Qiwei Wang Guangliang Ren A Partial Gaussian Tree Approximation (PGTA) Detector for Random Multiple Access Oriented SCMA Uplink With Codebook Collisions. 2295-2308 2021 20 IEEE Trans. Wirel. Commun. 4 https://doi.org/10.1109/TWC.2020.3041295 db/journals/twc/twc20.html#WangR21