9 Replies Latest reply on Jun 24, 2015 4:06 PM by GregG_16

    Range Testing with WiCED WiFi

      Hi,

       

        I'm doing range testing using BRCM943362WCD4_EVB evaluation boards. I'm particularly interested in the throughput that I can get between two such boards at a distance of 100m, 200m, 300m and so on.


        I've built the test.console application that comes with the WiCED SDK. The debug option is not enabled. To conduct the test I'm running iperf between two boards - the first boards configured as an AP and the second one as a STA. I'm ok with a throughput as low as 200 kbps and my main interest is in the range.


        With this configuration, I'm not able to run the tests beyond about 50 meters (line of sight). The throughput drops rapidly beyond this distance.


        I have the following questions:

      1. Is there any particular setting to increase Tx power, Rx sensitivity, etc to increase the range.

      2. Is there any other mechanism to increase the range - eg enable antenna diversity ?

      3. I'm currently using the PCB antenna. Will an external antenna help to increase the range. If so, what is the part number for external antenna and how do I enable this in software.

      3. Are there any sample test results available for range vs throughput. What is the maximum range I can expect if I'm ok with a throughput of about 200 kbps ?


      Thank you

      ngupta

        • 1. Re: Range Testing with WiCED WiFi
          FeTu_2131621

          1. wiced_wifi_set_tx_power (wwd_wifi.h)

          2. by default, you are in "antenna = 3 -> enable auto antenna selection ie. automatic diversity", you can use wwd_wifi_select_antenna to switch antenna.

          3. Better antennas can give you better range. wwd_wifi_select_antenna lets you select your antenna.

          4. The issue with range vs. throughput is that it doesn't consider how clean the environment is.  We tested at 100m with a very clean environment and had no problems doing 200 kbps, that being said, if you're environment is crowded (with lots of wifi devices) you can struggle to get decent throughput event at 10m.  In one instance we had a MacBook transmitting to an AP that was 20m away, but it was so loud (in dB) that our device had trouble transmitting with an AP  (on the same channel) that was only 3m away.

          • 2. Re: Range Testing with WiCED WiFi

            Thanks! Few more follow-on questions:

             

            1. What is the maximum value that I can set for tx_power to stay within FCC regulatory limits.

            3. Can you recommend part numbers for suitable antennas that can be attached to the WICED BRCM943362WCD4_EVB evaluation board. The board already has two connectors.

            4. Assuming an absolutely clean environment, what is the maximum range I can get with a reliable throughput of 200 kbps (let's say for udp packets) ?

            • 3. Re: Range Testing with WiCED WiFi
              FeTu_2131621

              1.  That will be based on your antenna (based on loss/gain in the whole path from transceiver to antenna)

              2.  I don't have a good recommendation for something that works with the eval board, because we do not use the eval board.

              3. You will have to test to see how far you can get in an absolutely clean environment.  A lot of these ranges will be based on the specific design/implementation of your device.  All I know is that with our device, which operates within FCC limits, we were able to transmit at least 200Kbps at 100m distance in a relatively clean environment (a big building with 1 AP running and most wireless mice and keyboards disabled).  You will have to test with your system to be able to determine your throughput limits for each range.

              • 4. Re: Range Testing with WiCED WiFi

                Thanks!

                Meanwhile, I checked the tx_power level and it is already at 31 which is already the maximum value.

                Antenna diversity is also enabled.

                Even in a clean environment, I'm not able to reach beyond 50 m.

                 

                Is there anything else that I can do to increase the range?

                • 5. Re: Range Testing with WiCED WiFi
                  GregG_16

                  The board you have is a reference design. It is not optimized for range. It uses low cost pub etched antennas. You would have to work with an antenna vendor to see what external antennas or chip antennas are available.

                  • 6. Re: Range Testing with WiCED WiFi
                    FeTu_2131621

                    Just like Gangi said, the antenna  and transmit path on the development board is probably not loss-less (net gain).  The TX power being set to 31 only means that the chip will try to transmit at that power, but then you have losses and gains in the path.

                     

                    I think, in our case, transmitting with the default tx power, using our mounted antenna gives us a transmit power of about 18 dB as measured outside our device.

                     

                    You would need to measure your output (with any packaging you put on your product) to be able to see if you can afford to turn up the power.  My guess is that you could turn in up significantly, before you are close to hitting FCC limits.

                     

                    EDIT:

                     

                    Also, how do you know your environment is clean?  If you used an analyzer to confirm that it's clean, then you can also use the same analyzer to see what power your device is outputting.  If you don't have an analyzer, then remember that phones, laptops, PCs, ect. with wifi on will crowd the spectrum, and that wireless mice and keyboards (and other wireless adapters) also work in the 2.4GHz band, but do not use 802.11.  This causes lots of noise on the band, which raises transmit errors and reduces your range/throughput.  In our building, our IR security sensors have to be disabled during the day because they output noise across the whole 2.4GHz spectrum at 30dB which is louder than our device.  If we don't disable those, even though there are 0 devices on the network, our range is reduced to 3m to 5m and our throughput is clamped down significantly.

                    • 7. Re: Range Testing with WiCED WiFi

                      Your question about whether the environment is clean is a good one. I'm doing my testing in a big park at a time when there are not too many people around. I also did a Bluetooth Inquiry and WLAN Scan - At least there are no Bluetooth or WiFi devices around, though there could be any other 2.4 GHz transmissions.

                       

                      I don't have a spectrum analyzer. So there's not much I can test to ensure that the environment is really clean.


                      Couple of questions:

                      1. From our own testing, what is the maximum range that I should be able to reach either with the evaluation board or some other boards. Do let me know if you recommend any other boards for range testing.

                      2. Any recommendation on the antenna that I should use on the evaluation board.

                      • 8. Re: Range Testing with WiCED WiFi
                        FeTu_2131621

                        I don't have an answer/recommendation for either question.  We did not use the development board in our development.

                        • 9. Re: Range Testing with WiCED WiFi
                          GregG_16

                          Please open a new discussion if you have further questions or send me a message.