3G Wireless Communications (W-CDMA, CDMA2000 and TDS-CDMA) Introduction Textbook

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3G Wireless Communications (W-CDMA, CDMA2000 and TDS-CDMA) Introduction Textbook [Copy link]

Lesson 1: Explanation of wireless technology related terms GSM/2G
　　

GSM ( Global System for Mobile Communication ) is a standard launched by the European Committee for Standardization in 1992. It uses digital communication technology and unified network standards to ensure communication quality and develop more new services for users. The transmission speed of the GSM mobile communication network is 9.6K /s . At present, there are more than 500 million GSM mobile users in the world , covering 1/12 of the population, and the proportion of GSM technology in the world's digital mobile phone field has exceeded 70% . Since GSM is the second generation of mobile communication technology relative to analog mobile communication technology, it is referred to as 2G . At present, China has more than 80 million GSM users, becoming the world's largest operating network.

GPRS ( General Packet Radio Service ) is a wireless packet switching technology based on the GSM system, providing end-to-end, wide-area wireless IP connection. Simply put, GPRS is a high-speed data processing technology that transmits data in the form of "packets". Network capacity is only allocated when needed and released when not needed. This transmission method is called statistical multiplexing. At present, the transmission speed of the GPRS mobile communication network can reach 115k/s . GPRS is a technology developed on the basis of GSM . It is a technology between the second-generation digital communication and the third-generation packet-based mobile service, so it is usually called 2.5G .

　　WAP (Wireless Application Protocol ) is the first phase of the integration of mobile communications and the Internet. This technology allows users to surf the Internet with wireless devices such as mobile phones and browse various websites through a small screen. These websites must also be written in WML (Wireless Markup Language), which is equivalent to HTML (Hypertext Markup Language) on the Internet . To use an analogy, GPRS and GSM are both roads, and WAP is a car on the road. After China Mobile opened GPRS , WAP drove on both GSM and GPRS roads, and driving on the GPRS road can increase the data transmission speed. Therefore, the existing content on WAP can also be browsed and used through GPRS . WAP is a 2.5G protocol.

　　2.5G

　　Other 2.5G technologies. 2.5G mobile communication technology is a connection technology from 2G to 3G . The current 2.5G connection technologies include: HSCSD , EDGE , EPOC , etc.

　　HSCSD ( High Speed Circuit Switched Data ) is an upgraded version of the GSM network. It can transmit data simultaneously through multiple time divisions instead of just one time division, thus greatly increasing the transmission speed to two to three times the normal speed. Currently, mobile phones of Singapore M1 and Singapore Telecom all use the HSCSD system, and its transmission speed can reach 57.6kbps .

　　EDGE (Enhanced Datarates for Global Evolution ) is based entirely on the current GSM standard. It not only maximizes the functionality of GPRS , but also provides broadband multimedia services through current wireless networks. EDGE 's transmission speed can reach 384k , and can be used in wireless multimedia, e-mail, online infotainment, and video conferencing.

　　3G

　　3G is the abbreviation of 3rd Generation , which refers to the third generation of mobile communication technology. Compared with the first generation analog mobile phones ( 1G ) and the second generation digital mobile phones such as GSM and TDMA ( 2G ), the third generation mobile phones refer to a new generation of mobile communication systems that combine wireless communication with multimedia communications such as the Internet. It can process multiple media forms such as images, music, and video streams, and provide a variety of information services including web browsing, teleconferencing, and e-commerce. In order to provide such services, wireless networks must be able to support different data transmission speeds, that is, they must be able to support transmission speeds of at least 2M/s , 384k/s , and 144k/s in indoor, outdoor, and driving environments, respectively . CDMA is considered to be the first choice for the third generation mobile communication ( 3G ) technology. The current standards include WCDMA , CDMA2000 , and TD-SCDMA .

　　An important reminder: In the article "What is broadband and broadband network", the watershed data problem of broadband / narrowband was mentioned (a network with a backbone network transmission rate of more than 2.5Gbyte and an access network transmission rate of 1Mbyte is defined as broadband), so it is obvious that all 2G and 2.5G products and technologies are not broadband technologies, and only 3G and its subsequent technologies can be called broadband technologies . It is said that some people want to skip 3G and directly study 4G , but the specific details are unknown. CDMA
CDMA ( Code-Division Multiple Access ) is an advanced wireless spread spectrum communication technology that emerged in the process of digital mobile communications. It can meet the market's high requirements for mobile communication capacity and quality. It has the characteristics of high spectrum utilization, good voice quality, strong confidentiality, low call drop rate, low electromagnetic radiation, large capacity, and wide coverage, which can greatly reduce investment and reduce operating costs. CDMA was first launched by Qualcomm of the United States. In recent years, it has developed rapidly due to various factors such as technology and market. Currently, the number of global users has exceeded 50 million. China has also opened CDMA telephone networks in cities such as Beijing and Shanghai .

　　3G Standards

In May 2000, the International Telecommunication Union (ITU) determined the three 　　major wireless interface standards, namely W-CDMA , CDMA2000 and TDS-CDMA , and wrote them into the 3G technology guidance document " International Mobile Telecommunications Plan 2000 " ( IMT-2000 for short ).

　　W-CDMA : Wideband CDMA , also known as CDMA Direct Spread , means wideband code division multiple access. Its supporters are mainly European manufacturers that mainly use GSM systems. Japanese companies are also more or less involved, including Ericsson, Alcatel, Nokia, Lucent, Nortel in Europe and America, and NTT , Fujitsu, Sharp and other manufacturers in Japan. This system can be built on the existing GSM network, which makes it easier for system providers to transition. In Asia, where the GSM system is quite popular, the acceptance of this new technology is expected to be quite high. Therefore, W-CDMA has an inherent market advantage.

　　CDMA2000 : CDMA2000 , also known as CDMA Multi-Carrier , was proposed by Qualcomm North America, with participation from Motorola, Lucent and later Samsung. South Korea is now the leader of this standard. This system is derived from the narrowband CDMA One digital standard, and can be directly upgraded from the original CDMA One structure to 3G , with low construction costs. However, the only regions using CDMA are Japan, South Korea and North America, so CDMA2000 does not have as many supporters as W-CDMA . However, the research and development technology of CDMA2000 is the fastest among all the standards, and many 3G mobile phones have been launched first.

　　TD-SCDMA : This is a 3G standard developed independently by mainland China . On June 29 , 1999 , the former China Ministry of Posts and Telecommunications Telecommunications Science and Technology Research Institute (Datang Telecom) proposed it to the ITU . This standard integrates the current international leading technologies such as intelligent wireless, synchronous CDMA and software radio, and has unique advantages in spectrum utilization, flexibility in business support, frequency flexibility and cost. In addition, due to the huge market in China, this standard has been valued by major telecommunications equipment manufacturers, and more than half of the equipment manufacturers in the world have announced that they can support the TD-SCDMA standard.

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Lesson 2: 3G and Optical Communications

What can 3G bring to optical communications? We think this should be discussed in four aspects: 1. What challenges does 3G bring to traditional optical network technology?　　2. How much bandwidth does 3G require from optical networks? 3. What kind of products or manufacturers can survive better under 3G ? 4. What is the optical network strategy of operators under 3G ? 　　Before discussing 3G in more detail , let's first understand 3G . 　　 　　 　　

　　We all know the three 3G standards : WCDMA , TD - SCDMA , and CDMA2000 . Since China Unicom has adopted CDMA2000 and Datang's TD-SCDMA has been in a state of change, the 3G that people talk about now is more likely to refer to WCDMA .

　　WCDMA currently has four standards: R99 , R4 , R5 , and R6 . R99 and R4 are relatively mature, and manufacturers have many products. As full IP R5 and R6 , the standards are still being changed and have not been finalized.

　　The following figure shows the WCDMA network structure based on R99 :

　　A more professional way of saying it is to divide 3G into radio network and core network. RAN and the airborne wireless part are called radio network, and CN refers to core network. As the basis of any service network, the optical network plays the role of carrying 3G services in 3G . The transmission from Node B to RNC and from RNC to core network requires the participation of optical network, and the interaction between core networks is also the task of optical network.

　　Below we discuss four questions:

　　1. What challenges does 3G bring to traditional optical network technology?

　　From the current optical network, SDH is undoubtedly the most mainstream technology. In the 2G era, SDH was very successful in adapting TDM services. In the 3G era, since each Iu interface adopts the ATM protocol, it means that our optical network must support ATM technology. Some people may ask, does this mean the revival of ATM ? The answer is no. Our use of ATM technology does not mean that we have to use ATM networking, that is, we can support ATM services based on SDH , which is the benefit brought to us by MSTP .

　　2. How big is the bandwidth demand of 3G for optical network? 　　This is a very troublesome question. If the 2M speed in static environment defined by 3G is really achieved , then a sector of a base station can only support a few users. Even at the walking speed of 384K , the number is very limited. Therefore, if we estimate our bandwidth demand according to the definition of 3G in the early stage of 3G construction , it will be an inestimable number. From the current situation, it is necessary to limit the number of data services, that is, to limit the number of various high-speed data users, and to provide substantial support for voice users with a speed of 12.2K .

　　3. What kind of products or manufacturers can survive better under 3G ?

　　Some netizens asked me on the forum, how can optical communication manufacturers survive better under 3G ? This question is basically beyond the scope of technology, I said I can only make a few random comments. First of all, I think 3G poses a great challenge to optical network products. I have seen that many manufacturers have integrated STM-1 optical ports on their 3G wireless devices, and some will even launch 1 + 1 backup optical ports as MSP next year . If one day I don’t see an optical terminal on the RAN , I will not be surprised. Moreover, AAL2 switching technology, as a new technology for ATM service aggregation, has surpassed the VPI/VCI- based switching provided by MSTP , which means that Node B may be more competitive than MSTP .

　　4. What is the optical network strategy of operators under 3G ? 　　For the old Telecom / Netcom, since the optical network has always followed the structure of the local fixed-line telephone tandem network, not only the network structure does not conform to the 3G business form, but also there are too few surplus resources in the network, which are difficult to use. This means that, at least at the C3 level, we need a brand new "transmission B plane", that is, we need to rebuild an optical network that conforms to the 3G business characteristics and reserves capacity for 3G .

　　As for China Unicom / China Mobile, since they have accumulated rich operating experience in CDMA and GSM , and their optical network and wireless network are closely linked, they should consider reusing old equipment and expanding capacity as the main idea. In particular, their optical network was established relatively late, and MSTP products account for the majority, which can better support ATM services under the condition of upgrading . The 3G craze has been going on for a long time since 2000 , but it has not really made any progress until recently. Fiber Online hopes that this time 3G is no longer a mirage, and it can take optical communications to the other side of the light. 　　

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Lesson 3: Analysis of the relationship between 3G , WLAN and Bluetooth

　 1. Background: As the commercial use of 3G - FOMA 　　in Japan and the 3G trials in Europe have not achieved the expected results, the 3G plans of operators in various countries have been further postponed. The group company has also put the integration of WLAN (wireless local area network) and 2.5G GPRS on the agenda to enhance the broadband and applicability of wireless Internet access and fill part of the market and technical space caused by the delay of 3G . At the same time, China Telecom and China Netcom have also intervened in the wireless data field with the help of WLAN , and tried to use the concepts of broadband, wireless, data, etc. to confuse users about the relationship between 3G , WLAN and Bluetooth .

　　In this context, some people may ask whether 3G will be attacked by 2.5G and WLAN ? What is the position of Bluetooth in this relationship? What is the relationship between these three technologies? This article will explain and analyze them from the aspects of technical attributes and supporting environment.

　　2. Overview 3G , WLAN , and Bluetooth are essentially complementary technologies, although they may be competitive at the edges. 　　

　　The WLAN technology that is currently widely used is the 802.11 family, which was the first wireless LAN standard published by IEEE in 1997. The 802.11b that is often mentioned in the media was approved in September 1999. It is also called Wi - Fi ( sounds a bit like Hi-Fi mentioned by music enthusiasts ) and can support a shared access rate of 11Mbps . Similar to this is the 802.11a technology, which uses the 5GHz frequency band and has a rate of up to 54Mbps . The frequency division uses OFDM (orthogonal frequency division multiplexing) technology, but the barrier-free access distance is reduced to 30-50 meters . A new candidate standard 802.11g that emerged last year is actually a hybrid standard that can adapt to the 802.11b standard and comply with the 802.11a standard. It is 5 times faster than 802.11b and is compatible with 802.11b .

　　Bluetooth technology is based on low-cost short-range wireless connection. It is an open global specification for establishing a special connection in the communication environment of fixed and mobile devices. It works in the 2.4GHz frequency band and currently supports a data rate of 1Mbps , data and voice services. Currently, it can achieve barrier-free access distance of about 10 meters (when the transmission power is 4dBm ). The Bluetooth technology research group SIG issued the Bluetooth 1.1 standard (channel data transmission rate is 1Mbps ) in early 2001 , and issued the Bluetooth standard version 2.0 ( channel data transmission rate is 2Mbps) at the end of 2001. Since Bluetooth and 802.11b both work in the 2.4GHz frequency band, there is interference between them. Literature data shows that when the transmission power of 802.11b using DSSS direct sequence spread spectrum is 20dBm , the Bluetooth data packet loss rate will reach 13.46% . Therefore, in April last year, the IEEE PAN ( Personal Area Network ) working group proposed a proposal to enable Bluetooth and 802.11b to work simultaneously to avoid mutual interference.

　　3G was first proposed by the International Telecommunication Union in 1985. At that time, considering that the system might enter the market around 2000, with an operating frequency band of 2000MHz and a maximum service rate of 2000Kbps , it was officially renamed IMT-2000 ( International Mobile Telecommunication-2000 ) in 1996 . 3G is a global roaming mobile communication network that can provide various types of high-quality multimedia services. It can achieve a static transmission speed of 2Mbps , a medium-low speed of 384Kbps , and a high- speed communication network of 144Kbps . However, due to the differences in interests among countries and manufacturers, the three major mainstream technical standards WCDMA , CDMA2000 and TD-SCDMA have emerged , and the focus is on WCDMA ( 3GPP ) and CDMA2000 ( 3GPP2 ). As the standardization work of 3GPP and 3GPP2 gradually deepens and tends to stabilize, the ITU has turned its attention to the next-generation mobile communication standard that can provide higher wireless transmission rates and a unified and flexible all- IP network platform, called Beyond 3G .

　　3. Different technical attributes
WLAN provides high bandwidth, but only within a limited coverage area (inside buildings and short distances outdoors). According to most industry estimates, even 1,000 WLANs cannot provide adequate coverage in a metropolitan area. In contrast, 3G networks support mobility across wide area networks, but data throughput is significantly lower than WLAN . Because 3G and WLAN have different advantages and limitations in coverage area and bandwidth, the two technologies support different applications and meet different needs. To this extent, they do not pose a competitive threat to each other, but complement each other.　　

　　Since 3G , wireless LAN and Bluetooth networks differ in their technical attributes, they also differ in the functions and applications they support.

　　(1) 3G supports mobility, and WLAN supports portability.

　　3G networks are built on a cellular architecture and are best suited to supporting data services in a mobile environment. The cellular architecture supports signal switching between different cells, providing users with full network coverage mobility, which is often extended through roaming agreements between different network operators. Of course, the bandwidth available to mobile users is limited.

　　WLAN wireless local area networks offer a lot of bandwidth, but their coverage area is limited ( up to 100 meters indoors ) . The applications they support are often accessed through portable data-centric devices such as laptops, rather than through phone-centric devices. PDAs and similar small devices are also beginning to be equipped with WLAN connectivity, but this process is still in its infancy. Bluetooth networks are only suitable for very short-range applications, and in many cases they are used simply as a replacement for cables.

　　(2) 3G supports voice and data, while WLAN mainly supports data.

　　Voice and data signals differ in many important ways: Voice signals can tolerate errors but cannot tolerate delays; data signals can tolerate delays but cannot tolerate errors. Therefore, a network optimized for data is not suitable for transmitting voice signals. Conversely, a network optimized for voice is not suitable for data signals. WLAN is primarily used to support data signals, in contrast, 3G networks are designed to support both voice and data signals.

　　Although WLAN is developing towards integrated telephony functions, its current structure lacks the necessary architecture required to support higher-level applications such as voice, multimedia and content: for example, architecture that adapts to the requirements of quality of service, scalability and billing mechanisms. Currently, a few large telecom operators in the country provide WLAN wireless LAN services (such as Shanghai Telecom's "Tianyitong" WLAN service), although they are still immature in roaming, coverage and billing integration.

　　4. Capacity, Interference and Dominant Forces 　　Everyone knows that WLAN can provide much greater bandwidth than 3G networks. While this assumption is correct, everyone should also note that WLAN is a shared-band technology. In shared-band technology, the available bandwidth is divided among users. In other words, the fact that a wireless LAN can provide 11Mbps bandwidth capacity does not mean that 10 users can use 11Mbps capacity at the same time . Although 3G networks are also limited by capacity, packet-switched cellular technology allows them to support a larger number of users at high capacity. And because WLANs operate in unlicensed frequency bands, they are also more susceptible to interference from other technologies ( such as Bluetooth ) operating in the same frequency band .

　　At the same time, the difference in the dominant forces also leads to different directions of technology development. WLAN is led by data communications rather than telecommunications manufacturers. The leaders here are traditional enterprise network companies such as Agere , Cisco , 3Com , IBM , D-Link and others. Wireless LAN vendors define mobility based on their own LAN experience ( such as portability ) . Therefore, their definition is different from the definition used by 3G mobile infrastructure equipment manufacturers. Many WLAN companies only focus on providing "transmission lines" and are not very interested in what is transmitted in these lines.

　　On the other hand, 3G infrastructure vendors ( such as Alcatel , Ericsson , Lucent , Nokia , Nortel , Motorola , Samsung and Siemens) come from the traditional telecom world. Their focus is on mobility, and they seek to enhance mobile voice services with mobile data services that can generate larger revenue streams for telecom network operators.

　　Mobility management presents serious challenges, but it also represents a huge revenue opportunity. In a mobile environment, a phone number generally belongs to a person rather than a place, so the network knows who you are, where you are and when you are there. This enables personalized information services that can be converted into huge revenue in the future.

　　In the case of Bluetooth, vendors such as Nokia and Ericsson are looking to Bluetooth technology simply to add functionality to their devices; they do not necessarily view Bluetooth as just another pure WLAN standard.

　　V. Supply Channels and Business Models The supply channels for WLAN and Bluetooth are significantly different from those for 3G communication systems. Most WLAN and Bluetooth device vendors use OEM relationships to simplify the sales and distribution process. Perhaps because they consider themselves to be merely providing wireless connectivity, WLAN and Bluetooth vendors do not specifically participate in the actual provision of services. In particular, Bluetooth itself is not secure or robust enough to support mobile services. It is just a chip technology that can only be delivered between Bluetooth vendors and specific device manufacturers in an OEM manner. 　　

　　At the same time, because the emerging world of such mobile data services is still not well defined : in this world, it is not clear what type of services or business models related to providing these services will be successful, so equipment manufacturers (especially 3G manufacturers) are actively exploring different service delivery models so that they can effectively sell network solutions and equipment to mobile operators. Telecom operators are also at the same starting line, thinking hard about future service content and business models. But it is obvious that there is an important difference between WLAN and 3G business models : the service provider providing WLAN services (which may be a large telecommunications operator or just an ordinary ISP ) only provides the infrastructure to users, and users must purchase or rent WLAN access equipment to access the wireless LAN; in contrast, 3G operators are likely to provide users with price subsidies for 3G terminals in order to attract users to join their 3G networks.

However, if the integration of WLAN and 3G or 2.5G at the business technology level 　　can be handled well , such as using GSM/GPRS SIM card authentication technology in a WLAN environment , telecom operators can also better establish their own unique business models to make full use of the original billing system and customer relationships.

　　In summary, we can conclude that 3G , WLAN and Bluetooth technologies have completely different properties and complement each other, although there is competition at the edges.

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Lesson 4: Comparison of mainstream technical standards for third-generation mobile communications

　 In recent years , global mobile communications have developed rapidly. The penetration rate of mobile phones in developed countries has reached more than 70 %, and some regions are even close to 100 %. In China, by the end of July 2003 , the number of mobile users had reached 240 million, and it still has a good development momentum. Due to the shortage of frequency resources and the need for more services, 2G networks can no longer meet the needs, and 3G is an inevitable trend of development. ITU has stipulated five terrestrial wireless technologies for 3G , among which WCDMA , cdma2000 and TD - SCDMA are the three mainstream technologies.

　　Among the three technologies, WCDMA and cdma2000 use frequency division duplex ( FDD ) and require paired frequency planning. WCDMA is wideband CDMA technology, with a spread spectrum code rate of 3.84Mchip/s and a carrier bandwidth of 5MHz , while the spread spectrum code rate of cdma2000 is 1.2288Mchip/s and the carrier bandwidth is 1.25MHz ; in addition, the synchronization between base stations of WCDMA is optional, while the synchronization between base stations of cdma2000 is required, so the global positioning system ( GPS ) is required. The above two points are the main differences between WCDMA and cdma2000 . In addition, in other key technologies, such as power control, soft switching, spread spectrum code and diversity technology used, they are basically the same, with only small differences.

　　TD - SCDMA uses time division duplex ( TDD ) and TDMA/CDMA multiple access modes, with a spread spectrum code rate of 1.28Mchip/s and a carrier bandwidth of 1.6MHz . Its base stations must be synchronized. Compared with the other two technologies, it uses smart antennas, joint detection, uplink synchronization, dynamic channel allocation, relay switching and other technologies. It has the characteristics of flexible spectrum use and high spectrum utilization, and is suitable for asymmetric data services.

　　In our country, there are only two 2G operators and the competition is not sufficient. Therefore, new mobile operators will be introduced. If new mobile operators choose to build 3G networks, they must consider factors such as standard stability, system performance, equipment maturity, roaming capability, service provision capability and intellectual property rights. The following is a comparative analysis of WCDMA , cdma2000 and TD - SCDMA in these aspects.

　　Standard stability　　 The WCDMA standard is formulated by the 3GPP organization. Currently, there are four versions, namely R99 , R4 , R5 and R6 . Among them, R99 has been stable and is currently in the process of improvement. Its main features are that the wireless access network adopts WCDMA technology, the core network is divided into circuit domain and packet domain, supporting voice services and data services respectively, and the concept of open service access ( OSA ) is proposed . Most of the current equipment is based on the R99 version, and the maximum downlink rate can reach 384kbit/s . The R4 version is a transitional version to the full packetization evolution. Compared with R99 , its main change is the introduction of the concept of soft switching in the circuit domain, separating control and bearer, and voice is transmitted through the packet domain. In addition, R4 also proposes a packetization solution for signaling, including two optional forms based on ATM and IP . R5 and R6 are full packetization networks. In R5, a high-speed downlink packet access ( HSDPA ) solution is proposed , which can make the maximum downlink rate reach 10Mbit/s . The standard is still being formulated.

　　The cdma2000 standard is formulated by 3GPP2 , and its versions include Release 0 , Release A , EV - DO and EV - DV . The main feature of Release 0 is that it continues to use the core network based on ANSI - 41D , and adds network entities that support packet services in the wireless access network and core network. This version has been stable. The CDMA Phase II project that China Unicom is about to launch adopts this version, and the maximum uplink and downlink rate of a single carrier can reach 153.6kbit/s . Release A is an enhancement of Release 0 , and the maximum rate of a single carrier can reach 307.2kbit/s , and it supports the concurrency of voice services and packet services. EV - DO uses a separate carrier to support data services, and can support high-speed data services with an average rate of 600kbit/s and a peak rate of 2.4Mbit/s in a 1.25MHz standard carrier. In the EV - DV stage, it can provide voice and high-speed packet data services simultaneously in a 1.25MHz standard carrier, with a maximum rate of up to 3.1Mbit/s .

　　The TD - SCDMA standard is also formulated by the 3GPP organization. The TSM ( TD - SCDMA over GSM ) standard formulated by the China Wireless Telecommunication Standard Organization ( CWTS ) is currently used. The system based on the TSM standard is actually a TD - SCDMA system supported by the GSM network . The core idea of the TSM system is to use TD - SCDMA base station equipment on the GSM core network . Its A interface and Gb interface are exactly the same as those of GSM . Only the GSM base station controller needs to be upgraded. On the one hand, the 3G spectrum is used to solve the problem of insufficient capacity of the GSM system, especially in high-density user areas. On the other hand, it can provide users with various data services with an initial rate of up to 384kbit/s . Therefore, the TD - SCDMA system based on the TSM standard is a good choice for operators with existing GSM networks. In the future, TD - SCDMA will be integrated into 3GPP 's R4 and subsequent standards.

　　In terms of standard integrity, the three technologies have complete definitions and solutions for increasing rates in terms of wireless access technology, and in terms of core network technology, all have routes for evolving toward packetization, but 3GPP has a clearer idea in terms of standard specifications. In terms of service, network management, and billing-related specifications, 3GPP 's definitions are more rigorous and complete.

　　System performance is mainly reflected in system capacity and coverage. For cellular systems, it is meaningless to calculate the capacity of a single cell theoretically. It can only be used as a reference and must be examined from the perspective of cellular networking. Generally, system capacity can be obtained through system simulation and actual measurement. The following mainly compares these two aspects :

　　First is capacity

　　When discussing the capacity of a wireless system, we cannot separate it from the specific services and wireless environment. Therefore, in a system using CDMA technology, the capacity of the air interface is related to the Eb/I0 (ratio of bit energy to interference power density) of the service, gain processing, interference from other cells, base station transmission power and the number of channel codes. The following explains the capacity differences among the three technologies for voice services and high-speed packet data services respectively.

　　For voice services, since the three systems have different carrier bandwidths, the average capacity within the unit bandwidth is generally compared. Although different companies set different conditions when conducting system simulations, the results of WCDMA and cdma2000 are similar, and there is no big difference for TD - SCDMA . For data service capacity, it is generally expressed by the data throughput within the unit bandwidth of the system. 3G has introduced data services of multiple rates. Even for the same system, different service combinations will produce different data throughputs. Generally, the comparison of data throughput is based on the data services of the same rate used by users in the same cell. From the simulation results, for medium and low-speed data, WCDMA and cdma2000 are basically equivalent, but WCDMA has an advantage in high-speed data services. Due to its technical characteristics, TD - SCDMA has a higher spectrum efficiency in theory and is suitable for providing data services, but it still needs to be verified by more experiments.

　　The second is coverage

　　The coverage of a base station is mainly determined by the maximum allowable loss of the uplink and downlink and the wireless propagation environment. In engineering, the coverage of a base station is generally estimated through the uplink and downlink budget. In the same frequency band, the coverage of WCDMA and cdma2000 is basically the same. Since TD - SCDMA uses the TDD method, its coverage is inferior to the other two technologies that use the FDD method. In short, WCDMA and cdma2000 are both FDD CDMA technologies , and there is no essential . Many simulation and field test results show that the system performance is basically the same. TD - SCDMA is quite different from the other two technologies, and more simulations and tests are needed to verify its performance.

　　Service provision capability Currently, service competition has become the focus of competition among existing operators, and new mobile operators are no exception. Only by providing a full range of mass services and special services can they attract more users and improve their competitiveness.

　　Both 3GPP and 3GPP2 have standardized the service classification and service generation mechanism. The two are basically the same in terms of service types, including basic voice services, supplementary services and various data services. In terms of service generation mechanism, 3GPP defines a variety of service generation mechanisms, such as network-based OSA and Customized Application for Mobile Network Enhanced Logic (CAMEL), Mobile Execution Environment (MExE ) and USAT ( USIM Application Toolkit , USIM application toolkit , where USIM is Universal Subscriber Identity Module universal user identification module). These mechanisms are aimed at enabling operators to provide services conveniently and quickly, and in accordance with the principle of separating the provision of services from the basic network, so that services can be provided by third parties other than operators, and open standard interfaces are used between services and networks. Service development is mainly completed by IT developers, and operators are responsible for network operations and the organization and management of numerous service providers. 3GPP2 has also proposed corresponding business concepts, with WIN specifications for intelligent networks, but no relevant specifications for open business systems, and plans to adopt 3GPP 's OSA concept. Therefore, 3GPP2 started late in the open business system and is not as complete as 3GPP .

　　In short, 3GPP organization is more perfect in service specification. At present, except for CAMEL -based intelligent network service, other service modes have not been widely used, but they have laid a good foundation for future service development. At present, the BREW ( Bi - nary Runtime Environment for Wireless ) service launched by Qualcomm is a non-standard service. It provides end-to-end solutions for wireless services, including providing BREW software development kits to application developers, BREW application platforms to equipment manufacturers, distribution systems for controlling and managing BREW to operators , and application download capabilities to end users. BREW is currently mainly used in cdma2000 systems.

　　Equipment maturity Equipment maturity is an important factor that operators should consider when building networks. It is related to the stability and reliability of network operation. From the current situation, cdma2000 is the most mature, especially in terms of terminals. There are more than 100 types of commercial terminals (using the frequency band of 800MHz to 1.9GHz ), and users can have more choices. cdma2000 has been operated in South Korea, Japan, the United States, Canada and other countries, and the total number of users reached 27 million by the end of 2002. The system products of the R99 version of WCDMA are also basically mature, but the terminal is still the bottleneck for business development. At present, there are only about ten types of commercial terminals (using the frequency band of 2GHz ). The commercial networks that have been opened are mainly the networks of Japan's NTTDoCoMo and J - phone , which was just opened at the end of 2002 , with about 150,000 users .

　　At present, whether in terms of system or terminal, the product maturity of TD - SCDMA lags behind WCDMA and cdma2000 . There is no commercial network yet, and there is a lack of network planning and testing tools. In terms of system, it is expected that products based on TSM will be launched first in 2003 , and products based on 3GPP R4 core network are still under development; in terms of terminals, there are plans to launch multi-mode terminals, but GSM/TD - SCDMA dual-mode terminals will be launched first, and GSM/WCDMA/TD - SCDMA triple-mode terminals will be launched later.

　　Roaming capability Good global roaming capability is conducive to cooperation with other operators and attracting high-end users. The main factors affecting roaming capability include the adoption of operators, the frequency band used and the interoperability of signaling. From the perspective of operator selection, although cdma2000 was commercialized earlier than WCDMA and TD - SCDMA , and its application scope is also wider, from the perspective of the choice of major operators around the world, 80 % of operators choose WCDMA technology, which provides a good development opportunity for WCDMA 's roaming capability.

　　From the frequency bands used, cdma2000 is mostly implemented in the form of in-band evolution, that is, most operators use the 800MHz frequency band of cdmaOne , and WCDMA mostly uses the 2GHz frequency band specified by the ITU . In China, the Ministry of Information Industry has announced the frequency planning of 3G , and it can be seen that the 2GHz frequency band is first used for both FDD and TDD .

　　From the signaling interoperability, in the core network, WCDMA is based on GSM 's Mobile Application Protocol ( MAP ), and user identification uses the same IMSI (International Mobile Subscriber Identity) as the GSM system , which has been proven to have good interoperability. cdma2000 uses the ANSI - 41 protocol based on cdmaOne , and user identification uses IMSI based on MIN . Although interoperability is not a problem in terms of technology, the system needs to be upgraded, which has been proven to affect roaming capabilities. TD - SCDMA currently has no commercial network, and its roaming will depend on the emergence of multi-mode terminals.

　　Impact of Intellectual Property Rights Because intellectual property rights have a certain impact on the production costs of equipment manufacturers, they will also affect the network construction costs of operators. The issue of intellectual property rights is very complex, so only a simple analysis is given here.

　　The main patent technologies of WCDMA are distributed among multiple patent owners, the most important of which are owned by Ericsson, Nokia, Qualcomm, Siemens and DoCoMo . Currently, the WCDMA Alliance led by NTTDoCoMo , Ericsson, Nokia and Siemens has taken the lead in jointly proposing a patent licensing plan, which will control the cumulative patent fee rate of WCDMA below 5 %.

　　Most of the core patents of cdmaOne are owned by Qualcomm. Other companies also claim to own basic patents in cdma2000 . The main reason is that in the cdma20001x /EV - DO/EV - DV standard, other companies have more patents. Although Qualcomm owns more patents, its advantage has been reduced in cdmaOne .

　　TD - SCDMA technology was proposed by Datang Telecom, so it has more basic patents in this area. It is generally believed that the basic patents of TD - SCDMA are mainly concentrated in Datang and Siemens, and Qualcomm also has a part. Most of these patents are core patents, and their status and role are more important. But recently other companies have also claimed to have TD - SCDMA basic patents. The main reason is that Datang Telecom's patents are mainly concentrated on the physical level of the air interface, and there are fewer patents for core network technology. The patents claimed by other companies are mainly concentrated in the core network. Compared with WCDMA and cdma2000 , it is obvious that state-owned enterprises have more intellectual property rights in TD - SCDMA , and have more say in patent negotiations, which is conducive to reducing equipment costs.

　　The final determination of intellectual property fees depends on the results of negotiations, which rely on government coordination and the cooperation of equipment manufacturers and pure patent licensors (such as Qualcomm).

　　From the above analysis, we can see that the three technologies have their own advantages and disadvantages, and there is no single perfect solution. In addition, the above analysis is based on the current situation. Some factors will change over time, especially the maturity of equipment. Therefore, new operators should consider various factors and choose specific technologies according to the time when network construction starts.

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Lesson 6: Third Generation Mobile Communication Related Technologies and Transition Strategies 　　The development characteristics of the first two generations of the wireless communication industry are mainly reflected in the demand for improved service quality, improved spectrum utilization and the demand for greater capacity. FDD and FDMA are technologies used in the first generation ( 1G ) wireless system, mainly focusing on analog cellular phone services. FDD , TDMA and FDD , CDMA are technologies used in the second generation ( 2G ) wireless system, which improves voice from analog to digital cellular and PCS . In the face of the development of voice and data integrated multimedia wireless communication equipment, the development of wireless Internet requires high-speed data transmission. The third generation of wireless communication will be a mobile IP standardized system, which needs to have higher spectrum efficiency and mobile speed to better support "mobile communication" and asymmetric services, higher throughput and less delay to improve various " IP " capabilities. Driven by this demand, various technologies have emerged. By June 30 , 1998 , the deadline for soliciting standards for the third generation of mobile communication wireless transmission technology (RTT), ITU - R received a total of 16 3G RTT standard proposals, of which 6 were satellite mobile RTT standard proposals and the remaining 10 were ground mobile 3G RTT standard proposals. These proposals came from the United States, Europe, China, Japan, South Korea and other countries and regions. Let's take a look at the characteristics and comparisons of various 3G technologies.

　　1. CDMA and TDMA

　　Among the five 3G technical specifications for wireless transmission technologies adopted by ITU-R , three are based on CDMA technology and two are based on TDMA technology:

　　---- Technical specifications based on CDMA technology:

　　IMT-2000 CDMA DS (WCDMA , cdma2000)
　　IMT-2000 CDMA MC (cdma2000 MC)
IMT-2000 CDMA TDD (TD-SCDMA , TD-CDMA)　　

　　---- Technical specifications based on TDMA technology:

　　IMT-2000 TDMA SC
IMT-2000 TDMA MC(DECT)　　

　　1. CDMA will be the development trend of 3G

　　( 1 ) High data transmission rate is the basis for the powerful functions of mobile communication systems. Although the TDMA system has a high service integration capability and can integrate data and voice, the terminal access rate is limited.

　　( 2 ) In comparison, CDMA technology has the advantages of large system capacity, good voice quality, strong anti-interference ability, and confidentiality.

　　( 3 ) CDMA in detail: CDMA, or code division multiple access, is a technology first proposed by Qualcomm, an American company. Its principle is based on spread spectrum technology, that is, the information data with a certain signal bandwidth to be transmitted is modulated with a high-speed pseudo-random code whose bandwidth is much larger than the signal bandwidth, so that the bandwidth of the original data signal is expanded, and then modulated by the carrier and sent out. The receiving end uses the exact same pseudo-random code to perform correlation processing with the received bandwidth signal to achieve information communication. Compared with FDMA and TDMA , CDMA has many unique advantages. In summary, the advantages of CDMA in digital mobile communications are:

　　---- The system capacity is large. In the CDMA system, all users share a wireless channel. When a user does not speak, all other users in the channel will benefit from reduced interference. Therefore, the CDMA system that uses the characteristics of human voice can greatly reduce mutual interference and increase its actual capacity by nearly 3 times. The system capacity of the CDMA digital mobile communication network is theoretically 20 times larger than that of the analog network , and in fact 10 times larger than that of the analog network , and 4-5 times larger than that of GSM .

　　---- The system communication quality is better. Soft switching technology (connect first and then disconnect) can overcome the disadvantage of hard switching that easily causes dropped calls. The CDMA system operates on the same frequency and bandwidth, and it is easier to implement soft switching technology than the TDMA system, thereby improving communication quality. The CDMA system uses adaptive threshold technology to determine the vocoder rate, powerful error correction, soft switching technology and separate multipath diversity receivers to provide extremely high data quality that cannot be matched by the TDMA system.

　　---- Frequency planning is flexible, users are distinguished by different sequence codes, and different CDMA carriers can be used in adjacent cells. Therefore, the frequency planning of CDMA networks is flexible and expansion is simple. CDMA networks also have the characteristics of low construction and operation costs and low base station equipment costs, so user costs are also low.

　　---- High frequency band utilization. CDMA is a spread spectrum communication technology. Although the improvement of the anti-interference performance of the spread spectrum communication system comes at the expense of occupying the frequency band width, CDMA allows a single frequency to be reused in the entire system area, allowing many users to share the frequency band and talk at the same time, greatly improving the frequency band utilization. Although this spread spectrum CDMA method occupies a wider frequency band, its frequency band utilization is very high when calculated based on the average frequency band occupied by each user. The CDMA system can also provide different channel frequency band utilization methods according to different signal rates, so that a given frequency band can be used more effectively.

　　---- Applicable to multimedia communication systems. The CDMA system can conveniently use multiple CDMA channels and multiple CDMA frames to transmit multimedia service information with different rate requirements. The processing and synthesis methods are more flexible and simple than TDMA and FDMA methods, which is conducive to the application of multimedia communication systems. For example, it can provide data services while providing voice services, so that users can receive paging information while talking.

　　----CDMA mobile phones have longer standby time. The combination of low average power, efficient VLSI design and advanced lithium batteries shows the breakthrough of CDMA in portable phone applications. Users can use their mobile phones to receive calls for a long time and receive short messages without hanging up.

　　However, the application of broadband CDMA systems still faces some technical difficulties. Reducing and offsetting multiple access interference is a basic issue of CDMA , and it is also an important issue to improve the capacity of broadband CDMA systems and give full play to the advantages of broadband CDMA systems.

　　2. Key technologies of CDMA

　　( 1 ) Power control technology

　　Power control technology is the core technology of CDMA system. CDMA system is a self-interference system. All mobile users occupy the same bandwidth and frequency. The purpose of CDMA power control is to enable the system to maintain high-quality communication without interfering with other users.

　　( 2 ) PN code technology

　　The selection of PN code directly affects the capacity, anti-interference ability, access and switching speed of CDMA system. CDMA channels are distinguished by PN code, so the PN code should have good autocorrelation, weak cross-correlation, simple implementation and coding scheme, etc. The current CDMA system uses a basic PN sequence - m sequence as the address code, and uses its different phases to distinguish different users.

　　( 3 ) RAKE receiving technology

　　The mobile communication channel is a multipath fading channel. The RAKE receiving technology is to receive the signal of each channel separately, demodulate it, and then superimpose the output to enhance the receiving effect. In the CDMA system, the multipath signal is no longer a disadvantage, but becomes a favorable factor that can be utilized.

　　( 4 ) Adaptive Threshold Technology for Vocoder Rate

　　The CDMA system uses adaptive thresholds to determine the vocoder rate. The adaptive thresholds can change the vocoder data rate according to the changes in the background acoustic noise level. The use of these thresholds suppresses the background acoustic noise, thus providing clear speech in a noisy environment.

　　2. TD-SCDMA Technology

　　1. Problems encountered in the development of GSM mobile communications

　　In recent years, China's GSM mobile communication network has developed strongly, with the number of mobile users exceeding 100 million and still growing rapidly.　　The first problem faced by the GSM network as it continues to develop rapidly is the frequency resource problem. For example, most cities in Guangdong are densely populated, so frequency resources are one of the important factors restricting the rapid development of mobile communications. The problem of insufficient frequency resources can be solved by using 900M/1800M dual-frequency networking. However, the attenuation of the 1800M frequency is worse than that of the 900M frequency . Therefore, the coverage radius of the 1800M GSM in urban areas is very small, and it cannot be completely co-located with the 900M GSM base station, which will increase the construction cost. With the growth of the demand for high-speed mobile data services by users in some urban areas, the bandwidth occupied by a single user has increased. After China joins the WTO , new telecommunications service operators will inevitably be added, and limited frequency resources will have to be allocated to more operators. All these will further aggravate the contradiction of tight mobile communication frequency resources.　

　　Another problem facing the rapid development of GSM network is the data service transmission rate. With the rapid development of the Internet, mobile Internet access has become more and more a fashionable demand. However, the user data transmission rate of GSM network is only 9.6kb/s , which will become a bottleneck for the development of mobile Internet access. The urgency of expanding the data service transmission rate of GSM network has become a practical problem to be solved. In addition, further improving the user data transmission rate is still a problem waiting to be solved.

　　2. China is not lagging behind in 3G

　　In recent years, the country has invested hundreds of millions of yuan in the research and development of third-generation mobile communication technology. On November 5 last year , a major breakthrough was made. The TD-SCDMA standard proposed by China for the third-generation mobile communication has been officially adopted by the International Telecommunication Union and has become one of the important standards in the third-generation mobile communication standard ( IMT-2000 ) series. This is the first time in China's century-old telecommunications history that a standard has been fully proposed and has become an international standard. This also marks that the development of China's communication technology has shifted from simple tracking to the stage of innovation, which is a groundbreaking change.

　　3. TD-SCDMA Technology

　　TD-SCDMA is a third-generation mobile communication system that uses time division duplex mode ( TDD ). Its main technical features are:

　　---- Adopt smart antenna technology ---- Adopt uplink synchronization mode ---- Adopt relay switching mode ---- Adopt low chip rate
　　
　　
　　

　　TD-SCDMA is the only third-generation mobile communication system in the world that uses smart antennas. In the TD-SCDMA system, due to the use of TDD mode, the uplink and downlink use the same frequency, and the spatial physical characteristics of the uplink and downlink are exactly the same at the same time. Therefore, as long as the spatial parameters are estimated based on the uplink data at the base station end, and the downlink data is digitally shaped based on these estimates, the purpose of adaptive beam shaping can be achieved, giving full play to the role of smart antennas.

　　In a CDMA system, the signals of multiple users are overlapped in the time domain and frequency domain, and the signals of each user need to be separated during reception. Ideally, the orthogonal characteristics of the spread spectrum code can ensure that the user data can be demodulated without deviation during demodulation. However, in actual systems, due to the influence of inaccurate synchronization and the multipath characteristics of the spatial channel, the ideal orthogonal characteristics cannot be maintained between the signals of each user. At this time, for a specific user, the signals of all other users working in the same frequency band are interference signals. As the number of users increases, the interference gradually increases. When the number of system users increases to a certain number, the interference increases to the point where the useful signal cannot be extracted. Therefore, the CDMA system is an interference-limited system.

　　After using smart antennas and uplink synchronization technology, multiple access interference can be greatly reduced. Only multipath from the main lobe direction and the larger side lobe direction will interfere with the useful signal. Therefore, the system capacity can be effectively improved, thereby significantly improving the spectrum utilization. The use of smart antennas can also effectively improve the antenna. Multiple low-power linear power amplifiers can be used to replace a single high-power linear amplifier. The price of a single high-power linear amplifier is much higher than that of multiple low-power linear amplifiers, so smart antennas can greatly reduce the cost of base stations. Another benefit of smart antennas is that they increase the redundancy of equipment.

　　The use of smart antennas can roughly locate the user's position and distance. Therefore, the base station and base station controller can use relay switching to determine whether the mobile phone user has moved to the monitoring area that should be switched to another base station based on the user's position and distance information. If the user enters the switching area, the base station controller can notify the other base station to prepare for the switching, thus achieving the purpose of relay switching. Relay switching can improve the success rate of switching.

　　The TD-SCDMA system uses only a 1.28Mb/s chip rate and only needs to occupy a single 1.6M bandwidth to transmit 2Mb/s data services. However, the 3G FDD solution requires 2*5M bandwidth to transmit 2Mb/s data services, that is, two symmetrical 5M bandwidths are required, as the uplink and downlink frequency bands, and there needs to be a frequency interval of several tens of M between the uplink and downlink frequency bands as protection. In the current situation where resources are very tight, it is very difficult to find a symmetrical frequency band that meets the requirements. However, the TD-SCDMA system can "make use of every opportunity" and can use any frequency band ( 1.6M ) that meets the requirements of one carrier , making flexible and effective use of existing frequency resources.

　　TD-SCDMA is a TDD working mode. The transmission of uplink and downlink data is determined by controlling the uplink and downlink sending time. No reception is performed during the sending period, and no transmission is performed during the receiving period. The ratio of the sending and receiving periods can be flexibly controlled and changed. For data transmission of asymmetric services such as the Internet, the amount of downlink data is much larger than the amount of uplink data. In this case, the downlink period can be controlled to increase and the uplink period can be shortened to achieve the purpose of efficiently transmitting asymmetric services.

　　According to the above characteristics, TD-SCDMA system is suitable for large and medium-sized cities and urban-rural fringe areas. In these areas, the population density is high, the frequency resources are tight, the mobile speed is not very high ( within 200km/h ), but a large number of small-radius, high-capacity cells are needed for coverage. At the same time, in these areas, the demand for data services, especially asymmetric data services such as the Internet, is relatively large, which can give full play to the technical advantages of TD-SCDMA .

　　3. LAS-CDMA Technology

　　LAS-CDMA technology has the following characteristics:

　　---- Higher spectrum efficiency than any 2G or 3G technology; ---- Superior to various data services at different rates; ----LAS-CDMA technology is suitable for the future "full IP system ( 3.5G or 4G ) requirements"
　　
　　

　　The performance advantages of LAS-CDMA (Large Area Synchronous Code Division Multiple Access) are as follows:

　　( 1 ) Additional spectrum. Since LAS-CDMA can provide more than 20 times the capacity of the existing 2G standard and 3 to 6 times the capacity of cdma2000 , it can minimize the construction and expenditure of additional networks, allowing telecommunications companies to compete in the market at a relatively low cost and provide customers with new and improved services in the most economical way.

　　( 2 ) New network structure. From a design perspective, LAS-CDMA technology can not only strengthen the current second-generation network, but also provide unprecedented functions for 3G and successfully promote the development of the fourth-generation ( 4G ) wireless network.

　　( 3 ) Global compatibility. The wireless telecommunication technologies used in different parts of the world are quite different. The current technologies include GSM , CDMA , TDM , etc. Since LAS-CDMA is compatible with all current and future standards, it is easy to migrate existing systems to LAS-CDMA . In addition, LAS-CDMA can also adapt to various advanced technologies that can further improve system performance and capacity. As an air interface technology, LAS-CDMA can be configured to use it as an enhanced mode to be compatible with other existing systems such as UTRA , IS-95 and TD-CDMA .

　　( 4 ) Improve server performance. LAS-CDMA can largely eliminate the interference phenomenon that occurs in the current CDMA system through its patented spread spectrum technology. Because this phenomenon not only affects the quality of voice services, but also eventually affects the quality of data services. In the LAS-CDMA system, the ISI (inter-code interference) and MAI (multiple access interference) of all signals can be reduced to zero within the "interference-free" time window, and the ACI (adjacent cell interference) can also be reduced to a marginal level. Therefore, LAS-CDMA not only improves system performance and capacity, but also does not add any complexity to other CDMA systems. The LAS-CDMA TDD mode has been designed to integrate the LAS-CDMA technology with the TDD technology that has been selected by IP , so it is very suitable for supporting mobile IP services. The LAS-CDMA TDD mode has the following characteristics:　　

　　---- High-speed mobility. In traditional CDMA TDD systems, the power control rate is limited by the frame length. Therefore, the system cannot achieve fast closed-loop power control. Because this control is required to compensate for high-speed channel fading and provide higher-speed mobility, traditional CDMA TDD systems cannot support high-speed mobility. However, in LAS-CDMA TDD systems, all signals will be kept in an "interference-free" time window through dual synchronization. Therefore, the LAS-CDMA system does not need high-speed power control, it only uses low-speed power control to save power in mobile stations.　

　　---- Asymmetric services. The LAS-CDMA TDD system adopts a combined FDMA/TDMA/CDMA multiple access scheme, in which the units of transmission / reception are "subframe (or time slot) -- code -- frequency". After the data unit is modularized, the scheme can be modified to support variable data rates, especially packet data. Since the switching points of the uplink and downlink can be flexibly allocated within a frame, and all subframes (time slots) can also be flexibly allocated to the uplink or downlink, it is an ideal solution for supporting IP asymmetric services.　

　　---- Compatibility. The spread spectrum technology based on the LAS-CDMA TDD mode is compatible with all other TDD systems, including UTRA TDD , TD-SCDMA , etc. LAS-CDMA can be integrated into existing TDD systems with only minor modifications at the physical layer to achieve higher system performance and capacity.　　

IV. Evolution Strategy

　　It is impractical to leap from GSM to the above solutions in one step, both economically and technically. Therefore, the real 3G technology should also include the communication technology from 1G and 2G to 3G .

　　1. Transition from 2G to 3G communication technology

　　Simply put, the transmission rate of the GSM network is 9.6kbsp. The use of GPRS technology will increase the transmission rate of the GSM network to 115Kbps. The application of EDGE technology will further increase the transmission rate of the GSM network to 384kbps , making high-quality image transmission possible . The true arrival of the 3G era, the combination of WCDMA and MPEG-4 technology reaches a transmission rate of 2Mbps , bringing real dynamic images.

　　In the process of transitioning to the third generation, "Bluetooth" must also be mentioned. "Bluetooth" is a new type of wireless network with low power wireless interface, which transmits digital data and voice signals in real time. It is a short-range wireless communication standard with a transmission range of about 10 meters jointly developed by mobile communication companies and computer companies. It has the advantages of high transmission rate, strong security and low price, which can enable portable computers, mobile phones and other mobile devices to communicate with each other wirelessly. With it, there is no need to lay special cables and connectors between various electronic devices in the office, home and on the road. As long as this chip is installed in the electronic equipment, the electronic devices in the local area will be connected by an invisible cable, and the relevant data can be automatically exchanged.

　　With Bluetooth, your device can get in touch with other people or devices at any time and any place, even if it encounters solid obstacles. Once any Bluetooth device finds another Bluetooth device, they can "interlock" with each other without any settings by the user. Another major advantage of Bluetooth is that it uses a globally unified frequency setting, eliminating the "national boundary" barrier, which has troubled users for many years in the field of cellular mobile phones. Bluetooth is the core technology of "wireless wallets". In the near future, if you carry a Bluetooth phone, you can walk through the supermarket checkout counter with your carefully selected food without taking out your wallet, because the phone will have settled the bill for you as you walk by.

　　The first step in the transition, GPRS technology, is an extremely cost-effective packet data technology. It adds packet switching data capabilities to the traditional circuit switching of ordinary GSM networks, and data is divided into data packets rather than transported in a steady stream of data. The ability to charge per data bit sent and received will ensure that customers only pay for usage, which will greatly reduce costs. Implementing GPRS functionality is also a huge project. In addition to transforming the base stations and base station controllers of the entire network, it is also necessary to add GPRS mobile phones and SGSN and GGSN network gateway equipment. Ericsson took the lead in proposing a GPRS solution. This year, Ericsson launched the first Bluetooth mobile phone T36 and the first GPRS phone R520 using Bluetooth technology . You only need to wear this lightweight device to your ear, and you can talk freely without being close to communication devices such as mobile phones and computers. At the 2000 China International Internet Conference and Exhibition, Siemens Mobile, which played the technology card, showed off its world-leading HSCSD and GPRS technology products, and fully demonstrated the milestone technology from GSM to UMTS . The tri-band HSCSD mobile phone S40 supports Bluetooth technology, which can make the speed of "wireless Internet access" surpass that of "wired Internet access". Guangdong Mobile Communications in our province has also officially launched GPRS services in Guangzhou and Shenzhen, and it is expected that there will be more than 3,000 GPRS users after the seventh phase of construction. Motorola plans to launch the first GPRS mobile phone L2000g on the market this year . Ericsson and Nokia's GPRS mobile phones will also be launched in the first and second quarters of 2001 respectively .

　　EDGE (Improved Data GSM Service) is a high-speed mobile data standard that effectively improves the efficiency of GPRS channel coding. It allows data transmission rates of up to 384kbps , which can fully meet the bandwidth requirements of future wireless multimedia applications. EDGE provides a transitional solution from GPRS to third-generation mobile communications, so that existing network operators can maximize the use of existing wireless network equipment and provide users with personal multimedia communication services in advance before the commercialization of third-generation mobile networks. Since EDGE is a transitional technology between the existing second-generation mobile network and the third-generation mobile network, some people call it "second-generation and a half" technology. EDGE also makes full use of existing GSM resources and protects the investment made in GSM . Most of the existing equipment can continue to be used in EDGE .

　　WCDMA (Wideband Code Division Multiple Access) brings the highest data transmission rate of 2Mbit/s . Under such conditions, any media in the computer can be easily transmitted through the wireless network. WCDMA can not only smoothly process sound and image data by effectively utilizing broadband, but also quickly connect to the Internet; in addition, WCDMA and MPEG-4 technology can also process dynamic images in a vacuum.

　　2. 3G evolution strategy suitable for national conditions

　　China should fully consider the current national conditions when choosing the 3G evolution strategy. The national characteristics of China's mobile communications are that the current population penetration rate of mobile phones is 7.7 %, and it is still facing a high-speed growth of user demand for voice services. Therefore, the newly built 3G network must have good backward compatibility with the GSM network, make full use of the existing GSM network, and choose a standard with high spectrum utilization. This should be the focus of China's third-generation mobile communications construction. Due to economic conditions, China is unable to rebuild a complete third-generation mobile communications network in a short period of time in a large-scale full coverage manner like the construction of the GSM network. Specifically, China's third-generation mobile communications evolution strategy should be as follows:

　　( 1 ) Relying on 900M GSM network, using dual-band dual-mode terminals

　　In view of the fact that users with demand for mobile high-speed data services in my country are mainly concentrated in large cities and economically developed medium and small cities; therefore, the construction of China's third-generation mobile communication network can only be to first build isolated third-generation mobile communication coverage areas in some large and medium-sized cities with demand. Specifically in our Guangdong Province, since the economy of the entire Qiujiang Delta is relatively developed, a small third-generation mobile communication coverage network can be built.

　　Moreover, the dual-band dual-mode networking mode should be considered in the early stage. The 3G terminal is a GSM/3G dual-band dual-mode terminal. In the 3G coverage area, the user's dual-band dual-mode terminal can obtain 3G high-speed data services and voice services. When the user terminal registered in a certain 3G island arrives at another 3G covered island, it can still obtain 3G high-speed data services and voice services. When the 3G dual-band dual-mode terminal arrives at an area without 3G coverage but only covered by the 900M GSM network, the 3G dual-band dual-mode user terminal can still obtain the support of 900M GSM voice services and enjoy roaming and switching functions. Using this method to build a 3G network can not only make full use of the already built national 900M GSM network, but also provide users with 3G services at a lower cost . When the demand for 3G services continues to increase, the number of 3G covered islands continues to increase and expand, gradually forming a local area or full city coverage, and finally forming a 3G network covering the whole country .

　　( 2 ) Using 3G base station subsystem to expand GSM network capacity. 　　Since 3G base stations are different from 2G or 2.5G base stations, 2G or 2.5G terminals cannot be supported by 3G networks. Therefore, after the large-scale construction of 3G networks begins, China will form a situation where two independent wireless networks (base station subsystems) of GSM 2G (or 2.5G ) and 3G coexist. Since the service rate and spectrum utilization rate of 3G are much higher than those of GSM , and the unit cost (per user, per Hz) is lower than that of GSM , the number of users of 3G networks will increase over time, and will eventually far exceed the number of users of GSM . By then, since GSM 2G and 2.5G users cannot use 3G networks, their situation is very similar to the current situation where users of analog networks cannot use GSM networks.

　　Therefore, after 3G base station subsystems and terminals mature, they should be used in GSM networks as soon as possible to replace the expansion of GSM base station subsystems. Instead of waiting for the third-generation core network to be built before using 3G base station subsystem equipment, this can not only meet the needs of rapidly growing mobile voice and data users, but also avoid the large-scale construction investment of 2G and 2.5G base station subsystems that are not forward compatible with 3G in the early stage of 3G scale construction , and minimize the losses caused by the evolution from 2G to 3G .

　　( 3 ) Make full use of the characteristics of TD-SCDMA and mix it with WCDMA to form a hybrid network

　　Since the TD-SCDMA third-generation mobile communication system has high spectrum utilization, it only needs a single 1.6M frequency band to provide 3G service requirements with a rate of 2M , and is very suitable for the transmission of asymmetric services. In the design of TD-SCDMA terminals and base station subsystems, the use of GSM/TD-SCDMA dual-frequency dual-mode is considered , which fully meets the requirements of relying on the 900M GSM network and gradually building a 3G network in an isolated form as mentioned above . Because TD-SCDMA meets the requirements of multiple interfaces such as Iub , A , Gb , lu , and lur at the same time, the base station subsystem of TD-SCDMA can be used as the expansion of 2G and 2.5G GSM base stations, and can also be used as the base station subsystem in the 3G network, which can take into account both current needs and long-term future development. In other words, the TD-SCDMA 3G system can simultaneously meet the two evolution strategies mentioned above.

　　TD-SCDMA is a TDD mode and has its own characteristics within its application scope. First, the terminal's mobile speed is limited to 240km/h by the existing DSP computing speed ; second, the spectrum utilization and system capacity can be optimal when the base station coverage radius is within 15km . Therefore, TD-SCDMA is suitable for use in cities and suburbs.

　　( 4 ) 3G core network evolution strategy

　　The original 900M and 1800M GSM core networks are circuit-switched, with a data transmission rate of only 9.6KB/S . In order to meet the transmission of high-speed data services, they must first undergo a GPRS upgrade. Each base station controller BSC must be upgraded to an E-BSC with GPRS function . In addition to voice services and circuit-type data services that continue to be transmitted to the MSC through the A interface , packet-type data services can be transmitted to the SGSN through the Gb interface . In the GPRS network, the highest data service rate can reach 115kb/s . Further improving the data service rate is limited by the baseband processing of the physical layer, and the capabilities of the Gb interface and SGSN can support data service rates of 384kb/s or even 2Mb/s .　

　　Therefore, after the GPRS upgrade, the data carrying capacity of the core network has been greatly improved. At this time, the TD-SCDMA base station subsystem can be used to expand the base station subsystem of the GSM network, directly access the A interface and Gb interface of the GPRS network , and provide voice services and data services within 2Mb/s respectively . At this time, the base station controller is called RNC . In addition to supporting the A interface and Gb interface, it also supports the Iub , Iu , and IuR interface standards, which are still being improved. After the 3GPP standards R99 and R00 are improved, RNC can use the Iub , Iu , and IuR interfaces to interconnect with the 3G core network, thereby evolving into a complete third-generation core network.

　　In short, the third-generation mobile communication network, whether it is the base station subsystem or the core network, is realized through gradual evolution. It must fully rely on the existing, large-scale GSM network to maximize the protection of existing investments during the evolution process and ensure the continuity of user services.

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Lesson 5: The important role of TD-SCDMA in 3G construction

　　在第三代移动通信(3G)标准领域，为了避免重演在2G领域由于各国(地区)频率分配的方式及制式技术选择的不同而造成的全球漫游困难，国际电信联盟(ITU) 在3G中提出了IMT-2000(国际移动通信-2000)的倡议，并由此而催生了最终的三大主流国际标准：WCDMA 、cdma 2000和TD-SCDMA 。其中，由中国提交的TD-SCDMA标准，虽然在ITU的标准征集阶段是后来者，却凭借其独特的技术优势最终胜出。同时，作为三个主流标准中惟一一个TDD标准，该技术从诞生初始就一直备受世人关注。那么，TD-SCDMA技术在我国3G网络建设中将扮演什么角色、发挥什么作用？将会对移动通信运营商和设备制造商产生哪些影响？

　　TD-SCDMA将有效缓解频率资源紧张

　　中国的移动通信用户截止到2003年4月底已达到2.26亿，但普及率仅为16.2%，远低于欧、美、日等普及率为60%以上的发达国家，而且仍以超过500万用户/月的速度稳步增长。同时，由于中国的移动通信用户分布严重不均，人口密度相对较高的城市地区移动通信用户的密度也远远高于平均水平，加之大城市中以商务人员和旅游者为主的流动人口越来越多，这些人大部分持有手机，所以部分地区GSM系统已经出现频率资源紧张的问题。与此同时，面向数据业务的GPRS业务占用的资源成倍增长(GPRS使用时将占用多个信道)，也加剧了GSM的频率危机。2G移动通信的进一步发展已经受到频率瓶颈的严重制约。因此，从某种意义上讲，3G也是移动数据业务进一步发展与2G频率资源严重不足之间难以调和的矛盾下的必然发展方向。那么，3G的出现能否缓解这种危机呢？

　　ITU、国内及欧洲对3G频率的规划方案

　　ITU在3G标准方案的征集之初，出于充分利用频率的考虑同时征集FDD和TDD两种方案，共收到10种地面移动标准提案。

　　从这些提案中可以得出的最后结论，欧、日、美提交的WCDMA和cdma 2000标准草案中均含有FDD、TDD两种方式。只是在后来的标准融合过程中，最终确定了欧洲提出的UTRATDD(TD-CDMA)和中国提出的TD-SCDMA为TDD国际标准。在后续的产业化开发中，由于TD-SCDMA明显的技术优势，使得所有从事于UTRATDD开发的公司全部放弃或转向了TD-SCDMA的开发。也就是说，目前世界上顺利进行产业化开发的3GTDD国际标准只有TD-SCDMA标准，也就意味着国际统一划分的TDD频段，将全部由TD-SCDMA技术使用，TD-SCDMA实现全球应用及漫游首先具备了宝贵的频率资源。

　　2002年初，美国联邦通信委员会(FCC)也正式对外公布了最新的TDD频谱分配方案。其中将原先由联邦政府控制的216-220MHz 、1390-1395MHz、1427-1435MHz 、1670-1675MHz、2385-2390MHz 共27MHz的频率转为TDD商业通信服务用途，加上以前分配的1910-1930MHz的20MHzTDD频段，目前共有47MHz的频率可用于3 GTDD移动通信。

　　在3G牌照发放上步伐较快的欧洲，基本上采取了将FDD频段与TDD频段捆绑发放的原则，几乎每个获得3G牌照的运营商都同时得到了FDD与TDD频段。

　　单纯依靠FDD技术难以有效解决3G的频率紧张问题

　　从3 GFDD系统运营所需的基本频率的角度来进行分析。对FDD中的WCDMA技术来讲，其基本带宽为5MHz×2，如果运营者建设多层网，即用宏蜂窝完成大面积覆盖，用微蜂窝覆盖热点地区，用微微蜂窝提供高速接入，则至少需要3个频点，即15MHz ×2的频率。考虑到在使用过程中的一定灵活性，某些国家也考虑使用20MHz ×2频率。

　　我国的实际3G频率状况是：3GFDD制式(包括cdma 2000和WCDMA) 在中国分得60M×2的频率。假设在3G实施时国内有4家运营商经营3 GFDD移动通信业务，由于不同运营商的3 GFDD网络间难以同步，因此，不同的运营商的3 GFDD网会产生邻频共存干扰。为消除干扰的影响，则要求不同运营商在相邻频段之间预留5M×2的保护频段，以保证各运营商之间的运营质量，四家运营商间至少需要15M×2(30M) 的保护频段。其结果是其中三家运营商仅能得到10M×2的FDD频率，另一家得到15M×2的FDD频率。仅有一家运营商的频率勉强可以支撑3 GFDD 的全国综合性大网。尤其是3G不再单纯以话音业务为主，而是话音加多媒体数据业务的模式，而单一数据终端的传输速率就可达到2 Mbps ，同时要占用5M×2的频宽。同时，除了人———人间的通信外，在3G应用时还会出现大量的机———机之间的数据通信，因此，频率紧张的矛盾会更突出。

　　从另一个角度讲，目前的2G运营商可以使用现有的2G频率构成3G宏蜂窝，但现实的情况是，2G网络的用户数太多，网络短时期内不会在我国退出历史舞台，也就是说，2G网络将与3G网络长期共存。因此，短期内让同时拥有2G和3G运营牌照的运营商清退出2G频率开展3G业务，是不现实的。短期内可启动的扩展频段只有尚未使用的GSM 1800M部分频段，但频段的频率有限。除此之外，只有启用2GHz以上的频段，由于该频段的频率较高，覆盖半径会降低，从而使组网成本上升。

　　TD-SCDMA的频率使用特点将有效解决3G频率紧张的矛盾

　　对TD-SCDMA技术来讲，该技术的单载波带宽为1.6MHz ，而且不需要对称频段，在考虑三级网络结构时，分配5MHz就可组建一个基本的全国网。中国的3G频率规划中为TDD模式划分了155M频率，完全可以满足多个TD-SCDMA 运营商大容量建网的频率需求。

　　同时，TD-SCDMA的技术特点尤其适合3G的应用。在TDD的工作模式中，上下行数据的传输通过控制上、下行的发送时间长短来决定，可以灵活控制和改变发送和接收的时段长短比例，这尤其适合今后的移动因特网、多媒体视频点播等非对称业务的高效传输。由于因特网业务中查询业务的比例较大，而查询业务中，从终端到基站的上行数据量很少，只需传输网址的代码，但从基站到终端的数据量却很大，收发信息量严重不对称。只有采用TDD模式时，才有可能通过自适应的时隙调整将上行的发送时间减少，将下行的接收时间延长，来满足非对称业务的高效传输。这种优势是FDD模式所不具备的。

　　TD-SCDMA有利于国内运营商发展 　　由于ITU为TDD技术在全球都划分了统一分配的频段，欧美各国也为TDD划分了专有频段。鉴于TD-SCDMA技术是目前国际上惟一的进行商业开发的3GTDD技术，只要各国运营商采用TDD技术，必将采用TD-SCDMA技术。因此，当其他国家决定建设TDD移动通信网时，中国运营商可以利用自身作为TD-SCDMA技术的首批运营者所积累的丰富运营经验，走向国际运营市场。

　　TD-SCDMA技术特点适合国内运营商进行业务创新。相对WCDMA和cdma 2000而言，TD-SCDMA是一项新生技术，首批采用TD-SCDMA的运营商，可以更有效地结合TD-SCDMA系统特性进行有针对性的业务创新。同时TD-SCDMA系统具有鲜明的技术特点，例如智能天线提供的强定位和追踪能力、上下行非对称业务、信道分配的灵活性、高频谱利用率等，这些特点都为国内运营商结合我国实际开发运营业务提供有力基础。

　　同时，TD-SCDMA技术的实施将为全球通信设备制造商提供新的机遇。

　　目前，作为国际上惟一在做商用研发的TDD的国际标准，关注、参与TD-SCDMA产品开发的厂商越来越多，TD-SCDMA 技术论坛的成员已突破410家，TD-SCDMA产业联盟的推进工作也逐步深入，包括芯片、系统、仪表的研发和产业化都已取得实质性突破。预计在技术验证和商用试验的基础上，TD-SCDMA将在未来1到2年内就会走向规模商用。

　　从目前来看，包括欧洲在内的世界大多数国家在3G频率规划和发放过程中，一般同时发放FDD和TDD频段。在3G这种以无线数据和多媒体业务为主的系统中，由于频率资源的压力，这些TDD频段早晚会被世界各大运营商使用，摆在3G设备制造商面前的，是如何切入TD-SCDMA设备开发的问题。因此，对全球相关芯片、软件和系统制造商而言，TD-SCDMA 是一个十分难得的历史机遇，特别是作为3G研发领域后来者的国内外设备制造商而言，更具有非同寻常的意义。WCDMA和cdma2000 相对开发时间较长，参与的设备制造商相对较多，但在实际商用运营中，运营商一般对一种标准的产品，只会选择前3至4名的设备制造商的产品，而位于3至4名之后的制造商和新的设备制造商都处于非常不利的地位，在市场上处于竞争劣势。在这种情况下，对落后者和后来者的制造商而言，做WCDMA、cdma2000产品的投资风险是非常大的。

　　同时，从知识产权角度来考虑，由于WCDMA和cdma2000的大部分核心专利由几十家公司所垄断，对于后来者而言，几乎不存在再创造新核心专利的机会。没有核心专利就意味着这些厂商不具备与其他拥有核心专利的公司进行核心专利交叉许可的条件，从而必须向多家拥有核心专利的厂商支付高昂的知识产权费，这将严重削弱这些后进入的设备制造商在3G产品价格上的竞争力，甚至将导致不得不退出自主研发的TD-SCDMA技术可在专网中实现第三代应用。

　　支持话音、数据和多媒体的3G移动通信系统，不仅适合于以公众运营为目的的公共网络，而且也适用于军队、电力、油田、水利等专用通信网络，使得这些专用领域的通信和信息化能力有大的飞跃。在这方面，中国自主知识产权的TD-SCDMA具有得天独厚的优势。

　　首先，包括核心芯片在内，国内厂商基本掌握其核心技术，又拥有相关的自主知识产权，因此，针对专用网络的应用特点，可以为其业务应用进行量身定制，例如提供加密功能、提供各种调度应用功能等。
其次，TD-SCDMA的技术特点可为专网的一些独特应用奠定基础。例如智能天线提供终端定位和跟踪能力、频率分配的灵活性、上下行数据不对称性等等。

　　同时，TD-SCDMA技术先进性带来实现低成本和业务灵活能力，以保证在专网中使用3G系统的经济可行性。据丹麦RTX公司估计，TD-SCDMA实现下来会比WCDMA便宜20%-25%，由于TD-SCDMA的码片速率为1.28Mbps，只是WCDMA标准的三分之一，因此，TD-SCDMA的终端完全可用软件无线电来实现基带处理，可极大地降低终端的成本和功耗，可有效解决专网应用特殊终端专用芯片的用量小、价格下不来的矛盾，而用软件无线电来满足各种特殊应用需求。

　　作为国际3G主流移动通信之一，TD-SCDMA技术为世人提供了一个充分利用宝贵频率资源的方案。同时，这项新生的技术给世界各国的运营商和通信设备制造商，尤其是那些后进入者提供了一个千载难逢的机会，大家将站在同一条起跑线上，在未来TD-SCDMA的巨大市场中共同发展。TD-SCDMA标准的诞生，不仅是中国通信史上的突破，更是世界通信史上的一个伟大创举。TD-SCDMA 技术标准必将把移动通信事业带入一个崭新的发展时代。

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第五课、TD-SCDMA在3G建设中的重要作用

　　在第三代移动通信(3G)标准领域，为了避免重演在2G领域由于各国(地区)频率分配的方式及制式技术选择的不同而造成的全球漫游困难，国际电信联盟(ITU) 在3G中提出了IMT-2000(国际移动通信-2000)的倡议，并由此而催生了最终的三大主流国际标准：WCDMA 、cdma 2000和TD-SCDMA 。其中，由中国提交的TD-SCDMA标准，虽然在ITU的标准征集阶段是后来者，却凭借其独特的技术优势最终胜出。同时，作为三个主流标准中惟一一个TDD标准，该技术从诞生初始就一直备受世人关注。那么，TD-SCDMA技术在我国3G网络建设中将扮演什么角色、发挥什么作用？将会对移动通信运营商和设备制造商产生哪些影响？

　　TD-SCDMA将有效缓解频率资源紧张

　　中国的移动通信用户截止到2003年4月底已达到2.26亿，但普及率仅为16.2%，远低于欧、美、日等普及率为60%以上的发达国家，而且仍以超过500万用户/月的速度稳步增长。同时，由于中国的移动通信用户分布严重不均，人口密度相对较高的城市地区移动通信用户的密度也远远高于平均水平，加之大城市中以商务人员和旅游者为主的流动人口越来越多，这些人大部分持有手机，所以部分地区GSM系统已经出现频率资源紧张的问题。与此同时，面向数据业务的GPRS业务占用的资源成倍增长(GPRS使用时将占用多个信道)，也加剧了GSM的频率危机。2G移动通信的进一步发展已经受到频率瓶颈的严重制约。因此，从某种意义上讲，3G也是移动数据业务进一步发展与2G频率资源严重不足之间难以调和的矛盾下的必然发展方向。那么，3G的出现能否缓解这种危机呢？

　　ITU、国内及欧洲对3G频率的规划方案

　　ITU在3G标准方案的征集之初，出于充分利用频率的考虑同时征集FDD和TDD两种方案，共收到10种地面移动标准提案。

　　从这些提案中可以得出的最后结论，欧、日、美提交的WCDMA和cdma 2000标准草案中均含有FDD、TDD两种方式。只是在后来的标准融合过程中，最终确定了欧洲提出的UTRATDD(TD-CDMA)和中国提出的TD-SCDMA为TDD国际标准。在后续的产业化开发中，由于TD-SCDMA明显的技术优势，使得所有从事于UTRATDD开发的公司全部放弃或转向了TD-SCDMA的开发。也就是说，目前世界上顺利进行产业化开发的3GTDD国际标准只有TD-SCDMA标准，也就意味着国际统一划分的TDD频段，将全部由TD-SCDMA技术使用，TD-SCDMA实现全球应用及漫游首先具备了宝贵的频率资源。

　　2002年初，美国联邦通信委员会(FCC)也正式对外公布了最新的TDD频谱分配方案。其中将原先由联邦政府控制的216-220MHz 、1390-1395MHz、1427-1435MHz 、1670-1675MHz、2385-2390MHz 共27MHz的频率转为TDD商业通信服务用途，加上以前分配的1910-1930MHz的20MHzTDD频段，目前共有47MHz的频率可用于3 GTDD移动通信。

　　在3G牌照发放上步伐较快的欧洲，基本上采取了将FDD频段与TDD频段捆绑发放的原则，几乎每个获得3G牌照的运营商都同时得到了FDD与TDD频段。

　　单纯依靠FDD技术难以有效解决3G的频率紧张问题

　　从3 GFDD系统运营所需的基本频率的角度来进行分析。对FDD中的WCDMA技术来讲，其基本带宽为5MHz×2，如果运营者建设多层网，即用宏蜂窝完成大面积覆盖，用微蜂窝覆盖热点地区，用微微蜂窝提供高速接入，则至少需要3个频点，即15MHz ×2的频率。考虑到在使用过程中的一定灵活性，某些国家也考虑使用20MHz ×2频率。

　　我国的实际3G频率状况是：3GFDD制式(包括cdma 2000和WCDMA) 在中国分得60M×2的频率。假设在3G实施时国内有4家运营商经营3 GFDD移动通信业务，由于不同运营商的3 GFDD网络间难以同步，因此，不同的运营商的3 GFDD网会产生邻频共存干扰。为消除干扰的影响，则要求不同运营商在相邻频段之间预留5M×2的保护频段，以保证各运营商之间的运营质量，四家运营商间至少需要15M×2(30M) 的保护频段。其结果是其中三家运营商仅能得到10M×2的FDD频率，另一家得到15M×2的FDD频率。仅有一家运营商的频率勉强可以支撑3 GFDD 的全国综合性大网。尤其是3G不再单纯以话音业务为主，而是话音加多媒体数据业务的模式，而单一数据终端的传输速率就可达到2 Mbps ，同时要占用5M×2的频宽。同时，除了人———人间的通信外，在3G应用时还会出现大量的机———机之间的数据通信，因此，频率紧张的矛盾会更突出。

　　From another perspective, the current 2G operators can use the existing 2G frequencies to form 3G macro cells, but the reality is that the number of users of the 2G network is too large, and the network will not be withdrawn from the historical stage in China in the short term, that is, the 2G network will coexist with the 3G network for a long time. Therefore, it is unrealistic to ask operators with both 2G and 3G operating licenses to clear out the 2G frequencies to carry out 3G business in the short term. The only extended frequency bands that can be activated in the short term are the unused GSM 1800M bands, but the frequency of the bands is limited. In addition, only the bands above 2GHz are enabled . Due to the high frequency of this band, the coverage radius will be reduced, thereby increasing the cost of networking.

　　The frequency usage characteristics of TD-SCDMA will effectively solve the contradiction of 3G frequency shortage

　　For TD-SCDMA technology, the single carrier bandwidth of this technology is 1.6MHz , and it does not require symmetrical frequency bands. When considering the three-level network structure, allocating 5MHz can form a basic national network. China's 3G frequency planning allocates 155M frequency for TDD mode , which can fully meet the frequency requirements of multiple TD-SCDMA operators for large-capacity network construction.

　　At the same time, the technical characteristics of TD-SCDMA are particularly suitable for 3G applications. In the TDD working mode, the transmission of uplink and downlink data is determined by controlling the length of the uplink and downlink transmission time. The length ratio of the transmission and reception time periods can be flexibly controlled and changed, which is particularly suitable for the efficient transmission of asymmetric services such as mobile Internet and multimedia video on demand in the future. Since the proportion of query services in Internet services is relatively large, and in query services, the amount of uplink data from the terminal to the base station is very small, only the code of the website address needs to be transmitted, but the amount of data from the base station to the terminal is very large, and the amount of information sent and received is seriously asymmetric. Only when the TDD mode is adopted, it is possible to reduce the uplink transmission time and extend the downlink reception time through adaptive time slot adjustment to meet the efficient transmission of asymmetric services. This advantage is not available in the FDD mode.

　　TD-SCDMA is conducive to the development of domestic operators. 　　As ITU has allocated a unified frequency band for TDD technology worldwide, European and American countries have also allocated a dedicated frequency band for TDD . As TD-SCDMA technology is currently the only 3G TDD technology that is being commercially developed internationally , as long as operators in various countries adopt TDD technology, they will definitely adopt TD-SCDMA technology. Therefore, when other countries decide to build TDD mobile communication networks, Chinese operators can use their rich operating experience accumulated as the first operators of TD-SCDMA technology to enter the international operating market.

　　TD-SCDMA technology features are suitable for domestic operators to carry out business innovation. Compared with WCDMA and cdma 2000 , TD-SCDMA is a new technology. The first batch of operators adopting TD-SCDMA can more effectively combine the characteristics of the TD-SCDMA system to carry out targeted business innovation. At the same time, the TD-SCDMA system has distinct technical features, such as strong positioning and tracking capabilities provided by smart antennas, asymmetric uplink and downlink services, flexibility in channel allocation, high spectrum utilization, etc. These features provide a strong foundation for domestic operators to develop and operate businesses in accordance with China's actual situation.

　　At the same time, the implementation of TD-SCDMA technology will provide new opportunities for global communication equipment manufacturers.

　　At present, as the only international standard of TDD that is being developed for commercial use, more and more manufacturers are paying attention to and participating in the development of TD-SCDMA products. The number of members of the TD-SCDMA Technical Forum has exceeded 410 , and the promotion work of the TD-SCDMA Industry Alliance has gradually deepened. Substantial breakthroughs have been made in the development and industrialization of chips, systems, and instruments. It is expected that based on technical verification and commercial trials, TD-SCDMA will be put into large-scale commercial use within the next 1 to 2 years.

　　At present, most countries in the world, including Europe , generally release FDD and TDD frequency bands at the same time during the 3G frequency planning and issuance process . In 3G systems that are mainly based on wireless data and multimedia services, due to the pressure of frequency resources, these TDD frequency bands will sooner or later be used by major operators around the world . The problem facing 3G equipment manufacturers is how to enter the development of TD-SCDMA equipment. Therefore, for global related chip, software and system manufacturers, TD-SCDMA is a very rare historical opportunity, especially for domestic and foreign equipment manufacturers who are latecomers in the field of 3G research and development, it has an extraordinary significance. WCDMA and cdma2000 have a relatively long development time, and relatively more equipment manufacturers are involved. However, in actual commercial operations, operators generally only choose products from the top 3 to 4 equipment manufacturers for a standard product, while manufacturers ranked after the top 3 to 4 and new equipment manufacturers are in a very disadvantageous position and at a competitive disadvantage in the market. In this case, for laggards and latecomers, the investment risk of making WCDMA and cdma2000 products is very high.

　　At the same time, from the perspective of intellectual property rights, since most of the core patents of WCDMA and cdma2000 are monopolized by dozens of companies, there is almost no opportunity for latecomers to create new core patents. The lack of core patents means that these manufacturers do not have the conditions for cross-licensing of core patents with other companies that have core patents, and therefore must pay high intellectual property fees to multiple manufacturers that have core patents, which will seriously weaken the competitiveness of these latecomers in 3G product prices and may even lead to the withdrawal of self-developed TD-SCDMA technology to realize third-generation applications in private networks.

The 3G mobile communication system 　　that supports voice, data and multimedia is not only suitable for public networks operated by the public, but also for special communication networks such as the military, electric power, oil fields, and water conservancy, making a big leap in the communication and information capabilities of these special fields. In this regard, China's independent intellectual property rights TD-SCDMA has a unique advantage.

　　First, domestic manufacturers have basically mastered the core technology, including core chips, and have related independent intellectual property rights. Therefore, they can tailor their business applications to the application characteristics of the private network, such as providing encryption functions, various scheduling application functions, etc. Secondly, the technical characteristics of TD-SCDMA can lay the foundation for some unique applications of the private network. For example, smart antennas provide terminal positioning and tracking capabilities, frequency allocation flexibility, uplink and downlink data asymmetry, etc.

　　At the same time, the advanced technology of TD-SCDMA brings low cost and flexible business capabilities to ensure the economic feasibility of using 3G systems in private networks. According to the estimation of RTX Company of Denmark, TD-SCDMA will be 20%-25% cheaper than WCDMA . Since the chip rate of TD-SCDMA is 1.28Mbps , which is only one-third of the WCDMA standard, TD-SCDMA terminals can completely use software radio to realize baseband processing, which can greatly reduce the cost and power consumption of terminals. It can effectively solve the contradiction between the small amount of special chips used in special terminals for private network applications and the low price, and use software radio to meet various special application requirements.

　　As one of the international 3G mainstream mobile communications, TD-SCDMA technology provides the world with a solution to fully utilize precious frequency resources. At the same time, this new technology provides a golden opportunity for operators and communication equipment manufacturers around the world, especially those latecomers. Everyone will stand on the same starting line and develop together in the huge TD-SCDMA market in the future. The birth of the TD-SCDMA standard is not only a breakthrough in China's communication history, but also a great initiative in the world's communication history. The TD-SCDMA technical standard will surely bring the mobile communication industry into a new era of development.

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