作业帮跪求中英文对照有关CDMA的文章5000字
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跪求中英文对照有关CDMA的文章5000字
CDMA is the English abbreviation for Code Division Multiple Access (Code Division Multiple Access), it is digital technology at a branch - Spread-spectrum communication technology has developed a new and sophisticated wireless communications technology. CDMA technology is based on the principle of spread spectrum technology, soon to be sent must have the information signal bandwidth data, with a bandwidth much larger than signal bandwidth, high-speed pseudo-random code modulation, so that the bandwidth of the original data signals to be extended, and then by the carrier modulation and sent. Receiver use the same pseudo-random code, and receive bandwidth for the associated signal processing, wideband signal put into the original information of the narrowband data signal that is de-spread in order to achieve information and communication.
[Edit this paragraph] CDMA technical background
CDMA technology from the human higher-quality wireless communications needs. During the Second World War due to the war needs of the research and development of CDMA technology, its original idea is to prevent the enemy of one's own communications interference, during the war are widely used in military anti-jamming communications, and later updated by QUALCOMM Incorporated as commercial cellular telecommunications technology. In 1995, the first commercial CDMA system is running after, CDMA technology's many advantages in theory, in practice the test, which in North America, South America and Asia and other places have been rapidly promoted and applied. Many countries and regions worldwide, including Hong Kong, China, Korea, Japan, the United States have been built there is CDMA commercial network. At the United States and Japan, CDMA become the main mobile communication technologies. In April of this year, Korea has 60% of the population become the CDMA users. In Australia to host the 27th Olympic Games, CDMA technology is playing an important role.
[Edit this paragraph] CDMA technology standards
Standardization of CDMA technology has gone through several stages. CdmaOne IS-95 series of standards are the first issued the standards really been widely used in the world's first CDMA standard is IS-95A, the standard support encoding 8K voice services. And then published separately 13K voice encoder TSB74 standards, to support 1.9GHz the CDMA PCS system STD-008 standards, one of 13K encoded voice quality of service have been very close to cable telephony voice quality. With the mobile communications business needs of data growth, in February 1998, QUALCOMM Incorporated announced the IS-95B standards for basic CDMA platform. IS-95B can provide CDMA system performance, and increase the user's mobile communications equipment data traffic, providing 64kbps data service support. Subsequently, cdma2000 become narrow-band CDMA system, the transition to third generation system standards. cdma2000 standards at the early stage of research, put forward the 1X and 3X development strategy, but later studies have shown that, 1X and 1X-enhanced technology on behalf of the future direction of development.
CDMA technology, standardization, and promote this technology in applications worldwide. At present, the United States, South Korea, Japan and other countries, CDMA technology has gained a larger scale applications. In some European countries, some operators have also built a CDMA network. According to CDG (World CDMA Development Group) statistics, CDMA users by the end of 1996 only 1,000,000; to March 1998 has been the rapid growth to 10 million; As of September 1999, the number of users has more than 40 million. Early in 2000 the global CDMA mobile phone users has exceeded the total number of 50,000,000, the number of users in a year growth rate of 118%. CDG said the CDMA market in Asia has become the main engine of growth in Asia the number of CDMA users grew 88 percent from a year ago, reaching 28 million. The growth rate of the United States is a whopping 143 percent, reaching 16.5 million, but the absolute number of users is lower than in Asia, at the Asia-Pacific region, Hong Kong, China, Japan, Korea, Australia, Thailand, India, the Philippines, New Zealand, Bangladesh and many other countries and regions have built commercial CDMA network, the number of users has more than 21 million. Growth rate is the third Central and South America, CDMA subscribers to reach 5,000,000. CDG has also said that in the future global CDMA market, mainland China the largest growth potential, it is estimated that the mainland Chinese market in 2003 the number of users can reach 40 million.
CDMA mobile communication technology are the development direction. At 2G stage, CDMA and GSM Enhanced IS95A up in the technical system in the same generation products, to provide roughly the same business. However, CDMA technology has its unique feature, at the call quality, fewer dropped calls, low, health and other aspects of environmental protection has significant characteristics. At 2.5G stage, CDMA2000 1X RTT and GPRS technically have been significantly different, at transfer rate of 1X RTT is higher than on GPRS, carrying on business in the new 1X RTT sophisticated than GPRS may provide more rapid rate of new business . From 2.5G to 3G technologies on the institutional transition, CDMA2000 1.X to CDMA20003.X than GPRS to WCDMA transition more smooth transition.
[Edit this paragraph] CDMA by an edge
(1) system capacity
Theoretically, the same frequency in the use of resources, CDMA mobile network capacity than the analog network 20 times, the actual use than the analog network 10 times larger than the GSM, to a large 4-5 times.
(2) system capacity and flexible configuration
In the CDMA system, the increase in the number of users equal to the increase in background noise, resulting in a decline in voice quality. However, the number of users and unlimited, the operator may be at capacity and trade-off between voice quality. In addition, many among the community according to traffic and interference automatically balanced.
The characteristics and mechanism of CDMA-related. CDMA is a self-interference system, all mobile users occupy the same bandwidth and frequency, an analogy, think of the bandwidth of a large house, all the people will enter only the big house. If they use a completely different language, they can clearly hear the voices of his companions but only by some from other people's interference. Here, the house air can be imagine broadband carrier, and different languages were used as encoding, we can continuously increase the user until the entire background noise restrict us. If we can control the user's signal strength, while maintaining high-quality calls at the same time, we can accommodate more users.
(3) better voice quality
TDMA channel structure can only support a maximum of 4Kb voice encoder, it can not support more than 8Kb voice encoder. And the structure of CDMA can support voice 13KB encoder. Therefore can provide better call quality. CDMA vocoder system can dynamically adjust data transfer rate, and in accordance with the appropriate threshold level choose a different class to launch. At the same time limits under the door to changes in background noise changes, so even if the background noise in the larger case, you can get a better call quality. In addition, TDMA using a hardware method of the transfer, the user can clearly feel the calls stopped at a user-intensive, intensive town in the base station, which is particularly evident on the discontinuity, because in this region will happen every 2 minutes to 4 times the transfer of the case. The CDMA system, "dropped calls" the situation significantly reduced, CDMA systems use soft-switching technology, "first connect again disconnect" so hard to switch completely overcome the shortcomings of easily dropped calls.
(4) frequency planning easy (?)
User to distinguish between different code sequences, so not the same CDMA carrier in the adjacent community use, network planning flexibility, easy expansion.
Although the CDMA system, frequency planning easy, but there is a CDMA system, the short PN code of planning, and short code PN planning compared to frequency planning is not necessarily easier.
The whole planning CDMA is not easy. In contrast, compared with GSM systems to more complex.
(5) to build low-cost Net
CDMA system has a huge capacity, the work of low-frequency than GSM, and so in CDMA planning, CDMA station spacing generally higher than that of GSM sparse. Savings could be better, therefore the cost of network building.
(6) network of green environmental protection
Technology system average maximum transmitting power transmitting power
GSM 125 mW 2 W
CDMA 2 mW 200 mW
Data can be seen from the above CDMA mobile phone GSM mobile phone are the average transmitting power of 2 / 125
CDMA mobile phone a more green environmental protection.
[Edit this paragraph] CDMA technology holding point
1. CDMA is a spread spectrum communication, spread spectrum communication with him the following characteristics:
(1) anti-interference ability. This is the basic characteristics of spread spectrum communication, all communications are second to none.
(2) broadband transmission, anti-fading ability.
(3) because of the use of broadband transmission, in the channel transmission power ratio of useful signal interference signal power is much lower, so if the signal hidden in noise; that is, if the power density is relatively low, there is in favor of covert signals.
(4) the use of spreading codes to obtain the relevance of the user's information, the ability of anti-interception.
(5) multiple users simultaneously receiving, sending simultaneously.
2. In CDMA spread spectrum communication system, because the key to the adoption of new technology with some new features:
(1) the use of a variety of ways diversity. In addition to the traditional outer space diversity. Yes because of broadband transmission frequency diversity played a role, while at the base station and mobile station using a RAKE receiver technology, which is equivalent to the role of time diversity.
(2) use of voice-activated technology and technology sector. Since CDMA capacity of the system directly related to the disruption related to the use of voice activation and technology sector can reduce the interference, can increase overall system capacity.
(3) use of mobile station assisted soft handoff. It can be achieved through the seamless switch to ensure the continuity of the call, reducing the possibility of dropped calls. Switch region in the mobile station through a number of base station diversity reception of signals, can reduce its transmission power, thereby reducing interference from the surrounding base stations, so that there is conducive to improve the reverse Luen Road capacity and coverage.
(4) use of power control technology, this reduces the transmission power heijunka.
(5) has a soft capacity characteristic. Can be at the peak traffic by improving the error frame rate can be used to increase channel number. When the adjacent community of one light one heavy load, the load weight by reducing the community can pilot the transmitter power, so that the edge of the user community because of the lack of pilot strength and switch to the adjacent community, so that the burden-sharing.
(6) a good compatibility. CDMA bandwidth because of large power distribution at a broad spectrum, the power, then the density is low, narrow-band interference simulation system of small, so the two can coexist. That is, good compatibility.
(7) CDMA high frequency of utilization, without frequency planning, which is one of the characteristics of CDMA.
(8) CDMA efficient voice coding OCELP. Voice coding technology in digital communications are an important topic. OCELP is the use of vector quantization code table difference signal, and in accordance with the degree of voice-activated to produce a variable output rate signal. This sort horse five approaches were considered as currently the most efficient coding techniques, while ensuring there is better voice quality under the premise of greatly improving the capacity of the system. This vocoder has 8kbit / S and 13kbit / S two-rate sequences. 8kbit / S sequences from 1.2kbit / s to 9.6kbit / s variable, 13kbit / S sequences from 1.8kbt / s to 14.4kbt / S variable. Recently, a type encoder 8kbit/sEVRC come out, also has 8kbit / s vocoder characteristics of large capacity, voice quality has been noticeably improved.
[Edit this paragraph] What is a CDMA cell phone?
Code-DivisionMultipleAccess are the initials, the full name of Code Division Multiple Access, are commercial in recent years been applied to a digital interface technology. It has a high frequency of utilization, and low-power mobile phone. China Unicom will be launched early next year belong to 2.5-generation CDMA technology. CDMA-based mobile phone refers to [2] networks, mobile communication terminals.
[Edit this paragraph] CDMA mobile phone advantages
Compared with the GSM mobile phone, CDMA mobile phone has the following advantages: First, CDMA mobile phone can be said to be truly green cell phone, it launched a very small power (2mw), but we are now used in GSM mobile phone (power 125mw) 1 / 60, television screen or even lower than the radiation power; two, CDMA mobile phone employs advanced switching technology - soft-switching technology (that is, switching is a good follow-up after the first interruption), the CDMA mobile phone calls can be comparable with fixed telephone, and no GSM cell phone dropped the situation; three, use the CDMA network operator investment required is relatively less, which for the CDMA mobile phone tariff downward reserved space; four, in order to expand the use of frequency-based communication as a modulation and multiple access means of communication, and its high-capacity simulation technology more than 10 times, more than about 4 times the GSM network; Friday, more importantly, the CDMA-based broadband technology allows video applications in mobile communications become possible, so that can only be called from a cell phone and send short message services, such as narrow toward broadband multimedia applications.
Classification of mobile communication technology
Mobile communication system has a variety of classification methods. Signal such as by nature, can be classified into analog, digital; by modulation points, can be divided into frequency modulation, phase modulation, amplitude modulation; many sites connected by way of points, can be divided into:
Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA).
At present, China Unicom, China Mobile used in GSM mobile phone network is used in FDMA and TDMA combination of two ways. Analog GSM mobile phones than there is a great advantage, but only on spectral efficiency at Analog systems are 3 times, with limited capacity; on the voice quality is also very difficult to achieve the level of fixed line telephone; TDMA terminal access speed can only reach the highest 9.6kbit / s; TDMA system without soft-switching function, and thus easy to dropped calls, the impact of service quality. Therefore, TDMA is not a modern cellular mobile communications the best wireless access, and CDMA multiple access technology is completely suited to modern mobile communication networks required by high-capacity, high-quality, integrated services, soft-switch and so on, is being more and more and more operators and users of all ages.
At present, China Unicom's CDMA business has. However, beginning October 1, 2008 Unicom's CDMA business to China Telecom
[Edit this paragraph] CDMA technical background
CDMA technology from the human higher-quality wireless communications needs. During the Second World War due to the war needs of the research and development of CDMA technology, its original idea is to prevent the enemy of one's own communications interference, during the war are widely used in military anti-jamming communications, and later updated by QUALCOMM Incorporated as commercial cellular telecommunications technology. In 1995, the first commercial CDMA system is running after, CDMA technology's many advantages in theory, in practice the test, which in North America, South America and Asia and other places have been rapidly promoted and applied. Many countries and regions worldwide, including Hong Kong, China, Korea, Japan, the United States have been built there is CDMA commercial network. At the United States and Japan, CDMA become the main mobile communication technologies. In April of this year, Korea has 60% of the population become the CDMA users. In Australia to host the 27th Olympic Games, CDMA technology is playing an important role.
[Edit this paragraph] CDMA technology standards
Standardization of CDMA technology has gone through several stages. CdmaOne IS-95 series of standards are the first issued the standards really been widely used in the world's first CDMA standard is IS-95A, the standard support encoding 8K voice services. And then published separately 13K voice encoder TSB74 standards, to support 1.9GHz the CDMA PCS system STD-008 standards, one of 13K encoded voice quality of service have been very close to cable telephony voice quality. With the mobile communications business needs of data growth, in February 1998, QUALCOMM Incorporated announced the IS-95B standards for basic CDMA platform. IS-95B can provide CDMA system performance, and increase the user's mobile communications equipment data traffic, providing 64kbps data service support. Subsequently, cdma2000 become narrow-band CDMA system, the transition to third generation system standards. cdma2000 standards at the early stage of research, put forward the 1X and 3X development strategy, but later studies have shown that, 1X and 1X-enhanced technology on behalf of the future direction of development.
CDMA technology, standardization, and promote this technology in applications worldwide. At present, the United States, South Korea, Japan and other countries, CDMA technology has gained a larger scale applications. In some European countries, some operators have also built a CDMA network. According to CDG (World CDMA Development Group) statistics, CDMA users by the end of 1996 only 1,000,000; to March 1998 has been the rapid growth to 10 million; As of September 1999, the number of users has more than 40 million. Early in 2000 the global CDMA mobile phone users has exceeded the total number of 50,000,000, the number of users in a year growth rate of 118%. CDG said the CDMA market in Asia has become the main engine of growth in Asia the number of CDMA users grew 88 percent from a year ago, reaching 28 million. The growth rate of the United States is a whopping 143 percent, reaching 16.5 million, but the absolute number of users is lower than in Asia, at the Asia-Pacific region, Hong Kong, China, Japan, Korea, Australia, Thailand, India, the Philippines, New Zealand, Bangladesh and many other countries and regions have built commercial CDMA network, the number of users has more than 21 million. Growth rate is the third Central and South America, CDMA subscribers to reach 5,000,000. CDG has also said that in the future global CDMA market, mainland China the largest growth potential, it is estimated that the mainland Chinese market in 2003 the number of users can reach 40 million.
CDMA mobile communication technology are the development direction. At 2G stage, CDMA and GSM Enhanced IS95A up in the technical system in the same generation products, to provide roughly the same business. However, CDMA technology has its unique feature, at the call quality, fewer dropped calls, low, health and other aspects of environmental protection has significant characteristics. At 2.5G stage, CDMA2000 1X RTT and GPRS technically have been significantly different, at transfer rate of 1X RTT is higher than on GPRS, carrying on business in the new 1X RTT sophisticated than GPRS may provide more rapid rate of new business . From 2.5G to 3G technologies on the institutional transition, CDMA2000 1.X to CDMA20003.X than GPRS to WCDMA transition more smooth transition.
[Edit this paragraph] CDMA by an edge
(1) system capacity
Theoretically, the same frequency in the use of resources, CDMA mobile network capacity than the analog network 20 times, the actual use than the analog network 10 times larger than the GSM, to a large 4-5 times.
(2) system capacity and flexible configuration
In the CDMA system, the increase in the number of users equal to the increase in background noise, resulting in a decline in voice quality. However, the number of users and unlimited, the operator may be at capacity and trade-off between voice quality. In addition, many among the community according to traffic and interference automatically balanced.
The characteristics and mechanism of CDMA-related. CDMA is a self-interference system, all mobile users occupy the same bandwidth and frequency, an analogy, think of the bandwidth of a large house, all the people will enter only the big house. If they use a completely different language, they can clearly hear the voices of his companions but only by some from other people's interference. Here, the house air can be imagine broadband carrier, and different languages were used as encoding, we can continuously increase the user until the entire background noise restrict us. If we can control the user's signal strength, while maintaining high-quality calls at the same time, we can accommodate more users.
(3) better voice quality
TDMA channel structure can only support a maximum of 4Kb voice encoder, it can not support more than 8Kb voice encoder. And the structure of CDMA can support voice 13KB encoder. Therefore can provide better call quality. CDMA vocoder system can dynamically adjust data transfer rate, and in accordance with the appropriate threshold level choose a different class to launch. At the same time limits under the door to changes in background noise changes, so even if the background noise in the larger case, you can get a better call quality. In addition, TDMA using a hardware method of the transfer, the user can clearly feel the calls stopped at a user-intensive, intensive town in the base station, which is particularly evident on the discontinuity, because in this region will happen every 2 minutes to 4 times the transfer of the case. The CDMA system, "dropped calls" the situation significantly reduced, CDMA systems use soft-switching technology, "first connect again disconnect" so hard to switch completely overcome the shortcomings of easily dropped calls.
(4) frequency planning easy (?)
User to distinguish between different code sequences, so not the same CDMA carrier in the adjacent community use, network planning flexibility, easy expansion.
Although the CDMA system, frequency planning easy, but there is a CDMA system, the short PN code of planning, and short code PN planning compared to frequency planning is not necessarily easier.
The whole planning CDMA is not easy. In contrast, compared with GSM systems to more complex.
(5) to build low-cost Net
CDMA system has a huge capacity, the work of low-frequency than GSM, and so in CDMA planning, CDMA station spacing generally higher than that of GSM sparse. Savings could be better, therefore the cost of network building.
(6) network of green environmental protection
Technology system average maximum transmitting power transmitting power
GSM 125 mW 2 W
CDMA 2 mW 200 mW
Data can be seen from the above CDMA mobile phone GSM mobile phone are the average transmitting power of 2 / 125
CDMA mobile phone a more green environmental protection.
[Edit this paragraph] CDMA technology holding point
1. CDMA is a spread spectrum communication, spread spectrum communication with him the following characteristics:
(1) anti-interference ability. This is the basic characteristics of spread spectrum communication, all communications are second to none.
(2) broadband transmission, anti-fading ability.
(3) because of the use of broadband transmission, in the channel transmission power ratio of useful signal interference signal power is much lower, so if the signal hidden in noise; that is, if the power density is relatively low, there is in favor of covert signals.
(4) the use of spreading codes to obtain the relevance of the user's information, the ability of anti-interception.
(5) multiple users simultaneously receiving, sending simultaneously.
2. In CDMA spread spectrum communication system, because the key to the adoption of new technology with some new features:
(1) the use of a variety of ways diversity. In addition to the traditional outer space diversity. Yes because of broadband transmission frequency diversity played a role, while at the base station and mobile station using a RAKE receiver technology, which is equivalent to the role of time diversity.
(2) use of voice-activated technology and technology sector. Since CDMA capacity of the system directly related to the disruption related to the use of voice activation and technology sector can reduce the interference, can increase overall system capacity.
(3) use of mobile station assisted soft handoff. It can be achieved through the seamless switch to ensure the continuity of the call, reducing the possibility of dropped calls. Switch region in the mobile station through a number of base station diversity reception of signals, can reduce its transmission power, thereby reducing interference from the surrounding base stations, so that there is conducive to improve the reverse Luen Road capacity and coverage.
(4) use of power control technology, this reduces the transmission power heijunka.
(5) has a soft capacity characteristic. Can be at the peak traffic by improving the error frame rate can be used to increase channel number. When the adjacent community of one light one heavy load, the load weight by reducing the community can pilot the transmitter power, so that the edge of the user community because of the lack of pilot strength and switch to the adjacent community, so that the burden-sharing.
(6) a good compatibility. CDMA bandwidth because of large power distribution at a broad spectrum, the power, then the density is low, narrow-band interference simulation system of small, so the two can coexist. That is, good compatibility.
(7) CDMA high frequency of utilization, without frequency planning, which is one of the characteristics of CDMA.
(8) CDMA efficient voice coding OCELP. Voice coding technology in digital communications are an important topic. OCELP is the use of vector quantization code table difference signal, and in accordance with the degree of voice-activated to produce a variable output rate signal. This sort horse five approaches were considered as currently the most efficient coding techniques, while ensuring there is better voice quality under the premise of greatly improving the capacity of the system. This vocoder has 8kbit / S and 13kbit / S two-rate sequences. 8kbit / S sequences from 1.2kbit / s to 9.6kbit / s variable, 13kbit / S sequences from 1.8kbt / s to 14.4kbt / S variable. Recently, a type encoder 8kbit/sEVRC come out, also has 8kbit / s vocoder characteristics of large capacity, voice quality has been noticeably improved.
[Edit this paragraph] What is a CDMA cell phone?
Code-DivisionMultipleAccess are the initials, the full name of Code Division Multiple Access, are commercial in recent years been applied to a digital interface technology. It has a high frequency of utilization, and low-power mobile phone. China Unicom will be launched early next year belong to 2.5-generation CDMA technology. CDMA-based mobile phone refers to [2] networks, mobile communication terminals.
[Edit this paragraph] CDMA mobile phone advantages
Compared with the GSM mobile phone, CDMA mobile phone has the following advantages: First, CDMA mobile phone can be said to be truly green cell phone, it launched a very small power (2mw), but we are now used in GSM mobile phone (power 125mw) 1 / 60, television screen or even lower than the radiation power; two, CDMA mobile phone employs advanced switching technology - soft-switching technology (that is, switching is a good follow-up after the first interruption), the CDMA mobile phone calls can be comparable with fixed telephone, and no GSM cell phone dropped the situation; three, use the CDMA network operator investment required is relatively less, which for the CDMA mobile phone tariff downward reserved space; four, in order to expand the use of frequency-based communication as a modulation and multiple access means of communication, and its high-capacity simulation technology more than 10 times, more than about 4 times the GSM network; Friday, more importantly, the CDMA-based broadband technology allows video applications in mobile communications become possible, so that can only be called from a cell phone and send short message services, such as narrow toward broadband multimedia applications.
Classification of mobile communication technology
Mobile communication system has a variety of classification methods. Signal such as by nature, can be classified into analog, digital; by modulation points, can be divided into frequency modulation, phase modulation, amplitude modulation; many sites connected by way of points, can be divided into:
Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA).
At present, China Unicom, China Mobile used in GSM mobile phone network is used in FDMA and TDMA combination of two ways. Analog GSM mobile phones than there is a great advantage, but only on spectral efficiency at Analog systems are 3 times, with limited capacity; on the voice quality is also very difficult to achieve the level of fixed line telephone; TDMA terminal access speed can only reach the highest 9.6kbit / s; TDMA system without soft-switching function, and thus easy to dropped calls, the impact of service quality. Therefore, TDMA is not a modern cellular mobile communications the best wireless access, and CDMA multiple access technology is completely suited to modern mobile communication networks required by high-capacity, high-quality, integrated services, soft-switch and so on, is being more and more and more operators and users of all ages.
At present, China Unicom's CDMA business has. However, beginning October 1, 2008 Unicom's CDMA business to China Telecom