you can use c,x bands for your application. check for Sentinal 1 C band SAR data in SLC format(Free data) for your area. https://scihub.esa.int/ check this website. you ll get data and toolbox as well.
C Band data can be used to estimate above ground biomass upto 75 Mg/ha, L band can be used for low biomass ranges upto 140 Mg/ha. P-band is capable of predicting biomass ranges from 80 - 200 Mg/ha. But there is a possibility of over estimation due to soil backscatter. So yes C band data can be used considereing your study area is iran.