Cutting the Cord: Going Wireless!

Auri Rahimzadeh

(As parking applications move to current technologies, it's important to know their features and drawbacks. PT's IT consultant, Auri Rahimzadeh, gives a primer on wireless applications. Editor)

Traditionally, device interconnects, exchanging data and computer communication have been done via wired networks. Only recently have we had the opportunity to choose from many standardized wireless networking topologies, freeing us from many wired network hassles and bringing network connectivity to places previously unreachable in garages and in the field.
In this article, I want to give you a description of the most prevalent technologies for interconnecting devices wirelessly and for interdevice communication -- with pros and cons and some "gotchas" to look for before and after potential deployments.
802.11 -- a.k.a. "Wi-Fi" -- is quickly becoming the standard for wireless network deployments across the United States and indeed the world. The Institute of Electrical and Electronics Engineers (IEEE) is an established standards body that has defined many technologies via its internal open working groups (WGs).
802.11 is named such due to its IEEE working group being group 802.11. IEEE Project 802 is also called the LAN/MAN Standards Committee (LMSC), and the 802.11 working group handles wireless LANs. Tens of millions of IEEE 802.11 devices have been deployed worldwide and are interoperable.
IEEE 802.11 has many flavors. The most widespread today is 802.11b (named after IEEE 802.11 working group B), which operates in the unlicensed ISM (Industrial, Scientific and Medical) band at approximately 2.45 GHz, and can transmit up to 11 megabits per second (Mbps).
Newly available 802.11 flavors include 802.11a and 802.11g. 802.11a and g support speeds up to 54 Mbps (in the standard, proprietary solutions claim faster speeds), and operate in the ISM band, as well as the newly unlicensed U-NII (Unlicensed National Information Infrastructure) band, at 5.2 and 5.8 GHz.
Even though 802.11 is a standard, its availability is restricted in different regions of the world due to varying regulations. Generally, 802.11b in the United States has 13 broadcast channels available for use (three optimal ones because they are non-overlapping). Generally, 802.11a in the United States supports 140 channels, with 12 non-overlapping optimal channels. However, in France and Spain, the various channels available to 802.11b and g users is severely limited (one non-overlapping channel), while there are actually more channels available in Japan (13 channels, three non-overlapping).
Take note: Even though 802.11a provides so many optimal channels, the international legalization of its 5.2 GHz frequency use has not been standardized, so outside-U.S. deployments may run into broadcast legal issues. Another note: The 5.2 GHz U-NII spectrum is also used by microwave landing systems to help airplanes land in bad weather. Indeed, high-power broadcasts emanating from your parking garage interfering with airplanes landing may irk some senior management, and possibly the FAA.
The speed at which data is transmitted can make a difference in the success of a wireless deployment. If you decide to implement 802.11b or g, you may want to forgo the higher speeds (54, 33, 22, and 11 Mbps) for slower ones (1 and 2 Mbps), which provide for more robust transmissions and greater distances. Before deploying, consider the speeds you need to get data across, as well as same-spectrum device interference issues.
Bluetooth could be considered the next generation of an alternative to infrared technology. Infrared is commonly used today for line-of-sight (the devices have to see each other, with nothing in the way) wireless networking applications, such as PDAs or handheld devices communicating with a computer or base station.
Handheld parking ticket generators may use infrared at the end of the day to transmit data to a main system. Infrared has served its purpose well over the years, but non-line-of-sight and greater distance, yet low-power, low-cost multi-device solutions (infrared is one-to-one) are needed today.
I am not elaborating much on infrared technology in this article. Please email me if you'd like me to cover that in more detail.
To recap: The infrared standard is IrDA, controlled by the Infrared Data Association. It can transmit line-of-site to any other IrDA-capable device at many speeds, up to four megabits per second (sixteen Mb/s rates are in the works).
IrDA provides a different level of security since (a) the devices must be able to see each other and (b) each device could encrypt the connection's data and always "see" whom they're sending to without someone covertly listening in (e.g., in the other room).
The technology is also deployed in millions of devices worldwide, including PDAs, cell phones, laptops, handheld devices and consumer electronics equipment. It is cheap and easy to deploy for uses such as information kiosks (beaming parking garage maps and tourist information to PDAs, for example) and remote control systems where the signal must go only to the device it's being pointed at (such as your TV remote to the television in front of it, instead of one in another room).
(For those wondering where the funky name came from, it stems from the great influence Baltic-region companies have had on the Bluetooth standard. Harold Bluetooth was the king of Denmark in the 900s.)
Bluetooth has a number of advantages for short-distance radio transmissions, such as handheld device communication, synchronization, printing and talking to cell phones (e.g., for an Internet connectivity), among many other uses.
Unlike 802.11x, which generally has a 6 milliwatt (mW) transmitter, Bluetooth transmitters tend to use only 1 mW, greatly reducing the battery drain and transmission radius, thus helping to prevent Bluetooth devices from interfering with adjacent networks. Like 802.11b and 802.11g networks, Bluetooth runs on the unlicensed ISM band, so keep that in mind when deploying Bluetooth where an 802.11b or g network already exists.
Bluetooth is well-suited for transmitting small amounts of data between devices. Generally, Bluetooth devices transmit at 1 megabit/second, compared to 1-54 Mbps for 802.11x and up to 4 Mbps for IrDA (an infrared standard).
Bluetooth also has standard device classifications. As a result, Bluetooth devices can intelligently communicate with one another automatically, such as placing a Bluetooth-enabled cell phone next to a Bluetooth-capable
laptop and automatically providing Internet services (after manually establishing classes of wireless (akin to 802.11 being a wireless version of Ethernet).

Auri Rahimzadeh can be reached at

Article Abstract from August, 2004

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