There are several technologies that need covering at this time. The networking protocol, IEEE 802.11b; Bluetooth, a short-range radio communications standard; GSM (Global System for Mobile) Communications, the European mobile communications standard; CDMA (Code-Division Multiple-Access), the United States mobile telephone standard; WAP (Wireless Application Protocol), defined as a communications method and markup language to produce Web pages for cellular phone display; LMDS (Local Multipoint Distribution Services), 28-GHz frequency television band used for Internet access; and MMDS (Multichannel Multipoint Distribution System), another television frequency being used for Internet access. All of these technologies are defined generally as wireless communication. The basic tenant covered within all of this technology is that voice and data can be transmitted via radio frequencies. This opens up both good and bad things for computer users doing wireless communications. The good is that we can move freely about and have communication connections and the bad is that we are open to unauthorized receipt of our data.

The wireless technology started with the development and use of mobile telephone service. In the beginning, the Bell Telephone Laboratories work concentrated on broadcast radio service, wherein an operator would set up a transmitter on a high location and transmit shared channels of two-way voice data. The transmit and receive frequencies are contained in the equipment and handle the voice data. The frequencies were limited and had to have controls for sharing, i.e., a police system with 25 channels and 500 cars, where 20 cars would use each channel.  With the advent of many users, a different antenna system was devised, wherein each antenna had transmit and receive frequencies and was inter-locked in a cell grid. This became the AMPS (Analog Mobile Phone System). The GSM, CDMA, LMDS, and MMDS systems are all technologies derived from this one.

Wireless LANs, Bluetooth, and WAP are also radio frequency driven. They each are designed to handle data outside of the voice range. Each is intended to meet requirements that are not directly interchangeable and have been developed from different specifications. Wireless networks, for example, are intended to work within the LAN (Local Area Network) standards and represents a communication system established by using RF (Radio Frequency) technology to function either as an extension of an existing LAN or as an alternative for a wired LAN. Bluetooth has been developed as a method of communicating with all types of gadgets. It is a device operator using the radio frequency spectrum as its media. WAP is a standard dedicated to Web based browsing via mobile communications devices such as data telephones, PDAs, and computers.

As can be seen, this is a wide spectrum of communications methods using radio frequencies as the data transfer medium. The wireless mobile telephone technologies are more easily understood in that they group nicely into the mobile voice spectrum. That is being blurred as both data and voice are being used in the PDA and data mobile telephone services. The wireless LANs, Bluetooth, and WAP group together in that they are extensions of data transfer using radio frequencies.

Wireless Data Transfer
Wireless LANs are intended to transmit and receive data over the radio frequencies. There are two general methods of doing wireless networks. One is governed by the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard. This standard governs how the wireless communications interfaces with wired networks. The IEEE 802.11b revised standard is the actual LAN standard in current operation by all vendors and uses DSSS (Direct Sequence Spread Spectrum) to support a data rate of up to 11 Mbps. The other technique is called a HomeRF SWAP (Shared Wireless Access Protocol). I do not have much information about the SWAP technology.

Three spread-spectrum communications methods are used in the transmit and receive data process. These are frequency-hopping and direct-sequence, both spread-spectrums communications using different radio communication techniques. The Infrared spectrum also leans its frequencies to data transfer as the third method. Vendors use all three methods in their designs. Transmission of data over the frequency spectrum is regulated by a government agency, the FCC (Federal Communications Commission). All devices must meet the FCC regulations.

Since the wireless network architecture uses electromagnetic spectrum in the form of radio or infrared to send data, there are no wires. This is the greatest advantage and disadvantage. Each host in the LAN requires a wireless LAN NIC (Network Interface Card)/adapter capable of sending in the specified radio or infrared frequency. The wireless adapter is usually in the shape of a Type II PC Card. This allows the adapter to be used either in a laptop, PDA, or PC. The PC usually has an expansion I/O device that plugs into a card slot and accepts the wireless PC Card adapter. The type II slot accepts the PC Card adapter in the laptop and PDA.

The advantage lies in the fact that no wires are required to be in the network. The disadvantage lies in the fact that any computer host equipped with an IEEE 802.11b adapter card can send or receive on that network. This is because the radio signals are sent in a spread-spectrum and are open to any receiver set for that frequency. There are security methods available to keep the radio signals from being used by unauthorized users.

The wireless LAN can be used as a peer-to-peer network wherein the computers communicating with each other, transmit and receive directly from each other. The only layout requirement is that the computer hosts be at the specified distance to send and receive. This is great for two or more computers attempting to send and receive to update each other. It does not lend itself to the office environment wherein there are many computer hosts on the network. An additional device is used to place a wireless host on a wired network. This technique is to place an access point on the wired network so that the wireless host can communicate with the wired hosts on the network. The access point can either be a computer with both a wireless network adapter and a wired network adapter, or a specially built device with the access point built-in. This device usually has a wired network connection that plugs into the wired network at a hub or switch via a Cat 5 wire connection. A dedicated access point can usually support more than one wireless host.

Wireless Applications
A short overview of potential business applications might include inventory control systems, hospitals, manufacturing, hotels, on the spot training or education, trade shows, or small offices. The inventory control technique is used by stores equipped with scanners to scan products on the shelf and then have the scanner transmit to an access point to update the stock on hand. The hospital application might include having patient information be updated via PDAs or laptops by doctors and nurses. The manufacturing application might have certain manufacturing routines programmed to scanners or PDAs for the purpose of reading data and then transmitting it to a central location on a roving route. Hotels might use wireless connections for service communication to determine when the room has been cleaned. Education in schools and training in business can use wireless networks to rapidly extent a network in areas where permanent wiring might not be located. Trade shows are an excellent example of using wireless networks to setup multiple computers in an area to connect together or to an Internet connection without using wires.

The small office or home application is the best example of using wireless networks. Especially, now that broadband routers are being made as wireless devices for Internet connections. It is in the SOHO arena that wireless communication can really shine. Using a broadband DSL or Direct Cable router equipped with wireless capability, any office or individual can easily set up a wireless network that precludes installing cabling or other media equipment. The wireless access can be an addition to an existing network such as the one I use, or it can be used to connect one or more host computers to a network without wires.

Wireless broadband routers normally act as the access point as well as handle the normal router functions. The access point transmit/receive equipment is built into the router and operates within the IEEE 802.11b standard. The router usually has at least one LAN port as well as the WAN port. The WAN port is used to receive the DSL or Direct Cable modem communications. The LAN port makes the router available to connect to a hub or switch in a wired LAN. Remember that the IEEE 802.11b standard communicates at up to 11 Mbps. There are distance limits on where the host computers may be located.

Bluetooth
Bluetooth is a technology that provides a technique to bind mobile communications and mobile computers together in a short-range communications standard. It is a method of wireless connection between gadgets. It connects PDAs to the I/O devices, printers, etc., so that data can be readily accessed. The PDA data transfer is probably the most needed communications avenue required today. As more hand held devices are being used for more things, keeping that data synchronized is really important. The more gadgets, the more confusing the compatibility between each device. This is where Bluetooth comes to a users assistance. The Bluetooth industry alliance saw this coming hardware incompatibility and developed this method of interface. Bluetooth is a limited-distance wireless transmission technology that is developing into a standard. Bluetooth will in the future replace much of the cabling between devices that must now be contended with.

Bluetooth compatibility is designed for world-wide use in the 2.45-GHz unlicenced radio band. It provides data rates of up to 721 Kbps as well as three voice channels. It is designed to work in noisy environments and includes frequency hopping to assure data transmission. The standard contains safeguards for error correction including FEC (Forward Error Correction), CRC (Cycle Redundancy Check), automatic request repeat, and modem AT commands to insure throughput. It functions within the existing protocols such as PPP (Point-to-Point Protocol) and has three levels of security. Each device has a unique 12 bit address like the MAC addresses in Network Interface Cards. Each device supports device authentication and communication encryption to insure that devices that are not authorized can not wander into areas where they are not welcome. Each device operates as a master or slave for transmission purposes. Bluetooth operates on a TDM (Time-Division Multiplexing) scheme wherein master devices send data using an even-numbered slot and slaves send on an odd-numbered slot. These devices have very low power requirements.

HP has delivered its first printer specifically setup for Bluetooth. Bluetooth USB devices and PDAs and data phones are being delivered pre-setup as well.

Conclusion
I have been operating a wireless node in my LAN for over two years. With it, I can take my laptop downstairs and search the Web while watching TV. It transmits through the walls and floors, admittedly at a slower rate, without problems. I am in the process of testing a Multitech RouteFinder broadband router on both DSL and Direct Cable. These devices are shelf items and are inexpensive.