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.
Thermal Noise Floor 125 Khz
Meaning
Power density levels define the minimum theoretical noise present in a radio receiver across a specific bandwidth at a given temperature. The thermal noise floor 125 khz represents the background electronic hiss that sets the limit for the weakest signal a LoRa or similar narrowband receiver can detect. This value is calculated using Boltzmann’s constant, the absolute temperature in Kelvin, and the bandwidth of 125,000 Hertz.
At room temperature, this floor typically sits near minus 123 decibel milliwatts.
Sensitivity Limit
Radio systems cannot decode information that falls below this level without advanced processing techniques. Because the thermal noise floor 125 khz is a physical constant, engineers improve range by reducing the noise figure of the internal amplifiers. Every decibel of noise added by the hardware reduces the maximum distance of the link.
Bandwidth Impact
Widening the channel increases the amount of noise collected, which raises the floor and obscures faint signals. A thermal noise floor 125 khz is higher than that of a 12.5 kilohertz channel, meaning narrower bands generally provide better range. This trade off is fundamental to the design of long range wireless protocols.
Environmental Factors
Heat increases the random movement of electrons, which directly raises the background noise level. In hot industrial environments, the thermal noise floor 125 khz might rise by several decibels, potentially breaking a marginal connection. Thermal management of the receiver housing helps maintain a stable noise profile.