Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

Infrared Wireless

Perhaps the most widespread wireless system uses infrared light for short-distance data communication. The most ubiquitous example is the wireless remote control on virtually all TV sets, DVD players, and most audio CD stereo systems. This standard feature on most consumer electronic products is so common that it is taken for granted. Infrared has also been used for wireless PANs. Because light travels in straight lines, there must be a clear path from transmitter to receiver for the system to work. Furthermore, light does not penetrate walls, floors, and ceilings, as wireless radio does, so IR LANs are not practical. Wireless PANs, however, are widely used to link nearby laptops, PCs, and PDAs such as Palm Pilots. This section explores the most popular IR wireless systems.

TV Remote Control

Almost every TV set sold these days, regardless of size or cost, has a wireless remote control. Other consumer electronic products have remote controls including VCRs, cable TV converters, CD and DVD players, stereo audio systems, and some ordinary radios. Generic remote controls are available to hook up to any device that you wish to control remotely. All these devices work on the same basic principle. A small handheld battery-powered unit transmits a serial digital code via an IR beam to a receiver that decodes it and carries out the specific action defined by the code. A TV remote control is one of the more sophisticated of these controls, for it requires many codes to perform volume control, channel selection, and other functions.

Fig. 21-5 is a general block diagram of a remote control transmitter. In most modern units, all the circuitry, except perhaps for the IR LED driver transistors, is contained within a single IC. The purpose of the transmitter is to convert a keyboard entry to a serial binary code that is transmitted by IR to the receiver.

The keyboard is a matrix of momentary-contact single-pole single-throw (SPST) pushbuttons. The arrangement shown is organized as eight rows and four columns. The row and column connections are made to a keyboard encoder circuit inside the IC.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

Pulses generated internally are applied to the column lines. When a key is depressed, the pulses from one of the column outputs are connected to one of the row inputs. The encoder circuit converts this input to a unique binary code representing a number for channel selection or some function such as volume control. Some encoders generate as few as 6 bits, and others generate up to 32-bit codes. Also 9- and 10-bit codes are very common.

The serial output is generated by the shift register as data is shifted out. A standard nonreturn to zero (NRZ) serial code is generated. This is usually applied to a serial encoder to generate a standard biphase or Manchester code. Recall that the biphase code provides more reliable transmission and reception because there is a signal change for every 0-to-1 or 1-to-0 transition. The actual bit rate is usually in the 30- to 70-kbps range.

The serial bit stream turns a higher-frequency pulse source off and on according to the code’s binary 1s and 0s. The transmitter IC contains a clock oscillator that runs at a frequency in the 445- to the 510-kHz range. A typical unit runs at 455 kHz, using an external ceramic resonator to set the frequency. The serial data turns the 455-kHz pulses off and on. For example, a binary 1 generates a burst of 16 pulses of 455 kHz, as shown in Fig. 21-6. When a binary 0 occurs in the data train, no pulses are transmitted. The fi gure shows a 6-bit code (011001) with a start pulse. The period T of the 455-kHz pulses is 2.2 µs. The pulse width is set for a duty cycle of about 25 percent, or T/4. If 16 pulses make up a binary 1 interval, that duration is 16 x 2.2, or 35.2, µs. This translates to a code bit rate of 1/35.2 x 10-6 or 28.410 kHz.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

The 455-kHz pulses modulate the IR light source by turning it off and on. The IR source is usually one or more IR LEDs. These are driven by a Darlington transistor pair external to the IC, as shown in Fig. 21-5. Two or more LEDs are used to ensure a sufficient level of IR radiation to the receiver in the TV set. The LED current is usually very high, giving high IR output levels for reliable transmission to the receiver. Some remote units use three LEDs for a wide-angle transmission signal so that a high-amplitude signal will be received regardless of the direction in which the remote is pointed.

An IR receiver is shown in Fig. 21-7. The PIN IR photodiode is mounted on the front of the TV set, where it picks up the IR signal from the transmitter. The received signal is very small despite the fact that the distance between the transmitter and receiver is only 6 to 15 ft on average. Two or more high-gain amplifiers boost the signal level.

Most circuits have some form of automatic gain control (AGC). The incoming pulses are detected, shaped, and converted to the original serial data train. This serial data is then read by the control microcomputer that is usually part of the TV receiver.

The microcontroller is a dedicated microcomputer built into every TV set. A master control program is stored in a ROM. The microcomputer converts inputs from the remote control and front panel controls to output signals that control the various functions in a TV set, such as channel selection and volume control.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

The microcontroller inputs and decodes the incoming signal and then issues output control signals to all other circuits: the PLL frequency synthesizer that controls the TV tuner, the volume control circuits in the audio section, and in the more advanced receivers, chroma and video such as hue, saturation, brightness, and contrast. The microcontroller also generates, sometimes with the help of an external IC, the characters and simple graphics that can be displayed on the screen. Most microcontrollers also contain a built-in clock.

IR controls are still widely used and will continue to be. However, they are gradually being replaced by a radio version based on ZigBee called RF4CE or radiofrequency for consumer electronics. RF4CE remotes have a longer range and do not require line-of-sight orientation. In addition, they add the ability of two-way communications with the controlled device. Some products will use both RF4CE and IR.


Besides remote control, the primary application for IR data communication is in short distance links between computers and other devices. For IR short distance typically means up to 1 m. Under some special conditions, the distance can be extended up to 9 m maximum. And there must be a clear line of sight between transmitter and receiver.

Because many of the short-range radio options, such as Bluetooth and ZigBee, offer better range and other benefits, IR is no longer widely used as wireless technology. However, it may find application in specialized operations where the benefits of IR are important factors.

Fig. 21-8 shows a block diagram of an IR transceiver. It connects to interface circuitry in the PC or other device. The interface is typically a small embedded controller inside the computer or device. The encoder puts the serial digital data from the PC into the proper format for transmission. A high-current bipolar transistor or MOSFET drives one or more IR LEDs. The receiver consists of the PIN diode that picks up the IR light from a nearby transmitter. The signal is amplified and shaped and then sent to the decoder, which recovers the original data. Fig. 21-9 shows the physical arrangement of the transceiver module. It contains the LED and PIN diodes plus the related circuitry. The LED and PIN diode are positioned next to each other, about 0.5 to 1 in apart.

There is a popular system for IR data communication system developed by Hewlett-Packard in the early 1990s. It has since become an international standard that is maintained by the Infrared Data Association (IrDA). The complete interface and system are referred to as IrDA. The systems are designed for the short-range. A typical range is about 1 m.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB
Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

As for data speed, the original standard supported speeds up to 115.2 kbps. Most systems used speeds as low as 2.4 kbps, although 9600 bps was very common. Different versions support speeds of 576 kbps and 1.152 Mbps up to 4 Mbps, which is the most commonly used version of IrDA. Newer versions of the standard support rates of 16 Mbps, 96 Mbps, 512 Mbps, 1 Gbps, 5 Gbps, and 10 Gbps. IrDA is not as widely used as RF technologies.

Radio-Frequency Identification and Near-Field Communications

Another growing wireless technique is a radio-frequency identification (RFID). You can think of it as the wireless version of bar codes. This technology uses thin, inexpensive tags or labels containing passive radio circuits that can be queried by a remote wireless interrogation unit. The tags are attached to any item that is to be monitored, tracked, accessed, located, or otherwise identified. RFID tags are widely used in inventory control, container and parcel shipping, capital equipment, and other asset management, baggage handling, and manufacturing and production line tracking. They are also widely used for automatic toll collection and parking access for vehicles. Other applications for RFID tags are personnel security checking and access, animal tracking, and theft prevention. As technology has developed, prices have dropped and many new applications have been discovered. The basic concept of RFID is illustrated in Fig. 21-10. The tag is a very thin label-like device into which is embedded a simple passive single-chip radio transceiver and antenna.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB
Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

The chip also contains a memory that stores a digital ID code unique to the tagged item. For the item to be identified, it must pass by the interrogation or reader unit, or the reader unit must physically go to a location near the item. Longer-range systems cover a complete building or area. The reader unit sends out a radio signal that may travel from a few inches up to no more than 100 ft or so. The radio signal is strong enough to activate the tag. The tag rectifies and filters the RF signal into the direct current that operates the transceiver. This activates a low-power transmitter that sends a signal back to the interrogator unit along with its embedded ID code. The reader then checks its attached computer, where it notes the presence of the item and may perform other processing tasks associated with the application.

RFID systems operate over the full radio spectrum. Commercial systems have been built to operate from 50 kHz to 2.4 GHz. The most popular ranges are 125 kHz, 13.56 MHz, 902 to 928 MHz, and 2.45 GHz. The 125-kHz and 13.56-MHz units operate only over short distances up to several feet, whereas the 902- to 928- MHz and 2.45-GHz units can operate up to about 100 ft. Most of the tags are passive; i.e., they have no power source of their own. They rely upon the interrogator unit to
supply a large enough RF signal to rectify for dc power. However, some active tages containing small flat batteries are available, and they can operate over a much larger range.

Fig. 21-11 shows a block diagram of a typical 13.56-MHz RFID interrogator unit. A 13.56-MHz crystal oscillator generates the basic RF signal, which is amplified and sent to the antenna. A microcontroller gates the oscillator on for a short time, and then the receiver waits for a response from the tag. The antenna picks up the weak tag signal. The receiver amplifies and demodulates it and then recovers the serial data code. The microcontroller communicates with the attached computer to do whatever processing is needed in the ID process.

Some RFID tag configurations are shown in Fig. 21-12. They consist of a flat spiral inductor and a capacitor that make up a 13.56-MHz tuned circuit that serves as the antenna. The transceiver chip is contained in the black dot on the tag. A block diagram of the circuitry is given in Fig. 21-13. A typical tag is the model MCRF 355/360, a product of Microchip Technology Inc. The resonant circuit picks up the interrogator signal as if it were the induced signal in a transformer secondary rather than an actual received electromagnetic radio wave. When the voltage reaches about 4 Vp-p, the power circuits are activated. The RF is rectified in a voltage multiplier circuit, filtered, and regulated into the direct current that operates the remaining circuits.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB
Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

The unique ID code is stored in an electrically erasable programmable read-only memory (EEPROM) in the tag chip. In this device, the code is 154 bits long. Fig. 21-14 shows the format of the packet sent to the reader. The 9-bit header initiates synchronization at the reader receiver for clock recovery. The customer’s unique ID number is encoded with 13 bytes. The checksum provides for error checking at the reader. The code is stored in the chip by the manufacturer with a contact transmitter that activates the chip and writes the code into memory. The tag chip contains the EEPROM write circuitry that stores the code.

The ID code in EEPROM is read out serially in NRZ data format, which is then converted to a Manchester or biphase signal that is used to modulate the carrier sent back to the reader. See Fig. 21-15. The Manchester code is used so that the clock can be easily recovered from the data in the reader. The data rate is typically 70 kbps. With a bit time of 1/70 x 103 =14.28 µs, it takes 154 x 14.28 µs = 2200 µs, or 2.2 ms, to transmit the 154-bit code.

The modulation used is a form of amplitude modulation called backscatter modulation. The circuitry was shown in Fig. 21-13, and the process is shown in Fig. 21-16. The coil in the external tuned circuit/antenna is tapped. A MOSFET switching transistor is connected to that tap inside the tag. The data to be transmitted is applied to this transistor. When the transistor is off, the carrier is passed to the tuned circuit and sent to the reader, which reads the signal as a binary 1. When the transistor is turned on, a portion of the coil is shorted, making the external tuned circuit resonant at a frequency of 3 to 6 MHz higher than its 13.56-MHz design frequency. This signal is out of the frequency range of the reader, so it receives a much lower-level signal that is interpreted as a binary 0. During the time the transistor is on, the signal is said to be cloaking. With the transistor off, the signal is uncloaked. The cloaking and uncloaking process produce amplitude shift keying (ASK) at the reader receiver. See Fig. 21-16.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB
Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

In some systems, the tag tuned circuit serves as the secondary winding of a transformer where the reader antenna is the primary winding. The binary pulses to be transmitted modify the impedance of the tag antenna, and this, in turn, causes an amplitude shift in the reader. As the tag’s data is read out, the process loads and unloads the secondary winding tag antenna, causing a reflected impedance back into the reader antenna. A typical carrier may have a 100-V peak-to-peak amplitude that will shift by several hundred millivolts as data is being transmitted by the tag. A peak detector recovers the signal.

The most recent new RFID standard is called Gen 2 for the second generation. It is a standard developed by more than 60 companies worldwide. The standard is under the auspices of EPCglobal, the organization that also standardizes the Electronic Product Code (EPC) to be used on all tagged items. The Gen 2 standard operates in the 900- MHz region with different frequencies being used in different countries depending upon the local regulations. The 868-MHz frequency is common in Europe while 915 MHz is common in the United States. The standard uses ASK backscatter and support a 96-bit EPC plus a 32-bit error correction code and a kill command that deactivates a tag after it is read.

A key benefit of the new standard is that it is designed to read multiple tags faster. Tag read rates as high as 1500 tags per second are possible, although in most situations the read rate will be no more than 500 to 1000 tags per second, which is still much faster than the 100 tag per the second maximum imposed by the older standards. The Gen 2 tags are also more robust and can operate reliably in an environment with multiple readers transmitting and receiving simultaneously. The RFID field is still new but growing as tag prices drop and as greater security measures are developed.

Near-Field Communications

One of the newest forms of wireless is a version of RFID called near-field communications (NFC). It is ultrashort-range wireless whose range is rarely more than a few inches. It is a technology used in smart cards and cell phones to pay for purchases or gain admittance to some facilities.

Near field means the near field of a radio wave. As discussed earlier, a radio wave is made up of both electric and magnetic fields. At a distance of about 10 wavelengths or more at the operating frequency, the radio wave behaves just as Maxwell’s equations describe it.

The two fields exchange energy and reinforce each other as it passes from the transmitting antenna to receiving antenna. This is the so-called far-field. At a distance of fewer than 10 wavelengths from the transmitting antenna in the near field, where the individual electric and magnetic fields exist. The electric field is not useful, but the magnetic field is used for short-range communications. The way to imagine NFC is as the magnetic field between the windings of a transformer. The coefficient of coupling is very low because of a large distance between the primary winding (the transmitting antenna) and secondary winding (the receiving antenna). The primary limitation of the near field is that the magnetic field strength drops off at a rate of about 1/d6, where d is the distance. With only low power the range is very limited. The far-field only drops off at a 1/d2 rate. NFC is standardized internationally. The technology is similar to that used in RFID.

It is similar to and compatible with the technology used in smart cards, those credit cards with an internal chip that allow you to pay for something by just passing the card over a point-of-sale (POS) terminal reader.

The standard specifies an operating frequency of 13.56 MHz, the international license band and one of the ISM band Part 15/18 frequencies in the United States. The transfer data rate is 106, 212, or 424 kbps. The speed depends upon the range, which is up to a maximum of 20 cm or about 8 in. In most cases, the actual range will be only a few inches or no more than 10 cm.

The standard also specifies an active and a passive mode of operation. In the active mode, both parties have powered transceivers. This means that each node has a battery or some other power supply. Either unit may initiate a transmission, which is half-duplex with a “listen before transmit” protocol. One of the devices is the initiator, and the other device becomes the target.

In the passive mode, the target is a passive device such as an RFID tag. The tag gets its operational power from the field transmitted by the initiator. It then transmits data back to the initiator by modulating the magnetic field, using backscatter AM.

There are several intended applications for this ultrashort-range technology. The most frequent use is an automatic payment tool such as a smart card. But instead of using a smart card, the NFC transceiver is built into your cell phone. To buy something, you just tap your cell phone on the reader or pass it within an inch or so, and your credit card account is automatically billed. You could use it to buy theater tickets or even to pay for a plane, train, or hotel charge. Some modern smartphones have NFC built-in, but payment with this technology is still not widespread, at the time this is written.

The second most useful application is an automatic gated entry. Passing your cell phone near the reader allows you entry into a building, parking lot, or another controlled area. NFC chips are also expected to be incorporated into the next-generation passports.

Another proposed use is to set up and initiate other forms of wireless. Some short-range wireless modes such as Wi-Fi or Bluetooth require that the two parties desiring a peer-to-peer link first exchange information to set up the correct protocol. It is sometimes called pairing. Putting your cell phone, laptop, or another device next to the device to be connected allows all this protocol setup to be exchanged automatically. After that the two devices then automatically begin talking in the new wireless mode faster and at a longer distance. NFC chips are small and inexpensive, so look for them to be more widely used as further applications are discovered.

Perhaps the newest and most unusual form of wireless is known as ultrawideband (UWB) wireless. There are two basic forms of UWB, the original version based on very narrow impulses and the newer kind based on OFDM. Both spread the signal over a very wide range of spectrum but at a very low signal level, so it does not interfere with other signals operating over those frequencies. Both methods are used, but the newer OFDM version appears to have captured the greatest number of manufacturing companies and applications. Both types of UWB are covered in this section.

Infrared Wireless | Ultra wideband Wireless | Multiband OFDM UWB

The original UWB discovered in the 1960s is known as an impulse, baseband, or carrier wireless. This form of UWB transmits data in the form of very short pulses, typically less than 1 ns. From the Fourier theory discussed in Chap. 12, you know that a fundamental frequency sine wave and many harmonics can represent any pulse train. A UWB signal using very short pulses with a low duty cycle occupies a very wide bandwidth. A UWB signal is defined as having a bandwidth at least 25 percent of the center frequency, or 1.5 GHz minimum. Another definition specifies UWB as occupying more than 500 MHz of spectrum. Fig. 21-17 shows a UWB signal spectrum compared to a standard 30-kHz cell phone channel and a 5-MHz wideband CDMA (spread spectrum) cell phone channel.

The FCC permits UWB in the 3.1- to the 10.6-GHz range. The only other services in this region are satellites, radars, broadband wireless, and wireless networks. UWB equipment spreads its signals over much of that range, but the power level is so low that there is essentially no interference to other services. UWB is like a spread spectrum in that man users can share a single wide bandwidth simultaneously.

A UWB signal starts as a very low duty cycle (less than 1 percent) rectangular pulse stream at some pulse repetition interval (PRI). The pulses are then Gaussian-filtered and differentiated to produce the final pulses to be transmitted. The pulses are applied directly to the antenna (see Fig. 21-18). Known as monocycles, these pulses are not just one cycle of a sine wave. They are shaped by a Gaussian filter. The pulse width sets the center frequency of the signal and the half-power bandwidth. The center frequency is approximately the reciprocal of the pulse width. For a pulse width of 500 ps, the center frequency is 1/500 x 10-12 = 2 GHz.

The serial data to be transmitted is then encoded with a unique pseudorandom code like that used in CDMA. This method effectively “channelizes” the system so that multiple users can share the spectrum but still be individually identified. The coded signal then modulates the pulse train by either PPM or BPSK. Both methods are illustrated in Fig. 21-19. In PPM, the position of the pulse may occur sooner or later in time than a pulse with no modulation. A binary 0 may be represented by an earlier pulse, and a binary 1 as a later pulse, or vice versa. The time shift is small compared to the pulse width. Because of the very small time differences, the timing clock generating the pulses must be very precise and stable, with minimal jitter, to ensure recovery.

In BPSK, the PRI is constant, and the data bits produce a normal pulse for binary0 and a phase-inverted pulse for binary 1.

Multiband OFDM UWB

The newest form of UWB is called multiband OFDM or MB-OFDM UWB. The term multiband is derived from the fact that many OFDM carriers make up the signal. This form of UWB divides the lower end of the assigned spectrum into three 528-MHz-wide channels, as shown in Fig. 21-20. These bands extend from 3.168 to 4.952 GHz. Note the center frequencies of the three bands. Each band is designed to hold an OFDM data signal. There are 128 carriers per band, and each carrier has a bandwidth of 4.125 MHz. Of the bands, 100 actually carry the data while 12 are used as pilot carriers to aid in establishing communications with nearby nodes. The remaining carriers serve as guard bands on either side to prevent interference between the three portions of the spectrum.

The signal to be transmitted is divided up among the carriers, and each is modulated by BPSK or QPSK depending on the data speed selected. In Fig. 21-20 you will see a dashed line that designates the maximum allowed operating power specified by the FCC. It is a very low 241 dBm/MHz, which generally prevents any interference to other services.

The system is designed to permit a wide range of data rates from about 53 to 480 Mbps. The most often mentioned speed is 110 Mbps at a range up to 10 m. A speed of up to 480 Mbps is possible but only at a range of 2 to 3 m.

Implementation of an OFDM UWB transceiver is just like that of any OFDM device. DSP chips are used to create the transmit carriers with the inverse fast Fourier transform (IFFT), and a DSP chip in the receiver uses the FFT for recovery of the data. MB-OFDM UWB radios are usually a single-chip IC containing all functions.

There is no UWB standard. Companies worked for years in an IEEE Task Group to create a single standard to be designated 802.15.3a. No consensus could be reached, so companies went their different ways. The largest group of companies banded together in the WiMedia Alliance to create a standard that most could agree upon. Today the MBOFDM form of UWB is the defacto standard. The WiMedia Alliance maintains this standard.

Advantages and Disadvantages of UWB

UWB offers many benefi ts to radar, imaging, and communication applications:

  1. Superior resolution in radar and imaging.
  2. Immunity to multipath propagation effects.
  3. License-free operation.
  4. No interference to other signals using the same frequency band. UWB signals appear as random noise to conventional radios.
  5. Power-efficient, extremely low-power operation. Peak power levels are in the milliwatt region and average power is in microwatts.
  6. Simple circuitry, most of which can be integrated into standard CMOS.
  7. Potentially low cost.

The primary disadvantage, which is also an advantage, is low power. It severely limits the range of operation. The range can be extended in military radar with higher power levels, but the power level in commercial and consumer applications is severely restricted by the FCC. Typical ranges are from a few inches up to no more than about 100 ft.

Primary Application of UWB

The primary application of impulse UWB to date has been on military radar. The very short pulse widths of electromagnetic energy permit a very fine resolution of target distance and detail. Short pulses also give UWB the ability to penetrate surfaces to see what is behind them. For that reason, UWB is an excellent electronic imaging technique. It is especially effective in seeing through leaves, trees, and foliage. UWB radars can even see underground to detect mines, pipes, and so on. UWB radar is used by fi re, emergency, and police personnel to see through walls and doors. Medical versions permit body imaging for diagnosis.

There are several target markets for UWB. First is computer peripherals. UWB, when married to the popular PC and laptop USB (Universal Serial Bus) interface, permits a wireless USB connection. USB is used almost exclusively today for connecting devices to PCs and laptops such as printers, mice, external drives, and networking equipment. By making the interface wireless, cables and the hassle of connecting them are eliminated. This application for UWB never developed as most wireless PC peripherals use either Wi-Fi (printers) or Bluetooth (keyboard, mouse).

UWB is also attractive for wirelessly connecting video equipment. Because of the very high-speed nature of digital TV and video, superhigh-speed wireless technology is needed for transport. Using a UWB link gives even higher speed with very low power consumption. The range is limited, but video links are usually short from the TV set to a cable box or DVD player or to a camcorder or wireless speakers. The multiband OFDM form of UWB is not widely used but is found in some wireless laptop docking stations for video monitor connection.

Additional Wireless Applications

Bluetooth and Wi-Fi are the most common. These will continue to dominate, but newer technologies will certainly be developed and new applications found. Three other technologies that deserve mention here are TV white space (TVWS), the Internet of Things (IoT), and machine-to-machine (M2M).

TV White Space

“White space” is the term used to refer to the unused TV channels that are present around the United States. The idea is to use the vacant channels for short-range data transmission. The number and location of these unused channels vary widely from location to location, so cognitive radio techniques are used to identify vacant channels that are least likely to interfere with the TV channels. A national database of TV station locations and open channels lets the cognitive radio identify and hop to an appropriate clear channel.

TVWS uses the TV channels in the 470- to the 710-MHz range. These are UHF TV channels 20–31. The channel bandwidth is 6 MHz. The basic modulation scheme is BPSK, QPSK 16QAM, or 64QAM. The transmit power level is 20 dBm, and the antenna gain is 0 dB. These low frequencies offer an exceptional range, far greater than other Wi-Fi versions in the 2.4- and 5-GHz range. Ranges to several miles are possible. Data rates vary depending on modulation type, range, and other factors. Current commercial products offer data rates to 20 Mbps.

The main applications for TVWS have yet to be established, but potential uses include Wi-Fi backhaul, telemetry, and remote monitoring and control, and wireless broadband Internet access for rural areas.

Current equipment for white spaces initially uses proprietary wireless standards. However, the 802.11af Wi-Fi standard targets the TV white spaces opportunity. The 802.11af standard defines the PHY and MAC layers for white space operation. You will hear of 802.11af referred to as Super Wi-Fi or White-Fi. Another IEEE standard 802.22 has been developed for white spaces. Both 802.11af and 802.22 are based on OFDM.

Machine-to-Machine (M2M) and Internet of Things (IoT) Applications

Both M2M and IoT are movements that seek to connect devices to one another or connect devices to humans wirelessly. M2M has been in development for over two decades, beginning with various applications in telemetry, industrial automation, and systems like SCADA (supervisory control and data acquisition). M2M’s goal is to connect machines to one another and to facilitate automated communications between them. M2M-enabled devices can exchange information, make decisions, and implement operations without the help of a human. M2M is the automated remote monitoring and control of objects. Remote monitoring of pipelines and vending machines and the tracking of trucks and fleet vehicles are common uses today. Connectivity has largely been cellular, although other technologies like Wi-Fi are used.

M2M forms the basis for IoT. IoT, or the Internet of Everything as some call it, is a broader vision for connecting machines to one another or machines to humans. M2M focuses predominantly on industrial, business, and commercial applications. IoT is more for consumer-related applications. The big idea is to put almost anything on the Internet so that it can communicate with remote computers, other devices, or even humans.


The uses of M2M include transportation, energy, industrial, sales and payment, security, and healthcare. For example, transportation includes trucking companies that monitor the location and status of tractors and trailers. Automotive fleet management is another. Both of these involve location, so all include embedded GPS receivers. Any large asset can be tracked this way. Most of these applications use cellular connections. Automotive uses are also emerging.

Energy applications are based on the smart grid. M2M is increasingly used to monitor electricity-generating facilities, substations, and related equipment. It is extensively used in wind- and solar-generation plants. M2M has also come to some home neighborhoods for sending utility meter data back to the utility. Smart meters in homes transmit electric or gas usage to a nearby concentrator hub using ZigBee or some other wireless technology. The concentrator then connects back to the utility via the cellular network of some other wireless method.

Industrial M2M is simply a variation of industrial automation communications. There are many forms of industrial networks, and a growing number are wireless. Telemetry is the biggest category, used for the monitoring of oil and gas pipelines, tank farms, oil rigs, and other remote facilities by cellular or other connections.

Sales and payment uses are everywhere. Point-of-sales terminals are all networked, many by wireless. Vending machines and kiosks are often monitored by cellular. Security is a major category. M2M is used for all manner of security monitoring. Much of it is a video that is recorded and sometimes monitored by a human. Cellular is the usual choice, although other wireless links are often involved. Healthcare applications mostly involve remote patient monitoring. Automotive communications are one of the fastest-growing M2M categories.

As for wireless technology, and can be used but most of it is done with cellular connections. Most applications require only low-speed data rates (<1Mbps), so 2G technology is adequate. However, because many cellular carriers are planning to phase out 2G in the future, most M2M applications use 3G. LTE is also available.

M2M services are offered by most cellular operators. Fig. 21-21 shows a complete cellular modem that can be embedded into almost any product. Some include a GPS receiver for tracking. Wi-Fi, ZigBee, and Bluetooth can also be used.


The Internet of Things is like M2M but with a broader scope of applications. It is more oriented to consumer and general commercial applications. IoT assumes that each “thing” has an IP address. It can be almost anything. IoT has been a good concept for years, but now it is in its very early stages of development and deployment. Like all new technologies, it has started with proprietary products and systems but seems destined to develop where standards are available to move the concept forward to implementation.

Fig. 21-22 shows a simplified diagram of an IoT application. The device to be monitored or controlled contains an embedded wireless transceiver that talks to a gateway or router that has an Internet connection. For example, a home thermostat would communicate by Wi-Fi with the home Wi-Fi router, which connects to the Internet via a cable TV or DSL link. That link connects with a remote cloud-based server that supplies the application’s intelligence. It collects the data, analyzes it, stores it, makes decisions, and can initiate actions. This server connects by way of the Internet to the application’s interface, where another machine like a PC analyzes and displays status and actions. A popular application interface is a smartphone; these are quickly becoming our all-purpose remote controls.

Most IoT applications are in the home. Any appliance, large or small, is a target. Some washers, dryers, refrigerators, and dishwashers already incorporate Wi-Fi to automatically report usage and problems to the manufacturer. Small appliances, like a crockpot or coffee maker, can also be controlled. They can be turned off and on, and their temperature can be controlled with an app from an iPhone. LED lighting control is another use. Some manufacturers make a generic device that lets do-it-yourselfers (DIYs) build solutions by adding Internet connectivity to any device controlled with a DC switch, such as robots, motors, sprinklers, and so on, via an iPhone app.

Another very popular IoT device is the thermostat. A smart thermostat with IoT can replace most existing thermostats for improved monitoring and control of heating and air conditioning for energy savings. It is linked by Wi-Fi to the home router, and a smartphone app lets you view settings, change settings, and view times of change.

Note the theme here. A smartphone or a tablet is used as the monitor and control device. These are ideal platforms for Internet connections. That means more machine-to-human communications, rather than machine-to-machine as with pure M2M.

The number of possible home applications is huge. Besides appliances, IoT will include things like garage doors, door locks, security systems including remote video monitoring, and lighting. Whole-home automation is still a niche, but IoT should make it more popular.

One other burgeoning area of IoT is health and fitness. Patient monitoring has become popular. In medical patients, specific body functions are tracked with sensors like electrocardiogram patches, sleep sensors, blood glucose, and blood pressure monitors, and thermometers, and these must be constantly monitored to ensure wellness. Patients can be quickly and easily provided with sensors and wireless connections that gather data for transmission later or even in real-time.

Wearables are another IoT category. This is a new classification consisting of gadgets like Google Glass, smartwatches, and sensors embedded in clothing like vests and coats. These devices usually connect via Bluetooth to a smartphone or other platform for further processing and connectivity.

Fitness is a related segment and definitely a hot topic. A variety of products transmit exercise data, such as heart rate or pedometer steps, from Bluetooth sensors to a smartphone for collection, storage, and analysis. The general acceptance of wearables has yet to be determined, but it will no doubt be part of the IoT mix.

As for wireless platforms, and can be used. Wi-Fi is the most common, but cellular, ZigBee, and Bluetooth are also widely used. Many market research firms and IoT companies are predicting 30 to 100 billion connected devices in the world by 2020.

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