TD-CDMA and TD-SCDMA

1. TD-CDMA就是UTRA TDD，與TD-SCDMA同屬相同的3G家族。被ITU認可為IMT-2000 CDMA TDD (IMT-TD), 這兩個親兄弟的血緣近似度不亞於人類與黑猩猩之間的DNA差別, 兩者最大的特徵差異在於chip rate的不同, TD-SCDMA只有1.28Mcps, TD-CDMA與WCDMA/FDD一樣, 都是3.84 Mcps.

2. TD-SCDMA是中國大陸第一個獲世界認可的無線通信標準(CWTS), 內需市場與技術資源都很充足, 因此聲勢浩大, 常常讓台灣的技術觀察家忽略還有TD-CDMA的存在, 兩者間似乎有瑜亮情節, TD-CDMA只能分食中國市場以外的TDD頻譜.

3. 技術基本參數
TD-CDMA的基本參數：
TDD Technical SummaryFrequency band:
1900 MHz -1920 MHz and 2010 MHz - 2025 MHz (Time Division Duplex) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency, but by guard period.
Minimum frequency band required: ~ 5MHz, ~ 1.6MHz with 1.28 Mcps
Frequency re-use: 1
Voice coding: AMR (and GSM EFR) codec
Channel coding: Convolutional coding, Turbo code for high rate data
TDMA frame consist of 15 timeslots
Each time slot can be transmit of receive
Duplexer not needed
Asymmetric connection supported
Data by packet and circuit switch
QPSK modulationReceiver: Joint Detection, (mobile: Rake)
Chip rate: 3.84 Mcps or 1.28 Mcps
Channel raster: 200 kHz
Maximum RF ch bit rate (kbps): ~ 3.3Mbps (1/2 rate coding, spreading factor 1, 15 timeslots, ex overheads), but interference limited
Frame length: 10msNumber of slots / frame: 15
Handovers: Hard
Power control period: 100 Hz or 200 Hz UL, ~ 800 Hz DL
Power control step size: 1, 2, 3 dB (Variable)
Power control range: UL 65dB, DL 30dB
Mobile peak power: Power class 1: +33 dBm (+1dB/-3dB) = 2W; class 2 +27 dBm, class 3 +24 dBm, class 4 +21 dBm
Number of unique base station identification codes: 512/frequency
Physical layer spreading factors: 1, 2, 4, 8, 16

TD-SCDMA的基本參數：
Frequency band: 2010 MHz - 2025 MHz in China (WLL 1900 MHz - 1920 MHz)
Minimum frequency band required: 1.6MHz
Frequency reuse: 1 (or 3)
Chip rate: 1.28 Mcps
Frame length: 10msNumber of slots: 7
Modulation: QPSK or 8-PSK
Voice data rate: 8kbit/s
Circuit switched services: 12.2 kbits/s, 64 kbits/s, 144 kbits/s, 384 kbits/s, 2048 kbits/s
Packet data: 9.6kbits/s, 64kbits/s, 144kbits/s, 384kbits/s, 2048kbits/s
Receiver: Joint Detection, (mobile: Rake)
Power control period: 200 Hz
Number of slots / frame: 7
Frame length: 5ms
Multi carrier: option
Handovers: Hard
Smart antennas
Baton handover
Uplink synchronisation
Physical layer spreading factors: 1, 2, 4, 8, 16

4. 相關網站:
- UMTS TDD
- CWTS (中國通信標準化協會)


5. 參考資料:
[1] UMTS World: technology/TD-CDMA, technology/TD-SCDMA
[2] Wikipedia: UMTS-TDD
[3] NextWave Wireless

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