3 Replies Latest reply on Jan 13, 2020 1:03 AM by ZhengbaoZ_96

    CYW4356 802.11ac WiFi real speed




      We are employing your CYW4356 WiFi transceiver to connect our android device to our WiFi network.

      The objective is to use 802.11ac standard to benefit it's transmission speed.


      We are using a Technicolor TC7230 WiFi router.

      WiFi router specification: 5.0 GHz (3x3) IEEE 802.11ac AP with IEEE 802.11ac compliant transmit beamforming

      Technical Datasheet:



      Specifically we use an AMPAK AP6356 module (integrates a BCM4356/CYW4356), our android device's CPU is an Amlogic S905X2 and our device has 2 physical antennas.

      AMPAK AP6356 Technical Datasheet:





      We perfomed multiple speed tests and used different WiFi network analyzers to know what was the transmission speed and MIMO,Modulation and Encoding used.


      WiFi network analyzers informed us PHY speed 866.66 Mbps, which means 2x2 MIMO 256QAM 5/6 Encoding.


      But real speed is 200 Mbps (we never obtained greater than 250 Mbps)


      We performed the same test (same test conditions) with another android 2x2 MIMO device (PHY speed 866.66 Mbps) and real speed was 446.6 Mbps (always around 400-450 Mbps)



      We know MAC efficieny determines real speed, reducing PHY speed around 50%-70% (such as the other android device tested)



      We are trying to understand why speed is so low.

      Is it due overheads such as interframe space, ACKs or MAC headers?

      Is there any other cause that can reduce the real speed?


      Thank you for supports,

      Kind regards,


      Antonio Valbuena Sánchez

        • 1. Re: CYW4356 802.11ac WiFi real speed

          Actually, I used to support a project of 4356 with pcie interface, the highest T/P value is more than 600Mbps with MIMO mode.  So  my suggest is :

          1.  can set the S905X2 cpu into performance mode to see if the T/P can be upgrade.

          2.  capture sniffer logs to check if re-transmission was happening frequently, better to test the T/P in a

             clean environment.

          3.  check the TCP windows setting to see if it can be modified.

          4.  check the communication interface,  if SDIO ,  to see if we can adjust the driver or other setting like from 2.0 to 3.0 to get hight T/P .

          1 of 1 people found this helpful
          • 2. Re: CYW4356 802.11ac WiFi real speed



            Thank you very much for supports.

            It is encouraging to know you obtained more than 600Mbps with the CYW4356 WiFi transceiver.


            We are going to follow your suggestions.


            1. Ok, CPU can be set to performance mode. Could you please specify what does "T/P" mean and how can be upgraded in a CPU?

            2. We will check if re-transmissions are frequent. Could you please suggest a software or hardware to capture sniffer logs?

            3. We will check TCP window and modify it if possible

            4. We will check the communication interface and adjust the driver to obtain a higher T/P


            Thank you,

            Kind regards,


            Antonio Valbuena Sánchez

            • 3. Re: CYW4356 802.11ac WiFi real speed

              for  performance , the command is similar as below:

              # echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

              I think you do not need an expensive sniffer tool for the tuning, you can test the T/P in an clean environment without AP in the test channel .

              then to check the communication interface .

              finally,  have an tuning on TCP layer.