- This topic has 14 replies, 1 voice, and was last updated 12 years, 6 months ago by
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Hi!
My question would be about GSM repeaters.
When you install GSM band selective repeaters, what about zones that are covered both by repeater and donor BTS site? For example, when you have in-building solution with GSM repeater, some of the “repeated” signal will go out of building and mix with existing signal on same channel. This is impossible to avoid, because you cannot set boundaries to signal.
So my question is: is 12dB margin enough to avoid potential problems? does receiver see both signal but consider it as multipath fading? is there any problems that I’m not aware of?
hi,
a margin of 12dB is good enough, because the donor signal is indeed considered as an interference. The delay between both signals is too long to be considered as multipath. (of course, i said that based on my theoretical knowledge. perhaps there are some repeaters that don’t face this problem because they repeat the signal very quickly).
there is something else you should consider (but i’m sure you did already) : the amount of feedback that leaks from one repeater antenna (ex: donor side) to the other repater antenna (ex: indoor coverage).
You should measure an isolation that’s higher than the repeater gain + 12dB.
regards
pixthank you for quick answer 🙂
I calculated isolation between donor and service antenna, so there should be no problem.
What would happen if those two signals are similar level. For example let’s look at the parking in front of building. Signal from repeater is very strong inside building (let’s say -60dBm), but weaken as it goes out. So signal from repeater outside the building is -85dBm. On the same spot outside building, signal from donor BTS is also -85dBm. What will happen? Theoreticaly, signal from mobile station would go to repeater, and to BTS at the same time.
If I understood you corectly, the delay in repeater is too great, so that signal should be dismissed at the BTS, because the one that goes directly is “faster”.
That sounds OK, even I had similar conclusion. But time advance is what is confusing me. Because repeater have time delay, there should be time advance that is greater than it should be without repeater. So to BTS mobile station seems further that it really is (this is my consideration, it must not be right). Should I expect problems like: mobile station is on parking outside of building, connected to BTS directly, but have time advance that is calculated when the mobile station were on the repeater?
woth5,
i don’t know what would happen in that case.
i don’t think the timing advance is a problem. on the other hand i would say that both signals are interfering with each other. Therefore the voice quality is at risk… perhaps.I could send an email to a repeater company, they would answer me 🙂 I’m waiting if anyone has field experience on the topic…? (bijoooy, maniiiiaaaa?)
I was also hoping for some field experience…but people from repeater company should also know. Whatever comes first, i’ll wait 😉
Hi Pix,
Did you get any information from repeater company?
korgi,
no… but to be frank, i wasn’t expecting an answer…. because i didn’t send my enquiry yet 🙂
thanks for the reminder,
pixHi pix,
still waiting :))
you are a patient man 🙂
would you like to send the email yourself ? (i would appreciate it !)
Dear Woth ,
yes , your Isolation value is ok ( practicably 6-10 dB is enough )i would suggest you that put 10dB coupler and connect the antenna to coupling port ( For Reducing the EIRP ) OR change the antenna location thus you can limit the signal in that particular building ……….. after these changes still your problem is existing , pl get back to me
hi all,
A RF signal repeater system is added to a wireless communications network which increases user data rates at the periphery of the cellular coverage area by boosting the downlink (base station to mobile user) signal and uplink (mobile user to base station) signal. The RF signal repeater system includes a signal tagging means that adds a unique electronic signature to the repeated signal such that position determination errors due to a non-line of sight propagation path can be corrected. The repeated signal is received and processed with a location measurement unit to determine the time of arrival and to extract the signal tag of the repeated signal. The time of arrival measurement and recovered signal tag are then processed at a mobile location center to determine the true position of the transmitter.
sreni, it’s hard to believe that a repeater would do that… and a mobile location center is not necessary to use a repeater.
And the amount of signalling that would be required to do what you are describing would be rather intense.Anyway, i’ve never heard of anything like this… are you talking about 2G repeaters ?
hi pix,
sorry for being late. my mail adress is: salihgorgun@gmail.com
This certanly is an old thread 🙂
Well, a couple years of experience and….
Base stations doesn’t have problem with the 2 components of incoming signal (first component is direct signal from mobile station to base station, and second component is signal from mobile station -> repeater -> base station). Base station is looking at these two components as multipath fading, and deal with it accordingly (a very common situation in urban enviroment, where there are two signals of relativly equal strenth from same source).
regards
Dear pix
I lost your email, can you please send your email to abdirahman[DOT]osm[AT]gmail[DOT]com.
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