文件名称：前向业务信道(F-TCH)-华为CDMA2000
文件大小：3.95MB
文件格式：PPT
更新时间：2024-05-13 05:52:04
cdma
前向业务信道(F-TCH) I Q I 信道PN序列 1.2288 Mcps PN 1.2288 Mcps 重复的符号 19.2kbps 8.6kbps 9.6 kbps 4.8kbps 2.4kbps 1.2kbps 增加帧质量指示比特(12,10,8,6) 增加8位帧尾比特 卷积编码 r=1/2,K=9 符号重复 前向业务信道信息比特 (172/80/40 or 16bits/帧) 块交织 19.2kbps MUX 长发生成器 功率控制比特 Q 信道PN序列 1.2288 Mcps 基带滤波 基带滤波 I(t) Q(t) 抽取器 抽取器 + + + X X ∑ QPSK 调制 4.0kbps 2.0kbps 0.8kbps 19.2sybps 9.6sybps 4.8kbps 2.4sybps Sin(2pfct) Cos(2pfct) 用于在前向传送BTS的数据和信令 Walsh 码 CDMA 空中接口 19.2kbps Symbol repetition makes symbol streams at different rates adapted to those at the rate of 19.2k. The original symbol stream at the rate of 19.2Kbps will not be repeated, 9.6Kbps symbol stream will be repeated once, 4.8Kbps symbol stream will be repeated twice…. Then, after the interleaving, long code scrambling, spreading, etc., the transmitting power of repeated bits is reduced during the transmission. Thus, variable rates can be achieved and the system capacity be increased. During the long code scrambling, one chip will be sampled from every 64 long code chips for exclusive-or with a scrambled chip. A forward traffic channel includes a power control sub-channel and a power control bit is used to instruct an MS to increase or decrease the transmitting power. Each forward traffic channel frame (20ms) can be divided into 16 power control groups (each group is 1.25ms long). Each power control group contains a power control bit , therefore the rate of reverse fast power control is 16* (1s/20ms)=800bps. And the power control bit is embedded right during the long code scrambling.