Wireless Technologies and Communication

Summary

Wireless technology comprises the hardware, software, and systems that support the transfer of signals, over long or short distances, without the use of electrical conductors or wires. Communications is the transfer of information between a sender and receiver; and wireless communications use wireless technology. Telecommunications, the transfer of messages between a sender and receiver; and data communications, the transfer of data between a sender and receiver, are the two most popular forms of wireless communications.

Definition and Basic Principles

Wireless technology includes wireless networking, wireless telecommunications, and other wireless devices. Wireless networking started in the 1980s with work supported by Bell Labs and resulting in the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, released in 1997. The IEEE 802.11 standard was improved over the years to become a robust wireless data network. Other wireless technologies have also emerged. Examples of wireless network standards introduced over the years include a high-speed metropolitan area standard (the 802.16), various mobile phone standards (such as the 802.16e/802.20), and the remote area access standard 802.22, though their adoption and success has varied. Notably, Bluetooth was introduced as a peer-to-peer home network in 1998 and was given an IEEE 802 designation, the IEEE 802.15, in 2002. Later generations of Bluetooth took the technology much further as wireless communication became increasingly prevalent.

Wireless telecommunications not only includes the popular code-division multiple access (CDMA) and Global System for Mobile communications (GSM) cellular telephone technologies but a vast array of other wireless phone systems as well. These include the two-way phone systems used by businesses, such as a power company; by emergency services, such as a fire department; by the military, such as battlefield communications systems; by public service systems, such as the marine VHF radio; and by individual users, such as ham radio operators. There are many other wireless devices in use as well, including infrared devices such as television controllers, cordless mice, garage-door openers, model-car controllers, and several satellite-type devices, such as the Global Positioning Systems installed in cars.

Background and History

In 1880, the first wireless communication device, the photophone, was developed by Alexander Graham Bell. Guglielmo Marconi, an Italian inventor, proved the feasibility of radio communications by sending and receiving the first radio signal in 1895. By the early 1900s, Marconi and Serbian inventor and engineer Nikola Tesla both claimed to have invented the basics of radio transmissions, and both started companies to support radio transmission. A number of radio phones were developed during the early 1900s, but the first modern analogue mobile phone was developed at Motorola by Dr. Martin Cooper in 1973. By 1979, the first cellular phone network was implemented in Japan, based in part on research at Bell Labs, and since then cellular phone networks have seen explosive growth.

In 1929 the first commercial radio transmission was made from KDKA in Pittsburgh. According to the Federal Communication Commission, there were 15,441 radio stations and 1,758 broadcast television stations in the United States as of March 30, 2021.

Infrared and microwave technology operate at a higher frequency than radio but have nearly as many technology applications. Infrared waves were discovered by British-German astronomer William Herschel in 1800. In the late 1990s, many uses for infrared technology were discovered, including remote controls, wireless mice, connecting printers to computers, and even heating saunas. The development of radar during World War II led to many advances in microwave technology, including the accidental discovery of the microwave oven in 1940. The first high-speed microwave network was begun in 1949, and microwave communications is an important component of network infrastructure. In 1965, Bell Labs astronomers Arno Penzias and Robert Wilson discovered cosmic microwave background (CMB) radiation by accident while using a large horn antenna. CMB is significant in that it is considered “noise leftover from the creation of the universe” and points to strong evidence supporting the Big Bang theory.

How It Works

Wavelength and Antennae. Wireless communications transmit data using sinusoidal waves. The different types of waves can be characterized by their amplitude (the height of half a sine wave), their frequency, how many complete sine waves are in a fixed length, and their phase (the beginning zero point of a sine wave). A popular measure of wireless waves is their hertz (Hz), the number of cycles per second of the wireless wave. For example, radio and television waves are between 10⁷ and 10⁹ Hz, microwaves are between 10¹⁰ and 10¹¹ Hz, and infrared waves are between 10¹³ and 10¹⁴ Hz.

Most wireless transmissions require the use of antennae, which are transducers that convert electrical energy into wave energy, to send and receive electromagnetic waves. There are many types of antennae in use. The simplest radio antenna is the dipole antenna, which consists of two wires running in opposite directions connected to a central feed element. Some antennae, such as parabolic or horn antennae, are designed to collect multiple signals into one stronger signal; while others, such as HRS curtain antennae, use an array of simple elements to produce a stronger signal. Antennae can be large, such as the proposed Square Kilometre Array, or small, such as the antenna contained in a smart credit card. Antennae can be directional or nondirectional, fixed or mobile, and designed for sending, receiving, or both. In the design of antennae, many factors are considered, including gain, efficiency, impedance, polarization, and bandwidth.

Wireless technology and communications fundamentals require an understanding of how analogue and digital information are prepared for transmission, how the transmission actually takes place, and how the receiving equipment converts the delivered data into usable information.

Digitizing and Encoding. Some information that is transmitted by wireless devices starts with a digital representation, such as data stored on a computer, and some starts with analogue representation, such as sound. Preparing digital data for transmission is relatively easy to do. In some cases, nothing is done to the data. In others, a minor transformation is done, such as performing Manchester encoding, while in others a fairly complex encoding scheme is applied, such as performing CDMA encoding. If the data to be sent is analogue, then several options are available. Some analogue data, such as a phone conversation, can simply be modulated onto a carrier wave and sent, as with the old analogue telephone system, but most analogue data needs to be digitized before it is sent. There are several approaches to digitizing data, but most of them, such as pulse-code modulation for voice, involve sampling the analogue data, representing the sample data digitally, and normalizing the data.

Modulation and Multiplexing. When data is transferred from a sender to a receiver over the air, the last step in this process is to modulate the data onto a carrier wave. To modulate analogue data, simply combine the two waves. For digital data, there are a number of modulation techniques in use. The simplest of these are: amplitude-shift keying, using different amplitudes to represent 0/1; frequency-shift keying, using different frequencies to represent 0/1; and phase-shift keying, using different phases to represent 0/1. Other digital-encoding techniques, such as Gaussian minimum-shift keying, are fairly complex.

A single carrier wave often supports multiple channels so that more than one data stream can be sent over a carrier at the same time. This process is called multiplexing. The old analogue phone system used frequency-division multiplexing to carry multiple calls simultaneously. Many digital phone systems use time-division multiplexing, where the digital path is divided into cells, and evenly divided cells create a channel to support multiple paths on one carrier signal. Another popular digital multiplexing technique is code-division multiplexing, in which multiple digital data streams are modified by a code word and then combined into a broader data stream that can be sent over the carrier wave.

Applications and Products

Most of the applications of wireless technology are wireless communications, and the majority of these are mobile phones and wireless networks.

Cellular Phones. Although quite primitive, the first mobile phone was demonstrated by Alexander Graham Bell in 1876. Mobile phones were being used by industry, the military, and government by the 1980s, but they were restricted to a single central antenna. In 1947, Bell Labs introduced the first cellular network architecture, and this has matured into modern cellular phone networks. Cell phones are electronic devices that include a processing unit, a graphics processor, memory, one or more communications chips, and one or more antennae. When operating as a phone, these devices transmit a signal to the nearest cell phone tower, which then forwards it to a controller, which manages multiple cell phone towers. Local calls may be immediately forwarded to the receiver, but for calls at a greater distance, the signal may be transmitted to a satellite or microwave tower and then forwarded to the receiver. Cellular networks derive their name from the fact that each primary cell phone tower creates a cell for phones in range of the tower. Cellular telephone architectures include a process to handle phones being in the range of two towers, and they hand off as a cellular user moves from one tower to another. One of the unique features of cellular phone networks, compared with other wireless communications networks, is its ability to authenticate users and bill them for services.

In the early 2010s, there were two competing cellular phone architectures. In the United States, the main cellular architecture was code-division multiple access (CDMA). The key characteristic of this architecture is its use of code-division multiplexing to send multiple calls on one signal. This method was mainly used for 2G and 3G phones and began to be phased out by the early 2020s. Another popular architecture in the United States was Global System for Mobile (GSM). The most prominent feature of this architecture is that it is an international standard. In fact, worldwide GSM was more popular that CDMA. GSM eventually developed into Enhanced Data rates for GSM Evolution (EDGE). This mobile architecture was a basis for the architecture upgrade known as LTE, or Long-Term Evolution. LTE uses Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) technology, which decentralizes communications and allows cell phone users to be “handed off” from one base station to another with no loss of signal. This method is primarily used in 4G technology. By the early 2020s, 5G technology was in active development and was being rolled out across the United States. Proposed new standards for this technology include Enhanced Mobile Broadband (eMBB), Ultra Reliable Low Latency Communications (URLLC), and Massive Machine Type Communications (mMTC).

Wireless Local Area Networks. Wireless networks went back to the Aloha data network and microwave connectivity of data centers in the 1970s. By 1980, a number of scientists were investigating how wireless technology could be used for local area networks (LANs). Two types of connectivity were developed: peer-to-peer, where pairs of stations make a direct connection; and shared access, where all stations share the media. In 1997, the IEEE 802.11 wireless LAN standard was released, and most shared-media LANs developed after that conformed to this standard. In the IEEE 802.11 shared-access mode, each computer in the network uses an access point to connect to the corporate network and the Internet. Handoffs and connection problems for the IEEE 802.11 are handled much like cellular phones. While the IEEE 802.11 supports peer-to-peer connections, Bluetooth, released in 1998, has become the principle standard for these networks. Bluetooth is a standard often used to connect cameras to computers, thermostats to access points, headsets to stereos, and keys to central locking systems, for example. In recognition of Bluetooth's success as a peer-to-peer network the IEEE introduced the IEEE 802.15 as its version of Bluetooth in 2002.

Remote Controls. Infrared waves have a higher frequency than radio waves, and this requires line-of-sight connectivity for applications. Infrared signals can be generated by a number of sources, including the Sun, but a common way for remote controls is with a diode (which is similar in operation to a light-emitting diode or LED). Many devices are used to collect infrared waves at the receiver, but most of them operate like an antenna. One of the most common applications of infrared technology is for remote controls–the most popular example is the one used with the television. A remote control has a number of buttons so users can send different instructions to a receiving device, which has an infrared antenna (sometimes called an infrared demodulator) and decoding mechanism. For TVs, digital video recorders (DVRs), and the like, a standard protocol, developed by Phillips called RC-5, is used for sending and receiving infrared signals.

In addition to remote controls, infrared-technology applications include peripheral connectivity for personal computers, night-vision systems, medical-imaging applications, military tracking systems, interactive game controllers, and saunas.

Satellite Communications and GPS. Satellite communications developed in both the United States and Russia shortly after the launch of Sputnik in 1957. Most satellite transmissions are in the microwave bands, but some use other electromagnetic wavelengths as well. There are a variety of devices for satellite transmissions, but many of them use an enhanced vacuum tube technology with names such as magnetron and gyrotron. Early satellite antennae were very large but have been greatly reduced in size.

From the beginning of satellite communication, scientists realized that measuring the difference in signals, over time, could be used to detect terrestrial positions. This basic observation has been greatly enhanced over the years to become the GPS that can be used by mobile phones and cars to determine their position on the Earth at any time. GPS uses microwave technology in the 1 to 2 megahertz (MHz) range, and one of its greatest successes has been the development of a number of small antennae for use in cell phones and cars.

Careers and Course Work

Earning a bachelor's degree with a major in electrical engineering, computer engineering, computer science, mathematics, or physics is the way most often selected to prepare for a career in wireless technology and communications. One needs substantial course work in mathematics and physics as a background for this degree. For some positions, such as antenna and infrared heaters design, an engineering background is advisable, while for others, such as developing cell phone applications, a programming background is necessary. For a position involving development of new products, one generally needs a master's or doctorate degree. Those parts of wireless technology related to the construction of devices are generally taught in engineering and physics, while those involved in using and managing wireless communications are usually taught in computer science and mathematics.

There are a wide variety of positions for those seeking careers in wireless technology and communications. Some go into hardware design of mobile wireless devices for companies such as Apple, Intel, and Cisco, while others go to work as wireless network managers for companies such as Verizon and AT&T. Some develop wireless software; still others take jobs in manufacturing to build products such as microwaves and infrared saunas.

Social Context and Future Prospects

While wireless connectivity has improved the ability to communicate, it has also introduced some serious privacy and security issues. Wireless data is easily intercepted and unless encrypted, it is easy for hackers to read and misuse the data. Mobile computing also supports storing data in the cloud on remote servers, and even when the data is encrypted, issues are raised with the owners as to its safety.

Marconi had a dream of a world connected by wireless devices, and that dream became a reality in the twenty-first century. According to the Pew Research Center, 97 percent of all US adult reported they used a cell phone in 2021. Of those, 85 percent used a smartphone. In addition, 77 percent said they also used a desktop or laptop home computer and 53 percent used a tablet computer. An estimated 99 percent of all Americans had some access to a wireless network.

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