基于国标Soft—Metric的算法设计与FPGA实现

Study of Soft-Metric arithmetic on National DTTB Standard

多进制正交振幅调制（MQAM）是在中、大容量数字通信系统大量使用的一种载波键控方式。MQAM是对载波的振幅和相位同时进行调制的一种复合的调制形式．他同时利用了载波的幅度和相位来传递信息比特。在调制的进制数较高时，信号矢量集的分布也比较合理，同时实现起来也比较方便，具有更大的符号率，从而获得更高的系统效率。通常由符号率确定占用带宽，因此每个符号的比特（基本信息单元）越多，效率就越高：基于地面数字电视国标ADTB—T规格，采用了一种QAM软判决解映射算法，其中以32QAM为倒进行说明其性能良好．有较好的可行性。

Multi-band orthogonal amplitude modulation （MQAM） is in, large-capacity digital communications system large-scale use of a carrier keying way. MQAM is a complex form of modulation that the cartier amplitude and phase at the same time, while the rate of use of carrier phase and to transmit information bits. Modulation in the band higher, set of signal vector distribution more reasonable, at the same time it is also more convenient, more symbol rate, and that resulting in higher system efficiency, occupied bandwidth is usually confirm by the Symbol rate, so every bit of symbols （the basic unit of information）, the more the higher efficiency. According to the terrestrial digital TV GB ADTB-T specifications, adopted a soft decision of the QAM mapping algorithm, 32 QAM as an example to explain their good performance, a better possibility.