For the last couple of decades, reverberation technology was solely used as a tool for engineers specializing in electromagnetic compliance (EMC) testing. Bluetest innovations have transformed this technology into a powerful solution tuned to the needs of current wireless developers. They are the next generation of over-the-air (OTA) test systems that bridge the testing gap between conducted and drive test methods.
It's All About User Experience
Among all the intangibles that wireless advertising serves, the real promise of wireless is about delivering high-quality communications at unprecedented data speeds on attractive devices. Great wireless designs, when working with solid networks, deliver on that promise. Today, devices and networks are supposed to interact dynamically to maximize scarce communications bandwidth in complex wireless environments. But do they? And if so, how well are they performing?
Traditionally there have been two basic test processes for verifying a device's wireless performance. The first is the conducted test, which taps into the handset's circuitry to measure subsystem performance, and the second is the drive test, which takes the device through a known network route and gathers performance data as it moves.
These two test methods provide very different kinds of insights. Conductive testing allows for a very deductive analysis of the phone's design and lends itself to an isolation-of-variables approach to tracking down how different parts of the phone respond to different signals. Drive testing, can be described as a more inductive process and lends itself to gathering large amounts of data to help infer and predict real-world performance.
Enter Over the Air Testing
As wireless phone designs advanced, more radio capabilities were added to more compact form factors. Phones that once ran a single technology in a region-specific band now became multi-mode, multi-band integrated systems. Connectivity expanded beyond the core cellular radio to include Bluetooth, WLAN and GPS. Antennas became integrated into the boards and cases of the device.
This increase in system complexity and tighter integration meant that diagnostic testing on the entire phone system became necessary. Component and subsystem testing no longer covered all the issues that the integrated system had to deal with.
Over the Air (OTA) testing allows for complete system testing of the wireless device in a controlled lab environment. Freed from the literal tethers of conductive testing, designers could now see the total system performance - including its interaction with the user's grip and positioning.
OTA doesn't replace drive testing, or conductive testing. Instead it bridges the gap between the two. It provides a way to analyze the total phone performance, including the subtle and complex effects of the radiating components across all the modes and bands and formats now supported.
The reverberation chamber systems from Bluetest are today one of the most convenient and accurate solutions available for OTA testing of wireless devices. They have become a significant part of the design and verification processes of engineers all over the world.
Reference Environment System Testing
As 3G matured and 4G emerged, capacity demands drove the implementation of multiple-input multiple-output (MIMO) technology to increase throughput under multipath conditions. When a handset no longer has direct line-of-sight to the base station antennas, it typically receives the signal from reflections of multiple objects. It reality, there are many reflection sources - especially near or inside buildings. (Cell phones shifted to being used more indoors than outdoors much sooner than many people think). This is known as a rich multi-path environment and together with multiple antennas on transmitters and receivers it can be used to send several data streams at the same frequency at the same time.
As MIMO became an important function for wireless designers, Limited MIMO testing was added to conducted and drive test systems. Creating multipath in many OTA solutions, however, was not possible as they were designed around a focused line-of-sight methodology.
Since Bluetest reverberation chambers are inherently multipath systems, MIMO testing of wireless devices was a direct extension of the antenna measurements we were already doing. Bluetest system users were able to test the MIMO performance of their devices in existing OTA chambers very rapidly. And as the industry began to explore the characteristics of wireless multipath channel environments, we have found ways to tune, modify and verify the wireless environment in the chamber.
This ability to test in a repeatable, yet complex channel environment is the latest in wireless system testing. This next generation of OTA testing verifies the total device performance under pre-defined channel characteristics. Unlike drive testing, which also has complex channel characteristics, we are testing under a controlled reference environment. This allows designers to easily see variations due to design changes, or network engineers to easily rank phone performance.
The Next Generation Bridge
Reference Environment System Testing is the latest generation of test solutions to bridge the gap between the core conducted and drive test methodologies. This is particularly critical today as use models and form factors explode. Wearables, tablets, connected vending machines, cars and trucks - everything is incorporating wireless data capabilities running on the latest cellular networks. The Bluetest systems, building on the convenient reverberation chamber technology, are a powerful tool for engineers to verify the performance of the latest wireless devices.