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Optimial 5g in an urban environment
I understand that posters here are generally looking at 5g as their only option for high speed internet in rural environments, but i face a similar challenge in London Zone 2. The best broadband connection via any OpenReach enabled provider i can buy here is 50 down / 20 up, and i refuse to sign up to Virgin Media after some truly horrific customer service experiences several years back - even they can only give me peak 50 up.

So, i'm looking at 5g options. The first challenge i have is that although Three and EE both tell me i live on the edge of the indoor/outdoor 5g coverage range, my indoor 4g/5g reception is pretty appalling. However, i can get onto the roof and generate a radical 350 down / 120 up fairly consistently. So i'm conducting an experiment to see if i can achieve a highly reliable and fast connection - good enough to host some home services with very high uptime demands - in this urban environment. if it goes well, my current "superfast" Zen connection will become the failover.

I don't like the current crop of 5g modem/router offerings, and wanted something very barebones, but in the end went for the MikroTik 5g Chateau after seeing Sean's very clear post about modifications to expose the internal connectors ports. In a bit of a rush, i've also bought the u.fl to SMA connectors and a Poynting omnidirectional 4 x 4 MIMO antenna (note this not the 2 x 2 MIMO version). This may be over-kill - we shall see, and bits can be easily swapped / returned if i need to tune the setup. What led me to post is some specific questions that came to mind about the likely best way to configure all of this considering equally dire 4g reception. In particular, is it possible to connect different combinations of the 4g/5g ports to a 4 x 4 MIMO antenna, and what should go where? Or should i have gone for separate 2 x 2 MIMOs?

My iPhone (on 3) tells me i'm generally using 5g band 78, and my 4g/LTE seems to jump between band 1 and band 20. I'll post some info about my connection stats as equipment arrives and things progress. I also have an EE sim coming to experiment with.
You can connect a 4x4 MIMO to a combination of 4G/5G ports, however, you may need to swap cables about to see which combination work best. A 4x4 MIMO antenna has two pairs of cross polarised elements, so depending how you attach the leads, you could end up with one pair connecting to 4G and the second to 5G (which would be ideal) or where an element of each pair connects to 4G and alternating elements to 5G.

As you get 5G on band n78, I suggest attaching internal ports A0 and A1 to the spare SMA ports. Leave A4+A5 as their are as these handle the upload on band n78. Once you have the antenna mounted on the roof, attach all 4 leads to the router and run 2-3 speed tests. Swap SMA ports 1<>2 and rerun the speed tests. Repeat one more time swapping SMA ports 2<>3. Use whichever combination gives the fastest results.

You'll probably not get the same speed as you got on the phone as 5G will only be running in 2x2 MIMO due to using two elements for 4G, which is necessary due to 5G NSA requiring a 4G connection for control signalling. If you need faster download speed, you can get an additional 2x2 MIMO antenna and run it to modem ports A0+A1, then connect modem ports A6+A7 to the 4x4 MIMO antenna. This would provide 4x4 MIMO on 5G (modem ports A4+A5+A6+A7) and a dedicated antenna for 4G (modem ports A0+A1). It would also require drilling two additional holes for 5th and 6th SMA connections.
Thanks Sean,

A few questions/clarifications:

When you talk about swapping SMA ports 1<>2, you simply mean swap the cables around, rather than trying A2?
I read your guide on the MikroTik, i noticed your "Config 1" used A4 + A6 (rather than A5). Should i try this and what is the rational?

Finally, how much of an influence does 4g/LTE signal play here? What is control signalling and is this merely about establishing a connection - or does the 4g/LTE speed have a direct impact on 5g speed too? I'm wondering if i can get away with devoting the 4x4 antennas to the MIMO and use the bunny ears for 4g/LTE, provided i can find a good enough spot in some corner. Obviously experimentation will resolve some of this.

A friend of mine let me borrow a Zyzel NR5101 today and in exactly the same spot my iPhone 12 gets 300/150, it was registering only 20/40 - using the 2 SMA ports which i believe are devoted to 5g with the Poynting. It didn't seem to have many configuration options! Hopefully the MikroTik will be with me in a couple of days and i'll see more impressive results.
That's correct, assuming you'll have SMA #1->A5 (prewired), #2->A0 (to install), #3->A1 (to install), #4->A4 (prewired).

I based A4/A5 on your first post where you mentioned Virgin Media could only provide 50Mbps up. 5G band n78 use ports A4 and A5 for uploading, so if you use A4+A6, it may reduce the upload speed. However, if the mast operates 4x4 MIMO, A4+A6 combined with A0+A1 would provide 4x4 MIMO on 4G, so may improve the download speed over using A4+A5 as either will provide 2x2 MIMO on the downlink for 5G.

One concern however is where you didn't get a similar speed with the Zyxel NR5101 using the Poynting antenna. That Zyxel has the same Snapdragon X55 modem as the Chateau 5G. The iPhone 12 also has the same Snapdragon X55, whereas the iPhone 13 has a newer Snapdragon X60 modem. This could mean you are on the edge of the n78 signal, which may drop below the minimum threshold along the Poynting antenna's leads. When you get the Chateau 5G, choose band 78 only in the 5G list. Next, try it on the roof with its rabbit ear antennas first just to make sure it gets similar speed to the iPhone, then swap the rabbit ears with the Poynting antenna to retest.

5G NSA uses 4G for both control signalling and carrier aggregation, so you get the combined speed of the 4G and 5G bands together, depending which combination of 4G bands the network supports aggregating with the 5G connection.
Hi Sean,

So the Chateau arrived today and i had a play. A bit too windy to get on the roof, so i was confined to the balcony. I know the general direction of one 3/EE 5g antenna, not more than 400m away as the bird flies and pointed at it vaguely. I'm a bit confused about my results.

I tested with both a 3 and an EE sim (i believe the tower i'm referencing is shared by them, at least according to cellmapper), and put both in my phone and then MikroTik, taking readings from exactly the same spot in each instance.

The image order is

iPhone 12(3)
iPhone 12 (EE)

For this experiment i used A0 + A1 + A4 + A6, though did also try with A5 sporadically. Regardless of the configuration of the antennae, i can't get my download speeds anywhere close to those on the iPhone, sometimes they are almost an order of magnitude out. I also tried adding the bunny ears to A0+A1 and only using the antenna for 5g, without any improvement.

As far as i can see, iPhone and MikroTik signal  stats are approximately equal, although i seem to have pretty dire SINR sometimes. Is there something in the configuration that can be improved? Apart from putting this about 10meteres higher, where i should have direct line of sight to the full set of 5g antennas, the only other thing i can think to add another 2x2 omni or direction antenna to the 4g ports. 

Thanks for all the advice!
Going by your MikroTik signal readings and the amount of aggregated bandwidth (both over 100MHz), the speed tests should be performing a lot higher. It's like there's something is limiting the speed to about 80Mbps based on the EE and Three speeds being similar and in both upload/download directions. 80Mbps is typically what I'd expect for a 2.4GHz Wi-Fi connection.

Just to rule out the computer (antivirus, browser, Ethernet, etc.), try a speed test from your iPhone connected to the MikroTik's 5GHz Wi-Fi connection. You can check the 5GHz Wi-Fi name in Winbox -> Wireless -> WiFi Interfaces, then check the SSID name to the right of 5GHz band column.
I was initially sceptical about this because i'd set the SSIDs to overlap and by default should have been connecting to the 5Ghz Wi-Fi by default. But it turns out you were right! I wasn't ever generating a 5GHz connection - the router was apparently detecting a radar and refusing to create it. I've never come across that before.

Once connected by directly to Ethernet, i am seeing speeds roughly equivalent to the 5G on my phone. Thanks again for the advice and nice spot.

However, i do have some new challenges. As of about 10pm last night, the EE Sim absolutely refuses to establish a 5G NSA link on the router, and can't connect to the internet on the LTE link, even with apparently decent 4G connection stats. See the attached screenshot. I've not got any bands specified at all.

I thought i might have screwed up the configuration accidentally, so reset it to defaults using the reset button, without any improvement at all. I then put it in my phone just to check - and 5G is working there on EE no issues. The 3 sim is also fine in the phone or the router, so i'm slightly baffled again.

Attached Files Image(s)
It seems to have resolved itself quite spontaneously and i'm not sure what the cause was. One thing i noted is that during this period i was only being provided with at ipv6 address, although i couldn't find where this is displayed on the router. My phone knew how to handle it, but the MikroTik router absolutely could not cope. I tried setting an APN to force ivp4 only, but at about the same time - it seems to have occurred automatically - and i was immediately able to connect to 5G masts. Maybe this was an issue at EE's end. I'm really not sure!
That's great getting the full speed. I'm not sure why it took its time reconnecting the 5G connection as signal readings were excellent in your previous screenshot and the primary EARFCN figure and physical cell ID both match.

There is a bugfix for IPv6 with LTE connections in Router OS 7.2, so worth upgrading the firmware (RouterOS, RouterBoard firmware and modem firmware) if you haven't already (steps in this post).

The 5GHz radar detection is a requirement when operating on DFS channels, although some routers ignore it or only operate on indoor frequency ranges (channels 36-52). MikroTik does a 1 minute radar scan on DFS channels below 5600MHz and a 10 minute scan with 5600MHz and higher to prevent interference with weather radar systems. It shouldn't do any radar detection on the indoor 5GHz frequencies, i.e. 5180-5260MHz (Channels 36-52).
Yep, upgrades all done when i first booted - except routerboard, which i hadn't understood and is now i also sorted. Indeed much better speeds now. How do i determine when i've saturated what the mast can provide? I'm kind of wondering if it's still worth investing in an additional 2 x 2 MIMO directional antenna now i'm clear about where the best signal is found. Would this be worth it in combination with the current 4 x 4 Omni that i'm using?
If you are still managing to get better download speed with the iPhone on the roof, it may be worth getting the additional antenna to have all 6 modem connections running to outdoor antennas. If the speeds however are consistently close to what the router achieves, then it's likely you are achieving what the backhaul capacity of the mast can handle. This of course would involve drilling two holes for additional SMA connections (i.e. two more U.fl to SMA pigtails), so you will need to decide whether to risk voiding the warranty for potentially additional speed.

For the antenna, I suggest the Poynting XPOL-2-5G as has good gain from 1.7GHz through 3.8GHz and gives two configuration options.

For attaching the additional antenna, go with either:

Option 1: Connect it to modem ports A0+A1. Connect the 4x4 Omni to ports A4-A7. This will provide optimal 4x4 MIMO on the n78 5G band.
Option 2: Connect it to modem ports A4+A6. Connect ports A0+A1+A5+A7 to the 4x4 Omni. This may provide additional download/upload speed with Three 5G where the 5G SINR was weak. It's worth trying also with EE.

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