences affecting these measures are graphically presented and discussed.

Resource Allocation for Interweave and Underlay CRs Under Probability-of-Interference Constraints

Efficient design of cognitive radios (CRs) calls for secondary users implementing adaptive resource allocation schemes that exploit knowledge of the channel state information (CSI), while at the same time limiting interference to the primary system. This paper introduces stochastic resource allocation algorithms for both interweave (also known as overlay) and underlay cognitive radio paradigms. The algorithms are designed to maximize the weighted sum-rate of orthogonally transmitting secondary users under average-power and probabilistic interference constraints. The latter are formulated either as short- or as long-term constraints, and guarantee that the probability of secondary transmissions interfering with primary receivers stays below a certain pre-specified level. When the resultant optimization problem is non-convex, it exhibits zero-duality gap and thus, due to a favorable structure in the dual domain, it can be solved efficiently. The optimal schemes leverage CSI of the primary and secondary networks, as well as the Lagrange multipliers associated with the constraints. Analysis and simulated tests confirm the merits of the novel algorithms in: i) accommodating time-varying settings through stochastic approximation iterations; and ii) coping with imperfect CSI.

Multidimensional Rain Attenuation Stochastic Dynamic Modeling: Application to Earth–Space Diversity Systems

A stochastic dynamic model for the induced rain attenuation on multiple radio links is presented in this paper. The model is considered as a generalization of the well-known and well-accepted Maseng–Bakken model in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$n$</tex></formula> -dimensions. It incorporates the spatial and time behavior of the rain attenuation phenomena and provides an analytical expression for the transition probability distribution. It consists of a system of stochastic differential equations (SDEs), which, except for the solid mathematical formulation of the correlated rain attenuation stochastic processes, constitutes the general framework for the calculation of other statistical quantities useful for the radio system designers. The long-term statistics and the dynamic properties of rain attenuation are used for the parameterization of the model, without the constraint of any built-in assumptions of the rain field. Finally, the proposed model is used for the generation of correlated rain attenuation time series on multiple satellite communication slant paths and especially to diversity schemes, including site and orbital (angle) diversity. The derived results from the model are tested with respect to experimental long-term statistics for various geometries with very encouraging results. The limitations and the ranges of applicability of the model for Earth–space diversity systems are reported, and the sensitivity of the model on the crucial parameters is discussed.

Design and Implementation of Real-Time Software Radio for Anti-Interference GPS/WAAS Sensors

Adaptive antenna array processing is widely known to provide significant anti-interference capabilities within a Global Navigation Satellite Systems (GNSS) receiver. A main challenge in the quest for such receiver architecture has always been the computational/processing requirements. Even more demanding would be to try and incorporate the flexibility of the Software-Defined Radio (SDR) design philosophy in such an implementation. This paper documents a feasible approach to a real-time SDR implementation of a beam-steered GNSS receiver and validates its performance. This research implements a real-time software receiver on a widely-available x86-based multi-core microprocessor to process four-element antenna array data streams sampled with 16-bit resolution. The software receiver is capable of 12 channels all-in-view Controlled Reception Pattern Antenna (CRPA) array processing capable of rejecting multiple interferers. Single Instruction Multiple Data (SIMD) instructions assembly coding and multithreaded programming, the key to such an implementation to reduce computational complexity, are fully documented within the paper. In conventional antenna array systems, receivers use the geometry of antennas and cable lengths known in advance. The documented CRPA implementation is architected to operate without extensive set-up and pre-calibration and leverages Space-Time Adaptive Processing (STAP) to provide adaptation in both the frequency and space domains. The validation component of the paper demonstrates that the developed software receiver operates in real time with live Global Positioning System (GPS) and Wide Area Augmentation System (WAAS) L1 C/A code signal. Further, interference rejection capabilities of the implementation are also demonstrated using multiple synthetic interferers which are added to the live data stream.

An energy-efficient polar transmitter for IEEE 802.15.6 body area networks: system requirements and circuit designs

This article discusses the radio system requirements and design trade-offs of a low-power 2.3/2.4 GHz IEEE 802.15.6-narrowband transmitter for body area network applications. The IEEE 802.15.6 narrowband PHY adopts nonconstant envelope DPSK modulations. Transmitter architecture selection is a major challenge because it needs to provide both amplitude and phase modulation, with good efficiency and strict requirements on modulation accuracy and linearity for non-constant envelope modulations. A PLL-based polar transmitter with a Sigma-Delta digitally controlled power amplifier (ΣΔ-DPA) is employed for its excellent energy efficiency. Finally, this article discusses the circuit design considerations and implementation results. With balance between analog and digital implementation, and careful planning of the radio system, the polar transmitter presented in this article can meet all of the specifications defined in IEEE 802.15.6 with abundant margin, while having extremely low power consumption of 5.4 mW and excellent energy efficiency of 5.4 nJ/bit.

Picasso

This paper presents the design, implementation and evaluation of Picasso, a novel radio design that allows simultaneous transmission and reception on separate and arbitrary spectrum fragments using a single RF frontend and antenna. Picasso leverages this capability to flexibly partition fragmented spectrum into multiple slices that share the RF frontend and antenna, yet operate concurrent and independent PHY/MAC protocols. We show how this capability provides a general and clean abstraction to exploit fragmented spectrum in WiFi networks, handle coexistence in dense deployments as well as many other applications. We prototype Picasso, and demonstrate experimentally that a Picasso radio partitioned into four slices, each concurrently operating four standard WiFi OFDM PHY and CSMA MAC stacks, can achieve the same sum throughput as four physically separate radios individually configured to operate on the spectrum fragments. We also demonstrate experimentally how Picasso's slicing abstraction provides a clean mechanism to enable multiple diverse networks to coexist and achieve higher throughput, better video quality and latency than the best known state of the art approaches.