Instead of simply adopting Long Term Evolution’s (LTE’s) Internet Protocol (IP) -based core infrastructure to totally replace their second- and third-generation (2G and 3G) networks, mobile operators are migrating gradually. Until Voice over LTE (VoLTE) is widely available, a solution must therefore enable LTE to work with existing 2G/3G voice services. Depending on their legacy network environment, operators can leverage options like Circuit Switched Fall Back (CSFB), Simultaneous Voice and LTE Data (SVLTE), and Single Radio Voice Call Continuity (SRVCC). This Band-Aid approach will present many challenges for developers, who must now create a range of different and more complex LTE user equipment (UE). In a five-page application note, Agilent Technologies stresses that the accurate and efficient voice testing of LTE UE will be needed to ensure that VoLTE delivers the same standard of voice calls provided by 2G/3G.

Titled “Enabling Fast, Accurate, and Efficient Testing of Voice Quality in LTE User Equipment,” the application note explains that test requirements for such devices are numerous—whether they are being tested by Perceived Evaluation of Speech Quality (PESQ) or a Perceptual Objective Listening Quality Assessment (POLQA). Testing can be performed using the following: audio analysis; signaling test (including connections to servers, conformance testing, radio aspects, and handovers for fallback support); battery-drain analysis; and SMS/video-call testing. In addition, operator-specific test plans and field testing also may be required.

Depending on the type of test, the form of UE testing also varies. Designers, for example, will perform benchtop testing. Yet the operator will demand infrastructure interoperability testing (IOT) with a variety of UEs, network equipment, and client applications. Conformance testing for standards also will be required. At some point, a combination of all of these tests will be needed.

To satisfy these varied requests, the application note suggests the use of a building-block approach. By combining a variety of products in different configurations, it is possible to address a range of LTE UE tests and test needs. In addition, UE developers can gain greater insight into their designs.

VoLTE battery-drain analysis, for example, calls for the creation of new battery-drain profiles. For a 2G/3G UE, battery-drain testing usually involves the transmission and reception of files, multimedia messaging services (MMSs), the repeated sending of short messaging services (SMSs), and potentially a combination of all of these tasks. Yet VoLTE has to confront its own burst-transmission nature as well as the all-IP network and different discontinuous reception (DRX) patterns for both idle (paging cycle) and connection mode. Using Agilent’s IFT software and PXT test set, it is possible for a developer to set up loops that continuously repeat SMS/MMS sends, large file downloads, voice calls, and more to simulate likely battery-drain profiles.

Agilent Technologies, Inc., 5301 Stevens Creek Blvd., Santa Clara, CA 95051; (877) 424-4536, www.agilent.com.