Realization and Performance Evaluation of IMS Multimedia Telephony for HSPA

The proposed voice over IP (VoIP) over HSPA solution targets high capacity as well as coverage and speech quality comparable to circuit switched (CS) speech. The VoIP over HSPA radio bearer realization includes one radio link control (RLC) un-acknowledged mode for the speech media. Parallel signaling radio bearers are also transmitted using HSPA access. Due to the flexibility of IP and HSPA, both narrow-band and wideband speech codecs work well. A delay sensitive scheduler is selected for the downlink transmission. For the uplink, the non-scheduled mode is selected. Coverage and quality can, with simulations, be shown to be at least as good as CS speech according to 3GPP ReI. 99 specifications. Similarly, capacity evaluations show that VoIP over HSPA has the potential of matching or exceeding CS speech capacity, depending on scenario. Finally, end to end simulations show that the maximum allowed delay of single links seldom occurs for uplink and downlink simultaneously, resulting in a lower perceived end-to-end delay than expected most of the time