If my data has long chain of 1's or 0's. Can the data be modulated and transmitted as it is. Will this have any effect of the receiver adc as this may increase dc value of the signal or any other block in the receiver chain? should the data be scrambled?
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A dominant concern with long runs of ones or zeros is the ability of the receiver to establish symbol timing. The receiver clock is independent from the transmitter clock, so without transitions in the data the receiver will not be able to determine the clock used in the transmitter for each symbol, and will ultimately drift off. Whitening the data has other benefits for equalization and overall efficiency.
answered Jul 10, 2020 at 11:48
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$\begingroup$ Thanks . I agree with you. but as it increases DC value does it effect ADC output if i am sending a zero IF signal to ADC? $\endgroup$– SteveCommented Jul 20, 2020 at 12:05
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$\begingroup$ In practical realizations there will always be DC offsets due to any imbalances in the receiver. Usually DC is ignored for this reason as there is no easy way to distinguish it (This is one reason why the DC bin is nulled in OFDM receivers). The answer to your question is yes the data should be scrambled. $\endgroup$ Commented Jul 20, 2020 at 12:18
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$\begingroup$ @ Dan sorry to bother u again . U mean to say the reason it should be scrambled is for timing related issued but not due to dc offset on adc? Thanks again $\endgroup$– SteveCommented Jul 20, 2020 at 12:39
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$\begingroup$ @Steve Both reasons. The ADC will have DC offset with or without your data and often that will be AC coupled to the receiver. Long runs will make timing acquisition difficult. $\endgroup$ Commented Jul 20, 2020 at 12:41
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$\begingroup$ @ so irrespective of the type of the data the dc offset is present in ADC. so even the scrambled data will have the dc offset? so scrambling might not help here? probably i should take into consideration in digital domain. what i mean is does the continuous o's or 1's and random data with behave the same way with respect to adc? i.e. no drop in signal after adc if continuous 0's or 1's are present? $\endgroup$– SteveCommented Jul 20, 2020 at 13:04