Backhaul uplink/downlink %

I am not sure if I am missing something obvious here, but I am somewhat confused as to why when it comes to bandwidth allocation, backhaul units are generally set to 50% Down, 50% Up, where as AP’s are generally set at 75% Down, 25% Up. What I mean is that I understand why the AP’s are set to 75/25. That makes sense that most traffic is in the download direction for normal users. But the BH is just an extension of that connection to the router and the cloud, so the traffic flowing through the BH is still 75/25, so shouldn’t the BH be set to mimic the AP’s set up?

Set them however you need them. We set our AP’s and BH’s both at 75%.

jmaysww wrote:
Set them however you need them. We set our AP's and BH's both at 75%.

So I have 2 more questions:

1. Does the downlink percentage literally split the pipe at all times. So if I have a 10Mb BH (which I guess has an aggregate useful throughput of 7Mb) and I have it set to 50% downlink, does that mean that the most bandwidth I can push through it for downlink is 3.5Mb even if there is absolutely no uplink traffic? Or would the BH allow more traffic to go through in one direction of there is no activity in the opposite direction.

2. Also, won't the location of the BH in terms of it being a master or slave affect what would be considered downlink? If for this example and for the sake of making this easy we forget that the network traffic is two way (since 90% of it is downloads in our case), and just concentrate on sending data downstream as clients are using the bandwidth at their homes, If I have a situation where the slave BH is at my headend, and the master unit is next to the AP that is feeding customers, then wouldn't the majority of the traffic actually being UPLOADED to the master unit from the slave unit?

Cloud ---> Headend ---> Slave BH ---> Master BH ---> AP ---> SM

And if so, does this mean that you should always have your master BH upstream from the slave unit?
  1. Canopy radios are not full duplex. They use the same radio and antenna for transmitting as they do for receiving. So when the downlink is set to 75% then it spends 75% of the time transmitting and 25% of the time receiving. So if you set them at 50% the max will always be 3.5x3.5 regardless of the ammount of bandwidth actually being used.

    2) Yes, master and slave position matter. Remember, the percentage is transmit time from the master. So if your master is closer to your customer than your slave you’d want to set it at 25% which would give you more download than upload.

    Keep in mind than if you have multiple backhauls leaving 1 tower site you want to have them all setup the same and use a cluster management module to time their transmit/receive cycles together. This way all radios transmit and receive simultanously and don’t interfer with eachother. You dont want one radio transmitting while another is trying to receive from another tower, etc. If you keep the radio frequencies far enough apart you can make them different such as the case of a BH being at 25% and the access points all at 75%.