Connectivity – a word that is bandied about everywhere. We need to be (seemingly) constantly connected. Good for the one who can take extended breaks from it. For overlanders, bloggers or blogging overlanders, a supply of sufficient internet bandwidth is of great importance. Not to mention families who travel long distances by car and whose kids are constantly asking about the next internet connection. We show what’s important for mobile Internet and WLAN in the car.
Internet in the car? No problem! Nowadays, any smartphone or tablet with a SIM card and a data plan can be used as a WLAN hotspot with the tethering function. No installation, no additional hardware, just turn on tethering. Or quickly ordered a surf-stick and plugged it into the car’s USB charging socket. Runs. If you think about it a bit more, you might use a mobile LTE router. This is a WLAN hotspot with its own SIM card that establishes the Internet connection via LTE mobile communications and passes it on to the end devices via WLAN.
It’s that simple? Yes, you would think so. and indeed, for the occasional use, so that the kids can watch a few short youtube videos on the way or the navigation with online route calculation, this is also perfectly sufficient. But if you want more performance and reliability, you have to come up with a bit more and, above all, the right technology. Because nature has put a few physical laws in the way of unrestricted reception, and the market has, invisibly to the customer, plenty of devices that do not deliver what they promise. In addition, the user is confused with many terms and marketing bluster.
But one thing at a time. We want to bring a little clarity into the matter and take a closer look at the solutions on offer.
How do we connect to the internet on the move?
Nowadays there are three ways to connect to the internet on the road. But one variant is not discussed here, the access via satellite phones. This is possible and in some places the only option, but at reasonable cost and generally available technology only suitable for exchanging short messages. the other two are much cheaper, increasingly affordable, sometimes free, and significantly more powerful: mobile radio and wifi.
even in deserts you can still catch some mobile radio signals. Especially in countries with otherwise weak infrastructures or difficult geography, setting up wireless networks has always been the faster and cheaper option than underground cables.
Wifi means nothing more than a publicly accessible WLAN, which is also how we use the term here. WLAN, on the other hand, stands for the vehicle’s own private network in and around the vehicle.
So we have to decide whether we want to receive the internet via mobile radio, WLAN or both. If we want to use both, we need a device that can do both and ideally switch between them automatically.
The end devices
The usual end devices are smartphones, tablets and laptops. Everyone can receive WLAN signals directly, smartphones and tablets can also receive mobile radio signals in the vast majority of cases. Exception: there are apple ipads that cannot accept a SIM card. These are only WLAN-capable. Conversely, there are laptops, specially hardened models for outdoor use, which can be equipped with a SIM card and can then receive mobile radio directly.
This raises the question of why additional technology is needed at all, since the end devices themselves are apparently already sufficiently equipped? There are good reasons for this. Because the maximum transmission rate due to the mobile radio standard (GSM/UMTS/LTE G4/LTE G5), the mobile radio tariff and the generation of the device is often considerably reduced and disturbed by environmental factors.
What disturbs the maximum possible transmission rate?
The biggest interference factor is the attenuation (weakening) of the signal. This problem affects us when we use the receiving and transmitting device in the vehicle. A radio signal decreases in strength with distance from the transmitter. Even a few meters away from the transmitter, the signal is much weaker. Beyond the direct line of sight, the signal continues to weaken. If other weakening factors are added, it may eventually become too weak.
The signal is very strongly attenuated by metal. If we sit in a car or a cabin with a metal frame or even metal planking, we find ourselves in a more or less ideal Faraday cage. This has the property of protecting us from electromagnetic radiation. The car or. Metal cages are therefore ideal for significantly reducing the strength of radio waves even further. This can go as far as the complete extinction of the signal. The higher the frequency and the narrower the metal meshes through which the signal can still slip, the greater the loss.
Additional technology provides a remedy
This brings us to one of the main reasons for additional technology, at least when it comes to reception in the vehicle. the signal is weakened by any metal on the vehicle. And there is plenty of that. The car body, frame, engine, but also the numerous cable strands or heating strips in the windows contribute their share to this. By the way, thermally insulated windows are also vaporized with metal, which further optimizes the Faraday cage. here the higher the frequency, the wilder the effects.
The remedy is an external antenna, which brings us to the next, exactly opposite problem: the lack of a metallic surface. If you want to use an external antenna to avoid the attenuation, it is best to mount it on a large metal surface (see vertical antenna type). This is difficult to do on a GRP cabin and if it is done, it will be punished with poor performance. For such cases you have to use ground independent antennas.
Other reasons can be the devices themselves. Depending on their age and generation, they are equipped with only one antenna, for example. This means that you cannot exploit the full speeds offered by MIMO in either LTE mobile communications or the current WLAN standards. Outside europe, other frequencies are used in mobile radio, namely the US frequencies. If the receiving devices are not tuned to receive, they receive poorly or not at all. Devices that can handle all frequencies worldwide (Europe/US) are more expensive than the models for Europe.
MIMO changes everything
Thanks to MIMO technology, transmission rates have increased enormously in recent years and will continue to do so. But in order to really use this technology, you need the right receiver. Particularly the antenna and the router. And exactly with the antennas the wheat is separated from the chaff. It can be said that not everywhere where MIMO is on it, MIMO is in it. to understand this, we have to make a little excursion into radio technology. But don’t worry, it’s called "high frequency is a bitch", but we’ll go around the whole thing and explain it understandable.
When data is sent by means of a radio signal, a lot of transmission errors occur, especially in the mobile radio and WLAN sector. Each mobile device must therefore acknowledge the correct reception of data packets to its current transmitting station, and only then will the next packets arrive. If the receiver does not do this, because the data arrived incomplete, it will be sent again. The result is a long delay in transmission due to frequent retransmission of the same data. We perceive this as a slow connection.
This is where MIMO, or better MIMO 2×2 , comes into play. the mobile radio signal is received a second time at the receiving device via a second antenna. If a data packet arrives incomplete at one antenna, it can in many cases be supplemented with the data received on the second antenna to form a complete data packet. No new transmission is necessary, so more data can be transmitted per time.
This error correction alone means that transmission speeds are now possible in the LTE+ range that make it possible to use streaming services or transfer larger volumes of data. MIMO 2×2 is currently the only reasonable and available MIMO technology in the mobile area for vehicles, boats, etc.
Signal separation – the be-all and end-all of MIMO
for MIMO to work, the receiver must be able to clearly distinguish between the two incoming signals, because each antenna receives each signal. Either the separation is done by a time delay or the signal strength. An important role for the signal separation plays the reflection of the signals at obstacles. This is why MIMO works better in cities than in the open countryside.
With WLAN routers, where MIMO has been in use for a long time, the signal separation could be solved relatively easily, since only short distances have to be overcome. There is basically only the reflection by obstacles in the room available to provide a time offset when arriving at the receiving antennas. This offset enables the receiver module to distinguish between the two signals and then combine them into a single data stream. To create the different reflections and the offset, the two antennas are mounted a few centimeters apart on the WLAN router and receiver.
In the mobile radio sector, other distances have to be overcome, where it must still be possible to separate the signals cleanly even after several kilometers. Spatial separation of antennas is not sufficient. Another trick of signal technology is used: the polarization of the second antenna is rotated by 90 degrees.
To explain, an antenna pole that stands vertically also transmits the signal vertically and should ideally be received by a vertical antenna. A second antenna is then positioned horizontally, d.H. your signal is also radiated horizontally and is best received with a horizontal antenna. In LTE practice, the 90 degree polarization difference is achieved by tilting both antennas 45 degrees to either side, the antenna is figuratively speaking, built like a half X. In the mobile communications sector, MIMO is being used for the first time with LTE and category 3 devices.
On the receiver side
on the side of the receiving devices, depending on the device, all information is used for separation, both polarization and the time offset. In smartphones, several antennas are used for reception in order to achieve the clearest possible separation of signals in the very small space available. The latest chipsets for fifth generation cell phones 5G, have up to 16 antennas, split between LTE and WLAN MIMO.
LTE routers first test if their (external) antennas are MIMO capable. To do this, they send a short signal via one of their antennas when they are switched on. If the signal is received strong enough by the other antenna, the configuration is not MIMO capable. The router switches to TX diversity mode. Thereby it uses only one antenna, the one with the better reception. The transmission rate collapses.
If the test signal does not arrive at the other antenna or arrives weakly enough, MIMO reception is possible. the router goes into MIMO mode and can keep transmission rates high.
I have a MIMO antenna, but the performance is disappointing
Many are disappointed with their MIMO antennas. The reason is often that the antennas used are specified as MIMO antennas, but are not technically capable of actually providing MIMO. outwardly this is not even necessarily to recognize.
As described in the info box on MIMO, the receiver must be able to clearly separate the two incoming signals. for this a sufficient electrical isolation of the two antennas is necessary and the reception of the polarized signal must function. The former is the biggest challenge for the antenna manufacturer. It must ensure that antennas do not interfere with each other electrically in a small area. The second hurdle is to electrically align both antennas tilted by 45 degrees and at a 90 degree angle to each other.
If you look at a MIMO antenna, you will find two perpendicular antennas in most cases. And now comes something that we laymen may well call magic. some of these vertical antennas are also just that, vertical radiators (omni-radiators) that can receive and transmit a vertical polarized signal (0 degrees) well. With other devices, however, the antennas are also vertical, but in fact they are tilted by 45 degrees, just not spatially. They have been electrically rotated by the necessary angle. This is achieved by the material, the structure and the metallic base plate, only to see it is not.
And here lies the pitfall. Bad antennas look exactly the same as good ones, but perform less. the effect in this case is the same as described above, the router tests the antenna and decides to use TX diversity mode.
Transmission rates in mobile communications
What data rates a device can achieve depends technically on the local LTE version (release) and on the device category of the device. Here is a short overview of the releases of the 3GPP (worldwide body for the definition of mobile radio standards). From release 8 MIMO technology is used by the transmitters.
mobile phone releases
|UMTS||4||2004||384 kbit/s||128 kbit/s|
|UMTS HSPA||4||2006||14 mbit/s||5,7 mbit/s|
|UMTS HSPA+||5/6||2009||42 mbit/s||11 mbit/s|
|LTE||8||2010||100 mbit/s||50 mbit/s|
|LTE+ (advanced)||10||2014||1 gbit/s||500 mbit/s|
To achieve significant transmission rates, you need at least one LTE transmitter (release and a MIMO-capable device with the right category and the right antennas. Therefore now the overview of the categories. If not mentioned in the documentation, you can roughly determine the category by the maximum up- and download rate of your device.
|cat 3||8/9||100 mbit/s||50 mbit/s|
|cat 4||8/9||150 mbit/s||50 mbit/s|
|cat 5||8/9||300 mbit/s||75 mbit/s|
|cat 6||10||300 mbit/s||50 mbit/s|
|cat 9||11||450 mbit/s||50 mbit/s|
|cat 11||12||600 mbit/s|
|cat 12||12||600 mbit/s|
|cat 13||12||400 mbit/s|
|cat 14||12||4000 mbit/s|
|cat 15||12||800 mbit/s|
|cat 16||12||1000 mbit/s|
if you are standing somewhere where wifi access to the internet is possible, it usually makes sense to use it, as it saves data volume. Unfortunately, campsites or other places with wifi are poorly lit with the signal or you stand exactly where the signal slowly disappears. Therefore, you should also try to receive these signals.
The WLAN standards are designated 802.11 with one or two lowercase letters at the end. The slowest standard is 802.11a (54 mbit/s theoretical, 25 mbit/s practical), the fastest available is 802.11ac (6.930 mbit/s theoretical, 660 mbit/s in practice). MIMO has been used for some time in the WLAN sector, including in the two fastest WLAN standards currently available, 802.11n and 802.11ac. The more devices are connected and the higher the mobile data rate, the higher the WLAN standard should be. 802.11ac practically already allows 660 mbit/s.
WLAN and mobile radio speeds cannot simply be compared
The mobile data rate and the wifi speed cannot be compared directly with each other. So if you think the WLAN router doesn’t have to be faster than the mobile speed, you’re wrong. This is due to the way in which the devices send data in a WLAN. An old method from network technology is used here, the CSMA/CA method (carrier sense multiple access/collision avoidance). In simple terms, the device that wants to transmit checks if all other devices are silent at the moment. This includes the WLAN hotspot. When nothing is going on, it transmits itself. If data is already being sent, it waits a random amount of time and then tries again. While one device is transmitting, no other can transmit. In practice, this halves the WLAN bandwidth with only two devices (e.g., one antenna).B. WLAN hotspot and end device) and the more devices are added, the slower it becomes. For this reason, the WLAN hotspot should use the fastest possible 802.11 standards, such as 802.11n or the much faster 802.support 11ac.
Do we still need WLAN reception?
If you have read the WLAN speeds carefully, you may have noticed that LTE is the 4th generation of WLAN. And 5. the second generation can be faster than the WLAN. So why provide WLAN to the devices in and around the vehicle?? Especially since the limiting speed to the Internet is always the mobile connection. But there are still good reasons for the WLAN.
First of all, the actual speed of mobile communications depends on a number of factors, such as the environment and buildings, signal strength and distance. On the other hand, mobile radio connections are shared connections. This means that all users in the vicinity of a transmitting station share its bandwidth. Therefore, the speed can vary greatly. As described before, your devices can’t use the internet faster than the cellular connection allows, but a good LTE antenna with a WLAN router behind it makes the cellular signal more steady and secure for all devices.
Other reasons are that not every device requires a mobile communications card (SIM), that devices can communicate with each other without consuming data volume, and that some devices can only be connected via WLAN at all, such as Apple’s ipads without a SIM card.
The solutions at a glance
Simplified there are only two options you can choose from. One does without any external antennas and receives the mobile radio and WLAN signals in the vehicle directly with the terminal device. As far as the quality of the signal is concerned, it makes no difference whether you use a smartphone/tablet for tethering, a surfstick or an LTE router. All are subject to the problem of strong signal attenuation. The differences between these solutions lie more in battery consumption and convenience. A surfstick and mobile LTE routers are not designed to receive wifi signals; they are only set up to receive mobile radio data. Wifi reception must then be provided by the end devices themselves.
What should also not remain unmentioned is that the signal must always come to the antenna. In other words, you cannot receive faster or better than the signal available at your location. If you have poor or no reception in the middle of the forest or in a ravine due to a lack of sufficient signal, you can’t do better with any technology.
Inexpensive clamp and windshield antennas help?
some people might be inclined to use the comparatively cheap windshield antennas, be it glued, clamped or attached behind the windshield with suction cups, to at least improve the reception in the car. This investment can quickly end in disappointment, because the customer usually expects much more than the antennas are capable of delivering. They can even reduce transmission rates.
This is due to the fact that the end devices have supported MIMO for a while, but you can only use one channel with a disc antenna. So MIMO is not used at all. Improving signal reception is of no use here either. Even the often advertised flat panel antennas fall short of most users’ expectations. They were originally developed for car-sharing fleets. For these vehicles, solutions were sought to enable close communication that can be removed quickly and without leaving any residue, without any structural changes. Somehow they found their way into the market and are recommended there for internet reception.
another problem is that the electrical counterweight, the largest possible metal surface, is missing. there is a counterweight in the inner part of the antenna, but it is modest in area, so these antennas are not so powerful in this respect either. there are exceptions, like the panorama antennas LPBEM-7-27-2SP, it needs no electrical counterweight, but as a magnetic antenna it needs a metal surface anyway.
Solution 1: tethering – the simple cell phone or tablet hotspot
Any cell phone or tablet with a SIM card can already serve as a WLAN hotspot. In this respect, this possibility already travels with most of them. It works well outside the vehicle, but has mainly disadvantages if the Internet is to be used more often and with good performance. On the one hand, mobile tariffs for telephones are mostly mixed tariffs for telephoning and data transmission. The data volume, which can be transferred at high speed, is mostly limited. Once the volume is used up, the speed is slowed down considerably by the provider, and it is basically only suitable for push-pull messages via the familiar chat apps such as whatsapp or threema, and for smaller e-mails. Common tariffs offer up to 5 or 10 GB per month. Depending on the provider, you can expect to pay up to 50 euros per month. For unlimited surfing at high speed, it goes on for well over 50 euro. This is no bargain.
In addition, the smartphone must then remain in the vicinity of the connected devices. The battery has to perform at its maximum during use and will be drained accordingly fast.
This solution is absolutely sufficient for checking e-mails on the road, as long as you don’t often have large attachments or need to look up something on the Internet. For more, it should be a solution that outsources the receiving function from the own phone.
Solution 2: surfsticks
Of course, the mobile providers also offer pure data tariffs, which are cheaper. These SIM cards are intended for use in tablets or surfsticks. The surfsticks are available as USB plugs that are simply plugged into the laptop. So at least this laptop can already access the internet. With the right operating system, such as windows 7 or 10, the laptop can also become a hotspot for other devices. In this variant, a charging option for the laptop should be provided, which also supplies the surfstick with power. Surfsticks only receive mobile data, the devices themselves must be designed for wifi use.
Surf sticks are well suited for use outside the vehicle when you are traveling with the laptop in the countryside. They are small and, depending on the model, also support MIMO. If a wifi signal is available, the laptop can receive it directly itself.
the vodafone LTE-surfstick K5150 offers up to 150 mbit/s download and 50 mbit/s upload in 4G-LTE networks and has no simlock, so you can use it with any SIM card.
Solution 3: LTE hotspot router
WLAN hotspots intended directly for the car are plugged directly into the classic car charging adapter or a USB charging port. There are also table devices with a battery, which can be placed somewhere in the vehicle. Equipped with SIM card they are a quick and easy solution. Some providers also have a device for the OBD-II interface (z.B. Telekom carconnect) and can monitor the vehicle at the same time. If the vehicle is moved or started, the devices report this and even the position via the Internet.
We consider the netgear AC810-100EUS to be a mobile LTE router with a good range of functions. It can receive for all mobile radio frequencies worldwide (3G) and use all 4G networks in Europe. 15 devices can simultaneously use the 11 hours of battery life, standby it lasts 260 hours. The AC810-100EUS supports up to 300 mbit/s. On the WLAN side, it offers all the major standards up to 802.11ac.
For better reception, the matching external MIMO antenna with TS9 connection is available as an accessory.
Number of end devices may be limited
Another criterion with many small, handy LTE receivers is the number of end devices that are allowed to use a connection simultaneously. For surf sticks, it is usually between five and ten. Routers sometimes allow up to 20 end devices. The more are active, the slower is the connection for the single device, of course.
May it be a professional solution?
All the above solutions receive and transmit the signals in the vehicle and are affected by attenuation. If you travel a lot and depend on the Internet, you’re probably looking for a more robust, permanently installed solution that delivers maximum performance. The antenna plays an important role in the quality of the connection.
Attenuation and movement during reception, both cause the connection to become unstable and the LTE device to transmit at full power most of the time, resulting in higher power consumption. Without MIMO, the transmission error rate will increase. Certainly not a problem for the use of smartphone apps, but for more demanding applications or data transfers rather undesirable.
Solution 4: external antennas with LTE router
This brings us to the most efficient solution variant. In order to receive both the mobile radio signals and the wifi network optimally, you need a specialized, external antenna. Ideally one that supplies all receiving systems in the vehicle at the same time: mobile radio, wifi and gps. A dedicated LTE router for external antennas is then used inside the vehicle. There are also LTE routers specially designed for the automotive sector, which are particularly resistant to vibrations and are even designed as an Ethernet switch. This allows you to set up a wifi-independent, wired network in the vehicle and keep the interior low in radiation.
Therefore, an external MIMO-capable antenna is optimal. With the typical roof antennas, it should be noted that they always require as much electrically conductive sheet metal as possible around the antenna base, otherwise they do not work well. So if you want to place a roof antenna on a plastic roof, you have to use a ground-independent antenna.
What a router must offer?
There are a few useful functions you should look out for in an LTE router. Here is the LTE standard that the router supports. This should be at least G4 and category 3, better 4 or higher. It should have an auto-switching function that switches between LTE and wifi for different events and conditions:
- Weak signal from a source (wifi or LTE)
- Exhausted mobile data quota
- No network
- Network access denied
- Connection errors
The management interface should be graphical. Typically, these devices have an internal web server so that they can be managed through a browser. For paid or access-protected wifi connections, it should be possible to enter the access data into the router. It is even better if several accesses can be stored at the same time. It should at least have its own DHCP server (automatically assigns network addresses) and it should mask the IP addresses of the connected devices to the outside (NAT). This allows multiple end devices to share a protected or. Use paid wifi connection in parallel. Of course also a firewall belongs to it.
It is also helpful that the most important status information can be read via LED or display, so that you do not have to call up the management interface directly.
Good routers offer many more options. These include support for voice over the network (voip), tunneled private network connections (VPN) or cable-based network connections (LAN ethernet ports with RJ45 jack at least 100 mbit/s) to be able to use a cable instead of the WLAN. Some even offer a WAN ethernet port, to which a fixed network DSL router could be connected. As usual for routers it should be able to handle all necessary mechanisms of an IP network. This includes ipv4 and ipv6, DHCP, NAT, NTP, DHCP, DNS and sslv3.
Recommended models here would be the RUT850 or the rut9xx series from teltonika or the pepwave MAX BR1 mk2.
LP/GMM low profile antenna series from panorama antennas
General tips for external antennas
- The higher the antenna is mounted, the better
- The shorter and higher quality the connecting cables (coaxial cables), the better
- the cables should be of the same type and the same length
- the antenna is outside, is it really weatherproof? A quality feature you should pay attention to
advice saves costs, trouble and new purchase
The topic of mobile internet is a very complex one. To find the optimal equipment for your own project and vehicle, it requires some experience from practice, manufacturing and trade. We therefore recommend specialist advice from companies that have already successfully completed several vehicle projects. PUC car&phone gmbh, which provided us with professional advice in the preparation of this article, recommends the following at this point
mr. roth – sales manager
+49(0) 6109 – 7668 -310
E-mail: [email protected]
for this article we were advised by mr. horstmann, PUC car&phone gmbh, werksvertretung panorama antennas ltd.