Bluetooth Low Energy Communication Research Articles

An ADPLL-Based GFSK Modulator with Two-Point Modulation for IoT Applications.

To establish ubiquitous and energy-efficient wireless sensor networks (WSNs), short-range Internet of Things (IoT) devices require Bluetooth low energy (BLE) technology, which functions at 2.4 GHz. This study presents a novel approach as follows: a fully integrated all-digital phase-locked loop (ADPLL)-based Gaussian frequency shift keying (GFSK) modulator incorporating two-point modulation (TPM). The modulator aims to enhance the efficiency of BLE communication in these networks. The design includes a time-to-digital converter (TDC) with the following three key features to improve linearity and time resolution: fast settling time, low dropout regulators (LDOs) that adapt to process, voltage, and temperature (PVT) variations, and interpolation assisted by an analog-to-digital converter (ADC). It features a digital controlled oscillator (DCO) with two key enhancements as follows: ΔΣ modulator dithering and hierarchical capacitive banks, which expand the frequency tuning range and improve linearity, and an integrated, fast-converging least-mean-square (LMS) algorithm for DCO gain calibration, which ensures compliance with BLE 5.0 stable modulation index (SMI) requirements. Implemented in a 28 nm CMOS process, occupying an active area of 0.33 mm2, the modulator demonstrates a wide frequency tuning range of from 2.21 to 2.58 GHz, in-band phase noise of -102.1 dBc/Hz, and FSK error of 1.42% while consuming 1.6 mW.

From wires to waves, a novel sensor system for in vivo pressure monitoring.

Pressure monitoring in various organs of the body is essential for appropriate diagnostic and therapeutic purposes. In almost all situations, monitoring is performed in a hospital setting. Technological advances not only promise to improve clinical pressure monitoring systems, but also engage toward the development of fully implantable systems in ambulatory patients. Such systems would not only provide longitudinal time monitoring to healthcare personnel, but also to the patient who could adjust their way-of-life in response to the measurements. In the past years, we have developed a new type of piezoresistive pressure sensor system. Different bench tests have demonstrated that it delivers precise and reliable pressure measurements in real-time. The potential of this system was confirmed by a continuous recording in a patient that lasted for almost a day. In the present study, we further characterized the functionality of this sensor system by conducting in vivo implantation experiments in nine female farm pigs. To get a step closer to a fully implantable system, we also adapted two different wireless communication solutions to the sensor system. The communication protocols are based on MICS (Medical Implant Communication System) and BLE (Bluetooth Low Energy) communication. As a proof-of-concept, implantation experiments in nine female pigs demonstrated the functionality of both systems, with a notable technical superiority of the BLE.

Multichannel Neighbor Discovery in Bluetooth Low Energy Networks: Modeling and Performance Analysis

Bluetooth Low Energy (BLE) has become one of the enabling wireless technologies to facilitate the Internet of Things. Neighbor discovery is critical in BLE communications. BLE uses multiple (three) channels in neighbor discovery. It is challenging to achieve low-latency and low-energy-consumption BLE neighbor discovery due to the lack of analytical models for multichannel neighbor discovery. In this paper, we study BLE multichannel neighbor discovery for two advertising modes specified by BLE: periodic deterministic advertising (PDA) and pseudo-random delay advertising (RDA). We build two generic models, BLE 3-Circle model and BLE 1-Circle model, for characterizing BLE multichannel neighbor discovery. For PDA mode, we present a necessary and sufficient condition for BLE multichannel neighbor discovery, and provide a guideline for parameter setting. With the guideline, we derive the expected discovery latency in closed form, and demonstrate that the expected discovery latency is very close to a theoretical lower bound. For RDA mode, we build an analytical model based on Markov chain to accurately compute the expected discovery latency. Simulation and experimental results show accuracy of our analytical works. Interestingly, our parameter setting guideline works well for both PDA and RDA mode.

Design and Development of IoT Enabled Smart Sandal

In this paper, an attempt has been made to develop a smart device that can assist women when they feel unsafe. This smart device will be clipped to the footwear of the user and can be triggered discreetly. On tapping one foot behind the other four times, an alert is sent via Bluetooth Low Energy communication to an application on the victim’s phone, programmed to generate a message seeking help with the location of the device attached. The results obtained were analysed using Naïve Baye classifier. In such situations, the aid of a safety device that will inform the victim’s family members or the authorities (in severe situations) may help women feel safer, confident and reduce the chances of harassment.

S-CAM: An Untethered Insertable Laparoscopic Surgical Camera Robot with Non-Contact Actuation

Fully insertable robotic imaging devices represent a promising future of minimally invasive laparoscopic vision. Emerging research efforts in this field have resulted in several proof-of-concept prototypes. One common drawback of these designs derives from their clumsy tethering wires which not only cause operational interference but also reduce camera mobility. In this paper, a tetherless insertable surgical camera (s-CAM) robot with non-contact transabdominal actuation is presented for single-incision laparoscopic vision. Wireless video transmission and control communication using onboard power help eliminate cumbersome tethering wires. Furthermore, magnetic based camera actuation gets rid of intrinsic physical constraints of mechanical driving mechanisms, thereby improving camera mobility and reducing operational interference. In addition, a custom Bluetooth low energy (BLE) application profile and a real-time operating system (RTOS) based multitask programming framework are also proposed to facilitate embedded software design for insertable medical devices. Initial ex vivo test results of the s-CAM design have demonstrated technical feasibility of a tetherless insertable laparoscopic camera. Effective imaging is confirmed at as low as 500 lx illumination. Wireless laparoscopic vision is accessible within a distance of more than 10 m. Transabdominal BLE communication is stable at over −52 dBm and shows its potential for wireless control of insertable medical devices. RTOS based sfotware event response is bounded within 1 ms while the CPU usage is at 3∼5%. The device is able to work for 50 min with its onboard power. For the mobility, the robot can translate against the interior abdominal wall to reach full abdomen quadrants, tilt between −180 and +180, and pan in the range of 0∼360. The s-CAM has brought robotic laparoscopic imaging one step further toward less invasiveness and more dexterity.

A portable and smartphone-operated photoelectrochemical reader for point-of-care biosensing

In recent years, a number of lab-made potentiostats have been developed as alternatives to the expensive commercial options to facilitate point-of-care (PoC) electrochemical biosensing. However, these devices have no means of interfacing with and controlling optical excitations sources, an essential component in photoelectrochemical (PEC) biosensing. Accordingly, this sensing modality has been relegated to laboratory applications only and can only be conducted using expensive photoelectrochemical workstations. To address this limitation, we have designed and validated a portable reader for PoC PEC biosensing (PECsense). The device can perform chronoamperometry while synchronously controlling an optical excitation source. PECsense is remotely controlled by a smartphone via the Bluetooth Low Energy communication protocol. This photoelectrochemical reader can be used in several different PEC sensing applications, including experiments with variable illumination periods, those that yield cathodic or anodic photocurrents, and those that require applied biases.

An Embedded System for Acoustic Data Processing and AI-Based Real-Time Classification for Road Surface Analysis

The current roadway monitoring is expensive and not systematic. This paper proposes a new system able to evaluate the pavement quality of road infrastructure. The embedded system records and processes the acoustic data of the wheel-road interaction and classifies in real-time roadways’ health thanks to integrated AI solutions. The measurements to produce the dataset to train a convolutional neural network (CNN) were collected using a vehicle operating at different cruise speeds in the area of Pisa. The dataset is composed by acoustic data belonging to several typologies of roads: dirty or grass roads, high roughness surfaces and roads with cracks or potholes. The raw audio signals were split, labelled, and converted into images by calculating the Mel spectrogram. Finally, the authors designed a tiny CNN with a size equal to 18 kB able to classify between four different classes: good quality road, ruined road, silence and unknown. The CNN architecture achieves an accuracy of about 93% on the original model and 90% on the quantized one. Quantization permits to convert the final architecture into a suitable form to be deployed on a low-complex embedded system integrated in the tyre cavity. In addition, a custom board was designed to act as IoT node thanks to a Bluetooth Low Energy communication towards smartphones and/or car infotainment systems. These systems, featured with GPS, guarantee to obtain real-time maps service of road quality. At authors’ knowledge, this is the first real-time and fully integrated solution at the state of the art for road pavement quality analysis and classification on acoustic data.

Reconfigurable Intelligent Surface-Assisted Bluetooth Low Energy Link in Metal Enclosure

Reconfigurable intelligent surface (RIS) technology is at the forefront for its transformative role in future wireless communication systems such as wireless local area networks (WLAN), sixth-generation (6G) communication, and internet-of-things (IoT). This paper presents RIS-assisted Bluetooth low energy (BLE) communication links in neighbor discovery mode. We optimized the packet error rate (PER) performance of the BLE communication link in a highly reflecting metal enclosure environment. We used one RIS for the PER optimization of four BLE physical (PHY) modes. Then, we used two RISs simultaneously in a distributed and centralized manner to further optimize the PER of all BLE PHY modes. We found PER optimization using two RISs is better than the PER optimization using one RIS. Additionally, PER optimization using a centralized arrangement of RISs outperformed PER optimization using distributed arrangement. We found the coded BLE modes i.e., LE500K and LE125K show lower PER than the uncoded counterpart i.e., LE1M and LE2M. This is because uncoded BLE PHY modes have higher data rates than the coded BLE PHY modes. Because of additional channel power gains introduced by RIS-based passive beamforming, the PER of coded and uncoded BLE PHY modes is further reduced.

Optimization of the AODV-Based Packet Forwarding Mechanism for BLE Mesh Networks

The standard Bluetooth Low-Energy mesh networks assume the use of flooding for multihop communications. The flooding approach causes network overheads and delays due to continuous message broadcasting in the absence of a routing mechanism. Among the routing protocols, AODV is one of the most popular and robust routing protocol for wireless ad hoc networks. In this paper, we optimized the AODV protocol for Bluetooth Low-Energy communication to make it more efficient in comparison to the mesh protocol. With the proposed protocol (Optimized AODV (O-AODV)), we were able to achieve lower overheads, end-to-end delay, and average per-hop one-way delay in comparison to the BLE mesh (flooding) protocol and AODV protocol for all three scenarios (linear topology with ten nodes, multipath topology with six and ten nodes). In addition, the proposed protocol exhibited practically constant route requests and route reply setup times. Furthermore, the proposed protocol demonstrated a better Packet Delivery Ratio (PDR) for O-AODV (84%) in comparison to AODV (71%), but lower than the PDR of the mesh (flooding) protocol with 93%.

Rescue notification system with accurate location estimation for injuries in city Marathons

ABSTRACT This study proposes a simple location-based rescue request system for use in city marathons with large numbers of athletes. Instead of using passive radio frequency identification technology, the proposed system employs initiative Bluetooth low-energy communication technology. When an athlete is injured, they can immediately transmit a rescue request that contains their estimated location and the time of the injury. Upon receiving the rescue request, medical staff can respond rapidly. This study included three parts. First, the time required for a rescue team to receive a request from an injured athlete was estimated based on past international city marathon race records. Then, a software simulation was performed to extract the simplest transfer parameter requirements for system positioning. Finally, experimental samples were produced for field verification, and the rescue notification timing system was developed. This approach was found to successfully deliver 97.4%–99.9% of the athletes’ request messages within 3–4 min and maintains the error range of the rescue locations under 15 m. It is appropriate for use in city marathons owing to its simple structure, low weight, low cost, and need for only common commercial technologies that are ready for mass production.

Efficient Communication Scheme for Bluetooth Low Energy in Large Scale Applications.

The use of Bluetooth Low Energy (BLE) in the Internet-of-Things (IoT) applications has become widespread and popular. This has resulted in the increased number of deployed BLE devices. To ensure energy efficiency, applications use connectionless communication where nodes broadcast information using advertisement messages. As the BLE devices compete for access to spectrum, collisions are inevitable and methods that improve device coexistence are required. This paper proposes a connectionless communication scheme for BLE that improves communication efficiency in IoT applications where a large number of BLE nodes operate in the same area and communicate simultaneously to a central server. The proposed scheme is based on an active scanning mode and is compared with a typical application where passive scanning mode is used. The evaluation is based on numerical simulations and real-life evaluation of a network containing 150 devices. The presented scheme significantly reduces the number of messages transmitted by each node and decreases packet loss ratio. It also improves the energy efficiency and preserves the battery of BLE nodes as they transmit fewer radio messages and effectively spent less time actively communicating. The proposed connectionless BLE communication scheme can be applied to a large variety of IoT applications improving their performance and coexistence with other devices operating in the 2.4 GHz band. Additionally, the implementation complexity and costs of the proposed communication scheme are negligible.

A Secure Authentication Protocol against the Co-located App Attack in BLE

Bluetooth Low Energy (BLE) is used for periodic transmission of smaller data packages called attributes. BLE remains in sleep mode at all times except when participating in a data exchange, which reduces overall energy consumption. For secure communication, BLE devices need to pair first. The pairing has two or three phases. We say two or three phases because the third phase is optional and happens only if the devices are going to bond. The second pairing phase is made using a secure pairing scheme, but the third phase remains vulnerable to an attack named the co-located application (app) attack: a malicious app gets the same level of access to the paired protected data as the legitimate app. We provide an authentication protocol to mitigate this attack. Furthermore, we analyze the security of BLE communications after bonding, with or without our proposed protocol. Moreover, we also analyze the efficiency of the proposed protocol, and conclude that our proposed scheme makes BLE communications secure against the co-located app attack and is efficient enough to be practical.

Can Be Applied for Bluetooth Low Energy to i-construction? : Characterization of BLE on Excavator

The Government of Japan has declared that construction sites must implement i-construction, in which information communication technology (ICT) is used to improve construction site productivity and throughput. Examples of i-construction include remote and automatic control systems for construction machinery, for which wireless communication is generally required; however, the wireless characteristics that must be considered in i-construction remain unclear. To clarify these characteristics, Bluetooth Low Energy (BLE) beacon module is implemented for construction machines, and we investigate its communication characteristics. We focussed on two evaluations: characterisation of the BLE unit module and its feasibility in i-construction. Experimental results were used to characterise BLE communication in a residential area and construction site. In the latter, BLE beacon module communication was possible between a sender located in an excavator attachment and a receiver in its cabin.

Earth-Abundant Fe–Al–Si Thermoelectric (FAST) Materials: from Fundamental Materials Research to Module Development

To develop an autonomous power generation technology to support an internet-of-things (IoT) society, we proposed low-cost and nontoxic Fe-Al-Si-based thermoelectric (FAST) materials consisting of an Fe3Al2Si3 phase. Because of the cost-effectiveness and easy disposal of FAST materials, they are attractive for autonomous power supplies to drive IoT sensors and devices. While bismuth-tellurium-based thermoelectric power generation modules have been commercialized, the discovery of FAST materials opens an additional route to generate power from waste heat at room temperature under a small temperature difference, which will expand the diversity of applications of thermoelectric power generation modules. This paper reports the thermoelectric properties of FAST materials synthesized by conventional laboratory-scale synthesis and mass production processes, enhancement of power factor less than 600 K through homogenization and removal of metallic precipitations, development of thermoelectric power generation modules, and the results of power generation tests. The operation of temperature/humidity sensors and wireless transmission by Bluetooth low energy communication using FAST materials-based modules under a small temperature difference at room temperature was demonstrated.

A 15-W Triple-Mode Wireless Power Transmitting Unit With High System Efficiency Using Integrated Power Amplifier and DC–DC Converter

In this article, we present an integrated triple-mode wireless power transmitter unit (TWPTU) circuit supporting all three alliance for wireless power (A4WP), wireless power consortium (WPC), and power matters alliance (PMA) standards, simultaneously, for high-efficiency battery charging application. The triple-mode power amplifier (PA) utilizes the adaptive gate splitting technique and free-wheeling control to achieve high efficiency in triple modes. The programmable supply voltage from two high-efficiency dc–dc converters supplies the PA. The output power of the PA is measured by the proposed high accuracy current sensor and controlled through different communication protocols depending on their operating standards. The WPC/PMA modes are based on the amplitude-shifting-key and frequency-shifting-key modulations for the communication between the transmitter and the receiver, while in the A4WP mode, to control the output power of the PA, the bluetooth-low-energy (BLE) unit adjusts the supply voltage through the provided step-up dc–dc converter. A step-down dc–dc converter with pulse-skipping modulation reduces the power consumption of the TWPTU during charge waiting time. The demodulator for in-band communication of WPC/PMA and interintegrated circuit for BLE communication of A4WP is fully implemented. This chip is fabricated using a 180-nm bipolar-CMOS-DMOS (BCD) process with laterally diffused <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> options and has a die size of 5 × 3.5 mm. The proposed architecture achieves the output power level of 25.8 W. The measurement results show the maximum system efficiencies of the TWPTU in WPC/PMA and A4WP modes are 88.5% and 84.3%, respectively.

Wearable EBG-Backed Belt Antenna for Smart On-Body Applications

This article presents an innovative belt antenna with an electromagnetic band-gap (EBG) ground plane made of textile materials. The antenna can be applied in a smart belt system to set up a communication link with other electronic devices and/or host a variety of sensors to track human motions. The proposed belt antenna works at 2.45 GHz in the industrial, scientific, and medical radio band for Bluetooth low energy communications. Considering the effect the human body would have on the performance of a belt antenna, a textile ground plane is designed to be integrated into the trouser fabric behind the belt to provide isolation from the body and simultaneously improve antenna radiation characteristics. Through the application of the ground plane, the belt antenna achieves a maximum realized gain of 7.94 dBi and a minimum specific absorption rate of 0.04 W/kg at 0.5 W input power. During the design process, characteristic mode analysis is used to explore the underlining principle and further optimize the antenna performance. Two typical EBG structures are analyzed in detail for this application scenario. The suspended transmission line method is used to evaluate EBG performance variations when the textile ground plane is bent. A prototype of such a system is fabricated and tested. Experimental results shows that the belt antenna, together with the textile EBG ground plane, is an excellent candidate for a smart belt system with desirable radiation pattern, efficiency, and safety limit.

Building an Energy-Efficient Ad-Hoc Network for Wildlife Observation

This study evaluated the design of an energy-efficient ad-hoc network used for wildlife observations, particularly in order to understand the social relationships in an animal group, where the distance between individuals, i.e., proximity, can be used to measure a relationship. Our proposed network consists of a full mesh topology and contains nodes that communicate via Bluetooth Low Energy (BLE) in advertisement mode. The initial hardware configuration and software algorithm duty cycles the BLE communication to on and off states using a parameter called the BLE active triggering interval. The algorithm is improved by placing the BLE subsystem and CPU in deep sleep when there are no BLE or CPU tasks to process. This improves the power performance by up to 94.48%. To scale up power optimization and track the trade-off between power and throughput, we created a simulator that modeled our network with dynamic wireless sensor nodes. The simulator verified the base case hardware results. It also showed a median power performance increase of 97.79% in comparison to the base case, yet throughput decreased by 66.65%. The highest power performance increased by 98.89% when a wireless sensor node was configured with a BLE active triggering interval of 50 s and its CPU was set to 14 MHz; however, the simulator showed a throughput drop of 79.97%. Depending on the application, a design may tolerate the decline in throughput to achieve higher power performance.

Improving the Timeliness of Bluetooth Low Energy in Dynamic RF Environments

The ability to communicate within given delay bounds in noisy RF environments is crucial for Bluetooth Low Energy (BLE) applications used in safety-critical application domains, such as health care and smart cities. In this work, we experimentally study the latency of BLE communications in the presence of radio interference and show that applications may incur long and unpredictable transmission delays. To mitigate this problem, we devise a model capturing the timeliness of connection-based BLE communications in noisy RF channels by expressing the impact of radio interference in terms of the number of connection events necessary to complete a successful data transmission ( n CE ). We show that this quantity can be estimated using the timing information of commands sent over the host controller interface of common BLE devices, hence without additional communication overhead or energy expenditure. We further show that a BLE device can make use of our BLE timeliness model and recent n CE measurements to adapt its BLE communication parameters at runtime, thereby improving its performance in the presence of dynamic radio interference. We implement such an adaptive scheme on the popular nRF52840 platform and perform an extensive experimental study in multiple indoor environments using three different BLE platforms. Our results show that a BLE application can, indeed, make use of the proposed model and recent n CE measurements to adapt its connection interval at runtime to increase the timeliness of its communications, reducing the number of delayed packets in noisy RF environments by up to a factor of 40.

City Marathon Active Timing System Using Bluetooth Low Energy Technology

This study proposes and implements city marathon timing technology using Bluetooth Low-Energy (BLE) communication technology. This study also performs a prevalidation of the athletes’ physiological sensory data that is sent out by the same timing system—the BLE active communication technology. In order to verify the timing and positioning technology, 621 K records of static measurement of the Received Signal Strength Indicator (RSSI) were first collected. The trend of the RSSI between the location and the BLE Receiver when the runners carried a BLE Tag was analyzed. Then, the difference between the runners’ passing timestamp and the runners’ actual passing time when the runners carried a BLE Tag and ran past the BLE Receivers was dynamically recorded and analyzed. Additionally, the timing sensing rate when multiple runners ran past the BLE Receivers was verified. In order to confirm the accuracy of the time synchronization in the remote timing device, the timing error, synced by the Network Time Protocol (NTP), was analyzed. A global positioning system (GPS) signal was used to enhance the time synchronization’s accuracy. Additionally, the timing devices were separated by 15 km, and it was verified that they remained within the timing error range of 1 ms. The BLE communication technology has at least one more battery requirement than traditional passive radio frequency identification (RFID) timing devices. Therefore, the experiment also verified that the BLE Tag of this system can continue to operate for at least 48 h under normal conditions. Based on the above experimental results, it is estimated that the system can provide a timing error of under ±156 ms for each athlete. The system can also meet the scale of the biggest international city marathon event.

(Invited) Soft Electronics and Machines with Tough Hydrogels

Introducing methods for instant strong bonding between hydrogels and antagonistic materials – from soft to hard – allows us to demonstrate elastic, yet tough biomimetic devices and machines with a high level of complexity [1]. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone and metals reaching unprecedented interfacial toughness exceeding 2000 J/m2. Our approach is applicable in rapid prototyping and in delicate environments inaccessible for extended curing and cross-linking. The combination of ionic hydrogels with antagonistic materials such as elastomers, polymers and metals allows to create soft electronics and hybrid machines. We demonstrate stretchable batteries for self-powered soft devices, adaptive lenses, and autonomous electronic skin for triggered drug delivery (Figure 1). We further introduce a new family of biodegradable hydrogels that are able to self-heal and are resistant to dehydration. Soft machines and robots – built from hydrogels with tuned mechanical properties – are designed to be operated in ambient conditions and degrade after use. Besides progressing standalone soft machines, our advances in the synthesis of biodegradable hydrogels bring bionic soft robots a step closer to nature. [1] D. Wirthl, R. Pichler, M. Drack, G. Kettlgruber, R. Moser, R. Gerstmayr, F. Hartmann, E. Bradt, R. Kaltseis, C. M. Siket, S. E. Schausberger, S. Hild, S. Bauer, M. Kaltenbrunner, „Instant tough bonding of hydrogels for soft machines and electronics”, Science Advances, 3(6), e1700053 (2017). Caption Figure 1: Hydrogel electronic skin. (left) Concept of a hydrogel smart skin, with a flexible unit bearing power supply, control, readout and communication units, and a stretchable transducer batch. (right) Photograph of an untethered electronic hydrogel with four stretchable heating elements and adjoined temperature sensors strongly bonded to a PVA hydrogel. Battery, control, readout and Bluetooth Low Energy communication electronics are hosted on a flexible circuit board. Figure 1