How to achieve success in non-line-of-sight environments

The propagation of signals between the transmitter and the receiver is obviously central to the reliability and availability of any wireless radio link.  In an ideal scenario, the two radios would have a clear line-of-sight (LOS) between them but in crowded urban settings where buildings may get in the way, achieving line-of-sight may not be practical or even possible.

And it’s not just urban settings where things get tricky – rural environments have different terrain issues to contend with such as tree cover, hills and paths over water which will impact both line-of-sight and precisely how the signals propagate.

Successful links can be achieved, however, with Non-Line-of-Sight (NLOS) paths, but they will require a) comprehensive path planning prior to deployment and b) radios which have been engineered to cope with sub-optimal RF conditions.


What is an NLOS path?

As the name suggests, non-line of sight is where the transmitter and receiver cannot “see” each other.  As a result of obstructions in the path (which could be a grove of tall trees, a multi-storey building or reflections off a body of water) the received signal is typically made up of the vector sum of several multi-path components.

Each of these components has scattered off objects along the way to the receive antenna and each arrives with a slightly different delay.  This results in neighboring data symbols being blurred on top of each other, causing data errors.


How do Mimomax radios manage NLOS paths?

Our MIMO receivers apply an adaptive equalizer that trains itself on the received signals to a) align all of the energy associated with a given symbol and b) cancel the energy associated with neighboring symbols.  This substantially mitigates the impact of such multi-path propagation.

Furthermore, this MIMO equalizer also applies the same process to constructively sum up the energy for a given symbol from both of the receive antennas, while rejecting the energy associated with symbols sent from the other transmitter.

In operating this way, the Mimomax radio uses all of the available signal energy to give the best chance of decoding the wanted signal – even in difficult propagation environments, such as NLOS.  The Mimomax team couples this sophisticated wireless technology with comprehensive path planning from one of our in-house experts to ensure the link will perform as required.