Magnetic Communication Systems Research Articles

Performance analysis and design of quasi-cyclic LDPC codes for underwater magnetic induction communications

Magnetic induction (MI) communication is an effective scheme for underwater wireless communication. In this paper, we aim to design an underwater MI communication system based on Quasi-cyclic LDPC (QC-LDPC) codes. Firstly, for a given QC-LDPC code used in underwater MI communication, we propose a novel algorithm to evaluate its performance, which is named as underwater magnetic induction protograph (UWMIP) extrinsic information transfer algorithm. Furthermore, we present a differential evolution UWMIP (DE-UWMIP) algorithm, which incorporates the differential evolution method and the UWMIP algorithm. By this algorithm, we search the optimized QC-LDPC codes with best distance threshold. Simulation results show that the proposed algorithm is effective and provide a good guidance to design the underwater MI communication system.

Surface Electromagnetic Wave-Based Wireless Communication System for Mines

The paper discusses the advantages and shortcomings of resonance and single-frequency single-wire induction communication systems for mines. The issues of creating a magnetic induction communication system based on the twin transmission line (the MIKON-Tel queuing system) and the prospects for using small antennas to arrange two-way communication channels through the rock have been considered. The possibility of creating a multichannel queuing system for subscribers, which operates in a wide frequency band using a twin induction transmission line and small ferrite resonator antennas, is shown. The antenna designs used for magnetic induction communication in mines have been considered. High level of radio frequency signals has experimentally been proven when using a twin line and small antennas. The specific signal attenuation along the route in the coal mine was 4 dB/km. The results obtained prove the fundamental possibility of designing multichannel induction communication systems with a guaranteed communication range of over 4 km from the base station.

자기 유도 통신 시스템 구현

자기장은 전파 시 거의 도전률에 의해서만 영향을 받기 때문에 자기 유도 통신은 음파, 광파, 전자파 등이 잘 전달되지 않는 복잡한 통신 환경에서 우수한 성능을 가진다. 하지만 자기 유도 통신 시스템에 대한 대부분의 연구결과가 이론 위주로 제시된 바 실제 자기 유도 통신 시스템의 구현이 중요한 이슈가 되고 있다. 본 논문에서는 범용 소프트웨어 정의 라디오 모듈과 GNU Radio를 사용하여 BPSK 방식의 자기 유도 통신 시스템 테스트베드를 구축하는 모델을 소개한다. 그 후 이론적인 수신 전력과 실제 실험의 수신 전력 값을 비교하고, 공중 환경에서 실제 구현된 시스템의 패킷오율 측정 결과를 제시한다.

Underwater Communication Employing High-Sensitive Magnetic Field Detectors

Magnetic communication is receiving significant interest in RF-challenging environments. Particularly in underwater environments and underground wireless sensor networks, magnetic communication is an emerging research area. In this paper, a new approach for magnetic underwater communication is presented and evaluated. In this approach, the receiver coil of a conventional magnetic induction communication system is replaced by a high-sensitive low-noise wideband magnetic field sensor. This concept enables a good detection sensitivity and, under certain conditions, an extended communication range. Most magnetic field sensors are small compared to equivalent search coils and offer a high bandwidth. Hence, they can be assembled in order to provide multiple-input multiple-output processing. Based on suitable channel modeling, trade-offs between system parameters are analyzed and the channel capacity is derived. Analytical results are supported by a prototype implementation. Potential application scenarios are studied, where emphasis is on mobile applications.

Construction of Quasi-Cyclic Low Density Parity Check Codes for Magnetic Induction Communication

The magnetic induction (MI) communication has been proved to be an effective method in the wireless underground sensor networks (WUSN). MI communication system based on quasi-cyclic low density parity check (QC-LDPC) codes is expected to improve the transmission performance in WUSN for its good performance and hardware friendliness. In this paper, we aim to construct an optimized QC-LDPC code with low encoding complexity for MI communication system. Firstly, we present a novel method, magnetic induction - protograph extrinsic information transfer (MI-PEXIT) algorithm, which can evaluate the performance of the QC-LDPC codes and predict the distance threshold for successfully transmission of the direct MI communication. Then, we combine the discrete particle swarm optimization (PSO) algorithm with the MI-PEXIT algorithm, and propose a novel scheme DPMIP method to optimize the QC-LDPC codes for MI communication system. Furthermore, two groups of QC-LDPC codes with low encoding complexity are constructed by the proposed DPMIP algorithm, which have different code parameters and different coil parameters. Simulation results validate the superiority of the proposed QC-LDPC codes for MI communication in WUSN, and the proposed codes also can achieve a good trade-off between the complexity and the performance.

Theoretical Modeling and Analysis of Magnetic Induction Communication in Wireless Body Area Networks (WBANs)

The wireless body area network (WBAN) is a promising new communication technology operating at close proximity to the human body. Although various wireless communication techniques using electromagnetic wave propagation have been deployed for WBANs, they encounter several problems. A major issue is that electromagnetic waves in the microwave range often experience a high level of attenuation. Multipath effects and interference with other existing systems are other issues. Magnetic induction (MI) is an alternative physical layer technique, which can address some of these problems. In this paper, a circuit model for an MI system is presented to describe power transmission between the transceivers and to facilitate performance analysis of this wireless system around the human body. An analytical model is derived for the mutual inductance of two MI coils as a function of coil geometry, operating frequency, and relative position and orientation of the coils. This model provides an accurate and fast method of calculating the mutual induction, which is a key parameter in the optimal design of an MI communication system. The model is verified by experimental measurements and numerical simulations. The results show that for frequencies up to 30 MHz, the human body does not affect the performance of MI communication system.

Recursive Frequency Allocation Scheme in Wireless Power Transfer and Magnetic Induction Communication Systems

Magnetic induction applications mostly rely on resonance for inducing maximum magnetic fields to system loads and hence for each resonant frequency dedicated circuits are required. Unfortunately, the frequency responses of such inductive systems manifest several peaks (frequency splitting) when their coupling coefficients are equal to or larger than critical coupling. Such frequency responses with several peaks are detrimental when the objective is to transfer maximum energy. Frequency splitting between inductive coils have been seen to date as detrimental to wireless power transfer and inductive communication systems. In this paper it is demonstrated that frequency splitting is a welcome phenomenon with advantage in the design of inductive filter banks and multi-frequency inductive systems. The centre frequencies of the filter banks result from split bands of inductive systems. This phenomenon is applied in conjunction with an innovative recursive algorithm to design inductive filter banks. The filters straddle both sides of the resonant frequency position and can be resolved individually.

Design optimization of transmitting antennas for weakly coupled magnetic induction communication systems

This work focuses on the design of transmitting coils in weakly coupled magnetic induction communication systems. We propose several optimization methods that reduce the active, reactive and apparent power consumption of the coil. These problems are formulated as minimization problems, in which the power consumed by the transmitting coil is minimized, under the constraint of providing a required magnetic field at the receiver location. We develop efficient numeric and analytic methods to solve the resulting problems, which are of high dimension, and in certain cases non-convex. For the objective of minimal reactive power an analytic solution for the optimal current distribution in flat disc transmitting coils is provided. This problem is extended to general three-dimensional coils, for which we develop an expression for the optimal current distribution. Considering the objective of minimal apparent power, a method is developed to reduce the computational complexity of the problem by transforming it to an equivalent problem of lower dimension, allowing a quick and accurate numeric solution. These results are verified experimentally by testing a number of coil geometries. The results obtained allow reduced power consumption and increased performances in magnetic induction communication systems. Specifically, for wideband systems, an optimal design of the transmitter coil reduces the peak instantaneous power provided by the transmitter circuitry, and thus reduces its size, complexity and cost.

Increasing the Capacity of Magnetic Induction Communications in RF-Challenged Environments

Magnetic Induction (MI) techniques enable efficient wireless communications in dense media with high material absorptions, such as underground soil medium and oil reservoirs. A wide range of novel and important applications in such RF-challenged environments can be realized based on the MI communication mechanism. Despite the potential advantages, the major bottleneck of the MI communication is the limited channel capacity due to the low MI bandwidth. In this paper, the Spread Resonance (RS) strategy is developed for the MI communication in RF-challenged environments which greatly increases the MI channel capacity. Specifically, instead of using the same resonant frequency for all the MI coils, the spread resonance strategy allocates different resonant frequencies for different MI relay and transceiver coils. An optimization solution for the resonant frequency allocation is formulated to maximize the MI channel capacity which captures multiple unique MI effects, including the parasitic capacitor in each MI coil, the Eddy currents in various transmission media with limited conductivities, and the random direction of each coil. Numerical evaluations are provided to validate the significant channel capacity improvements by the proposed SR strategy for MI communication systems.

INVESTIGATION OF NEAR FIELD INDUCTIVE COMMUNICATION SYSTEM MODELS, CHANNELS AND EXPERIMENTS

Near-fleld inductive channels created between two or more magnetically coupled inductive nodes are studied in this paper. Peer- to-peer conflgurations and array architectures are discussed. The array channels are used for cooperative relaying with inductive methods with potential to provide range extension and enhanced data rate access in magnetic induction communication systems. The received power shows the presence of the nearest neighbour interactions and the in∞uences of higher order coupling from nodes two or more positions away from the receiver. This in∞uence causes phase changes in the communication system. Four methods of exciting the antenna arrays are proposed. These are array edge excitation, center excitation, collinear array excitation and multi-array excitation. Experiments with hardware nodes show that while array edge excitation provides increased power at the array edge, it is out performed by array center excitation which results to twice the power captured at the array center node compared to the power captured at edge excited flrst element. We demonstrate by example that a receiver is in∞uenced most by its neighbouring nodes on both sides and that the efiects of second and third tier neighbours are relatively insigniflcant.

Performance of Magnetic Induction Communication Systems Using Induction Factors

Inductive communication is an emerging physical layer technology for secure communications which has promise to provide significant incentives in body area networks and other short range communication systems. This paper presents the principles and performance of inductive communication systems from the points of view of the efficiencies of the transmitter and receiver topologies. The rapid reduction of power level with distance to power six means that inductive systems should be designed for efficient flux coupling to the receiver. This therefore needs to be quantified. This paper proposes a performance measure using both the trans-impedance and a new factor called the induction factor which describes the magnitude of induced power caused by a transmitter at the receiver. The effects of system parameters on performance are modeled, simulated and discussed. Four system topologies are identified and their performances in terms of the influences of the system components are investigated. Different topologies result to different induced voltages in the receiver. We demonstrate that at frequencies below 1.4 MHz, the performance of the series---series and series---parallel topologies are almost identical. We also show by the induction factor concept that the series---parallel (transmitter---receiver) topology provides more induced voltage to the receiver at high frequencies above 1.4 MHz. This is demonstrated for frequencies up to 4.5 MHz. Many applications use frequencies above 1 MHz, making these results highly essential for inductive system design and development.

Power Equations and Capacity Performance of Magnetic Induction Communication Systems

Although a number of studies have been done on the traditional Radio Frequency (RF)terrestrial communication system, the potential applications and the advantages of Near-Field magnetically coupled coils in wireless short range communications is just emerging and is yet to be explored. This paper investigates the impacts of magnetically coupled transceiver antenna coil on the received signal power and the communication link capacity. Based on the equivalent circuit model in free space, theoretical foundations are laid with observed simulation results. The simulation result benefits the antenna designers and the network planning engineers to estimate the power at the receiver and a near field magnetic communication system capacity for different antenna coil characteristics and different communication ranges.