HD-FDD LTE-M and HD-FDD LTE-NB have different uplink ratios over radio frame and maximum continuous uplink durations. Both systems are based on a 10 ms radio frame consisting of 10 subframes (SF), 1 ms each.
In normal network signaling conditions without uplink repetitions, the number of continuous uplink and downlink subframes may differ noticeably between the systems. In HD-FDD LTE-M, the maximum uplink ratio can be 3 SF/10 SF (33%), whereas in HD-FDD LTE-NB it can be 8 SF/10 SF (80%). This means that in HD-FDD LTE-NB, the uplink can be transmitting approximately three times longer per radio frame than in HD-FDD LTE-M.
However, with uplink repetitions, both systems share the same uplink ratio of 86%. Power consumption at high output power levels for HD-FDD LTE-M is approximately 15% higher than HD-FF LTE-NB. Power supply design requirements are the most rigid for LTE-M.