Infrared Technology for Smart Home Automation

Introduction
As next-generation electronic information systems evolve, it is critical that all people have access to the information available via these systems. Examples of developing and future information systems include interactive television, touch screen-based information kiosks, and advanced Internet programs. Infrared technology, increasingly present in mainstream applications, holds great potential for enabling people with a variety of disabilities to access a growing list of information resources. Already commonly used in remote control of TVs, VCRs and CD players, infrared technology is also being used and developed for remote control of environmental control systems, personal computers, and talking signs.

For individuals with mobility impairments, the use of infrared or other wireless technology can facilitate the operation of information kiosks, environmental control systems, personal computers and associated peripheral devices. For individuals with visual impairments, infrared or other wireless communication technology can enable users to locate and access talking building directories, street signs, or other assistive navigation devices. For individuals using augmentative and alternative communication (AAC) devices, infrared or other wireless technology can provide an alternate, more portable, more independent means of accessing computers and other electronic information systems.

Wireless Communication
Wireless communication, as the term implies, allows information to be exchanged between two devices without the use of wire or cable. A wireless keyboard sends information to the computer without the use of a keyboard cable; a cellular telephone sends information to another telephone without the use of a telephone cable. Changing television channels, opening and closing a garage door, and transferring a file from one computer to another can all be accomplished using wireless technology. In all such cases, information is being transmitted and received using electromagnetic energy, also referred to as electromagnetic radiation. One of the most familiar sources of electromagnetic radiation is the sun; other common sources include TV and radio signals, light bulbs and microwaves. To provide background information in understanding wireless technology, the electromagnetic spectrum is first presented and some basic terminology defined.
The electromagnetic spectrum classifies electromagnetic energy according to frequency or wavelength (both described below). As shown in Figure 1, the electromagnetic spectrum ranges from energy waves having extremely low frequency (ELF) to energy waves having much higher frequency, such as x-rays.


 
[Figure 1 description: The electromagnetic spectrum is depicted in Figure 1. A horizontal bar represents a range of frequencies from 10 Hertz(cycles per second) to 10 to the 18th power Hertz. Some familiar allocated frequency bands are labeled on the spectrum. Approximate locations are as follows. (Exponential powers of 10 are abbreviated as 10exp.)
10 Hertz: extremely low frequency or ELF.
10exp5 Hertz: AM radio.
10exp8 Hertz: FM radio.
10exp10 Hertz: Television.
10exp11 Hertz: Microwave.
10exp16 Hertz: Infrared (frequency range is below the visible light spectrum).
10exp16 Hertz: Visible Light.
10exp16 Hertz: Ultraviolet (frequency range is above the visible light spectrum).
10exp18 Hertz: X-rays.

A typical electromagnetic wave is depicted in Figure 2, where the vertical axis represents the amplitude or strength of the wave, and the horizontal axis represents time. In relation to electromagnetic energy, frequency is:
1. the number of cycles a wave completes (or the number of times a wave repeats itself) in one second
2. expressed as Hertz (Hz), which equals once cycle per second
3. commonly indicated by prefixes such as
a. Kilo (KHz) one thousand
b. Mega (MHz) one million
c. Giga (GHz) one billion
4. directly related to the amount of information that can be transmitted on the wave



[Figure 2 description: A sine wave is depicted in the graph in Figure 2. The horizontal axis of the graph represents time, and the vertical axis of the graph represents amplitude. One cycle (or one complete sine wave) is labeled on the graph.]



[Figure 3 description: Graphs of three different sine waves are depicted in Figure 3. The horizontal axis, with values ranging from 0 to 1, represents time in seconds. The vertical axis, with values ranging from -1 to 1, represents arbitrary amplitude. The first graph in the figure depicts a sine wave with a frequency of 1 cycle per second. As shown, the energy wave makes a complete cycle from 0 to its maximum positive value, then through to its maximum negative value, then back to 0. The second graph in the figure depicts a sine wave with a frequency of 2 cycles per second. The sine wave therefore makes 2 complete cycles of moving from 0 to its maximum positive value, through to its maximum negative value, and back to 0, in the same time that the wave in the first graph completes 1 cycle. The third graph in the figure depicts a sine wave with a frequency of 3 cycles per second. The sine wave therefore completes 3 full cycles in the same amount of time that the wave in the first graph completes 1 cycle.]
Figure 3 illustrates energy waves completing one cycle, two cycles and three cycles per second. Generally, the higher the range of frequencies (or bandwidth), the more information can be carried per unit of time.
The term wavelength is used almost interchangeably with frequency. In relation to electromagnetic energy, wavelength is:
1. the shortest distance at which the wave pattern fully repeats itself
2. expressed as meters
3. commonly indicated by prefixes such as
a. Kilo (km) 10exp3
b. Milli (mm) 10exp-3
c. Nano (nm) 10exp-9
4. inversely proportional to frequency
Figure 4 depicts an infrared energy wave and a radio energy wave, and illustrates the two different energy wavelengths. As is expected based on the electromagnetic spectrum, the infrared wave is higher frequency and therefore shorter wavelength than the radio wave. Conversely, the radio wave is lower frequency and therefore longer wavelength than the infrared wave. Anyone who has listened to the radio while driving long distances can appreciate that longer wavelength AM radio waves carry further than the shorter wavelength FM radio waves.



[Figure 4 description: Figure 4 depicts a radio frequency energy wave superimposed upon an infrared energy wave, and illustrates the inverse relationship between frequency and wavelength. The infrared energy wave completes nearly 5 and a half cycles in the time that the radio frequency wave completes 2 cycles. The wavelengths of the infrared wave and the radio wave are labeled, and the infrared wavelength is less than half the wavelength of the radio wave.]
Other terms commonly used in describing wireless communication include transmitter, receiver, and transceiver. In any type of wireless technology, information must be sent (or transmitted) by one device and captured (or received) by another device. The transmitter takes its input - a voice or stream of data bits for example, creates an energy wave that contains the information, and sends the wave using an appropriate output device. As an example, a radio transmitter outputs its energy waves using an antenna, while an infrared transmitter uses an infrared light- emitting diode (LED) or laser diode. The electromagnetic energy waves are captured by the receiver, which then processes the waves to retrieve and output the information in its original form. Any wireless device having the circuitry to both transmit and receive energy signals is referred to as a transceiver. Depending on the communication protocol being used, a device may be capable of only transmitting or receiving information at one time, or it may be capable of both transmitting and receiving information at the same time.
The above described terminology is relevant in all forms of wireless communication, regardless of the band of electromagnetic energy (radio, infrared, etc.) being used. Although radio and ultrasound waves have frequent application in wireless communication, the remainder of the presentation/paper is devoted more specifically to infrared (IR) technology. Infrared technology is highlighted because of its increasing presence in mainstream applications, its current and potential usage in disability-related applications, and its advantages over other forms of wireless communication.

Infrared Technology
As depicted in Fig. 1, infrared radiation is the region of the electromagnetic spectrum between microwaves and visible light. In infrared communication an LED transmits the infrared signal as bursts of non-visible light. At the receiving end a photodiode or photoreceptor detects and captures the light pulses, which are then processed to retrieve the information they contain. Some common applications of infrared technology are listed below.
1. Augmentative communication devices
2. Car locking systems
3. Computers
a. Mouse
b. Keyboards
c. Floppy disk drives
d. Printers
4. Emergency response systems
5. Environmental control systems
a. Windows
b. Doors
c. Lights
d. Curtains
e. Beds
f. Radios
6. Headphones
7. Home security systems
8. Navigation systems
9. Signage
10. Telephones
11. TVs, VCRs, CD players, stereos
12. Toys
Infrared technology offers several important advantages as a form of wireless communication. Advantages and disadvantages of IR are first presented, followed by a comparative listing of radio frequency (RF) advantages and disadvantages.

IR Advantages:
1. Low power requirements: therefore ideal for laptops, telephones, personal digital assistants
2. Low circuitry costs: $2-$5 for the entire coding/decoding circuitry
3. Simple circuitry: no special or proprietary hardware is required, can be incorporated into the integrated circuit of a product
4. Higher security: directionality of the beam helps ensure that data isn't leaked or spilled to nearby devices as it's transmitted
5. Portable
6. Few international regulatory constraints: IrDA (Infrared Data Association) functional devices will ideally be usable by international travelers, no matter where they may be
7. High noise immunity: not as likely to have interference from signals from other devices

IR Disadvantages:
1. Line of sight: transmitters and receivers must be almost directly aligned (i.e. able to see each other) to communicate
2. Blocked by common materials: people, walls, plants, etc. can block transmission
3. Short range: performance drops off with longer distances
4. Light, weather sensitive: direct sunlight, rain, fog, dust, pollution can affect transmission
5. Speed: data rate transmission is lower than typical wired transmission