Frankenbox

Technology
41

Absolutely.

It’s more the next level of detail that I’m struggling to understand in more detail. LTE uses OFDM which seems straightforward enough (though the detailed maths is beyond me) - the carriers are more widely spaced than DSL (15kHz vs 4 IIRC) and the symbol rate correspondingly higher (15k symbols per sec).

The available resources also say that with allowance for guard bands there are 1200 carriers in a 20Mhz band (4G defines bands from 1.4MHz to 20MHz wide).

I’m also fairly au fait with how QAM constellations work though TBH I can’t quite figure out if the later revisions of 4G go above 256 QAM, nor quite where the boundary lies between LTE and LTE-A (4G+, 4.5G or 4.9G depending on the reference).

So the bit rate for a single 20MHz channel should be 1200x15000x8 (as 256QAM is 8 bits per symbol) - which is 144Mbps - manifestly not any of the data rates that are listed.

So I was working on the assumption that ECC takes us to ~ 75 Mbps and then MMIO and carrier aggregation beef it up again - though I can’t see how you get 3Gbps (or higher) which is the top (theoretical) performance of 4G technologies.

I thought that was diversity, rather than MMIO as the latter offers a total bandwidth of No of streams x capacity of each. Theoretically anyway.

On the face of it MMIO seems straightforward - radiate two (or more) signals from two (or more) antennae to two (or more) antennae at the receiving end(s). Then separate them out again despite the fact that they are at the same frequency use the same modulation and occupy more or less the same airspace (but potentially with multiple paths between transmitter and receiver). The maths is so far above my head that it might as well be in orbit so I just accept that one works by magic.

It does beg the question though - if two (or more) people are connected to the same tower using the same band, how many of them can get full bandwidth. There’s an RF quart in a pint pot somewhere but I honestly don’t know if it’s a quart, half a gallon or a gallon in the same 20Oz container.

From the cell mapper I have this for the local tower:

image
image470×629 66.5 KB

Though I think the info for Free is wrong - from one of the “LTE stats” type apps on the phone I have seen Free using B28 and (on a different occasion) B20 and the phone claiming a 20MHz channel each time, also when it uses B28 the EARFCN is exactly the same (9335 for D/L centred on 770.5MHz) as Orange, SFR or Bouygues on the same channel. I haven’t seen a connection to Orange, SFR or Bouygues on B20.

Yes, except a different and more straightforward version of “more pipes” than MMIO - the fact that the tower supports just one 20MHz channel in each of B20 & B28 suggests that it can’t do “in band” aggregation but might be able to do “out of band” aggregation.

So the answer to “what speed can I get under ideal circumstances” seems to be, er, complex.

Thoughts in my head at the moment include an external antenna as that should optimise the signal and perhaps actually getting two SIMs (as I have spare modems) and bonding the connections either through my network in the UK or via the dedicated server that I rent, which is physically in France and has an unmetered 300Mbps allowance so plenty to bond two LTE connections.

PS apologies to anyone for who the above is acronym soup :slight_smile:

42

I used to have a tool which would model download speeds after punching in all the various system parameters, but alas, that tool belonged to Apple and got erased when I nuked my work laptop prior to handing it in when I left.

It’s worth remembering that the network might not be offering you the maximum data rate available in your location depending on what data package you’re paying for. This goes double for when your equipment isn’t a common one.

Every time it registers on the network from “cold”, Frankenmodem will be sending its IMEI and a full set of device capabilities. Both of which include values the network isn’t expecting and causing it to default to a lower capability set.

I was once despatched to Denmark to find out out why all the Apple phones on one Danish network were systematically failing a 3G > 2G in one location. Turns out that iPhones were reporting their support of the US GSM bands as well as the expected European band when the network asked it on the lead up to the handover and the ancient Danish GSM boxes didn’t support quad band measurement reports, causing the network to bin the handover.

1 Like
43

Quectel EP06-E at the moment, FWIW.

44

Frankenbox5G testing

IMG_20250403_221031387
IMG_20250403_2210313871920×1440 261 KB

1 Like
45

I like the double stacked gender changers?

46

You might, but I doubt that Trump would…

1 Like
47

One is a null modem.

Though given that there is usually a gender changer involved somewhere I am surprised Trump hasn’t banned RS232

1 Like
48

I’m not actually sure how much use Frankenbox5G will get - for starters we don’t actually have 5G in the village so I’m not necessarily expecting better performance though it does have a “better” 4G radio than the Quectel and can do 4x4 MMIO so it might be a bit faster even on just 4G. It’s more a proof of concept/“I’m going to get this working” thing at present.

For the curious (OK I realise that’s a small audience) the 5G card is a Foxconn T99W175 - these are fitted to various LTE enabled HP, Lenovo or Dell laptops - as the firmware varies a bit it is probably best to go for the Lenovo version - I had a Dell version but this either had a hardware problem and died or I killed it, not sure which as it worked for about half an hour and then stopped the machine booting because of PCIe errors.

The big advantage of these cards is they are cheap - £30-40 so losing one is no big deal.

The platform isn’t great for this setup - it’s an APU4D4 rather than the 3D4 for Frankenbox II - this is harder to get OpenWRT running for one thing as the Ethernet isn’t recognised out of the box (you can download the drivers, but if you haven’t got a network connection because you haven’t downloaded the drivers yet you are stuck in a bit of a catch-22).

It also, like the 3D4, only routes PCIe to one of the MiniPCIe sockets. 4G modems are normally USB (despite the form factor) but most 5G modems are a) PCIe and b) more commonly the M.2 format - hence the need for an adapter (again with pitfalls for the unwary because not all the adapters route the PCIe connections). With the adapter the card will not fit on the PCB (the Ethernet connectors are in the way) so I need a MiniPCIe extender as well

Also, the PCIe enabled socket is intended for a Wi-Fi card (which are PCIe based) so does not connect to the SIM sockets on the board - fortunately the MiniPCIe to M.2 adapter card has a SIM socket. However I can’t build an LTE/WiFi “hotspot” because I can’t fit both an LTE card *and* a Wi-Fi card. The final, minor, annoyance about the APU4 is that it does not fit in the case which has six pre-drilled SMA mounts.

I need to find an APU2 board as these route PCIe to two of the sockets - but as all of these are out of production I need to wait until one comes up on eBay these, like the APU3, have a slightly less capable Ethernet chipset but that’s probably not significant in practice - or I need to look an alternative platform such as the Broachlink Noah boards.

Fun putting it all together though.

49

Ah thats the deal breaker for me so I wont be investing :face_with_hand_over_mouth:

50

That’s OK I’m not looking for investors, I’ll keep the millions for myself.

Actually it would be price competitive as a 5G router which currently seem to start around £300 and go up, 4G routers are as cheap as chips though so high prices for 5G will not last.

Apart from the APU2 it looks like the Broachlink Noah 5 would do the job - it has a more powerful CPU, but just does not look as nice as the APUs which look decidedly cute in their little anodised cases.

51

Well, one popped up quite quickly for a decent price - a 2e4. At least it would have been decent but it was on ebay.de and eBay thoughtfully slapped 20% VAT on top at the checkout. Thanks, Brexit :rage:

52

Wouldn’t you have had to pay 19% German VAT in any case? Unless you are VAT registered and can offset it…

53

Not for a private sale of a used item, no.

2 Likes
54

Same with me on a pair of tyres from Italy, :pensive:
In the end the seller cancelled the sale, probably because of the paperwork involved these days.

55

In this case I’m hoping that the fact that eBay has charged me the VAT means there will be no further charges. It seems to work OK for stuff from China.

56

Indeed not had an issue from China orders at all. When I sent a pool pump from the UK back to Europe for repair the paperwork required was surprising and I still got charged some duty on a 0 value broken pump, worth something once repared for its return journey though. I now wait until I arrive in France to send things, no big paperwork, no duty or VAT.

57

If it were closer to a planned visit I would have had it posted to my French address, or even arranged pick up in person as the seller is located in Frankfurt and I’ll probably be driving through (or rather round) on the way back from Munich.

1 Like
58

Die deutsche Apu ist hier

image
image1920×1440 290 KB

Even arrived with the right USB ↔ RS232 adapter so no chains of gender changers and null modems.

1 Like
59

So, running the Lycamobile (no spare “R”) SIM in Frankenbox for a few days.

When it is good, it is very good (as they say).

image
image727×447 55 KB

Tower is 750m away: RSSI is currently -57.00 dBm, RSRQ -8.00 dB, RSRP is -87.00 dBm and SIRR is 6.6dB - all of which gobledygook means that the signal is “good” (SINR could be better).

If anyone is contemplating a 4G/5G box you can get an app such as “LTE Discovery” to get the numbers and then reference the following chart

image
image365×138 3.14 KB

RSRP and RSRQ are negative numbers so a “smaller” number is better (-50dBm is better than -80dBm for instance). SINR is positive so bigger numbers are better.

A handheld device such as a phone is likely to be a “close to worst case scenario” though. There’s very little room for the antennae and most (to pick up @corona’s query from the other day) will be 2x2 MIMO (like Frankenbox 4G - trying the 5G modem can wait until I’ve finished painting the fence).

4x4 MMIO tends to be a feature specific to more expensive phones - high end iPhones have it as do high end Samsung Galaxies, however it’s more common in 4G/5G routers.

80 down and 40 up is actually faster than my Orange VDSL :slight_smile: :slight_smile:

Typically it about 30Mbps down and 35Mbps up.

When it’s bad, however, it’s very bad - yesterday afternoon Internet dropped out completely. the phones were struggling as well, the G8+ could not get a data connection and the Edge 40 Pro had clearly flipped towers to pick up an HSPA+ (i.e 3G) connection - so I think that there was a general problem with the closest tower for some reason.

60

Now we know who’s in charge of you painting the fence :rofl: 750m from the aerial tower, oh how I remember those days. Now its SFR and not Orange or Free france my mast checking app couldnt locate the thing and zooming out lost it altogether.
Back to playing later then :slightly_smiling_face:

1 Like