A puzzle of power-constained LNA

I am reading "the design of CMOS RF IC" 2nd edition of Thomas. H. Lee. For the power constrained noise optimization of LNA, I have the following puzzle:
It is said the optimum device
Wopt=1/(3wLCoxRs).
The Wopt has no relation to the P(power dissipation), Does it mean that for different Power dissipation requirments, the optimun W is always the same?
And how the P is specified now? just by the biasing voltage?

I found it is hard to understand. Can you explain it to me or recommend a easy- understading paper on the subject?