How can I solve a WiFi interference problem?

[Bob2.0]

I have been asked to get something working for a trade show. The devices are mostly Wi-Fi based. The only device with wired Ethernet ports is the router. How have folks solved this in the past? The devices are in an open environment so I can't put a faraday cage around everything. Is this something I can solve with coax cable and attenuators? I have been working out how to replace the antennas with coax for the ones that get used and terminations for the unused ports, but I don't know how beam shaping and MIMO algorithms will react to this. Any words of wisdom or pointers for how this can be solved or has been solved in the past are greatly appreciated.

Thanks for your help,

 

[ColinTaylor]

What kind of devices are you talking about and what frequency band? Also, what type of interference are you talking about - RF noise, adjacent and co-channel congestion?

 

[thiggins]

Your best hope is to operate devices in 5 GHz on DFS channels with 20 MHz channel bandwidth if you can get by with it.

 

[Bob2.0]

What kind of devices are you talking about and what frequency band? Also, what type of interference are you talking about - RF noise, adjacent and co-channel congestion?

Hi Colin,

The devices are our OEM equipment with internal 2.4GHz antennas talking through a router to cell phones or tablets. The interference is from the close proximity to other vendors and customers. I don't have any hard data on this. I guess it will be dozens of routers and hundred's of folks with cell phones in range at any given time. The complaint I was given is that Wi-Fi does not work well for anyone, if it works at all at trade shows. I started by asking if we could put everything in a faraday cage to reduce the external noise. The answer was no so I changed to a small faraday cage, coax cable. I don't know what troubles this will cause but there are sure to be some.

 

[Bob2.0]

Your best hope is to operate devices in 5 GHz on DFS channels with 20 MHz channel bandwidth if you can get by with it.

Hi Tim,

Our OEM device is locked to 2.4GHz. We can connect the cell phone or tablet over 5GHz.

I am looking into DFS now. That can help on the 5GHz side if we are allowed to use a cell phone or tablet that supports DFS.

 

[ColinTaylor]

Maybe you could cover the partitions/walls of your exhibition area with some snazzy advertising posters, that just happen to have a nice metallic backing material. It might help reduce some of the interference from your immediate neighbours.

 

[Bob2.0]

Hi Colin,

That's a good suggestion. I talked with the guys about doing that. They don't expect to have any external walls or places where we could add shielding. I will keep it in mind in case the setup changes.

 

[ColinTaylor]

What kind of area do you need to cover? How far away from the wireless router (I'm assuming everything is connecting back to a wireless router) will the client devices be? Can the router be placed centrally in the exhibition area?

If we're talking about devices that are only a few feet away from the router I doubt there'd be a problem. If people start wandering off, that could be an issue.

 

[Bob2.0]

Hi Colin,

I forgot to put this in the problem statement. We are streaming video to and from the OEM devices. We don't go higher than 1080p.

I will see what I can find out about the setup for the next show.

The next show is CES. Our section of the booth is towards the corner of the larger company booth, sort of under one of the convention hall cell phone repeaters. We get one Ethernet drop and we have our own Wi-Fi router. Our router is within ten or fifteen feet of the equipment we are showing. There's not a lot of flexibility to the setup at this point. The area was described to me as being a sea of other routers and folks with cell phones so, no hard facts.

The issues we are working on improving are stuttering and dropped video.

I can run the antennas from the equipment we are showing into a metal box with an access point, and use some attenuators to reduce signal strength in the box to reasonable levels. Then run Ethernet from the access point to the router.

 

[thiggins]

CES is a hellacious Wi-Fi environment, especially on 2.4 GHz. You'll be lucky to get anything to work. Doing a streaming video demo on 2.4 GHz; forget it unless you have huge buffers.

Your best bet would be two decent RF chambers, NOT "metal boxes". Cable box to box with sufficient fixed attenuation between to keep signal levels reasonable. You might not even need additional pads if you are going OTA inside both boxes.

Put a HD video camera in the RF box running to a monitor outside to view the screen.

 

[Bob2.0]

Hi Tim,

The video is streaming from a phone or tablet. The monitor is part of our OEM equipment.

We ordered some Ubiquiti parts to try. They have a small 2.4 GHz access point with an external antenna connector. The configuration I am planning to try first is to run coax, with some suitable attenuation, from the external antenna connection on the access point, to the antenna port on the OEM device.

I found some Yagi antennas that have a pretty good pattern for the part of this that must be wireless. I am going to put some attenuation in the lines to the Yagi antennas and point them up to minimize the number of devices in the pattern.

Does that sound reasonable?

 

[thiggins]

Coax connection between AP and device will require attenuation. You'll need probably 30 or 40 dB to avoid overloading the receivers.

I don't think the Yagi's will work.

 

[Bob2.0]

Hi Tim,

I have some 10 and 20db attenuators to get started. I will check signal strength and we should be able to adjust the output of the access point to keep the difference from causing a problem.

We need to show wireless streaming. What should I be looking at to help that part work? I don't think the phone or tablet we are using supports DFS.

 

[thiggins]

We need to show wireless streaming. What should I be looking at to help that part work? I don't think the phone or tablet we are using supports DFS.

As I said, at CES, WiFi based demos are iffy at best. Forget trying to stream in 2.4 GHz. I don't have anything else for you other than what I've already suggested.

 

[Bob2.0]

As I said, at CES, WiFi based demos are iffy at best. Forget trying to stream in 2.4 GHz. I don't have anything else for you other than what I've already suggested.

Ok, thank you for the suggestions. They are very helpful. We can plan to do the streaming over 5GHz. I ordered access points and Yagi antennas for both frequencies.

 

[Alin Martin]

This may be some number if things ... But if I had to spend some time guessing ... I would say your problem is caused by channel interference. Most people who install wireless routers use their own default channels ... So ... Everyone uses the same channel ... You should have about 10 different channels for you to choose from.

 

[RMerlin]

As I said, at CES, WiFi based demos are iffy at best. Forget trying to stream in 2.4 GHz. I don't have anything else for you other than what I've already suggested.

I hadn't thought about it before, but this might be a situation where 802.11ad could prove useful, due to its very short range.

 

[Bob2.0]

I hadn't thought about it before, but this might be a situation where 802.11ad could prove useful, due to its very short range.

Wow, that's a good suggestion. I don't think the cell phone the guys want to use has that but I will check.

 

[RMerlin]

Wow, that's a good suggestion. I don't think the cell phone the guys want to use has that but I will check.

Highly unlikely they do unfortunately.

 

[sfx2000]

11ad is not a solution in OP's case - don't waste time there...