请教电学翻译 尤其是 with two bits per each 16QAM symbol ？

The second mapper 517b uses 16QAM modulation with two bits per each 16QAM symbol coming from a data stream originating at the first encoder 511a。
请教如何翻译？尤其是 with two bits per each 16QAM symbol ？？
多谢

The second mapper 517b uses 16QAM modulation [(with two bits per each 16QAM symbol) coming from a data stream originating at the first encoder 511a]。

with two bits per each 16QAM symbol 修饰 16QAM modulation

coming from a data stream originating at the first encoder 511a 修饰 16QAM symbol

16QAM symbol