Basic Of Mobile Communication Question :: Try To Help :: Pls

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Hi guys

Is there any factors i have to take it into account ( interm of delay or phase shift ) if i want to bypass my signal from base station A to the base station G through ( B C D E F ), instead to pass it directly from A to G.

please help me

see the figure below

 
Last edited:

The time delay for the base band signal is the sum of the flight time of the waves through air and the time delay in the base stations / repeaters. The delay inside the base station/repeaters may be dominant (of course depening on topology of base stations / repeaters. I don't know what overall delay is accaptable for you.
 

awesome WinRFP. but how can i know the delay of the base station and repeaters? and how can i know the flight time of wave?

sorry for long question because i am in the 2nd semester.
 

Hello,

Flight time of waves is just distance/c c = 3*10^8 m/s.

Delay in repeater can only be assessed when you know what goes on inside the repeater. For example when you are discussing digital signal transmission, the error detecting/correcting decoder requires certain amounf of bits in its internal registers before it can decode the baseband data. After this, the baseband bitstream has to go to the voice decoder. These decoders also need some amount of bits before it can put out voice.

In an RF repeater, the signal is frequently down converter to an IF (intermediate frequency) for analog processing. After this, it is up converted to the new transmit frequency. the IF filters in the IF processing, will introduce singificant delay, especially when they are narrow band.

I hope this helps you to understand that without knowing the repeater/base station, you can't say nothing about the delay.

BTW: where are you located on earth?
 
Hi Wim Telkamp

thank you so much for your explanation,
my last question is how can i calculate the delay in case of RF repeaters, then, is there any threshold or acceptable delay time OR phase shift??
 

Hello,

The delay (group delay) is mostly determined by the filter with the smallest bandwidth.

For a buttworth filter with n=5 (that means it consists of 5 resonators), the delay is about:

Delay = 1.5/BW, Delay in s, BW (bandwidth) in Hz.

If you have filters with very steep skirts (that means n is higher), the delay increases. Filters with less steep skirts/slopes have less delay. From the formula you can see that center frequency has no influence on delay through the filter. So a 10 MHz wide filter at 10 GHz, has same delay as a 10 MHz wide filter at say 500 MHz center frequency.

You can add the delays for all filters that have significant delay. Mixers and transistors have negligible delay (w.r.t. the filtes).


The delay in the formula is not the delay based on the phase shift of the RF signal (between in and output), but the delay of the modulation (base band signal) if you would insert such filter into a system.
 

hello

Sorry but you did't answer my last question which is " what is the threshold of the delay, in any system such as satellite, etc..?

2- what is the highest acceptable delay?

really appreciate your HelpFul
 

What do you mean with "threshold of the delay"?

Regarding the accaptable delay, what is your application?
 

Hi

Excuse me, whet's the name of this software ? Is it free.

Sorry if i don't answer at your topic.
 

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