Microsoft's Lumia 640 may not be the most powerful or feature-packed smartphone, but a study has found it's the best performer under a weak network signal.
The study, conducted by Aalborgs University in Denmark and commissioned by telecom authorities in Sweden, Denmark, Finland and Norway, assesses how good 26 smartphone models are at providing a connection when operated on weak mobile signals.
Samsung's Galaxy S7 and S7 Edge were put under the microscope alongside Apple's iPhone 6S, iPhone 6S Plus, and iPhone SE, Google's Nexus 6P and Nexus 5X, as well as Microsoft's Lumia 950, Lumia 650, and Lumia 640.
Surprisingly, when it comes to data services on a weak signal, Microsoft's Lumia 640 tops the field under the LTE 800MHz band. It also achieves respectable results in the LTE 1,800MHz and LTE 2,600MHz bands. In second, third and fourth place are Samsung's Galaxy S6 Edge+, Galaxy S7 Edge, and Galaxy S7.
None of Apple's iPhone models fare well in the study. In the 800MHz band, Apple's iPhone SE is the best performer but ranks 11th, behind the Lumia 950, Huawei P9, and Nexus 5X. The iPhone 6 and iPhone 6S trail at 13th and 14th place respectively, ahead of iPhone 6S Plus in 17th spot.
The study also looks at each model's voice performance when held in either the right or left hand, and hands-free mode. HTC's Desire 626 tops the right-hand test, while the DORO PhoneEasy 530X comes in top for the left-hand test. The top iPhone in the right-hand test is the 6S Plus, which ranks 12th, while all four iPhone models occupy the bottom four spots in left-hand tests.
Unfortunately for iPhone S6 Plus owners, their device is also the worst performer in a test that measures devices in action without the interference created by a head or hands in the low frequency GSM900 band.
The study questions how far manufacturers are taking into consideration how people hold phones when designing antennas.
"The performance variation between left-hand and right-hand usage is for several phones very large," it notes. "This shows that for some phones the antenna design does not take body loss in different usage positions into account. A well-designed antenna solution has a low body loss in both right- and left-hand usages."
To indicate each device's data performance, the study measured the Total Isotropic Sensitivity (TIS) attained in each frequency band. The TIS is a negative number measured in decibel-milliwatts or dBm. So Microsoft's -93.1dBm indicates it was better at receiving data in weak signal areas than the Galaxy S7 Edge's -92.2dBm or the iPhone 6's -89.1dBm.
Small variations in the dBm measurement can result in a big difference between data speeds. As an example, the study points out that "with low signal strength, a 7dB reduction in TIS results in a reduction in the data-rate from, eg, 1Mbps to 0.2 Mbps".
In other words, the poor-performing phone will take five times longer to download from the network than a good-performing phone. Also, 1Mbps suffices for most data services whereas 0.2Mbps does not.
Sweden's telecoms authority PTS concludes from the study that phones work best in hands-free mode and worse when held to the head.