Kristofer Sandlund

Performance Evaluation of HSDPA Mobility for Voice Over IP

In this paper we evaluate the performance of the serving HS-DSCH cell change procedure for delay sensitive services, like voice over IP (VoIP). The impact of the signaling procedure delay on the user plane performance is studied by means of dynamic system simulations. The simulation results show that within the studied range, the duration of the signaling procedure starts to impact performance only for terminals moving 50 km/h, or faster. Parameter tuning and combining the procedures for active set update and change of best HS cell can considerably improve the performance, so that even at 120 km/h, less than 2% of the handovers suffer interruptions longer than 100 ms. Thus, the HSDPA handover procedure in Rel-6 can be made fast enough to accommodate VoIP users traveling at 120 km/h with acceptable conversation quality.

LTE In-Band Relay Prototype and Field Measurement

Relaying is a feature defined in LTE Release 10 to provide coverage in new areas and/or to improve cell-edge throughput. For the purpose of investigating relays performance in a real network, an LTE TDD in-band relay prototype was developed. Based on this prototype some field measurements were conducted using LTE Release-8 terminals. Both indoor scenarios and outdoor scenarios were tested. Measurement results show that relays (once properly deployed) provide good coverage in the coverage holes of a donor eNB. Besides coverage extension, relays can also improve data rate in the poorly-covered area of a donor eNB, i.e. cell edge. The throughput of a terminal served by this relay prototype reaches around 8 Mbps in the uplink and 20 Mbps in the downlink. Regarding latency, given uplink data is always scheduled, the measured round-trip time via the relay is around 10 ms larger than that directly via the donor eNB.

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