Automatic Transmit Power Control for responsible use of GURL frequencies outdoors

Ever since mass-produced outdoor General User Radio Licence (GURL) products hit the market, there has been the fear that the entire 2.4GHz and 5GHz bands would collapse and become completely unusable. This is true in some high-density urban city areas and certain radio towers. What we tend to see though is that the manufacturers are always keeping one step ahead and are working on the next piece of technology, enabling them to continue selling their products and services.

Many advances have come due to the ever-reducing cost of fast, high-speed processors and new manufacturing techniques that allow for the use of very accurate digital RF filtering circuitry while enabling the use of extremely high frequencies.  We are now seeing the mainstream use of 60,70 and 80GHz and ongoing research into the 95GHz to 3,000GHz potential uses. RF Shielding has also become very popular across all manufacturers, as it should be. 

Due to the cost, many of the advances were reserved for the higher end manufacturers, but now we are seeing a general adoption across the industry of interference reducing design being included in most outdoor equipment.  Automatic Transmit power control (ATPC) is a very powerful tool that has been around since early RF systems but has not been widely implemented into 802.11 based radio systems until recently. The IEEE 802.11h-2003 standard includes methods for reducing interference by using Dynamic frequency selection (DFS) and Transmit power control (TPC) and has been around since the early 5GHz 802.11a products.  

Automatic Transmit power control allows the user to select the best RX level for the modulation required and this then controls the TX power at the remote end. The standard also ensures that the transmitters remain within the TX levels needed by the local regulators.  The other advantage is that during times of signal fade due to weather conditions, the TX power will automatically adjust to keep the link stable and within spec. 

Some of the many advantages of ATPC are:

  • Reduced noise floor and general interference in the surrounding area
  • Lower TX power often allows for higher TX and RX QAM rates 
  • Reduced likelihood of overloaded receiver on short links
  • Less transmitter power consumption
  • Longer amplifier component lifespan
  • Makes pre-configuration of equipment before installation easier
  • Automatically compensates for signal fade, if within range limits 

When you put all these benefits together, it makes it easy to see why you should enable Automatic Transmit Power Control whenever your radios support it. Sometimes it can be just a firmware upgrade to a version that includes ATPC. If you are unfamiliar with your radios full feature set, we encourage you to undertake industry training to keep you up to date and become a responsible spectrum user.

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