Saturday, January 1, 2011

【 Weak current College 】 two wireless communication technology application 】

Summary: through Bluetooth and UWB technology comparison and analysis of multiple perspectives, confirmed the Bluetooth + UWB as next-generation high-speed wireless communications technology.
As the Internet, multimedia and wireless communication technology development, people and information network has been inextricably linked. Today's wireless communication in people's lives playing an increasingly important role, low power consumption and miniaturisation is a user on the current wireless communication products, in particular the pursuit of highly portable products, as wireless communication technology is an important branch of short-range wireless communication technologies are becoming more and more extensive note due.
1 introduction of short-range wireless communication technologies
In recent years, due to data communication needs, coupled with the semiconductor, computer, and other related electronic technology area of rapid development, short distance wireless and mobile communications technologies has also experienced a rapid growth phase, WLAN, Bluetooth, UWB, and purple bees (ZigBee) technology has made notable achievements. Short-range wireless communication usually refers to communication, within 100m into high-speed short-range wireless communication and low-speed-distance wireless communication. High speed short distance wireless communication maximum data rate > 100Mbit/s, communication distance < 10m, typical technology with high-speed UWB, WirelessUSB; low-speed-distance wireless communication of minimum data rate < 1Mbit/s, communication distance < 100m, typical technology Bluetooth, UWB purple bees and low speed.
2 Bluetooth (Bluetooth) technology
"Bluetooth (Bluetooth)" is an open, standard for short-range wireless communication technology, is currently the most new an open specification for wireless communication. It can, to a lesser extent, through wireless connection security, low-cost, low power network of the Internet, allowing close various communication devices to achieve the seamless sharing of resources, can also be achieved in a variety of digital devices for voice and data communications. Because of Bluetooth technology can be easily embedded into a single CMOS chip, therefore particularly suitable for small mobile devices, enabling the device to remove the connection cable of inconvenience to establish communication by wireless.
Bluetooth technology for low-cost short-range wireless connections, with high frequency hopping (FrequencyHopping) and time division multiple access (TDMA TimeDivisionMulti-access —) and other advanced technology, for fixed and mobile communications environment to establish a special connection. Bluetooth technology enables some of the portability of mobile communications equipment and computer equipment do not need to use cables can be connected to a network, and be able to achieve a wireless connection to the Internet, its practical application range can also be extended to all kinds of household appliances, consumer electronics and household appliances, automobiles, and other information to form a huge wireless communications network. Printer, PDA, desktop computers, fax machines, keyboards, joysticks, and all other digital devices can become part of the Bluetooth system. Currently Bluetooth standard is IEEE802.15, working in 2.4GHz band, channel bandwidth for lMb/s, asynchronous asymmetrical connection maximum data rate for 723.2kb/s. Bluetooth rate also intends to further enhance the new Bluetooth standard 2.0 Edition supports up to 10Mb/s above rate (4, 8 and 12 ~ 20Mb/s), this is the future more and more broadband multimedia business requirements of evolution.
As an emerging technology, Bluetooth technology also exist many problems and deficiencies, such as the cost is too high, short range and speed, and security performance is not satisfactory. But there is no doubt, Bluetooth technology has become in recent years, the application of the fastest wireless communication technology, it will in the near future, penetrated into all aspects of our lives.
3 ultra-wideband (UWB) technology
Ultra-Wideband (UWB Ultra-wideband —) technology originated in the late 1950s, previously used primarily as military technology in radar and other communication devices. With the rapid development of wireless communications, high-speed wireless communications has set higher requirements for ultra-wideband technology has been renewed, and award-winning attention. UWB is a signal bandwidth greater than 500MHz or signal bandwidth and center frequency ratio is greater than 25% of wireless communication solutions. And common use continuous carrier communication in different ways, UWB uses very short pulse signal to transmit information, typically each pulse duration only skin seconds to several tens of nanoseconds. So the pulse bandwidth occupied by or even up to several GHz, the maximum data transfer rate can reach a few hundredths. At the high-speed communications, the UWB device transmitting power is very small, just a few of the existing equipment by 1%, for ordinary non-UWB receiver, approximate the noise, so theoretically, UWB radio equipment with an existing share bandwidth. UWB is a high-speed, low power data communication system, it is expected in the field of wireless communication for a wide range of applications. UWB characteristics are as follows:
(1) strong anti-interference performance: UWB hopping spread spectrum signal, when the system has a larger processing gain, in launching the faint radio signals distributed on the broad band, output power even lower than the noise generated by conventional equipment.
(2) transfer rate: UWB data rate can reach several dozens Mbit/s to several hundred Mbit/s, is expected to be higher than Bluetooth 100 times.
(3) bandwidth is very wide: UWB bandwidth usage above the 1GHz, up to several GHz. UWB system capacity is big, and may and the present narrow-band communication systems at work and do not disturb each other.
(4) consumption of electric energy small: typically, a wireless communications system in communication requires continuous transmission carrier, therefore consumes a certain power. While not using the carrier, UWB just issue the instantaneous pulseRed wave, which is the direct press 0 and 1 sent out, and send pulses only as needed, so consumption of electrical energy waves.
(5) confidentiality: the confidentiality in UWB for two aspects: one is to use time-hopping spread spectrum, the receiver only known sender PN to solve emission data; on the other hand is a system for transmitting power spectral density is very low, with traditional receiver cannot receive.
(6) send power very small: UWB systems transmitting power is very small, communication equipment can be used less than 1mW of transmit power can achieve communication. Low transmit power greatly extend the system working hours.
(7) low cost, ideal for compact UWB technology used: as with baseband transmission, without the need for RF modulation and demodulation, there is no need for mixers, filters, RF/TF converter and local oscillator, complex components, the system structure is simplified and greatly reduce the cost, easier integration into CMOS circuits.
Reference documents:
[1] party xuming, Ho Jung. short-range wireless and mobile communications networks [M]-Beijing: telecommunications press, 2004.
[2] Liu Naian. wireless local area network (WLAN)-theory, technology and application [M]. Xidian University Press, 2004.

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