Rapid mobile communication technology rapid development process and trend
Radio mobile communication technology rapid development process and trend (Zhang Wei)
[Abstract] This article is divided into three parts: first explain the rapid development of wireless mobile communications and wired fixed communication; then
He has highlighted the rapid development of the wireless communication honeycomb network from simulation to the numbers and the future tendency to enter the third generation system;
Finally, the wireless satellite communication microwave communication is also accelerating the pace to continue to develop forward to play an important role.
[Key words] wireless communication; mobile communication; honeycomb network; satellite communication
1 Wireless mobile communication with wired fixed communication
Wired fixed communication and wireless mobile communications are often two components of the information infrastructure (NII / GII). near
In the past, they all advanced with a clear and fast pace, and they will be more rapidly developed after entering the new century.
Contribute. Traditional wired fixed communication network is "public switched telephone network" PSTN (Public Switch Telephone
NetWork, long-term maintenance has been stable and expanded, which has prompted people to universally load the fixed terminal phone. However, from 90
From the mid-era, the Internet internet has raised the traditional communication network of the world to be affected by an unprecedented impact. Vast
Communication users began to universally loaded computer, data communication has risen sharply every year, and its growth rate far exceeds traditional calls.
Each year growth rate. According to this moment, the total number of data information traffic in the world will be chased by the five years after entering the new century.
The total number of information traffic on the phone is available, and there will be more and more later. Therefore, the future communication transfer network will be based on data information.
Points for packet switching, and undertake the transfer of telephone communications, no longer use the original circuit exchange
(Circuit Switching), but still guarantees a business quality (QoS) indicator for the phone. With the improvement of computer technology and
Function plus, data communication will extend to multimedia communication including audio, video information. In this way, the future wired fixed pass
The letter network will be able to assume the unified communication network transmitted by all information services, which will be a large capacity communication network.
Wireless mobile communication network is mainly a cellular network of central countries, and each city is divided into several honeycombs.
Area,
Setting a radio base station, all mobile terminals and personal wireless mobile phones in the area are directly
Wireless lines are called wireless access (Wireless Access). Mobile communication is originally only mobile phone, recently
Like the cable network, allow mobile users to connect to the Internet, transfer data information, and improve the computer,
Multimedia communication containing audio, video information is also transmitted in the future. The mobile terminal passes through the wireless access to the base.
To the mobile communication switch center MSC (Mobile-Communication Switching Center), in addition to wireless lines
with
Outside another radio base of a honeycomb network, it is also connected to the urban exchange of wired fixed communication network. This means, wireless mobile communication
The network is connected to the city fixed communication network. Mobile terminals and personal portions with mobile terminals of the same honeycomb or the same city
Direct or personal mobile phones communicate directly, of course, can be turned on by a wireless mobile communication network. However, the wireless mobile communication network is limited to this city.
The honeycomb network, the honeycomb network of different cities still needs to be turned on by the national wired fixed communication network. Running mobile phones like a wireless mobile phone
In China or international communications, we must pass wireless access and then connected by a city fixed network. This shows that the wired fixed communication network is both
Associated all kinds of communication services from wired access, including the communication services required for PSTN users, but also assume various communication services for wireless access, so the total number of communications traffic in fixed network is extremely large, and will be added year by year Big, in the country of designing the future
When the wire fixing communication network is inevitable, it must be refined, considering high capacity and increases capacity year by year. This requires transmission lines and
Communication network internal equipment can be easily increased as needed.
In view of the fact that the time division TDM used in the past digital communication network, the digital system evolved from the PDH to SDH, but
The maximum number of times is difficult to improve, so that the communication network continues to increase the capacity "electronic bottleneck". Fortunately, fiber is used as
The transmission line has huge potential capacity to explore utilization. Moreover, from the mid-1990s, wave division multi-channel / intensive wave division
(WDM / DWDM) is put into commercial use on fiber optic lines, showing unparalleledity. So, the trunk line in the wired communication network is almost all
The unit uses the fiber and installs the wave division multiplex system, and the communication network is inside itself, in order to expand capacity in the future, it has begun to consider from electricity.
Net imported into an optical network, using various optical device / components based on WDM, to achieve wavelength routing
And exchange and other functions, so that the capacity of the network can be further increased.
For people using telephone communication, although the fixed terminal telephone in the past is reliable, it is portable with recent promotion.
Compared with the wireless mobile phone, users feel that they carry a mobile phone, one number, and can call the other party anytime, anywhere.
That is, the call is much flexible than the past fixed terminal. So in recent years, the sales volume of mobile communications mobile phones has increased dramatically. International speculation,
In less than 2010, the total number of mobile wireless mobile phones in all world users will be equal to the total number of fixed-line terminals, but the user needs
When you call the phone, you are more happy to use your phone. Now the wireless mobile communication network not only provides a call, but also try to make a portable computer
Interworking data information and even multimedia communication, only because of the limited radio spectrum resources, wireless mobile communication can provide each path
The frequency band width of the signal is not like wired fixed communication. Therefore, in the case of a wide communication business, it is necessary to use a wide bandwidth.
For example, the user Internet needs Internet / WWW for a long time to provide special large amount of data information, or the user needs' to watch a specific at home.
High quality entertainment TV programs or movie films use "on-demand TV / movie" VOD / MOD business, it is necessary to use "wired
Access.
In summary, there are two extremely important predictions for the development of communications business in less than ten years: one is about 2005
The total number of data information traffic in the world is chasing the total number of traditional telephone traffic, and then forever; the second is about 2010
The total number of wireless mobile communications users in the world is increased to the total number of traditional wired fixed communication users. This wired fixed communication network
The capacity will become bigger and larger, and the mobile phone of the wireless mobile communication network is increasingly common. In the future, the two types of communication network technologies will continue together.
-Rapid development.
2 Honeycomb network from simulation to the number, will enter the third generation
One of the basic and most important one of wireless mobile communications is to use the honeycomb network. It avoids a city to use high-power wireless
Electric launch pad, cover the old idea of 40km area in diameter, and divide a city in the shape of a honeycomb network into a six-angle mutually close to each other
Shape (Cell), each zone can be less than 1 km. Set up a radio base BS in the center of such a honeycomb area (Base
Station, small transmit power, mobile phone with all mobile terminal MS (MobileStation) or personal portable
Always get in touch at any time. When a MS is moved from a zone to the neighborhood, the BS contact with the neighboring zone is changed, saying "handover" is "overworked". The wavelength used by a certain area is different from the wavelength of the neighboring zone BS, but with the wavelength of the second zone can be the same, called
"Frequency reuse" does not cause interference, this is the advantage of honeycomb network, saving radio spectrum resources. In the early 1980s,
The honeycomb network mobile communication starts commercial, then use analog calls, due to the progress of the integrated circuit, but also due to voice coding and digital pass
The development of letter technology is very successful. By the second half of the 1980s, the honeycomb network developed to digital, called the second generation ZG (Second
In the transition, mobile phones can be used in dual mode, which can be used for simulation phones, and can be used in digital telephones. At that time
European has standard organizational GSM (GROUPE Special Mo-Bile), and later in the 900MHz spectrum generally applied second-generation
GSM (Global System for Mobile Communications). Digital mobile phone uses more time
Site "Time Division Multiple Access). In the mid-1990s," Code Division Multiple Access "CDMA
(Code)
Division Multiple AC- CESS, also in the mid-1990s, US $ 14OMHz width of 1850-1990MHz
of
Spectrum for "Personal Communication Service" for "Personal Communication Service", these have been continuous
By the late 1990s, the continuous development momentum was maintained.
During the period of 2G system technology, the third-generation mobile communication 3G (Third "started internationally
The prospect of generation is necessary to use the foreseeable advanced technologies, but also take care of the system equipment that has been installed.
The standards recognized all over the world are generally referred to as IMT-2000 (International MobileEletEleCommunication).
Prepare
The 2000 MHz spectrum was used to start trial in 2000. This 3G system not only keeps a mobile phone, but also pays great attention to the number of development.
According to communication, the wireless system and wired communication network have valued data transmission, including Internet / Internet regulations IP and broadband services.
Multimedia communication with a data rate is 2Mb / s. International Standards Organization has reviewed the radio transmission plan submitted by countries,
Including my country's program, there is a frequency division of Duplency FDD (Frequency Duplex) CDMA, TDMA, and sometimes `divided duplex TDD (Time
CDMA of Division Duplex. It is always impossible to make wireless communication in terms of performance, cost and capacity.
In wireless digital mobile communication, in order to sufficiently save the spectrum, speech coding is very heavy
want. This is very different from the wired communication, and the wired digital telephone uses a pulse code to modulate the PCM, 64kb / s per channel, or adaptive pulse code
Modulate the AD-PCM, 32kb / s per way, is not difficult to communicate network capacity. Wireless communication voice code, from early "linear"
Predicting Coding "Linear Predictive Coding," code excitation linear forecast "in the 1980s CELP
(Code Excited Linear pre-Diction), the number rate of each voice drops to 5 to 13kb / s. At the same time, in the code
In the process, it is also necessary to overcome the radio wave propagation process caused damage and background noise to ensure the quality of the call. At the 3G system,
To consider the audio and video of the audio and video required for multimedia communication, the spectrum is saved and guaranteed to communicate.
Each radio is generally necessary to set a few sets of RF Transceiver. Now transition from simulation to numbers
Lamp, will make full use of digital signals to process DSP and dedicated large-scale integrated chip ASIC, and tend to use more and more new types
Software, leading to programmable, allowing a variety of air interface standards.
The base will use broadband linear power amplification and broadband RF devices to facilitate increasing digital content, making digital processing as close as possible to the antenna.
Many radio frequency are simultaneously processed, and the software completes more features. Since digital mobile communication supports multiple users with CDMA or
TDMA multiple access communication, digital can reduce the number of radio transceivers, and can be processed in a wideband of the same frequency band
Higher frequency processing, from the baseband to the intermediate frequency, and the radio frequency is used to use digital processing. When the base uses the programmable device like this,
They are called "Software" (Software.ra-DIO), which is quite flexible, and allows the base equipment easier to match.
"Smart Antenna or Intelligent Anten-NA). Mobile terminals and wireless phones will also tend to
Software radio. When the business and standard techniques have changed, software radio can quickly adapt to new technologies and do not need to be replaced.
Equipment, thus the investment cost can be reduced.
Additional digital signal processing can cause wireless communication intelligent antenna technology to achieve advantageous development. Intelligent antenna needs
Use multiple antennas. The base tends to have several orientation antennas, and each of the sectors, the wireless access of mobile terminals in the area.
It is particularly advantageous, it is also possible to make multiple beam shots through the adaptive process to quickly change to achieve the best pore gain, diversity increase
Benefits, and curb interference, leading to performance improvements. The receiving antenna is adopted by two antenna branches, there is sufficient space in space,
Get the benefits of spatial diversity, if there is only one wireless, the use of polarization diversity can also be beneficial. In adaptive intelligent antenna,
Send multiple antennas to make more benefits. For TDMA systems, intelligent wireless can increase communication capacity, by reverse line
The signal transmitted is processed, and the beam adjustment of the forward line is adjusted. For CDMA systems, all mobile terminals are used
The same band, just the different coding. To 3G system, users can specify special symbols such as using higher data rates (Pilot
Symbol) to control adaptive antenna processing to reduce interference between users, thereby increasing communication capacity, that is, several users
It is still allowed to use high-speed data.
The wireless mobile communication network is sometimes necessary to determine a mobile terminal or individual in a certain reason for public safety.
Move to geographic locations for a time, called geoloca-tion. There is now an independent handheld device
Entering the equipment, using the Global Positioning System (GPS, GLOBAL POSITIONING SYSTEM), moving individuals at outdoor
Your own location. In the future, enter the 3G era, the personal mobile wireless mobile phone itself may accompany the positioning function, it is governing the assistance
Lower positioning, do not have to carry separate GPS handlers. That is, the new mobile communication mobile phone attachment assistance
AGPS (Assisted GPS), measure yourself, or even indoors. Communication mobile phone is available when needed
The situation does not have to be continuously tracked with GPS satellites by the communication phone itself. The honeycomb network 3G system switches the wired network to the future, focusing on providing data communication as high as possible. Honeycomb net
It is also necessary to provide asymmetric digital transmission. As the asymmetrical digital subscriber line ADSL of the cable network, the radio station to the user's direction
Provide higher rate data transmission. The cable network is in the switch to set up multi-carrier discrete polyphones (DMF, Discrete
Multi-Tone) equipment, and the wireless network is in the abutment of multi-carrier trafficfield multiplex (OFDM, ORTHOGONAL)
FREQUENCY DIVISION MULTIPLEX Equipment, which requires a lot of information about the mobile user on the Internet
want.
3 Satellite communications and microwave communication have an important role
In addition to most of the city's honeycomb net, wireless mobile communication, as well as satellite communication, large
Have development prospects. Synchronous satellites have proved more reliable for fixed communication and broadcasting, and it can also advantageously provide remote movement.
Communication, low orbit, medium orbit satellite communication. If the technology, equipment, the cost is in-depth research, it can still be actually active.
Plays the global personal mobile communication. The same temperature layer (flat flow layer) wireless communication has been proposed, such as continuing to study,
There is a unique role in fixed communication and mobile communications. In addition, wireless fixed communication includes people's well-known microwave digital relay communication
And recently advocated wireless user loop (WSL, Wireless Subscriber Loop, very applicable in less population, it
We have the advantages of rapid construction and less investment compared to the construction of fiber optic cables and wireline users. Millimeter wave radio
Communication and wireless infrared communication have been installed in multiple installation tests, which proves to be good for short-range communications. In short, there are many actual internationalities.
The use and test experience shows that there are many wireless communication advantages, deserve to expand the actual use range. It can be asserted that after entering the new century,
Wireless communication will have to develop and mutually cooperate with wired communication, which is worthy of two components of the information infrastructure.
Satellites running in synchronous tracks have provided reliable international communication and television spread, enjoying a reputation. In recent years, it has been strengthened, especially
Its transponder, transponder, relaxing transmission band, increase transmit power, improves antenna efficiency, even
Install ATM equipment, expand business functions, so that the ground application is increasing. An application is installed on the ground "very small aperture
The antenna "satellite station, called VSAT, providing convenience for the wide-area private communication of large enterprises. Synchronous satellites may also be available on the ground
Long-distance mobile communication, but the ground mobile terminal requires a larger pair of star antennas, and the city center of the high-rise forest
It is difficult to broadcast. To this end, the global mobile communication of the ground has been developed another low orbit, hundreds from hundreds to one thousand kilometers away.
Dozens of mobile satellites, called Low Earth OR-bit. I have developed the track, about 10,000 kilometers away from the ground.
Ten mobile satellite, called MEO (Medium Earth Orbit). [Accordingly, it is 36,000km from the ground, and
Three satellites running synchronously, called geo (Geostational Earth OR-BI)]. Although recent LEO system
IRIDIUM will be frustrated shortly after the open commercial use, and the other system GlobalStar is opening up commercially, and it may be smooth.
But you should be treated calmly. The theory and technology of these Leo / Meo global wireless mobile communication systems is correct, but operators
Conditions of user needs, mobile phones and costs, and problems that are not expensive to users, it seems to be pre-considered
Not thoughtful enough. If you can carefully learn experience, carefully analyze the cause, it is likely to be a complete success, we can warmly look forward to a good future. Wireless fixed communication is also developed forward, fully utilizing wireless unique advantages, but wireless communication is received by radio frequencies
Restrictions on spectral resources, in order to continue to develop applications, we must consider increasing the frequency or shortening the use of wavelengths, ie from microwave (cm).
Wave) extends to millimeter wave, or even infrared waves. In such an extension process, there will be a new electric wave propagation problem and device asking.
Questions, must be properly resolved one by one, should be supported and encouraged by all parties.
Excerpted from "mobile communication"