fixed effect? or random effect

[Yo_oY]

I applied proc glmmix in analysis. The level 2 variable is wave, that is the year when data were collected. The professor sugested it as fixed effect. The problem is there is no statement for fixed effect at level 2. How can I deal with this problem? Thank you.

[Yo_oY]

No one answers my questions. Is it not clear in my desciption of the problem?
I mean, the statement RANDOM intercept/sub=wave solution is to examine the random effect of wave. However, wave is supposed to be fixed effect since the year of data collection is fixed. Is there any methods to investigate fixed effect of variables which are at the level 2?
Thank you!!!!!

Yin