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Antenna installation and alignment
- Thread starter Azimuth
- Start date
Do you have a mobile phone that is capable of showing you the Cell ID?
jcheek
Expert Member
How to "prospect" for base stations
When you are initially setting up or re-aligning a 3G/LTE installation, you want to know which is the “best” base-station in your vicinity, where it is, and how to optimise your antenna system to connect to it. If you're lucky, you may not need more than the antennas provided with your modem. However, if it turns out that you need (or want!) a better antenna system, you'll want to establish if you have line-of-sight to nearby stations or not. This will help determine what type of antenna system you select and how you set it up.
In my opinion, the most effective way for you to identify your “best” nearby base stations is to actually test them, ideally before you select an antenna system. To do this, you need to find out where they are, drive to them and physically test them on the spot using a modem and laptop PC. I call this “prospecting” for base stations and it’s not hard to do.
Much has been written on the forum lately about the “Cell_ID” which some modems display on their User Interface when connected to a base station.
For a fixed wireless installation, a daily look at Cell_ID will tell you if your modem is connecting reliably to the cell you've set your antenna system up for. Also, knowing the Cell_ID of a problematic base station will allow you to report it to your Network Operator with no ambiguity.
In the initial task of setting up an antenna system, the usefulness of a Cell_ID display is in seeing whether or not you are connecting to the same base station as you did on a former occasion. For instance, if you have recently moved a directional antenna with the purpose of connecting to a different base-station, a look at the connected Cell_ID will confirm this for you.
Beyond that point, however, knowledge of the Cell_ID is of rather limited use. This is because most of us - unless we are privy to inside information - will not know which Cell_ID corresponds to which physical base station.
Some modems, like the Huawei B593-s601 LTE modem (with current firmware, “V200R001B270D00SP00C00", dated 20 Dec 2013), don't provide a display of the "Cell_ID" at all. Fortunately, this isn't a train smash, as you'll see.
Since many of us are now using the Huawei B593 LTE modem, I’ll base these instructions on it, but the principles would be the same for any similar wireless modem.
Before you start, you’ll need to do the following:
Set up your Huawei B593 LTE modem as follows:
a. Under System/Antenna Settings, set the option in the drop-down box to “Built-in” so that the B593 always uses its built-in antennas (it is usually set to “Auto”). My own experience is that the internal antennas are at least as good (if not better) than the two included flat whip antennas. They’re also less variable, ie there’s not much to set up or get right.
b. If you like, you can even remove the whip antennas completely for easier handling in the field.
c. Under “Internet”, change the “Connection Mode” from “Always On” to “Manual”.
d. Under “Network selection”, click “Manual” and become familiar with the way the B593's “Network Search” feature works. Do this by clicking “Search” and seeing what 4G networks (if any) come up in your area.
Arrange a 12-Volt DC “field power supply” for your B593:
There are two options here:
a. Obtain (or make up) a DC adapter cable that plugs into your car’s cigarette lighter and provides 12VDC on a 5.5mm/2.1mm circular plug that will plug straight into your B593's DC port. Make sure “positive” is on the centre contact of the DC plug. Get a longish cable if you can - at least 3m (preferably 5m) is good. These can be bought ready-made in some electronics shops.
b. Use a small 12VDC-to-230VAC “inverter”. These also plug into a car cigarette-lighter and have a 230VAC output that can be used to power your B593's included 12VDC/1A AC-to-DC adapter directly.
Option (a) : Automotive DC cable with 5.5x2.1mm DC plug. This one's a bit short for the job.
Option (b) : A 12VDC-to-230VAC automotive inverter. This one is 150 Watts, which is plenty (you only need about 15 Watts). Another example is shown here.
One advantage of method (b) is that it gives you a fair amount of cable slack, which is handy in the field.
Once you’re all set up, proceed as follows :
1) From your rooftop or place where your antenna will be, try to see and identify base-stations in your vicinity. Sometimes these are on masts (easy to spot), but they can also be on top of buildings (less obvious). You can also make use of any other viable source (eg friends who work for Network Operators) to get hold of this information.
2) In the case of base-stations on masts, use Google Earth to go to the place where you suspect the tower is located and look for the tell-tale “long shadow”. If conditions at the time and day on which the Google image was captured don’t show a shadow, use Google’s “time machine” (historical imagery) to find a day when shadows were more prominent. Once you have the tower’s location, you can also drop down into Streetview to confirm it. Make a list of all the potential base-stations in your vicinity, along with their locations. Usually this will be around 7 per network operator. Also, different operators’ base-stations are often on the same site or mast, which helps.
3) Physically drive to the location of each base-station, taking your B593 and laptop with you. Once at the station, look inside the enclosure and see if you can spot nameplates on the equipment containers that will confirm if your network operator does actually have equipment at that station. The nameplates for the “Big 4" (Vodacom, MTN, Cell C and Telkom/8ta) are usually pretty easy to spot.
4) Take photos of the base station and antennas, ideally from the same angle as that from which you will see it when you’re back home. This will help confirm whether the base-station(s) you see from your rooftop are in fact the same ones you visited. They can be a bit tougher to recognise from a distance.
5) Park your vehicle in a place that has good line-of-sight to the base-station antennas - ideally about 30-100m away from the station. Get your B593 and laptop ready.
6) Whilst the exact radiation pattern of the B593 isn’t really known, it would seem logical that it is mildly directional and that the “sweet spots” are along a line at right angles to the plane of the unit (this is my opinion/impression). Position your B593 such that the “plane” of the unit is at right angles to a line connecting your position to the base station antennas, plug in, switch on, and let it boot up.
Testing in progress. This particular station was a corker - almost 80Mbps.
7) For connecting your laptop to the B593, one can either use Wi-Fi or a physical ethernet cable. I prefer the latter method as it takes one variable out of the system. Whatever method you use, wait for your B593 to boot up and then connect to its ‘Web configuration page.
8) Initiate a manual network search and see what networks are available around the base station. If you've done your homework correctly, your preferred Network Operator should be one of them.
Interesting point here : I don't know who PLMN=65514 is - perhaps Neotel ?
9) Use the “Register” button to connect to the chosen network. If your SIMcard is correctly provisioned, you should see a “Registration successful” message. The unit will still show “Disconnected”.
10) Click the “Connect” button to make an actual data connection to the base station. Verify that the unit responds with a “Connected” message.
11) Go to your System / Diagnosis page and initiate a “Wireless Status” test. This only takes about 10 seconds. Take note of your actual signal parameters. If you're in the close vicinity of a base station that actually does have your Network Operator’s equipment, my experience is that the RSSI will generally be between about -55dBm and -45dBm. These indicate powerful signals which confirm you are in the right place with the right kit.
12) Open up a separate browser tab and verify that you do have an actual internet connection, eg with a simple Google search.
13) Open a separate browser tab, go to www.speedtest.net, initiate a speed test and record the results. Make a note of that station’s RSSI, RSRP, RSRQ and down- and up-link speeds.
14) Repeat this exercise for all base stations in your area. The results may surprise you. For instance, even with the best signal, certain stations may give poor speed results which might indicate that they don't have the latest equipment, aren't correctly set up, are over-subscribed or that a speed constraint exists elsewhere (eg on the backhaul).
Here are results from various stations in my area (on Telkom Mobile) :
Station / Result
A RSSI/RSRP/RSRQ=-53/-80/?; DL/UL=61.2/8.2
B RSSI/RSRP/RSRQ=-52/-81/-8; DL/UL=11.2/7.8
C RSSI/RSRP/RSRQ=-54/-81/-7; DL/UL=30.0/7.2
D RSSI/RSRP/RSRQ=-47/-73/-6; DL/UL=22.9/9.1
E RSSI/RSRP/RSRQ=-53/-79/-6; DL/UL=76.5/4.5
F RSSI/RSRP/RSRQ=-48/-74/-6; DL/UL=58.6/8.5
G RSSI/RSRP/RSRQ=-48/-75/-6; DL/UL=28.3/8.2
The results will quickly tell you which stations might be your best bet !
Once you’ve determined which stations give you the best signal and/or connection speeds, you can set about the task of selecting an antenna system to connect to it from your home location.
As with any method, there are of course some unknowns. Without full diagnostics, you can never be completely certain that you're connecting to the station you think you are. The base-station you test could be busy, performing poorly, or even completely offline at the time that you test. But the balance of probability is very much in your favour.
Good luck!
When you are initially setting up or re-aligning a 3G/LTE installation, you want to know which is the “best” base-station in your vicinity, where it is, and how to optimise your antenna system to connect to it. If you're lucky, you may not need more than the antennas provided with your modem. However, if it turns out that you need (or want!) a better antenna system, you'll want to establish if you have line-of-sight to nearby stations or not. This will help determine what type of antenna system you select and how you set it up.
In my opinion, the most effective way for you to identify your “best” nearby base stations is to actually test them, ideally before you select an antenna system. To do this, you need to find out where they are, drive to them and physically test them on the spot using a modem and laptop PC. I call this “prospecting” for base stations and it’s not hard to do.
Much has been written on the forum lately about the “Cell_ID” which some modems display on their User Interface when connected to a base station.
For a fixed wireless installation, a daily look at Cell_ID will tell you if your modem is connecting reliably to the cell you've set your antenna system up for. Also, knowing the Cell_ID of a problematic base station will allow you to report it to your Network Operator with no ambiguity.
In the initial task of setting up an antenna system, the usefulness of a Cell_ID display is in seeing whether or not you are connecting to the same base station as you did on a former occasion. For instance, if you have recently moved a directional antenna with the purpose of connecting to a different base-station, a look at the connected Cell_ID will confirm this for you.
Beyond that point, however, knowledge of the Cell_ID is of rather limited use. This is because most of us - unless we are privy to inside information - will not know which Cell_ID corresponds to which physical base station.
Some modems, like the Huawei B593-s601 LTE modem (with current firmware, “V200R001B270D00SP00C00", dated 20 Dec 2013), don't provide a display of the "Cell_ID" at all. Fortunately, this isn't a train smash, as you'll see.
Since many of us are now using the Huawei B593 LTE modem, I’ll base these instructions on it, but the principles would be the same for any similar wireless modem.
Before you start, you’ll need to do the following:
Set up your Huawei B593 LTE modem as follows:
a. Under System/Antenna Settings, set the option in the drop-down box to “Built-in” so that the B593 always uses its built-in antennas (it is usually set to “Auto”). My own experience is that the internal antennas are at least as good (if not better) than the two included flat whip antennas. They’re also less variable, ie there’s not much to set up or get right.
b. If you like, you can even remove the whip antennas completely for easier handling in the field.
c. Under “Internet”, change the “Connection Mode” from “Always On” to “Manual”.
d. Under “Network selection”, click “Manual” and become familiar with the way the B593's “Network Search” feature works. Do this by clicking “Search” and seeing what 4G networks (if any) come up in your area.
Arrange a 12-Volt DC “field power supply” for your B593:
There are two options here:
a. Obtain (or make up) a DC adapter cable that plugs into your car’s cigarette lighter and provides 12VDC on a 5.5mm/2.1mm circular plug that will plug straight into your B593's DC port. Make sure “positive” is on the centre contact of the DC plug. Get a longish cable if you can - at least 3m (preferably 5m) is good. These can be bought ready-made in some electronics shops.
b. Use a small 12VDC-to-230VAC “inverter”. These also plug into a car cigarette-lighter and have a 230VAC output that can be used to power your B593's included 12VDC/1A AC-to-DC adapter directly.
Option (a) : Automotive DC cable with 5.5x2.1mm DC plug. This one's a bit short for the job.
Option (b) : A 12VDC-to-230VAC automotive inverter. This one is 150 Watts, which is plenty (you only need about 15 Watts). Another example is shown here.
One advantage of method (b) is that it gives you a fair amount of cable slack, which is handy in the field.
Once you’re all set up, proceed as follows :
1) From your rooftop or place where your antenna will be, try to see and identify base-stations in your vicinity. Sometimes these are on masts (easy to spot), but they can also be on top of buildings (less obvious). You can also make use of any other viable source (eg friends who work for Network Operators) to get hold of this information.
2) In the case of base-stations on masts, use Google Earth to go to the place where you suspect the tower is located and look for the tell-tale “long shadow”. If conditions at the time and day on which the Google image was captured don’t show a shadow, use Google’s “time machine” (historical imagery) to find a day when shadows were more prominent. Once you have the tower’s location, you can also drop down into Streetview to confirm it. Make a list of all the potential base-stations in your vicinity, along with their locations. Usually this will be around 7 per network operator. Also, different operators’ base-stations are often on the same site or mast, which helps.
3) Physically drive to the location of each base-station, taking your B593 and laptop with you. Once at the station, look inside the enclosure and see if you can spot nameplates on the equipment containers that will confirm if your network operator does actually have equipment at that station. The nameplates for the “Big 4" (Vodacom, MTN, Cell C and Telkom/8ta) are usually pretty easy to spot.
4) Take photos of the base station and antennas, ideally from the same angle as that from which you will see it when you’re back home. This will help confirm whether the base-station(s) you see from your rooftop are in fact the same ones you visited. They can be a bit tougher to recognise from a distance.
5) Park your vehicle in a place that has good line-of-sight to the base-station antennas - ideally about 30-100m away from the station. Get your B593 and laptop ready.
6) Whilst the exact radiation pattern of the B593 isn’t really known, it would seem logical that it is mildly directional and that the “sweet spots” are along a line at right angles to the plane of the unit (this is my opinion/impression). Position your B593 such that the “plane” of the unit is at right angles to a line connecting your position to the base station antennas, plug in, switch on, and let it boot up.
Testing in progress. This particular station was a corker - almost 80Mbps.
7) For connecting your laptop to the B593, one can either use Wi-Fi or a physical ethernet cable. I prefer the latter method as it takes one variable out of the system. Whatever method you use, wait for your B593 to boot up and then connect to its ‘Web configuration page.
8) Initiate a manual network search and see what networks are available around the base station. If you've done your homework correctly, your preferred Network Operator should be one of them.
Interesting point here : I don't know who PLMN=65514 is - perhaps Neotel ?
9) Use the “Register” button to connect to the chosen network. If your SIMcard is correctly provisioned, you should see a “Registration successful” message. The unit will still show “Disconnected”.
10) Click the “Connect” button to make an actual data connection to the base station. Verify that the unit responds with a “Connected” message.
11) Go to your System / Diagnosis page and initiate a “Wireless Status” test. This only takes about 10 seconds. Take note of your actual signal parameters. If you're in the close vicinity of a base station that actually does have your Network Operator’s equipment, my experience is that the RSSI will generally be between about -55dBm and -45dBm. These indicate powerful signals which confirm you are in the right place with the right kit.
12) Open up a separate browser tab and verify that you do have an actual internet connection, eg with a simple Google search.
13) Open a separate browser tab, go to www.speedtest.net, initiate a speed test and record the results. Make a note of that station’s RSSI, RSRP, RSRQ and down- and up-link speeds.
14) Repeat this exercise for all base stations in your area. The results may surprise you. For instance, even with the best signal, certain stations may give poor speed results which might indicate that they don't have the latest equipment, aren't correctly set up, are over-subscribed or that a speed constraint exists elsewhere (eg on the backhaul).
Here are results from various stations in my area (on Telkom Mobile) :
Station / Result
A RSSI/RSRP/RSRQ=-53/-80/?; DL/UL=61.2/8.2
B RSSI/RSRP/RSRQ=-52/-81/-8; DL/UL=11.2/7.8
C RSSI/RSRP/RSRQ=-54/-81/-7; DL/UL=30.0/7.2
D RSSI/RSRP/RSRQ=-47/-73/-6; DL/UL=22.9/9.1
E RSSI/RSRP/RSRQ=-53/-79/-6; DL/UL=76.5/4.5
F RSSI/RSRP/RSRQ=-48/-74/-6; DL/UL=58.6/8.5
G RSSI/RSRP/RSRQ=-48/-75/-6; DL/UL=28.3/8.2
The results will quickly tell you which stations might be your best bet !
Once you’ve determined which stations give you the best signal and/or connection speeds, you can set about the task of selecting an antenna system to connect to it from your home location.
As with any method, there are of course some unknowns. Without full diagnostics, you can never be completely certain that you're connecting to the station you think you are. The base-station you test could be busy, performing poorly, or even completely offline at the time that you test. But the balance of probability is very much in your favour.
Good luck!
Last edited:
jcheek
Expert Member
Yeah, I do - with some persuasion, even a Blackberry can be made to show this ;-)
I may give it a go when I'm next in the area with the right SIMcard ...
That's not true. It is also quite easy to determine whether a cell ID belongs to a physical base station, simply drive around the base station and see what other cell IDs you pick up.
According to wikipedia, 65514 is Neotel:
http://en.wikipedia.org/wiki/Mobile_country_code#South_Africa_-_ZA
jcheek
Expert Member
True - the Cell_ID (or IDs, if there are multiple sectors) you pick up will likely be for the base station you're at.
Perhaps I should have said " ... most of us ... will not know for sure which Cell_ID corresponds to which physical base station."
A critical look at some of the data on OpenCellID.org reveals how hit-or-miss this process can be!
+1 for Wikipedia.
I think it's the first time I've actually come across a Neotel signal in real life
Last edited:
jcheek
Expert Member
Wasn't connecting, I was just checking out the signal landscape.
Seems some or other name-server type service also didn't/doesn't know that Neotel 4G had/has arrived!
Just out of interest, what options do you have over on the "Maintenance / Diagnosis" screen on your B880 ? On the B593 that's where the "Wireless Status" option gives you the the RSSI, RSRP and RSRQ:
View attachment 135416
PS: If it seems like I'm heckling you it's partly because we need to get your post-count up
Oops, it's 65502. Sorry!
I don't understand why we stick in this thread with B593, which doesn't even support Cell ID, so it doesn't allow proper tower identification and requires extraordinary attachments as in quoted text above. There are are other LTE modems, ordinary cell phones or LTE MiFi devices (even more convenient - with internal battery), cheaper, some with dual external antenna connectors like this one: http://mybroadband.co.za/vb/showthread.php/498822-Huawei-E3276-150Mbps-LTE-USB-Modem
Plug in to the laptop and climb out of the car, thats all. Just wonder...
Last edited:
Hi Azimuth - very good information, thank you. I'm struggling with very erratic speeds.
Download 1.94Mb/s
Upload 2.11Mb/s
Ping 351 ms
TELKOM INTERNET
Server JOHANNESBURG
8/11/2014 at 1:42 PM GMT
Download 17.38Mb/s
Upload 1.57Mb/s
Ping 30 ms
TELKOM INTERNET
Server RANDBURG
8/4/2014 at 6:21 AM GMT
Download 32.27Mb/s
Upload 4.06Mb/s
Ping 40 ms
TELKOM INTERNET
Server JOHANNESBURG
8/2/2014 at 7:44 AM GMT
Download 8.28Mb/s
Upload 3.61Mb/s
Ping 521 ms
TELKOM INTERNET
Server JOHANNESBURG
8/11/2014 at 2:50 PM GMT
I have the B593s-82 by Mobily. I bought a LTE 16SMA-ST5000 Dual antena 8DB 2xSMA 5M and an Ultra Motto-W wall mount wifi repeater (AirLink ) from OTTO Wireless Solutions. However the router does not seem to pick up the external antenna. In the table below the antenna status still just reflects "built-in".
And points 4.7, 4.8 and 4.9 have minus values. Is that OK ?
I currently use Telkom Mobile as a service provider.
I really would appreciate if you can shed some light on this.
PC Information
1.1 OS Name: Windows NT 6.1 PASS
1.2 Browser: Firefox 31.0 PASS
1.3 UI Language: English PASS
Product Information
2.1 Model: B593s-82 PASS
2.2 Software Version: V200R001C82SP024 PASS
2.3 Hardware Version: Ver.B PASS
2.4 SN: B??????????????????? PASS
2.5 IMEI: ???????????????????? PASS
2.6 WLAN MAC Address 1: AC:E8:7B:32:51:7F PASS
2.7 WLAN MAC Address 2: AC:E8:7B:32:51:80 PASS
2.8 WLAN MAC Address 3: AC:E8:7B:32:51:81 PASS
2.9 WLAN MAC Address 4: AC:E8:7B:32:51:82 PASS
2.10 LAN MAC Address: AC:E8:7B:32:51:7E PASS
2.11 Antenna Status: Build-in PASS
Modem Status
3.1 Wireless Mode: LTE/4G PASS
3.2 Dialing Mode: Always on PASS
3.3 Data Connection Status: Connected PASS
3.4 SIM card ready: YES PASS
3.5 SIM verified: YES PASS
3.6 Data APN: internet PASS
3.7 Internet MTU: 1500 PASS
3.8 Data IP Address: 1??.???.???.??? PASS
3.9 Data IP address subnet mask: 2??.???.???.??? PASS
3.10 Data IP gateway: 1??.???.???.??? PASS
3.11 DNS: 1??.??.??.1??
1??.??.??.1?? PASS
Wireless Status
4.1 PLMN: 65502 PASS
4.2 Service Status: Valid services PASS
4.3 Frequency(kHz): 23500 PASS
4.4 Bandwidth(kHz): 20000 PASS
4.5 Cell ID: 67 PASS
4.6 Signal Strength: 4 PASS
4.7 RSSI(dBm): -62 PASS
4.8 RSRP(dBm): -88 PASS
4.9 RSRQ(dB): -13 PASS
4.10 Roam: NO PASS
Download 1.94Mb/s
Upload 2.11Mb/s
Ping 351 ms
TELKOM INTERNET
Server JOHANNESBURG
8/11/2014 at 1:42 PM GMT
Download 17.38Mb/s
Upload 1.57Mb/s
Ping 30 ms
TELKOM INTERNET
Server RANDBURG
8/4/2014 at 6:21 AM GMT
Download 32.27Mb/s
Upload 4.06Mb/s
Ping 40 ms
TELKOM INTERNET
Server JOHANNESBURG
8/2/2014 at 7:44 AM GMT
Download 8.28Mb/s
Upload 3.61Mb/s
Ping 521 ms
TELKOM INTERNET
Server JOHANNESBURG
8/11/2014 at 2:50 PM GMT
I have the B593s-82 by Mobily. I bought a LTE 16SMA-ST5000 Dual antena 8DB 2xSMA 5M and an Ultra Motto-W wall mount wifi repeater (AirLink ) from OTTO Wireless Solutions. However the router does not seem to pick up the external antenna. In the table below the antenna status still just reflects "built-in".
And points 4.7, 4.8 and 4.9 have minus values. Is that OK ?
I currently use Telkom Mobile as a service provider.
I really would appreciate if you can shed some light on this.
PC Information
1.1 OS Name: Windows NT 6.1 PASS
1.2 Browser: Firefox 31.0 PASS
1.3 UI Language: English PASS
Product Information
2.1 Model: B593s-82 PASS
2.2 Software Version: V200R001C82SP024 PASS
2.3 Hardware Version: Ver.B PASS
2.4 SN: B??????????????????? PASS
2.5 IMEI: ???????????????????? PASS
2.6 WLAN MAC Address 1: AC:E8:7B:32:51:7F PASS
2.7 WLAN MAC Address 2: AC:E8:7B:32:51:80 PASS
2.8 WLAN MAC Address 3: AC:E8:7B:32:51:81 PASS
2.9 WLAN MAC Address 4: AC:E8:7B:32:51:82 PASS
2.10 LAN MAC Address: AC:E8:7B:32:51:7E PASS
2.11 Antenna Status: Build-in PASS
Modem Status
3.1 Wireless Mode: LTE/4G PASS
3.2 Dialing Mode: Always on PASS
3.3 Data Connection Status: Connected PASS
3.4 SIM card ready: YES PASS
3.5 SIM verified: YES PASS
3.6 Data APN: internet PASS
3.7 Internet MTU: 1500 PASS
3.8 Data IP Address: 1??.???.???.??? PASS
3.9 Data IP address subnet mask: 2??.???.???.??? PASS
3.10 Data IP gateway: 1??.???.???.??? PASS
3.11 DNS: 1??.??.??.1??
1??.??.??.1?? PASS
Wireless Status
4.1 PLMN: 65502 PASS
4.2 Service Status: Valid services PASS
4.3 Frequency(kHz): 23500 PASS
4.4 Bandwidth(kHz): 20000 PASS
4.5 Cell ID: 67 PASS
4.6 Signal Strength: 4 PASS
4.7 RSSI(dBm): -62 PASS
4.8 RSRP(dBm): -88 PASS
4.9 RSRQ(dB): -13 PASS
4.10 Roam: NO PASS
Switch connection to manual first. It seems Huawei routers need to be in disconnect state to accept fiddling with antenna source.
Also looks like rooter is swithing to 3G mode at times, some test show results similiar to overloaded 3G tower. You can force router to keep LTE connection. I don't have this router, but I think you will find it easy.
Negative numbers are normal (less negative is better). Your signal is very good, when you manually force LTE connection, results will be more consistent.
Good luck!
Last edited:
jcheek
Expert Member
Some analysis of actual LTE test results
We now have quite a few folks using LTE and we've accumulated several test results for users' signal parameters and achieved speeds.
I thought it would be interesting to scrape all this info into a pile, plot it on on some scatter charts and perhaps try to draw some conclusions. The question : given knowledge of RSSI, RSRP and RSRQ, can we make any useful statements or predictions about likely performance ?
If nothing else, it gives a nice overview of actual results so far.
First, some preliminaries:
Units & measurements
There are many good sources of info on deciBels, dBm, RSSI, RSRP & RSRQ.
For the sake of completeness, here's my précis version:
What do we expect to see on the scatter diagrams ?
The scatter diagrams and source data are all contained inside the PDF document that is attached at the bottom of this post. Just to keep things interesting amidst the sea of text, here's a teaser:
How to the read the scatter diagrams
Practical value ranges
Cautionary notes
Observations
Possible conclusions?
(made very cautiously, bearing all the earlier disclaimers in mind):
Many thanks to all the forum users who responded to my requests for their complete test results!
We now have quite a few folks using LTE and we've accumulated several test results for users' signal parameters and achieved speeds.
I thought it would be interesting to scrape all this info into a pile, plot it on on some scatter charts and perhaps try to draw some conclusions. The question : given knowledge of RSSI, RSRP and RSRQ, can we make any useful statements or predictions about likely performance ?
If nothing else, it gives a nice overview of actual results so far.
First, some preliminaries:
Units & measurements
There are many good sources of info on deciBels, dBm, RSSI, RSRP & RSRQ.
For the sake of completeness, here's my précis version:
- deciBels, dB and dBm : The amount of power reaching your antenna system is best measured on the logarithmic “Bel” scale, in deciBels relative to a received power of 1 milliWatt (dBm). On that scale, a level of -50dBm - which is a really strong signal - represents a received power of 10nW (10 nanoWatts). Every 3dB fall on the deciBel scale represents a halving of the signal power, and every 10dB fall means a factor 10 reduction. So, a level of -80dBm represents a power level of 10 picoWatts : 1000 times (30dB) lower than the -50dBm level.
(Incidentally, this is why the apparently small difference between antennas with gains of 8dBi and 11dBi is actually quite significant : double the signal power.)
- RSSI (Received Signal Strength Indication) is an indication of the “raw” signal power reaching your antenna system. This includes both the power in the signal you’re trying to utilise, as well as any other signals in the frequency band your receiver is tuned to. Some equipment uses an arbitrary scale to indicate RSSI, such as 0-100% or 0-255. Increasingly, however, manufacturers present RSSI in the “proper” unit - dBm as given above.
- RSRP (Reference Signal Received Power) is an indication of the power in just the relevant parts (the Reference Signals) of the signal(s) you’re receiving. As such, it should provide a better measure of the true incident power of the signal you’re trying to utilise. Like RSSI, RSRP is best presented in dBm. Logically, the RSRP can never exceed the RSSI - in practise, it's significantly lower.
- RSRQ (Reference Signal Received Quality) is derived from a quotient between RSRP and RSSI and measures the amount of “useful power” reaching your antenna, as a fraction of the total power reaching it. Higher values indicate that more of the total signal power you’re receiving is associated with the signal you’re trying to utilise. RSRQ is presented in deciBels.
- RSSI-RSRP Because of how RSSI and RSRP are defined for LTE, the difference between RSSI and RSRP values (in deciBels) has a theoretical minimum value. This article explains how this minimum difference is around 20dB, and although it probably relates primarily to FDD systems (not TDD ones), the principle of a minimum difference probably applies to TDD as well. Measurements support this.
Background - Presumably, only received signals in the same frequency band to which the receiver is tuned would increase your RSSI without producing an improvement in your own signal performance. This includes signals from adjacent cells on the same network, and other networks using the same frequency. At the moment, MTN, Vodacom & Neotel use FDD in the same LTE band (1800MHz) whereas Telkom Mobile is alone at 2300MHz with TDD. As of October 2015, CellC operates FDD LTE in the 2100MHz band, and also in the 1800MHz band in some areas.
- In the context of an LTE connection, “good performance” has a number of dimensions : stability, latency, downlink speed, uplink speed etc. For this exercise, I will judge performance purely by downlink speed, which is of course simplistic. However, a connection that can consistently achieve a high downlink speed is likely to be good in other respects too.
- For the moment, I've looked only at results achieved on Telkom Mobile LTE.
What do we expect to see on the scatter diagrams ?
- A possible correlation between RSSI and speed : the higher the RSSI, the greater the possibility of high speed (neglecting the effect of spurious signals for now).
- Perhaps a better correlation between RSRP and speed : the higher the RSRP, the greater the possibility of high connection speed.
- A possible correlation between RSRQ and speed : a larger RSRQ indicates that most of the signal power incident on your antenna system comes from the signal you’re trying to utilise, and not other irrelevant ones.
- Mathematically, the dB difference between RSSI and RSRP is somewhat analogous to the quotient between those same two quantities, ie to RSRQ. Thus we might also expect to see the same correlation between RSSI-RSRP difference and speed, as we do between RSRQ and speed.
The scatter diagrams and source data are all contained inside the PDF document that is attached at the bottom of this post. Just to keep things interesting amidst the sea of text, here's a teaser:
How to the read the scatter diagrams
- In the first chart, the RSSI (in dBm) is plotted on the left axis versus the achieved downlink speed (in Mbps) on the horizontal axis (green squares).
- In the second chart, the RSRP (also in dBm) is plotted on the left axis versus the achieved downlink speed on the horizontal axis (red squares).
- In the third chart, the difference between RSSI and RSRP (RSSI-RSRP) is plotted on the left axis, versus the achieved downlink speed on the horizontal axis (pink squares).
- In looking at all 3 graphs, things get better/faster going from left to right, and from bottom to top. Signal and speed Nirvana is in the top right corner of each graph.
Practical value ranges
- For RSSI :-85dBm (weak) to -40dBm (very strong).
- For RSRP : -114dBm (weak) to -72dBm (very strong).
- For RSRQ : -12dB (terrible) to -6dB (the best it can be for "plain" LTE)
- For RSSI-RSRP : 29 (bad) to 22 (good).
- For downlink speed : 5Mbps (poor) to 90Mbps (excellent).
- Note that 100Mbps is the theoretical maximum for Telkom’s current class of LTE equipment.
Cautionary notes
- By now I think most of us realise that having good signal conditions is a prerequisite for, but not a guarantee of, high connection speed. The type of equipment at the base station, the type of connection negotiated, the capacity of the backhaul and the number of users connected, all play a role.
- The signal conditions at the receiver could differ from one occasion to another. This is especially true when using built-in or indoor antennas; less so when using a stable, permanent external antenna system.
- Even given that your signal conditions are good, the base-station’s “capacity to perform” could differ from one occasion to one another.
- Practically, there are different ways to arrive at “good signal conditions”. If you live very close to a base-station, and the signal is good anyway, then using just your modem’s internal antennas may get you to a good operating point. Alternatively, if you live far away, you may find you need a high-gain directional external antenna system to get to the same operating point. The results presented are a mix of all situations : everything from internal antennas deployed right next to the base station; all the way up to high-gain directional antenna systems deployed further away.
Observations
- On all three charts, you can notice the gradual slope from bottom left to top right : As signal conditions improve (from bottom to top), so the achievable speed (on average) increases (from left to right).
- Downlink speeds seem to fall into at least two fairly distinct “groups”. Broadly speaking, the downlink speeds are either in the range of approx 4-40Mbps, or 50-80Mbps. There may be other sub-groupings. These groupings possibly reflect different base-station operating modes, different backhaul constraints, or different classes of LTE equipment, eg “Category 3" 100Mbps equipment versus some lower-speed class(es).
- Installations achieving speeds above 20Mbps all have RSSI ≥ -75dBm. However, having RSSI ≥ -75dBm is no guarantee of getting high speed : there are cases with high RSSI values and poor speed.
- Installations achieving speeds above 20Mbps have RSRP ≥ -100dBm. Likewise, installations achieving >60Mbps have RSRP ≥ -90dBm. But again, having RSRP above those levels is no guarantee. Likewise, there are also examples where a comparatively low RSRP (say, below -95dBm) still gets good speed > 50Mbps.
- Installations achieving speeds above 50Mbps have RSSI-RSRP ≤ 26dB.
- Looking at the table of values : Once RSSI & RSRP are above a fairly low minimum signal level, the RSRQ quickly seems to max out at -6dB. However we have seen other examples (not included in these results) where a very poor RSRQ (say, -9dB or lower) is associated with poor performance.
Possible conclusions?
(made very cautiously, bearing all the earlier disclaimers in mind):
- If your antenna and signal conditions are such that:
- Your RSSI is below -75dBm; or
- Your RSRP is below -100dBm; or
- Your RSRQ is below -8dB; or
- Your RSRP is more than 27dB below your RSSI
then ... you are probably not going to see more than about 20Mbps on LTE. - If all three parameters exceed the above criteria, then you have the possibility (not certainty) of achieving speeds anywhere up to about 80Mbps.
Many thanks to all the forum users who responded to my requests for their complete test results!
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jcheek
Expert Member
Yes, you sure are !
Some of your results look fine : Down/Up/Ping = 17.4 / 1.6 / 30 for instance.
The others with the very long ping times would seem to indicate a major "traffic jam" somewhere!.
I only know the B593s-601, but hopefully yours has a similar layout:
On the B593-s601, there is a separate configuration page where you can explicitly set the antenna usage to be either (1) Built-in (2) External or (3) Auto-detected. The setting affects both antenna ports at the same time.
On a different page, there is a "status" table that shows you what antenna settings are actually in use. On the B593-s601, the actual antenna status is reported per port, but yours may not have this. (In fact, when the B593-s601 device is set to "Auto-detect", it will often choose "Built-in" on one port and "External" for another.)
The only way to make certain of using your externals is to explicitly force the antenna settings to "External" and then verify that that setting has been effective on the status page.
Yes, the negative values are normal here.
Your RSSI (raw signal power) and RSRP (useful signal power) look OK, as does the 26db difference between them.
One thing I do notice is that your RSRQ (signal quality) looks very suspect at -13dB.
From other users' results, anything below about RSRQ=-8dB is starting to get problematic. Below -10dB is certain to give bad results. Offhand, I'm not sure what would cause your value to be so poor.
Note that I'm assuming both the B593-s601 and -s82 report this parameter in the same way and on the same scale.
I gather (also from diagnostic table snapshot) that you have forced your B593 to operate in "4G only" mode.
If so, it will not happen that your B593 will drop back into 3G mode - it is effectively operating in "4G or nothing" mode.
Assuming your B593s-82 works the same as the B593s-601, the colour of the flashing circular "Mode" light confirms the type of connection : Blue for LTE, Green for 3G, red for no connection. Check your manual and verify ?
As a diagnostic test, I would suggest trying the following :
1) Try to locate your nearest Telkom Mobile base-stations. Other forum users have been successful in asking Telkom directly. If you make your approximate address known, other forum users in your area may also be able to direct you.
2) Change your B593's antenna settings to "Built-in" and go "signal-prospecting" as I described in this post. See what sort of performance you get right at the base-station to establish a baseline to compare with.
3) Once you know what performance you can get, and which base-stations you want to connect to, position your external antennas appropriately for the chosen station.
Apart from establishing a performance baseline, an "at the station" test will also give you a much better idea of which station(s) you want to try and connect with, how to set up your external antennas, and what level of performance you might expect.
Good luck!
Edit: Subsequent to this post (March 2015), it was established that the antenna which suel09 was using, is not suitable for LTE at all. See this post for details.
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Congratulations on that post, jcheek, it is simply superb. Thanks to all for sharing their data and feedback to allow a post like this! This could easily have been a MyBB article.
Note that the B593s-82 would be comparable with the B593u-91 or B593u-12 (I think), thus the old firmware and dashboard.
Besides jcheek's advice, I'd like to offer the following:
- test your antennas on another B593, or
- test another antenna e.g. Poynting on your B593
- please post your results/speeds before and after connecting the antennas?
I'd love to know the cause of that RSRQ. Let's see what it looks like without any antennas connected. Please also let us know if you have LOS for your particular base station?
On that note, I cannot identifying if your antenna solution is directional or omni. Even more importantly, what is the frequency support? This looks like a Chang Hong product. Perhaps it's Taiwan specific? Also, they appear to use RG58 coax cable which would also be a problem.
Off topic: I'd love to have those SMA plugs on my coax cables!!
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