Measurement Journal Issue 6

It’s also worth noting that in a mobile environment, extreme changes of bandwidth are likely and often occur rapidly as a mobile device roams between networks. These large, dynamic variations are difﬁcult to model and even more challenging to compensate. Similarly, as a mobile phone moves between networks, large delays can build up as a result of the time required to process handover protocols and re-establish data ﬂow. Test techniques that mimic real-world scenarios are therefore the best way to ensure that the phone continues to perform correctly in a challenging environment. The next step is to add an application that places a moderate load on the device’s processors. Then, to fully stress the system from a data throughput perspective, a packet-switched call can be set up and a data ﬁle transferred. Using FTP, for example, can simulate the running of an application that requires acknowledgment of received packets. Following these steps maximizes the amount of data ﬂowing through the HSPA mobile phone to verify that everything is working together. Two additional techniques can be used to push the mobile phone to its performance limit: • Emulating a live network and exposing the phone to scenarios that could be expected in the real world. • Subjecting the phone to the most stressful of these usage scenarios to ﬁnd any weak (or breaking) points in the design. Finally, the importance of handover testing must be noted. Handover errors are some of the most common causes of dropped calls and data loss. Valuable network resources are required to manage handovers and this explains why so many HSPA conformance tests require testing with more than one cell. It is critical to test handovers while running other services and features on the phone such as SMS, MMS, FTP throughput, Web browsing, and video and voice calls. Additionally, it’s important to test scenarios in which the phone hands over from a cell that supports HSPA to one that does not. Base station emulators that support HSPA can be used for testing most of these cases. Improving test effectiveness There is no simple, one-step method of testing mobile phones for every performance issue associated with HSPA. However, a useful approach can be devised to test mobile phones during the integration and validation stages of development. Testing at the physical layer is the ﬁrst step in evaluating the performance of a mobile device or application. Physical-layer data throughput gives an initial indication of how well the mobile phone is performing, although it doesn’t point directly to the root cause of any errors that may occur. Building on the results of physical layer testing, the next step is to validate the radio link control (RLC) protocol, driver and IP. This begins to tell the developer how the HSPA device will perform on a live network. Application-layer data throughput tests can also be carried out at this time to see how well the mobile phone performs from an end user’s perspective. Resolving HSPA issues Mobile phone designers can identify and resolve many HSPA issues using the test methodology described, along with enhanced measurement tools provided by test and measurement suppliers. As an example, consider a situation uncovered during physical layer testing (Figure 3). In this case, the designer wanted the device to process HSDPA and HSUPA data simultaneously at the maximum capability of the device — 7.2 Mbps on the downlink and 2 Mbps on the uplink. Although the downlink data appeared to work correctly, the uplink data was occasionally being dropped. Setting up a packet-switched data call, the designer initiated a flood of user datagram protocol (UDP) trafﬁc to and from the device and observed the results on the data throughput monitor provided by the Agilent 8960 Wireless Communications Test Set. 29 Agilent Measurement Journal

Table of Contents Feed for the Digital Edition of Measurement Journal Issue 6

Measurement Journal Issue 6 Using a Few Words to Convey a Deeply-Held Spirit Charting a Unique Path to Technology Innovation Contents Announcing First Commercial GC/MS Metabolites Library Assessing Nonlinear Behavior Testing Combines Form and Function Testing Multiplay Networks Higher Sensitivity LC/MS Easing Military Radio Test Stepping Up Calibration Accuracy Increasing Spectrum Analyzer Bandwidth 3GPP Tool Supports TS 36 Standards The Olympic Story Spotlights Agilent's Continuing Contribution to Technology Innovation Ensuring a Level Playing Field in Competitive Sports GPS: Coming of Age Resolving Design Issues in HSPA Mobile Devices Achieving Accurate Results with Oscilloscope-Based Jitter-Analysis Software RF Handheld Testers Guarantee Traffic Stability Under Olympic-Sized Stress Conditions Utilizing LAN-Based Instrumentation to Measure Total Harmonic Distortion in Remote Facilities IMT-Advanced: 4G Wireless Takes Shape in an Olympic Year EPO Doping: A Speed Engine, Turbo-Charged by Chemistry

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.