Panadapter lag, network latencies?

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While experimenting today I connected to the 6700 over wifi and moved around a bit. I got into a situation where the panadapter was noticeably lagging behind - maybe a second or so - comparing the visualisation to the audio I was hearing.

Once I reset the wifi and reconnected, everything was back in sync (e.g. indiscernible lag), so I'm not concerned here. However, it made me idly curious about maximum network latencies and whether there were any plans to do adaptive streaming rates and resyncing if things get out of whack. I run a number of wifi repeaters to cover the house, so probably that's responsible for a jump in latencies as I moved about.

Presumably at some point we'll get simultaneous audio streaming to the client too, which one might imagine involving more adaptive use of the data stream.
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Posted 6 years ago

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Stu Phillips - K6TU, Elmer

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Make sure that you don't have other neighboring access points on the same channel(s). One of the nasty challenges with WIFi at 2.4 ghz is that there are o ly three or four completely separate channels - and everyone uses them.

Cochannel QRM is a major cause of slow WiFi and that's all you see.

Depending on your repeaters, they can cause more harm than good - depends on the manufacturer.

The real solution is multiple access points connected to a wired network. I have three in my house and they still only cover the areas we spend the majority of time.

YMMV but worth a thought.
Stu K6TU
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Yeah, I'm too lazy to run ethernet cabling around the house, hence the repeaters :-)

Anyway, I'll usually be in my office/den/shack, for which this is simply a non-issue (either because I'll be on wired ethernet or adjacent to the main wired wifi base station.

I guess if this is pure latency, then there's not much that can be done anyway - you get as much lag as is implied by the communication path but at least all the data arrives, albeit a bit 'late'.

If the audio is eventually streamed in addition, then it should at least be in sync with the pano data and other telemetry even if there's a lag. I'm looking forward to that, and the option to do remote operations, if only from different rooms my my house... but that's probably a long way down the road yet.
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Graham - KE9H, Employee

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The way most WiFi repeaters work is that they store and forward on the same RF channel, which means that they cut the usable bandwidth of the system in half and double the RF channel related latency. Multiple repeaters necessarily will do more damage.

If you have a WiFi coverage issue, Stu's solution of multiple WiFi base stations (access points) connected by hard cable is a much better coverage solution with respect to latency and capacity.

--- Graham / KE9H
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Steve - N5AC, VP Engineering / CTO

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There are two potential causes of latency in the panadapter:

1. There is real network latency that causes a delay of packets
2. The computer processing the packets is getting behind in processing.

In general, if you are able to stop the application and restart it and it clears the problem, it tends to say that you have problem #2 and not problem #1. If the computing device you are using to display the panadapter has a CPU load that is close to 1/number of cores (for example, if the machine is a 4-core box and the CPU is running 23-27%), you can check to see if the SmartSDR thread is consuming a core. If it is, you have problem #2. In this case, you have a couple of options. First, you could use a better video card to offload the CPU. Second, you can slow down the packet rate by turning up averaging of the panadapter.

There could be other issues, but this is my guess as to the two most common.