How to decide ratio of in-band noise to quantization noise?

Hi, all,

I am reading "RF system design of transceivers" by Qizheng Gu.

When discussing the ADC dynamic range, he indicates the ratio of in-band noise to quantization noise should be considered in ADC's dynamic range, but I am confused how to decide/calculate the ratio?

In this book, the ratio is 12dB for CDMA system and 16dB for GSM. How to get the results?

Thanks!
Dopradar