The present disclosure discloses a system and method for determining deterioration in call quality between one or more wireless end-users based on codec characteristics. Specifically, a network device determines a codec associated with a call between two client devices. Then, the network device determines a transmission rate based on the codec. Moreover, the network device estimates a number of packets to be received by an access point that a first client device is associated with based on the transmission rate, and compares the estimated number of packets to an actual number of packets received by the access point. If a difference between the estimated number and the actual number of packets exceeds a threshold, the network device diagnoses that a poor call quality associated with the call is due to either the first client device or network connectivity between the first client device and the access point.