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  1. 1. 3G and TD-SCDMA 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. In order to integrate TD-SCDMA into UTRA,new coordination began within 3GPP. The first pace includes 3.84 Mcps TD-CDMA and 1.28 Mcps
  2. 2. TD-SCDMA according to the difference of chip rate.Many work are undergoing within the 3GPP tech spec groups,including WG1(physical layer), WG2(protocol layer, MAS and RLC), WG3(interface, IuB and IuR)and WG4(RF requirement and test criterion).These standardization work are to adopt TD-SCDMA as one part of UTRA Release 2000, these spec are expounded in the 3GPP and 3GPP2 and have been one part of IMT-2000 of ITU. Hereafter, the two kinds of TDD technologies have finished the integration in the March of 2001.Thus TD-SCDMA has been one part of 3GPP R4 and forms the integrated TD-SCDMA 3G international standard. Recently, TD-SCDMA has new advance in 3GPP release R4. On the release R4 standard simulation and forming, more than 500 technique papers are issued to ITU and 3GPP based on the link level and system level simulation. As matured as WCDMA/FDD, release R4 has been fixed on time. Meanwhile the standard has been maintained and modified, LCR TDD Uu is modified little, and few paper on NBAP of Iub is issued and part of the RRM RF parameters have been changed after the research. TD-SCDMA also participates the update of 3GPP release R5 and R6 actively. The hybrid ARQ and AMC (adaptive modulation and coding) are adopted in HSDPA (high speed downlink packet access). In current release R5, The HSDPA of TDD has been finished basically; the advanced antenna techniques and DSP schemes of MIMO have enhanced the performance of wireless system greatly, some key techniques are analyzed, researched and simulated. About the research on 3G 2500MHz-2690MHz, the extended frequency band allocation and the existence scheme of FDD and TDD has been finished. According to the 3GPP specification, the harmonization of TD-SCDMA and WLAN includes 6 phases: in the 1st phase, the networks are built individually, and only the accounting bill is unified; in the 2nd phase, the authentication/accounting is unified, WLAN only provides IP service; in 3rd phase, WLAN can be provided PS packet service from TD-SCDMA, such as IMS, LCS, etc.; In 4th phase, the handover and unified service are provided between WLAN and TD-SCDMA, and certain break and packet loss are permitted, but the service reset up is unnecessary ;in 5th phase, the seamless handover is provided between WLAN and TD- SCDMA, the QoS is as good as intra handover of TD-SCDMA; in 6th phase, the seamless handover of CS domain between WLAN and TD- SCDMA.
  3. 3. The joint research of TD-SCDMA and Ad hoc network has been performed, such as peer-to-peer communication, multi-hop/dynamic top structure, etc. The transceiver of Ad hoc network terminal is better to work at the same frequency band, and TD-SCDMA working as a TDD mode meets this requirement. The technique advantage of combination of TD- SCDMA and Ad hoc network, the cell coverage can be extended by relay, and thus the capacity can be improved; The peer to peer communication can decrease the consumption of the radio resource, so the TD-SCDMA can be further developed on the current physical layer. TD-SCDMA and WCDMA are all the member of 3GPP, one is TDD and the other is FDD, the fix of the 3GPP release R4 (and the back compatible release R99) means the stability of TD-SCDMA release R4, and during the perfection of the release R5, R6, the corresponding part of the TD-SCDMA is been perfected at the same time. It is the same to say that TD-SCDMA is as matured as WCDMA. Currently, the main task of TD-SCDMA is to track the technique advance of beyond 3G. 3. THE ALLOCATION OF 3G TDD SPECTRUM IN THE WORLD In every country in the world, the radio frequency for mobile telecommunication is allocated by national related institute.The 3G spectrum inlcudes FDD(Frequency Division Duplex) and TDD(Time Division Duplex) which used for TD-SCDMA system. At present, some countries have allocated the TDD spectrum, some countries are allocating the TDD spectrum , these provide the favorable condition for the large scale commercial use for TD-SCDMA in the world. The early deployment of TD-SCDMA in china will promote its global application. China will be the inaugurator of TD-SCDMA application trend from the following market analysis. The allocated TDD spectrum in the world as follows: Asia area China 155 MHz TDD spectrum allocated,
  4. 4. Licenses award scheduled in the late of 2004 or beginning of 2005 China - Hong Kong 4 Operators:5 MHz TDD South Korea 50MHz TDD Not yet licensed Japan 15MHz TDD not yet licensed China - Taiwan 4 Operators: 5MHz TDD Philippines License award scheduled ‘04 Indonesia 3G licenses by 2004 New Zealand 2 Operators: 5 MHz TDD 1 Operator: 10 MHz TDD Australia 4 Operators: 5 MHz TDD Singapore 3 Operators: 5 MHz TDD Malaysia License award scheduled ’02 India License award scheduled ’05 Europe area Belgium 4 Operators : 5 MHz TDD Netherlands 3 Operators : 5 MHz TDD Norway 4 Operators : 5 MHz TDD Sweden 4 Operators : 5 MHz TDD UK 4 Operators : 5 MHz TDD Finland 4 Operators : 5 MHz TDD Ireland 4 Operators : 5 MHz TDD Denmark 4 Operators : 5 MHz TDD Spain 4 Operators : 5 MHz TDD Germany 5 Operators : 5 MHz TDD Portugal 4 Operators : 5 MHz TDD Austria 1 Operators : 5 MHz TDD 2 Operators : 10 MHz TDD France 2 Operators : 5 MHz TDD Switzerland 4 Operators : 5 MHz TDD Italy 5 Operators : 5 MHz TDD Greece 4 Operators : 5 MHz TDD Figure 1: The allocated TDD spectrum in the world 4. Key Technologies TDMA/TDD Principle Employing a single carrier to both send and receive traffic it ptimizing the use of your radio resources.
  5. 5. Time Division Multiple Access (TDMA) in combination with Time Division Duplex (TDD) significantly improves network performance by allowing radio resources to process network traffic in both directions, per uplink and downlink. TDMA uses a 5 ms frame for repetitive transmissions. This frame is subdivided into 7 time slots, which can be flexibly assigned to either several users or to a single user who may require multiple time slots. TDD principles permit traffic to be uplinked (from the mobile terminal to the base station) and downlinked (from the base station to the mobile terminal) using the same frame and different time slots. For asymmetric services used with Internet access, where high data volumes are transmitted from the base station to the terminal, more time slots are used for the downlink than the uplink. For symmetric services used during telephone calls, where the same amount of data is transmitted in both directions, the time slots are split equally between the downlink and uplink. This capability of adapting the uplink/downlink format according to the data loads within a single frequency band increases the overall capacity of the air interface. This making TDMA/TDD operations ideal for 3G services. Smart Antennas Permit focusing of transmission beams, minimizing cell interference and increasing transmission capacity. TD-SCDMA base stations are equipped with Smart Antennas, which target signals to and from specific terminals and reduce intercell interference. The base station tracks the mobiles throughout the cell, so that the signal-to-interference ratio of the mobile terminal is improved by about 8 dB. In addition, Smart Antennas optimize the link budget and increase the capacity of a TD-SCDMA operator's radio interface. Joint Detection/Terminal Synchronization Increases transmission quality and air interface capacity. Joint Detection eliminates the multiple access interference (MAI) typically associated with multi-user access, through parallel processing of individual traffic streams. Terminal Synchronization improves the uplink signal's quality by precisely tuning the transmission timing of each individual terminal with respect to its base station. Together, this very efficient combination of Joint Detection and Terminal Synchronization enhances the coverage of a base station and allows TD-SCDMA deployments for macro, micro and pico cell applications. Soft handover It is the solution used to settle the interference among CDMA systems. Without soft handover, the service base station will require huge transmission power and this means its huge interference power to other base stations.It needs soft handover to advoid this,at this time, the mobile station connects with two or more base stations.The base station which requires the minimal transmission decides the transmission power of the mobile station to decrease the interference. But there are disadvantages of this mechanism: one is the used air interface capacity which is bigger than the actual required capacity and this leads to the decrease of
  6. 6. spectrum effiency. The other is it must send message from one RNC to many NodeB including another RNC possibly,so it needs fixed line capacity.Another is it needs to frequently use the detection and signaling resources among base stations,mobile stations and networks. TD-SCDMA system doesn’t exist cell breathing effect,so it doesn’t need soft handover. TD-SCDMA Features • Advanced 3G services allow high speed data, packet data, multimedia and excellent voice quality by connecting TD-SCDMA RAN to the GSM/GPRS network. • Access to new UMTS spectrum resources increase the network capacity. • Outstanding Spectrum efficiency (1.6 MHz bandwidth, 3 to 5 times higher than GSM, handling more traffic with fewer base stations) ensures economic use of spectrum. • Support of all radio network scenarios (Wide Area - Macro, Local Area - Micro, Hot Spots - Pico and Corporate Networks) allows full service coverage. • Best suited for mobile Internet 3G applications provided by the inherent flexibility of the technology. • Flexibility for asymmetric traffic, data rates and radio resource allocation, allows optimum adaptation of the radio access to the actual traffic load within the network.
  7. 7. 5. Advantages of TD-SCDMA Technical Advantages 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
  8. 8. • Designed for success