Non-Line-of-Sight (NLoS) refers to a type of communication in wireless networks where the signal path between the sender and receiver is obstructed by physical objects such as buildings, trees, or hills. Despite these obstructions, the wireless signal can still reach the receiver, although the signal strength and quality might be degraded.

Here are some key points regarding NLoS communication:

  1. Signal Propagation:
    • In NLoS scenarios, signals may reach the receiver by reflecting off other objects, diffusing around obstacles, or, to a lesser extent, penetrating through obstacles.
    • Lower frequency signals, such as those used in TV White Space (TVWS) technology, are better suited for NLoS conditions as they can more easily diffract around obstacles and penetrate through some materials.
  2. Technologies Suited for NLoS:
    • TVWS and other low-frequency radio technologies are often used for NLoS communication. Some Wi-Fi technologies and devices also have capabilities to handle NLoS conditions, although their effectiveness may be limited compared to lower frequency alternatives.
    • Multi-Input Multi-Output (MIMO) technology, which uses multiple antennas at the transmitter and receiver, can also enhance performance in NLoS conditions by exploiting multipath propagation.
  3. Applications:
    • NLoS communication is crucial for providing wireless connectivity in urban areas with dense buildings, as well as in rural or hilly areas where a clear line of sight to the transmitter is not possible.
    • It can be used for various applications including broadband internet access, wireless backhaul, emergency communication systems, and IoT (Internet of Things) connectivity.
  4. Challenges:
    • The primary challenge in NLoS communication is the degradation of signal strength and quality due to obstructions.
    • Multipath propagation, where signals take multiple paths to reach the receiver, can cause interference and degrade the signal quality further.
  5. Solutions:
    • Deploying additional relay nodes or base stations to provide alternative paths for the signals.
    • Using directional antennas to focus the signal strength and minimize interference.
    • Employing advanced signal processing techniques to mitigate the effects of multipath propagation and improve signal reception.
  6. Advancements:
    • Research and development continue to explore technologies and methodologies to improve NLoS communication, including leveraging AI and machine learning for better signal processing and network optimization.

Non-Line-of-Sight communication remains a critical enabler for ubiquitous wireless connectivity, especially in challenging environments.