Magnetic Communication Research Articles

The Magnetic Induction Communications for the Wireless Underground Sensor Networks

The most important difference between the wireless underground sensor networks (WUSNs) andthe wireless ground sensor networksis the propagation environment of the signal .In fact, the underground environments consist of soil, rock and water instead of the air. The challenging reasons of these environments to propagate the wireless signal via the Electro Magnetic (EM) 2waves are considered as: the high path loss, channel dynamic conditions and the high size of antenna. At the present study, the details of Bit Error Rate (BER) 3 for 2PSK modulation, path loss and the bandwidth of the Magnetic Induction (MI) 4Systems and Electro Magnetic (EM) Waveguide in the underground environment areevaluated. Meanwhile, a new method isintroduced via MI waveguide that provided the constant conditions of channel by the small inductive coils. At the end of this study,itisfounded that the transmission range in MI waveguide system would be raised and the path loss in that system would be declined severely.

Magnetic Resonant Coupling for Magnetic Induction Wireless Communication

In the last decade, magnetic induction (MI) communication has drawn the attention of researchers to alternate the EM communication in some environments, such as the underground environment, littoral environment, underwater environment, and caves. By using MI communication, dynamic communication channel, large size antenna and multipath fading can be solved. However, the path loss of MI communication is too high, and limits its transmission range. In this paper, we combine the magnetic resonant coupling method, which is used for wireless power transfer, with the traditional MI communication to reduce the path loss and improve the transmission range. We analyze channel characteristics of this improved MI communication and compare these with those of traditional MI communication. We have also identified two key factors that can increase the receiving power, reduce the path loss, and increase the transmission range.

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.

Maximizing the Capacity of Magnetic Induction Communication for Embedded Sensor Networks in Strongly and Loosely Coupled Regions

We attempt to maximize the capacity of magnetic induction communication in strongly and loosely coupled regions. In a strongly coupled region, we investigate frequency splitting, which disturbs the resonance of transmitter and receiver coils. We find a splitting coupling point, which is the value just before frequency splitting occurs, and propose an adaptive frequency-tracking scheme for finding an optimal frequency. The proposed scheme compensates for the degradation of capacity and so guarantees large capacity even at regions where frequency splitting occurs. Next, in a loosely coupled region, we derive an optimal quality factor for maximizing capacity in a two-coil system. As the distance between coils increases, strong resonance is needed to overcome the serious attenuation of signal strength. As a result, the optimal quality factor should be increased. In addition, we find an optimal quality factor for a relay system in order to guarantee reliable communication at long distance. In addition, an optimal- Q scheme that adjusts the optimal quality factor according to a given distance can achieve near-optimal capacity. Finally, through simulations using the Agilent Advanced Design System, we demonstrate the accuracy of our analytic results and the effectiveness of the proposed schemes.

Multihop Relay Techniques for Communication Range Extension in Near-Field Magnetic Induction Communication Systems

munications and near field magnetic induction communication (NFMIC) is discussed. Three multihop relay strategies for NFMIC are proposed: Non Line of Sight Magnetic Induction Relay (NLoS-MI Relay), Non Line of Sight Master/Assistant Magnetic Induction Relay1 (NLoS-MAMI Relay1) and Non Line of Sight Master/Assistant Magnetic Induction Relay2 (NLoSMAMI Relay2). In the first approach only one node contributes to the communication, while in the other two techniques (which are based on a master-assistant strategy), two relaying nodes are employed. This paper shows that these three techniques can be used to overcome the problem of dead spots within a body area network and extend the communication range without increasing the transmission power and the antenna size or decreasing receiver sensitivity. The impact of the separation distance between the nodes on the achievable RSS and channel data rate is evaluated for the three techniques. It is demonstrated that the technique which is most effective depends on the specific network topology. Optimum selection of nodes as relay master and assistant based on the location of the nodes is discussed. The paper also studies the impact of the quality factor on achievable data rate. It is shown that to obtain the highest data rate, the optimum quality factor needs to be determined for each proposed cooperative communication method.

Pulsed magnetic induction for underground wireless communication

Magnetic induction (MI) communication has been an emerging communication technology to alternate electromagnetic communication in underground environment. However, the path loss of MI communication is too high, and limits its transmission range. In order to increase the transmission range, the direct way is to raise the transmitting power. However, in underground environment, the power supply cannot be large because of the limited size of apparatuses. In this paper, we use pulsed power to solve this problem and use a capacitor connected with receiver coil to form a resonant circuit. These above ideas are all analysed theoretically and compared with traditional MI communication. The results show that this method can improve the transmission range. Some key factors that can influence the transmission effect are also found in this paper.

Pulsed Magnetic Induction for Underground Wireless Communication

Magnetic induction (MI) communication has been an emerging communication technology to alternate electromagnetic communication in underground environment. However, the path loss of MI communication is too high, and limits its transmission range. In order to increase the transmission range, the direct way is to raise the transmitting power. However, in underground environment, the power supply cannot be large because of the limited size of apparatuses. In this paper, we use pulsed power to solve this problem and use a capacitor connected with receiver coil to form a resonant circuit. These above ideas are all analysed theoretically and compared with traditional MI communication. The results show that this method can improve the transmission range. Some key factors that can influence the transmission effect are also found in this paper.

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.

NFMIC Cooperative Communication Methods for Body Area Networks

To achieve higher data rate or to extend the coverage range of a wireless communication system, cooperative relay has been seen as a promising solution. This concept has been integrated in many traditional wireless communication networks. However, it has not been extensively examined for near field magnetic induction communication (NFMIC) systems. This paper aims to apply cooperative relay to NFMIC in a sense that is applicable to body area networking, since NFMIC is stated to be a suitable physical layer for body area networks. We have shown that using idle NFMIC nodes as relaying terminals, the system performance will be enhanced, as compared to a point to point communication system. In this context we have proposed three relaying methods to enhance the data rate and the received signal power in a personal area network. The relaying strategies are denoted as MI-Relay, MAMI Relay1 and MAMI Relay2. In this paper, using theoretical studies and simulation results, we have compared the performance of the three strategies and we have shown that higher data rates can be achieved through MAMI Relay1. However, we have discussed that the separation distance between relaying nodes and the source or destination can be a key factor for relay node selection.

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.

Magnetic Induction for Underwater Wireless Communication Networks

Although acoustic waves are the most versatile and widely used physical layer technology for underwater wireless communication networks (UWCNs), they are adversely affected by ambient noise, multipath propagation, and fading. The large propagation delays, low bandwidth, and high bit error rates of the underwater acoustic channel hinder communication as well. These operational limits call for complementary technologies or communication alternatives when the acoustic channel is severely degraded. Magnetic induction (MI) is a promising technique for UWCNs that is not affected by large propagation delays, multipath propagation, and fading. In this paper, the MI communication channel has been modeled. Its propagation characteristics have been compared to the electromagnetic and acoustic communication systems through theoretical analysis and numerical evaluations. The results prove the feasibility of MI communication in underwater environments. The MI waveguide technique is developed to reduce path loss. The communication range between source and destination is considerably extended to hundreds of meters in fresh water due to its superior bit error rate performance.

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.

Magnetic Induction Communications for Wireless Underground Sensor Networks

The main difference between the wireless underground sensor networks (WUSNs) and the terrestrial wireless sensor networks is the signal propagation medium. The underground is a challenging environment for wireless communications since the propagation medium is no longer air but soil, rock and water. The well established wireless signal propagation techniques using electromagnetic (EM) waves do not work well in this environment due to three problems: high path loss, dynamic channel condition and large antenna size. New techniques using magnetic induction (MI) create constant channel condition and can accomplish the communication with small size coils. In this paper, detailed analysis on the path loss and the bandwidth of the MI system in underground soil medium is provided. Based on the channel analysis, the MI waveguide technique for communication is developed in order to reduce the high path loss of the traditional EM wave system and the ordinary MI system. The performance of the EM wave system, the ordinary MI system and our improved MI waveguide system are quantitatively compared. The results reveal that the transmission range of the MI waveguide system is dramatically increased.

Near-field magnetic communication

Even as cell phones have shrunk in size while boasting an ever-increasing array of features, two things about them haven't changed much: they still sprout a stubby antenna and, if you want a headset, you have to put up with an unwieldy wire connecting the headset and the phone. Thanks to a patented technology called near-field magnetic communication (NFMC), from Aura Communications, one can also cut the cord between the phone and the headset. While the concepts behind magnetic induction communication have been around for decades, Aura's engineers are the first to develop and implement practical solutions capturing the benefits of this technology. NFMC communicates wirelessly by coupling a very-low-power quasistatic magnetic field at 13.56 MHz. This paper discusses further the benefits of this technology.