Wireless network technology paper I
Imagine that in the era of wired network, users' activities are limited by network cables, and they have to drag long cables wherever they go, worrying about finding broadband interfaces. Therefore, wireless network came into being. Compared with wired network, although the bandwidth of wireless network is smaller; Compared with the current limited network, the waiting delay is more; Poor stability; The CPU, memory, display screen and other resources of wireless access equipment are limited. The wireless network can adapt to the complex construction environment, with simple construction and strong cost performance. The biggest advantage is that people can get rid of the shackles of network cables and communicate more conveniently and freely. Therefore, it quickly seized the market from the beginning of development. At present, the coverage of wireless networks can be roughly divided into the following three categories: (1) system interconnection/wireless local area network (2) wireless local area network (3) wireless metropolitan area network/wide area network. Therefore, this paper introduces the application status of various wireless networks.
I. Unlimited personal area network (WPAN)
Wireless personal area network mainly adopts IEEE802. 15 standard. Unlimited LAN can be regarded as a special case of wireless LAN. Its coverage radius is only a few meters. Its main applications include: voice communication gateway, data communication gateway, information appliance interconnection and automatic information exchange. WPAN usually adopts microcellular or femtocell structure. WPAN is one of the fastest-growing fields at present, and corresponding new technologies emerge one after another, mainly including Bluetooth technology, IrDA, home radio frequency, ultra-wideband technology and ZigBee technology. Details are as follows:
(1) Bluetooth technology is a short-range wireless communication technology that supports point-to-point and point-to-multipoint voice and data services. Its basic network structure is piconet. Its advantages are low power consumption, strong portability, simple integrated circuit and easy popularization. Bluetooth technology works in the global ISM frequency band of 2.45 GHz, eliminating the limitation of national boundaries, enabling short-distance interconnection and plug and play. In a very noisy radio environment, its advantages are more obvious. At present, it provides support for three general application fields using short-range wireless connection, namely data and voice access points, cable substitution and ad hoc networks.
(2) IrDA technology has the largest market share among several technologies at present. It uses infrared as the communication medium, supports point-to-point voice and data services at various rates, and is mainly used in embedded systems and devices.
(3) Home RF is an open industrial standard, which is used to realize wireless digital communication between PC and user electronic equipment in the home area.
(4) UWB technology is a new technology, and its concept is similar to radar. Its advantages of high performance and low power consumption will make it one of the strong competitors in the future market.
(5) ZigBee technology is a new short-distance, low-rate wireless network technology. It is a technical scheme between wireless tag technology and Bluetooth, and is mainly used for short-distance wireless connection.
Second, the wireless local area network (WLAN)
Wireless LAN mainly adopts IEEE802. 1 1 standard. By using electromagnetic waves in the air instead of traditional cables to transmit information, it can be used as an extension, supplement or replacement of wired networks. Comparatively speaking, WLAN has the following advantages:
(1) Mobility: The communication range is not limited by environmental conditions, and it can provide users with real-time ubiquitous network access function, so that users can easily obtain information.
(2) Flexibility: The networking mode of WLAN is flexible and diverse, and it is convenient to add, delete, move and modify devices.
(3) Economy: WLAN can be used in places where physical wiring is difficult or unsuitable, and the network can be put into use quickly, saving popularization costs.
It is the most popular type of wireless network at present, with a wide range of applications and many ways of application, but it can only be used for users or services that are not moving or moving slowly at present, and a wireless local area network suitable for high-speed movement may be developed in the near future. According to the application type, it can be divided into two categories, one is with fixed infrastructure, and the other is without fixed infrastructure. Wireless local area network without fixed infrastructure is also called Ad Hoc network, the most prominent of which is mobile Ad Hoc network. It has a good application prospect in military and civil fields, can be used quickly in any communication environment, and can respond to network topology changes in time. It is a network technology with good prospects at present and in the future.
Thirdly, wireless wide area network (WWAN)
Wireless WAN mainly adopts IEEE802.20 standard. It emphasizes fast mobility, and its connectivity can cover a wide geographical area. But its information rate is usually not very high, only 1 15 KB/s ... At present, the wireless WAN is mostly a digital mobile communication network used for mobile phones and data services. GSM mobile communication system and satellite communication system are commonly used, and 3G and 4G technologies also belong to wireless wide area network. This technology enables laptops or other devices to connect to the Internet anywhere within the coverage of cellular networks.
Four. Concluding remarks
The wireless network based on Wi-Fi technology not only greatly improves the bandwidth and coverage, but also transforms the wireless application based on Wi-Fi from the original "anytime, anywhere, free access" service to many rich wireless applications such as car wireless, wireless voice, wireless video, wireless campus, wireless medical, wireless city, wireless location and so on. In the future, wireless networks will play an important role in academic, manufacturing, warehousing and medical care. However, for wireless networks, priority should be given to solving the following problems: (1) Strengthening mobile device management (MDM) and security system; (2) Deploying large-scale voice and video wireless local area networks; (Is the WLAN controller installed inside or outside the enterprise? These problems are the most urgent to be solved, and also determine the role of wireless networks in the future.
Wireless network technology paper II
Speaking of the historical origin of wireless networks, it can be traced back to World War II fifty years ago, when the US Army used radio signals to transmit data. They developed a set of radio transmission technology and adopted a fairly high-intensity encryption technology, which was widely used by the US military and allied forces. This technology has inspired many scholars. 197 1 year, researchers at the university of Hawaii created the first radio communication network based on packet technology. This network, called ALOHNET, can be regarded as a fairly early wireless local area network (WLAN). It includes seven computers, spanning four Hawaiian islands in a two-way star topology, and the central computer is placed on Oahu. Since then, the wireless network was officially born.
From the earliest infrared technology to Bluetooth, which is highly anticipated, and even the most popular IEEE 802. 1 1(WiFi), wireless network technology is gradually maturing. But when it comes to industry influence, I'm afraid no one can match WiFi.
Wi-Fi (short for wireless fidelity) is an industrial standard of wireless network communication defined by IEEE (IEEE802. 1 1). The first version of Wi-Fi was published in 1997, which defined the MAC layer and the physical layer. The physical layer defines two wireless FM modes and one infrared transmission mode working in the ISM band of 2.4 GHz, and the total data transmission rate is designed to be 2Mbits. The communication between two devices can be carried out in a special way or under the coordination of a base station (BS) or an access point (AP).
The following describes the membership and structure of the Wi-Fi connection point network:
The station is the most basic part of the network.
Basic service set. The most basic service unit of the network. The simplest service unit can only contain two sites. Sites can be dynamically associated with basic service units.
Distribution system. The power distribution system is used to connect different basic service units. The media used by the distribution system is logically different from the media used by the basic service unit, although they may be physically the same media, such as the same radio frequency band.
Access point. The access point not only has the identity of an ordinary station, but also has the function of accessing the distributed system.
Extended service set. It consists of distribution system and basic service unit. This combination is logical, not physical-different basic service units may be geographically far apart. The distribution system can also use various technologies.
The gateway is also a logical component. Used to connect wireless LAN and wired LAN or other networks.
There are three kinds of media, the wireless media used by the site, the media used by the distribution system, and the media used by other LANs integrated with the wireless LAN. They may overlap each other physically. IEEE802. 1 1 is only responsible for addressing on the wireless medium used by the site. The addressing of distribution system and other local area networks is beyond the scope of wireless local area networks.
IEEE802. 1 1 does not specifically define the distribution system, but only defines the services that the distribution system should provide. The whole WLAN defines 9 services, among which 5 services belong to the tasks of distributed system, namely, association, disassociation, distribution, integration and reassociation. Four services belong to the tasks of the site, namely authentication, verification, privacy and MAC data transmission.
Simply put, WIFI is a network consisting of an AP (access point) and a wireless network card. AP is generally called a bridge or access point, which acts as a bridge between traditional wired LAN and wireless LAN, and also a bridge between wireless LAN and wireless LAN. Therefore, any PC equipped with wireless network card can share the resources of wired local area network or even wide area network through AP, and its working principle is equivalent to a hub or routing with a built-in wireless transmitter. Wireless network card is the client device responsible for receiving signals transmitted by AP.
Although WIFI wireless technology has encountered many difficulties on the way forward, with the progress of product technology and the unification of technical standards, WIFI will certainly bring people greater convenience and brighter prospects, and wireless network technology will also develop in a more mainstream direction.
Wireless Network Technology Paper III
I. Introduction
When people are about to enter the 2 1 century, the internet has unconsciously become an indispensable part of everyone's life, and it is used to query the required information, browse all kinds of news, and even query the travel route of the day. However, people want to do all these things, basically through wired networks. Most people are not familiar with the slow-developing wireless network, and if they want to use it in China at present, the cost is quite expensive. Therefore, due to some objective reasons, most people stay away from it and never even ask questions.
In fact, wireless network is a kind of progress and reform in the network age. It can make life more convenient and promote the progress of the whole society; So, in order to let those who don't know it or don't want to get close to it know more about it, let them get in touch with it, and even use it slowly, let's briefly introduce the wireless network from five aspects.
Second, the birth of wireless network.
From 1969, when the Internet was born in the United States, its history was not long. The following can be illustrated by a short story. The story began on August 30th of that year. The first "Interface Information Processor" manufactured by BBN Company, called IMP 1 for short, arrived at the University of California two days ahead of schedule. Cranlock was a professor who conducted this experiment at that time, with more than 40 engineers and graduate students. But at the beginning of 10, the second IMP2 was transported to the second node of ARPANET experiment, namely Stanford Research Institute (SRI).
After more than a year of intense research by hundreds of people, ARPANET remote networking experiment will be formally implemented soon. IMP 1 connected host is called sigma -7, which has been shipped to the University of California. The SRI host, named SDS 940, which communicates with it, also arrived at the same time. After one or two months of preparation, 10 realized the first two-computer communication experiment in the world that night. Professor Clanrock immediately ordered his research assistant, a student named Charlie Klein (English name: C. Kline) of the University of California, to sit in front of a terminal named IMP 1, and told him to put on headphones and a microphone to keep in close contact with another technician in charge of the operation of the SRI terminal at any time through long-distance telephone calls.
So the experiment began. According to Klein's memory at that time, his professor asked him to transmit five letters first, namely, L, O, G, I and N, which were used to confirm the transmission effect of packet switching technology. The professor instructs it, as long as three letters, L, O and G, are input, so that IMP 1 machine can send it out, and then SRI machine can automatically generate "in", and finally combine the five letters to realize it, namely: LOGIN. Under the guidance of the professor, with the cooperation of Klein and SRI terminal operator, at 22: 30, with excitement, C Klein began to type the first letter "L" on the keyboard, and then shouted into the microphone: "Did you receive that" L "?" The answer at the other end is: "Yes, I received' L'."
He continued to do the same job. ...
"Did you receive O?
"Yes, I received an' o'.
So step by step, suddenly appeared an unexpected result. IMP 1 instrument shows that the transmission system has crashed, and communication cannot continue. Professor Cranlock and his forty students ended their first communication experiment in the world. At that time, only the successful transmission of the letters L and O truly marked the real birth of the network. Historically, this happened as a witness to the birth of the Internet.
What about the birth of wireless networks? It can be traced back to World War II, when the United States was ahead of other countries in science and technology, whether in communication or network, so the US military adopted radio signals and used a set of radio transmission technology with high-intensity encryption protection function, and began their technological breakthrough on the battlefield. From this moment on, the wireless network was officially born.
Third, the concept and security of wireless network
(A) the concept
The so-called wireless network, as its name implies, is a global voice and data network that does not need to transmit through the medium of cable, and users can establish long-distance wireless connections. It is very similar to the use of wired networks, but the biggest difference is that except for the transmission medium: radio technology replaces the network cable, and it is also slightly different from wired networks in classification, including wireless personal network, wireless local area network and wireless metropolitan area network.
In wireless LAN, the common devices are: wireless network card, wireless bridge, wireless antenna, wireless router and other wireless devices. Once the local area network is established, the wireless network will have a certain radiation risk, which is even stronger than the wired network in time and scope. Therefore, in order to get as little radiation as possible, we should put the commonly used wireless routing and wireless AP away from the body and bedroom, and pay attention to avoid putting some wireless products too close to electronic products such as audio and television to prevent mutual interference from causing other radiation. In short, as long as we keep a certain distance from it, avoid the cumulative effect of staying in the wireless network environment for a long time, and develop good habits, then the auxiliary shooting of wireless network will not pose too much threat to human beings.
(2) Safety
When using wireless networks, security is of course very important. In terms of security, it is very different from wired network. The security of wireless networks can be grasped mainly from the following six aspects:
1. Use a strong password. Speaking of passwords, this is a very sensitive matter. A strong enough password can make violence impossible to eliminate. On the contrary, if the password strength is not enough, it will almost certainly damage your system. So you should not only set a password, but also be strong enough.
2. It is forbidden to broadcast the service set identifier (SSID). The SSID is actually the renaming of the wireless network. If it cannot be protected, the security risks will be very serious. At the same time, when configuring the wireless router, it is necessary to prohibit the broadcast of the service set identifier. Although it can't bring real security, it can at least reduce the threat, because many primary malicious attackers use scanning to find some vulnerable systems as their breakthrough. Once the function of service set identifier is hidden, the degree of damage is greatly reduced.
3. Adopt effective wireless encryption method. On the contrary, another dynamic wired security method is not very effective. Using free tools like aircrack, we can find out the vulnerabilities of encrypted wireless networks in a few minutes. Wireless network protection access is a common encryption standard at present. Of course, you can choose to use some more powerful and effective methods. After all, the struggle between encryption and decryption has been going on.
4. Use different types of encryption. Don't just rely on the wireless encryption mentioned above to ensure the overall security of the wireless network. Different types of encryption can improve system-level security and reliability. For example, OpenSSH is a good encryption option, which can provide secure communication between systems in the same network, even if it needs to pass through the Internet. Similar to the e-commerce website using SSL encryption technology. In fact, in order to achieve a more secure effect, it is recommended not to always change the encryption method.
5. Control the media access control address layer. That is, what we call MAC addresses, individual restrictions will not provide real protection. However, hiding the service set identifier of the wireless network and restricting the access of the media access control (MAC) address to the network can ensure that the network will not be interfered by major malicious attackers. In addition, this method can fully protect the whole system, whether it is malicious attacks by novices or strong destruction by experts, and ensure the safety of the whole system.
6. Monitor the activities of network intruders. As we all know, human beings use the Internet all the time. Therefore, intruders will attack your network at any time, so you need to track the development trend of attacks and how they connect to your network. In order to provide a better basis for security protection, you need to analyze the relevant information scanned in the log to find out the more favorable parts, so as to inform you in time when there are abnormal situations in the future. In short, with the progress of society and the constant renewal of science and technology, we need to remember the above ten points understandably and use them flexibly in the future.
Fourth, wireless network technology and application
At present, wireless network technology is not very popular in China. Compared with wired network, it is not very mature. However, today, in the wireless world, new technologies emerge one after another, and new terms are overwhelming. For example: from wireless local area network, wireless personal area network, wireless body area network, wireless metropolitan area network to wireless wide area network; From mobile ad hoc networks to wireless sensor networks and wireless mesh networks; From Wi-Fi to WiMedia, WiMAX from IEEE802. 1 1, IEEE802. 15, IEEE802. 16 to IEEE802.20 from fixed broadband wireless access to mobile broadband wireless access; From Bluetooth to infrared, HomeRF, UWB to ZigBee, GSM, GPRS, CDMA to 3G, Super 3G, 4G and so on.
In application, there are two main ways: GPRS mobile phone wireless network and wireless local area network. In a sense, GPRS mobile phone wireless network can be called the real network in the society at present. It mainly accesses the Internet through the mobile phone network, so as long as GPRS service is opened in your area, you can access the Internet anywhere. The latter, mainly compared with wired network, highlights its convenience, because it is a data transmission system realized by radio frequency technology (RF for short), which replaces the old annoying way of accessing the Internet through twisted copper wires; Besides the two mainstream modes mentioned above, there are three wireless network communication modes in China, namely, mobile TD-SCDMA, CDMA2000 and WCDMA. So in the future, as long as there is 3G network signal, you can access the Internet.
Verb (abbreviation of verb) employment prospect
A new type of industry will certainly bring a lot of influence to the society and push the whole society to a more stable pace. For example, in terms of employment, it has created a number of new jobs, such as 3G network engineers and wireless network optimization. In terms of communication, there have been surveys and wireless network tests. , thus reducing the employment pressure of the whole society. Moreover, in the case that the technical application of products produced under another wireless LAN standard has gradually become the mainstream of the wireless network market, the wireless network based on Wi-Fi technology has not only made a great breakthrough in bandwidth and coverage, but also in application, today's wireless network is no longer just for users to access the network anytime and anywhere, and even has been able to participate more in the service of industry informatization. As you can imagine, it is not a dream that wireless medical service, wireless campus, wireless city and other industries will become the mainstream of the future wireless network market.
Ending of intransitive verbs
With the continuous evolution of science and technology and the rapid development of wireless industry, wireless network will become a new force to promote the whole network market. In the foreseeable future, various and always-on intelligent terminal technologies will integrate all functions of entertainment, office, consumption, medical care, culture, education, life service and other industries to jointly serve our work and life, making it simpler and smarter. Let intelligent technology and wireless network be better and more closely combined, and let more and more innovative applications and new lifestyles enter the future society. Finally, let's usher in a wireless era of "everything is online" and "the network moves with people".