Electronic Design

No Shortage Of Options For Short-Range Wireless

Wireless abounds, and we're addicted to all of it. Sure, we love our cell phones. But don't forget the TV remote, the garage door opener, and remote keyless entry. Or your Wi-Fi laptop and Bluetooth headset. You can't leave out your desktop, which looks neat without those cords for your keyboard, mouse, and printer. The air pressure gauges in your car and security sensors in your house provide peace of mind, too.

Short-range wireless installation seems simpler, faster, and cheaper to install than cable. And just when you think designers have run out of ideas, along comes something new. This perpetual innovation will be with us for a while. What are the trends to watch in 2006?

Bluetooth, The Short-Range King
It was thought that Bluetooth, which has been around for many years, would never live up to its hype. Some people still think that. But just the opposite is true. According to Mike Foley, the executive director of the Bluetooth Special Interest Group (SIG), over 500 million Bluetooth chip sets have been shipped to date. Current shipment rates total over 9.5 million chips per week!

Bluetooth's success comes from the fact that it's incorporated into almost half of today's cell phones. It can be used to connect to wireless headsets as well as provide links to PDAs and laptops. Single-chip Bluetooth transceivers cost less than $5 in volume. With dozens of application Profiles now available, it's easier than ever to integrate it into other products too.

Simple point-to-point connections are the most common applications. Yet Bluetooth is a personal-area networking (PAN) technology that lets up to seven Bluetooth transceivers automatically seek out and connect to one another to form a piconet. Basic Bluetooth reaches about 10 m. Its high-power option, though, boosts this to almost 100 m with a clear line of sight. Also, the Enhanced Data Rate (EDR) feature in Bluetooth 2.0 kicks the original 1-Mbit/s data rate up to 3 Mbits/s.

While Bluetooth is established in cell phones, PC peripherals, and automobiles, look for increased use in stereo audio, MP3 players, home and industrial automation, and Voice over Internet Protocol (VoIP) systems. By using companion near-field communications (NFC) transceivers, it's simpler than ever to pair two Bluetooth devices. Look for some video applications as well.

The Bluetooth SIG is working with Ultra-Wideband (UWB) wireless vendors to further extend Bluetooth's usefulness by developing a very high-speed (100 Mbits/s+) version. Despite the competition from Wi-Fi and ZigBee in some applications, Bluetooth should hold its own as king of short-range wireless.

Wi-Fi Stays Competitive
Wi-Fi is the popular name given to products implementing the IEEE 802.11a/b/g local-area network (LAN) standard. It's widely used in laptops to link to in-house LANs as well as to the tens of thousands of hotspots around the world. More than 90% of all laptops now come with Wi-Fi. But it doesn't stop there. Wi-Fi is landing in many other wireless applications where speed and range are critical.

Wi-Fi transceivers can achieve a bit rate of 54 Mbits/s at a range extending to 100 m?tops among short-range technologies. Today, 802.11b/g standard radios dominate. The 5.0-GHz 802.11a technology is stagnant because the equally fast 11g version is backwards-compatible with 11b in the 2.4-GHz band.

One major trend is to employ Wi-Fi in mesh networks. This greatly extends a Wi-Fi node's range, since it uses other nodes as repeaters in a fully linked network. Available multiple paths increase reliability further.

The city of Philadelphia plans to build a city-wide LAN, providing its citizens and visitors with access to the Internet for e-mail or whatever from anywhere in town. Earthlink will build the new network with Wi-Fi. San Francisco and hundreds of other cities are looking at similar systems. Phone and cable companies plan to fight this trend, as they believe it encroaches on their legacy approval to provide such services.

Look for growth in municipal Wi-Fi mesh, giving the masses broadband coverage. So far, though, no mesh Wi-Fi standard exists. The IEEE is working on it in task group 802.11s, but a final standard is probably a year away. In the meantime, various proprietary mesh schemes will be adopted where interoperability from city to city isn't an issue.

Wi-Fi's future seems very bright thanks to its forthcoming incorporation into cell phones. Nokia's Wi-Fi-equipped phone permits VoIP calls via a LAN or hotspot. As VoIP becomes more available, the Wi-Fi phone will provide unlimited connectivity. A single phone can supply regular outside cellular service while serving as an in-house phone via a Wi-Fi access point within a business.

On top of that, Wi-Fi is showing up in consumer devices like digital cameras. It provides enough speed to transfer huge photo files to a PC or printer in a reasonable time. Another application involves video transfer in home-entertainment centers. Wi-Fi offers high speed now, but even more speed is on the way.

The IEEE and various industry players are developing the next higher-speed version of the standard: 802.11n. It promises speeds of 100 to 600 Mbits/s over a range of up to 100 m. Multiple-input/multiple-output (MIMO) and spatial multiplexing technologies increase speed over the same range. They also improve the connection's reliability to deliver quality of service. MIMO uses multiple antennas and transceivers with parallel data streams to achieve those goals.

Standards work is going through the usual debates, confrontations, and negotiations. Two factions are vying for their own version to be adopted, so there's gridlock. As a result, 49 manufacturers from both factions formed the Enhanced Wireless Consortium (EWC). It has put forth a compromise standard version that may break the logjam and expedite the process. While some vendors are already selling pre-n wireless products that deliver over 100 Mbits/s at longer ranges, a final standard isn't expected until later this year or perhaps 2007.

Wimax?The Broadband Option
WiMAX is the name of IEEE's 802.16 high-speed wireless option targeting broadband solutions. It uses orthogonal frequency-division multiplexing (OFDM) to deliver up to 70 Mbits/s for up to 30 miles. Normal usage will mean the typical basestation range will only be several miles at most, with the speed divided into multiple slower channels of T1 speed or higher.

The goal is to provide a wireless broadband option to places that don't have access to high-speed cable or digital subscriber line (DSL) Internet service. No U.S. carrier offers WiMAX service so far, though most carriers are testing it. With chips and equipment just arriving in the marketplace, applications are limited. One popular initial use is hotspot and cell-site back-haul to eliminate the high cost of a T1 line or other wired connection. WiMAX also is finding many applications in countries that lack a huge telephone and Internet infrastructure.

Further potential will come to WiMAX now that the 802.16e version of the standard has been ratified. It's called mobile WiMAX because it permits nodes to be in motion at speeds to 100 mph, making WiMAX a possible alternative to 3G cell phones. It also may turn it into an even longer-range replacement for Wi-Fi. WiMAX mobile will have to be good to beat a 3G phone card in a laptop.

As for projections, most experts believe that WiMAX won't ever replace cable TV or DSL (Fig. 1). But it will provide a viable option for people who don't have broadband service now. Furthermore, most experts believe that WiMAX won't materially impact 3G cell-phone systems. Carriers have invested heavily in 3G already, and they're just beginning to roll it out.

While carriers are testing WiMAX, it won't replace 3G. The lack of suitable spectrum is hampering adoption in the U.S., so most initial applications will be in Europe, Asia, and developing countries. No one is sure just where WiMAX will find a home, but most experts agree it's a great technology that will find a niche.

It's Simpler With Zigbee
ZigBee is the name for a short-range wireless technology designed for low-speed monitor and control applications. It's based on the IEEE 802.15.4 PAN standard, which provides short-range (less than 10 m) connectivity for remote measuring and simple control.

The ZigBee Alliance adds greater functionality with its networking layers, which makes ZigBee a super choice for low-cost mesh applications. The most popular form of ZigBee uses offset-quadrature phase-shift keying (O-QPSK) direct-sequencing spread-spectrum (DSSS) in the 2.4-GHz Part 15 band. Up to 250-kbit/s data speeds are possible for networking applications.

It targets commercial building automation of lights, HVAC and security, industrial monitoring, automatic meter reading, and home automation and control. Many chip sets, modules, reference designs, and development systems are now available, so look for ZigBee-based end products beginning this year. Also, ZigBee's inherent mesh capability makes any network more reliable, as well as extends the range of any given node by using all other nodes as repeaters.

UWB: High Speed And Low Cost
UWB is the unusual wireless mode that spreads itself out over a huge bandwidth, offering very high data rates with no interference to other services. The Federal Communications Commission permits UWB in the in the U.S. over the 3.1- to 10.6-GHz range. A wide range of technologies have been tried, but two versions are currently available.

The older version is called direct-sequence UWB. It uses short, uniquely shaped pulses to spread the signal over a wide range. Speeds from 100 Mbits/s to 1 Gbit/s are possible. A newer OFDM version uses three 528-MHz bands in the 3.1- to 4.7-GHz range. No standard is established yet, but these two versions are now available from multiple chip companies. The target for UWB is wireless consumer video connectivity and a 480-Mbit/s wireless USB version (Fig. 2).

The higher speeds are achieved at a range much less than the maximum of about 10 m. Though that will limit its usefulness, the high speed should make it attractive nonetheless. Video will be the major beneficiary of this technology. Like any new method, the applications will emerge soon. Also, look for UWB to show up as the physical layer of choice on the future roadmap for Bluetooth.

RFID Tracks Anything
RFID is an electronic bar code. A tiny chip with an antenna transmits a unique code and other information that identifies the item to which it's attached. RFID tags are useful for a wide range of identification duties. Asset tracking, inventory control, and shipping are primary uses. Many other applications are on tap, though, such as automated toll taking, parking access, consumer purchases, and employee ID security.

The big issue is tag cost. Bar codes are dirt cheap because they can be printed on any product. The least-expensive RFID tags, passive tags, get their power via the RF signal transmitted by an interrogator or reader. The tag backscatter modulates the RF carrier to transmit its ID information. But even these simple tags cost 20 to 50 cents, depending upon volume, which is too expensive for many lower-cost items but okay for trucks, large shipping containers, pallets, or cases of products.

Despite the cost, large retailers, the military, and other organizations are rapidly adopting RFID. The key to success is the middleware software. It performs data filtering and analysis to accept and manage the massive amount of data generated by the multitude of tags being read. Early adoption also shows that there's still a large number of read errors, especially when they speed past the reader and distance from the reader is too great, or too many items are being read simultaneously.

While the second-generation (Gen2) UHF chips help solve these problems, active tags using a small battery may be the solution to most current read problems. Active tags extend the read range and greatly improve the reliability of reading. RFID is a valuable technology that will continue to improve and become more widely adopted?that is, if its application isn't restricted. Many people believe it to be an intrusive technology that could limit personal movement and privacy.

Short-range wireless technology is alive, well, and growing. Lesser-used wireless methods, such as infrared (IR) data transmission, NFC, magnetic wireless, and ISM-band (industrial, scientific, medical) amplitude shift keying/frequency shift keying (ASK/FSK) solutions, also will continue to serve specialized niches.
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