Terminology » Difference between static and dynamic tdd in 5G NR

Difference between static and dynamic tdd in 5G NR

static tdd dynamic tdd 5g nr duplexing

Introduction : 5G NR (New Radio) uses TDD (Time Division Duplexing) widely especially in mid-band and mmwave frequencies. In addition it uses FDD (Frequency Division Duplexing) also.

In TDD, both uplink (UL) and downlink(DL) share same frequency but take turns in time slots to transmit/receive. A frame is divided into subframes/slots, which are configured for either DL or UL. Capacity depends on allocation of slots in DL or UL.

Static TDD

A fixed, pre-configured DL/UL slot pattern is same for all the cells in a network. This case works well when traffic demand is predictable. Example : Say in a frame pattern, 7 slots are allocated for DL, 2 for UL and 1 for special signals. Here every cell in the network follows the same ratio and timing.

  • Advantage : Simple, synchronized, low interference.
  • Disadvantage : The drawback of static TDD is that if users suddenly need more UL slots, they can not change it dynamically.

Dynamic TDD

In this mode, DL/UL slot configurations can be changed dynamically based on real time traffic needs. Each cell can adapt its slot pattern independently to match its traffic demand.

Advantage : High flexibility, better resource utilization Disadvantage : Creates cross link interference between UL of one cell with DL of another cell and vice versa. Needs advanced coordination.

Key differences

FeatureStatic TDDDynamic TDD
Slot PatternFixed, Pre-definedChanges dynamically based on demand
FlexibilityLow, not adaptable to traffic variationHigh, can match DL/UL demand in real time
Cell Co-ordinationAll cells use the same pattern; no cross link interferenceCells may use different patterns; risk of UL to DL interference.
ComplexitySimple to implementMore complex, requires coordination and interference management
PerformanceStable but may waste resources if traffic mix changesMore efficient spectrum utilization but challenging interference control

Conclusion: In 5G NR, static TDD offers simplicity and predictable performance but lacks flexibility, while dynamic TDD provides adaptive UL/DL allocation for efficient spectrum use at the cost of higher complexity and potential interference. The choice depends on requirement of traffic patterns. Static tdd is used for stable where as dynamic tdd is used for heavy loads and variable real time demand.