Unconscious, the wired network has been flooded in our lives, we gradually start to believe that the connection and access of the network is to access a network cable from the wall into the computer, then start our online life. But now it is now changing, the emergence of wireless broadband access technology, making more and more people join the ranks of wireless access and wireless network, starting to enjoy the speed of wired, while It has wireless freedom.
As the user broadband accesss the Internet, each operator is using existing networks to build a broadband access network with a variety of different broadband access. At present, using fiber or wireless approach, technology through ATM or pure IP has solved the community where the broadband access to the user, including some users relatively concentrated, such as hotels, office office buildings, etc. Further access to the home and user side is different. This is mainly caused by the existing conditions of the user, and some places have paved the top 5 lines, and some places have only the twisted pair of simulated calls, how to solve these problems? Each machine is configured with ADSL. The cost will be quite high; use LMDS technology, it is still not mature and the price is very high; the telephone line is connected, the speed is firm; it seems to use 10M / 100M Ethernet It is the most convenient way. However, with people's demand for office, and the increase in new users increase, the network is difficult to expand the problem. Traditional Ethernet access methods have become increasingly unable to meet the needs of people's modern work. The wireless access method is increasingly concerned with its unique advantages.
Research wireless broadband access technology can make us more fully realize the advantages of wireless access, and use wireless access technology more effectively to exert its strengths.
Wireless access technology is compared with past wired technology, the biggest advantage is:
1, mobility. Using wireless space transfer characteristics, there is no trap, access the Internet, anytime, anywhere, and get the latest information.
2, seamless roaming. No need to reconfigure the machine, dynamically perform roaming between the various wireless access networks.
3, easy to use. The province has a hassle for each desktop user separately.
4, flexibility. In complex, multi-change networking environments such as branch office or temporary office location), it is convenient to implement and improve networked capabilities. Wireless access can also be convenient and quickly accepted newly joined networks without having to change much changes to users' management configurations.
5, reasonable price. A set of installation and maintenance costs for a set of wireless broadband access solutions is much lower than the traditional Ethernet access scheme.
6, safety. Relying on complex encryption technology, for those illegal recipients, traffic signals that are intercept wireless broadband access are unusual.
Development status and development direction at home and abroad
First we see the development of technology.
Wireless access technology name
the work
Frequency band
What spread spectrum technology is used?
What modulation technology is used?
transmission
rate
transmission
distance
Other important technologies
802.11 2.4GHz (ISM frequency band) Direct sequence spread spectrum (DSSS) DQPSK DBPSK 1 or 2Mbps dozens of meters to dozens of km roaming (Roaming) and WEP encryption 802.11b 2.4GHz (ISM band) Direct sequence spread (DSSS) CCK DQPSK DBPSK 11MBPS (5.5, 2 or 1Mbps) dozens of meters to dozens of km roaming (ROAMING) and WEP encryption 802.11g (development) 2.4GHz (ISM band) Texas Instrument company PBCC (Group binary volume code) ) Technology and INTERSIL company's OFDM technology CCK-PBCC or CCK-OFDM 22Mbps (CCK-PBCC), 54Mbps (CCK-OFDM) dozens of meters to dozens of km roaming (ROAMING) and WEP encryption 802.11a 5GHz (U-NII) Orthogonal Frequency Division The throughput of the OFDM Physical Layer is divided into 6, 12, 18, 24, 36, 48, 54Mbps 5-10 km support voice, data, image service
Bluetooth 2.4GHz (ISM frequency band) Frequency crossing (FHSS) 1600 / sec GFSK modulation highest rate 1Mbps Effective rate 721kbps 10 meter tone adopts continuous variable slope modulation CVSD, communication protocol uses TDMA Homerf 2.4GHz (ISM band) frequency hopping Spread spectrum (FHSS) DQPSK DBPSK 2Mbps, currently increased to 8-11Mbps 100 m through time division multiplexing support voice communication, providing data communication services through carrier monitoring multi-access / conflict avoidance (CSMA / CA) protocol
Hiperlan / 1 5GHz (U-NII)
GMSK modulation 23.5Mbps 100 meters
Hiperlan / 2 5GHz (U-NII) orthogonal frequency division multiplex qDM is 54Mbps 150m QoS support based on the high-level protocol according to specific requirements
From the table, we can see that various techniques have their own characteristics, and the side focus is different. 802.11 Family has been continuous development, with the development of modulation technology, the transmission rate is getting faster, the use bandwidth is getting wider and wider, the safety performance is getting stronger, the transmission distance is getting farther. And 802.11b and Bluetooth and Homerf have some of the overlapping, its modulation technology is not the same, Hiperlan / 1 and 802.11b are a pair of competitors, and Hiperlan / 2 and 802.11a are another pair of competitors. The modulation techniques they use are also different. Therefore, we need to explore the optimal wireless access to the modulation techniques used under various conditions by research on the modulation techniques used in various wireless broadband access technologies.
Although many standards coexist, there is no restriction of the rapid development of the industry. The reason is that the current wireless LANs generally cannot be applied separately, just as a standby or supplement of the local area network. Just like the broadband access market has an access method such as ADSL, ISDN, CABLE MODEM and other access methods, which do not obstruct users' broadband Internet access, rarely used different standard wireless LANs, so there is no different standard WLAN Interconnected problems. In this sense, major manufacturers insist on launching their own products and standards with their own truth. Generally speaking, the production of unified standards is lagging behind the products and markets, and who is the most widely covered in the product market. Who is possible Become a standard standard.
From the development of foreign-related products, with the maturity of the 802.11b protocol, there is more and more corresponding products, and the supported manufacturers are increasing. Currently, almost all related products of all communications have compliant 802.11b standards. As INTEL, 3COM, CISCO, Ericsson, Lucent, Abovecable and other manufacturers have developed a series of wireless network products, including wireless bridges, wireless network cards, wireless APs, TI (Texas Instruments) also developed The corresponding chip. At present, all major manufacturers are preparing or developing the next generation of products, including a series of products that meet 802.11a and 802.11g norms. Domestic such as Chom, Lenovo, BenQ, Datang, Huawei, ZTE and other manufacturers have also launched the corresponding products and a set of solutions. In Bluetooth products, foreign countries such as 3com, Ericsson, International Commercial Machine (IBM), Intel (Intel), Lucent, Microsoft, Motorola, Nokia, Toshiba (Toshiba) Waiting for Bluetooth, it is also very attached to the mobile phone, Bluetooth is already a practical technology. Companies such as Agilent, Super Blue and other companies have also developed products with Bluetooth technology through OEM or independent development and also focus on the development and promotion of the program. Guangzhou is currently preparing to build a Bluetooth Science and Technology Park, which believes this will greatly promote the development of Bluetooth technology in China. Hiperlan / 2 is supported by European manufacturers such as Ericsson, Philips and Nokia. Because it is similar to 802.11a, the development of 802.11a is significantly better than Hiperlan / 2, so currently related to Hiperlan's mature products are in China or It is very few abroad. Homerf is designed to use wireless phones and LAN functions for home networks, more for transmitting control data for home appliances. Motorola, PROXIM and Ericsson Company are in a leading position in the production and development of Homerf products. There are very few related products in China. Currently, WLAN is still in many standards. Behind each standard has a large company or a large group support. In the United States and Europe, several high-speed wireless standards that are not allowed: 802.11b (also known as Wi-Fi) support from companies such as 3COM, Lucent, Apple, Cisco, etc., this standard is currently very popular in North America; It is Homerf standard supported by Proxim, Motorola, Compaq; US IEEE created another high-speed wireless standard 802.11a, nearly 5 times faster than the current 802.11b technology; the European Telecommunication Standards Committee created a very competitive high-speed standard Hyperlan2, Ericsson Company is the main supporter, current Europe with Hyperlan2 standards.
