Journal of Information Engineering and Applications www.iiste.org ISSN 2224-5782 (print) ISSN 2225-0506 (online) Vol.3, No.11, 2013 44 VoIP on 3GPP LTE Network: A Survey Oluwadamilola I. Adu, Babasanjo O. Oshin and Adeyemi A. Alatishe Department of Electrical and Information Engineering, Covenant University Km 10, Idiroko Road, Ota, Ogun State, Nigeria E-mail: damilola.adu@covenantuniversity.edu.ng Abstract As wireless access networks evolve towards an all-IP architecture, the principles of operations of communication services (specifically voice services), which have hitherto been circuit switched are being revisited. Voice over Internet Protocol (VoIP) has been identified as a solution and is potentially capable of completely replacing existing phone networks. However, as opposed to circuit switching technology, the call quality obtained via packet switching through IP has not been encouraging due to certain issues. The increasing demands on data rates, mobility, coverage and better service quality, led to the evolution in Radio Access Technologies (RATs) to an era of last-mile fourth generation (4G) access technologies among which is Long Term Evolution (LTE). LTE is an all-IP network initially meant for carrying data only, while carriers would be able to support voice traffic either by utilizing 2G or 3G systems or by using VoIP. This paper seeks to describe all options for providing VoIP services as a method of voice transfer over the LTE network. Keywords: 4G, Circuit switching, Convergence, LTE, Packet switching, RAT, VoIP. 1. Introduction The Internet Protocol (IP) is the driving force for future communication networks with convergence being an important requirement. Voice over IP (VoIP) can be said to have contributed somewhat to this convergence such that multiple networks including data, voice and video, are being integrated into a single network to share common facilities resulting in efficiency and cost savings; therefore, it has the potential to completely replace existing phone networks. However, as opposed to voice service through circuit switching technology, the quality of calls transmitted via packets through internet protocols was still not very encouraging; therefore, its use by operators and consumers was still limited. This was majorly due to the fact that voice transmission demands high-speed data rates for effective and efficient communication, which was a scarce and expensive commodity. To enhance the user Quality-of-Experience (QoE), necessary Quality-of Service (QoS) measures were developed and implemented. The QoS measures addressed issues peculiar to packet networks such as but not limited to packet loss, latency, jitter and echoes in the network. These issues brought about the necessity for multiple networks: circuit switching network for voice and packet switching network for data. This led to high CapEx (Capital Expenditure) and OpEx (Operating Expenditure), in that, the separate networks needed separate infrastructure and running expenses. The increasing demands on data rates, mobility, coverage and better service quality, led to the evolution in RATs and the corresponding Radio Access Networks (RANs) from the eras of second generation (2G) systems (a mixture of circuit switching and packet switching functionalities) through till the advent of last mile fourth generation (4G) access networks which are entirely packet-switched. These 4G RATs, which are entirely packet- based, are foreseen to either complement or replace existing standards because the required future RAN architectures must support an increased volume of packet-based applications, ensure availability of efficient IP packet transport, and provide mobility within and between the access networks (Didier, 2007; Jordi, 2007; 3GPP2, 2006). The introduction of a Next Generation Mobile Broadband Network (NGMBN) called Long Term Evolution (LTE) falls into this 4G all-IP category. LTE, developed by 3GPP (ETSI TS, 2011), builds on the UMTS cellular technology to meet operator requirements for high-speed data and other multimedia transport as well as high- capacity voice support for future generations. It possesses the strength and capabilities to support real-time applications excellently well (like in voice transfer using VoIP). LTE at the onset, was understood to be a completely IP cellular system meant for carrying data only, while carriers would be able to support voice traffic and SMS either by utilizing 2G or 3G systems or by using VoIP. Consequently, a number of alliances were set up to develop approaches in ensuring the possibility of carrying voice over the LTE network (Ian, 2012). This paper seeks to describe all options for supporting VoIP services as a method of voice traffic over the LTE network and it is organized as follows: Section II describes briefly the principle of operation of VoIP. Section III describes the components and functionalities in an LTE network. Section IV explores the various options for VoIP services over an LTE