4G vs 5G Resource Allocation
Visual side-by-side comparison of how LTE and 5G NR lay out resources in time and frequency. Toggle numerology, inspect BWP, and see why NR is so much more flexible.
Slot = 0.5 ms · 2 slots/subframe
LTE Resource Block
SCS 15 kHz · 1 ms subframe5G NR Slot
SCS 30 kHz · slot 0.5 msKey differences at a glance
- Slot duration: LTE is fixed at 0.5 ms per slot (2 slots / 1 ms subframe). NR scales with numerology — 0.5 ms at 30 kHz SCS.
- Numerology: LTE uses only 15 kHz SCS. NR supports 15/30/60/120/240 kHz and can mix numerologies in the same carrier.
- BWP: NR defines Bandwidth Parts so a UE can live in a narrow slice of a wide carrier to save power. LTE has no such concept — UEs always monitor the full carrier.
- Mini-slots: NR can schedule a transmission over just 2, 4 or 7 symbols for URLLC. LTE schedules whole subframes only.
- PDCCH position: LTE PDCCH occupies the first 1–3 symbols of every subframe, across the full bandwidth. NR uses CORESETs — configurable in time and frequency — giving much more scheduling flexibility.
Feature comparison
| Feature | LTE (4G) | 5G NR |
|---|---|---|
| Subcarrier spacing (SCS) | 15 kHz (fixed) | 15 / 30 / 60 / 120 / 240 kHz |
| Symbols per slot | 7 (normal CP) | 14 (normal CP) |
| Slot duration | 0.5 ms | 1 / 2^μ ms (e.g. 0.5 ms at 30 kHz) |
| Min. scheduling unit | 1 subframe (1 ms, 2 slots) | 1 slot, or mini-slot (2/4/7 sym) |
| Radio frame duration | 10 ms (10 subframes) | 10 ms (10 × 2^μ slots) |
| Mixed numerology | Not supported | Supported — different SCS in same carrier |
| Resource allocation unit | Resource Block (12 SC × 7 sym × 2 slots) | PRB (12 SC × 14 sym) within a BWP |
About resource allocation in LTE vs 5G NR
LTE was designed around a single numerology — 15 kHz SCS, 1 ms subframes, 7-symbol slots under normal cyclic prefix. Every UE in the cell listens to the first 1–3 symbols of each subframe for PDCCH across the full channel bandwidth, then decodes its PDSCH in the rest. Simple and predictable, but rigid: a UE on a 100 MHz carrier would waste power monitoring frequencies it doesn't need, and there was no way to shorten a transmission for ultra-low latency.
5G NR replaced that with a scalable numerology (μ = 0 to 4), slots of 14 OFDM symbols, configurable CORESETs for PDCCH, Bandwidth Parts so a UE can operate on a narrow slice of a wide carrier, and mini-slots for URLLC. The fundamental RE-count per slot is the same (12 × 14 = 168), but the time and frequency elasticity is what enables eMBB, URLLC and mMTC to coexist on the same radio.
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