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Occasional Contributor
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Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

I wish to get my modem to connect to 5 GHz channels in the 149-165 band. Ideally 161 or so.

No matter how hard I try, with Channel set to Auto, and width either 80 or 40 or 20 Hz, the modem repeatedly defaults to Ch 36 or 100.

Direct channel selection is not possible with this modem, other than 36/80.

In my local home environment, there are at least 2 neighbours and another with a Hidden BSSID (gurrr!) that use Ch36, which slow down internet wifi connection especially during peak periods.

How can I make (or trick) this modem into selecting channels above 100?

Why does this firmware not allow direct channel selection above Ch36, and could an update provide this if there was enough support from Optus users?

 

 

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Occasional Contributor
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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Sorry, duplicated. See previous post

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Honoured Contributor
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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Modem Firmware updates are exteremely rare at Optus. If you want better WiFi performance perhaps look into a fully featured modem?

 

Peter Gillespie

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Hi Erani - I would recommend you maintain the Default settings rather than altering them. At the risk of being incorrect, I think this is why.

 

The 5 Ghz band covers 5150-5850 Ghz and is broken up into 4 distinct classes, the lower two being assigned to early generation 5.0 Ghz legacy bands. I would expect that by selecting Channel 36/80, this will limit you to the lower legacy 5.0 Ghz band 802.11a (54 Mbps Max) which was developed pre 802.11n (2.4Ghz 600 Mbps Max). The 802.11ac is backwards compatible to these specifications to ensure if you had any legacy equipment in your network or a weak 802.11 ac signal , it could continue to work in these lower speeds - Sagemcom make these units for global market which is full of legacy equipment and this may explain why it appears in the drop down box, but I would not recommend selecting them as there is no advantage. Country specific, the very high frequencies which use Channels over 150 are generally not available for open use and may require a licence. This may change over time.

 

Another aspect of channel availability is related to bandwidth bonding to achieve higher speeds. On this generation of modem, apart from foundational technical factors, each time a 20 Mhz bandwidth is bonded to a higher level of 40 Mhz or 80 Mhz, it uses up an available channel for each additional 20 Mhz bond and keeps it for the duration of link, so less to choose from the existing pool of spare channels. The Sagemcom only shows one channel on the GUI , but I think there are actually more being used. It  will auto connect you to the most suitable or stable combination of channels at the time of transmission/reception.  

 

I only use the Sagemcom 3864V3AC for testing and is not connected to a WAN service, so have no practical experience to share with you. It defaults to Channel 149, bonded at 80 Mhz. Your Channel 100 is in the Lower Category of new generation higher speed 802.11ac 5.0Ghz, so that is where it should be happy; not sure why it sometimes links you to channel 36 - could be a temporary attempt to give you a link when other higher channel presents as a weaker link or not available for use.

 

If your concern is low link speed and somehow being directed to channel 36 often, is it feasible for you to relocate the Sagemcom away from where it is installed with a longer WAN/LAN cable so that the signal becomes stronger in the coverage area? It may not be your neighbour's A/Ps that are causing the problem; leaving your unit on Default, Auto (100) should handle that anyway.  Your device may be directed down to the lower speed 5.0 Ghz (a)  because at that time, it is a stronger signal than the higher speed 5.0 Ghz (ac). You could also test this by logging off the Wi-Fi Network, moving closer to the Sagemcom and then re-log back in.  Hope this helps. 

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Thank you for taking the time to provide such a detailed response.

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

In support of what @Mkrtich has posted and from what I understand, your best bet for channels selection are 36, 52, 100, 132 or 149. That is because these are the channels that allow/support 80 MHz channel width. Channel 161, for example, will only allow 20 MHz width; channel width can be equated to possible speed. About the only other variable that is relevant is channel (output) power: that is a function of country settings in the Sagemcom which, to me, are an unknown (and I wonder what is set in the Optus Sagemcom). So, you a 'better off' defaulting to, say, 100 than setting 161 - unless you have a reason to do so.

 

My Sagemcom started life defaulting to 149, but now defaults to 56. Have no idea why.

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Thank you for your response.

I have a legacy device (iMac 2010) that cannot connect to Channels 100-144. Consequently when the modem defaults to Ch 100, this is of no value to me other than for my other devices which have no problem connecting to channels within that range.

My workaround is to connect the Mac to the 2.4 GHz band (Auto/20). This however is not as fast as 5GHz.

If I manually select Ch36 (36/80) which the Mac can see, then I find that this can be slow with stutters at peak periods, probably because others are using this/these channels.

The modem did at one point a few months ago connect to Ch 161, and from what  I remember the connection speed was good all round. I did not know about the 20 MHz width limitation however, and am reasonably sure I had selected 80 MHz width? 

I think that I am correct in believing that channel bonding is not necessarily symmetrical around the central channel. So for example at Ch 161, channels in use can be 149-161 or 153-165? I guess that you believe this to be incorrect. 

I do know that I have seen nearby AP’s using Ch 149 and Ch 153 respectively, and I assume that I have been “bumped off” or the modem precludes Ch 161 selection (or 149-165) because of this.

 

I am sure that the Sagemcom modem has a mind of it’s own, and that the Auto channel selection algorithm is not very sophisticated.

However the modem now either defaults to Ch 36 or 100, and I don’t see any of the other channels anymore.

I guess I will have to accept that direct channel selection in the 5GHz range is limited with this modem.

It is interesting to note that a previous reply suggested that I purchase a “fully featured” modem. This is what Optus offers, and I guess that I expected better than what is probably mediocre. And I even paid $40 for the upgrade to the AC modem (Black) which supposedly is better than the standard F@ST3864v3 (White)!

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Erani - I am by no means a specialist or technically qualified expert in these matters. I do like to read about technology and formulate understandings of how it all comes together but a lot of it remains a mystery to me. A few observations and these are theoretically based rather than experienced based.

 

1. The iMac 2010 model does not support native 802.11ac, only its predecessor, 802.11a, so there is advantage in trying to configure it to connect it to it's 802.11a settings. My understanding is that the later is limited to 54 Mbps which was at one stage was a default expectation outcome for 802.11n (2.4Ghz). The 802.11a 5 Ghz was introduced by authorities as initial attempt to separate it from the then overcrowded use of 2.4 Ghz spectrum. A lot has happened to the 2.4GHz band since those days and its capabilities have surpassed the now abandoned 802.11a 5Ghz; in theory and subject to the adoption of more modern Coding Schemes, the increase in the Number of Spatial Streams and the newer Types of Modulation Schemes employed within the Modem. Unfortunately, devices have not kept up with these developments due to cost, battery power consumption issues and people keeping their devices for up to 10 years, so legacy devices have to fit into these modern Wi-Fi Networks the best way they can governed by what the device's Wi-Fi chipset can do.

 

I would expect that you will achieve a more stable result using the 2.4Ghz setting in the iMac. If you haven't already done so and if your Sagemcom Modem has Beamforming Enabled in the 5Ghz Radio pages, I suggest you Disbable the two tick boxes at the bottom of the page and then Save - this results in the 2.4 Ghz and 5 Ghz SSIDs both broadcasting, instead of a common SSID which I assume relieves the Modem from its Auto Supervision work, allowing you to lock in the iMac to the 2.4 Gz. Beamforming enablement, due to its early history of being vendor proprietary then later being industry standardised  is another victim of technology advancing faster making legacy devices not compliant and has in many situations, when Enabled, has caused poor Modem performance or sheer inablity to connect some 2.4 Ghz devices.  If speed remains an issue, you may wish to consider a pair of 240 volt AV500 Powerline Adapter, like DLink DHP-P309AV - sometimes unused new on Gumtree for around $50 or $100 new at shops. Faster ones are available but are more expensive.

 

Wi-Fi channel allocation when bonding for speed improvement by Modems is in the Mystery category for me - the technique employed may be industry or vendor specific, not sure. I have read many articles on the web which are beyond my level of understanding and find it a confusing topic. I have distilled some essence from it and come away with the impression to leave the modem decide. Buying a more expensive modem will not allow your iMac Wi-Fi to operate faster, I think that comment may be in relation to coverage area and more customised functionality. Your iMac would fly faster with a LAN connection and serve you well for many years to come - I am an Apple fan.

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Mkritch- thank you again for your reply.

Like you I am no expert and what little knowledge I have has come from quite disjointed reading. Your knowledge seems to be more cohesive than mine.

I am a little confused however with your suggestion to disable the two beamforming boxes in the modem 5GHz radio page. I apologise if I am misunderstanding the point your a making.

Currently the beam forming options are both set to disabled in the 2.4GHz range, but set at SUBFR and SUBFE respectively in the 5 GHz range. This is the default as I have not altered this arrangement.

In this setup the modem already operates in a dual band fashion, simultaneously outputting both 2.4 and 5Ghz using separate BSSID’s, and separate network names.

So the Mac is already locked in using 2.4Ghz in the Auto channel selection setting, and my other devices access the 5Ghz range either in the Auto or 36Mhz channel bands.

I have not experimented with disabling the two options in the 5GHz radio pages as well.

Yes the Mac would be better served by a direct ethernet cable connection, and that remains an option, but currently impractical due to room and device layout.

 

There is so much to this modem and it’s options and radio box selections that I do not understand. This is because there is no documentation supplied by Optus. Nothing on the web either. Sagemcom seem not to directly offer this model in their range either. This is obviously a conscious decision on the part of Optus. To achieve what end? Very frustrating!

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Re: Cannot directly select 5GHz channel operation on Sagemcom FAS3864v3AC modem

Yes, having no manual is frustrating and I am continuously learning as well. I think carriers would end up happier customers if they published some meaningful guides and applications examples for people to follow. I occasionally assist a few friends who use Optus with their Internet issues and the firmware in my test unit is at V10.33. In default mode it came up with a common SSID and only 5Ghz showing up on the Wireless Management Page. I had to get into System Admin with a LAN cable to discover wl0 (5Ghz) and wl1(2.4Ghz) settings pages and read up on the Internet that Beamforming was the culprit causing prevention of 2.4Ghz broadcasting. Your modem may have later version firmware which may have addressed this issue.

 

From my readings on the subject, Beamforming is a 5Ghz feature and for the majority of situations, when deployed successfully (a rare feat), it works as a Downlink from Router to device only. For the Uplink side to work, the device also has to support the same functionality which the majority of consumer grade devices currently don't. In the Sagemcom, the 5Ghz is provided by a special Wi-Fi Radio chipset and the 2.4 Ghz is integral to the Modem's CPU Chipset, that is why the 2.4Ghz page is greyed out.

 

Prior to the introduction of a standardised Beamforming in 802.11 ac Wave 2, it was a mishmash of proprietary arrangements whereby the Router Manufacturer could only get it to work if they also supplied their Wi-Fi Adapter for the PC or the Wi-Fi chipset supported their special add-in or extension. Two types existed, Implicit, where the Router had to pre-map all devices in the network and understand how and where to target them, causing additional processor load which slowed down its operations and then the current replacement called, Explicit, whereby the workload is shared between the Router and the Device, after handshaking, they lock into each other with a narrow Downlink beam instead of the standard spherical Omni broadcast pattern.

 

I think the two Beamforming Tick boxes when Enabled would unnecessarily add processing load to the CPU as it will be constantly testing and looking for something that is not there, especially for  devices that move within the home. That is why I think it is safe to turn them off. This is what I think these settings stand for. The 'SU' prefixes do not show up on the 10.33 screens, only the BFR and the BFE.

 

Beamforming Transmission - BFR - Router broadcasting out Downlink - Function ON - (this may also be a hangover from Implicit days ? not sure)

Beamforming Reception - BFE - Router Receiving Information from device - Explicit , where the device is actively participating

 

I also think all the other Settings in Wi-Fi are best kept at default and would not recommend experimenting with them. 

 

 

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