An Energy-Efficient Pulse Position Modulation Transmitter for Galvanic Intrabody Communications MirHojjat Seyedi, Zibo Cai, and Daniel T.H. Lai College of Engineering and Science Victoria University Melbourne, Australia mirhojjat.seyedi@live.vu.edu.au Francois Rivet University of Bordeaux IMS Laboratory Bordeaux, France francois.rivet@ims-bordeaux.fr Abstract— Intrabody communications (IBC) is a novel communication technique which uses the human body itself as the signal propagation medium. This communication method is categorized as a physical layer of IEEE 802.15.6 or Wireless Body Area Network (WBAN) standard. It is significant to investigate the IBC systems to improve the transceiver design characteristics such as data rate and power consumption. In this paper, we propose a new IBC transmitter implementing pulse position modulation (PPM) scheme based on impulse radio. A FPGA is employed to implement the architecture of a carrier- free PPM transmission. Results demonstrate the data rate of 1.56 Mb/s which is suitable for the galvanic coupling IBC method. The PPM transmitter power consumption is 2.0 mW with 3.3 V supply voltage. Having energy efficiency as low as 1.28 nJ/bit provides an enhanced solution for portable biomedical applications based on body area networks. Keywords-energy-efficient; FPGA; galvanic coupling; intrabody communication; pulse position modulation; I. INTRODUCTION Imagine a world in which simply as you go about your daily life, your medical check-up happens every day. Such systematic monitoring helps to defuse the reliance on medical personnel for current medical disorders like heart attack or stroke. It could prevent frequent hospital visits and save costs for both patient and healthcare system [1]. Nowadays, wireless portable monitoring devices present a revolutionary change in healthcare applications by means of portable devices. WBAN (wireless body area network) is a new ratified communication protocol to standardize the use of wireless techniques in, on, and around the human body. This protocol outlined three physical layer schemes as ultra-wideband (UWB), narrowband (NB), and human body communication (HBC). The human- centric WBAN operation needs to take the technical hardware requirements into account. This raises research issues concerning transceiver circuit design, as a fundamental stage of WBAN system, particularly reducing power consumption while improving the data rate. Among the WBAN PHYs, HBC is energy efficient compared to both UWB and NB. For instance, the reported energy consumption for an UWB communication system was 2.5 nJ/b. While a 0.24 nJ/b was indicated for the recent HBC system [2]. HBC or Intrabody Communication (IBC) is a novel data communication technique using the human body itself as the propagation medium with transmission power below 1.0 mW. IBC can be classified into two basic procedures: Capacitive coupling method and Galvanic coupling method. The former achieved up to 10 Mb/s data rates in the tens of MHz frequency bands and the latter approximately 64 kb/s for frequencies less than 10 MHz [3]. Depending on different kinds of biomedical signals, i.e. analog or digital, the IBC transceiver may consist of one or more subsystems such as analog-to-digital or digital-to-analog converter (ADC or DAC) [4]. Based on the human body channel limitations and body tissues characteristics in different frequency domain, direct data transmission through the human body lead to a large transmitted voltage or power [5]. Therefore, signals produced by various medical devices are not always suitable for direct transmission over a body channel. Hence a modulator or demodulator should be considered in IBC transceiver design. The first IBC transceiver was proposed by Zimmerman in 1995 [6]. He employed on-off keying (OOK) modulation scheme in the IBC system due to its simple design and implementation. This preliminary prototype of capacitive coupling IBC indicated data rate and power consumption of 2.4 kb/s and 400 mW, respectively. Following several attempts which employed different kinds of analog and digital modulation schemes [7, 8], in 2012, Bae et al. [2] reported the analog IBC transceiver which used a double-FSK (frequency shift keying) modulation scheme which decreased the power consumption of the transceiver to 5.4 mW. Meanwhile, in some of the past studies, the coded digital signal was directly transmitted through the body [9, 10]. They proposed the digital Manchester data encoding transmitter. Harikomar et al. [10] used a field-programmable gate array (FPGA) to transmit the digital Manchester coded data through the human body without any modulation. Since neither modulation module nor analog to digital converter (ADC) are required in digital transmitter method, the power consumption of their system was 2.0 mW. However, an error in Manchester code signals leads to a huge bit error in entire received signal. The main objective of this paper is to implement the energy efficient MOBIHEALTH 2014, November 03-05, Athens, Greece Copyright © 2014 ICST DOI 10.4108/icst.mobihealth.2014.257342