4 Replies Latest reply on May 4, 2018 5:35 AM by arh

    Clarification on Min and Max Advertisement Interval

    ssl.huynh_3143771

      We are wondering how the minimum and maximum advertisement value come into play with the advertising interval for ble.

       

      We have custom advertisement set with the same minimum and maximum advertisement value as seen in an example project, and advertisement works fine. So, we are wondering in what cases would we want the min. and max. values to be different or the same?

       

      Best,

      Steve

        • 1. Re: Clarification on Min and Max Advertisement Interval
          fwan

          Steve,

          As per clarification in BLE Core_v4.2 spec, "The Advertising_Interval_Min shall be less than or equal to the Advertising_Interval_Max. The Advertising_Interval_Min and Advertising_Interval_Max should not be the same value to enable the Controller to determine the best advertising interval given other activities."
          Because advertising events are perturbed in time using advDelay, the actual advertising interval should not be identical with the value, which is set with the two values(max/min) same.

          • 2. Re: Clarification on Min and Max Advertisement Interval
            ssl.huynh_3143771

            Hi fwan,

             

            Could you elaborate for us what the documentation means by "...to determine the best advertising interval given other activities"? An example would help clear some things up.

             

            Best,

            Steve

            • 3. Re: Clarification on Min and Max Advertisement Interval
              msur

              Hello Steve,

               

              The min/max intervals ensure the advertisement packets are transmitted with least collision losses. In order to establish a connection, it is important the central device receives the advertisement packets. If you transmit advertisement periodically at a fixed rate and if there is another device that transmits/uses the channel (can be a Wi-Fi device too) and blocks the advertisement, then your device is almost useless. Though advertising on all 3 channels at fixed rate may improve the chances of the advertisement going through. Still the chances of sending advertisement packets on all 3 channels at random rate (it is typically fixed interval with random delay before advertising - min/max interval is used to determine these values) has more chances of making it to the central device. Hence the recommendation of having different min and max interval.

               

              Let me know if this helps.

               

              Regards,

              Meenakshi Sundaram R

              • 4. Re: Clarification on Min and Max Advertisement Interval
                arh

                I like to think about the advertising interval as one of if not the most important power consideration.

                 

                There is a tradeoff between connection speed and power.  The more you advertise the faster the device can be connected... the slower your advertise the more power you save.