Microwave Engineering Europe - October 2008 - (Page 28)

28 MOBILE PHONE TEST Simplify mobile data applications and services test By Sara Johnson, Product Marketing Engineer, Agilent Technologies, Inc. W hat happens when mobile devices pass signaling conformance tests, but still have performance that results in degradation of service? Here are just a few real examples of performance issues found after passing conformance tests: • A data security application in the phone would utilize 100 percent of the CPU until an email was sent to the phone; • Phone was too slow in responding to channel changes during video streaming; • A large number of SMS messages would cause the phone to quit working. Finding these types of problems during development is difﬁcult. Users typically keep their devices on for several days, and conformance tests do not address any latency driven issues. Finding a way to easily demonstrate and replicate the problem so that the program ﬂow in the phone can be traced and a ﬁnal solution implemented is not trivial. One class of failure that will never be detected without extensive repetitive test is a memory leak. When a new process is initiated in a computer system, it requests a memory block from the operating system (OS). When the process completes, it should release that block of memory back to the OS. A leak occurs when the amount of memory returned to the OS is smaller than was originally granted. If this process is executed repeatedly, the available memory will become depleted and cause the computer to stop functioning as it runs out of memory. Often, it is the interaction of numerous processes that will trigger a leak. As simple as it seems to correct such an error, it can be very difﬁcult to determine that it has happened. Each service initiated in the user equipment (UE) will launch at least one process, usually many more than one. It is important to use a variety of tasks with lots of repetition to excite possible memory leaks. Poor service performance as well as a shorter battery life is caused by faulty interactions of applications. Figure 1: Agilent 8960 data throughput results of a ﬁle download while incrementing the CQI value. The qualiﬁcation process for a modern cellular phone is very complex. Signaling conformance testing was originally meant to guarantee interoperability between network equipment from various providers and the user equipment from various vendors. For GSM this model works well as the main focus of this system is on control elements for voice, and the signaling associated with a voice call is relatively simple. The added complexity for SMS using the GSM control channels is also low and can be considered as a specialized class of signaling on the control channels. With the rollout of data services in cdma2000, 1xEV-DO, GPRS, EGPRS and the improvements to data services in W-CDMA and its high speed data capabilities in HSPA, script based testing veriﬁes speciﬁc call processing scenarios in extremely limited cases. While serving an important role, this qualiﬁcation is not sufﬁcient to fully qualify a modern UE. Additionally, ﬁnding problems in UE qualiﬁcation during phone qualiﬁcation at an operator’s test site is very costly, both in engineering time, and in delays in getting a product to market. What is needed is a test environment in the R&D lab that emulates the real-world and extreme usage models. Real-world testing (overlapping various services just as an end-user would) undertaken in the lab requires a functional test system that forces the device to process a host of interacting test scenarios. This is as opposed to scriptbased testing methods, since with script testing the phone’s connection state is often established artiﬁcially using a test mode, and the complexity of the script is generally small when compared to the real world operating environment. A real-world test approach requires the UE to use the protocol stack to establish a circuit switched or packet switched connection to the system, establish services, and allow various services in the UE to run in parallel — just as can be done when using the device in a real network. Examples of these services include voice calls, SMS, MMS, data transfer using WAP, HTTP, UDP, or FTP protocols, cell handovers, and changes in data rate and coding structure. Also it is important to stress the link with dropped frames or blocks to test the retransmissions and data storage that occurs as packets arrive out of sequence. Inter-mixing these various services during testing before devices Microwave Engineering Europe ● October 2008 ● www.mwee.com 028_030_MWEE.indd 28 2/10/08 12:48:22 http://www.mwee.com

Table of Contents Feed for the Digital Edition of Microwave Engineering Europe - October 2008

Microwave Engineering Europe - October 2008 Contents Comment News Cover Feature: AWR's AXIEM Software Brings 3D Planar Electromagnetic (EM) Simulation "Up Front" RFID: Augmented Reality: Beyond RFID and QR Codes for Mobile Phone Platforms Filters & Frequency Synthesis ZigBee Goes Green with Support for Smart Energy Simplify Mobile Data Applications and Services Test Enabling the State-of-the-Art in Automatic Test Equipment National Physical Laboratory Test Facility Aids Development of Next-Generation Antennas Selecting the Synthetic Test Environment for Transmit-Receive (T-R) Modules in a Phased Array Radar System Products Calendar

Microwave Engineering Europe - October 2008

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