In order to accommodate the growing traffic demand in GSM cellular networks, several features are continuously being developed to improve the voice capacity of GSM/EDGE Radio Access network (GERAN). In this paper we investigate the capacity of a GSM network considering the use of some of these features, namely, interference rejection combining (IRC), single-antenna interference cancelation (SAIC), sourceadaptive AMR (SA-AMR), dynamic frequency and channel allocation (DFCA), and 8-PSK voice channels. These techniques have been previously investigated individually in the literature, but here we focus on the system-level impact of the interactions among them. We show that the proper combination of these features increases the spectral efficiency of speech channels in GERAN.