In this chapter, differences between magnetic communication and electromagnetic wave-based communication are summarized and major advantages of magnetic communication are discussed, which provides a big picture of the applicable scenarios of magnetic communication. In addition, the physical circuit for magnetic communications is introduced. The fundamental performance metrics, such as path loss, bandwidth, capacity, and connectivity are discussed.

Magnetic communication is a novel physical communication technology. To connect a large number of magnetic communication devices, traditional networking protocols can be employed, but we need to make significant modifications on the physical layer to accommodate the special features of magnetic communication. For example, to access the communication medium, traditional carrier-sense multiple access or Zigbee can be adopted, but the magnetic communication has a short communication range, and the antennas of different devices may have substantial coupling, which can affect the communication performance. To address this issue, we need dedicated scheduling algorithms to reduce mutual couplings among coils and increase the network throughput. In this chapter, we first introduce a complete magnetic communication network stack. Then, we show the unique features of magnetic communication at the network level. After that, we introduce the scheduling algorithms for magnetic communication networks.

We study the connectivity of a large-scale ad hoc MI networks, whose nodes are randomly located with randomly deployed MI antennas. The pathloss model we use here considers the effect of MI noise via a signal-to-noise ratio threshold instead of magnetic signal strength. In addition, the effects of carrier frequency and eddy current both are considered for the determination of signal coverage. To study the MI coverage and connectivity under such assumptions, we develop a Lambert W-function-based integral method to evaluate the effective coverage space and the expected node degree of an MI node. The probability of having no isolated node in the network is further derived to estimate the required parameters for an almost surely connected network. Passive MI waveguide is not considered in this chapter. We also performed carrier frequency optimizations.

The so-called magnetic communication makes use of the time-varying magnetic field produced by the transmitting antenna, so that the receiving antenna receives the energy signal by mutual inductance. Research studies show that the penetrability of a magnetic communication system depends on the magnetic permeability of the medium. Because the magnetic permeability of the layer, rock, ice, soil, and ore bed is close to that of the air, channel conditions have less effects on magnetic transmission than electric transmission. Therefore, the communication network based on deep-penetrating MI can expand the perception ability and sensing range of information technology effectively, which can be applied to complex environments such as underground, underwater, tunnel, mountain, rock, ice, and forest. We conclude that the network construction of IoT based on magnetic communication is of great value and can be regarded as one of the reliable technologies to improve the connectivity of a wireless network.

One of the important peculiarities of MI communications is the use of magnetic antennas that can deliver information by using inductive coupling instead of radiation. The magnetic coupling is constrained in the near field, which is more secure since it is not easy to be detected. Moreover, magnetic fields have better penetration efficiency than electric fields. A magnetic antenna is more robust to environment changes than its electric counterpart. In this chapter, we first introduce the fundamentals of antennas to show the difference between magnetic antennas and the widely used electric antennas to gradually narrow our discussion from a big picture. We present the advantages of magnetic antennas and their applicable conditions. Also, we introduce the signal transmission techniques and channel characteristics for the single-input-single-output (SISO) system. Finally, we discuss the multiple-antenna MI system with different antenna placement strategies, which is more reliable and efficient than the SISO system.

In this chapter, several kinds of MI-based applications are introduced. Specifically, the MI-based localization system is one of the most widely used and mature applications of the MI-based techniques. Thus, this chapter first describes several typical MI localization applications, such as the motion capture system, pipeline position systems, and fusion localization with other techniques (such as inertial measurement correction). Second, we summarize some MI-based communication applications for IoT, such as radio frequency identification, through-the-earth communication and underwater communication.

In this chapter, the network throughput and capacity are derived and analyzed. The deployment strategies for MI networks are first introduced. Then, we present the typical network topologies for MI networks. After that, we compare the performance of different network topologies regarding congestion, node failure, and power consumption, among others.

In preceding chapters, we have shown reasons by analyzing the power generated by the magnetic dipole antenna and devising the pathloss model by using the equivalent circuit model. Due to the high path loss, the magnetic communication range is very limited. On the one hand, this can be leveraged to enable secure short-range wireless communications, e.g., near-field communication. On the other hand, magnetic communication cannot be used for many important applications that require a long communication range. In this chapter, we first introduce the magnetic waveguide, which starts from the fundamental analysis of its structure and magnetic field propagation in the air. Then, we extend the discussion to extreme environments and show the range extension. Next, we introduce the metamaterial-based solutions. The spherical metamaterial-resonance structure is analyzed using advanced electromagnetic theory. After that, we present an approach to implement the spherical metamaterial structure. The enhancement is demonstrated by using numerical analysis and experimental measurements.