VoIP over realistic IEEE 802.16e system scenarios: The uplink direction

As opposed to best-effort data applications, which tolerate a lot of flexibility from a system resource allocation standpoint, real-time services such as Voice over IP (VoIP) have very stringent packet delivery requirements, characterized by tight air-interface delay budgets in the order of tens of milliseconds (ms). Speech packets are short by nature and need to be carried out with minimal packet loss probability, typically no more than 1%-2%. These constraints are even more limiting in the uplink, where the available power at the mobile terminal - couple of hundreds of milliWatts (mW) - is much lower compared to the available power at the base station in the downlink (tens of Watts (W)). The paper addresses the VoIP service in the context of the limiting uplink direction of an IEEE 802.16e system via a comprehensive system simulation study.