Quick easy for WiFi issues??

TL;DR - Try constraining HEX-NET down to lower 802.11 data rates.

I picked up three Cisco Aironet 1142N access points with the intent of improving my home wireless coverage. I am planning to place one of them out in the garage, to provide better coverage for a certain WiFi device, but I haven't gotten that far yet.

I've turned up one of them inside the house and it's been giving me much better insight. HEX-NET associates fine in Infrastructure mode from out in the garage, but it rate-shifts up and down constantly, and the AP sometimes boots it off due to excessive retries/timeouts. HEX-NET WiFi has been finicky for me at the best of times at any real range, even in AP mode.

Then I reconfigured the Aironet AP to only offer it the lowest 802.11g rate of 6.0Mbit (as compared to the max of 54.0Mbit). Then suddenly it's bulletproof. Ping is nice and clean. Desktop client auto-discovery always works. Desktop response is as smooth as Desktop gets. Mobile is responsive and network-test back to home base looks nice. Mobile Cloud functions started working right and that's never been the case for me before, although I'll grant it's been a while since I tried.

When HEX-NET is installed in a car, it's in a terrible EM environment surrounded by metal. HEX-NET needs smooth, predictable isochronous transfer far more than it needs higher 802.11 rates. I strongly suggest Ross-Tech experiment with this in-house... it was a complete game-changer for me.

Jason

Interesting insight -- thank you!

-Uwe-

jyoung8607 said:

it rate-shifts up and down constantly, and the AP sometimes boots it off due to excessive retries/timeouts.

Click to expand...

Interesting data point! As a note, most WiFi adapters can be configured to less-aggressively seek better APs and/or connections.

It just so happens I have an AP in my garage (hanging from the ceiling centered between the two bays and towards the back) and I've had no issues with HEX-NET running in AP mode in the car

Also as a note, I run dual-frequency APs (2.4/5GHz) and reserve the 5GHz band for my high-bandwidth devices - there can be some oddities mixing b and g devices on 2.4GHz too. All of this says that you might decide to repurpose an old AP with a dedicated SSID for HEX-NET use and avoid interaction with your other WiFi devices that way

solomon said:

Interesting data point! As a note, most WiFi adapters can be configured to less-aggressively seek better APs and/or connections.

Click to expand...

Agreed, but in this case I don't have roaming issues yet since I haven't installed my other two APs yet. I've just substituted one that gives me far better control and insight.

solomon said:

Also as a note, I run dual-frequency APs (2.4/5GHz) and reserve the 5GHz band for my high-bandwidth devices - there can be some oddities mixing b and g devices on 2.4GHz too.

Click to expand...

That's why I'm planning on three. One carefully-placed AP could cover everything I want in the 2.4GHz band, but 5GHz doesn't have nearly the same range or penetration. Fortunately B-only devices are getting pretty rare, but on the other hand 2.4GHz is getting pretty crowded. 802.11n at 300Mbit (40MHz channel width) on 5GHz is pretty nice without spectral interference from the neighbors or microwaves or cordless phones or Bluetooth or whatever.

solomon said:

All of this says that you might decide to repurpose an old AP with a dedicated SSID for HEX-NET use and avoid interaction with your other WiFi devices that way

Click to expand...

Perhaps, but that wasn't really my intent in posting this. People like you and me could rearrange their home network to suit this device, but we're not the only HEX-NET users. My thought process was basically this:

1) Ross-Tech is still fighting to get WiFi fully reliable.
2) I found that forcing lower-rate, longer-range 802.11 rates dramatically helped reliability in my environment, but I have to do backflips on my AP config for infrastructure, or desktop WiFi driver config in AP mode to make that happen.
3) I suggested Ross-Tech try the same to see if this is replicable and useful outside my own environment.
4) If Ross-Tech agrees, they have options to limit HEX-NET's 802.11 rates offered in AP mode or accepted in Infrastructure client mode, or possibly tweak the rate-shifting algorithm in their wireless driver, with zero end-user effort and no support calls.

Jason

jyoung8607 said:

1) Ross-Tech is still fighting to get WiFi fully reliable.
2) I found that forcing lower-rate, longer-range 802.11 rates dramatically helped reliability in my environment, but I have to do backflips on my AP config for infrastructure, or desktop WiFi driver config in AP mode to make that happen.
3) I suggested Ross-Tech try the same to see if this is replicable and useful outside my own environment.
4) If Ross-Tech agrees, they have options to limit HEX-NET's 802.11 rates offered in AP mode or accepted in Infrastructure client mode, or possibly tweak the rate-shifting algorithm in their wireless driver, with zero end-user effort and no support calls.

Click to expand...

-Uwe-

jyoung8607 said:

Perhaps, but that wasn't really my intent in posting this. People like you and me could rearrange their home network to suit this device, but we're not the only HEX-NET users.

Click to expand...

Agreed, sorry - in this case the "you" was very specifically that you personally might like that option

jyoung8607 said:

4) If Ross-Tech agrees, they have options to limit HEX-NET's 802.11 rates offered in AP mode or accepted in Infrastructure client mode, or possibly tweak the rate-shifting algorithm in their wireless driver, with zero end-user effort and no support calls.

Click to expand...

100% agreed and that was all I was trying to point out on the algorithm tuning - that one might be able to have one's cake *AND* eat it too

Richard

solomon said:

Agreed, sorry - in this case the "you" was very specifically that you personally might like that option

Click to expand...

Hey look buddy, I'm an engineer. That means I solve problems. For instance, what am I going to do if I have WiFi coverage problems? The answer: use an access point. And if that don't work? Use more access points.

On a partly related note, there are dozens of cheap WiFi repeaters/range-extenders on the market. At some point, it might be worth it for Ross-Tech to test and officially bless one of those, similar to what was done for the active USB extension cable for HEX-USB+CAN.

Fun fact: even with the 6 foot OBD2 extension cable that lets me sit HEX-NET up on the dashboard, I still have to remember to roll down my windows if I'll be outside the car. W12 Phaetons over here all have metal film IR reflective glass that really does a number on WiFi signal.

Jason

I tried to use the AP-mode equivalent of this tweak today but couldn't. My laptop's Broadcom adapter has settings for max rates, which I had hoped would be effective when using HEX-NET in AP mode, but they seem to be ignored. They may only be effective in ad-hoc or virtual AP modes.

I found something peculiar in my WiFi site survey tool. There is something about HEX-NET's WiFi beacons that are different from other typical access points. Something about it makes inSSIDer think it only supports 802.11b (up to 11Mbit) even though it advertises 802.11g rates (up to 54 Mbit). My only neighbor with a non-N router doesn't show up that way. For test purposes I reconfigured my Aironet for G-only rates and it doesn't show up that way either.

I am not sure why HEX-NET shows up that way, or what impact it might cause, if any. I do remember some posts about WiFi interop problems with certain chipsets and I wonder if this could be relevant. I would have to chat with some of my WiFi-specialized coworkers to find out what the difference is here. I'm not really a wireless expert, and we have some site-survey gear that can look closer at 802.11 frames and RF issues than I can.

Jason

hi Jason,

for interest sake, does your Cisco Aironet have settings for:
* WMM and,
* Short GI

Could you let us know whether you can use the higher rates with these two disabled?

best
Stephan

Stephan said:

hi Jason,

for interest sake, does your Cisco Aironet have settings for:
* WMM and,
* Short GI

Could you let us know whether you can use the higher rates with these two disabled?

Click to expand...

I can tune both of those things. Guard intervals can be set to long or auto (short GI dynamically enabled if compatible with associated clients) and I'm on auto. I believe WMM is on but I can turn it off (provided I disable 802.11n which requires it). Does HEX-NET try to use WMM QoS capabilities for real-time protocol data?

I am travelling on vacation with my family until late next week, on the beaches in Alabama and Florida. I do have my trusty HEX-NET with me just in case my Acadia needs help but my good APs are back at home in Ohio. Since I have a temporary surplus of Aironets, when I get home I'll dedicate one for HEX-NET tinkering and chart out hrping results for each variant.

Jason

Enjoy the family vacation!

HEX-NET does not use WMM... but the web is full of references to WMM and especially Short GI causing havoc..

Once you're home, if you cannot disable GI on yours, select long and get some ping stats... should be interesting... and should allow you to up the rate...

Interesting about your Soft AP mode... I switched mine to Soft AP and it shows b/g and 54Mbps... maybe something related to your laptops broadcom adapter?


Stephan

Stephan said:

... but the web is full of references to WMM and especially Short GI causing havoc..

Click to expand...

Could you be more specific? I'm not aware of major problems in this area, but wireless is only tangentially related to my day job. I did some light Googling and didn't immediately come away with an idea of what you're speaking of.

Stephan said:

Once you're home, if you cannot disable GI on yours, select long and get some ping stats... should be interesting... and should allow you to up the rate...

Click to expand...

Guard interval isn't something you can disable. You only have some influence over its duration: mandatory 800ns long, or optional 400ns "short" available to clients that support it with 800ns to clients that don't. Also, my understanding is that short GI is strictly an 802.11n thing whereas the HEX-NET radio only supports 802.11g. However, I am teetering on the far edge of stuff I understand about wireless.

All this said, I did run across a reference to longer guard intervals possibly being of value in environments with multipath reception problems (multiple copies of a signal being received at slightly off-set times due to bounces and reflections). I'm sure being inside a metal-and-glass box is going to create multipath issues. This could be of value if 802.11n radios in a mixed cell running short GIs can step on (or be stepped on by) 802.11g radios in a bad multipath environment. I will run some tests when I get home.

Stephan said:

Interesting about your Soft AP mode... I switched mine to Soft AP and it shows b/g and 54Mbps... maybe something related to your laptops broadcom adapter?

Click to expand...

My gut feeling is it's not related to my client chipset. However, I do have another older laptop that I believe has an Atheros chipset; I'll try inSSIDer on it when I get home. inSSIDer is the only site survey utility I tried that showed a difference. Others (like yours) didn't see a difference, possibly because they're not looking at beacon frames in the same way. Note that yours shows only 802.11n support for two APs when they probably support b/g as well.

I don't know what's wrong that makes it show up that way, or even if anything is truly wrong, it's just a data point: something about HEX-NET's built-in soft AP is Different and Unusual as compared to regular 802.11b/g access points. I think I will ask the inSSIDer people how they determine the displayed PHY type on their support forum.

Jason

Got bored while recovering from some mild sunburn, replying to myself...

jyoung8607 said:

I don't know what's wrong that makes it show up that way, or even if anything is truly wrong, it's just a data point: something about HEX-NET's built-in soft AP is Different and Unusual as compared to regular 802.11b/g access points.

Click to expand...

I examined beacon frame captures with some better tools and found the probable answer: HEX-NET's AP beacons lack an "ERP" information element.

According to IEEE 802.11-2012, the ERP (Extended Rate PHY) IE is a mandatory part of management beacons from 802.11g access points. It controls protection mechanisms for 802.11 and 802.11b interop. At the very least, according to my reading, its absence is a standards violation. It may explain other problems as well. Nearby 802.11b clients (including those not associated with HEX-NET) will definitely cause problems since HEX-NET (as the AP) can't tell 802.11g clients to enable their protection mechanisms. Even in the absence of legacy clients, 802.11g clients may not react in a predictable way to this IE being absent.

Jason

If nothing else, I have been re-learning the gritty details of 802.11 that I forgot over the last 10 years...

HEX-NET in Soft AP mode requires clients use long slot times (in the style of 802.11b) as opposed to short slot times (in the style of 802.11g). Use of short slot times is optional, but support is mandatory and 802.11g devices should be using short unless there's a good reason not to. Switching to long slot times is part of 802.11b/g interop, but if it's doing that, it's supposed to tell the other APs around it with the ERP IE on its beacons so they can do the same. The ERP IE is entirely missing as outlined in my earlier post.

Slot times are used to manage backoff and retry during congestion. Devices using the same slot-time setup will compete for airtime equally. If there is a mismatch, the device using long slot times will be heavily penalized relative to devices using short slot times. The one client on HEX-NET will play okay with HEX-NET itself, however, if it's in a wireless-dense neighborhood with other busy 802.11g/n clients around it, I'm pretty sure they will stomp all over both HEX-NET and its client.

Soft AP very literally looks like an 802.11g RF layer being operated by an 802.11b MAC layer. I feel like something is wrong here because Microchip has lots of docs and compatibility and performance testing white-papers up, and they seem to know their business. Is there a possibility a wrong driver got installed? Otherwise, if it's going to be that kind of party, Microchip should limit Soft AP to 802.11b rates so it at least works correctly.

I can supply packet captures and steps-to-reproduce if needed. Infrastructure appears a bit healthier but we'll see. I will get into some more testing later.

Jason

Breaking this off into a separate post for clarity...

The HEX-NET wireless module bears a striking resemblance to a Microchip MRF24WG0MA(*). They make a ton of documentation available, which is nice. Looks like it handles all of the RF and almost all of the MAC layer work. It does seem to have a series of strange limitations and restrictions though.

Some people have posted here with trouble associating with APs that have mixed WPA/WPA2 turned on. A firmware update was made available in March that seems right on point. It fixes a problem associating with APs that offer mixed WPA/WPA2 when the AP's beacons exceed about 200 bytes. It states a relationship with 802.11n but I think that's mainly because beacons from 802.11n APs have to carry information elements about HT rates, WMM (support for WMM is mandatory for 802.11n), etc so they often exceed that 200 byte figure.

Jason

(*) I swear that a peek under the hood, combined with looking up the MAC OUI vendor and stumbling across a picture of the thing on Microchip's website has been the total extent of my warranty violation to date.