Proposal of a Visible Light Communication Method for Personalized and Localized Building Energy Management
2016; Electronics and Telecommunications Research Institute; Linguagem: Inglês
10.4218/etrij.16.0116.0120
ISSN2233-7326
AutoresJin-Doo Jeong, Sang‐Kyu Lim, Jinsoo Han, Wan–Ki Park, Il‐Woo Lee, Jong‐Wha Chong,
Tópico(s)Semiconductor Lasers and Optical Devices
ResumoETRI JournalVolume 38, Issue 4 p. 735-745 ArticleFree Access Visible Light Communication Method for Personalized and Localized Building Energy Management Jin-Doo Jeong, Corresponding Author Jin-Doo Jeong [email protected] Corresponding Author[email protected]Search for more papers by this authorSang-Kyu Lim, Sang-Kyu Lim [email protected] Search for more papers by this authorJinsoo Han, Jinsoo Han [email protected] Search for more papers by this authorWan-Ki Park, Wan-Ki Park [email protected] Search for more papers by this authorIl-Woo Lee, Il-Woo Lee [email protected] Search for more papers by this authorJong-Wha Chong, Jong-Wha Chong [email protected] Search for more papers by this author Jin-Doo Jeong, Corresponding Author Jin-Doo Jeong [email protected] Corresponding Author[email protected]Search for more papers by this authorSang-Kyu Lim, Sang-Kyu Lim [email protected] Search for more papers by this authorJinsoo Han, Jinsoo Han [email protected] Search for more papers by this authorWan-Ki Park, Wan-Ki Park [email protected] Search for more papers by this authorIl-Woo Lee, Il-Woo Lee [email protected] Search for more papers by this authorJong-Wha Chong, Jong-Wha Chong [email protected] Search for more papers by this author First published: 01 August 2016 https://doi.org/10.4218/etrij.16.0116.0120Citations: 9 Jin-Doo Jeong (corresponding author, [email protected]), Sang-Kyu Lim ([email protected]), Jinsoo Han ([email protected]), Wan-Ki Park ([email protected]), and Il-Woo Lee ([email protected]) are with the Hyper-connected Communication Research Laboratory, ETRI, Daejeon, Rep. of Korea. Jong-Wha Chong ([email protected]) is with the Department of Electronic Engineering, Hanyang University, Seoul, Rep. of Korea. This work was supported by the Electronics and Telecommunications Research Institute (ETRI) grant funded by the Korea government (16ZC1610, Development of key technologies for energy sharing networking to realize the zero energy community). AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract The Paris agreement at the 21st Conference of the Parties (COP21) emphasizes the reduction of greenhouse gas emissions and increase in energy consumption in all areas. Thus, an important aspect is energy saving in buildings where the lighting is a major component of the electrical energy consumption. This paper proposes a building energy management system employing visible light communication (VLC) based on LED lighting. The proposed management system has key characteristics including personalization and localization by utilizing such VLC advantages as secure communication through light and location-information transmission. Considering the efficient implementation of an energy-consumption adjustment using LED luminaires, this paper adopts variable pulse position modulation (VPPM) as a VLC modulation scheme with simple controllability of the dimming level that is capable of providing a full dimming range. This paper analyzes the VPPM performances according to variable dimming for several schemes, and proposes a VPPM demodulation architecture based on dimming-factor acquisition, which can obtain an improved performance compared to a 2PPM-based scheme. In addition, the effect of a dimming-factor acquisition error is analyzed, and a frame format for minimizing this error effect is proposed. I. Introduction At the 21st Conference of the Parties, which was held in Paris from November 30 to December 11 2015, representatives from all over the world announced targets to reduce greenhouse gas emissions and curtail climate change. The reduction of greenhouse gases aimed by the Paris agreement is related to fossil-fuel oriented energy consumption based on the continuing trends of rising energy demand [1]. For example, the electricity demand and consumption in the U.S. have increased annually over the last 20 years [2]. The current energy crisis owing to increasing energy consumption has required a significant energy reduction in all areas [3]. Both residential and commercial energy management in buildings has become an important aspect of energy saving because of the increasing demand for building services and comfort levels, together with a rise in the time spent inside of buildings [4]. Because lighting is a major component of electrical energy consumption, and lighting systems are a strategic indoor infrastructure, various methods to reduce lighting energy consumption are required. One method generally known for saving lighting energy is controlling the brightness or dimming level of the luminaires, which is normally proportional to the consumption of lighting energy [5], [6]. Another method is replacing incandescent and fluorescent sources with LED luminaires, which have greater energy efficiency and a longer lifetime [7], [8]. Through a combination of these two methods, an additional reduction of lighting energy can be achieved [9]. Therefore, a building pursuing energy efficiency should consider a lighting system based on controllability of the dimming level of the LED lighting system. LED luminaires can synergistically provide dimmable illumination with high energy-efficiency and the wireless transmission of data through visible light, which is called visible light communication (VLC) [10], [11]. VLC technology using LED luminaires, which can reduce the energy consumption compared to conventional lighting sources, is receiving increasing attention in various fields, including indoor broadcasting and entertainment lighting [12], [13]. VLC may also be applied to building energy management systems such as conventional RF wireless modules including ZigBee modules [4], [9], [14]. The possibilities of applying VLC to building energy management are shown in [15] and [16]. However, the methods in [15] and [16] are insufficiently detailed to be implemented, or allow aspects of VLC to be applied, such as location-information transmission [17] and secure communication using light [18], which are difficult to implement in conventional RF wireless communications. In this paper, we propose a more specific method for applying the advantages of VLC to building energy management, and consider a VLC modulation scheme from the perspective of our proposed energy management system. We then analyze the VLC performance and propose an efficient VLC architecture suitable for the proposed building energy management system. II. Approach to Personalized and Localized Building Energy Management Based on VLC In [15] and [16], the possibilities for building an energy management system employing VLC are described. In this section, we describe a systematic approach to a building energy management system based on VLC to support personalized and localized management. Figure 1 shows the proposed building energy management system using VLC. One of the characteristics of the proposed method is to monitor energy data localized using VLC. Information related to the installation location can be embedded into the VLC-LED lighting, and thus location information can be transmitted using VLC [17]. This means that the VLC receiver can extract the location information from a signal received from the nearest VLC-LED luminaire, and a localization energy service is made possible by utilizing the extracted location or position information. For example, as shown in Fig. 1, a user under a VLC-LED luminaire in Section 1 is able to monitor the energy data corresponding to this Section. In addition, another user under a VLC-LED luminaire in Section 2 can receive localized energy monitoring of Section 2. Another characteristic of the proposed energy management system is the capability to control the amount of energy consumption by changing the brightness, or dimming the level of the VLC-LED luminaires. The power consumption of an LED is directly proportional to the dimming level [5]. Thus, the energy consumption can be adjusted by controlling the dimming levels of the VLC-LED luminaires. The transmission of signals for dimming control from user terminals may be conducted using wireless modules such as WiFi, ZigBee, or VLC modules. Using the proposed VLC-based method, selective control of the VLC-LED luminaires can be obtained because the location information extracted from a received VLC signal can be applied to select those luminaires corresponding to the related section, a function that is difficult to implement in other RF wireless modules including ZigBee and WiFi modules. Security and privacy have become important points of energy management applications including smart metering, and users may need to be reassured that their energy data are secure [19]. This paper describes a method for applying spatially secure communications based on VLC to building energy management. The concept of spatially secure communications based on VLC was proposed in [18]. As described in [18], only a user in a lighted area under a VLC luminaire is able to use the wireless communication function because the encryption key for the communications is delivered through VLC. Therefore, secure communications in the space dimension can be obtained using VLC, whereas this feature is difficult to implement in conventional RF wireless communications. Spatially secure communications based on VLC can improve the privacy-preserving services of energy management. In other words, personalized building energy management from the perspective of enhanced privacy is possible using VLC-based management. In this paper, we use a flowchart for a detailed description of the proposed management system. Figure 2 shows a flowchart of personalized and localized building energy management using VLC. A VLC-LED luminaire transmits VLC-modulated signals for information related to its location or position. A user terminal extracts the location information from the received VLC signal through VLC demodulation. The user or user terminal generates user information through a user login and transmits this information to the energy management server. Communication between the user terminal and server can be established using conventional wireless methods, such as WiFi and ZigBee, or through a combination of VLC and a backbone network. The energy management server conducts user authentication using the transferred user and location information. If the server determines that the user is not conducting energy management under the corresponding VLC-LED luminaire, the server transfers a prohibition message regarding the energy management. Otherwise, the server generates a security code using the user and location information and transfers this code to the VLC-LED luminaire above the permitted user. The VLC-LED luminaire conducts VLC modulation of the security code and transfers the security code through visible light. After VLC demodulation, the user terminal extracts the security code utilized for spatially secure communications between the user terminal and energy management server. The rest of the flowchart shows the processes for energy-usage monitoring and energy-consumption adjustment. When a request for energy-usage is received from a permitted user or user terminal, the energy management server conducts an analysis of the energy database based on the corresponding user and location, and transfers a request for related energy data. The server extracts the energy-usage information from the energy data transferred from the energy data aggregator, and transmits this information to the user terminal. The user or user terminal can set and transmit the results of an energy-consumption adjustment by referring to the adjustable energy information received from the management server. The server then generates control information regarding the LED luminaires according to the setting information received, and transmits the LED-control information to the VLC-LED luminaires. The energy consumption can be adjusted by controlling the dimming levels of the VLC-LED luminaires receiving control information from the energy management server. Figure 2 shows that the application of VLC to building energy management can achieve personalized and localized management suitable for the user and the user's location, and furthermore supports spatially secure privacy preservation. This indicates that VLC can provide differentiated services for building energy management compared to methods using conventional RF-based wireless modules such as WiFi and ZigBee modules. On the other hand, several issues should be considered when building energy management based on VLC is established, whereas no such issues exist for conventional management systems using RF wireless methods. One issue is a simple and reliable way to control the dimming level of VLC-LED luminaires for energy-consumption adjustment while maintaining wireless communication using visible light. The proposed energy management method shown in Figs. 1 and 2 requires more highly available dimming control of VLC-LED lighting than a high data rate implemented normally through OFDM, which may be sensitive to dimming control because VLC used by the proposed management system transmits the location information and a security code consisting of relatively small-sized data. Various VLC modulation methods supporting highly available dimming control such as variable on-off keying and variable pulse position modulation (VPPM) have been presented [20], [21]. VPPM has attracted attention because it is easy to implement and is capable of providing a full dimming range [21]. In addition, VPPM is one of the modulation methods adopted in the IEEE 802.1.5.7 standard [22], [23]. Furthermore, VPPM lighting with high-resolution dimming control appropriate for the fine control of lighting energy consumption can be implemented simply and efficiently [24]. For these reasons, VPPM is considered for the VLC modulation of the proposed building energy management system. In the next section, the theoretical performance of the VPPM is described under variable dimming levels for when an adjustment of the energy-consumption is required. Figure 1Open in figure viewerPowerPoint Concept of building energy management using VLC. Figure 2Open in figure viewerPowerPoint Flowchart for personalized and localized building energy management using VLC. III. Theoretical Performance of VPPM as VLC Modulation for the Proposed Energy Management System The VPPM incorporates the main advantages of 2PPM for VLC, and pulse-width modulation (PWM) for dimming control. Figure 3 shows a signal waveform of VPPM modulation. VPPM modulates transmitted data using a pulse position such as 2PPM. This is similar to PWM in that the pulse width can be controlled in accordance with the required dimming level [22]. 2PPM is equal to 50% dimmed VPPM [23]. Figure 3Open in figure viewerPowerPoint Signal waveform of VPPM modulation [22], [23]. In [25], the complex nature of VLC links is conveniently transformed into a widely understood additive white Gaussian noise (AWGN) channel description. Many previous studies [20], [26], and [27] have also analyzed the VLC performance in an AWGN channel. Based on [28], the BER in an AWGN channel can also be expressed as (1) where d01 indicates the distance between two signals, that is, s0 for bit 0 and signal s1 for bit 1. In addition, N0 denotes the power spectral-density of the noise. VPPM waveforms can be created using codewords in the discrete-time domain, as described in [20]. To analyze and evaluate the detection performance of VPPM signals, M-length VPPM symbols, whose dimming step is 1/M and dimming-factor γ is m1/M, can be defined as (2) where m1 and m0 denote the number of samples required to designate a high-level section, respectively, which means the light is on, and a low-level section, which means the light is off, within the unit time period of a symbol composed of M samples. Thus, M is and m0/M is equal to . It is reasonable to set Eb to the bit energy at full brightness and under the output of a photo-detector (PD) by considering the energy change owing to the use of variable dimming and the square root transform at the PD [25]. The theoretical BER for VPPM signals can be represented through (3) using . (3) The VPPM demodulator through the performance of (3) can be designed using a correlation-based method described in [28]. However, implementing the VPPM correlation-based demodulator typically requires correlators while considering the dimmable VPPM waveform references. This indicates that the hardware complexity of the correlation-based demodulator is relatively high. In the next section, we describe the architecture for VPPM demodulation based on the 2PPM mechanism, which normally may be simply designed, and analyze the performance of VPPM demodulation applied with the 2PPM mechanism. IV. VPPM Performance Based on 2PPM Demodulation Mechanism with Simple Architecture A simple architecture for demodulating a VPPM signal can be obtained using the 2PPM mechanism. An architecture based on the 2PPM mechanism in the discrete-time domain can be obtained by applying the 2PPM correlation reference to the architecture in the continuous-time domain in [29]. 2PPM demodulation has one correlation with a 50% dimming reference for bit 0 and another correlation for bit 1. As shown in Fig. 4, VPPM demodulation based on the 2PPM mechanism requires only two correlators, in contrast to the correlation-based method described in Section III. The correlator detecting bit 0 has a role in the accumulation of the former half of the samples in a VPPM symbol, as shown in Fig. 4. Similarly, the latter half of the samples is accumulated through the correlator that detects bit 1. In other words, VPPM demodulation based on the 2PPM mechanism can be processed through the accumulation of both the former and latter samples in a symbol, and through a comparison of the accumulated values. Of these properties, the demodulation in Fig. 4 can be designed using an architecture with two accumulators, as shown in Fig. 5. Figure 4Open in figure viewerPowerPoint Block diagram of VPPM demodulation based on 2PPM mechanism. The received data are detected through a comparison of the accumulations for bits 0 and 1, as shown in Fig. 5. For a VPPM signal transmitted for bit 0 with a dimming of less than 50%, that is, , the energy of the signal and noise in the compared process or comparator shown in Fig. 5 can be expressed as (4) Figure 5Open in figure viewerPowerPoint Architecture of 2PPM-based VPPM demodulation with two accumulators. In (4), E{ } is an expectation operation, and is the noise at the i-th sample in the correlator. In addition, Σ2PPM_0 and Σ2PPM_1 represent accumulations for bits 0 and 1, respectively. The result of the VPPM signal for bit 1 is the same as the result of (4). In a similar manner, energy in the comparison process for dimming of over 50%, that is, , can be obtained through (5). (5) Considering the 2PPM-based demodulation for dimming signals of over 50%, as shown in (5), the overlapping region between signals s0 and s1 cancel each other out. In (4) and (5), the first term is related to the signal energy, and the second term represents the noise power. The BER for 2PPM-based VPPM demodulation can then be expressed as (6). (6) The BER performance of 2PPM-based VPPM demodulation is inferior to that of the theoretical VPPM performance in (3) because the SNR of the 2PPM-based scheme is proportional to the square of dimming-factor γ, whereas that in (3) is proportional to γ. In the proposed building energy management system described in Section II, a request for an energy-consumption adjustment induces a change in the dimming levels of the VLC-LED lighting when VLC functions for the proposed management should be supported. In other words, it is important for the VLC performance to be as good as possible while the dimming level for the energy-consumption adjustment is variable. This means that the degradation of the VLC performance owing to a change in dimming has to be reduced. In the next section, we propose an architecture that can be used to improve the VPPM demodulation based on a 2PPM mechanism and is suitable for the proposed building energy management system. V. Novel VPPM Demodulation Architecture for the Proposed Energy Management Based on the analysis described in section IV, this paper proposes a performance-improved VPPM demodulation scheme to be efficiently applied to the proposed building energy management system. The proposed method is based on two correlators originating from the 2PPM demodulation mechanism to reduce the complexity and enhance the efficiency. As shown in (4), the performance of the 2PPM-based VPPM demodulation is degraded because the number of pulse-on samples m1 is smaller than the number of accumulation samples NΣ. Therefore, noise samples in the pulse-off region affect the signal detection. In the case of dimming of over 50%, SNR degradation is caused by the mutual canceling of signals in (5). To overcome this degradation, we propose a method for varying the accumulation number NΣ. In other words, the accumulation region of the received samples in each of the accumulators for bits 0 and 1 is controlled according to the dimming-factor of the received VPPM signals. From (4) and (5), variable accumulation number NΣ used to overcome the performance degradation from noises or a signal overlap can be set as follows: (7) The performance of the proposed VPPM method was also assessed through an SNR analysis similar to 2PPM-based demodulation. The energy of the comparison process, which accumulates the received samples according to NΣ, can be expressed through (8) for a VPPM signal transmitted for bit 0 with a dimming of less than 50%. The result of the VPPM signal for bit 1 provides the same result as (8). (8) In a similar manner, the energy of the comparison process for dimming of over 50%, where , can be derived as (9) From (8) and (9), the SNR for 2PPM-based VPPM demodulation can be extracted as in (10). (10) Equation (10) shows that the BER of the proposed VPPM scheme is equal to that of the theoretical approach in (3). In other words, the proposed demodulation can achieve the same performance as the theoretical approach under the assumption that the acquisition of dimming-factor γ is perfect. This is shown in Fig. 6 based on the BER simulation results for the 2PPM-based and proposed methods. Figure 6 also shows that performance of the proposed method is superior to that of the 2PPM-based method, with the exception of . Figure 6Open in figure viewerPowerPoint Simulation results for the 2PPM-based and proposed methods. The normalized variable accumulation region (NVAR), AΣ, can be expressed as (11) from (7). (11) Figure 7 shows the architecture of the proposed demodulation based on the NVAR parameter. It is possible to design the proposed architecture by adding logic applying NVAR parameter AΣ to the 2PPM-based architecture described in Fig. 5. This means that the proposed demodulation can obtain a level of performance approximately equal to that of the theoretical approach described in Section III. Therefore, the proposed VPPM architecture is more robust in terms of performance than the 2PPM-based VPPM architecture when VPPM is used for the proposed building energy management system described in Section II. Figure 7Open in figure viewerPowerPoint Architecture of the proposed VPPM demodulation. VI. Effect of Dimming-Factor Acquisition Error and Proposal of Frame Format for the Proposed Energy Management Based on VPPM VLC The VPPM demodulation method proposed for efficiently implementing the VLC-based building energy management system is based on NVAR AΣ according to dimming-factor γ. This means that the performance of the proposed method is affected by an error in the dimming-factor acquisition. The error effect on the dimming-factor acquisition was assessed in terms of the SNR when considering an incorrect accumulation. For a VPPM signal transmitted for bit 0 with a dimming of less than 50% and a smaller dimming-factor acquisition , where moff is an integer between zero and m1, as compared to the desired m1, the energy of the comparison method can be expressed through (12) by considering (7) as (12) When the dimming-factor acquisition , where moff is an integer between zero and , is larger than the desired m1, energy can be expressed as (13) In a similar manner, the energies for a dimming of over 50% can be derived through (14) and (15) by considering (7). (14) (15) The SNRs of the proposed method when considering the error effects during the dimming-factor acquisition can be derived from (12) through (15) as follows: (16) (17) (18) (19) As shown in (16) through (19), the effect of the dimming-factor acquisition error is dependent upon the direction of the acquisition error. In the cases of (16) and (19), the acquisition error reduces the signal-power. On the other hand, the noise effect is increased from any occurring errors, as shown in (17) and (18). Figure 8 shows the simulation results for the effect of the dimming-factor acquisition error. In Fig. 8, the sign of dimming-factor acquisition error γoff means the direction of the acquisition error, and thus the negative side at the zero acquisition error represents cases when the dimming-factor acquisitions are smaller than the desired acquisition. In Fig. 8, the simulation results are almost equal to the theoretical results in an error range of between and 0.2. However, when the dimming-factor γ is 0.3, as shown in Fig. 8, which is smaller than 0.5, the demodulation scheme for the ranges over 50% dimming, as shown in Fig. 7, is applied. On the other hand, when the dimming-factor γ is 0.7, which is bigger than 0.5, the demodulation scheme for the ranges under 50% dimming is applied. For these reasons, the theoretical results do not correspond to the simulation results except within the range between and 0.2. Thus, some additional analyses may be needed. Figure 8Open in figure viewerPowerPoint Simulation results for the effect of the dimming-factor acquisition error. One of the methods for obtaining the dimming-factor in the receiver is to estimate the dimming-factor from the received VPPM signals using a signal-processing algorithm. However, the estimation methods require additional hardware resources and are sensitive to channel noise and changes in dimming. Another method for dimming-factor acquisition can be obtained using a frame format or packet structure appropriate for dimmable VPPM VLC systems. Figure 9 shows a frame format for the VPPM communication proposed in this paper. The proposed frame format is based on two fields that are not in other communication frame formats. In this paper, one is termed the dimming-factor field, and the other is the variable dimming buffer field. The dimming-factor field indicates the dimming level in the payload, which is typically the bulk of the frame. The physical-layer header (PHR) including the dimming-factor field is modulated at a 50% dimming level, at which the BER performance is the best, as shown in Fig. 6, as in IEEE 802.11a WLAN [30]. This means that the error rate is minimized in a PHR containing important frame information such as the payload length. Dimming-factor acquisition for the proposed demodulation scheme is achieved through PHR extraction in the VPPM VLC receiver. A variable dimming buffer field has no information but acts as the guard time to allow error data that may occur owing to an abrupt change in dimming to be ignored. Detection parameters such as the moving average for removing the DC component can be adapted for use in a payload with variable dimming in a variable dimming buffer field. Figure 9Open in figure viewerPowerPoint Proposed frame format for dimmable VPPM VLC systems. The VPPM demodulation scheme proposed in Section V can achieve a better level of performance than 2PPM-based demodulation, but is affected by errors in the dimming-factor acquisition. Therefore, the proposed VPPM demodulation scheme can be applied along with the proposed frame format to obtain a robust performance and satisfy the key characteristics of the building energy management, as proposed in Section II, in which the VLC performance is as good as possible, with a variable dimming level for the energy-consumption adjustment. To gain a further reduction in the error effect and enhance the performance of PPM-based VLC, algorithms such as a soft value calculation for LDPC coded PPM [31], group modulation [32], and a separate dimming controlling method [33] can be applied. In addition, when the simple architecture for designing VPPM lighting presented in [24] is also applied, a robust and complexity-efficient implementation of VPPM VLC for the proposed building energy management system can be achieved. VII. Conclusion This paper proposed a personalized and localized building energy management system based on VLC-LED lighting by applying the advantages of VLC, such as spatially secure communication and location-information transmission. In this paper, we adopted the VPPM scheme as a type of VLC modulation suitable for the proposed management system, which has a simple controllability of the dimming level and is capable of providing a full dimming range. This paper analyzed the VPPM performance according to variable dimming under several different schemes in order to check whether the VLC performance is as good as possible under a variable dimming level for an adjustment of the energy consumption. In addition, this paper proposed a VPPM demodulation architecture based on the dimming-factor acquisition, whose performance is superior to that of a 2PPM-based scheme and nearly equal to the theoretical performance. Furthermore, this paper analyzed the effects of the dimming-factor acquisition error and proposed a frame format for minimizing the error effect. Using the proposed VPPM demodulation and frame format, a personalized and localized building energy management system employing VPPM VLC can be implemented efficiently and robustly. Biographies Jin-Doo Jeong received his BS degree in electronic engineering in 1998 and his MS degree in electronic and communication engineering in 2000 from Hanyang University, Seoul, Rep. of Korea. In 2010, he joined ETRI, Daejeon, Rep. of Korea, where he has worked on wireless personal area communication systems using UWB and VLC. He is a senior researcher in ETRI, and is concentrating on the area of energy IT technology including smart metering and wireless energy management. Sang-Kyu Lim received his BS degree in physics in 1995, and his MS and PhD degrees in electronics engineering in 1997 and 2001, respectively, from Sogang University, Seoul, Rep. of Korea. Since he joined ETRI, Daejeon, Rep. of Korea, in 2001, he has worked on high-speed optical transmission systems and microwave/millimeter-wave circuit designs. He is currently concentrating on visible light communication and lighting control networks, and has been one of the major contributors in developing the IEEE 802.15.7 standard. He is a principal member of the engineering staff at ETRI and is a senior member of IEEE. Jinsoo Han received his BS degree in electronics engineering from Yonsei University, Seoul, Rep. of Korea in 1998, and his MS degree in electrical and electronics engineering from KAIST, Daejeon, Rep. of Korea in 2000. He is currently a PhD candidate at Chungnam National University, Daejeon, Rep. of Korea. He joined ETRI, Daejeon, Rep. of Korea in 2000, where he has been involved in the development of optical communication systems and optical networks. He has also been engaged in the research and development of home gateway and home server systems, wired and wireless home networks, and power management systems. His current research interests are in wireless sensor networks (WSNs), home/building energy management, and green IT solutions. Wan-Ki Park received his BS and MS degrees in electronics engineering from Chungnam National University, Daejeon, Rep. of Korea in 1991 and 1993, respectively, and his PhD degree in information communication engineering from the same university in 2006. He joined the Agency for Defense Development, Daejeon, Rep. of Korea, in 1993 and was engaged in the research and development of military-related communications until 2000. He joined ETRI, Daejeon, Rep. of Korea in July 2000 and has been engaged in the research and development of energy IT technologesy to conserve energy in the consumer domain and micro-grids. His research interests are in IoT applications and a system architecture for green homes and buildings and smart grids. Il-Woo Lee received his BS and MS degrees in computer science from Kyung Hee University, Seoul, Rep. of Korea in 1992 and 1994, respectively, and his PhD degree in computer science from Chungnam National University, Daejeon, Rep. of Korea in 2007. He joined ETRI, Daejeon, Rep. of Korea in 1994 and has been engaged in the research and development of CDMA, TDX-10 ISDN, high-speed routing systems, and home network systems. He is currently the director of the energy IT technology research section, and his research interests include smart grid/microgrid platforms, DER, energy trading, and energy informatics. Jong-Wha Chong received his BS and MS degrees in electronics engineering from Hanyang University, Seoul, Rep. of Korea, in 1975 and 1979, respectively, and his PhD degree in electronics and communication engineering from Waseda University, Tokyo, Japan, in 1981. Since 1981, he has been with the Department of Electronics Engineering at Hanyang University, where he is now a chair professor. From 1979 to 1980, he was a researcher at the C&C Research Center of Nippon Electronic Company, Tokyo, Japan. From 1983 to 1984, he was a visiting researcher at the Korean Institute of Electronics & Technology, Seongnam, Rep. of Korea. 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