What is 3G TD-CDMA? What are its differences and connections with GSM and CDMA?

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TD-SCDMA\CDMA\GSM\3G Differences and Connections

Now let’s talk about 3G

First of all, 3G network can make video calls, watch online TV, etc. Foreign 3G networks are relatively mature.

TD-SCDMA was developed by China itself 3G network.

GSM digital network: GSM: GSM (Global System For Mobile Communication) network is the global system for mobile communications, also known as "Global Communication". Many companies have participated in the formulation of standards. The GSM digital mobile communication system was designed by a standardization committee composed of major European telecommunications operators and manufacturers. It was developed on the basis of the cellular system. Since the end of 1994, our country has been preparing to build GSM cellular mobile communication networks in more than ten provinces and cities. Its development momentum has been admired by everyone. Now the GSM digital network has covered more than 30 provinces (autonomous regions and municipalities), more than 300 regions and 2,000 cities across the country. Multiple counties and cities, and can roam with more than 40 countries.

GSM uses digital modulation technology. One of its key technologies is time division multiple access (each user selects a carrier frequency in a certain time slot and can only receive information at a specific time). The GSM system has Several important features: good anti-theft and copying capabilities, large network capacity, rich number resources, clear calls, strong stability and not susceptible to interference, sensitive information, few dead spots in calls, low power consumption of mobile phones, etc. Therefore, its voice is clear, confidentiality is easy, and it can provide more data transmission services. The number of users that the GSM network can support is 1.8-2 times that of the analog network.

Due to the rapid development of GSM, after its 900MHZ frequency band was full, the GSM1800 frequency band was opened up. Mobile phones work in the 900MHZ and 1.8GHZ frequency bands as well as GSM1900MHz and other frequency bands.

GPRS: GPRS is the English abbreviation of General Packet Radio Service, and the Chinese is General Wireless Packet Service. It is a wireless packet switching technology based on the GSM system, providing end-to-end, wide-area wireless IP connections. Compared with the original GSM dial-up circuit-switched data transmission method, GPRS is a packet switching technology, which has the advantages of "real-time online", "pay-as-you-go", "quick login", "high-speed transmission" and "free switching". In layman's terms, GPRS is a high-speed data processing technology that transmits data to users in the form of "packets." Although GPRS is a transitional technology for the transition from existing GSM networks to third-generation mobile communications, it has significant advantages in many aspects.

Due to the use of "grouping" technology, users' Internet access is relatively stable and avoids the trouble caused by unnecessary short-term connections. In addition, the method of using GPRS to access the Internet is different from that of WAP. Using WAP to access the Internet is like surfing the Internet at home. You need to "dial-up" first. After you access the Internet, you cannot use the phone line at the same time. However, GPRS is superior. You can download data and make calls. At the same time. Technically speaking, voice transmission (i.e. calls) continues to use GSM, while data transmission can use GPRS. In this case, the application of mobile phones is raised to a higher level. Moreover, the development of GPRS technology is also very "economical" because it only needs to use the existing GSM network for development. GPRS is used for a wide range of purposes, including sending and receiving emails through mobile phones, browsing on the Internet, etc.

TDMA: TDMA is the abbreviation of Time Division Multiple Access. This is a technology that uses Time-Division Multiplexing (Time Division Multiple Access) to provide wireless digital services. It represents a mobile phone system. Digital signal transmission technology. TDMA divides a radio frequency into multiple time slots and then assigns these time slots to multiple groups of calls. In this way, one radio frequency can support multiple data channels simultaneously, and this technology has now become the basis of today's D-AMPS and GSM systems.

Comparison between GSM digital phone and analog mobile phone voice

The voice of GSM digital phone is digitized before being transmitted on the wireless channel. It is not as easy to be interfered as analog mobile phone , so the voice is clear and there is little interference during the call. However, since digital voice is transmitted, there is also the disadvantage that the voice is somewhat distorted. The voice distortion of analog mobile phones is better than that of GSM digital phones. Now, relevant departments are researching and developing more advanced voice digital coding technology to reduce the voice distortion of GSM mobile phones.

CDMA digital network: CDMA is the English abbreviation of Code Division Multiple Access. It is a new and mature technology developed on spread spectrum communication technology, a branch of digital technology. Wireless communication technology. 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, small electromagnetic radiation, large capacity and wide coverage, which can greatly reduce investment and Reduce operating costs.

Industry operators are working hard to increase the number of users in their systems, reduce the cost per user, create greater profits and actively strengthen market penetration. Code division multiple access technology is one of the digital communication technologies that solves this problem.

The advantages are:

Efficient frequency band utilization and larger network capacity

Simplified network planning

Improved call quality

Enhance confidentiality

Improve coverage characteristics

Extend user talk time

Soft volume and "soft" switching

Internet speed is faster

At present, the "China Great Wall Mobile Communication Network" using CDMA technology in China has been opened in Beijing, Shanghai, Guangzhou, Xi'an and other places.

CDMA is the latest development of digital network technology. The United States is its birthplace and is the most widely used. CDMA mobile phones have clear voice, close to wired phones, good signal coverage and less likely to drop calls.

Compared with GSM mobile phones, CDMA mobile phones have the following advantages: CDMA mobile phones use advanced switching technology: soft handover technology (that is, switching is first connected and then interrupted), which makes the call on CDMA mobile phones It can be compared with fixed telephones; using CDMA network, operators' investment is relatively reduced, which leaves room for the reduction of CDMA mobile phone tariffs; due to the use of a modulation and multiple-access communication method based on frequency extension communication, its capacity It is 10 times higher than analog technology and about 4 times higher than GSM network. CDMA based on broadband technology makes video applications in mobile communications possible, thus enabling mobile phones to move from narrow services such as making phone calls and sending short messages to broadband multimedia applications.

GSM1X: The so-called GSM1X refers to a dual-mode mobile phone that supports two standard networks. There are mainly two dual-mode mobile phones: GSM/PHS and GSM/CDMA. Compared with GSM/GPRS, the Internet speed is greatly improved. Among them Currently, the only GSM/PHS mobile phones are Sanyo's PDG-G1000 (i.e. J100 sold by Taiwan Popular Telecom and UT's UT818). GSM/CDMA dual-mode mobile phones are mainly three models of Samsung, LG and Motorola available in the country.

GSM1x can be used as a technical solution to enable China Unicom to allow its existing GSM users to enjoy enhanced CDMA 1X services while retaining the existing GSM business layer and SIM card user characteristics. benefit.

GSM1x combines the advantages of CDMA 1X and GSM-MAP and is a solution that can be used by GSM operators using any frequency to provide CDMA 1X services.

GSM1x can maximize the operator's investment in the existing GSM-MAP network and retain all major functions and services that can be provided in the system. GSM1x can increase the voice and data capacity of operators, while supporting the overlay of a CDMA 1X network on a GSM network, the use of SIM card-based GSM/CDMA dual-mode mobile phones, and promoting global roaming across GSM and CDMA dual networks.

3G: 3G is the third generation of mobile communication technology and the general name for the next generation of mobile communication systems. The main standards are GSM/GPRS/WCDMA/EDGE/TD-SCDMA. The 3G system is committed to providing users with better voice, text and data services. Compared with existing technologies, the main advantages of 3G technology are that it can greatly increase system capacity, improve communication quality and data transmission rate. In addition, seamless roaming technology between different networks can be used to connect wireless communication systems and the Internet, thereby providing more and more advanced services to mobile terminal users.

Standards of 3G technology: The International Telecommunications Union (ITU) determined the three mainstream 3G standards of W-CDMA, CDMA2000 and TD-SCDMA as early as May 2000.

WCDMA: The full name of WCDMA is (Wideband Code Division Multiple Access), and the Chinese translation is "Wideband Code Division Multiple Access". WCDMA originated from the fusion of several technologies in Europe and Japan. It adopts MC FDD duplex mode and has good compatibility and interoperability with GSM network. As a new technology, it is not as mature as CDMA2000 in terms of technology maturity, but its advantage is that the widespread adoption of GSM can bring convenience to its upgrade. Therefore, it has been favored by major manufacturers in recent times. WCDMA adopts the latest Asynchronous Transfer Mode (ATM) WeChat element transmission protocol, which can allow more voice calls to be transmitted on one line. The number of calls has been increased from the current 30 to 300. Lines in densely populated areas will no longer be prone to congestion. . WCDMA uses direct expansion (MC) mode with a carrier bandwidth of 5MHz. It can support data transmission rates ranging from 384Kbps to 2Mbps. In high-speed moving conditions, it can provide a transmission rate of 384Kbps. In low-speed or indoor environments, it can Provides transfer rates up to 2Mbps. The GSM system currently can only transmit 9.6Kbps, and the fixed line Modem only has a rate of 56Kbps. It can be seen that WCDMA is a wireless broadband communication.

In addition, in the same transmission channels, it can also provide circuit switching and packet switching services. Therefore, consumers can use switching to answer calls at the same time, and then access the Internet through packet switching. Such technology can improve the efficiency of mobile phone use, allowing us to exceed the limitations of services that can only do voice or data transmission at the same time.

In terms of cost, because WCDMA relies on packet switching technology, the cost of network usage is not calculated based on the access time, but based on the consumer's data transmission volume.

EDGE: The full English name of EDGE is Enhanced Datarate for GSM Evolution, and its Chinese meaning is "Improved Data Rate GSM Service". It is a data-enhanced mobile communication market highlight based on the GSM/GPRS network. It has successively Cingular Wireless and AT&T Wireless in the United States, Telefonica Moviles in Chile, CSL in Hong Kong SAR of my country, and AIS in Thailand have launched services based on EDGE. At the same time, some European mobile operators have also begun to show interest in EDGE, among which TIM and TeliaSonera have made it clear that they will adopt EDGE technology. This technology mainly enables the use of broadband services, allowing networks using the 800, 900, 1800, and 1900MHz frequency bands to provide some functions of the third-generation mobile communication network, and can greatly improve the standardized services currently provided on GSM and TDMA/136. This technology can provide wide-area data communication services of 384kbps and local-area data communication services of approximately 2Mbps, which can fully meet the bandwidth requirements of future wireless multimedia applications.

The concept of EDGE was first proposed to ETSI by Ericsson in 1997. In the same year, ETSI approved the feasibility study of EDGE, which paved the way for the future development of EDGE. Although EDGE still uses the GSM carrier bandwidth and time slot structure, it can also be used in other cellular communication systems. EDGE can be regarded as an effective universal radio interface technology that provides high bit rates and thus promotes the evolution of cellular mobile systems to third generation functions. On this basis, the Unified Wireless Communications Forum (UWCC) evaluated EDGE technology for TDMA/136 and approved the technology in January 1998.

EDGE provides a transitional solution from GPRS to third-generation mobile communications, allowing existing network operators to maximize the use of existing wireless network equipment in the third-generation mobile network. Provide users with personal multimedia communication services in advance before commercialization. Because GDGE is a transition technology between the existing second-generation mobile network and the third-generation mobile network, some people also call it "second and a half generation" technology. EDGE also makes full use of existing GSM resources and protects investments in GSM. Most of the existing equipment can continue to be used in EDGE. EDGE can provide three groups of services: EGPRS service: maximum rate ≥384kbps48kbps/BP; T-ECSD business: transparent enhanced circuit switching service, maximum rate ≥32kpbs/Bp; NT-ECSD: non-transparent enhanced circuit switching service, maximum rate ≥28.8kbps.

From a technical perspective, the advantages of EDGE technology that are different from GSM are:

8 PSK air interface mode

Enhanced AMR encoding method

MCS1~9 nine channel coding methods

Link adaptation

Incremental redundant transmission

Automatic adjustment of RLC window size

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TD-SCDMA: The full name of TD-SCDMA is Time Division-Synchronous Code Division Multiple Access (time division synchronous code division multiple access technology). It is one of the third generation mobile communication space interface technical specifications officially released by ITU. It is fully supported by CWTS and 3GPP. It is China Telecom's first complete communication technology standard in a century. It is a solution that can replace UTRA-FDD. It integrates the technical advantages of CDMA, TDMA and FDMA, has large system capacity and wide spectrum. Mobile communication technology with high utilization rate and strong anti-interference ability. It adopts smart antenna, joint detection, relay switching, synchronous CDMA, software radio, low chip rate, multiple time slots, variable spread spectrum system, adaptive power adjustment, etc. technology. Time-domain adaptive resource allocation in the TD-SCDMA transmission direction can achieve optimal utilization of spectrum allocation independent of symmetrical service load relationships. Therefore, TD-SCDMA can support all 3G services such as voice and Internet at rates from 8kbps to 2Mbps through optimal adaptive resource allocation and optimal spectrum efficiency. In the final version, it is planned to directly connect the TD-SCDMA wireless network to the INTERNET.

Personal Access Phone System

Personal Access Phone System, also known as PAS (Personal Access Phone System), is a new type of personal wireless access system that uses advanced PHS micro-cell technology. It organically combines local telephone transmission and switching with wireless access technology, utilizes local telephone switching and transmission resources, and wirelessly provides it to personal communication terminals with mobile roaming capabilities within a certain range. In short, "Little Smart" is through a certain Technical means have transformed the original fixed-use telephone into a portable and mobile wireless telephone.

The development of mobile phone systems

1G (first generation) represents the first generation of mobile communication technology. Represented by the now obsolete analog mobile network.

2G (second generation) represents the second generation of mobile communication technology. Represented by GSM. Taking digital voice transmission technology as the core.

2.5G is based on the transition type between 2G and 3G. Compared with 2G, the speed and bandwidth are improved. It enables existing GSM networks to easily achieve simple access to high-speed data packets.

The 2.5G (Generation) mobile communication technology that is currently in commercial application is a connectivity technology from 2G to 3G. It breaks through the constraints of 2G circuit switching technology on data transmission rate and introduces packet switching technology. , thus achieving a qualitative breakthrough in data transmission rate, and is a transitional technology between 2G and 3G. The emergence of 2.5G is mainly due to the fact that 3G is a huge project involving many and complex layers. It is impossible to move from the current 2G to 3G immediately. Representatives include: GPRS, HSCSD, WAP, EDGE, Bluetooth, EPOC and other technologies.

3G is the abbreviation of 3rd Generation in English, which refers to the third generation of mobile communication technology. At present, my country's 3G standards have not yet been promulgated. Compared with the first generation of analog mobile phones (1G) and the second generation of digital mobile phones (2G) such as GSM and TDMA, the third generation of mobile phones generally refers to a new generation of mobile communication systems that combine wireless communications with multimedia communications such as the Internet.

It can process various media forms such as images, music, and video streams conveniently and quickly, and provide a variety of information services including web browsing, conference calls, and e-commerce. Provide powerful support for integrating multimedia elements into mobile phones. But in order to provide this service, the wireless network must be able to support different data transmission speeds, which means that it can support at least 2Mbps (megabytes per second), 384kbps (kilobytes per second) and 144kbps in any environment. transmission speed. The bandwidth provided by the 2G network is 9.6Kpbs. 2.5G increases to 56Kpbs. 3G will have wider bandwidth and its transmission speed will reach 100-300Kbps. It can transmit not only voice but also data, thereby providing fast and convenient wireless applications.