A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> HBC Technologies <s> The human body characteristics as a signal transmission medium are studied for the application to intrabody communication. The measurements of the body channel cover the frequency range from 100 kHz to 150 MHz and the distance on the body up to 1.2 m. A distributed RC model is developed to analyze the large variation of the channel properties according to the frequency and channel length. The simulation results using the channel model match well with the measurements in both the frequency and time domains. The effect of the ground plane to the body channel transceivers is also investigated and an empirical formula for the minimum ground size is obtained. Finally, the amount of the electromagnetic radiation due to the body antenna effect is measured. With regards to the Federal Communications Commission regulations, the proper frequency range for the intrabody communication is determined to satisfy given bit error rate requirements <s> BIB001 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> HBC Technologies <s> Body-coupled communications (BCC), in which the human body is used as a communications channel, has been shown to be a promising solution for wireless body-area networks (WBANs). For successful deployment of these BCC-based WBANs, it is necessary to develop a clear understanding of the channel behavior. Therefore, this paper presents the key characteristics of the capacitively-coupled on-body channel used for BCC. This is based on an experimental study, which was carried out with a specifically designed measurement system. The goal of the study was to reveal the influence of electrode design, electrode position and body motion on the propagation loss and to characterize the experienced interference. It is concluded that the maximum propagation loss for the whole body channel is below 80 dB. Moreover, the frequency dispersion and the influence of body movement on channel attenuation are shown to be much smaller than for radio frequency (RF) WBAN channels. From the results we conclude that BCC can result in a simpler, more robust, and lower-power WBAN than what is achievable with traditional RF solutions. <s> BIB002 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> HBC Technologies <s> Electronic devices in contact or in close proximity to the human body can use its conductive properties to establish body coupled communication (BCC) between each other. This human centric communication paradigm can be used for wireless body-area networks to reduce the impact of interference on/from RF systems, to avoid the fading effect that the body has on radio systems and to enable power efficient, high data-rate wireless links. <s> BIB003 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> HBC Technologies <s> Biomedical sensor research is moving towards portable, wearable and implantable designs. Human body communication (HBC) is a promising data transmission method for low-power and high-speed biomedical sensors. Using the conductive human body as transmission medium, HBC trials has significant potential applications for personal healthcare and sports performance. The human body channel investigation identifies an optimum channel bandwidth of 1MHz to 100MHz. To further show better performance and reduce power consumption, the proposed baseband system for human body channel incorporates forward error correction (FEC) coding and FSK modulation technique. The extended Binary Primitive BCH Codes for compensating the elevated BER as FEC are adopted in HBC. The BCH-FSK Baseband (BFB) system for HBC has performed high-efficiency transmission for human body channel communication (HBCC). <s> BIB004
Unlinke the other two WBAN PHY layer wireless technologies, HBC uses the human body as the communication medium. HBC transceivers enable low-power communication at low frequencies. Previous studies have shown that the optimal operation frequency range for body coupled communications ranges between 10-100 MHz BIB001 BIB002 . The lower bound is imposed by propagation losses while the upper bound is determined by the fact that the RF energy is no longer confined to the body but is radiated into the environment. Therefore, HBC signals must be modulated to a carrier lower than 100 MHz, before being capacitively coupled to the body via electrodes on or near the surface of the skin. Recently published works on HBC transceivers  BIB003 have shown energy efficiency in the order of 1 nJ/bit, data rates of 1 Mbps and receiver sensitivity of −60 to −70 dBm. The low amount of power radiated outside the body by an HBC transceiver provides a layer of inherent security to the user, allowing spectrum reuse between adjacent users without requiring an explicit cellular structure. A major concern, however, is the interference cancellation due to the presence of high-powered television and radio stations that coexist in the same bandwidth. The authors in  adopt a cognitive FSK modulation to avoid frequencies with high interference, whereas the authors in BIB003 employ a high-input resistance at the receiver to reject offending spectrum above 30 MHz, and a correlation-based scheme to reject signals with low correlation with respect to the expected received signals. An overview of the presented related work on PHY layer transmission techniques has been provided in Table 3 . BIB003 Transceiver design and simulation study BIB004 Baseband system design and simulation study