FEATURE TEST & MEASUREMENT Enhancing the quality of experience with MIMO
Richard Jacklin, Business Development Director at network and handset interoperability testing specialist, Anite discusses the factors which will determine 5G device performance and the importance of thorough testing for the range of applications for the new standard
be performed using one of two methods: • Evaluating and benchmarking performance of 2x2 and higher order MIMO devices
he mobile phone industry is being driven by a need for increasing capacity and speed for end-users to access applications such as video, web browsing and audio streaming. This growth is facilitated by 4G, or in other words, LTE and LTE-A technologies. According to Cisco1
T , 4G represents only 6 percent of mobile
connections today, but already accounts for 40 percent of mobile data traffic. With average smartphone usage up 45 percent in 2014 and mobile video traffic accounting for more than half of total mobile data traffic, making sure mobile devices deliver on Quality of Experience (“QoE”) is crucial if operators are to meet their customers’ expectations. Authorised/Licensed Shared Access (“ASA/LSA”) allows operators to unlock additional and under-utilised spectrum, leading to improved data capacity. ASA/LSA enables them to share spectrum with existing non- mobile incumbent users with low or localised utilisation in their bands. Key LTE-A features such as Carrier Aggregation (“CA”), eICIC (enhanced Inter Cell Interference Coordination, CoMP (“Coordinated MultiPoint” and MIMO (“Multiple Input Multiple Output”) also contribute to improving data capacity.
VERIFYING PERFORMANCE WITH LAB-BASED TESTING There are essentially two lab- based methods that device manufacturers and operators use to test the performance of an LTE-A capable mobile device. The first uses a standardised model and is predominately used in the R&D stages of mobile device development and by operators who wish to validate and
20 SEPTEMBER 2015 | ELECTRONICS
1 Cisco Visual Networking Index (VNI) Global Mobile Data Traffic Forecast Update 2014-2019 White Paper (published February 3, 2015)
2 CTIA-The Wireless Association is an international non-profit membership organisation that has represented the wireless communications industry since 1984
benchmark devices. MIMO Over-The-Air (“OTA”) testing is an example of a test method that applies a standardised model. The second uses measured propagation
models such as in Virtual Drive Testing (“VDT”) where a “standard” propagation model is replaced by a field measured model. This gives greater ability to benchmark devices within an operator’s network, using typical drive test routes. This method is also used by device manufacturers and operators as well as by Network Equipment Manufacturers who wish to verify the performance of their product against various types of devices. VDT uses data imported from real networks to enable users to cost-effectively perform realistic drive testing in a repeatable way.
ACCELERATING THE DEPLOYMENT OF LTE-A MOBILE DEVICES CTIA2
has represented the wireless “OTA testing in a
reverberation chamber with Anite’s Propsim
channel emulator enables assessment of a device’s average data throughput performance ... ”
communications industry since 1984. Operators and manufacturers of devices and network infrastructure use their recommendations as part of their development and evaluation programmes. Anite has contributed channel emulation expertise to the CTIA MIMO OTA sub- group which has been investigating MIMO OTA performance since its
inception in March 2011. The sub-group has recently agreed
(with endorsement from all CTIA operators) that testing of devices with multiple antennas against
standardised propagation conditions should
• Evaluating and benchmarking performance of devices using Transmit-Diversity mode (“TXD”), which involves evaluating the performance of both receive (main and diversity) antennas in a mobile device MIMO OTA testing using channel emulators in an anechoic chamber CTIA recommends evaluating and benchmarking the performance of 2x2 and higher order MIMO devices by performing MIMO OTA testing in an anechoic chamber in combination with channel emulators. In an anechoic chamber, multiple antennas are deployed at various angles to simulate reflections. A large capacity channel emulator enables the user to perform a wide range of testing, from small to large devices. Furthermore, a channel emulator with channel capacity for as many as 32 channels enable Carrier Aggregation based testing under a single setup, which simplifies testing, reduces test times and increases reliability. CTIA recommends performing Transmit-
Diversity testing in an anechoic or a reverberation type chamber. A reverberation chamber is a highly reflective environment where multipath signals fill the chamber with standing waves. Channel emulators enhance the capabilities of a reverberation chamber by implementing different power delay profiles, adjusting delay spreads and enhanced Doppler speeds, as well as by taking into account different base station antenna configurations; thereby offering better control over the temporal properties of the channel. OTA testing in a reverberation chamber
with Anite’s Propsim channel emulator enables assessment of a device’s average data throughput performance relative to other devices under isotropic Spatial Channel Model extension (SCME) channel models. MIMO OTA testing incorporates the antenna performance by letting a device interact with a spatial channel. It helps operators and device manufacturers assure end-user quality of experience of LTE-A MIMO capable mobile devices. Anite offers a future-proof channel emulator with superior channel emulation capabilities in terms of capacity and emulation accuracy for MIMO OTA in anechoic or reverberation type chambers.
Anite
www.anite.com 01252 775200
/ ELECTRONICS
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