A solution for poor LTE signal strength?

Mikrotik SXT LTE is an outdoor LTE modem and router, that may provide a far better signal and data rates for fixed installations than an indoor solution.

The best solution for a network uplink connection is fibre, but it is not always an option. Cellular data may deliver more bandwidth than ADSL connections which utilise old phone copper wires. WiFi-router-firewall-LTE combo boxes are gaining popularity for a reason. It is a unit that looks like a WiFi access point but contains a SIM card slot for uplink connection. In Finland these are common even in fixed locations like homes, small offices and rural locations because unlimited cellular data plans have been inexpensive. Too bad that many have been disappointed by the actual data rates they are getting. Concrete or brick buildings, especially with modern thermal glasses, are very good at keeping cellular signal from getting inside the building. In rural area the distance to the cell tower is often too long for good data rates. What can you do?

The most common solution is an external antenna. The problem with that solution is attenuation in the cable. As a rule of thumb the loss is 3dB per meter and an additional 3dB per connection. For a 5 meter (17 feet) antenna cable that totals for 5*3dB+2*3dB or 21dB loss. Since the internal antennas are typically 2dBi you would need to install a 23dBi external antenna just to get equal signal level. Of course you can install a 30dBi antenna for a 7dB net gain, but such high gain antennas have very narrow beams. Narrow beam requires precise alignment. If the antenna is just slightly off or moves with the wind,  you may end up with much worse signal than the internal antenna already provided.

MikroTik SXT LTE

MikroTik SXT LTE (~200€) is an outdoor antenna-LTE modem-router combo. The antenna is in the same box, so the antenna cable is just an inch long. The gain of the antenna is 9dBi (eightfold signal) but is not too difficult to align. The device is connected to the internal network by ethernet cable, that can be 100 meters long without any decrease in data rates. You could place the device on a nearby hilltop, if that’s what is obstructing your connection. The ethernet cable also supplies power, so you don’t need to worry about providing power. Just keep in mind that you need to use weatherproof ethernet cabling and protect it from surges. If the cable is longer than a stub, you need to put surge protectors at both ends.

MikroTik SXT LTE
MikroTik SXT LTE & Ubiquiti surge protector

SXT LTE can receive at 100Mbps and transmit at 50Mbps. The ethernet port is 100Mbps. There are LTE data plans with higher nominal rates, but SXT LTE cannot take advantage of them. The device comes with a 24V power supply and an ethernet adapter. For longer cable runs you should consider upgrading the voltage to 48V to minimize losses. The maximum rate is 57V.

Deployment

Under a small protective door there is an ethernet port and a place for a legacy SIM card. The door is made of hard plastic, but seems to be fairly weatherproof when closed properly. There is no seal, so putting some sealing tape over the door seams and the ethernet opening should be considered. SXT LTE comes with hardware for mast attachment, but no surge protectors.

MikroTik routers use IP address 192.168.88.1 by default. You can connect to it using a browser or MikroTik’s WinBox application. The default username is admin and password is empty. The only required setting is the PIN code for the SIM card, if it has one. The default is empty. In the browser user interface the path is: top right WebFig > top left Interfaces > select lte1 > enter PIN.

MikroTik WebFig
MikroTik WebFig

The outdoor device doesn’t contain an ethernet switch or a WiFi access point, so you need to provide those in the internal network. Usually they also provide a DHCP server that you need to switch off. A DHCP server provides IP addresses for clients, usually from subnets 192.168.0.0/24 or 192.168.1.1/24. If the clients get one of those addresses, they won’t be able to connect to the SXT LTE, because it is in a different subnet. The SXT LTE also runs a DHCP server by default providing addresses from subnet 192.168.88.0/24, but it has a two second delay. If there is some other DHCP server in the network, it will serve the clients first. That’s why you need to turn off all other DHCP servers. Typically this is the only configuration change required for the internal network.

Downsides

LXT LTE only supports LTE bands 3 ja 7 (1800MHz and 2600MHz), there is no support for GPRS or EDGE. The fourth generation LTE network is not ubiquitous, so outside of it you need to find another solution.

The cell operators don’t volunteer their tower locations or info on the frequencies in use. This makes them free to change them without notice, since the customers aren’t promised anything. Unfortunately without tower location antenna alignment becomes a manual process. SXT LTE has five LEDs to show the signal strength, so you can align it at least approximately. Fortunately the 9dBi antenni is not too directional.

Different cell operators may have very different signal strength in any given location. You should have a handful of SIM cards to try when installing. The best signal for another operator may come from a different direction, so you should re-align the antenna for each SIM card.

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5 thoughts on “A solution for poor LTE signal strength?”

  1. Hi!
    I’ve been searching some info. guidance for this antenna with little luck.
    I’m from Spain, but I think that you could help anyways.
    I live in aparted home with no access to ADSL or fiber at all, so my only options to have internet access are WiMAX, Satellite and 4G/LTE networks.
    Nowadays I have WiMAX but it’s terrible, so since I have pretty good signal of 4G/LTE in my phone, and when that happens I can surf the web and play videogames pretty well, I came with the idea to buy an LTE antenna like this.
    If I buy this antenna and I have the APN settings of an operator, can I connect to it for free?
    I ask this questions, because as I can see the microSIM slots are for “backup”, but if you cannot connect for free, then I don’t know how the operator how can charge you your data usage of their network.
    If I don’t want to setup the APN settings, can I connect a SIM card and it will be Plug&Play or almost Plug&Play?
    Maybe I did stupid questions, but I don’t want to spend ~100€ for nothing.
    Thanks!

    1. You will always need a SIM card with a data plan to connect to an operator’s network. In the new SXT LTE Kit there are two SIM card slots where the second one can be used for backup. You could use another operator’s SIM if the first one goes down.

      No, you won’t be able to connect for “free”. You need to pay to the operator to use their network. Perhaps you can get a secondary SIM card to the one in your phone? At least here in Finland that would save you some money. The secondary card will have the same phone number but of course the SXT LTE won’t ever answer your calls.

      Typically the SIM card contains all the necessary settings so you won’t have to configure anything except for the PIN code (if your SIM has it). It is virtually Plug’n’Play.

      The new SXT LTE Kit will replace the old SXT LTE. The new model has two SIM slots, two Ethernet ports and supports all possible cellular data connections. The old one only did LTE on bands 3 and 7, which are typically used in urban environment. Just make certain you get the new one and you’ll be fine.

      1. Wow! That was a fast response!
        Thank you!
        So it’s a must to have a SIM card, ok.
        I wasn’t sure that this let it you have free connection, but I asked anyways to clarify it.
        Ok, so if I buy this, and have a new number (it would be only for the SXT) I would remove the PIN using it first from my phone, so in the SXT it would be fully Plug&Play for the SIM part.
        But I have new questions.
        This device has some management utilities like QoS for example?
        Since it is made by Mikrotik and they have the RouterOS, I suspect that it will have typical routing and network management, but I want to be sure.
        If not my idea was to connect this antenna to a PC with two network interfaces and use that PC like a router, one interface connected to the SXT and the other to a switch, and then make QoS, NAT and this kind of things on that PC.
        And since the new SXT (is the only that I can find in Spain) has 2 SIMs, is the second only for backup? Or it can be used to do load balancing?
        It would be very interesting, so I could have two different data plans, one for web surfing and other typical services like FTP, IMAP and STMP, etc. and the other one for gaming.
        Thanks very very much again.

        1. Yes, SXT LTE has full RouterOS. However, you cannot access QoS on the LTE side, it is the operator’s network. You could create your own queues on the local network before the LTE to shape traffic.

          No, you don’t need any other router. SXT LTE has a firewall and can do NAT by itself.

          No, SXT LTE has only one LTE radio so it can connect to only one LTE network at a time. The other SIM is for failover only. You can’t use it while the other is in use.

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