4g Technology development Prospects

This paper briefly reviews the development of mobile communication in the previous more than 20 years and points out its unsatisfactory status. This paper expounds some requirements, ideas and discussions about the development of the new generation mobile communication technology in the relevant industries around the world.

Mobile communications Since 1980, has gone through 20几 years, experienced the first generation (1G) and second generation (2G), is now moving to the third generation (3G) smooth evolution, and in the exploration of the future after 3G or 4G.

1 First 20 years of the mobile communication

The first generation of mobile communications from the commercial to the completion of the mission, about 1980 years until 1994, in frequency division multiple access (FDMA) format to provide ordinary analog phones, the actual data rate of 2. 4kbit/s.

The second generation of mobile communications, which lasted about 1995 years to the beginning of this century, uses time division multiple access (TDMA) system to support data circuit exchange, providing high-quality digital telephone and short text transmission, the data rate is 14. 4KBIT/S (actually only up to 9.) 6KBIT/S).

In recent years the development of the second-generation half (2). 5G) mobile communication supports packet switching, and the data rate target is 115kbit/s (actually only 40kbit/s).

2G and 2. 5G Mobile communication technology, although more than 1G, but with the increase in the number of users and the demand for multimedia services, its use of frequency bands, spectrum utilization, access rate and network capabilities are not obvious.

As early as the mid 1980s, the ITU calculated to work out a future terrestrial mobile communication system (FPLMTS) in the 2000MHz band before and after 2000. The system was formally named IMT-2000 in 1996 as the third generation mobile communication system (3G). (Computer science)

The goal of 3G is summed up as follows:

(A) Global standards, the use of uniform frequency bands to improve the efficiency of the spectrum;

(B) Provision of high-quality multimedia services;

(C) Strengthening the security secrecy function;

D require data transmission rates to reach 2mbit/s in indoor environments (walking 384kbit/s, garage 144kbit/s). Of course, it also has to be easy to smooth transition from 2G systems.

The 3G system uses Code Division multiple Access (CDMA) and packet switching technology. Compared with 2G, 3G system capacity increases, communication quality improved, and can achieve global seamless roaming, can provide users with voice, data, images, television and other multimedia services.

At present, mobile communication is in the smooth transition from 2G to 3G, but the goal of unified standard and frequency is not achieved. Now there are 5 different 3G standards, which are mainly ETSI to Gsmmap as the core network, FDDWCDMA as the wireless interface standards, ANSI IS-41 as the core network, FDDCDMA2000 as the wireless interface standards, And the same TDDTD-SCDMA of the core network and WCDMA as the standard of wireless interface.

3G Mobile Communication System has a great improvement over 2G, but it still can't meet the requirements of users. The main problem is:

(a) without a unified world standard, it is difficult to achieve global seamless roaming;

B The voice is transmitted on the infrastructure inherited from 2G, not on the IP network structure;

C) video transmission does not meet the requirements of high definition;

D the data rate, although improved, can be difficult to quickly transfer large text and large e-mail attachments.

2 ITU's vision for the post-3G

Considering the deficiencies of the 3G system, the ITU has proposed some enhancements to the current 3G system (which can be said to be 3G-modified or called 3). 5G): such as the introduction of high-speed downlink Packet Access (HSDPA) technology, the use of better modulation technology, so as to achieve a mbit/s downlink rate, all users in the honeycomb share this capacity of the users in the zone without interference to give a wider bandwidth. Also such as the IP from the core network (CN) extended to the Wireless access Network (RAN), so that the CN and wireless local area network (WLAN) interconnection, support multimedia broadcasting and multicast.

The ITU also began to consider the future of the 3G (BEyOND IMT-2000) mobile communication system, and proposed the concept, framework of the post 3G Mobile communication system, the main content, the key data rate requirement and the research development process.

The specifics of the post 3G or 4G mobile communication system are now hard to imagine, but the post-3G or 4G Broadband mobile communications system will certainly not be the exclusive hive of the previous generations. After 3G or 4G system will bring together wireless access, wireless mobile, wireless LAN and other advanced technology, and combined with all IP network, to provide users with a safe and reliable, easy to use wireless mobile Internet system, can meet the human society in the next few years the requirements of mobile communications business.

3 Some current research trends

The ITU is planning to solicit plans for a post 3G or 4G Mobile communication system in 2004. Some relevant departments, institutions and schools in the world have been actively organizing their efforts to explore and carry out a lot of research work.

3. 1 Mobile Broadband system (MBS)

Mobile Broadband System (MBS) is a mobile broadband design program organized by some companies and schools in the European Commission. Its physical layer is based on the TDMA variant of most 2G telephones, and the higher level is based on ATM. Previous generations of mobile communications are mainly used for telephone calls, or some other business such as SMS, while MBS is to separate various forms of services. It is a large data channel facility that can be used separately for various forms of service.

It is estimated that the system will be commercialized for another 15 years, and it may begin to be used in 2010, with a large expansion of services estimated to 2020 years. During this period, technical indicators to change, the physical layer will be to overcome the wireless signal multipath transmission interference design based on orthogonal frequency Division Multiplexing (OFDM) technology, while abandoning ATM to face IPv6, to use the previously used GHz or GHz spectrum to meet the extremely wide bandwidth requirements.

3. 2 IEEE 802. 11 series

Currently, the fastest way to access the Internet in Mobile is through a wireless LAN. The United States IEEE developed IEEE 802 at the end of last century. 11 Standard series, of which 802. 11, 802. 11A and 802. 11B, as well as 802 of the research and development. 11G. 802. 11 technology is not very mature, not see commercial products; 802. 11A has the technical advantage, but the difficulty is big, the commercialization is later, the current market massive use is 802. 11B.

802. 11B (often called Wi-Fi) works at 2 without a license. 4 GHz band, using direct sequence spread spectrum (DSSS) technology, the maximum physical rate of one mbit/s, the actual amount (third layer) up to 6 mbit/s, if used as a honeycomb, think it can reach 3. 5G requirements.

802. 11A work at the 5 GHz band without certification, using the DSSS relatively complex orthogonal frequency division Multiplexing (OFDM) technology, the highest physical rate of mbit/s, the actual amount of the maximum can reach mbit/s. In addition to the data rate is relatively high, the frequency band is relatively wide, less interference, 5 GHz band channel number is always more than 802. The advantages of 11A. 802. The problem of the 11A existence is with 802. Compatibility and interoperability issues with 11B products.

In order to solve interoperability, IEEE developed 802. 11G to extend 802. 11B data rates and coverage and are compatible. 802. 11B and 802. The 11A coverage ranges from M and M respectively. 802. 11G uses 2. 4 GHz band, the use of OFDA technology, covering the range is expected to reach the M, but the rate is not 802. 11A fast, the physical layer rate is up to mbit/s, and the actual amount is only one mbit/s.

In order to increase the 802. 11 series of working capability, IEEE is studying and developing some new standards:

A) 802. 11E is designed to make 802. 11 Network QoS performance has been improved, using equivalent TDMA mode to replace Ethernet similar MAC layer, and to add special error correction for important business;

B) 802. The 11F intends to improve the 802. The handover (handover) mechanism in 11 enables users to remain connected when roaming between 2 different wireless channel switching segments or 2 access points (APs) attached to different networks, which is important for the mobility of wireless LANs;

C) 802. 11H to make 802. 11A Radio transmitting power and channel selection are better controlled.

D) 802. 11I focus on 802 increase. 11 system security and confidentiality issues.

Like the MBS in GHz, the problem with wireless LAN access is that each access point or base station can reach a very small distance, about M, the outdoor environment is good in the case of only hundreds of meters. This means that wireless LANs are limited to a handful of hot spots in the public application, such as the airport Passenger lounge, the Convention center, the Grand Hotel and the business district. To expand the scope of services, some vendors would like to collaborate with existing dedicated wireless LANs, so that they can fill the gap.

Some cellular operators intend to invest in the wireless LAN industry, using their existing billing infrastructure and customer relationships to provide cellular phones and 802. 11 combined components.

IEEE is working on a metropolitan area network (HUMAN) program called High speed without approval. It is a use 802. 11A wireless local loop system with point-to-point link. Laptops and cellular phone users can be within the building, by 802. The 11A LAN is connected to the outside by a directional transceiver on the roof.

3. 3 HIPErLAN2

HIPErLAN2 is the European Telecommunication Standards Association (ETSI) began to organize research and development at the end of last century.