1.   THE INTRODUCTION OF IMT-2000

The third generation mobile telecommunication or 3G is defined by ITU as the IMT-2000(International Mobile Telecommunication-2000). Its design object is to provide more capacity and better call quanlity than 2G, to realize the seamless roaming globally and provide various of seervices including voice,data and  multimedia,and can be compatible with 2G. The mainly characteristics of 3G are to provide the mobile multimedia services by the transmission rate of 144kb/s at the high speed, 384kb/s at the speed of walking and 2Mb/s indoors.

IMT-2000 mainly has two parts:the core network（CN）and radio access network（RAN）. The CN can based on MAP GSM network and IS-41 CDMA network. There are 5 kinds of  RAN standard, including 2 kinds of TDMA standard and 3 kinds of CDMA standard which are dominant,including WCDMA （IMT-2000 CDMA-DS），cdma2000 （IMT-2000 CDMA-MC）and TD-SCDMA （IMT-2000 CDMA TDD）. WCDMA and cdma2000 belong to FDD mode and TD-SCDMA belongs to TDD mode. One of the international telecoms standardization organization,3GPP is responsible for the constitution of GSM,WCDMA and TD-SCDMA. 3GPP2 is responsible for the constitution of narrowband CDMA and cdma2000.

2．THE POSITION OF TD-SCDMA IN IMT-2000

TD-SCDMA was accepted by ITU as one of its international standard in the November of 1999 and formally adopted by ITU as one of 3G international standard in the May of 2000. This is a significant milestone in the chinese telecoms histroy. And TD-SCDMA was accepted by 3GPP as one of 3G international standard and included in 3GPP release 4 in the March of 2001, this signed that TD-SCDMA was accepted by the most mobile telecoms vendors around the world and it provides for chinese telecoms vendors a new opportunity to make an integrated breakthrough in the next generation telecoms field.

TD-SCDMA offers a smooth and seamless way of upgrading existing GSM networks for advanced 3G mobile networks and services. When TD-SCDMA base stations are installed in an existing GSM system, the radio network layout can be retained and existing transmission links can be reused. What's more, technical risks are reduced because this 3G services will develop from a well-known GSM network. TD-SCDMA provides a spectrum efficiency 3 to 5 times greater than GSM. Together with the added ability to handle symmetric and asymmetric services as well as flexible data rates - each carrier can now be used with maximum efficiency. This allows it handle higher traffic densities within each cell and in case of areas with low traffic the cells can be increased.

• Seamless GSM to 3G upgrades
• Re-use of GSM resources
• Reduced migration risks
• 3 to 5 times greater spectrum efficiency
• Increased capacity
• Operational Advantages

Operational Advantages

The 3G air interface used in combination with your established infrastructure dramatically shortens the time to market for new 3G services. And this also speeds up your ability to provide customers 3G mobile Internet applications. It also enables the network's spectrum to be easily increased, keeping in step with user numbers, data throughput and quickly overcoming GSM capacity problems. At the same time, the new TD-SCDMA components can be fitted into existing operation and maintenance strategies.

• 3G air interface
• Rapid market introduction of 3G services
• Additional spectrum for GSM networks
• Simple operation and maintenance

Commercial Advantages

TD-SCDMA gives GSM operators the opportunity to offer 3G services without making major new infrastructure investments. In addition, the total amount of your 3G investment can now be spread over a longer period of time. By efficiently utilizing existing GSM infrastructure, the total 3G investment risk is reduced to a minimum. This also means spectrum license fees can be used economically to generate new 3G revenues from Internet, Intranet and multimedia applications earlier.

• Minimized new investment
• Economic use of license fees
• Early generation of 3G revenues
• Designed for success