Location technology has become an integral part of modern life, with wireless chipsets supporting positioning capabilities such as Global Navigation Satellite System (GNSS) and Assisted GNSS (A-GNSS) now included in many handheld devices. A-GNSS is just one location technology—in addition to the use of cellular systems, Wi-Fi, and sensors—used to provide location information. Many location-finding devices combine data from several different positioning technologies for improved accuracy, especially where the signals from one technology might be weak or not available (such as when indoors or in congested urban areas).
With the combination and integration of multiple location technologies into portable devices, of course, comes a significant and complex challenge to validate the hybrid performance of the devices. Fortunately, the Hybrid Location Technology Solution (HLTS) from Spirent Communications can be tailored to characterize different hybrid scenarios and RF emulation, based on a combination of location technologies [including cellular, Wi-Fi wireless-local-area-network (WLAN) systems, A-GNSS, and sensors].
HLTS can create actual operating conditions, such as uplink and downlink signal loss and free-space path loss (in IEEE 802.11 systems). This enables testing devices with location capabilities in the laboratory under controlled, repeatable conditions, reducing the time needed for field testing. HLTS also validates hybrid or multiple-location-system operation, such as the combination of A-GNSS and Wi-Fi positioning methods.
One component of HLTS, the GSS6700 GNSS simulation system, can simulate as many as 12 simultaneous channels for each satellite constellation, such as GPS, GLOSNASS, or Galileo satellite channels, including multipath and atmospheric effects. HLTS includes the GSS6700 hardware instrument for signal generation and analysis and the SimSENSOR software for programming and control.
For Wi-Fi or WLAN simulations per IEEE 802.11 a/b/n standards, HLTS uses the GSS5700 simulation system to produce the required simulation signals at 2.4 GHz. It can produce from 1 to 14 operating channels and 12 independent access points (APs) in a simulated Wi-Fi/WLAN system.
HLTS employs the SimHybrid™ software and a graphical user interface (GUI) to synchronize simulation or playback of A-GNSS, WiFi, sensor, and cellular positioning technologies. SimHybrid enables interactive testing by allowing complete flexibility to model real-world scenarios with the inclusion of advanced parameters for motion, RF emulation, antenna characteristics, atmospheric effects, path loss values, and multipath propagation parameters (see figure).
The HLTS test system works with the SimHybrid GUI to synchronize simulation or playback of A-GNSS, Wi-Fi, sensor, and cellular positioning technologies.
HLTS provides two operating modes: simulation, and record and playback. In simulation mode, the HLTS GUI, SimHybrid, allows a user to create a scenario from scratch, providing complete control over all aspects of the environment. Simulation mode provides the ability to model the real world and characterize certain aspects of a device performance under a particular set of conditions—including stress testing under difficult conditions and replicating different environments without going into the field.
The main goal of the record and playback mode is to bring the field conditions into the lab. Playback mode utilizes recording devices to capture the field data, and then replay the field data using laboratory instruments. Data from different location technologies can be collected simultaneously on the same time scale and replayed coherently.
HLTS employs two approaches for collecting and replaying field data. In the first, working with processed information from high-performance receivers, Wi-Fi, GPS, and cellular signals can be decoded and the key elements required for positioning recorded synchronously. These signal elements can then be fed to simulators that generate the required RF signals to exercise a device under test to varying field conditions. In the second approach, using recorded RF captured by specialized receivers (such as the Spirent GSS6400), the actual field RF can be recorded over a set spectrum. The device can then be used to playback the recorded signals.
Spirent’s HLTS is an industry leading test solution that integrates four different location technologies into one system, boasting software that simulates and controls the actual environments of location-finding satellites, APs, cellular towers, and sensors. Providing several advantages over field testing, HLTS allows for repeatable conditions, isolation of specific conditions and regression/stress testing. Spirent’s HLTS enables the R&D engineer to address complex hybrid location technology test scenarios in the lab, a critical step in the successful deployment of the next-generation, location-enabled mobile device.
Spirent Communications, 26750 Agoura Rd., Calabasas, CA 91302;(800) SPIRENT, (818) 676-2683, e-mail: sales@spirent.com, www.spirent.com.