Meaning
Subcarrier spacing configurations in narrow-band internet of things systems determine the bandwidth and number of individual channels available for parallel uplink transmissions. The chosen NB-IoT tone spacing is either fifteen kilohertz or three point seventy-five kilohertz, depending on the coverage requirements and device capabilities. These options allow operators to optimize the network for either high data rate throughput or deep signal penetration.
Subcarrier Allocation
Narrow subcarrier spacing enables a higher power spectral density. Utilizing the three point seventy-five kilohertz NB-IoT tone spacing option yields a twelve-decibel gain in coverage. This mode works well for utility meters buried deep within buildings.
Frequency Error
Inaccurate signal tracking is highly sensitive to frequency offsets between the transmitter and the receiver. When utilizing the tightest NB-IoT tone spacing, even minor oscillator drifts can cause inter-subcarrier interference and degrade the quality of the uplink. The receiver must implement advanced signal processing to track and neutralize these offsets, which adds computation time but preserves the integrity of the data link.
Uplink Throughput
A wider channel spacing allows for higher peak transfer rates but reduces the overall coverage budget. When fifteen kilohertz NB-IoT tone spacing is selected, the device transmits data faster and returns to low-power sleep mode quickly. This trade-off balances energy consumption with the necessity of transmitting larger data payloads.
