Question: What is more important for MNO capacity and optimization? The 3GPP physical layer Spectral Efficiency or the Bearer Efficiency?
To answer the question we need to understand what is what…
- Spectral efficiency (SE) is a measure of information rate, transmitted over a given bandwidth, measured in Bits/sec/Hz
- Bearer efficiency (BE) is the measure of the effective number of user payload bits, carried by the transmission of one symbol and measured in bits/symbol. There is no bandwidth mention at all!!!
Did you know that 3GPP TS 38.214 Spectral Efficiency column in Table 5.1.3.1-1, actually refers to the Bearer efficiency??? Indeed following the row for MCS 25, that translates into bearer efficiency = (Modulation order) x (Target Code Rate) = 6 x (822/1024) = 4.8164 without mentioning bandwidth
well…to convert from that point to real 5G NR resource grid spectral efficiency, for a given SCS, we need to use the convertion formula:
BE (bits/symbol) = SE x SCS bandwidth (Hz) / (symbols/slot) x (slots/sec) = (SE x 120000) (bits/sec) / (14 x 8000) (symbols/sec) = SE x 15/14 (bits/symbol)
Or
SE = BE x (14/15)
Summarizing:
Spectral Efficiency (SE): Directly impacts network capacity and how efficiently expensive licensed spectrum is used. For operators, spectrum is the most valuable and costly resource, so maximizing SE is key to delivering more Gbps/Hz/site.
Bearer Efficiency (BE): Matters more to equipment vendors and PHY designers for scheduler and Link Adaptation, since it reflects coding/modulation efficiency without spectrum context. It’s a clean metric for comparing MCS tables and coding schemes, but it doesn’t capture full system efficiency.
Conclusion: For MNOs, SE is more important than BE since spectrum cost is the bottleneck resource, not the symbol structure.
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