A survey of short-range wireless communication technology

The current use of a wide range of short-range wireless communications technology is Bluetooth (Bluetooth), Wireless LAN 802.11 (Wi-Fi) and infrared data transfer (IrDA). There are also some development potential of short-range wireless technical standards, they are: ZigBee, UWB (ultrawideband), short distance Communication (NFC), WiMedia, GPS, DECT, wireless 1394 and dedicated wireless systems. They are based on the characteristics of transmission speed, distance, power consumption, or focus on functional expansion, or meet the specific requirements of some single application, or the establishment of differentiation of competitive technologies. But no technology can be perfect enough to meet all the needs.

Bluetooth technology

Bluetooth technology has emerged in recent years, and has been widely concerned by the industry close to the wireless connection technology. It is an open global specification for wireless data and voice communications, which is based on Low-cost short-range wireless connectivity and provides low-cost access to fixed or mobile terminals.

Bluetooth technology is a wireless data and voice communication of the open global norms, its essence is for fixed equipment or mobile devices in the communication environment to establish a common short-range wireless interface, communication technology and computer technology to further integrate, so that all kinds of equipment in the absence of wires or cables connected to each other, Can communicate or operate with each other in close range. Its transmission band for the global public general 2.4GHzISM band, providing 1Mbps transmission rate and 10m transmission distance.

Bluetooth technology was born in 1994, Ericsson decided to develop a low-power, Low-cost wireless interface to build mobile phones and their accessories to communicate between. The technology is also gaining support from industry giants in the PC industry. 1998, Bluetooth Technology agreement by Ericsson, IBM, Intel, NOKIA, Toshiba and other 5 companies to reach agreement.

The standard version of the Bluetooth protocol is 802.15.1, which is developed by the Bluetooth team (SIG). 802.15.1 's initial standard is based on Bluetooth 1.1 implementation, which has been built into many Bluetooth devices in existence. The new 802.15.1a is basically equivalent to the Bluetooth 1.2 standard, with a certain QoS characteristics, and maintain a complete back to compatibility.

But the biggest obstacle to Bluetooth technology is that it's too expensive. Outstanding performance in chip size and price is difficult to cut down, anti-interference ability is not strong, transmission distance is too short, information security issues and so on. This makes many users unwilling to pay a large price for the wireless device. Therefore, industry experts believe that Bluetooth market prospects depend on the Bluetooth price and Bluetooth based applications can reach a certain scale.

Wi-Fi technology

Wi-Fi (wirelessfidelity, wireless high-fidelity) is also a wireless communication protocol, the official name is IEEE802.11B, and Bluetooth, the same as the short range of wireless communication technology. The maximum Wi-Fi rate is up to 11mb/s. Although in the data security than Bluetooth technology to some, but in the range of radio wave coverage is slightly, up to 100m or so.

Wi-Fi is a wireless extension of Ethernet, theoretically, as long as the user is located in a certain area around an access point, you can access the Web at a maximum speed of about 11mb/s. But in fact, if there are multiple users at the same time through a point of access, bandwidth is shared by multiple users, Wi-Fi connection speed will generally only hundreds of kb/s of the signal is not blocked by the wall, but the effective transmission distance within the building is less than outdoor.

The most promising applications for WLAN in the future will be in Soho, home wireless networks and buildings or places where cables are inconvenient to install. At present, the users of this technology are mainly from the airport, hotels, shopping malls and other public hotspot places. Wi-Fi technology can combine Wi-Fi with xml-based or Java Web Services, which can significantly reduce the cost of the enterprise. For example, companies choose to have 802.11b access points in each floor or department, instead of connecting the entire building with a cable line. As a result, it can save a lot of money to spend on laying cables.

The original IEEE802.11 specification was introduced in 1997, called 802.11B, the main purpose is to provide WLAN access, but also the main technical standards of WLAN, it is the operating frequency of 2.4GHz, and cordless phones, Bluetooth and many other wireless devices that do not require the use of frequency licenses share the same frequency band. With the new version of the Wi-Fi protocol, such as 802.11A and 802.11g, Wi-Fi applications will be more and more extensive. The faster 802.11g uses the same orthogonal frequency division multiplexing modulation technology as 802.11B. It works in the 2.4GHz band, the rate reaches 54mb/s. Judging from the recent trends in International consumer electronics, 802.11g is likely to be selected as a product standard by most wireless network manufacturers.

Microsoft's desktop operating system, Windows XP and Embedded operating system WINDOWSCE, all include Wi-Fi support. The WINDOWSCE also includes support for Wi-Fi rivals such as Bluetooth and other wireless communications technologies. Many manufacturers are involved in this area because of the lower cost of 802.11b investment. Intel has launched a laptop chip group with integrated WLAN technology, which enables wireless Internet access without the need for an external wireless network card.

IrDA Technology

Infrared Data Association IrDA (infrareddataassociation) was established in 1993. At first, the IrDA-standard wireless device could only transmit data at a 115.2kb/s rate within 1m range, rapidly developing to 4mb/s and 16mb/s rates.

IrDA is a technology that uses infrared to point-to-point communication, and is the first technology to realize wireless personal local area network (PAN). At present, its hardware and software technology is very mature, in small mobile devices, such as PDA, mobile phones are widely used. In fact, today every factory PDA and many mobile phones, laptops, printers and other products are supported by IrDA.