Evaluating Sub Gigahertz Spreading Factors against Cellular Coverage Enhancement Energy Costs
Sub-GHz LoRaWAN spreading factors consume less baseline battery energy than NB-IoT coverage enhancement repetitions in deep indoor deployments.
Sub-GHz Spreading Factor
Meaning
Modulation parameters adjust the relationship between signal duration and chip rate in wireless communication. A sub-GHz spreading factor defines the ratio of the frequency of the chip rate to the frequency of the base signal. High values increase the time per symbol to improve link budget in environments with heavy attenuation.
This configuration allows nodes to transmit over longer distances by pushing the signal power below the noise floor.
Signal Budget
Increased values demand more time for each packet transmission. Battery consumption rises as the radio remains active longer to complete the process. Range extension happens because the receiver distinguishes the coded data from background interference.
Sensitivity gains allow successful demodulation of signals that would otherwise disappear in ambient noise.
Integration Constraint
Link synchronization requires both the transmitter and receiver to agree on the chosen factor before communication initiates. Hardware manufacturers select the range of values based on the processing capacity of the baseband chip. Incorrect settings during board bringup prevent the establishment of a network connection entirely.
Thermal limitations prevent constant usage of the highest values due to excessive radio duty cycle heat generation.
Data Throughput
Effective bandwidth drops as the chosen factor rises. Longer symbol durations result in fewer bits per second transferred across the air interface. Applications requiring frequent sensor updates prioritize lower values to maintain speed and minimize latency.
Dense networks sacrifice range to ensure each node clears the channel quickly for subsequent traffic.