Network Common Sense Essays

1. Wi-Fi and WiFi

1) First to literally introduce the next WLAN and wife. WLAN is the abbreviation of Wireless Local area network, which refers to the application of wireless communication technology to interconnect computer equipment, constituting a network system that can communicate with each other and realize resource sharing.
2) wife refers to the place where wireless LAN (WiFi) access to Internet services is provided in public places. Most of these sites are cafes, airports, business hotels, universities, large exhibition halls and so on.
3) can also be differentiated from the transmit signal power size. From the inclusion relationship, WiFi is a standard of WLAN, WiFi is included in the WLAN, is a new technology in the adoption of WLAN protocol. WiFi coverage can reach about 300 feet (90 meters), the maximum WLAN (plus antenna) can be up to 5KM.
4) After we open the WLAN in the mobile phone, there will be a lot of wireless network, we search to connect to the Internet.   But there are many are to password, others can not let free internet. If your home has a network cable. Get a wireless router can also achieve wife wireless Internet access!!

2. Several short-distance transmission of the internet of Things

At present, the use of a wide range of close wireless communication technology is wireless LAN 802.11 (Wi-Fi), ultra-wideband UWB (Ultra Wide Band), ZigBee, short-distance communication (NFC) and so on. Each of them has its own application characteristics, in terms of transmission speed, distance, power consumption and other requirements, or focus on the expansion of functionality, or meet the specific requirements of a single application. Or to establish the differentiation of competitive technology and so on. But there is no one technology that can be perfected enough to meet all the needs of the Internet of things.
1) WiFi Technology
Wi-Fi (Wireless Fidelity, Wireless high fidelity) is a wireless communication protocol (IEEE802.11B), Wi-Fi transmission rate of up to 11mb/s, although in terms of data security than Bluetooth technology, but in the radio The range of wave coverage is notch above, up to about M

2) Wi-Fi is a wireless extension of Ethernet, in theory, as long as the user is located in a certain area around an access point can be at the highest rate of about 11mb/s Internet access. In fact, if multiple users are connected at the same time through a single point,
Bandwidth will be shared by multiple users, Wi-Fi connections will be reduced to only hundreds of kb/s, and Wi-Fi signals are generally not affected by wall blocking, but the effective transmission distance within a building is less than that of outdoors.
3) The original IEEE802.11 specification was proposed in 1997, called 802.11B, the main purpose is to provide WLAN access, but also the main technical standard of WLAN, its operating frequency is 2.4GHz, and cordless telephones, blue and other Many wireless devices that do not require a frequency use license share the same band. With new versions of the Wi-Fi protocol, such as 802.11A and 802.11g, Wi-Fi applications will become more widespread. The faster 802.11g uses the same orthogonal frequency division multiplexing modulation technology as the 802.11B, which also operates in the 2.4GHz band at a rate of up to 54mb/s. Judging by the latest development trends, 802.11G will likely be the product standard for most wireless network product manufacturers. Microsoft's desktop OS Windows XP and Embedded operating system Windows CE, all include support for Wi-Fi.

4) UWB Technology

Ultra-wideband Technology

UWB (Ultra wideband) is a wireless carrier communication technology, it does not use the sine wave carrier, but the nanosecond-level non-sinusoidal pulse transmission of data, so it occupies a wide spectrum range. UWB can transmit signals on a very wide bandwidth, and the U.S. FCC's rules for UWB are: Occupy more than 500MHz of bandwidth in the 3.1~10.6ghz band. Because UWB can use low power, low complexity transmitter/receiver to achieve high-speed data transmission, in recent years has been rapid development. It uses low-power pulses to transmit data over a very wide spectral range without causing significant interference to conventional narrowband wireless communication systems and can make full use of spectrum resources. The high rate data transceiver based on UWB technology has a wide range of uses.

UWB technology has low system complexity, low transmit signal power spectral density, insensitive to channel fading, low interception ability, high positioning accuracy, especially suitable for high-speed wireless access in dense multi-path places such as indoor, and is very suitable for establishing an efficient WLAN or wireless domain network (WPAN).

5) ZigBee Technology

ZigBee is mainly used in the short distance and the data transmission rate is not high between various electronic devices. Zigbee

The alliance was established in August 2001. In the second half of 2002, Invensys, Mitsubishi, Motorola and Philips Semiconductor companies announced the joining of the ZigBee Alliance to develop next-generation communication standards known as ZigBee. All of these companies participate in the IEEE 802.15.4 Working Group that develops technical standards for ZigBee physical and media control layers.

ZigBee Alliance is responsible for developing protocols above the network level. At present, standard-setting work has been completed. ZigBee protocol is simpler and more practical than Bluetooth, high rate personal area network or 802.11x WLAN.

ZigBee can be said to be the same gypsy Bluetooth, it uses the 2.4 GHz band, using frequency hopping technology. ZigBee is simpler, slower, more powerful and less expensive than Bluetooth. Its basic rate is 250kb/s, and when it is low to 28kb/s, the transmission range can be extended to 134m for higher reliability. In addition, it can be networked with 254 nodes to better support gaming, consumer electronics, instrumentation, and home automation applications than Bluetooth.

ZigBee technology features mainly include the following parts:

(1) Low data transfer rate. Only 10kb/s~250kb/s, focused on low-rate transmission applications.

(2) Low power consumption. In standby mode, two normal 5th dry batteries can be used for more than 6 months, which is a unique advantage of ZigBee.

(3) Low cost. Because ZigBee data transmission rate is low, the protocol is simple, so the cost is greatly reduced; Motorola and Philips, which are actively involved in ZigBee development, have introduced application chips. According to Philips estimates, the application

On the host side of the chip cost and other end-product cost than Bluetooth more competitive price.

4)

5) Large network capacity. Each ZigBee network can support up to 255 devices, which means that each ZigBee device can be connected to another 254 devices.

6) The effective range is small. Effective coverage range 10~75m, depending on the actual transmit power size and a variety of application patterns, can basically cover the ordinary home or office environment.

7) Flexible working band. The frequency bands used were 2.4GHz, 868MHz (Europe) and 915MHz (USA), all of which were unlicensed bands.

6) NFC Technology

NFC (near Field communication, close-up wireless transmission) is a short-range wireless communication technology standard that is similar to RFID (contact radio frequency identification) pushed by Philips, Nokia and Sony. Unlike RFID, NFC uses two-way identification and connection, working in the 13.56MHz frequency range within 20cm distance. NFC was initially only a merger of remote sensing and network technology, but it has now evolved into wireless connectivity technology. It can quickly and automatically set up a wireless network for cellular devices, Bluetooth devices,

A Wi-Fi device provides a "virtual connection" that enables electronic devices to communicate over a short range of distances. NFC's short-range interaction greatly simplifies the entire authentication process, making it more straightforward, safer and clearer to access each other between electronic devices.

NFC helps solve the hassle of remembering multiple passwords by combining all of the identity applications and services on a single device, while also ensuring the security of the data. With NFC, multiple devices such as digital cameras, PDAs, set-top boxes, computers, mobile phones, and other wireless interconnection, exchange data or services will be possible to achieve.

In addition, NFC can "accelerate" other types of wireless communications, such as Wi-Fi and Bluetooth, for faster and longer-distance data transfer. Each electronic device has its own dedicated application menu, and NFC creates a fast and secure connection without having to choose from a menu of many interfaces.  Unlike the well-known Bluetooth standard for short-range wireless communication, NFC is further shortened and does not require a corresponding encryption device like Bluetooth. Similarly, building a Wi-Fi family wireless network requires more than one computer, printer, and other device with a wireless card. In addition, there must be a skilled professional to be competent for this work. When NFC is placed in the access point, it can be communicated as soon as two of them are close, which is much easier than configuring the Wi-Fi connection.

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