Just had a theoretical question. I'm reading a book on LTE, and I came across an introductory section that talks about using higher modulation with channel coding. I understand that usually using modulation schemes like 16 QAM and 64 QAM will require more Eb/No at the receiver end as compared to QPSK. But then they talk about the higher modulations being more efficient when combined with channel coding, that is, they require a lower Eb/No at the receiver as compared to QPSK. The example the books talks about is as follows:
"As an example, if a bandwidth utilization of close to 2 information bits per modulation symbol is required, QPSK modulation would allow for very limited channel coding (channel-coding rate close to 1). On the other hand, the use of 16QAM modulation would allow for a channel-coding rate of the order of one-half."
I'm confused about the second part of the statement. How do we get a channel-coding rate of one-half? Can anyone shed some light on this or perhaps point me to something I can read to get a better understanding?