|
|
Programming Help |
Homework Help |
Counseling Astrology Advice | Tarot Advice | Parenting Dating Advice | Love Advice | Divorce Advice Legal Advice | Debt Advice | Career Advice W IRELESS N ETWORK S ECURITY 4-3 Mobile routers in a Bluetooth network control the changing network topologies of these networks. The routers also control the flow of data between devices that are capable of supporting a direct link to each other. As devices move about in a random fashion, these networks must be reconfigured on the fly to handle the dynamic topology. The routing protocols it employs allow Bluetooth to establish and maintain these shifting networks. Bluetooth transceivers operate in the 2.4 GHz, ISM band, which is similar to the band WLAN devices and other IEEE 802.11 compliant devices occupy. Bluetooth transceivers, which use Gaussian Frequency Shift Keying (GFSK) modulation, employ a frequency hopping (FH) spread spectrum system with a hopping pattern of 1,600 times per second over 79 frequencies in a quasi-random fashion. The theoretical maximum bandwidth of a Bluetooth network is 1 Mbps. However, in reality the networks cannot support such data rates because of communication overhead. The second generation of Bluetooth technology is expected to provide a maximum bandwidth of 2 Mbps. Bluetooth networks can support either one asynchronous data channel with up to three simultaneous synchronous speech channels or one channel that transfers asynchronous data and synchronous speech simultaneously. Bluetooth uses a combination of packet-switching technology and circuit-switching technology. The advantage of using packet switching in Bluetooth is that it allows devices to route multiple packets of information by the same data path. Since this method does not consume all the resources on a data path, it becomes easier for remote devices to maintain data flow throughout a scatter-net. 4.1.1 Brief History The original architect for Bluetooth, named after the 10 th century Danish king Harald Bluetooth, was Ericsson Mobile Communication. In 1998, IBM, Intel, Nokia, and Toshiba formed the Bluetooth SIG, which serves as the governing body of the specification. The SIG began as a means to monitor the development of the radio technology and the creation of a global and open standard. Today more than 2,000 organizations are part of the Bluetooth SIG, comprising leaders in the telecommunications and computing industries that are driving development and promotion of Bluetooth technology. Bluetooth was originally designed primarily as a cable replacement protocol for wireless communications. However, SIG members plan to develop a broad range of Bluetooth-enabled consumer devices to enhance wireless connectivity. Among the array of devices that are anticipated are cellular phones, PDAs, notebook computers, modems, cordless phones, pagers, laptop computers, cameras, PC cards, fax machines, and printers. Bluetooth is now standardized within the IEEE 802.15 Personal Area Network (PAN) Working Group that formed in early 1999. The Bluetooth SIG Web site provides numerous links to other Web sites with additional information. 38 The IEEE Web site provides updates on the IEEE 802.15 Working Group. 39 This is the Working Group that develops Personal Area Networking consensus standards for short distance wireless networks, or WPANs. 4.1.2 Frequency and Data Rates The designers of Bluetooth like those of the 802.11 WLAN standard designed Bluetooth to operate in the unlicensed 2.4 GHz2.4835 GHz ISM frequency band. Because numerous other technologies also operate in this band, Bluetooth uses a frequency-hopping spread-spectrum (FHSS) technology to solve interference problems. The FHSS scheme uses 79 different radio channels by changing frequency about 1,600 times per second. One channel is used in 625 microseconds followed by a hop in a pseudo-random 38 For more information, see the Bluetooth Web site at http://www.bluetooth.com. 39 For more information, see the IEEE Web site at http://grouper.ieee.org/groups/802/15/ . |
Find more freelance jobs
|
