There are no modifications at the tower. Usually your phone drops B41 at around -120 because the upload times out, even though the download may still be chugging along at 10-15 mbps. All HPUE does is increase the maximum upload power of the phone, allowing it to hold on to a much weaker signal without the upload failing. This perceived increase in range, because the phone will not drop B41 until a much weaker signal , brings its "range" almost to that of B25.