To try and clarify factors that you need to consider when planning on using an external antenna for your 4G/LTE broadband connection.
With 4G (LTE) services starting to come onto the UK market a lot of users are finding that they are achieving download speeds that are lower than they were expecting to get. Often this can be due to poor reception however there are other factors that need to be understood which can affect the broadband speed.
Hopefully this short article will help explain the implications and considerations the user needs to examine before they can decide the best course of action.
Okay… first things first. What many users do not understand is that LTE is a multi-stream radio, MiMo (multiple in/multiple out) service. btw I’m going to stop using the term 4G; LTE is NOT 4G. The 4G term has been jumped on by various bodies e.g. telco/ISP/Government who don’t fully understanding the technology but 4G sounds better to the end users. I’m not going to go into it here but LTE is not 4G; Wiki has several good articles for any readers that want to read about why LTE isn’t 4G. Anyway… so LTE is multi-stream MiMo technology. This is like 11n WiFi (which is also MiMo). One of the ways that LTE gets it’s performance improvements is to use multiple radio data streams to and from the end client. Just like 11n WiFi, the more streams of data the client can take then the faster the effective broadband.
Like 11n WiFi, the terminology which denotes the number of streams is expressed as TxR where T is the number of transmit radio streams and R is the number of receive streams the connection can support. So, if a client supports 2×2 streams then it can generally support twice the upload and download speed of a 1×1 device. In the world of LTE you can have anything from 1×1 right up to 8×8 stream capability with all the possible mixes in between.
In simple terms a client device needs to have an antenna for each radio stream. For a 1×1 service then the client just needs a single antenna. For a 2×2 service the client needs two antenna, and so on. So the number of streams a connection can support depends upon the capabilities of the service providers masts and also the radio capabilities of the client device.
The majority of LTE dongles and routers currently being supplied by the providers are 1×1 devices. I suspect there are several reasons for this:
1×1 devices are cheaper (if the teloco’s giving something away then they want it to be as cheap as possible).
If the clients only have 1×1 devices then the maximum speed they can download is reduced which means the local telcos mast can service more users and the data backbone costs per user for the telco are minimized (or maybe that’s me just being cynical).
If you look around you will see various types of LTE (4G) antenna being advertised at range of different prices. One of the differences between these antenna is the number of antenna connections they have. Typically you will see antenna with single connections (so this is for 1×1 client devices) and antenna with dual connections (so this is for 2×2 client devices and also for 2×1 or 1×2 devices). As a general rule dual antenna cost a lot more than single antenna.
If your client device (dongle, router, whatever) only has a single antenna connector then there’s just no point in getting an LTE antenna with dual connections; you’re just wasting your money. On the other hand if you do have a dual connection device then you must use either two single connection antenna or one dual connection antenna. If you don’t then you will limit your potential data throughput (of course I’m assuming that the mast/service from your telco/ISP actually supports multi-stream).
So, if we look at the Solwise range of LTE antenna we have the Poynting A0121, as a 1×1 omni antenna:
and we also have the Poynting XPOL-A0001 which is an omni 2×2 antenna:
In some countries there is just a single frequency band used for their 4G service. The advantage of a single band is it makes the client devices cheaper and it also simplifies the antenna. It’s much easier to make an antenna to cover a single frequency range, e.g. you might just have to cover the 850MHz band, than it is to have to cover three different bands as disparate frequencies. The UK is probably the worst with LTE services spread across three widely different bands. i.e. 791-862MHz, 1710-1880MHz, and 2570-2620MHz. I suspect there are several reasons for this:
The UK didn’t have a wide enough frequency band free to allocate as a single range
The more frequency space available then the more money Ofcom can make in flogging the licenses to the telcos (again, maybe that’s be being a cynical git!).
In the Ofcom LTE auctions in early 2013 the following allocations were awarded:
Actually it’s even more complicated because some providers have more than one licensed band e.g. Vodafone has frequency allocation in both the 800MHz band and also the 2.6GHz band, and the band used varies across the country and signal mast! Generally, because the lower frequency bands give longer transmission range than the higher frequencies, then the lower bands are used in more rural areas where a mast needs to cover a geographically larger area. Conversely the higher band would be used in more built up areas like towns or cities. However this isn’t a definite. I suppose there’s no reason why a provider might not decide to use a 2.6GHz service in a rural area – it’s not fixed in stone.
The implications for the end user are you need to ensure your antenna suits the providers service. So, if you get an antenna suitable for EE on their 800MHz band and then change to a service that uses 2.6GHz then the antenna may or may not be suitable; it just depends if you were sensible in the first place and picked an antenna that can cover 800MHz and also 2.6GHz. All of the LTE antenna from Solwise clearly state the frequency bands they support. In fact we’ve made a conscious decision to only stock LTE antenna that are suitable to all three UK LTE bands so you don’t have to worry about choosing which band antenna for which supplier.
From the Ofcom table above you can see that spectrum allocated to the providers was split into individual sub bands. e.g. EE were allocated spectrum of 2x5MHz in the 800MHz band. So EE could use this as a 2×2 service with 5MHz per stream or as two 1×1 services. According to the specs for e-UTRA (this is the air interface for LTE) each 5MHz band can cope with up to 200 users. As such, in areas of high user density, you might find that the provider prefers to deliver it as two 1×1 services in order to maximize the number of users.
So let’s look at the download rates specced for LTE: A mythical link using 4×4 with 20MHz wide streams is supposed to give 300Mbps and a single 20MHz wide stream (or, presumably, two 10meg streams running as a 2×2 service) works out at 75Mbps. Scale that down to a 5MHz stream as you arrive at about 18Mbps. Note these are the transport data rates; the actual download throughput performance of the user equipment will depend upon the signal conditions, capabilities of the providers connection etc. Remember as well these data rates are shared between all the users. Get 100 users connected to the mast and that 18Mbps ain’t going to go very far! Of course, since 99.99% of users are only going to be using their connection for simple things like checking their online Facebook postings or maybe watching incredibly poor quality (low res) videos on their 2inch phone screen, then most people won’t even know!
Okay… so the conclusion is that 4G (LTE) might be considered as just a load of ISP hype? Me being cynical again!
Omni or Directional?
It doesn’t matter if its WiFi or 3G or LTE, most users think just get the highest gain antenna I can find and, invariably, this means a directional antenna. However in the majority of cases a directional antenna is a bad choice and it’ll often just make things worse. The problem is radio waves, as a rule, don’t go through solid objects. If there’s something in the way then the signal gets from mast to you by a process of reflecting and scattering from neighbouring objects. In practice this means that the signal could be arriving at your device from a multitude of different directions. For that reason a high gain directional antenna, which has a very limited angle of coverage, will frequently make things worse. Unless you have perfect line of sight between the mast and where you are going to mount the antenna then a directional antenna should be avoided. Much better to go for an omni antenna; lower gain but at least it should pick up a signal. Though, to be honest, don’t get too fixated on the gain of the antenna. The antenna in a typical data dongle is less than zero; a LOT less than zero. So even a low gain external omni with 2 or 3 dBi is still several times higher than the antenna in your dongle. The other issue is antenna location. The fact that the external antenna is placed outside (and hopefully high up) is a significant factor in improving the signal.
Single or Dual (or more)
If your dongle or router only has a single antenna connector then go for an external antenna with single connector. If you have a dual stream dongle or router then you need an antenna with two connectors or use two single connector antenna. Note, however, even if you have a dongle and antenna setup that can support a 2×2 service, if the service coming out from your providers mast doesn’t send out 2×2 then you won’t see any different than if you were running a 1×1 set-up.
As you can see from the Ofcom table previously shown, make sure your antenna setup suits the frequency range of the service coming from your local mast. If you have antenna that only supports 800MHz range but your provider uses a 2.6GHz service then your 800MHz ain’t going to work!
Unless you don’t want to run the risk of having to shin up onto your roof to change the antenna if (when) you change service then it’s best to get antenna which cover all three UK LTE bands. So that’s 800MHz, 1800MHz and 2600MHz. Our antenna clearly specify their operating frequencies and, as I’ve said before, we try to only offer LTE antenna that support all three bands; though you do pay a little more for an antenna with this flexibility.
Omni or directional
My advice is go for an omni. We get a lot of directional antenna back from customers but very few omni types. The reason for this is the customer has just jumped on the antenna which offers the biggest gain for your buck and this invariably means a directional antenna. However most people do NOT have line of sight to the mast so an omni is the way to go.
Mount the antenna where it has the best line of sight to the mast. Even if it doesn’t have true line of site (in a built up area it can often be impossible to see the signal mast) get it as high as possible and don’t position it so it has to go through a thick wall or metal building located 2 feet away! As an example, if, at our office, we try an outdoor antenna at the front of our building (which is one of those horrible metal boxes you see on industrial estates) then we get a rubbish signal even using an omni antenna. However we try the same antenna at the rear of the building and get almost full signal. The reason is the signal mast is at the back of the building (though still not in true line of sight). Using the antenna at the front means the radio signals have to try and blast a hole through the metal building and that’s just not possible.
Might still be crap
Even if you get a perfect signal then, depending upon the capabilities of your provider (e.g. their frequency allocation), the service they can offer from your local mast, how good your dongle or router is, and how many users are connected to the service in your area, it might still give a rubbish download. However, if it’s just for doing a Facebook post then you probably won’t ever notice!