Meaning
Multipath propagation effects cause rapid fluctuations in the received signal strength of wireless devices when there is no direct line of sight. The presence of rayleigh fading can result in intermittent packet drops for mobile sensor nodes operating in dense industrial environments where metal structures reflect the radio waves. This phenomenon applies to non-line-of-sight environments and is not modeled for direct-path communications.
Multi Path Propagation
Radio signals traveling from a transmitter to a receiver take multiple paths due to reflections off walls and machinery. Under conditions of rayleigh fading, these reflected signals arrive at the receiver at slightly different times and with different phases. This phase difference causes constructive and destructive interference, which can create deep signal nulls that are difficult to predict.
Signal Mitigation
Antenna diversity and error correction coding are used by wireless modules to overcome the signal drops caused by multi-path interference. By using two antennas spaced slightly apart, the receiver can select the stronger signal because it is unlikely that both antennas are in a signal null at the same time. This hardware configuration is supported by software algorithms that dynamically adjust the data rate based on signal quality.
These combined techniques allow the device to maintain its data link even when operating in heavy multipath environments.
Performance Evaluation
Testing the wireless modules in simulated fading environments ensures that the hardware can maintain the connection under realistic conditions. Engineers use specialized channel emulators to apply rayleigh fading profiles to the radio frequency link during the verification phase. This testing ensures that the wireless product will operate reliably in complex environments like factories and automated warehouses.
