UE (Global Telecom Titan 4000 CPE, FWA) reports split UE categories per 3GPP Release 12 in UECapabilityInformation:
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ue-Category = 7 (legacy, max UL TBS 102,048 bits/TTI)
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ue-CategoryUL-r12 = 13 (R12 split, max UL TBS 150,752 bits/TTI)
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ul-64QAM-r12 = supported (in rf-Parameters-v1250, Band 48)
The eNB correctly grants 64QAM modulation on PUSCH based on ul-64QAM-r12 (confirmed via M8012C257/C258 counters showing MCS23/MCS24 64QAM traffic for non-256QAM UE). However, the PUSCH scheduler appears to use the legacy ue-Category=7
TBS limit (102,048 bits) rather than ue-CategoryUL-r12=13 TBS limit (150,752 bits) for transport block size selection.
Observed behavior: UL throughput caps at approximately 21 Mbps on a 10 MHz TDD carrier (SA2), which matches Cat 7 TBS calculation: 102,048 × 2 UL subframes / 10ms = 20,410 kbps.
Expected behavior: UL throughput should reach approximately 30 Mbps per 3GPP TS 36.306 Table 4.1A-1, using ue-CategoryUL-r12=13 TBS limit: 150,752 × 2 / 10ms = 30,150 kbps.
Evidence:
1. S1-AP UE Capability Info Transfer (pcap) confirms UE sends both ue-Category=7 and ue-CategoryUL-r12=13
2. M8012C257/C258 counters confirm 64QAM is scheduled on PUSCH (MCS23/24), proving eNB reads ul-64QAM-r12 from rf-Parameters-v1250
3. UL throughput consistently caps at ~21 Mbps regardless of RF conditions
4. LTE44 (64QAM UL) is active and functioning correctly
5. LTE4581 (256QAM UL) documentation confirms eNB can parse ue-CategoryUL-r12 for Cat 16-20, but no feature identified for Cat 5-13 TBS
Configuration:
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Site: MRBTS-200, Band 48 CBRS, TDD Config 2 (SA2)
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Software: SBTS20C_ENB_0000_002196_000000 (SRAN 20C 4.3)
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LTE44 actUl64Qam: true
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20+20 MHz carrier bandwidth
Questions:
1. Does the PUSCH scheduler in SRAN 20C use ue-CategoryUL-r12 for TBS selection when the UE reports split categories in the Cat 5-13 range?
2. If not, which SRAN release introduces this support?
3. Is there a parameter or feature activation required to enable R12 split category TBS handling?