Test & Measurement World, July/August 2012

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TESTDIGEST All of this is spurred by a basic problem: Despite all the technology, location accuracy is often just not good enough when calls are placed from mobile phones; in some cases, us- able location information is impossible to obtain, especially when calls are made from indoors. Today, more than 70% of 911 calls originate from mobile devices, and more than 60% of 911 calls originate indoors. Industry bodies such as 3GPP and 3GPP2 have developed compliance standards for mobile devices to help ensure the FCC's location accuracy requirements are achieved. Since these standards are global, they are often a requirement in other markets as well. For 2G and 3G devices that use CDMA, GSM, or WCDMA technology, the requirements are well established. The recent push to launch LTE, or 4G, networks, however, is shaking things up. With LTE migration well underway in North America, wireless service providers are working to upgrade the tech- nologies that enable caller-location identification in order to PRODUCT TRYOUT iOS logic analyzer shows the bits Oscium, the company that developed the iOS-based iMSO-104 oscilloscope and WiPry WiFi spectrum analyzer/ power meter, has now developed the LogiScope, a 16-channel logic analyzer for the iPad, iPhone, and iPod Touch. I tried the $389 LogiScope on an iPad 2 rather than on an iPhone because of the iPad's larger screen. Viewing 16 traces on the iPhone's screen is, well, challenging. As the figure shows, the LogiScope comes with two wiring harnesses, each holding eight color-coded input wires and a ground wire. The leads connect to standard-sized pins. The instrument also comes with a bag of 16 clip leads. I used 16 channels of a 24-channel logic demo board as a signal source. After downloading the free app from Apple's App Store, I connected the Lo- giScope. The iPad immediately found the instrument and signals appeared. Navigating the menus is easy and is similar to the way you navigate the menus on Oscium's other products. Each trace on the screen is color-coded to match the color of the wire. Using your finger, you can move any trace up or down the display. The "Digital" menu lets you turn deploy E911 capabilities. Designers need to understand how the different positioning technologies (or combinations of technologies) play into the requirement to support E911 on LTE networks in North America and must also understand the implications for testing the complex positioning scenarios that can result. No current positioning technology is capable of providing the FCC's required accuracy level by itself, so a combination of technologies will likely be needed. Current LTE standards support three handset-based positioning technologies: ECID, A-GNSS, and Downlink OTDOA. LTE deployments also employ two location protocols: LTE Positioning Protocol and Secure User Plane Location Version 2.0. In the online version of this article, we discuss the FCC's standards and how they translate into location protocols, and we also explain how engineers can test E911 in LTE net- works: Brock Butler and Susan Ahimovic, Spirent on any channel and give each a name. The "Cursor" menu lets you enable cursors for measuring time between events or the frequency of a signal. Us- ing the "Measure" menu, you can measure duty cycle, pulse width, and frequency. The LogiScope also provides a two- level trigger. Virtual logic gates add combinational logic for building a trig- ger. The virtual gates let you set up AND, NAND, OR, NOR, XOR, or XNOR conditions to trigger an acqui- sition. Trigger conditions include rising or falling edges, levels, or pulse width. Overall, the LogiScope is a handy tool for troubleshooting logic circuits. To read my complete product tryout of the Lo- giScope, go to the online version of this article at To read my tryout of the earlier-released WiPry spectrum analyzer, go to "Prod- uct tryout: iOS spectrum analyzer/ power meter lights up WiFi" at www. Martin Rowe, Senior Technical Editor Test & Measurement World | JULY/AUGUST 2012 | –15– ^

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