WCDMA

Principles of the WCDMA SystemGSM-to-UMTS Training Series_V1.0HUAWEI TECHNOLOGIES CO., LTD.www.huawei.comHuawei ConfidentialInternalHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential1Page 2Major Differences Between WCDMA and GSM Air InterfacesGSMWCDMACarrier spacing200 kHz5 MHzFrequency reuse coefficient1-181Method for differentiating cellsFrequency + BSICFrequency + Scrambling codePower control frequency2 Hz or lower1500 HzQoS controlNetwork planning (frequency planning)Algorithm of radio resource managementFrequency diversityFrequency hoppingThe 3.84-MHz bandwidth enables the network to use the rake receiver for multipath diversityPacket dataTimeslot-based scheduling in the GPRSPacket scheduling based on loadsDownlink transmit diversityNot supported by the standards but applicableSupported for increasing the capacity of downlinksHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential2Open loop transmit diversity: STTD and TSTD Closed loop transmit diversity: by means of the FBI The handover mode is also a major difference between the GSM and the WCDMA. The GSM uses hard handover while the CDMA mainly uses soft handover. Air interface interferences in the WCDMA network are mainly derived from terminal users while those in the GSM network are from poor frequency planning. Page 3185019001950200020502100215022002250ITUEuropeUSAMSSPCSADBBCDCEFAFEMSSReserveBroadcast auxiliary2165 MHz1990 MHz1850190019502000205021002150220022501880 MHz1980 MHzUMTSGSM 1800DECTMSS1885 MHz2025 MHz2010 MHzIMT 2000MSSUMTSJapanMSSIMT 2000MSSIMT 2000PHS18951918BC1885AA.2170 MHzIMT 20002110 MHz2170 MHzMSSMSSCDMATDDWLLFDDWLL19802025 MHzGSM1800CDMAFDDWLL196019201945Chinacellular(1)cellular(2)cellular(2)1805 MHz186518651870188518901895191019301945196519701975Allocation of 3G SpectrumHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential3The International Telecommunication Union (ITU) has allocated the 230 MHz frequency for the IMT-2000, namely, 18850 MHz to 2025 MHz for uplinks and 2110 MHz to 2200 MHz for downlinks, totally 230 MHz. 1980 MHz to 2010 MHz (ground-to-air) and 2170 MHz to 2200 MHz (air-to-ground) are used for the mobile satellite service. The frequencies for uplinks and downlinks are asymmetrical so that the dualband FDD mode and the single-band TDD mode can be used. Such planning has been passed in the WRC92. According to the frequency allocation and technical standards of the IMT-2000 stipulated by the ITU and China's regulations on radio frequency allocation, as well as the actual use of radio frequency in China, matters related to the frequency planning for China's 3G public mobile communication system are as follows: Working bands of the 3G public mobile communication system: 1. Main working bands: Frequency division duplex (FDD) mode: 19201980 MHz/21102170 MHz; Time division duplex (TDD) mode: 18801920 MHz/20102025 MHz 2. Supplementary working bands: FDD mode: 17551785 MHz/18501880 MHz; TDD mode: 23002400 MHz, shared with the radio location service. The sharing standards will be constituted separately. 3. Working bands of the satellite mobile communication system: 19802010 MHz/21702200 MHz

In Europe, the frequency bands for land communication are 1900 to 1980 MHz, 2010 to 2025 MHz, and 2110 to 2170 MHz, totally 155 MHz. In north America, the conditions are more complex, as shown in the figure. The low frequency band (1850 to 1990 MHz) of the 3G system has been allocated to the PCS and already divided into multiple bands of 2x15 MHz and 2x5 MHz. The IMT-2000 spectrums occupied by the PCS service have been adjusted, but after adjustment, the uplink frequency band of the IMT-2000 must still be shared with the downlink frequency band of the PCS. Such arrangement does not accord with the general configuration in which the BS transmits signals at a higher frequency band and receives signals at a lower band. In Japan, the frequency band of 1893.5 to 1919.6 MHz has been used for the PHS, and the frequency bands (1920 to 1980 MHz, 2110 to 2170 MHz, and 2010 to 2025 MHz) for the 3G mobile communication can also be provided, that is, 2 x 60 MHz + 15 MHz, totally 135 MHz. Currently, Japan is working at solving the problem of conflict with the 3G mobile communication frequencies. In South Korea, totally 170 MHz are used for the 3G mobile communication, as proposed by the ITU. Page 4Comparison of Frequency Computation Between the WCDMA and the GSMMain working bands: 19201980 MHz/21102170 MHzFormula for computing WCDMA frequencies:Frequency number = Frequency x 5Central frequency number of uplink: 96129888Central frequency number of downlink: 1056210838Supplementary working bands: 17551785 MHz/18501880 MHz The currently existing GSM frequency bands of China Mobile and China Union can be used for the WCDMA later. Computing WCDMA frequenciesGSM900: BS reception: f1 (n) = 890 + n x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 45 MHz

GSM1800: BS reception: f1 (n) = 1710 + (n - 511) x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 95 MHzComputing GSM frequenciesHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential4EGSM BS reception: f1 (n) = 890 + (n -1024) x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 45 MHzPage 5Contents

Chapter 1 Introduction: GSM and WCDMAChapter 2 Overview of CDMA PrinciplesChapter 3 WCDMA Radio Interface Physical ChannelChapter 4 Overview of Radio Resource ManagementChapter 5 Technical Features of WCDMA FDDHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential5Page 6Overview of CDMA PrinciplesRadio Propagation EnvironmentMultiple Access Technology and Duplex TechnologyCDMA Principles and Rake Receiver

HUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential6Page 7Multipath Environment

TimeRx signals

Tx signalsIntensityHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential7The delay for the signals reaching the receiver from different paths differs. As a result, their phases are also different. In-phase signals are mutually strengthened, while out-of-phase signals are mutually weakened.The GSM system cannot distinguish signals from different paths. Therefore, the only way is to add vectors. In this way, however, the received signals fluctuate greatly.The CDMA system can distinguish signals from multiple paths through the rake receiver. Then, the in-phase signals are superimposed after phase correction. This can ensure the maximum reception efficiency and effectively resist the impact of multipath fading.Page 8Fading

Tx data

Rx dataHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential8Page 9Fading Distance (m)Rx power (dBm)102030-20-40-60Slow fadingFast fadingHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential9Slow fading Slow fading, also called shadow fading, refers to the shadow effect caused by obstructions. In slow fading, the intensity of received signals weakens but the mean value of the field strength varies slowly with geographical changes. In slow fading, the mean value of the field strength follows logarithmic normal distribution and is related to the location or position. The fading speed depends on the movement speed of a user equipment (UE).Fast fading Fast fading means that the amplitude and phase of multiplexed wavelength vary greatly with the movement of a UE. The deep fading points are spatially distributed at the interval of nearly half a wavelength. Because the field strength complies with Rayleigh distribution, fast fading is also called Rayleigh fading. The fading amplitude and phase are random. Fast fading is further divided into the following types: Time-selective fading: Fast movement of a user generates a Doppler effect in the frequency domain and thus causes frequency diffusion. As a result, time-selective fading .Space-selective fading: The fading features differ in different places and on different transmission paths.Frequency-selective fading: The fading features vary with frequencies, thus causing delay diffusion and further frequency-selective fading.The common methods to reduce the impact of fast fading on radio communication include space diversity, frequency diversity, and time diversity. Page 10Frequency-Selective FadingNarrowband system (GSM)Large fadingTx signalsRx fading signalsFrequencyFrequencyIntensityIntensityLarge fadingTx signalsRx fading signalsFrequencyFrequencyIntensityIntensityBroadband system (CDMA)HUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential10Suppose there is 200 kHz-wide fading at the transmission frequency. In the narrowband GSM system, it means that signals at this frequency fade because the bandwidth of a frequency is 200 kHz in the system. In the broadband WCDMA system, however, useful signals are distributed on the 3.84 MHz band. Therefore, most useful signals are not affected after 200 kHz-wide fading and the system can still demodulate signals correctly. This is similar to the laser holographic technology.Therefore, the CDMA system has an enhanced capability against frequency-selective fading.The GSM system can also obtain a similar anti-fading capability by adopting the frequency hopping technology. Page 11

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