Assessment of Communication Technology Alternatives for a Home Energy Management System in Premises Area Network B. Desong, Student, IEEE, M. Kuzlu, Member, IEEE, M. Pipattanasomporn, Senior Member, IEEE, and S. Rahman, Fellow, IEEE Virginia Tech – Advanced Research Institute, Arlington, VA 22203
units (PMU), and some services, e.g., wide area monitoring,
Abstract— Design of an effective premises area network requires control and protection. The high bandwidth and low latency Virginia Tech – Advanced Researchtechnology. Institute, Arlington, VA 22203requirements for WAN. NAN extends a shorter choosing an appropriate communication The are important objective of this paper is to compare mostly used communication distance than WAN. It is the neighborhood area network technologies in the premises area network in terms of their architecture which connects several premises networks within latency, throughput, reliability, power consumption and a neighborhood area via smart meters. NAN is the bridge implement cost. The aimed communication technologies include between WAN and premises area network. The coverage area wireless, i.e., ZigBee and Wi-Fi, wired, i.e., Ethernet. The selected and bandwidth requirement for NAN based on different sizes communication technologies are simulated in OPNET for two communication schemes, i.e., Always-on and Turn-on-in-loop. By of deployment area and are generally located between the summarizing performances of each communication technology, requirements of the premises network and WAN. The premises this paper gives the conclusion for choosing communication network is the end-use customer’s network architecture. The technology and scheme for a home energy management system in premise area networks can be categorized as home area a premises area network. network (HAN), building area network (BAN) and industrial
Index Terms- Smart grid, premises area network, home energy management system, OPNET.
I. INTRODUCTION
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OWADAYS, the electric power grid is undergoing a significant transition from traditional keeping balance between demand and supply into an intelligent, reliable, and automatic grid which is called the smart grid [1]. In the smart grid, lots of services including smart metering, demand response, load management, distributed generation, real-time pricing and substation automation can be achieved by implementing communication technologies into the power system. The key for realizing the cooperation is appropriate choosing communication technologies and designing communication networks, which provide bidirectional end-toend data communications in the smart grid [2]. Communication networks in the smart grid, according to their coverage, can be divided into three types: wide area network (WAN), neighborhood area network (NAN) and the premises area network. The WAN is the network architecture at the utility’s side. It contains the backbone network and the backhaul network. The backbone network connects the utility backbone and substations; the backhaul network provides the broadband connection between WAN and NAN. WAN provides the management of various devices, e.g., phasor measurement This work was supported in part by the U.S. National Science Foundation under Grant ECCS-1232076. B. Desong, M. Kuzlu, M. Pipattanasomporn and S. Rahman are with Virginia Tech – Advanced Research Institute, Arlington, VA 22203 USA (e-mail:
area network (IAN), depending on the environment, i.e., residential, business, and industrial. The premises network is the most basic element in the whole smart grid communication network. It plays an important role within the whole network. It provides communication access to appliances such as air conditioner (AC), water heater, electric vehicle (EV) charger, etc. It is hard to realize the smart grid without appropriate designing premises network. For communication requirements in a premises area network, there is no great need for a high band-width and low latency. The most important network requirements are low power consumption and low implement cost. This paper goes to discuss various communication technologies for home energy management (HEM) applications in HAN by taking into account the latency, reliability, throughput, power consumption and implement cost. Applications, e.g., HEM system, metering, demand response, etc., of the premises are network in HAN environment are discussed in [3, 4, 5]. In [6], the authors compare different communication technologies (i.e., FiberOptic, DSL, Coaxial Cable, PLC, ZigBee, Wi-Fi, Ethernet, and etc.) and assess their suitability for deployment to serve various smart grid applications. In [7], the authors provide a contemporary look at the current state of the art in smart grid communications as well as to discuss the still-open research issues in this area. In [8], the authors overview the issues related to the smart grid architecture from the perspective of
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potential applications and the communications requirements needed to ensure performance, flexible operation, reliability and economics. In [9], the authors present a ZigBee wireless sensor network simulation in OPNET, while, in [10], the authors propose energy efficient cluster tree architecture for home area network using ZigBee. In literature, it is limited the comparison of communication technologies which are suitable for the premises area network in OPNET. In this paper, popular communication technologies for HA, i.e., ZigBee, Wi-Fi and Ethernet, are discussed and simulated in OPNET in two communication schemes, i.e., Always-on and Turn-on-in-loop. Additionally, performances of these technologies are compared in term of the latency, reliability, throughput, power consumption and implement cost. II.
OVERVIEW OF HOME ENERGY MANAGEMENT (HEM) SYSTEM AND ITS ARCHITECTURE
The premises network can be further classified into HAN, BAN and IAN. This section overviews the home energy management (HEM) in a HAN (Home Area Network). To realize all the intelligence and activity in HAN, the HEM is introduced and implemented in a house to enable demand response applications. The HEM provides a homeowner the ability to automatically perform smart load controls based on utility signals, customer’s preference and load priority. Design and implementation of HEM system are discussed in [11, 12, 13]. In [14], the authors show the hardware demonstration of an equivalent system in a lab environment while the authors present a set of algorithms for HEM system [15]. Based on above papers, the brief review of HEM is shown as following: The overall HEM system comprises an HEM unit which provides monitoring and control functionalities for the homeowner, and load controllers that gather electrical consumption of each appliance, such as AC, water heaters, EV, etc. The gateway, i.e., a smart meter, receives a command signal from a utility, which is used as an input for HEM system. The embedded HEM algorithm is responsible for decisionmaking process based on customer preferences to keep the total power consumption less than requested limit. To achieve this task, it sends an ON/OFF command to load controllers at end of the decision-making process. With penetration of using HEM systems, the communication technologies between the HEM unit and load controllers becomes more frequently. The network requirements for HEM systems are summarized in [1]. The HEM system needs low power consumption and low implement cost communication. There are many communication technologies which can meet the HEM communication network requirements, such as the wired, e.g., Ethernet and power line communication (PLC), and wireless, e.g., ZigBee, Wi-Fi, Bluetooth and Z-Wave, communication technologies. In this paper, mostly used wireless (ZigBee and Wi-Fi) and wired (Ethernet), and are discussed in term of their advantages and disadvantages.
III.
VARIOUS COMMUNICATION TECHNOLOGIES AND SCHEMES FOR A HEM SYSTEM
In this section, mostly used wireless, i.e., ZigBee and Wi-Fi, and wired, i.e., Ethernet, communication technologies are discussed in a Home Energy Management System in a premises are network. A. ZigBee ZigBee is a specification for a suite of high level communication protocols used to create personal area networks built from small, low-power digital radios. It is based on an IEEE 802.15.4 standard, and used in applications that require a low data rate, long battery life and secure networking. ZigBee has a defined rate of 250 kbps. It is suitable for periodic or intermittent data transmission from a sensor or input device. ZigBee applications include wireless light switches, electrical meters with in-home-displays, traffic management systems, and other consumer and industrial equipment that require short-range wireless data transfer at relatively low rates. The technology defined by the ZigBee specification is intended to be simpler and less expensive than other wireless premises area networks, such as Wi-Fi. ZigBee networks are secured by 128 bit symmetric encryption keys. In home automation applications, transmission distances range can be up to 100 meters depending on power output and environmental characteristics. Additionally, ZigBee-Pro can extend its ranges up to 1,600 m. Advantages of ZigBee include low power consuming, low implementation cost and security. However, the low processing capability, small memory size and easily being interfered with other devices using same frequency band are major drawbacks of the ZigBee technology. B. Wi-Fi Wi-Fi is a high-speed wireless internet and network communication technology. Its standards based on the IEEE 802.11; and it operates in 2.4 GHz, 3.5GHz and 5 GHz. Generally, Wi-Fi coverage is up to 100 meters with data rates from 2 Mbps to 600 Mbps. Wi-Fi provides reliable, secure and high-speed communications. However, it supports short-range communications, i.e., up to 100 meters. The cost and power consumption of Wi-Fi products are also higher than other shortrange wireless technologies such as ZigBee. C. Ethernet Ethernet is a most popular wired communication technology which is commonly used in the short-range network. It is a family of computer networking technologies for local area networks (LANs). Ethernet was commercially introduced in 1980 and standardized in 1985 as IEEE 802.3. The original 10BASE5 Ethernet used coaxial cable as a shared medium. Later the coaxial cables were replaced by twisted pair and fiber optic links in conjunction with hubs or switches. Data rates were increased from the original 10 Mbps to 100 Gbps. Ethernet is simply chained together with coax cable, so it is an inexpensive technology to implement and conceptually simple. Besides, since Ethernet is wired network, it is noise immunity. These are the advantages of Ethernet. However,
once the network based on Ethernet is placed, it is hard to make changes to the network since Ethernet is wired communication technology. D. Communication schemes for HEM system Communication schemes are designed for implementation of communication technology in a HEM system. It is used to design the communication traffic which can affect the whole network’s latency, throughput and reliability. In this part, two different schemes are designed: Always-on and Turn-on-inloop. 1) Always-on communication scheme Always-on scheme, all elements (HEM unit and load controllers) in the HEM system are turn on all the time. All load controllers send packets which contain their load information to the HEM unit at the same time and continually, i.e., one packet from each load controller in every second. The coordinator receives load information packets consistently. Additionally, it broadcasts a confirmation packet to all load controllers to test the connection or unicasts control signal to certain load controller every one minute. 2) Turn- on-in-loop communication scheme In Turn-on-in-loop scheme, all load controllers are formed a queue/loop. The load controllers either send load information signals to HEM unit or listen to HEM unit. Each load controller only sends the load information once (last 3 or 5 seconds) and listens to HEM unit during the rest of time within one loop (60
seconds). After the HEM unit receives load information packets from every load controller during the loop, it broadcasts confirmation packet. In Turn-on-in-loop scheme, the confirmation packet is also used as the synchronous signal which marks the beginning of next loop. IV.
PERFORMANCE COMPARISON OF THE SELECTED COMMUNICATION TECHNOLOGIES
The communication requirements for HAN include: latency, throughput, reliability, power consumption and implement cost. Before comparing the performances of the selected technologies, the HAN model built in OPNET is introduced. This model refers a single floor house in 1600 square feet (40 x 40) in a premises area network. A. HEM Model The HEM model includes one HEM unit, i.e., the coordinator, and several load controllers, i.e., smart plugs. The coordinator is used as the central controller which collects electrical data including voltage, current, real power, apparent power and power factor, from plugs and sends out control signals. The plug is used to send electrical data to the coordinator and also receive control signals. The plug can be connected by any kinds of electrical appliances, such as water heater, AC, clothes dryer, etc. The proposed model consists of one coordinator and ten plugs.
Fig. 1. HEM model (a. ZigBee, b. Wi-Fi, c. Ethernet)
The HEM system model uses two kinds of information packets: the control signal and electrical data signal. The signal consists of header, trailer and information. It is assumed the packet size is picked as 100 bytes (800 bits). The maximum data rate of this network is the peak data rate when the coordinator broadcasts. The total data rate equals to the sum of the coordinator’s broadcasting data rate (800 * 10 = 8,000 bps) and its information receiving data rate (800 * 10 = 8,000 bps). Therefore, the maximum data rate is 16.000 bps. The ZigBee, WiFi and Ethernet simulation models are built in OPNET and shown in Fig. 1 (a, b and c). The ZigBee model is the simplest one among these three. There are only ten smart plugs and one coordinator without access point and lines. The Wi-Fi model is as same as the ZigBee model except with an access point. In Ethernet model, there are ten plugs marked as APP 1 to APP 10, one
coordinator marked as HEM and one switch. The red lines show the physical links between devices. B. Latency Latency, also named as the End-to-End delay, refers to the time taken for a packet to be transmitted across a network from source to destination. Generally, it contains three kinds of delay: transmission delay, propagation delay and processing delay. The transmission delay is the amount of time required to push all of the packet’s bits into the channel. Propagation delay is the amount of time it takes for the head of signal to travel from the sender to the receiver. Processing delay is the amount of time it takes for destination to pick all packets’ bits from channel to its storage/memory. The simulation results in Fig. 2 show the latency of three communication technologies and two schemes for each technology. We can find out the Turn-on-in-loop scheme
always has less latency than Always-on scheme. Using the same communication scheme, Ethernet has the least latency; ZigBee has the most latency. According to [6], all three communication technologies and two communication schemes are acceptable for the premise area network which requires the latency less than minutes.
ZigBee Always-on Wi-Fi Always-on; Ethernet Always-on; Fig. 4. Throughputs of Always-on scheme
ZigBee Always-on; ZigBee Turn-on-in-loop; Wi-Fi Always-on; Wi-Fi Turn-on-in-loop; Ethernet Always-on; Ethernet Turn-on-in-loop; Fig. 2. Simulation results about latency (unit: second)
C. Throughput The Network throughput is the average rate of successful messages delivery over a communication channel. Fig. 3 shows throughputs of Turn-on-in-loop scheme comparing with three communication technologies. During one time-slot, i.e., 3 seconds, there is only one device sending information, either the plug sends 800 bps usage information or the coordination broadcasts 10*800 bps confirmation signals. The results of all three communication technologies are same as expected.
D. Reliability Reliability is a character showing how reliable a communication system can perform data transfers according to the specific requirements. The reliability factor equals to the bits of received data over bits of send data. The most reliable network is the one’s reliability factor equals to 100%. The simulation results show that the Always-on scheme has lower reliability than the Turn-on-in-loop. The reliability of all communication technologies is 100% in Turn-on-in-loop scheme in our simulation environment. Additionally, the reliability of Ethernet and Wi-Fi technologies are almost 100% in Always-on scheme as well. However, high data dropping occurs for ZigBee technology using Always-on scheme. See Fig 5.
Fig. 5. Data dropped using ZigBee (Always-on)
Fig. 3. Throughputs of Turn-on-in-loop scheme
Fig. 4 shows the throughput of Always-on scheme comparing with three communication technologies. Different from Turn-on-in-loop scheme, all plugs send one packet to the coordinator every second, i.e., 10*800 bps, as shown in blue line. A spike occurs, i.e., 16,000 bps, when coordinator broadcasts the control signal to all plugs. The simulation results are same for Wi-Fi and Ethernet technologies as shown in red and blue line respectively. However, data dropping issues occur for ZigBee technology showing with green line.
E. Power consumption The power consumption is used to measure the sum of energy usage of each device within the whole network. It is an important factor for wireless communication technologies. According to [1], Wi-Fi is the most power efficient technology and would be ideally suited to large data exchanging. Unfortunately, its current consumption needs a large battery to supply. At this point, ZigBee can be better solution than WiFi. F. Implement cost The implement cost is the total cost of setting up the network. It includes chip, network switch/access point and cable costs. Table 1 shows the estimation of implement cost for the selected communication technologies. Since Ethernet is a wired communication technology, it needs extra cable and a network switch to connect the end-devices and control the data traffic. Wi-Fi and ZigBee are wireless communication
technologies, which don’t need cabling. However, an extra network access point is required for Wi-Fi to set up a network. G. Impact of number of plugs on communication performance The results obtained from the model with 10 plugs show the performance of three communication technologies in a premises area network consisting of ten plugs in Always-on and Turn-on-in-loop scheme. To see impact of the number of devices on communication performance, the HAN model including 5, 10 and 15 devices are simulated in OPNET for selected communication technologies. All results are
summarized in Table I. According to results, we can conclude the communication performance of Turn-on-in-loop scheme is better than the Always-on scheme in latency and reliability. All the selected communication technologies can meet the latency requirement of the HEM application in premises area network. Moreover, these three technologies can provide 100% reliability in Turn-on-in-loop scheme. Considering power consumption and implement cost which are two important factors in premises area network, ZigBee is the best suitable technology for HAN applications.
TABLE I. SUMMARY OF PERFORMANCE Number of Devices 5 ZigBee
10 15 5
Wi-Fi
10 15 5
Ethernet
10 15
Communication Schemes
Latency
Throughput
Reliability
Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop Always-on Turn-on-in-loop
1.0e(-2) 1.0e(-3) 1.0e(-2) 1.0e(-3) 1.0e(-2) 1.0e(-3) 1.0e(-3) 1.0e(-4) 1.0e(-3) 1.0e(-4) 1.0e(-3) 1.0e(-4) 1.0e(-3) 1.0e(-4) 1.0e(-3) 1.0e(-4) 1.0e(-3) 1.0e(-4)
high low high low high low high low high low high low high low high low high low
100% 100% >99.95183% 100% >99.07471% 100% 100% 100% 100% 100% >99.94505% 100% 100% 100% 100% 100% 100% 100%
V.
CONCLUSIONS
This paper compares mostly used wired and wireless communication technologies and identifies their suitability for Home Energy Management (HEM) Systems in a premises area network in OPNET communication simulation platform. For the premise area network, main communication requirements are the reliability, low power consumption and the low implement cost. As wireless technologies provide lower installation cost, more rapid deployment, higher mobility and flexibility than its wired counterparts, wireless technologies are recommended in most of the HEM systems. ZigBee is the most suitable communication technology because of its low power consumption and low implement cost for HEM system in Turnon-in-loop communication scheme which is commonly used in premises network. It is expected that this paper will benefit researchers and engineers working in related fields by providing an insight into communication technologies that can be used in the premises area network. REFERENCE [1]
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N/A
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$20 - $50
$1 / meter
$20 - $50
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