There are always some test results one cannot readily explain. In principle, spectral efficiency should be higher when channels are bigger, at least in part because less bandwidth is “wasted” on guard bands. That does not appear to be the case for a test of 2.6-GHz 5G spectrum on Sprint’s network in Chicago, which found 2.6-GHz spectral efficiency greater than on millimeter wave spectrum.
“Based on RB-normalized throughput and MCS allocations, the Band 41 spectral efficiency was at least 50% higher than 5G millimeter wave for most test scenarios in Chicago when compared with testing did in New York City late this summer,” according to a study of Sprint’s network.
But there are notable elements of the test that likely account for the finding that 2.6-GHz efficiency was higher than that of millimeter wave networks. The Chicago test used some form of spectrum aggregation, where both the 2.6-GHz 5G channels and also 4G LTE bandwidth could be used by the phones tested.
In principle, that means the effective 5G bandwidth theoretically could use 120 MHz of spectrum across the 4G and 5G networks. It seems likely that the millimeter tests used channels of less than 120 MHz.
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