Nowadays, wireless network technology becomes one of the most popular technologies, especially IEEE 802.11n. However, there are many conditions that cause performance to decrease. This study has been conducted to analyze the IEEE 802.11n standard while using Voice over IP (VoIP) in the Enhanced distributed channel access (EDCA) mode which is supported in IEEE 802.11e. The study was conducted in 2 states of traffic conditions, which are free-traffic and congested traffic, and to study the effects and differences. From this study, it has been found that EDCA mode can help to achieve small performance gain for VoIP but with limitation to deal with very high traffic.