One of the unusual features of Bluetooth networks is their temporary nature. With other popular wireless standards, you need a central communication point, such as a hub or router. Bluetooth networks are formed on an ad hoc basis, meaning that whenever two Bluetooth devices get close enough to each other, they can communicate directly with each other. This dynamically created network is called a piconet. A Bluetooth-enabled device can communicate with up to seven other devices in one piconet. Within the piconet, one device is the master and the other seven devices are slaves. Technically, communication can occur only between the master and a slave. While this might sound like a problem, the role of master rotates quickly among the devices in a round-robin fashion. In this way, all devices in a piconet can communicate with each other directly. Current Bluetooth specifications allow for connecting two or more pico nets together in a scatter net. In a scatter net, one or more devices would serve as a bridge between the pico nets.
In 1998, a consortium of companies formed the Bluetooth Special Interest Group (SIG), and formally adopted the name Bluetooth for its technology. The name comes from a 10th- century Danish king named Harald Blatant, known as Harold Bluetooth in English. One can only imagine how he got that name. King Blatant had successfully unified warring factions in the areas of Norway, Sweden, and Denmark. The makers of Bluetooth were try- ing to unite disparate technology industries, namely computing, mobile communications, and the auto industry. Current membership in the Bluetooth SIG includes Microsoft, Intel, Apple, IBM, Toshiba, and several cell phone manufacturers. We use the technical specification IEEE 802.15.1 describes a wireless personal area network (WPAN) based on Bluetooth version 1.1. The first Bluetooth device on the market was an Ericsson headset and cell phone adapter, which arrived on the scene in 2000. By 2002, there were over 500 Bluetooth certified products, and as of 2005 over 5 million Bluetooth chipsets shipped each week. The current Bluetooth specification is Version 2.1+ Enhanced Data Rate. According to the Bluetooth SIG, Bluetooth wireless technology is a short-range communications technology intended to replace the cables connecting portable and/or fixed devices while maintaining high levels of security. Bluetooth also operates at low power and low cost and can handle simultaneous voice and data transmissions.
There are three different supported versions of Bluetooth. Version 1.2 was adopted in November 2003, and it supports data transmissions of up to 1Mbps. Version 2.0+ Enhanced Data Rate (EDR), adopted in November 2004, and Version 2.1+EDR, adopted in July 2007, can support data rates up to 3Mbps. All standards transmit in the 2.4–2.485GHz range. The 2.4GHz range is unlicensed, meaning that any wireless technology can use it. Indeed, many cell phone technologies as well as wireless networking technologies do use it. To avoid interference, Bluetooth can signal hop at different frequencies to avoid conflicts with devices using other technologies in the area. For security, Bluetooth uses the Secure and Fast Encryption Routine (SAFER+) encryption routine, a 128-bit algorithm developed in 1998. There have been questions surround- ing how secure Bluetooth really is, and the best advice is to not leave powered-on devices unattended. As mentioned earlier, the first device was a wireless headset for a cell phone, and Bluetooth continues to excel in this field, considering its low power consumption and ample bandwidth for voice communications. Bluetooth-enabled computer peripherals include keyboards and mice, printers, digital cameras, and MP3 players. The technology is also prevalent in PDAs and handheld computers as well as in several cars, including those made by BMW and Toyota (and Lexus). Cards for laptops come in USB and PCMCIA Type II varieties. Figure 10.26 shows a USB model by Link sys. All in all, Bluetooth is a solid technology that should be around for a while. It doesn’t have the range of cellular or the capacity of WiFi, but it fills a nice niche, uses low power, and has developed a critical mass of devices that support it.
Infrared waves have been around since the beginning of time. Infrared waves are longer than light waves but shorter than microwaves. The most common use of infrared technology is the television remote control, although infrared is also used in night-vision goggles and medical and scientific imaging. In 1994, the Infrared Data Association (IrDA) was formed as a technical consortium to support “interoperable, low-cost infrared data interconnection standards that support a walk-up, point-to-point user model.” The key terms here are walk-up and point-to-point, meaning that you need to be at very close range to use infrared, and it’s designed for one to one communication. Infrared requires line of sight, and generally speaking the two devices need to be pointed at each other to work. If you point your remote away from the television, how well does it work. An infrared network is a point-to-point network between two devices. There is no master or slave or hub-type device required. Simply point one infrared-enabled device at another and transmit. Current IrDA specifications allow transmission of data up to 16Mbps, and IrDA claims that 100Mbps and 500Mbps standards are on the horizon. Because it does not use radio waves, there are no concerns of interference or signal conflicts. Atmospheric conditions can play a role in disrupting infrared waves, but considering that the maximum functional range of an IrDA device is about one meter, weather is not likely to cause you any problems. Security is not an issue with infrared. Considering that the maximum range is about one meter with an angle of about 30 degrees and the signal does not go through walls, hacking prospects are limited. If someone is going to intercept an infrared signal, you will know that the person is there and trying to intercept the signal. The data is directional, and you choose when and where to send it.
