Techniques for Performance Improvement of IMS Voice Calls in UMTS Networks

Abstract

The introduction of IMS (IP Multimedia Subsystem) in UMTS (Universal Mobile Telecommunication Services) architecture has made possible the implementation of end to end VoIP calls, thus integrating mobile and fixed networks in the IP technology. However we know that, without the use of some techniques, VoIP transmission can demand more resources, in terms of bandwidth and power. This is not a serious problem for fixed networks, but it is of special concern in the case of mobile systems, mainly because of the natural limitations of the air interface and the power restrictions of the user cellular equipment. In this paper we address the performance of voice calls in terms of transmitted power efficiency. We show that making convenient choices of standard procedures and using specific optimization techniques it is possible to turn IMS VoIP competitive with the traditional voice telephony service performed by the CS (Circuit Switching) counterpart of the UMTS.

Reducing the VoIP packet overhead in UMTS air interface

“…Also in this situation, the authors conclude that the efficiency of CRC is higher than the internet checksum. Concerning the VoIP transmission in IMS mode, references [8,9,10,11] show the possibility of further increasing the efficiency of packet transmission, relative to the aspect of power consumption: a new algorithm is presented in [8] that aims the optimization of padding operation, with the consequent minimization of waste caused by the extra bits used for this purpose; a new methodology is introduced in [9] for the optimization of the rate matching block's operation at the Physical Level of UMTS systems, thus allowing efficient multiplex of services with different QoS levels; references [10] and [11] present the results obtained when the above techniques are applied to an hypothetical voice call performed in both CS and PS (VoIP) systems, showing the gained efficiency in terms of power consumption, when compared to the traditional UMTS transmission techniques. These results lead to UE's (User Equipments) battery's savings as well as interference level's reduction.…”