WCS - Link Test Results - Uplink/Downlink

Answered Question
Mar 20th, 2009
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Hello all,


Can anyone tell me what the meaning of the link test results are. Mainly the following:


"Packets Transmitted at different Rates"


On the "uplink" I assume this is from client to AP, I get varied packets sent at different rates.


but


On the downlink (assume this is from AP to client), they are always at the lowest rate.




1st, Have I got uplink and downlink the correct way round? Uplink, client-to-ap, downlink, ap-to-client????


2nd. Does the downlink indicate a problem as all packets are at the lowest rate?


Please see attached.


Many thanks indeed for your help,


Kind regards,

Ken



Correct Answer by dennischolmes about 8 years 5 days ago

You have it correct. The problem you are seeing is the result of signal degradation from the client to the AP due to a mild form of multipath. This occurs due to limited antenna arrays on client devices. In a perfect wifi world you would see synchronous upload and download datarates. Unfortunately the only perfect wifi world exists in a lab. As you learn more about packet capture and decoding you will see very strange things happening several time per minute in the spectrum. Using Airmagnet Handheld Analyzer you should look for very few -5db sweeps. Less than 5 per second and the network is fairly stable. More and you want to redesign and stabilize the cell. Downlink is usually shown as the lowest data rate advertised on the contoller because most client devices can't report back what they actually see.

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Correct Answer
dennischolmes Sat, 03/21/2009 - 16:12
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You have it correct. The problem you are seeing is the result of signal degradation from the client to the AP due to a mild form of multipath. This occurs due to limited antenna arrays on client devices. In a perfect wifi world you would see synchronous upload and download datarates. Unfortunately the only perfect wifi world exists in a lab. As you learn more about packet capture and decoding you will see very strange things happening several time per minute in the spectrum. Using Airmagnet Handheld Analyzer you should look for very few -5db sweeps. Less than 5 per second and the network is fairly stable. More and you want to redesign and stabilize the cell. Downlink is usually shown as the lowest data rate advertised on the contoller because most client devices can't report back what they actually see.

kfarrington Mon, 03/23/2009 - 02:47
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Hey Dennis,


Many thx indeed,


I am glad to see that the downlink "usually" at the lowest data rate. That was concerning me.


Many thx for the other clarification :)


Kind regards,

Ken

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