Several methods are used to achieve read depth normalization:
1. Down-Sampling: Reducing the number of reads in higher-depth samples to match those with lower depth. 2. RPKM/FPKM/TPM: Normalizing read counts by considering the length of genes and the total number of reads. 3. Quantile Normalization: Aligning the distribution of read counts across samples. 4. DESeq/edgeR: Statistical packages that model read counts and apply normalization techniques.