LTE learning Path (1)--development history of mobile communication technology

Preface

With the development of information technology and the increasing demand of users, mobile communication technology has been known as the most development potential in the field of modern communication, and the most popular research hotspot in the market foreground. At present, mobile communication technology has undergone several generations of development.

One, the first generation of mobile communication technology (1G)--Analog mobile communication

Originated in the 1980s, mainly using analog modulation technology and frequency division multiple access (FDMA) technology, the main disadvantage of this technology is low spectral utilization, signaling interference voice services. 1G main representatives are: Advanced Mobile phone System (AMPS) in the United States, the British Global Access Communication System (TACS) and the Japanese Telegraph and telephone system (NMT). 1G Mobile communication is based on analog transmission technology, characterized by small business volume, poor quality, poor cross-over, no encryption and low speed. 1G is mainly based on cellular structure network, directly using analog speech modulation technology, transmission rate of about 2.4kbit/s.

1G Features:

• only voice services;
• Low spectral multiplexing rate;
• Standard is not unified, can not roam (different working frequency bands);
• Poor security;
• High Price ("mobile")

Second-generation mobile communication Technology (2G)--Digital mobile communication

Originated from the early 90 's, the main use of digital time division multiple access (TDMA) and Code Division multiple Access (CDMA) technology. The second generation of mobile communications digital wireless standards mainly include: Europe's GSM and Qualcomm introduced the IS-95CDMA, China's main use of GSM, the United States, South Korea mainly using CDMA.

In order to adapt to the development of data business, in the second generation of technology also born 2.5G, that is GSM system GPRS and CDMA system is-95b technology, greatly improve the data transmission ability.

2G main business is voice, its main feature is to provide digital voice services and low-speed data services. It overcomes the weakness of analog mobile communication system, voice quality, security performance is greatly improved, and can be carried out in the provincial and provincial automatic roaming. The second generation of mobile communication replaces the first generation of mobile communication system to complete the transformation of analog technology to digital technology.

2G Features:

• Standard is not unified, only in the same format coverage area roaming, unable to roam around the world;
• Limited bandwidth, can not provide high-speed data transmission;
• Anti-interference anti-fading ability is not strong, the system capacity is insufficient;
• Low frequency utilization;

GSM (Global system for mobile communication, worldwide mobile communications system) components:

? Mobile Station (MS)? Base Station system (BSS)? Mobile Service Exchange Center (MSC)? Network Maintenance Operations Center (OMC)? Database (database)-HLR, VLR, AUC, EIR, etc.   GSM System structure diagram:

Third, the third generation mobile communication technology (3G)--Digital mobile communication

3G of theoretical research, technology development and standards began in the 80 's, the International Telecommunication Union (ITU) officially named as the International Mobile Communications (imt-2000,international mobile Telecommunications in the Year 2000). The European Telecommunication Standards Association (ETSI) calls it a universal mobile communications system (UMTS,UNIVERSAL Mobile telecommunication systems).

3G is the most basic feature of intelligent signal processing technology, intelligent Signal Processing Unit will become a basic function module, support voice and multimedia data communication, it can provide the first two generations of products do not provide a variety of broadband information services, such as high-speed data, slow images and TV images.

3G Standard: The International Telecommunication Union (ITU) has now established the world's four major 3G standards, namely WCDMA, CDMA2000, Td-scsma and WiMAX. China Mobile adopts TD-SCDMA and China Telecom adopts CDMA2000, and Unicom uses WCDMA

• WCDMA(wideband CDMA)--A large number of companies engaged in WCDMA standards research and equipment development, including Nokia, Motorola, Siemens, NEC, Alcatel and so on. The standard proposed the Evolution strategy of GSM (2G)--GPRS--EDGE--WCDMA (3G).
• CDMA2000(narrowband CDMA) was introduced by Qualcomm, Motorola, Lucent and Samsung, and South Korea was the leader of CDMA2000. This standard proposes the evolution strategy of CDMA (2G)--cdma2001x--cdma2003x (3G). One of the cdma2001x is called 2.5G Mobile communication technology. At present, China Telecom is the use of this scheme to the 3G transition.
• TD-SCDMA(Time division-synchronous CDMA, isochronous CDMA), the technology developed by China Datang Telecom 3G Standard. The proposed standard does not pass through the middle of the 2.5G, direct to 3G transition, very suitable for GSM system to 3G upgrade
• WIMAX(Global interoperability of microwave access), also known as the 802.16 Wireless metropolitan area Network, is another "last mile" broadband wireless connectivity solution for businesses and home users.

3G parameters of each standard

Wcdma:

RTT FDD

Asynchronous CDMA system: no GPS

Bandwidth 5MHz

Chip Rate: 3.8Mcps

China Band: 1940mhz-1955mhz (upstream), 2130mhz-2145mhz (downlink)

CDMA2000

RTT FDD

Synchronous CDMA system: with GPS

Bandwidth: 1.23MHz

Chip Rate: 1.2288Mcps

China Band: 1920mhz-1935mhz (upstream), 2110mhz-2125mhz (downlink)

Td - scdma

RTT TDD

Synchronous CDMA system: with GPS

Bandwidth: 1.6MHz

Chip Rate: 1.28Mcps

China Band: 1880mhz-1920mhz (upstream), 2010mhz-2025mhz (downlink)

Wimax

Bandwidth: 1.5mhz-20mhz

Maximum access Speed 70M

Maximum I transmission distance: 50 km

Code chip rate: Unknown

China Band: No　

Iv. comparison of FDMA, TDMA and CDMA

1. Frequency division is sometimes called channelized, that is, the entire assignable spectrum is divided into a number of individual radio channel transmit and receive carrier frequency, each channel can transmit one voice or control information.

2. Time Division Multiple access is on a broadband wireless carrier on a number of times or called time slots divided into several cent channel, each user occupies a time slot, only in this designated time slot to receive or send a signal, it is called division multiple address.

3. Code Division Multiple access is a multi-address method which is realized by the different code sequences formed by spread spectrum technology.

V. LTE (long term Evolution) project

LTE is the evolution of 3G, not a widely misunderstood 4G technology, but a transition between 3G and 4G technology, is the global standard of 3.9G, which improves the 3G air access technology, using OFDM and MIMO as the only standard for their wireless network evolution.

LTE provides a peak rate of 326Mbps and downstream 86Mbps at a 20MHz spectral bandwidth. Given the need to provide a higher data rate than the 3G and the possible future distribution of the spectrum, LTE needs to support transmission bandwidth above 5MHz.

3GPP LTE is developing the wireless interface and wireless access network architecture Evolution technology mainly includes the following content:

• Significantly increased transmission rate. If the 20MHz bandwidth is achieved: downlink transmission rate 100mbit/s and upstream transmission rate 50mbit/s;
• Increasing the bit rate of the cell boundary while maintaining the current base station position unchanged;
• Obviously improve the spectrum utilization;
• Significantly lower waiting time, less than 100ms, etc.