DSS
Dynamic Spectrum Sharing: a feature enabling LTE and NR to coexist on the same carrier frequency by dynamically allocating resources between the two technologies.
DSS lets LTE and NR share the same carrier at the same time, allocating resources between them dynamically from one slot to the next. The point is migration economics: an operator can light up 5G on existing low-band spectrum without clearing LTE off it first, then shift the split toward NR as 5G traffic grows and LTE traffic fades — all in software, no re-farming required.
The clever part is fitting NR around LTE's rigid, always-on signals. LTE transmits cell-reference signals and control regions on a fixed grid that can't move, so DSS schedules NR transmissions in the resource elements LTE leaves free, using NR's rate-matching to dodge the LTE pilots. That coexistence isn't free — the overhead of working around LTE means DSS spectrum is less efficient than a clean NR carrier, and it's typically deployed on sub-1 GHz coverage bands as a stopgap rather than a capacity play. It buys broad early 5G coverage cheaply; operators move heavier traffic to dedicated mid-band carriers where they can.
Frequently asked questions
- Why is DSS less efficient than a dedicated 5G carrier?
- Because NR has to work around LTE's fixed transmissions on the shared carrier. LTE's cell reference signals and control channels sit on a rigid grid that can't be moved, so NR can only use the resource elements left over and must rate-match around the LTE pilots. That coordination overhead means a DSS carrier delivers less NR throughput than the same spectrum running NR alone — which is why operators use it for coverage and shift heavy traffic to dedicated mid-band.
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