We live in a connected world without any visible connections. This seeming contradiction describes the wireless communications that make our lives possible. We no longer pause to marvel that we can call, text, send amazing photographs or even stream live video from wherever we may be to anywhere on the planet, connecting with a single person or many thousands of strangers. All with a few taps on small device in our pocket.
This is the reality where our cars, houses and wearables are all talking with one another, and us. We get our email, social media updates and news on smart-phones and tablets; Our entertainment is streamed to our 3D-HD-4K televisions, computers and other screens over our home networks, at the local coffee shop or the airplane cabin cruising at 30,000.
Our roadways, waterways, railways and skyways depend on wireless communications to remain safe, reliable, efficient and operational. The industries that keep our world moving rely on wireless – Oil extraction, refining and transportation; Electricity generation and distribution; Water collection, treatment and distribution; Farming and Agriculture. The list extends to just about anything you can think of. Even the buildings we work in are dependent on wireless communications to keep us from freezing or roasting, to circulating and purifying the air we breathe, and controlling the doors, elevators and lights.
New developments include monitoring babies to help prevent Sudden Infant Death Syndrome (SIDS) and creating electronic pills to diagnose illnesses from inside your body.
Many of us never consider what happens behind the scenes, and often in plain sight, to make all of this possible. Now that we’ve introduced what wireless communications does for us, let’s explore how this is all possible. At its most basic level, a wireless communication system has a transmitter which sends data to a receiver, using sound waves, radio waves, micro waves, light waves or some portion of the electromagnetic spectrum.
Speech was the first “wireless” communication – the voice box and mouth are the transmitter, and the ears are the receivers. For humans, the audio spectrum is in the 300 Hz to 3,400 Hz range. Bats, dogs and other animals can utilize higher frequencies; Elephants and whales can communicate with lower frequencies.
Communicating with visible light was the next major leap, enabling long-distance messaging. Initially this was a simple fire located at the highest point in an area or along a shoreline. For hundreds of years, line-of-sight communications, with distances up to the 10’s of kilometers was the leading-edge messaging technology. The visible light spectrum is in the 400–790 THz range, with white-light being preferred. This was the first use of “free space optical” communications, although it would be a long time before this term was used.
The next development, and the beginnings of our present day wireless communications, came in the early 1900’s with the invention of the radio by Guglielmo Marconi. Direct communications were now possible between the United States and Europe, and all points in between. The value of radio wave communication was truly appreciated when the Titanic was able to radio a distress call before sinking on April 15th, 1912.
This brings us to the modern age of wireless. As with our short history above, we can categorize today’s methods into three main technologies: Acoustical, Light and Radio. We’ll explore these in the context of embedded systems and mobile devices.
In the United States, the radio spectrum is defined as 3 KHz to 300 GHz. Within that range is the “Industrial, Scientific and Medical (ISM) Band” utilizing frequencies from 915 MHz to 5.800 GHz. Devices operating in the ISM band are governed and regulated by the FCC, but are considered “un-licensed” which means considerably less amounts of paperwork, certifications, compliances, and costs.
The most common wireless communications methods include:
- Proprietary / Custom
- Radio / RF
- WiFi (802.11 a/b/n/g)
- ZigBee (802.15.x)
- Cellular (GSM/GPRS)
Proprietary and/or custom solutions are generally used when data and communications security are absolutely required. These have applications in the financial, military and industrial sectors. It’s rare that a commercial product, targeted for mass-market consumers, would require the features of a custom solution. These are also very costly relative to “standard” communication hardware and protocols.
Radio, or RF, has excellent signal capabilities, long range and power usage profiles. The disadvantage is that it also requires a dedicated receiver unit. The amount of data that can be transmitted is mid-range, and the data-rate is low. This would not work with a standard smart-phone. These are most commonly used for animal tracking (e.g., transmitter collars on mountain lions, cattle grazing on a ranch) and ware-house inventory management.
WiFi is the same as used for you office network, home network, computers, smart-phones and the generic “data connection” to the internet. For communications, there needs to be available either an existing network of “open” / public connections, or access with account and password to private or paid connections. Both the amount of data, and the transfer rates are at high. Cost to implement can be on the high side, and power usage will depend greatly on the data rate and amount of data.
ZigBee has advantages of low power and high reliability, but is limited to ~ 350 feet. It does not also directly communicate with smart-phones. This is used primarily for industrial applications such as sensor to monitor temperature or pressure in pipes at an oil refinery. Data rates are low. Cost to implement is also low.
Cellular communications, similar to sending data from your smart-phone, is reliable, secure and can operate nearly anywhere on the planet including underwater. There are readily available GSM/GPRS which have excellent range, high data rates and good power usage. A consideration for using this approach is the cost for transmitting and receiving data. All data will need to pass through a cellular network provider system and an external server / database for relaying communications. The cost per individual communication may be low (e.g., $0.0001 / transaction), but needs to be considered for the overall usage of the application. There may also be per device fees in the $0.50 / month range.
Bluetooth will communicate directly with smart-phones, has a range of up to ~ 500 feet (with Class 1 devices), has robust signal integrity and good power usage profiles. For these reasons, this is a commonly used standard for many consumer products. Cost for implementation is also low relative to other methods.
Other types of communications consist of:
NFC (Near Field Communications) which is the technology behind security card badges, Apple-pay and other digital wallets, US Passport embedded chip information and some credit cards. As the name states, the transmitter and receiver have to be “near” each other in order to exchange information. In this case, this means in direct contact or a few to tens of millimeters. NFC is supported by most major smart-phone manufacturers, is inexpensive, low-power and very secure. It’s main limitation (or prime advantage, depending on the desired application) is communication range.
WiMax – this uses microwaves for communications, and one side is typically in a fixed, permanent location (e.g., a tower). Range is ~ 50Km and data transfer is excellent. Typically used by service providers (Telephone, Internet, TV/Sports/Radio).
Optical – uses light to communicate. This is almost always configured as a “point-to-point” or “one-to-one” communication. Very short range, low data applications like a TV remote can use LEDs or InfaRed (IR) devices. Longer range, very high data systems can use lasers in a “free space optical” link.
Acoustic – uses sound waves to communicate. Low data rate, short range.
Lastly, there is the “Other” category for new types of communications and research which doesn’t really fit into the standard three groups. One novel area that shows promise for short range communications uses brain waves. Another explores the Quantum Mechanics theory of “entanglement”. Similar to this is a quantum-tunnel or “worm-hole” which makes it possible for two distant points to occupy the same space. Yet another is trying to isolate biological energy signatures in single-cell organisms to create a data transmission net. These may seem very futuristic and the imagination of science-fiction authors, but consider how our technology today would seem prior to the discovery of radio waves. Magical!
We’ll explore these, and more in an upcoming article. Please share in the comments below what you think will be the next breakthrough in wireless communications.
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