gsm to umts03

WCDMA

Principles of the WCDMA SystemGSM-to-UMTS Training Series_V1.0HUAWEI TECHNOLOGIES CO., LTD.www.huawei.comHuawei ConfidentialInternalHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential1Page 2Spreading Factor and Service RateSymbol rate = (service rate + check code) channel code repetition or punching rateFor WCDMA, if the service rate is 384 Kbit/s and the channel code is 1/3 Turbo, the symbol rate is 960 Kbit/s.For CDMA2000-1x, if the service rate is 9.6 Kbit/s and the channel code is 1/3 convolutional code, the symbol rate is 19.2 Kbit/s.Chip rate = symbol rate spreading factorFor WCDMA, if the chip rate is 3.84 MHz and the spreading factor is 4, the symbol rate is 960 Kbit/s.For CDMA2000-1x, if the chip rate is 1.2288 MHz and the spreading factor is 64, the symbol rate is 19.2 Kbit/s.HUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential2Page 3Basic Block Diagram of CDMA System Source codingInterleavingChannel coding and interleavingScramblingSpreadingModulationRF emissionSource decodingdeinterleavingDe-interleavingChannel decodingDescramblingDe-spreadingDemodulationRF receptionRadio channelHUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential3The difference between the GSM and the CDMA systems is that: The CDMA system uses spreading, de-spreading, scrambling, and descrambling, while the GSM system uses burst pulse formatting, encryption, and decryption. Other processes are the same. Page 4Source Coding in WCDMASource codingInterleavingChannel coding and interleavingScramblingSpreadingModulationRF emissionThe WCDMA system adopts the adaptive multi-rate (AMR) speech coding.A total of eight coding modes are available. The coding rate ranges from 12.2 Kbit/s to 4.75 Kbit/s.Multiple voice rates are compatible with the coding modes used by current mainstream mobile communication systems. This facilitates the design of multi-mode terminals. The system automatically adjusts the voice rate according to the distance between the user and the NodeB, thus reducing the number of handovers and call drop. The system automatically decreases the voice rate of some users according to the cell load, thus saving power and containing more users. HUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential4Page 5

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HUAWEI TECHNOLOGIES CO., LTD.Huawei ConfidentialPage 8Source codingInterleavingChannel coding and interleavingScramblingSpreadingModulationRF emissionChannel Coding in WCDMAChannel coding can enhance symbol correlation to recover signals in the case of interference.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25Code typeVoice service: convolutional code (1/2 and 1/3).Data service: Turbo code (1/3). HUAWEI TECHNOLOGIES CO., LTD.Huawei Confidential8Page 9

HUAWEI TECHNOLOGIES CO., LTD.Huawei ConfidentialThe original data is fed to the FEC generator, which in this caseproduces twice as much data. A coder that produces this increase,that is, two bits out for one bit in is known as a 1/2 rate coder. Onethat produces three bits of information for one input is known as a1/3 rate coder. This output is not simply the input data repeated; itwill be subjected to noise superimposed by the RF transmissionpath.In the receiver, a device known as a Viterbi Decoder is used tocorrect these errors and recover the original data. This deviceworks by taking the actual level of the data and estimating whetherthis was a 1 or a 0 when it left the transmitter, rather than usethresholds for 1 and 0.9Page 10


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