2.

1 HISTORY OF HOME AUTOMATION

Home automation has been around since the world war 1 (1914), in fact,

the television remote (a simple home automation system) was patented in 1893

(Wikipedia, 2009). Since then different home automation systems have evolved with a

sharp rise after the second World War. It's growth has been through various informal

research and designs by technology enthusiasts who want a better way of getting

things done at home without much effort on their part. The systems evolved from one

that can automatically do routine chores like switch on and off security lights, to more

sophisticated ones that can adjust lighting, put the television channel to favourite

station and control doors.

2.2 HOME AUTOMATION SYSTEMS

Home automation systems may designate electronic systems in homes and

residential buildings that make possible the automation of household appliances. The

new stream of home automation systems has developed into a vast one and the current

market is flooded with a flurry of home automation systems and device

manufacturers.

The types of home automation systems based on their control systems are:

1. Individual Control Systems

These types were the first to hit the market in the early years, here each

device like the heater or the air conditioner will have an independent control

dedicated to it.

2. Distributed Control Systems

The main feature of these type of systems is emergency shut-down. With

this system you can preset or change the control parameters of several

similar devices, for example, the thermostat of several air conditioners and

their ON/OFF timings.

3. Central Control Systems

These are computerized systems programmed to handle all functions of

multiple utilities like air conditioning system, home entertainments, doors,

windows, refrigerators and cooking systems, all at the same time regardless

of whether you are at home or away. You can connect to the control system

through telephone or internet from anywhere in the world.

The types of home automation systems based on the carrier mode are:

1. Powerline carrier Systems

The least expensive type of home automation system operates over the

home's existing wiring, or powerline carrier. These can range from X10-

based lamp timers, to more sophisticated systems that require installation by

a trained professional.
 2. Wireless systems

Also available are wireless home automation systems that utilize radio-

frequency technology. They are often used to operate lights, sometimes in

conjunction with a hardwired lighting control system.

3. Hardwired systems

Wired, or hardwired home control systems are the most reliable and

expensive. These systems can operate over high-grade communications

cable such as Category 5 or 5e, or their own proprietary bus cable. That is

why it is best to plan for them when a house is being constructed. Hardwired

systems can perform more tasks at a time and do them quickly and reliably,

making them ideal for larger homes. They can also integrate more systems

in the home, effectively tying together indoor and outdoor lighting, audio

and video equipment, security system, even the heating and cooling system

into one control package that will be easy and intuitive to operate.

4. Internet Protocol control system

Internet Protocol (IP) control automation system uses the internet, gives

each device under its control an Internet Protocol address, and creates a

local area network (LAN) in the home. Hence, the home can be interacted

with over the internet with possibility of live video streaming and real-time

control.

2.3 HOME AUTOMATION STANDARDS

 There are many established industry standards for home automation

systems and are implemented over the various carrier modes ranging from powerline

to wireless. The popular and major standards are INSTEON, European Home

Systems (EHS), ZigBee, KNX, Z-Wave, X10, LonWorks, ONE-NET and Univerasl

Powerline Bus (UPB).

2.3.1 INSTEON standard

INSTEON standard is a dual-band mesh topology employing ac-power

lines and a radio frequency (RF) protocol to communicate with and automate home

electronic devices and appliances, which normally work independently. It is a home

automation networking technology invented by SmartLabs Inc. INSTEON was

developed, based on the X10 model, for control and sensing applications in the home

(Wikipedia, 2009).

INSTEON is designed to enable simple devices to be networked together

using the powerline and/or radio frequency (RF). All INSTEON devices are peers,

meaning each device can transmit, receive, and repeat any message of the INSTEON

protocol, without requiring a master controller or complex routing software.

INSTEON is not only an effective system for connecting lighting switches and loads

without extra wiring, but it also forms the basis for a more sophisticated home

automation network.

The following are the possible applications of INSTEON:

Scene and remote control lighting,

 Security alarm interfaces and sensors,

Home sensors (e.g. water, humidity, temperature),

Access control (e.g. door locks),

Heating, ventilating and air cooling (HVAC) control,

Audio-video control, and

Appliance management.

2.3.2 European Home Systems (EHS) protocol

The European home systems (EHS) protocol was aimed at home

appliances control and communication using power line communication (PLC).

Developed by EHSA (European Home Systems Association) it was merged with two

other protocols to form the KNX protocol, which complies with CENELEC norm EN

50090 standard and had a chance to be a basis for the first open standard for home

and building control (Wikipedia, 2009).

The areas of application of EHS are:

Heating, ventilating and air cooling (HVAC) control,

Scene and remote control lighting, and

Appliance management.
2.3.3 ZigBee standard

ZigBee is a specification for a suite of high level communication protocols

using small, low-power digital radios based on the IEEE 802.15.4-2003 standard for

wireless personal area networks (WPANs), such as wireless headphones connecting

with cell phones via short-range radio. The technology defined by the ZigBee

specification is intended to be simpler and less expensive than other WPANs such as

Bluetooth. ZigBee is targeted at radio frequency (RF) applications that require a low

data rate, long battery life, and secure networking (Wikipedia, 2009).

ZigBee is a low-cost, low-power, wireless mesh networking standard. The

low cost allows the technology to be widely deployed in wireless control and

monitoring applications, the low power-usage allows longer life with smaller

batteries, and the mesh networking provides high reliability and larger range.

ZigBee operates in the industrial, scientific and medical (ISM) radio

bands; 868 MHz in Europe, 915 MHz in the USA and Australia, and 2.4 GHz in most

jurisdictions worldwide. ZigBee chip vendors typically sell integrated radios and

microcontrollers with between 60K and 128K flash memory, such as the Freescale

MC13213, the Ember EM250 and the Texas Instruments CC2430. Radios are also

available as stand-alone to be used with any processor or microcontroller. Generally,

the chip vendors also offer the ZigBee software stack, although independent ones are

also available. The ZigBee Alliance is a group of companies that maintain and publish

the ZigBee standard.

Typical areas of application of ZigBee are:

 Home Entertainment and Control Smart lighting, advanced

temperature control, safety and security, movies and music,

Home Awareness Water sensors, power sensors, smoke and fire

detectors, smart appliances and access sensors,

Mobile Services m-payment, m-monitoring and control, m-

security and access control, m-healthcare and tele-assist,

Commercial Building Energy monitoring, HVAC, lighting,

access control, and

Industrial Plant Process control, asset management,

environmental management, energy management, industrial device

control.

2.3.4 KNX

KNX is a standardised (EN 50090,ISO/IEC 14543), OSI-based network

communications protocol for intelligent buildings. KNX is the successor to, and

convergence of, three previous standards: the European Home Systems Protocol

(EHS), BatiBUS, and the European Installation Bus (EIB). The KNX standard is

administered by the Konnex Association (Wikipedia, 2009).

This standard is based on the communication stack of EIB but enlarged

with the physical layers, configuration modes and application experience of BatiBUS

and EHS.
 KNX defines several physical communication media:

Twisted pair wiring

Powerline networking

Radio

Infrared

Ethernet (also known as EIBnet/IP or KNXnet/IP)

KNX is designed to be independent of any particular hardware platform. A

KNX Device Network can be controlled by anything from an 8-bit microcontroller to

a PC, according to the needs of a particular implementation. The most common form

of installation is over twisted pair medium.

KNX is approved as an open standard to International standard (ISO/IEC

14543-3) European Standard (CENELEC EN 50090 and CEN EN 13321-1) and

China Guo Biao(GB/Z 20965).

KNX has more than 100 members/manufacturers including ABB, Bosch,

Miele & Cie KG, ON Semiconductor, Schneider Electric Industries S.A., Siemens,

Uponor Corporation and Jung.

There are three categories of KNX device:

1. A-mode or "Automatic mode" devices automatically configure

themselves, and are intended to be sold to and installed by the end user.
 2. E-mode or "Easy mode" devices require basic training to install. Their

behaviour is pre-programmed, but has configuration parameters that need

to be tailored to the user's requirements.

3. S-mode or "System mode" devices are used in the creation of bespoke

building automation systems. S-mode devices have no default behaviour,

and must be programmed and installed by specialist technicians.

2.3.5 Z-Wave standard

The Z-wave is a wireless communications proprietary standard designed

for home automation, specifically to remote control applications in residential and

light commercial environments. This technology, which is developed by Sigma

designs' Zensys, uses a low power RF radio embedded or retrofitted into home

electronics devices and systems, such as lighting, home access control, entertainment

systems and household appliances. The technology has been standardized by the Z-

Wave Alliance, an international consortium of manufacturers that oversees

interoperability between Z-Wave products and enabled devices (Wikipedia, 2009).

Z-Wave is a mesh networking technology where each node or device on

the network is capable of sending and receiving control commands through walls or

floors and around household obstacles or radio dead spots that might occur in the

home. Z-Wave devices can work singly or in groups, and can be programmed into

scenes or events that trigger multiple devices, either automatically or via remote

control.

Z-Wave is a low-power wireless technology designed specifically for

remote control applications. Unlike Wi-Fi and other IEEE 802.11-based wireless

LAN systems that are designed primarily for high-bandwidth data flow, the Z-Wave

RF system operates in the sub Gigahertz frequency range and is optimized for low-

overhead commands such as on-off (as in a light switch or an appliance) and raise-

lower (as in a thermostat or volume control), with the ability to include device

metadata in the communications. Because Z-Wave operates apart from the 2.4 GHz

frequency of 802.11 based wireless systems, it is largely impervious to interference

from common household wireless electronics, such as Wi-Fi routers, cordless

telephones and Bluetooth devices that work in the same frequency range. This

freedom from household interference allows for a standardized low-bandwidth

control medium that can be reliable alongside common wireless devices. On other

hand, 2.4 GHz frequency usage allows unlicensed devices usage in most countries;

this is convenient to customers and allows wider technology adoption and reduced

deployment costs. This could be not true for other frequencies and could easily turn

into a strong drawback if licensing is required or frequency is occupied. That's one of

reason why competing 2.4 GHz technologies became so popular.

As a result of its low power consumption and low cost of manufacture, Z-

Wave is easily embedded in consumer electronics products, including battery

operated devices such as remote controls, smoke alarms and security sensors. Z-Wave

is currently supported by over 200 manufacturers worldwide and appears in a broad

range of consumer products in the U.S. and Europe.

Some common applications for Z-Wave include:

Remote Home Control And Management By adding Z-Wave to

 home electronics such as lighting, climate and security systems, it is

possible to control and monitor these household functions via remote

control, based on manual or automated decisions. The control can be

applied to a single device or group of devices, in a single room or zone or

throughout the entire home. One of the benefits of Z-Wave over power

line communication technologies is the ability to function in older houses

lacking a neutral wire. Z-Wave devices can also be monitored and

controlled from outside of the home by way of a gateway that combines

Z-Wave with broadband Internet access.

Energy Conservation Z-Wave is envisioned as a key enabling

technology for energy management in the green home. As an example, Z-

Wave-enabled thermostats are able to raise or lower automatically, based

on commands from Z-Wave enabled daylight sensors. Grouped scene

controls can ensure that unnecessary energy consumption is minimized by

various all-off states for systems throughout the home, such as lighting,

appliances and home entertainment systems.

Home Safety And Security Systems Because Z-Wave can transceive

commands based on real time conditions, and is able to control devices in

intelligent groupings, it allows novel extensions of traditional home

security concepts. As an example, the opening of a Z-Wave enabled door

lock can de-activate a security system and turn on lights when children

arrive home from school, and send a notification to a parent's PC or cell

phone via the Internet. Opening a Z-Wave enabled garage door can
 trigger exterior and interior home lights, while a Z-Wave motion detector

can trigger an outdoor security light and a webcam, which would allow

the end user to monitor the home while away.

Home Entertainment Z-Wave's ability to command multiple devices as

a unified event makes it well suited for home audio and video

applications. For example, a simple "Play DVD" command on the remote

control could turn on the needed components, set them to the correct

inputs and even lower motorized shades and dim the room lights. Z-

Wave's RF technology is also well suited as an evolution of conventional

Infrared (IR) based remote controls for home electronics, as it is not

constrained by IR's line of sight and distance limitations. In January of

2008, Zensys announced a single-chip solution that pairs Z-Wave with IR

control, positioning the technology as an all encompassing solution for

home remote controls.

2.3.6 X10 standard

X10 is an international and open industry standard for communication

among electronic devices used for home automation. It primarily uses power line

wiring for signalling and control, where the signals involve brief radio frequency

bursts representing digital information. X10 was developed in 1975 by Pico

Electronics of Glenrothes, Scotland, in order to allow remote control of home devices

and appliances. It was the first general purpose home automation network technology

and remains the most widely available. Although a number of higher bandwidth

alternatives exist including KNX, INSTEON, BACnet, and LonWorks, X10 remains
popular in the home environment with millions of units in use worldwide, and

inexpensive availability of new components (Wikipedia, 2009).

Packets transmitted using X10 control protocol consist of a four bit house

code followed by one or more four bit unit code, finally followed by a four bit

command.

Table 2.1 : List of X10 four bit commands

Code Function Description

Switch off all devices with the house code indicated in the
0 0 0 0 All Units Off
message
Switches on all lighting devices (with the ability to control
0 0 0 1 All Lights On
brightness)
0 0 1 0 On Switches on a device
0 0 1 1 Off Switches off a device
0 1 0 0 Dim Reduces the light intensity
0 1 0 1 Bright Increases the light intensity
0 1 1 1 Extended Code Extension code
Requests a response from the device(s) with the house code
1 0 0 0 Hail Request
indicated in the message
Hail
1001 Response to the previous command
Acknowledge
1 0 1 x Preset Dim Allows the selection of two predefined levels of light intensity
Response to the Status Request indicating that the device is
1 1 0 1 Status is On
switched on
1 1 1 0 Status is Off Response indicating that the device is switched off
1 1 1 1 Status Request Request requiring the status of a device
2.3.7 LonWorks

LonWorks is a networking platform specifically created to address the

needs of control applications. The platform is built on a protocol created by Echelon

Corporation for networking devices over media such as twisted pair, power lines,

fibre optics, and radio frequency. It is used for the automation of various functions

within buildings such as lighting and HVAC (Heating, ventilating and air

conditioning).

This technology has its origins with chip designs, power line and twisted

pair, signalling technology, routers, network management software, and other

products from Echelon Corporation. Two physical layer signalling technologies,

twisted pair and power line carrier, are typically included in each of the standards

created around the LonWorks technology. The two-wire layer operates at 78 kbit/s

using differential manchester encoding, while the power line achieves either 5.4 or

3.6 kbit/s, depending on frequency. Additionally, the LonWorks platform uses an

affiliated Internet protocol (IP) tunnelling standard ANSI/CEA-852 in use by a

number of manufacturers to connect the devices on previously deployed and new

LonWorks-based networks to IP-aware applications or remote network management

tools. Most LonWorks-based control applications are being implemented with some

sort of IP integration, either at the user interface, application level or in the control

infrastructure. This is accomplished with web services or IP-routing products

available on the market (Wikipedia, 2009).

2.3.8 ONE-NET standard

 ONE-NET is an open-source standard for wireless network designed for

low-cost, low-power (battery operated) control networks for applications such as

home automation, security and monitoring, device control, and sensor networks.

ONE-NET is not tied to any proprietary hardware or software, and can be

implemented with a variety of low-cost off-the-shelf radio transceivers and

microcontrollers from a number of different manufacturers (Wikipedia, 2009).

ONE-NET uses UHF ISM radio transceivers and currently operates in the

868 MHz and 915 MHz frequencies. The ONE-NET standard allows for

implementation on other frequencies, and some work is being done to implement it in

the 400 MHz and 2.4 GHz frequency ranges. It utilizes Wideband FSK (Frequency-

shift keying) to encode data for transmission and it features a dynamic data rate

protocol with a base data rate of 38.4 kbit/s. The specification allows per-node

dynamic data rate configuration for data rates up to 230 kbit/s.

ONE-NET supports star, peer-to-peer, and mesh networking topologies.

Star network topology can be used for lower complexity and cost of peripherals, and

also simplifies encryption key management. In peer-to-peer mode, a master device

configures and authorizes peer-to-peer transactions. The wireless mesh network mode

allows for repeating to cover larger areas or route around dead areas. Outdoor peer-to-

peer range has been measured to over 500 m, indoor peer-to-peer range has been

demonstrated from 60 m to over 100 m, and mesh mode can extend operational range

to several kilometers. Simple, block, and streaming transactions are supported.

Simple transactions typically use message types as defined by the ONE-NET protocol

to exchange sensor data such as temperature or energy consumption, and control data
such as on/off messages. Simple transactions use encryption techniques to avoid

susceptibility to replay attacks. Block transactions can be used to transmit larger

blocks of data than simple messages. Block transactions consist of multiple packets

containing up to 58 bytes per packet. Blocks transactions can transfer up to 65,535

bytes per block. Streaming transactions are similar in format to block transactions but

do not require retransmission of lost data packets.

ONE-NET is optimized for low power consumption such as battery-

powered peripherals. Low-duty-cycle battery-powered ONE-NET devices such as

window sensors, moisture detectors, etc. can achieve a three to five year battery life

with AA or "AAA" alkaline cells. Dynamic power adjustment allows signal

strength info to be used to scale back transmit power to conserve battery power. High

data rates and short packet sizes minimize transceiver on time. Further power

efficiency can be gained utilizing deterministic sleep periods for client devices.

2.3.9 Universal Powerline Bus

The Universal Powerline Bus (UPB) is an industry emerging standard for

communication among devices used for home automation. It uses powerline wiring

for signalling and control.

Household electrical wiring is used to send digital data between UPB

devices. While in the X10 protocol this digital data is encoded onto a 120 KHz carrier

which is transmitted as bursts during the relatively quiet zero crossings of the 50 or 60

Hz AC alternating current waveform, the UPB protocol works differently. The UPB

communication method consists of a series of precisely timed electrical pulses (called

UPB Pulses) that are superimposed on top of the normal AC power waveform (sine

wave). Receiving UPB devices can easily detect and analyse these UPB Pulses and

pull out the encoded digital information from them. UPB Pulses are generated by

charging a capacitor to a high voltage and then discharging that capacitors voltage

into the powerline at a precise time. This quick discharging of the capacitor creates a

large spike (or pulse) on the powerline that is easily detectable by receiving UPB

devices wired large distances away on the same powerline.

UPB controllers range from extremely simple plug-in modules to very

sophisticated whole house home automation controllers. The simplest controllers are

plug-in controllers that are recommended for a moderate amount of switches and

devices as it becomes cumbersome to control a wide range of devices. More

sophisticated controllers can control more units and/or incorporate timers that

perform pre-programmed functions at specific times each day. Units are also available

that use passive infrared motion detectors or photocells to turn lights on and off based

on external conditions. Finally, whole house home automation controllers can be fully

programmed. These systems can execute many different timed events, respond to

external sensors, and execute, with the press of a single button, an entire scene,

turning lights on, establishing brightness levels, and so on.

UPB was developed by PCS Powerline Systems of Northridge, California

and released in 1999. Based on the concept of the ubiquitous X10 standard, UPB has

an improved transmission rate and higher reliability. While X10 without specialised

firewalls has a reported reliability of 70-80%, UPB reportedly has a reliability of

more than 99% (Wikipedia, 2009).

2.4 HOME AUTOMATION IMPLEMENTATION PLATFORMS

Home automation can be implemented over a number of platforms

namely, Powerline, RS232 serial communication, Ethernet, Bluetooth, Infrared and

GSM. Each platform having its own peculiarity and area of application.

2.4.1 Powerline communication

Powerline communication is a system for carrying data on a conductor

also used for electrical power transmission. Though electrical power is transmitted

over high voltage transmission lines, distributed over medium voltage and used inside

buildings at lower voltages, powerline communication can be applied at each stage.

All powerline communication systems operate by impressing a modulated

carrier signal on the wiring system. Different types of powerline communications use

different frequency bands, depending on the signal transmission characteristics of the

power wiring used. Since the power wiring system was originally intended for

transmission of alternating current (AC) power, in conventional use, the power wire

circuits have only a limited ability to carry higher frequencies. The propagation

problem is a limiting factor for each type of powerline communications. Data rates

over a powerline communications system vary widely. Low-frequency (about 100

200 Khz) carriers impressed on high-voltage transmission lines may carry one or two

analog voice circuits, or telemetry and control circuits with an equivalent data rate of

a few hundred bits per second; however, these circuits may be many miles long.
2.4.2 RS232

The RS232 stands for recommended standard number 232. The serial ports

on most computers use a subset of the RS232 standard. The full RS232 standard

specifies a 25-pin "D" connector of which 22 pins are used. Most of these pins are not

needed for normal PC communications, and indeed, most new PCs are equipped with

male D type connectors having only 9 pins, trading off compatibility with the standard

against the use of less costly and more compact connectors.

In RS232, the communicating devices are referred to as Data Terminal

Equipment (DTE) and Data Communication Equipment (DCE). The DTE is an end

instrument that converts user information into signals or reconverts received signals

and uses the male connector. The DTE is the functional unit of a data station that

serves as a data source or a data sink and provides for the data communication control

function to be performed in accordance with link protocol. While the DCE is

communication link control device that provides the clock signal and uses the female

connector. The DTE ends the communication line, whereas the DCE provides a path

for communication. In connecting a DTE device to a DCE a straight pin-for-pin

connection is used. However, to connect two DCEs or DTEs the transmit and receive

lines must be crossed. The DTE is usually a computer or a terminal device and the

DCE is usually a modem.

Figures 2.1 2.3 shows the straight connections while figures 2.4 2.6

illustrate the cross-over cable connections.

Figure 2.1 : Straight cable connection between RS232 DB9 DTE and RS232 DB9 DCE

Figure 2.2 : Straight cable connection between RS232 DB25 DTE and RS232 DB25 DCE
Figure 2.3 : Straight cable connection between RS232 DB9 DTE and RS232 DB25 DCE

Figure 2.4 : Crossover cable connection between DB9 DCE and DB9 DCE
Figure 2.5 : Crossover cable connection between DB25 DCE and DB25 DCE

Figure 2.6 : Crossover cable connection between DB9 DCE and DB9 DCE
2.4.3 Ethernet

Ethernet defines a number of wiring and signalling standards for the

physical connection of two or more devices together. Ethernet was originally based on

the idea of computers communicating over a shared coaxial cable acting as a

broadcast transmission medium. The methods used show some similarities to radio

systems, although there are fundamental differences, such as the fact that it is much

easier to detect collisions in a cable broadcast system than a radio broadcast. The

common cable providing the communication channel was likened to the ether and it

was from this reference that the name "Ethernet" was derived (Wikipedia, 2009).

From this early and comparatively simple concept, Ethernet evolved into the complex

networking technology that today underlies most local area networks. The coaxial

cable was replaced with point-to-point links connected by Ethernet hubs and/or

switches to reduce installation costs, increase reliability, and enable point-to-point

management and troubleshooting. StarLAN was the first step in the evolution of

Ethernet from a coaxial cable bus to a hub-managed, twisted-pair network. The

advent of twisted-pair wiring dramatically lowered installation costs relative to

competing technologies, including the older Ethernet technologies. Through the

physical connection, Ethernet stations communicate by sending each other data

packets, blocks of data that are individually sent and delivered.

Despite the significant changes in Ethernet from a thick coaxial cable bus

running at 10 Mbits/s to point-to-point links running at 1 Gbit/s and above, all

generations of Ethernet (excluding early experimental versions) share the same frame

formats (and hence the same interface for higher layers), and can be readily
interconnected. And due to the ubiquity of Ethernet, the ever-decreasing cost of the

hardware needed to support it, and the reduced panel space needed by twisted pair

Ethernet, most manufacturers now build the functionality of an Ethernet card directly

into computer and laptop motherboards, eliminating the need for installation of a

separate network card.

2.4.4 Bluetooth

Bluetooth is an open wireless protocol for exchanging data over short

distances from fixed and mobile devices, creating personal area networks (PANs). It

was originally conceived as a wireless alternative to RS232 data cables. It can connect

several devices, overcoming problems of synchronization. It is a standard and a

communications protocol primarily designed for low power consumption, with a short

range (power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost

transceiver microchips in each device. Bluetooth makes it possible for devices to

communicate with each other when they are in range. Because the devices use a radio

(broadcast) communications system, they do not have to be in line of sight of each

other.

Bluetooth uses a radio technology called frequency-hopping spread

spectrum, which chops up the data being sent and transmits chunks of it on up to 79

frequencies. In its basic mode, the modulation is Gaussian frequency-shift keying

(GFSK). It can achieve a gross data rate of 1 Mb/s. Bluetooth provides a way to

connect and exchange information between devices such as mobile phones,

telephones, laptops, personal computers, printers, Global Positioning Systems (GPS)

receivers, digital cameras, and video game consoles through a secure, globally
unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz short-range radio

frequency band. The Bluetooth specifications are developed and licensed by the

Bluetooth Special Interest Group (SIG). The Bluetooth SIG consists of companies in

the areas of telecommunication, computing, networking, and consumer electronics

(Wikipedia, 2009).

2.4.5 Infrared

Infrared (IR) radiation is electromagnetic radiation whose wavelength is

longer than that of visible light (400 700 nm), but shorter than that of microwave

radiation . It's wavelength spans between 750nm and 100 m and is employed in

short-range communication among devices that conform to the standards published

by the Infrared Data Association (IrDA).

Remote controls and IrDA devices use infrared light-emitting diodes

(LEDs) to emit infrared radiation which is focused by a plastic lens into a narrow

beam. The beam is modulated, i.e. switched on and off, to encode the data. The

receiver uses a silicon photodiode to convert the infrared radiation to an electric

current. It responds only to the rapidly pulsing signal created by the transmitter, and

filters out slowly changing infrared radiation from ambient light. Infrared

communications are useful for indoor use in areas of high population density. IR does

not penetrate walls and so does not interfere with other devices in adjoining rooms.

Infrared is the most common way for remote controls to command appliances.

2.4.6 GSM
GSM which stands for Global System for Mobile Communication, is the
most popular standard for mobile phone communication in the world. It is used by

over three billion people across more than 212 countries and territories (Wikipedia,

2009).

GSM basically provides voice call and short message service (SMS). It

operates as a cellular network that mobile phones connect to by trying to search for

cells in their immediate vicinity. The modulation used in GSM is Gaussian minimum-

shift keying (GMSK), a kind of continuous-phase frequency shift keying. In GMSK,

the signal to be modulated onto the carrier is first smoothed with a Gaussian low-pass

filter prior to being fed to a frequency modulator, which greatly reduces the

interference to neighbouring channels (adjacent channel interference). GSM networks

operate in the 900 MHz or 1800MHz frequency bands in most countries of the world

except in few countries like USA and Canada where 850 and 1900 MHz bands are

used as the 900 and 1800 MHz bands were already allocated. The GSM technology

uses a 200 Khz radio frequency channels that are time division multiplexed to enable

up to eight users to access each carrier.

2.4.7 Microcontroller

A microcontroller is an inexpensive single-chip computer. Single-chip

computer means that the entire computer system lies within the confines of the

integrated circuit chip (Byte, 2002). The microcontroller on the encapsulated silver of

silicon has features similar to those of our standard personal computer. Its ability to

store and run unique programs makes it extremely versatile, and its ability to perform

maths and logic functions allows it to mimic sophisticated logic and electronic

circuits. Microcontrollers are used in automatically controlled products and devices,

such as automobile engine control systems, remote controls, office machines,

appliances, power tools and toys. Hence, microcontrollers due not function in

isolation, they accept input from one or more devices and provide output to other

devices within a given system. In fact, they are responsible for the intelligence in most

smart devices in the consumer market.

The microcontroller has two general architecture types that define its mode

of operation and design.

2.3.7.1 Von-Neumann architecture

This architecture has a single, common memory space where both program

instructions and data are stored. There is a single data bus which fetches both

instructions and data. And each time the CPU fetches a program instruction it may

have to perform one or more read/write operations to data memory space. It must wait

until these subsequent operations are complete before it can fetch and decode the next

program instruction. The advantage to this architecture lies in its simplicity and

economy. On some Von Neumann machines the program can read from and write to

CPU registers, including the program counter. This can be dangerous as you can point

the processor to memory blocks outside program memory space and careless

processor manipulation can cause errors which require a hard reset.

2.3.7.2 Harvard architecture

This architecture implements separate memory areas for program

instructions and data. There are two or more internal data buses which allow
simultaneous access to both instructions and data. The CPU fetches instructions on
the program memory bus. If the fetched instruction requires an operation on data memory, the

CPU can fetch the next program instruction while it uses the data bus for its data operation.

This speeds up execution time at the cost of more hardware complexity. Most modern

microcontrollers have the harvard architecture.