My excellent LHGG is supplied with a LTE6 (CAT6) Mikrotik modem, however can a CAT12/16 be fitted to increase the DL aggregation (x3 / x5
) and if so which modems are supported?
Pretty sure DL / no of carriers that can be aggregated is independent of MIMO, although technically I’m not sure how this can be. Article here: https://commsbrief.com/what-is-the-difference-between-mimo-and-carrier-aggregation/ would suggest a MIMO 2 x 2 can still DL x5 although how when there are only 2 MIMO antenna, can the LTE modem RX and TX at multiple frequencies at the same time?
@Mikrotik - can we have a (4 x 4 or greater LHGG antenna design) with CAT 16 modem please?
Different modems support different CA combinations. And CA combinations can be different in DL and UL. So yes, CA-capable modems can Rx on multiple frequencies at the same time and some (CAT 16 do) can Tx on multiple frequencies at the same time. Simultaneous Tx and Tx over multiple frequencies is the crux of CA. MIMO capability is not directly related to CA capability, so MIMO 2x2 should be fine even for higher categories with CA.
The only thing to care is configuration of modem … it has to be configured to only Tx using ports that are actually connected to antennae, otherwise it may malfunction (or even damage itself). Ideally unconnected ports should not be used for Rx either (they will mostly contribute to interference and noise).
I just can’t see from an RF viewpoint how a modem can Tx using two frequencies simultaneously, so I wonder if ‘simultaneously’ actually means time sliced intervals (multiplexed), ie Tx at freq1, then Tx at freq2, back to 1, then 2 etc?
Good point re informing the modem of the MIMO config, ie Tx without an antenna load may indeed damage the RF amps, unless they have a protection mechanism. I wonder if this can be achieved in the Quectel EP160R i.e. inform the modem to operate at 2 x2 MIMO not 4 x 4.
Maybe I’ll email Mikrotik, see if they respond re 4 x 4 MIMO dish antenna and CAT 16. And even 5G support via a dish (for edge signals rural).
From RF point of view, CA modems will have multiple transmitters, each covering certain frequency band range. Hence set of supported CA combinations. E.g. if one radio covers both B3 and B1 … 1800 and 2100 bands … then B1+B3 CA combination is not supported. If second radio covers B8+B20+B68 (900+800+700), then modem will support e.g. B20+B3 CA or B8+B1 … but not B8+B20. And this is reason why early CA modems only supported CA for DL … they didn’t have multiple transmitters.
Mind that this is true for UL and DL but DL is slightly easier because one wide-band receiver can receive multiple carriers simultaneously quite easily.
I’d listen to mkx on the RF. While I don’t know Quectel’s logic, the CA modes available are linked to MIMO configuration (and RI)… on Sierra and Telit modems, cutting off two antenna reduce the availability of some CA modes (so imagine be same on Quectel). Outside CA, perhaps you’d get higher modulation from a CAT18 on an existing channel, but I cannot believe that be that significant, but dunno.
Another consideration is Mikrotik makes the ATL that’s comes 4x4 MIMO. The retail price of a modem and M.2 adapter may be close to/exceed the cost of ATL be another concern. CAT18 modems at retail aren’t that cheap, nor are the M.2 adapters.
This makes much sense, thanks. Then I suspect the Mikrotik LTE6 modem supplied with the LHGG has a radio sharing B1+B3 and maybe no wide-band receiver, hence it can’t B1+B3.
When you mention ‘higher modulation’, higher QAM right? I’d be interested to know how to discover what the cell offers and what’s the highest QAM these days. No point having QAM ‘infinity’ if the local cell only offers QAM256, well, for me anyway.
Basically 4x4 MIMO is going to be a 2X multiplier (assuming tower/carrier/etc offer) in performance. While whatever difference in CAT6 to CAT18 offer using same 2x2 antenna is going to be some smaller percentages (e.g. there is also FEC rate associated with the QAM, so performance is still pretty linear)
Indeed higher modulations will only bring improvement in throughput in perfect radio conditions. 1024QAM has 4-times the number of possible symbol states compared to 256QAM and that in same amplitude/phase space. So it needs 6dB higher SINR to be successfully decoded (and already 256QAM requires pretty good SINR). But it only brings 25% of improvement (10 bits per symbol compared to 8 bits per symbol). OTOH working 4x4 MIMO will bring almost double throughput in fair to good radio conditions (but not so much in great radio conditions because it’s not possible to have 4 truly independent radio paths in 3D space without making some tricks, like depending on multipath to introduce delays which are different for each radio leg).
Linear was a bad word choice. Just at same CQI, the bit/Hz doesn’t double. While 3CA combo would. Also if CAT18 reported lower CQI, the difference be even less.
I’m just of opinion that congestion is what kills you, so having more CA available allows more options to avoid. And a move to CAT18 may limit CA modes with only 2x2 MIMO. But no doubt there would likely be some theoretical improvement in swapping.
Indeed that’s the biggest issue when it comes to mobile broadband performance. Physical layer (LTE carriers) is shared medium and a very congested one (many concurrent users).
I would agree, but for the mast I connect to, if I walk towards it (and achieve additional tree clearance), BW increases significantly, so I’m confident it’s RSRP/SNR (c.-100dB and 11-18dB respectively).
The “is it worth changing” my answer likely no. Now pretty sure you’d see some improvement, but the variables/time in trying to upgrade the modem may not be worth it. I’d either keep it as is and tweak it until you optimized RSRQ (and then others) as best you can. Or upgrade to the ATL* which comes 4x4 which likely have more visible improvements than just upgrade 2x2 CAT18 alone.
Also, you might want to check cellmapper.com to see what bands your carriers offer to even know what might help. (The actual maps of coverage are more hit-or-miss, but typically carrier deploy the same bands in a region)
Well, scheduler in base station can use different algorithms and some of those can be tuned a bit. But what most operators do is to prioritize cell throuhput (which means highest average client happiness). Which means that often the client with best signal strength will get largest share of resources (can be read as: air time). So it is good to enhance your radio link as much as possible to get higher share of resources. And that’s what hapens when you move closer to cell tower.
Now, even if scheduler algorithm used is the most communistic one (round robin), having radio link as good as it gets does give advantage … because any given resource can carry different amount of user payload, the better the signal, the bigger amount of payload. Which in case of capitalistic operators (prioritizing clients with better radio link) it brings two-fold improvement (higher share of resources and better resource utilization).
My observation, quoted inside quotation, was more about when client position, relative to cell tower (including any obstacles in between), is constant … so that utilization (caused by users) will constrain achievable throughput at any given time. Similarly when moving from one cell to another (can even be on the same cell tower, but different direction) there will probably be a difference in perfromance … because some cells will serve more clients than other cells. But in all cases, having better radio link will give you more throughput. Always.
Good old Cellmapper, yes quite comfortable using this and Solwise’s elevation mapping tool also, cheers Amm0.
What’s odd is that B3 & B3 CA on my LTE6 provides less BW than a single B1 (no CA), but as mkx details above, there are a whole host of variables , and what appears the most significant is number of users per cell & signal level. Thanks mkx for sharing your knowledge, really useful to understand things a little more in depth, rather than simply ‘congestion’, scheduling algorithms make sense (‘which means highest average client happiness’ - chuckle but quite true)
Also, I have just spotted the LHGG with CAT18 (albeit only 2 x 2 MIMO) LHGGM&EG18-EA, and based on this thread it’s unlikely to dramatically increase throughput cell edge, however depending on the radio config, it may offer B1 & B3 & B3 (my cell supports this) so I’m in two minds as this would be an improvement on only B3 & B3 (current LTE6 doesn’t support B1 & B3). Of course the only real way is to bite the bullet and test I suppose!