11 wireless LAN access technical issues

11 wireless LAN access technology problems are explained in detail. Wireless LAN access technology mainly introduces Wireless LAN access technology from various access technologies and GSM access technologies. It is easy to complete the configuration. Hurry into the Wireless World.

As the communication market becomes increasingly open, telecom businesses are rapidly developing towards data, broadband, integration, and personalization, and competition among operators is becoming increasingly fierce. The basic point of competition lies in the competition of access resources. How to quickly, effectively, flexibly, and at a low cost to provide various services required by customers has become the primary concern of operators. The wireless access method meets the needs of operators to a certain extent.
◆ No special pipeline line is required for wireless access, which provides service access for areas where optical cables or cables cannot be laid and shortens the project time, saves investment in pipelines.
◆ With the development of access technology, wireless access devices can simultaneously access data, voice, and other services.
◆ You can flexibly adjust the bandwidth based on the increase or decrease of the region's business volume.
◆ Business migration and resizing are very convenient. The advantage is more obvious in the application of temporary business points.

Generally, wireless access can be divided into two types in terms of structure. One is that local devices are connected wirelessly, which is equivalent to a repeater. In addition, the user terminal uses wireless access to access local devices.

1. Wireless LAN Access Technology GSM access technology

GSM is a standard of mobile communication technology originating in Europe and the second generation of mobile communication technology. This technology is a common technical representative of personal communication. It uses narrowband TDMA, which allows eight groups of calls at the same time at a single radio frequency (RF. GSM was put into use in 1991. By the end of 1997, it has been operating in more than 100 countries and has become an actual standard in Europe and Asia.

The GSM digital network has strong confidentiality and anti-interference capabilities, clear sound quality, stable calls, large capacity, high frequency resource utilization, open interfaces, and powerful functions. China introduced this technical standard in early 1990s. Previously, it had been using cellular analog mobile technology, that is, the first generation of GSM technology, which was disabled by China in December 31, 2001 ). Currently, China Mobile and China Unicom each have a GSM network. The total number of GSM mobile phone users is more than 0.14 billion, making it the world's largest mobile communication network.

2. Wireless LAN Access Technology CDMA Access Technology

CDMA is short for code-divisionmultipleaccess. It is called the 2.5-generation mobile communication technology. CDMA mobile phones have the characteristics of clear voice, difficulty in phone disconnection, low transmit power, and strong confidentiality. The transmit power is only 160 of the transmit power of GSM mobile phones, which is called "Green mobile phones ".

More importantly, the broadband-based CDMA technology makes video applications in mobile communication possible. Like GSM, CDMA is also a mature wireless communication technology. Unlike GSM, which uses the Time-DivisionMultiplexing technology, CDMA does not assign a definite frequency to each user, but allows each channel to use all the spectrum provided.

Therefore, CDMA digital network has the following advantages: efficient bandwidth utilization and greater network capacity, simplified network regulation, high call quality, good confidentiality and signal coverage, and difficulty in dropping calls. In addition, the CDMA system uses the encoding technology. There are 0.44 billion kinds of numbers in the Code arrangement, and the encoding of each mobile phone is still changing at any time, which makes the code piracy only possible theoretically.

3. Wireless LAN Access Technology GPRS Access Technology

Compared with the original GSM dialing method, GPRS is a group switching technology. Because of the use of the "Group" technology, users can access the Internet without being disconnected, probably like using the Download Software NetAnts.

In addition, the method of using wireless LAN access technology to access the Internet through GPRS is different from that of WAP. Using WAP to access the Internet is like accessing the internet at home. First, "dial-up connection" is used, and the Telephone Line cannot be used at the same time after the Internet is connected, however, GPRS is superior, and data downloading and communication can be performed at the same time. Technically, if you only need voice calls, you may wish to continue using GSM. However, if you need data transmission, you 'd better use GPRS.

It increases the application of mobile phones to a higher level. At the same time, the development of GPRS technology is also very "economical", because it only needs to upgrade the existing GSM network. GPRS is widely used, including sending and receiving emails through mobile phones and browsing the Internet.

The biggest advantage of GPRS is that its data transmission speed is not comparable to that of WAP. Currently, the data transmission speed of the GSM mobile communication network is KB per second, while GPRS reaches 115Kbps, which is twice the ideal rate of commonly used 56Kmodem. In addition to the speed advantages, GPRS also features the "always online" feature, that is, the user can keep in touch with the network at any time.

4. Wireless LAN Access Technology CDPD Access Technology

The most important feature of CDPD access technology is its fast transmission speed, and the maximum communication speed can reach 19.2 kbps. In addition, due to the use of RC4 encryption technology, data security is relatively high. Positive and reverse channel keys are asymmetric, and keys are controlled by the Exchange Center and logged on to the mobile terminal once, the Exchange Center automatically checks the old key and replaces the new key once, implementing dynamic management.

In addition, because the CDPD system is an open system based on TCPIP, we can easily access the Internet. All application software based on the TCPIP protocol can be directly used without modification. The application software is easy to develop; the mobile terminal communication number directly uses the IP address. The CDPD system also supports cross-region switching, full-network roaming, broadcast, and group calling. It supports data users with a mobile speed of up to kmh and can communicate with public wired data networks.

5. Wireless LAN Access Technology Fixed Broadband Wireless Access to MMDS/LMDS) Technology

The broadband wireless access system can be divided into MMDSMulti-channel Multi-point Distribution Service and LMDSLocal Multi-point Distribution Service according to different frequency bands, it is a local multi-point distribution service. This is a microwave broadband technology, and has been hailed as a "Wireless Optical Fiber" technology.

It can achieve two-way transmission of voice, data images, videos, conference and television services at a close distance, and supports standards such as ATM, TCPIP, and MPEG2. A service area structure similar to a cellular network is used to divide a service area into several service areas. Each service area has a base station, and the base station equipment communicates with the user end in the service area through a point-to-point wireless link. Each service area ranges from several kilometers to dozens of kilometers and can overlap with each other.

Because NMDS/LMDS features higher bandwidth and two-way data transmission, it can provide a variety of broadband interactive data and multimedia services to overcome the bottleneck of the traditional local loop, it can meet users' increasing demands for high-speed data and image communication. Therefore, it is a powerful tool to solve the communication network access problem.

6. Wireless LAN Access Technology DBS satellite access technology

DBS is also called the digital live broadcasting satellite access technology. It uses the communication satellite in the earth synchronous orbit to send high-speed broadcast data to the user's receiving antenna. Therefore, it is also called high-orbit satellite communication. It is characterized by long communication distance, independent of cost and distance. It has a large coverage area and is not subject to geographical restrictions, bandwidth frequency, and capacity, and is suitable for multi-service transmission, it can provide users around the world with a wide range of roaming and flexible mobile communication services.

In the DBS system, a large amount of data is broadcasted using the High-Speed Uplink Channel of the satellite Main Station and the satellite forwarder after the frequency division or time division modulation, the user receives data through the satellite antenna and satellite Modem, and the receiving antenna is generally 0.53 m or m in diameter.

Because the digital satellite system has high reliability, it does not require much signal correction for analog phones using twisted pair wires in the PSTN network. Therefore, the download rate can reach 400 kbit/s, the actual DBS broadcast rate can reach 12 Mbit/s.

Currently, DBS are available in the United States and are mainly used for Internet access. The largest DBS network is the DirectPC of Hughes Network System Corporation. DirectPC data transmission is asymmetric. when connected to the Internet, the download speed is 400 kbit/s and the uplink speed is 33.6 kbit/s. Although this speed is much higher than that of common dial-up Modem, however, compared with DSL and CableModem technologies.

7. Wireless LAN Access Technology Bluetooth Technology

The English name of Bluetooth is "Bluetooth". In fact, it is a protocol for wireless connection between multiple devices. This Protocol enables information exchange between a large number of devices, including cellular phones, handheld computers, laptops, related peripherals, and home hubs, including home RF. Bluetooth is used to connect a mobile phone to a computer, which reduces the cost of a mobile phone and achieves data sharing, Internet access, wireless hands-free, data synchronization, and image transmission.

Although Bluetooth has great advantages in multi-direction transmission, if there are many devices, the identification method and speed may also be faulty. Bluetooth has one-to-multiple-point data exchange capability, therefore, it requires a security system to prevent unauthorized access. The basic communication speed of Bluetooth is 750 kbits/s, but now the products with 4 Mbits/sIR ports are very common, in addition, 16 mbitss extensions have been approved recently.

8. Wireless LAN Access Technology HomeRF Technology

HomeRF is mainly designed for home networks to reduce the cost of Speech data. To achieve efficient transmission of data packets, HomeRF adopts the CSMACA mode in the standard, which is similar to CSMACD and obtains control over the channel in a competitive manner, only one access point can transmit data over the network at a time point.

Unlike other protocols, HomeRF provides true support for StreamMedia. Because the streaming business sets a high priority and adopts a priority-based re-transmission mechanism, this ensures the bandwidth and low interference and low error codes required for Real-Time Streaming business.

HomeRF operates in the GHz band and uses the Digital Frequency Hopping Spread Spectrum Technology. The speed is 50 hops/s, and a total of 75 bandwidth 1 MHz frequency hopping channels are available. The modulation method is constant envelope of the PSK modulation, which can be divided into two types. FM modulation can effectively suppress interference and fading in wireless environments.

The maximum data transmission rate is 1 Mb/s in 2PSK mode, and 2 Mb/s in 4psk mode. In the latest HomeRF2.x, WBFHwidebandfrequencyhopping technology is used to increase the frequency-hopping bandwidth, from 1 MHz to 3 MHz and 5 MHz, and the frequency-hopping rate also increases to 75 s, its data peak value is also as high as 10 Mb/s, close. the IEEE802.11b standard is 11 Mb/s, which can basically meet the needs of home broadband communication in the future.

9. Wireless LAN Access Technology WCDMA access technology

The WCDMA technology can provide users with a data transmission rate of up to 2 Mbit/s. Under such conditions, any media used in computers can be easily transmitted through wireless networks. The advantage of WCDMA is that the bit rate is high, which effectively utilizes the frequency selective diversity and the space receiving and transmitting diversity.

It can solve the problem of multi-path and fading. It uses Turbo channel encoding and decoding to provide a high data transmission rate. FDD can provide full coverage for wide areas. downlink base stations use unique cell search methods, strict synchronization between base stations is not required. Uses the continuous frequency guide technology to support high-speed mobile terminals.

Compared with the second generation of mobile communication technology, WCDMA has a larger system capacity, better voice quality, higher spectrum efficiency, faster data rate, stronger anti-fading capability, better anti-multi-path performance, and can be applied to up to 500 km /h technical advantages of mobile terminals.

In addition, it can smoothly transition from the GSM system to ensure the investment of operators and provide a good technical foundation for 3G operation. Through the effective use of broadband, WCDMA not only can smoothly process sound, image data, and the Internet fast connection; in addition, WCDMA and MPEG-4 technology can also be combined to process real dynamic images.

10. Wireless LAN Access Technology 3G Communication Technology

The technology, also known as International Mobile Phone 2000, stipulates that when a mobile terminal moves at a speed, the data transfer rate is 144 kbps, And the outdoor static or walking speed is 384 kbps, the indoor bandwidth is 2 Mbps.

However, these requirements do not mean that the user availability rate can reach 2 Mbps, because the indoor rate will also depend on the detailed frequency planning in the building and the closeness of the Organization and operator collaboration. However, since the speed of High-Speed businesses such as wireless LAN can reach 54 Mbps, it is difficult to predict what the market demand for 2 Mbps businesses will be when 3G networks are fully rolled out.

11. Wireless LAN access technology wireless LAN

Wireless LAN WirelessLAN (WLAN) is a combination of computer networks and wireless communication technologies. It is not bound by cables and can be moved. It can solve problems caused by difficulties in wired network cabling and has the advantages of flexible networking, convenient resizing, compatibility with various network standards, and wide application. WLAN can meet the network access requirements of all types of hosts, as well as remote computer LAN access, text and fax, email, and other functions.

12. Wireless LAN Access Technology Wireless Optical Access System (FSO)

The wireless infrared optical transmission system is a combination of optical communication and wireless communication. It transmits optical signals through the atmosphere rather than optical fibers. This technology can provide a rate similar to optical fiber without rare resources such as spectrum. The main features are: high transmission rate, from 2 Mb/s to 622 Mb/s high-speed data transmission; the transmission distance is 200 to 6 kilometers; due to work in the infrared band, it does not interfere with other transmission systems and is highly secure. signals are transmitted and received through optical instruments without the need for a Antenna Feeder System. The devices are small in size.