‫Now we come to the concept of modulation with these differential encoding in DBP, ASCII.
‫And Dick UPMC schemes that we have studied before.
‫We have seen that we may yet be fears of assemble with respect to this carea cause of megacity, for
‫example, for this symbol.
‫Its phase is zero degrees with respect to this CAREA and DPH years of this symbol with respect to all
‫of megacity.
‫It is one 80 degrees.
‫Similarly, in this case, the fears of this symbol is zero degrees and the fears of this symbol is
‫90 degrees.
‫And at the receiver, we are actually measuring the fears of sambal with respect to this area.
‫And we are for this symbol.
‫We are measuring the face of this symbol with respect to this cause of megacity area.
‫Here it is, 180 degrees.
‫And here it is to 70 degrees.
‫But in the case of differential encoding, what we do is that we measure the features of the received
‫symbol with respect to the previous symbol that has been received.
‫For example, if at the receiver we receive this symbol.
‫And after that we receive this symbol.
‫Then we will we will hear the features of this symbol.
‫With respect to the previous symbol.
‫And similarly, if we receive.
‫This symbol, and then we received this symbol, we will measure the features of this symbol with respect
‫to this symbol and.
‫For example, if we receive this symbol and then December, we will measure the features of this symbol
‫with respect to the previous received symbol.
‫So we are not measuring the features of this symbol with respect to that, this area that was being
‫used at the transmitter and which is recovered at the receiver using the features log, Lou.
‫And how this differential encoding is achieved, this differential encoding is achieved by using a differential
‫encoder before the modulator at the transmitter site.
‫And at the receiver site after the demodulator, we use the differential decoder.
‫So here we are meeting, for example, in this signal and the fears of this symbol with respect to the
‫devious symbol that we have received.
‫Now, what are the advantages and the disadvantages of differential in encoding the differential in
‫chording becomes an all important because sometimes the phase locked loop, which is used at the receiver
‫in order to recover the carrier, it recovers the carrier, but it recovers the carrier with 180 degree
‫first shift.
‫So as a result, the decoding that we are doing at the receiver, it becomes in error.
‫So this problem can be solved by using the differential in chording, because in the differential in
‫cording, we are measuring the features of a symbol with respect to the previous symbol.
‫And if both symbols have a 180 degree face shift, it doesn't matter as long as the difference of features
‫between the two symbols remains the same.
‫So so this is the advantage of the differential in courting, but there is also this disadvantage of
‫the differential in recording.
‫And it did it.
‫And the disadvantage is that if there is error in assemble, it is propagated to the next sample.
‫So instead of having one symbol in error, we get two symbols in error.
‫If there is a if there is error in Lansing them.