Evaluation of Wireless Home Automation Technologies

A. J. Dinusha Rathnayaka, Vidyasagar M. Potdar Digital Ecosystems and Business Intelligence Institute

Curtin University of Technology Perth, Western Australia

abekoon.rathnayaka@postgrad.curtin.edu.au, v.potdar@curtin.edu.au

Samitha J. Kuruppu Digital Ecosystems and Business Intelligence Institute

Curtin University of Technology Perth, Western Australia

samithajk@gmail.com

AbstractIntroduction of Wireless Home Automation (WHA) has become a positive inspiration to the new home and renovation projects, as it increases the quality of life and comfort of the inhabitants, simultaneously facilitating energy conservation and environmental sustainability. Generally WHA networks comprise of wireless embedded sensors and actuators that intelligently interconnect with each other through a suitable wireless architecture. Many wireless technologies have been emerged recently targeting WHA, hence selecting the optimal technology is challenging. In this article, we present an evaluation of these emerging wireless technologies and discuss their suitability for smart home networks.

Keywords- wireless home automation; wireless technologies;

I. INTRODUCTION HA [1] concept is an emerging vision in modern era,

which offers efficient home management system with convenience, comfort, energy efficiency and security. Home automation is defined as the introduction of technology within the home to enhance the quality of life of its occupants, through the provision of different services such as telehealth, multimedia entertainment and energy conservation [2]. Conservative home automation solutions are mostly based on power line or wired communication technologies. These are complex, expensive, inflexible, and involved with time-consuming installations. WHA architectures have become famous in home automation due to numerous advantages such as plug and play nature, flexibility, interoperability and cost effectiveness. In general, WHA networks are comprised of smart devices, mainly sensors and actuators, which communicate with each other directly or via a centralized server (Fig. 1) to achieve defined automation functionalities. However some established wireless standards [3] such as Wireless Wide Area Network (WWAN) and Wireless Local Area Network (WLAN), Code Division Multiple Access (CDMA2000), and Wideband CDMA (WCDMA), have become unfeasible to use in low power smart devices due to their high power consumption. Several organizations have developed wireless technologies focusing WHA based on different architectures and principles. Fig. 2 illustrates the published official symbols of most of the existing wireless solutions.

According to the literature, there are considerable amount of articles that discuss the existing WHA technologies. However none of them compare all the protocols that we

Figure 1. Centralized HA-embedded area

(UWB)

Figure 2. Wireless Solutions Logos

discuss in this article; those protocols are ZigBee[4], Z-Wave[5], Bluetooth [6], 6LoWPAN[7], Insteon [8], Wavenis[9], UWB [10] Wi-Fi[11], and EnOcean[12].

The rest of the paper is organized as follows; section II illustrates main applications of WHA and benefits it provides to the inhabitants as well as to the community. Section III evaluates existing WHA solutions and section IV draws concluding remarks.

II. APPLICATIONS AND BENIFITS OF WHA WHA concept has been incorporated immensely to the

new home and renovation projects due to the better improvements it provides in many domestic applications.

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ISBN: 978-1-4577-0872-5 (c) 2011 IEEE 76

A. Applications of HA In this section we illustrate some of the many

applications that home automation offers. 1) Light control:

Intelligently control the behaviour of the lights according to the presence of the inhabitants. The lights are automatically switched-off when the unit is unattended and automatically dimmed based on the natural light during the daytime.

2) HVAC control: This includes; A/C control, that automatically switches on the AC or increase the cooling intensity specified duration before the scheduled workers arrive to the unit, reduces the cooling level or switched off the AC when the unit is unattended and control the cooling level based on the temperature level inside the unit. Automated ventilation system, which will be switched on to replenish clean air based on temperature, moisture, smoke, heat, dust, or carbon dioxide level in the unit.

3) Smart surveillance: Intelligent surveillance system records activities in the house and enables the authorities to remotely monitor.

4) Smart door lock and automated security system: When an access event occurs, the door open sensor informs the actuator to initiate an email, text message, or phone call to the authority. The door will be automatically locked after a predefined time period, when a person enters or leaves the premises.

5) Appliance Control: If the electrical appliances such as televisions, radios, are in running mode when the unit is unoccupied, the control point will forward requests to automatically switch-off the appliances.

6) Smart water supply and irrigation: Sensors are located to measure rainfall and moisture and automatically adjust the amount of water supplied for irrigation.

7) Smart metering: Smart metering with display gives detailed information about the electricity usage patterns, energy consumption information etc. It also communicate with the utility provider, giving information such as how much electricity units consumed and power outages and receiving information such as tariff involved.

8) Smart Applications and energy regulation: Smart Applications regulate the energy usage. Smart

algorithms can be configured with different regulation schemes such as activating the devices according to the changing energy-rate information, restricting the usage duration of certain appliances, etc. For example, by using a service application, the running time of the dish washer can be delayed avoiding peak hours which the electricity toll is higher, unless the user forcibly activates the appliance.

B. Benifits of WHA In this section, we discuss the advantages that the

inhabitants will gain from the WHA-embedded applications.

1) Energy Saving Lower the energy bills Quantify operational energy reduction Displaying the real-time energy consumption and

their cost involved persuades the users to concern on energy efficiency on their actions

2) Improved security and occupant safety Real time surveillance of access activities and

occupancy status of the site and enables the authority to remotely grant or restrict the access

Even if the tenant forgets to lock the door, the door will be automatically locked in predefined period.

Quick detection and dissemination of emergency information; safety threatening abnormal electric conditions such as electric leakages and smokes in appliances will be detected and notified to the occupants quickly.

3) Comfortable and convenient living solution Reduce key management overhead Enjoy the comfort of the home environment,

which is anticipating the tenants arrival and adjusting the temperature appropriately

Saving the occupants time and effort by allowing the automated execution of routine functions such as turning off all lights, activating the security systems, setting the thermostat to economy mode when the occupants retire for the night.

Improved stylish multimedia support , allowing the tenants to enjoy home theatre moment by enabling the dim lights, closed curtains, turned on TV and DVD player, and mute phone etc. all with just touching a key of the mobile.

4) Reduced equipment maintenance, operational costs and increased lifetime of the equipments

5) Positive environmental effects Save scarce energy resources (reduce diesel usage,

hence saves natural petroleum reserves) Reduce greenhouse gas (CO2, CO) emissions and

pollutants

III. EVALUATION OF WIRELESS TECHNOLOGIES In this section, we evaluate the wireless technologies; Bluetooth, ZigBee, Z-Wave, EnOcean 6LoWPAN, Insteon, Wavenis, UWB and Wi-Fi, based on the different criteria; radio parameters, power consumption, security, error control, network size, communication range, and protocols logistic (Table. 1).

A. Radio Parameters Zigbee/6LoWPN functions in three license free bands at

2.4 GHz, 915 MHz (North America) and 868 MHz (Europe), while maintaining number of RF channels 16, 10 and 1 and maximum data rates of 250, 40 and 20 Kbps respectively. The modulation methods differ according to

5th IEEE International Conference on Digital Ecosystems and Technologies (IEEE DEST 2011), 31 May -3 June 2011, Daejeon, Korea

ISBN: 978-1-4577-0872-5 (c) 2011 IEEE 77

TABLE I. COMPARISON OF EMERGING WIRELESS SOLUTIONS

the used band, which Offset Quadrature Phase Shift Keying (O-QPSK) for 2.4 GHz band and Binary Phase Shift Keying (BPSK) for 868 and 915 MHz bands. The same spreading technique, Direct Sequence Spread Spectrum (DSSS) is used in all the bands.

Z-Wave on the other hand, mainly operates in 868 MHz (Europe), 908 MHz (United States), and 921.42MHz (Australia) bands and latest version of Z-Wave (400 series) supports the 2.4 GHz. These bands allow 9.6, 40 and 200 Kb/s data rates respectively using Frequency Shift Keying (FSK) modulation schemes.

EnOcean, which has solar power and push button driven sensors, operates at 868.3 MHz, using Amplitude Shift Keying (ASK) modulation with data rate of 120 Kbit/s.

Unlike all other protocols, INSTEON network topology contains RF and power line links, which devices can be RF-only or power-line only, or support both. INSTEON operates in 904 MHz range, which allows 38.4 kbps data rate using FSK modulation.

Wavenis typically operates 433 MHz (Asia), 868MHz (Europe), and 915 MHz (United States) bands, which offers the typical data rate of 19.2kbps and maximum and minimum data rate figures are 4.8 kb/s and 100 kb/s respectively. Data modulation is done using Gaussian FSK (GFSK) with fast frequency-hopping spread spectrum

(FHSS). Bluetooth operates in the 2.4GHz band with adaptive frequency hopping. The specifications relevant to WHA are; (i) classic Bluetooth-Basic-Rate / Enhanced-Rate (BR/EDR) specification, and (ii) Bluetooth-low-energy technology. Basic Rate (BR) employs a GFSK modulation scheme and Enhanced Data Rate (EDR) adds two additional Phase-shift Keying (PSK) modulation schemes namely Differential encoded Quaternary PSK (DQPSK) and Differential encoded PSK (8DPSK). This increases the symbol rate from 1MBps to 2 and 3 Mbps. Bluetooth-low-energy technology uses GFSK with symbol rate of 1Mbps.

Wi-Fi operates in 2.4GHz band uses DSSS (802.11), complementary code keying (CCK, 802.11b), or OFDM modulation (802.11a/g) with 54Mbs data rate.

UWB uses Multiband-OFDM Alliance (MB-OFDM) and DS-CDMA UWB. The multiband method takes 7.5 GHz of unlicensed UWB spectrum and split it into 15 frequency channels that remain between 500MHz and 700MHz.UWB uses BPSK and QPSK with110 Mb/s.

2.4 GHz ISM (Industrial, Scientific, and Medical) band is unlicensed in most countries and offers communication medium for most wireless technologies. The technologies like Bluetooth, ZigBee, Z-Wave, 6LoWPAN, and Wi-Fi operates in 2.4 GHz range. However some of the domestic devices such as microwave ovens, codeless phones, wireless

Protocol Zigbee Z-Wave (Zensys Corp)

EnOcean UWB Bluetooth Insteon (SmartLabs, Inc)

Wavenis (Coronis System)

Wi-Fi 6LoWPN

IEEE Standard

802.15.4 _ _ 802.15.3a *

802.15.1 _ _ 802.11a/b/g 802.15.4

Frequency Band

2.4 GHz, 915 MHz 868 MHz

868/908MHz 2.4 GHz (400 series only)

868 MHz 3.1-10.6 GHz

2.4 GHz 904 MHz 433 /868/ 915

2.4 GHz; 5 GHz

2.4 GHz, 915 MHz 868 MHz

Data Rate 20/40/250 Kb/s

9.6Kbps/40Kbps, 200 kb/s

125 kbit/s

110 Mb/s 1 Mb/s 38.4 Kb/s 4.8/19.2/100

54 Mb/s 20/40/250 Kb/s

Modulation BPSK/BPSK/ O-QPSK

FSK /GFSK ASK BPSK, QPSK

GFSK FSK GFSK/PSK B/QPSK, COFDM, QAM

BPSK/BPSK/ O-QPSK

Spreading DSSS No No DS-UWB, MB-OFDM

FHSS No FHSS DSSS, CCK, OFDM

DSSS

Communication Range(m)

10-100 30 (in) 100 (out )

30 (in)300(out )

10 10 45 (out ) 200 (in) 1000 (out )

100 10-100

Security AES

AES-128 Basic

AES E0 Stream AES-128

Rolling codes, public-key

3 DES 128AES

RC4 Stream / AES Block

AES

Error Control/ Reliability

16-bit CRC, ACK, CSMA-CA

8-bit CRC, ACK, CSMA-CA

- 32-bit CRC CSMA -CA

16 -bit CRC

8-bit checksums

BCH (32,21) FEC

32-bit CRC 16-bit CRC, CSMA-CA, ACK

Network Size

64000 232 232 8 8 256 NA 2007 264

Internet connection

Gateway Required

Gateway Required

Gateway Required

Gateway Required

Gateway Required

Gateway Required

Gateway Required

Gateway Required

Gateway NOT required

Logistic Standard Proprietary Proprietary

Standard Standard Proprietary Proprietary Standard Standard

5th IEEE International Conference on Digital Ecosystems and Technologies (IEEE DEST 2011), 31 May -3 June 2011, Daejeon, Korea

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TABLE II. TRANSMIT (TX) AND RECEIVE (RX) POWER OF ICS

TABLE III. POWER CONSMPTION OF DIFFERENT ICS

LAN also operate in the same band, hence there is a possibility for interferences with the automation networks. Therefore an interference avoidance method plays vital role in such technologies. The interference avoidance technique should be capable to analyse the available channels and reforms the network in least interfered channel, in case of severe interferences. On the other hand, INSTEON, Wavenis, UWB and most common Z-Wave series, operate in a single channel in sub gigahertz bands, hence interference avoidance techniques are not required. This makes the hardware implementation is easier. Data rate is also an important factor, which data transmission at a higher data rate allows shutting down the transmitter and receiver frequently. This saves significant amount of power. Higher data rates at a specified power level means theres fewer energy per transmitted bit, which typically means reduced range. Hence special mechanisms are required to improve range, while negotiating on the battery life. If we compare the modulation schemes supported by different technologies, the PSK schemes demonstrate better signal to noise ratio than ASK and FSK. Operating with FHSS spreading technique gives higher tolerance to the interference than DSSS, hence suitable in noisy industrial environments with high level of interferences. In contrast, DSSS supports higher data rate than FHSS.

B. Power Consumption The energy saving is one of the main reasons for the emergence of smart home automation concept. Most wireless autonomous devices are usually battery-powered. Therefore its essential to manage the smart devices to best utilize the scarce power resources over long time. Some of the techniques employed to reduce power consumption includes; Ability to enable sleep mode: The device is shutdown

(sleep mode) when not transmitting or receiving. Keep low duty cycle: Equation. 1, Duty cycle

(Tduty_cycle) refers to the devices active time (transmission or reception time: Ttx/rx) as a fraction of the time gap between activities (total cycle time between transmission and reception: Tcycle).

cycle

rxtxcycleduty T

TT /_ (1) With low duty cycles, the smart node is active for a small time period, making power optimization. This can be achieved using short transmission or reception time and long time interval between transmission and reception. For example, IPv6 (6LoWPN) uses maximum transmission unit (MTU) to be higher than 1280 bytes in length. This is significantly longer than the IEEE802.15.4's standard packet size of 127 octets. As a result, the transmissions become short and thereby reduce power consumption. Optimal modulation scheme: The modulation

schemes like BPSK for 868/915 MHz and O-QPSK for 2400 MHz reduce power utilization by making a peak-to-average power ratio of one.

In rapidly evolving RF market, many leading IC manufacturers publish their hardware platforms integrating with different technologies. To evaluate the power usage of wireless technologies, we consider those technology enabled hardware ICs. (Table 2, Figure 3). Accordingly, most of the solutions can be applied to WHA networks except UWB and WiFi. Both UWB and WiFi may be not very feasible for battery powered sensing devices in WHA networks due to their high power consumptions. UWB and WiFi are more

Technology Manufacturer Part Number

Supply Voltage (V)

TX current (mA)

RX current (mA)

TX power (mW)

RX power (mW)

Zigbee TI (Texas Instrument) CC2420 Transceiver 3 17.4 18.8 52.2 56.4 Zigbee

TI CC243x System on

Chip (SoC) 3 25 27 75 81 Bluetooth TI CC2540 SoC 3 24 19.6 72 58.8 Bluetooth Cambridge Silicon Radio Bluecore2 1.8 57 47 102.6 84.6

Zwave Zensys ZW0201 3 36 23 108 69 UWB Freescale XS112 3.3 227 227 749.1 749.1 WiFi Conexant CX53112 3.3 219 215 722.7 709.5

EnOcean EnOcean Dolphin EO3000I 2.5 0 23 Not given 57.5 Wavenis Coronis Systems Wavenis SoC 3 Not given 17 Not given 51

5th IEEE International Conference on Digital Ecosystems and Technologies (IEEE DEST 2011), 31 May -3 June 2011, Daejeon, Korea

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suitable implementations like video surveillance, due to its high bandwidth (data rate) and lower normalized energy consumption (Energy efficiency based on bit rate). Unlike others technologies, EnOcean exhibits battery-less feature, which the devices are solar powered or push button based. EnOcean is a cost effective and environment-friendly concept in regions featured with high solar radiation all over the year.

C. Protocolss Logistic ZigBee, WiFi, 6LoWPN, and UWB are open, publicly

accessible standards whereas Z-Wave, INSTEON, Wavenis, EnOcean are proprietary. Since proprietary solutionis are owned by single vendor, the industry support from the semiconductor manufacturers is not available as with standard solutions. Standard technologies offer cost-effective common platforms and the buyers have a range of option to select the product manufacturer.

D. Security Secure network is an important feature in the smart

home to protect sensitive information. Secure protocol is necessary to protect critical monitoring and control signals, and also to eliminate undue interferences in the data transmission and reception. Therefore security mechanisms play a critical role in technology selection. With E0 stream cipher algorithm [13], the authentication key exchange is via a simple secure pairing method, employing Elliptic Curve Diffe Hellman public key. Digital Encryption Standard (DES) [14] is a symmetric block cipher with 64-bit block size with 56-bit key, while more secure 3DES encrypts data three times, resulting a cumulative key size of 112-168 bits. Advanced Encryption Algorithm (AES) [14], a symmetric key encryption algorithm, offers three key sizes: 128-, 192-, or 256-bit encryption key. When we talk about the security methods of wireless solutions, Bluetooth performs encryption using E0 algorithm (Bluetooth-BR/EDR), and 128bit AES (Bluetooth low-energy). The Z-Wave200/300 series chips do not support security, the 400 series chip offer 128-bit AES encryption. WiFi, UWB and Zigbee use AES block ciphers and Wavenis utilizes 3-DES in addition to AES. INSTEON complete long messages can be embedded with encrypted payloads, which probable encryption methods include rolling-code, public-key, and managed-key, algorithms. EnOcean still uses basic security mechanism [18], which a fixed 32 bit ID is added to transmitted telegram, and advanced security mechanisms such as rolling code and encryption are still in progress.

E. Error Control Reliable delivery of information is critical in smart home

networks to obtain accurate automation functionality. Error detection and correction enable identification and correction of the corrupted data in unpredictable communication channels. Zigbee, Z-Wave, UWB, WiFi, and Bluetooth use cyclic redundancy check (CRC) [15, 16] to validate the packets. Here a certain number of bits are (checksum) are

appended to the message being transmitted. Different technologies use 16, 8, 32 checksum and higher the checksum, more powerful error controls. UWB and WiFi show the highest CRC error control proficiencies by offering 23 checksum, Zigbee, 6LoWPN and Bluetooth use 16 checksum, and Zwave and Insteon use 8 checksum. To find out that the data was not infected in transmission, the receiver determines whether the check bits agree with the data with a certain degree of probability. If the CRC shows that the packet was not corrupted, ACK will be sent or otherwise the packet is dropped and NACK is transmitted. On the other hand, Wavenis uses Forward Error correction (FEC) with BCH [17] error control block code by adding redundant data to the transmitted information using a predetermined algorithm. Error control features are not incorporated with EnOcean; hence unsuitable for the applications run in noisy communication architectures that have the possibility to introduce errors to the transmitted data.

F. Communication range and Network size The scalability of the WHA network is mainly

dependent on the network size and the communication range supported by different technologies. Certain established technologies like Infrared have become specific to low communication range applications such as appliance remote controllers due to the short ranges they offer. However employing mesh networking can obtain limitless communication range in large scale applications that involves many nodes. But this requires proper positioning of the relay nodes. If we compare the existing technologies, UWB and Bluetooth exhibit lower range of 10 m, hence unsuitable for WHA networks where the devices are located in distant.

When we consider the network size supported by existing protocols, Bluetooth and UWB support only 8 nodes, therefore unsuitable for large scale networks. Z-Wave and Insteon are more suitable for medium sized networks as they support between 200-300 nodes. Zigbee, 6LoWPN and Enocean are the optimal solutions for large scale networks, since they support 64000, 264, and 232 nodes respectively.

G. Connectivity to Internet (Gateway) Gateway is responsible to interface the network solution into an external system such as IP (Internet Protocol) devices. Gateway translates commands and addresses between the network and IP. Unlike all other technologies (except IP-based-Wavenis, IP-based-Zigbee, which are not used commonly), 6LoWPN doesnt require a gateway for Internet connectivity. 6LoWPN forms wireless network over IEEE 802.15.4, carrying packet data using IPv6 as the basic IP format. All other technologies require gateways to connect to internet.

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IV. CONCLUSION The most important goal in introducing WHA to the

homes is to promote the enhanced living pattern of inhabitants, while offering the environmental sustainability. The chosen technology for the WHA must represent a suite of high level communication architecture intended for low-power, small digital radios and also should facilitate cost-effective, reliable, scalable, wirelessly networked management and control. In this article, we compare the features of emerging wireless solutions and conclude that different wireless solutions offer comparative benefits and limitations in different perspectives. Hence the selection of suitable technology should be dependent on the requirements of selected application.

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